Content uploaded by Diane Maher
Author content
All content in this area was uploaded by Diane Maher on Jan 14, 2015
Content may be subject to copyright.
Available via license: CC BY 2.0
Content may be subject to copyright.
R E V I E W Open Access
Current status and implications of microRNAs in
ovarian cancer diagnosis and therapy
Mohd Saif Zaman
1
, Diane M Maher
1
, Sheema Khan
1
, Meena Jaggi
1,2,3
and Subhash C Chauhan
1,2,3*
Abstract
Ovarian cancer is the fifth most common cancer among women and causes more deaths than any other type of
female reproductive cancer. Currently, treatment of ovarian cancer is based on the combination of surgery and
chemotherapy. While recurrent ovarian cancer responds to additional chemotherapy treatments, the
progression-free interval becomes shorter after each cycle, as chemo-resistance increases until the disease becomes
incurable. There is, therefore, a strong need for prognostic and predictive markers to help optimize and personalize
treatment in order to improve the outcome of ovarian cancer. An increasing number of studies indicate an
essential role for microRNAs in ovarian cancer progression and chemo-resistance. MicroRNAs (miRNAs) are small
endogenous non-coding RNAs (~22bp) which are frequently dysregulated in cancer. Typically, miRNAs are involved
in crucial biological processes, including development, differentiation, apoptosis and proliferation. Two families of
miRNAs, miR-200 and let-7, are frequently dysregulated in ovarian cancer and have been associated with poor
prognosis. Both have been implicated in the regulation of epithelial-to-mesenchymal transition, a cellular transition
associated with tumor aggressiveness, tumor invasion and chemo-resistance. Moreover, miRNAs also have possible
implications for improving cancer diagnosis; for example miR-200 family, let-7 family, miR-21 and miR-214 may be
useful in diagnostic tests to help detect ovarian cancer at an early stage. Additionally, the use of multiple target
O-modified antagomirs (MTG-AMO) to inhibit oncogenic miRNAs and miRNA replacement therapy for tumor
suppressor miRNAs are essential tools for miRNA based cancer therapeutics. In this review we describe the current
status of the role miRNAs play in ovarian cancer and focus on the possibilities of microRNA-based therapies and the
use of microRNAs as diagnostic tools.
Keywords: Ovarian cancer, miRNAs, Chemoresistance, Diagnosis, Prognosis, Therapy, miR-200, Let-7
Introduction
Epithelial ovarian cancer (referred to as ovarian cancer
in this review) is the fifth most common cancer among
women and causes more deaths than any other type of
female reproductive cancer [1]. Signs and symptoms of
ovarian cancer are frequently absent or ambiguous early
on and due to a lack of early detection strategies most
(>60%) patients are diagnosed with advanced-stage dis-
ease. The five year survival rate is less than 30% for these
advanced-stage patients and, despite advances in chemo-
therapy, survival rates have only modestly improved over
the past 40 years [1-3]. Pathologically, ovarian cancer is
a heterogeneous disease comprised of serous, mucinous,
clear cell, and endometrioid subtypes. Serous tumors are
the most common subtype. Each subtype is associated
with diverse genetic risk factors and molecular events
during oncogenesis and is characterized by distinct
mRNA expression profiles. It has been observed that
subtypes respond differently to chemotherapy. The re-
sponse rate of clear cell carcinomas (15%) is very low,
whereas the response rate for high-grade serous is 80%,
resulting in a lower 5-year survival for clear cell com-
pared with high-grade serous carcinoma in patients with
advanced stage tumors (20% versus 30%) [4,5].
The standard treatment for advanced ovarian cancer is
surgical tumor debulking (removal of all tumor and me-
tastasis that can be macroscopically detected in the en-
tire abdomen region), followed by platinum-based
* Correspondence: subhash.chauhan@sanfordhealth.org
1
Cancer Biology Research Center, Sanford Research/USD, 2301 East 60th
Street North, Sioux Falls SD 57104, USA
2
Department of Obstetrics and Gynecology, Sanford School of Medicine, The
University of South Dakota, 2301 East 60th Street North, Sioux Falls SD 57105,
USA
Full list of author information is available at the end of the article
© 2012 Zaman et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Zaman et al. Journal of Ovarian Research 2012, 5:44
http://www.ovarianresearch.com/content/5/1/44
chemotherapy [6]. Neoadjuvant therapy, the use of
chemotherapy or radiation prior to surgery, may be an
option for patients with stage IIIC or IV ovarian cancer
which typically presents with a large tumor burden and
extensive metastases. For these patients optimal debulk-
ing may be difficult to achieve, making neoadjuvant ther-
apy an important option [7]; however, there is currently
an ongoing debate to clearly identify which patients
would benefit from neoadjuvant therapy [8,9].
Chemotherapy in ovarian cancer includes platinum-
based drugs, cisplatin or carboplatin coupled with pacli-
taxel. After first-line treatment with carboplatin and
paclitaxel, most patients eventually relapse with a me-
dian progression-free survival of 18 months. Recurrent
ovarian cancer initially responds to additional chemo-
therapy; however, the progression-free interval becomes
shorter after each cycle as chemo-resistance increases
until the disease becomes incurable [10]. A number of
molecular mechanisms have been characterized to ex-
plain the development of resistance to chemotherapy,
such as increased DNA repair activity and defective
DNA damage response [11], increased anti-apoptotic
regulator activity [12,13], growth factor receptor deregu-
lation [14] [15] and post-translational modification or
aberrant expression of β-tubulin and other microtubule
regulatory proteins [16].
The recently discovered microRNAs (miRNAs) consti-
tute a novel regulatory layer of gene expression and have
been implicated in the etiology of various kinds of
human cancers. miRNAs are small (~22bp) endogenous
non-coding RNAs and are frequently dysregulated in
cancer. Their role is to modulate gene expression mainly
by base-pairing to the 3’-UTR (untranslated region) of
the target mRNA, eventually causing either translational
repression, mRNA cleavage, or destabilization [17]. In
ovarian carcinoma the expression of various miRNAs
has been found to be dysregulated [18]. Recent reports
support a role for miRNAs in the initiation and progres-
sion of ovarian carcinoma [19-21] by promoting the ex-
pression of proto-oncogenes or by inhibiting the
expression of tumor suppressor genes. In this review we
focus on the current status of the role miRNAs play in
Figure 1 Oncogenic and tumor suppressor miRNAs in ovarian carcinoma. Based on their function miRNAs can be used for diagnostics and
therapeutics. Certain miRNAs such as miR-200 family, let-7 family, miR-21, miR-214 and miR-100 have strong diagnostic/prognostic potential in
ovarian cancer. Use of antagonists for oncogenic microRNAs and microRNA replacement therapy for tumor suppressor miRNAs are important
tools in miRNA based cancer treatment. EMT-Epithelial to Mesenchymal Transition; NM-Nuclear membrane; PM-Plasma membrane.
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 2 of 11
http://www.ovarianresearch.com/content/5/1/44
ovarian cancer (Figure-1 and Table-1). We also describe
their diagnostic / prognostic and therapeutic potential.
miRNAs
miRNAs were first discovered in 1993 by Lee, Feinbaum
and Ambros in the nematode C. elegans [22] and are
now known to be present and highly conserved among a
wide range of species [23]. Mature miRNAs are derived
from precursors called pri-miRNAs, composed of hun-
dreds or thousands of nucleotides [17,24,25]. miRNAs
precursor sequences are located in different parts of nu-
clear DNA and may constitute mono- or policistrone
transcriptional units. Pri-miRNAs are transcribed mainly
by polymerase RNA II. Subsequently, they are cleaved by
the endonuclease Drosha and cofactor DGCR8 into a
structure known as precursor miRNA or pre-miRNA.
Pre-miRNAs, ~60 nucleotide stem-loop molecules, are
transported from the nucleus to the cytoplasm by Expor-
tin 5 and protein Ran-GTP and further processed by the
Dicer enzyme into a ~22 nucleotide double-stranded
microRNA [26]. The double-stranded miRNA assembles
into a ribonucleoprotein complex which is known as the
RNA induced silencing complex (RISC) [27]. The RISC
induces unwinding of the double-stranded molecule into
single stranded miRNA, concomitantly degrading the
complementary strand. In animals the miRNA–RISC
binds to 3’untranslated region (3’UTR) of mRNA, does
not require perfect complementarity, and induces inhib-
ition of translation at the initiation or elongation phase
[27]. The mode of inhibition may depend, in part, on the
level of complementarity of the miRNAs where perfect
or near perfect complementarity favors degradation. The
mechanism of 3’UTR mRNA target regulation is com-
plex. Nevertheless, recent studies suggest that it is a two
step process in which inhibition of translation is done
first, followed by mRNA decay due to deadenylation of
the mRNA [28]. The seed sequence is essential for the
binding of the miRNA to the mRNA. The seed sequence
is a conserved heptamerical sequence which is mostly
situated at positions 2–7 from the 5’end of the miRNA,
although other factors are also important [17,29]. Gu
et. al. [30] have suggested that miRNA target sites can
also be found in the 5’UTR or even in the coding re-
gion of the mRNA. By binding to 5’UTR sequences
miRNAs can also activate translation. Thus, inhibition
of posttranscriptional mRNA processing is not the only
way of regulating miRNA-dependent gene expression
[31]. Moreover, as miRNAs do not require perfect com-
plementarity for functional interactions with mRNA tar-
gets, a single miRNA can regulate multiple targets and
conversely, multiple miRNAs are known to regulate in-
dividual mRNAs [32].
miRNAs in cancer
miRNAs are involved in crucial biological processes, in-
cluding development, differentiation, apoptosis and pro-
liferation [33]. This is done through imperfect pairing
with target messenger RNAs (mRNAs) of protein-coding
Table 1 miRNAs: functions and targets in ovarian cancer
microRNAs Function Targets Reference
miR-200 family Tumor suppressor ZEB1,ZEB2,βtubulin III [31,42,45,47,48,51-59,111,112]
(Loss of EMT)
Let-7 family Tumor suppressor KRAS,HRAS,C-MYC,HMGA-2,CyclinA,D1,D2,D3,CDC25,CDK6 [47,68-81,110,113,116,117]
(Chemosensitization)
miR-34a/b/c Tumor suppressor c-myc,CDK6,Notch-1,MET,E2f3,Bcl2,cyclinD1 [82,119]
(Reduced invasion/migration/proliferation)
miR-100 Tumor suppressor mTOR, PLK-1 [83-85]
(Increased sensitivity to rapamycin analogs)
miR-31 Tumor suppressor E2F2, STK40 [86]
(Increased apoptosis)
miR-214/199a* Oncogenic PTEN [51,87-91,93,112]
(Chemoresistance)
miR-376c Oncogenic ALK7 [21,98]
(Chemoresistance)
miR-93 Oncogenic PTEN [100-102]
(Chemoresistance)
miR-21 Oncogenic PTEN [47,51,104-107,112]
(Chemoresistance)
miRNAs in ovarian carcinoma can either be oncogenic or tumor suppressor. Tumor suppressor miRNAs suppress oncogenes resulting in either loss of EMT
(Epithelial Mesenchymal Transition), chemosensitization or tumor suppression. Whereas, oncogenic miRNAs target tumor suppressor genes leading to chemo
resistance and reduced survival.
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 3 of 11
http://www.ovarianresearch.com/content/5/1/44
genes and the transcriptional or post-transcriptional
regulation of their expression [26]. The first reported
link between miRNAs and cancer regarded chronic
lymphocytic leukemia, wherein miR-15 and miR-16 were
found to be deleted or down-regulated in a majority of
tumors [34]. Since then, changes in the expression level
of miRNAs have subsequently been detected in many
types of human tumors [35]. miRNAs have various roles
in oncogenesis as they can function either as tumor sup-
pressors (e.g., miR-15a and miR-16-1) or oncogenes (e.g.,
miR-155 or members of the miR-17–92 cluster). Recent
studies on the abnormal expression of miRNAs in can-
cer have described the following reasons for differential
expression: chromosomal rearrangements [36-38], gen-
omic copy number change [39,40], epigenetic modifica-
tions [41,42], defects in miRNA biogenesis pathway [43],
and regulation by transcription factors [44].
miRNAs in ovarian cancer
One of the seminal studies done on epithelial ovarian
cancer (EOC) and miRNA was done by Zhang et. al. in
2008 [45]. In this study the authors utilized an integra-
tive genomic approach to study miRNA deregulation in
human epithelial ovarian cancer. They compared mature
miRNA expression profiles in 18 ovarian cancer cell
lines and 4 immortalized, non neoplastic cell lines
derived from normal ovarian surface epithelium. Thirty
five miRNAs were found to be differentially expressed
between the two groups of cells. Out of these 35, only 4
were up-regulated, whereas the rest were mostly down-
regulated in cancer cells as compared to immortalized
non-neoplastic cell lines. The 4 up-regulated miRNAs
were miR-26b, miR-182, miR-103 and miR-26a. The list
of down-regulated miRNAs included prominent tumor
suppressors such as let-7d and miR-127. This showed
that miRNA expression profiles can distinguish malig-
nant from nonmalignant ovarian surface epithelium.
Zhang et. al. went on to analyze 106 primary human
ovarian cancer specimens of various stages and grades
using miRNA microarrays. They found that all tumor
suppressor miRNA alterations were related to down-
regulation in late stage tumors, which included miR-15a,
miR-34a and miR-34b. The authors also observed that
DNA copy number loss and epigenetic silencing are
mainly responsible for down-regulation of the miRNAs.
In the case of over-expressed miRNAs (oncogenic miR-
NAs such as miR-182) the chromosomal regions were
found to be amplified in a significant number of cancer
samples. Additionally, epigenetic alterations reduced the
expression of 16 out of 44 miRNAs which were down-
regulated in late-stage ovarian cancer as the expression
of these miRNAs, e.g. miR-34b, was restored by DNA
demethylation or histone deacetylase inhibiting agents.
In addition several studies have compared the expres-
sion profile of miRNAs in a large number of clinical
ovarian cancer samples to normal ovarian tissues, ovar-
ian epithelial cell lines or fallopian tubes [42,46-51]. The
following sections provide information regarding miR-
NAs that are suggested to be involved in the pathobiol-
ogy of ovarian cancer (Tables 1 and 2).
miRNA-200 family
The miR-200 family contains miR-200a, miR-200b, miR-
200c, miR-141 and miR-429 which are arranged in 2
clusters in the human genome. miR-200a, miR-200b and
miR-429 are located on chromosome 1, while miR-200c
and miR-141 are on chromosome 12 [52]. Iorio et. al.
[42] have shown that the miR-200 family is among the
most significantly over-expressed miRNAs in epithelial
ovarian cancer. The expression of miR-200a and miR-
200c was found to be up-regulated in three types of
ovarian cancer: serous, endometrioid and clear cell.
However, miR-200b and miR-141 are up-regulated in
endometrioid and serous subtypes. The role of the miR-
200 family in ovarian carcinoma is complicated. While
miR-200 family members are believed to be metastasis
suppressants, the majority of studies done on the family
relate to over expression in ovarian cancer. However,
some studies report that miR-200 family members are
either down regulated [48] or even unchanged [45].
These differing results may occur because of the use of
different normal controls or the inclusion of ovarian
stromal cells which lack miR−200 expression.
Further complicating the potential roles of the miR-
200 family members, recent studies have implicated the
miR-200 family with the regulation of the epithelial to
Table 2 miRNA profile of subtypes of ovarian cancer
Type of ovarian
cancer
Up-regulated miRNA Down-regulated miRNA References
Serous miR-200a, miR-200b, miR-200c, miR-141, miR-93, miR-21,
miR-519a, miR-214
let7-b, miR-99a, miR-125b, miR-22, miR-
31, miR-34a/b/c
[42,47,51,86,102,106,108,109]
Clear Cell miR-519a, miR-182, miR-30a,miR-21, miR-200a, miR-200c miR-100, miR-22, miR-34a/b/c, miR-214 [42,51,83,109]
Mucinous miR-153, miR-485-5p [109]
Endometrioid miR-200a, miR-200b, miR-200c, miR-141 [42]
Most of the miRNA profiling has been done on the serous and clear cell ovarian carcinoma. miR-200 family stands out as the up-regulated miRNA in most types
of ovarian cancer. miR-100 plays a specific role in clear cell ovarian carcinoma.
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 4 of 11
http://www.ovarianresearch.com/content/5/1/44
mesenchymal transition (EMT). EMT is a process where
epithelial tumor cells are stimulated by extracellular
cytokines, e.g. TGFβ, or intracellular molecules such as
oncogenic Ras, to change their epithelial characteristics
into a mesenchymal phenotype with increased migratory
and invasive capabilities. EMT is induced by a group of
transcriptional repressors, such as Snail, Slug, TWIST,
Id2, ZEB1 and ZEB2. The protein levels of these re-
pressors increase during EMT, resulting in the down-
regulation of genes such as E-cadherin which are
responsible for the epithelial identity of the cells [53].
The E-cadherin molecules mediate cell-cell adhesion.
Park et. al. [54] have shown a positive correlation in the
expression of E-cadherin with the expression of miR-
200c in ovarian cancer tissues. The miR-200 family
members have also been shown to suppress the expres-
sion of ZEB1 and ZEB2, thereby suppressing EMT.
Over expression of miR-200 a/b/c and/or miR-141
down regulates ZEB1/2 levels, and leads to higher
levels of E-cadherin and an epithelial phenotype. On
the contrary, ZEB1/2 can inhibit the expression of
miR-200 family members by binding to the promoter
of both miR-200 clusters thereby blocking transcrip-
tion. The mechanistic explanation of the above process
can be summarized as follows: activation of a trigger
such as TGF-βor PDGF-D [52], leads to increased
levels of ZEB1/2, decreased expression of miR-200 and
the induction of EMT [31,54-57]. The miR-200 family
might be down regulated when cancer cells acquire in-
vasive properties and then become up-regulated when
the cells undergo mesenchymal to epithelial transition
during the process of re-epithelialization, which is evi-
dent from the positive correlation of miR-200 and E-
cadherin expressions [58].
In a recent study, Leskela et. al. [59] demonstrated the
role of the miR-200 family members in controlling β-
tubulin III expression and its association with paclitaxel-
based treatment response and progression-free survival
in ovarian cancer patients. Previous studies demon-
strated that high tumoral β-tubulin III expression has
been associated with decreased survival with non-small
cell lung cancer [60,61], breast [62], head and neck [63]
and ovarian cancer [64]. Moreover, a number of studies
have also shown that high expression of β-tubulin III is
associated with worse treatment response in ovarian
cancer [65-67]. Leskela et. al. found that tumors with
high levels of β-tubulin III protein have significantly
decreased miR-200 expression. They observed the stron-
gest associations with miR-141, miR-429 and miR-200c.
miR-200c expression was statistically significantly asso-
ciated with response to treatment as patients who did
not achieve a complete clinical response had lower levels
of miR-200c as compared to those showing a complete
response. Low expression of miR-200c was also
associated with recurrence of ovarian cancer. Moreover,
miR-429 expression was found to be significantly asso-
ciated with recurrence-free survival and overall survival
of the patients [59].
Let-7 family
The let-7 (lethal-7) family in humans consists of 13 miR-
NAs located on nine different chromosomes [68,69]. In
multiple human cancers expression of the let-7 family is
significantly reduced. Low let-7 expression has been
found to be associated with poor survival of cancer
patients [70,71]. Let-7 suppresses multiple ovarian can-
cer oncogenes, which includes KRAS,HRAS[72], c-MYC
[72] and HMGA-2 [73]. Moreover, it also inhibits cell
cycle regulators such as CDC25, CDK6 as well as Cyclin
A, D1, D2 and D3 [74,75]. The mechanism of down-
regulation for let-7 miRNAs is through copy-number
alterations [76]. The genomic locus containing let-7a-3/
let-7b was deleted in 44% of ovarian cancer samples
studied. Restoration of let-7b expression significantly
reduced ovarian tumor growth both in vitro and in vivo.
Additionally, recent studies have shown a correlation
between loss of let-7 and resistance to either chemother-
apeutic drugs or radiation [71,77-79]. Using a drug re-
sistant ovarian cancer cell line, Boyerinas et. al. [80]
demonstrated that drug sensitivity to taxanes is
increased upon over expression of let-7g as it inhibits
IMP-1, an RNA binding protein which stabilizes the
mRNA of a number of target genes, including, MDR1
(multidrug resistance-1). MDR1 is a member of the ad-
enosine triphosphate binding cassette transporters (ABC
transporter family) which pump drugs across the cell
membrane to the extracellular space. Therefore, the ex-
pression of let-7g resulted in a decrease in MDR1 and
sensitized the cells to Taxane treatment.
On the other hand, Lu et. al. [81] observed that ovar-
ian cancer patients responding to a regimen of platinum
and paclitaxel had significantly lower let-7a expression
than those who did not respond to treatment. Moreover,
survival data indicated that patients with high let-7a sur-
vived better when they were treated with platinum only
(no paclitaxel) as compared to those having low expres-
sion of let-7a. The authors conclude that miRNA-let-7a
expression can be a potential marker for selection of
chemotherapeutic agents in ovarian cancer treatment.
miRNA-34 a/b/c
Quantitative-RT PCR and in-situ hybridization in a
panel of 83 human ovarian cancer samples showed a sig-
nificant decrease in miR-34a/b/c expression. The de-
crease was also correlated with the p53 status as p53
regulates the expression of miR-34 family members by
promoter methylation and copy number alterations [82].
Over-expression of miR-34 family members reduced
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 5 of 11
http://www.ovarianresearch.com/content/5/1/44
migration, invasion and cellular proliferation in ovarian
cancer cell lines, providing evidence that the loss of
miR-34 family members may be involved in the patho-
biology of ovarian cancer.
miRNA-100
miR-100 is a tumor suppressor which has been found to
be down-regulated in most of the ovarian cancer cell
lines, especially clear cell ovarian carcinoma cell lines
and ovarian cancer tissues [83,84]. miR-100 represses
mTOR (mammalian target of rapamycin) signaling and
increases sensitivity to the cancer drug everolimus (rapa-
mycin analog RAD001) in cell lines derived from clear
cell carcinomas. mTOR is a serine/threonine kinase and
is a downstream effector of the Akt signaling pathway.
mTOR has also been shown to be a possible therapeutic
target in both cisplatin-sensitive and cisplatin-resistant
clear cell ovarian carcinoma [85]. Low miR-100 expres-
sion was associated with shorter overall patient survival
and advanced stage ovarian cancer. Moreover, its expres-
sion has been shown to be an independent predictor of
overall survival in ovarian cancer patients. miR-100 also
inhibits the expression of the proto-oncogene PLK1
(Polo-like kinase-1) in ovarian cancer [84].
miRNA-31
miR-31 is under-expressed in both serous ovarian cancer
cell lines and tissues [86]. miRNA-31 inhibits the expres-
sion of cell cycle regulators such as E2F2 and STK40, a
repressor of p53 mediated transcription, and acts as a
tumor suppressor in ovarian cancer. Over expression of
miR-31 in ovarian cancer cell lines having non func-
tional p53 pathways lead to decreased proliferation and
increased caspase-mediated apoptosis, whereas, over ex-
pression of miR-31 had no effect on ovarian cancer cells
having wild-type p53 [86]. Thus, miRNA-31 might have
therapeutic roles in the case of cancers having p53
mutations.
miRNA-214/199a*
Up-regulation of miR-214 has been detected in various
human malignancies, including pancreatic, prostate, gas-
tric, breast and ovarian cancers as well as malignant
melanoma [51,87-90]. miR-214 has extensive roles in
chemo-resistance, tumor progression and metastasis
[51,87,88,91]. Yang et. al. [51] have shown that miR-214
induces cell survival and cisplatin resistance by targeting
PTEN. miRNA microarrays show the aberrant regulation
of 36 miRNAs between normal ovarian cells and epithe-
lial ovarian tumors [51]. miR-199a*, miR-214, miR-200a
and miR-100 were most highly differentially expressed.
miR-199a* and miR-214 were found to be up-regulated
in 53 and 56% of the tumor tissues, respectively. miR-
214 knockdown was found to abrogate cisplatin
resistance in cisplatin-resistant cell line A2780CP,
whereas exogenous expression of miR-214 renders
cisplatin-sensitive cell line A2780S and OV119 cells re-
sistant to cisplatin induced apoptosis. miR-214 activates
the Akt pathway by targeting PTEN, which normally
negatively regulates Akt. Constitutive activation of Akt
leads to chemo-resistance in different types of tumors
including ovarian cancer [92]. Thus, miR-214 possibly
plays an important role in cisplatin resistance by target-
ing the PTEN/Akt pathway. miR-199a and miR-214 have
been implicated in the process of differentiation of ovar-
ian cancer stem cells (CSCs) into mature ovarian cancer
cells [93]. Twist 1, a transcription factor belonging to
basic helix-loop-helix proteins has been shown to regu-
late the expression of both miR-199a and miR-214
which are part of the human Dnm3os gene. Twist 1 is
involved in the differentiation of multiple cell lineages,
including muscle, cartilage and osteogenic cells [94-97].
Twist 1 levels increase during the differentiation process
leading to an increase in miR-199a and miR-214, a de-
crease in IKKβexpression (target of miR-199a), and a
decrease in PTEN expression (target of miR-214). This
eventually results in an increase in the pAkt activity
leading to the process of differentiation.
miRNA-376c
miRNA-376c was earlier known as miR-368 and was
found to be over expressed in a subset of acute myeloid
leukemia [98]. Ye et. al. have shown that miR-376c pro-
motes cell proliferation, survival and spheroid formation
in ovarian cancer cells [21]. This is done by suppressing
activin receptor-like kinase 7 (ALK7) and its ligand
Nodal, which together are able to induce apoptosis in
human epithelial ovarian cancer cells. A previous study
had demonstrated that the Nodal-ALK7 pathway might
be involved in chemosensitivity [99]. miR-376c over ex-
pression significantly reduced the effect of cisplatin.
Moreover, miR-376c and siRNA inhibitors of Nodal
and ALK7 also blocked the effect of carboplatin.
Chemosensitive and chemoresistant ovarian tumors
showed a differential expression of ALK7 and miR-
376c. Immuno-histochemical staining was used to stain
tumors with ALK7 and miR-376c was detected using
real-time PCR, in patients showing a complete response
(CR) and those who had an incomplete response (IR).
Patients showing CR showed significant ALK7 staining,
whereas the staining intensity was very weak in patients
with IR. Additionally, the miR-376c expression level
was inversely related to ALK7 in both cases [21].
miRNA-93
miRNA-93 is part of the miR-106b-25 cluster [100]. It
has been shown to promote tumor growth and angio-
genesis by targeting integrin-β8 [101]. In ovarian cancer
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 6 of 11
http://www.ovarianresearch.com/content/5/1/44
it is up-regulated in cisplatin-resistant ovarian cancer
cells [102]. It regulates cisplatin chemosensitivity in cis-
platin resistant ovarian cancer cells OVCAR3 and
SKOV3 by targeting the phosphatase PTEN. Over-
expression of miR-93 in both these cells increased the
ratio of phosphorylated Akt/over the total Akt (pAkt/
total Akt). Phospho rylated-Akt has been shown to play
an important role in multiple drug resistance including
cisplatin [92,103].
miRNA-21
miR-21 is aberrantly expressed and functions as an
oncogenic miRNA in many tumors including ovarian
cancer [51,104,105]. In ovarian cancer cells it promotes
cell proliferation, invasion and migration through target-
ing PTEN [106]. miR-21 also has a role in resistance to
hypoxic conditions which inhibit tumor growth [107].
Protein kinase Akt2 induces miR-21 expression under
oxygen deprivation leading to suppression of tumor sup-
pressor proteins PTEN, PDCD4 and Sprouty 1 (targets
of miR-21). This results in resistance to hypoxia [107].
miRNA expression profiles of subtypes of ovarian cancer
In addition to the miRNAs discussed above, a number of
studies have profiled the miRNA expression of specific
subtypes of ovarian cancer. Nam et. al., used a custo-
mized miRNA microarray of 314 human miRNAs to
analyze the miRNA expression profiles of serous ovarian
cancer tissues as compared to normal ovarian tissues
[47]. They found differential expression of 23 miRNAs.
miR-21 was most frequently up-regulated and miR-125b
was most frequently down- regulated (Table-2). North-
ern blot analysis confirmed the up-regulation of miR-
200c, miR-93 and miR-141 and the down-regulation of
let-7b, miR-99a and miR-125b. In a separate study, Li et.
al. have shown a negative correlation between miR-22
expression and the metastatic potential in serous ovarian
cancer cell lines [108]. Additionally, miR-519a was found
to be significantly up-regulated in serous and clear cell
carcinomas as compared to the mucinous subtype in tis-
sue samples [109]. Higher expression of miR-519a in late
stage serous carcinoma showed positive correlation with
poor progression-free survival. miR-153 and miR-485-5p
were found to be up-regulated in mucinous ovarian car-
cinoma. The down-regulation of miR-153 and miR-485-
5p showed significant correlation with advanced clinical
stage FIGO (International Federation of Gynecology and
Obstetrics) grade 3 and miR-519a was found to be high
in clinical stages III and IV (advanced clinical stages) as
compared to stages I and II (early clinical stages) [109].
As mentioned above miR-100 has been shown to be
down-regulated in clear cell ovarian carcinoma cell lines
and its over-expression in them inhibited mTOR signal-
ing and enhanced sensitivity to rapamycin analog
RAD001 (everolimus) [83] (Table-2). In the same study
the authors show the down-regulation of miR-22 and
the up-regulation of miR-182 and miR-30a in clear cell
ovarian carcinoma cell lines. Over-expression of miR-22
and knockdown of miR-182 could alter the global gene
expression pattern of clear cell ovarian cell lines towards
a normal state [83].
miRNAs in ovarian cancer diagnostics / prognostics
Previous studies in ovarian carcinoma have shown that
miRNAs can be used in its diagnosis as well as progno-
sis. Lu et. al. [110] demonstrated that patients having
low let-7a-3 methylation had overall worse survival than
those with high methylation. The miRNA-200 family
plays an important role in ovarian cancer and it has been
shown that the miR-200 family cluster, which includes
miR-200a, miR-200b and miR-429, can predict poor sur-
vival when they are expressed at low levels [111]. Yang
et. al. [51] showed that miR-214, miR-199* and miR-
200a were associated with high-grade and late stage
tumors. In an interesting ovarian cancer study [112] the
authors profiled miRNA signatures from tumor-derived
exosomes. Levels of 8 miRNAs, which were previously
shown to have diagnostic potential (miR-21, 141, 200a,
200c, 200b, 203, 205 and miR-214), were compared in
exosomes isolated from serum specimens of women
with benign disease and various stages of cancer. The 8
miRNAs had similar expressions between cellular and
exosomal miRNAs, with no detection of exosomal miR-
NAs in control samples. The profile of exosomal miR-
NAs from ovarian cancer patients was distinctly
different from patients with benign disease. HMGA2/let-
7 ratio has also been used for prognostic studies [113].
High-mobility group AT-hook 2 (HMGA2), an early em-
bryonic gene is a target of miRNAs let-7a, let-7c and
let-7g. Higher HMGA2/let-7 ratio exhibited decreased
5-year progression-free survival (<10%) as compared to
a lower ratio (~40%).
Potential role of miRNAs in ovarian cancer therapeutics
miRNA therapeutics in ovarian cancer can take differ-
ent forms. Oncogenic miRNAs can be inhibited by
using antisense oligonucleotides, antagomirs, sponges
or locked nucleic acid (LNA) constructs [114]. Cancer
cells have dysregulation in several miRNAs at the
same time and targeting a single miRNA is not suffi-
cient for treatment. Multiple-target anti-miRNA anti-
sense oligodeoxyribonucleotide-MTG-AMO (Multiple
target-O-modified antagomirs) are used to inhibit mul-
tiple miRNAs at the same time [115]. The expression
of tumor suppressor miRNAs can be restored by
miRNA replacement therapy. Several miRNAs have
been used for this purpose. Use of let-7 miRNA
mimetics is a potential tool as intra-tumoral delivery
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 7 of 11
http://www.ovarianresearch.com/content/5/1/44
of let-7b has been shown to decrease the tumor bur-
den in lung tumors [116,117]. The miR-143-145 clus-
ter has been shown to be frequently deleted in
cancer. miR-143 and 145, delivered intravenously to
subcutaneous and orthotopic xenografts downregulated
the oncogenes RREB1 and KRAS [118]. One of the
more beneficial miRNA therapies is miR-34 replace-
ment therapy. P53 protein is known to enhance miR-
34 expression and it is mutated in many cancers
[119]. The intra-tumoral delivery of miR-34 mimics
impaired tumorigenesis on a xenograft model of non-
small cell lung cancer, and systemic delivery of miR-
34 reduced tumor growth of KrasLSL-G12D
+
mice
[117,120]. Certain small molecule compounds like
enoxacin have been shown to restore downregulated
miRNAs to a normal miRNA level or expression pat-
tern without affecting normal cells and with no tox-
icity in in vivo models [121,122].
miRNAs can also be used to sensitize tumors to
chemotherapy. The efflux of anticancer drugs by ABC
transporters is one of the main reasons resistance to
chemotherapy drugs develops. miR-9 has been shown to
negatively regulate SOX2 which induces the expression
of ABC transporters ABCC3 and ABCC6 [123]. Resist-
ance to tamoxifen is restored by the over expression of
miR-15 and miR-16. miR-15 and 16 suppress the anti-
apoptotic molecule BCL-2 and sensitize the cells to tam-
oxifen [124]. Similarly, use of antagomirs against miR-21
was found to sensitize cultured cells to the chemothera-
peutic agent 5-Fluorouracil (5-FU) [125].
One of the greatest challenges in RNAi therapy con-
tinues to be the delivery method of the therapeutic
siRNA or miRNA to the target cells. Future focus should
be aimed at addressing these issues by engineering an ef-
ficient delivery system by use of radiolabeled, tumor spe-
cific antibody conjugated nanoformulations to deliver
miRNA to the ovarian tumor site. It is very important
to formulate an effective delivery method, such as
nanotechnology-based delivery approach for microRNA
for therapy with the help of strategic image-guided
systemic delivery to the tumor. This will be a major
contribution in the field of cancer therapeutics and
will help overcome challenges in miRNA delivery. The
goal of this novel therapeutic approach is to effectively
encourage reprogramming of miRNA networks in can-
cer cells which may lead to a clinically translatable
miRNA-based therapy to benefit ovarian cancer
patients.
Conclusions
In spite of all the above advances there is still a long way
to go to understand and apply miRNA therapeutics in
cancer and ovarian cancer in particular. Identification of
unique patterns of deregulated miRNA expression in
ovarian cancer provides valuable information that may:
serve as molecular biomarkers for tumor diagnosis; iden-
tify low and high risk populations of patients, disease
prognosis and prevention of cancer, and predict thera-
peutic responses. One of the areas of improvement in
miRNA therapy has been to reduce or eliminate off-
target or non-specific effects. This regulatory network is
complex because of the fact that a single miRNA can
have multiple targets and several miRNAs can have a
single target. Therefore, careful designing of therapeutic
strategies is needed to overcome these technical issues.
Moreover, the identification of new strategies is required
to enhance the potency and stability of therapeutic
vectors and the specificity of their delivery to tissues.
We hope that with increased understanding of the role
of miRNAs in cancer development and by designing
more efficient miRNA-modulating molecules, miRNA
mediated cancer therapy will give a new impetus to
the cure for cancer including ovarian cancer.
Abbreviations
miRNA: MicroRNA; EMT: Epithelial to mesenchymal transition;
RISC: RNAinduced silencing complex; UTR: Untranslated region;
EOC: Epithelial ovarian cancer/ovarian cancer.
Competing interests
The authors declare that there are no financial and non financial competing
interests.
Authors’contributions
MSZ designed and drafted the manuscript; MJ, DMM and SK were involved
in the critical revision of the manuscript; SCC gave final approval of the
version to be published. All authors read and approved the final manuscript.
Acknowledgements
The authors thank Cathy Christopherson for editorial assistance and
Dr. Mohammed Sikander for preparing the figure. This work was partially
supported by grants to SCC from Governor’s Cancer 2010, the National
Institutes of Health Research Project Grant Program (RO1) (CA142736), and
(UO1) (CA162106A) and the Centers of Biomedical Research Excellence
(P20 RR024219).
Author details
1
Cancer Biology Research Center, Sanford Research/USD, 2301 East 60th
Street North, Sioux Falls SD 57104, USA.
2
Department of Obstetrics and
Gynecology, Sanford School of Medicine, The University of South Dakota,
2301 East 60th Street North, Sioux Falls SD 57105, USA.
3
Basic Biomedical
Science Division, Sanford School of Medicine, The University of South
Dakota, 2301 East 60th Street North, Sioux Falls SD 57105, USA.
Received: 20 October 2012 Accepted: 6 December 2012
Published: 13 December 2012
References
1. Siegel R, Naishadham D, Jemal A: Cancer statistics, 2012. CA Cancer J Clin
2012, 62(1):10–29.
2. Wright JD, Shah M, Mathew L, Burke WM, Culhane J, Goldman N, Schiff PB,
Herzog TJ: Fertility preservation in young women with epithelial ovarian
cancer. Cancer 2009, 115(18):4118–4126.
3. Fung-Kee-Fung M, Oliver T, Elit L, Oza A, Hirte HW, Bryson P: Optimal
chemotherapy treatment for women with recurrent ovarian cancer.
Curr Oncol 2007, 14(5):195–208.
4. Takano M, Kikuchi Y, Yaegashi N, Kuzuya K, Ueki M, Tsuda H, Suzuki M,
Kigawa J, Takeuchi S, Moriya T, et al:Clear cell carcinoma of the ovary: a
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 8 of 11
http://www.ovarianresearch.com/content/5/1/44
retrospective multicentre experience of 254 patients with complete
surgical staging. Br J Cancer 2006, 94(10):1369–1374.
5. du Bois A, Luck HJ, Meier W, Adams HP, Mobus V, Costa S, Bauknecht T,
Richter B, Warm M, Schroder W, et al:A randomized clinical trial of
cisplatin/paclitaxel versus carboplatin/paclitaxel as first-line treatment of
ovarian cancer. J Natl Cancer Inst 2003, 95(17):1320–1329.
6. Shih Ie M, Kurman RJ: Ovarian tumorigenesis: a proposed model based
on morphological and molecular genetic analysis. Am J Pathol 2004,
164(5):1511–1518.
7. Morgan RJ, Alvarez RD, Armstrong DK, Burger RA, Castells M, Chen LM,
Copeland L, Crispens MA, Gershenson D, Gray H, et al:Ovarian Cancer,
Version 3.2012. J Natl Compr Canc Netw 2012, 10(11):1339–1349.
8. Vergote I, du Bois A, Amant F, Heitz F, Leunen K, Harter P: Neoadjuvant
chemotherapy in advanced ovarian cancer: On what do we agree and
disagree. Gynecol Oncol 2012, Sep 21 (Epub ahead of print).
9. Gonzalez-Martin A, Chiva L: Emerging Concerns When Evidence-Based
Medicine Is Translated into Real Life: The Case of Neoadjuvant
Chemotherapy in Ovarian Cancer. Curr Oncol Rep 2012, Oct 9
(epub ahead of print).
10. Cannistra SA: Cancer of the ovary. N Engl J Med 2004, 351(24):2519–2529.
11. Rabik CA, Dolan ME: Molecular mechanisms of resistance and toxicity
associated with platinating agents. Cancer Treat Rev 2007, 33(1):9–23.
12. Fraser M, Bai T, Tsang BK: Akt promotes cisplatin resistance in human
ovarian cancer cells through inhibition of p53 phosphorylation and
nuclear function. Int J Cancer 2008, 122(3):534–546.
13. Behbakht K, Qamar L, Aldridge CS, Coletta RD, Davidson SA, Thorburn A,
Ford HL: Six1 overexpression in ovarian carcinoma causes resistance to
TRAIL-mediated apoptosis and is associated with poor survival. Cancer
Res 2007, 67(7):3036–3042.
14. Duan Z, Foster R, Bell DA, Mahoney J, Wolak K, Vaidya A, Hampel C, Lee H,
Seiden MV: Signal transducers and activators of transcription 3 pathway
activation in drug-resistant ovarian cancer. Clin Cancer Res 2006,
12(17):5055–5063.
15. Gan Y, Wientjes MG, Au JL: Expression of basic fibroblast growth factor
correlates with resistance to paclitaxel in human patient tumors.
Pharm Res 2006, 23(6):1324–1331.
16. Ferlini C, Raspaglio G, Cicchillitti L, Mozzetti S, Prislei S, Bartollino S, Scambia
G: Looking at drug resistance mechanisms for microtubule interacting
drugs: does TUBB3 work? Curr Cancer Drug Targets 2007, 7(8):704–712.
17. Bartel DP: MicroRNAs: genomics, biogenesis, mechanism, and function.
Cell 2004, 116(2):281–297.
18. Bartels CL, Tsongalis GJ: MicroRNAs: novel biomarkers for human cancer.
Clin Chem 2009, 55(4):623–631.
19. Sorrentino A, Liu CG, Addario A, Peschle C, Scambia G, Ferlini C: Role of
microRNAs in drug-resistant ovarian cancer cells. Gynecol Oncol 2008,
111(3):478–486.
20. Marchini S, Fruscio R, Clivio L, Beltrame L, Porcu L, Nerini IF, Cavalieri D,
Chiorino G, Cattoretti G, Mangioni C, et al:Resistance to platinum-based
chemotherapy is associated with epithelial to mesenchymal transition in
epithelial ovarian cancer. Eur J Cancer 2012, Aug 13, (Epub ahead of print).
21. Ye G, Fu G, Cui S, Zhao S, Bernaudo S, Bai Y, Ding Y, Zhang Y, Yang BB,
Peng C: MicroRNA 376c enhances ovarian cancer cell survival by
targeting activin receptor-like kinase 7: implications for chemoresistance.
J Cell Sci 2011, 124(Pt 3):359–368.
22. Lee RC, Feinbaum RL, Ambros V: The C. elegans heterochronic gene lin-4
encodes small RNAs with antisense complementarity to lin-14. Cell 1993,
75(5):843–854.
23. Wheeler BM, Heimberg AM, Moy VN, Sperling EA, Holstein TW, Heber S,
Peterson KJ: The deep evolution of metazoan microRNAs. Evol Dev 2009,
11(1):50–68.
24. Ambros V: The functions of animal microRNAs. Nature 2004,
431(7006):350–355.
25. Cai X, Hagedorn CH, Cullen BR: Human microRNAs are processed from
capped, polyadenylated transcripts that can also function as mRNAs.
RNA 2004, 10(12):1957–1966.
26. Kim YK, Kim VN: Processing of intronic microRNAs. EMBO J 2007,
26(3):775–783.
27. Pratt AJ, MacRae IJ: The RNA-induced silencing complex: a versatile
gene-silencing machine. J Biol Chem 2009, 284(27):17897–17901.
28. Fabian MR, Mathonnet G, Sundermeier T, Mathys H, Zipprich JT, Svitkin YV,
Rivas F, Jinek M, Wohlschlegel J, Doudna JA, et al:Mammalian miRNA RISC
recruits CAF1 and PABP to affect PABP-dependent deadenylation.
Mol Cell 2009, 35(6):868–880.
29. Grimson A, Farh KK, Johnston WK, Garrett-Engele P, Lim LP, Bartel DP:
MicroRNA targeting specificity in mammals: determinants beyond seed
pairing. Mol Cell 2007, 27(1):91–105.
30. Gu S, Jin L, Zhang F, Sarnow P, Kay MA: Biological basis for restriction of
microRNA targets to the 3' untranslated region in mammalian mRNAs.
Nat Struct Mol Biol 2009, 16(2):144–150.
31. Vasudevan S, Tong Y, Steitz JA: Cell-cycle control of microRNA-mediated
translation regulation. Cell Cycle 2008, 7(11):1545–1549.
32. Lewis BP, Shih IH, Jones-Rhoades MW, Bartel DP, Burge CB: Prediction of
mammalian microRNA targets. Cell 2003, 115(7):787–798.
33. Flynt AS, Lai EC: Biological principles of microRNA-mediated regulation:
shared themes amid diversity. Nat Rev Genet 2008, 9(11):831–842.
34. Calin GA, Dumitru CD, Shimizu M, Bichi R, Zupo S, Noch E, Aldler H,
Rattan S, Keating M, Rai K, et al:Frequent deletions and down-regulation
of micro- RNA genes miR15 and miR16 at 13q14 in chronic lymphocytic
leukemia. Proc Natl Acad Sci U S A 2002, 99(24):15524–15529.
35. Zhang W, Dahlberg JE, Tam W: MicroRNAs in tumorigenesis: a primer.
Am J Pathol 2007, 171(3):728–738.
36. Calin GA, Ferracin M, Cimmino A, Di Leva G, Shimizu M, Wojcik SE, Iorio MV,
Visone R, Sever NI, Fabbri M, et al:A MicroRNA signature associated with
prognosis and progression in chronic lymphocytic leukemia. N Engl J
Med 2005, 353(17):1793–1801.
37. Calin GA, Croce CM: Chromosomal rearrangements and microRNAs: a
new cancer link with clinical implications. J Clin Invest 2007,
117(8):2059–2066.
38. Tagawa H, Seto M: A microRNA cluster as a target of genomic
amplification in malignant lymphoma. Leukemia 2005, 19(11):2013–2016.
39. Calin GA, Sevignani C, Dumitru CD, Hyslop T, Noch E, Yendamuri S,
Shimizu M, Rattan S, Bullrich F, Negrini M, et al:Human microRNA genes
are frequently located at fragile sites and genomic regions involved in
cancers. Proc Natl Acad Sci U S A 2004, 101(9):2999–3004.
40. Giannakakis A, Sandaltzopoulos R, Greshock J, Liang S, Huang J, Hasegawa
K, Li C, O'Brien-Jenkins A, Katsaros D, Weber BL, et al:miR-210 links hypoxia
with cell cycle regulation and is deleted in human epithelial ovarian
cancer. Cancer Biol Ther 2008, 7:255–264.
41. Saito Y, Liang G, Egger G, Friedman JM, Chuang JC, Coetzee GA, Jones PA:
Specific activation of microRNA-127 with downregulation of the proto-
oncogene BCL6 by chromatin-modifying drugs in human cancer cells.
Cancer Cell 2006, 9(6):435–443.
42. Iorio MV, Visone R, Di Leva G, Donati V, Petrocca F, Casalini P, Taccioli C,
Volinia S, Liu CG, Alder H, et al:MicroRNA signatures in human ovarian
cancer. Cancer Res 2007, 67(18):8699–8707.
43. Kumar MS, Lu J, Mercer KL, Golub TR, Jacks T: Impaired microRNA
processing enhances cellular transformation and tumorigenesis. Nat
Genet 2007, 39(5):673–677.
44. He L, He X, Lim LP, de Stanchina E, Xuan Z, Liang Y, Xue W, Zender L,
Magnus J, Ridzon D, et al:A microRNA component of the p53 tumour
suppressor network. Nature 2007, 447(7148):1130–1134.
45. Zhang L, Volinia S, Bonome T, Calin GA, Greshock J, Yang N, Liu CG,
Giannakakis A, Alexiou P, Hasegawa K, et al:Genomic and epigenetic
alterations deregulate microRNA expression in human epithelial ovarian
cancer. Proc Natl Acad Sci U S A 2008, 105(19):7004–7009.
46. Zhang L, Huang J, Yang N, Greshock J, Megraw MS, Giannakakis A, Liang S,
Naylor TL, Barchetti A, Ward MR, et al:microRNAs exhibit high frequency
genomic alterations in human cancer. Proc Natl Acad Sci U S A 2006,
103(24):9136–9141.
47. Nam EJ, Yoon H, Kim SW, Kim H, Kim YT, Kim JH, Kim JW, Kim S: MicroRNA
expression profiles in serous ovarian carcinoma. Clin Cancer Res 2008,
14(9):2690–2695.
48. Dahiya N, Sherman-Baust CA, Wang TL, Davidson B, Shih Ie M, Zhang Y,
Becker KG, Morin PJ, Wood W: MicroRNA expression and identification
of putative miRNA targets in ovarian cancer. PLoS One 2008,
3(6):e2436.
49. Wyman SK, Parkin RK, Mitchell PS, Fritz BR, O'Briant K, Godwin AK, Urban N,
Drescher CW, Knudsen BS, Tewari M: Repertoire of microRNAs in epithelial
ovarian cancer as determined by next generation sequencing of small
RNA cDNA libraries. PLoS One 2009, 4(4):e5311.
50. Lee CH, Subramanian S, Beck AH, Espinosa I, Senz J, Zhu SX, Huntsman D,
van de Rijn M, Gilks CB: MicroRNA profiling of BRCA1/2 mutation-carrying
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 9 of 11
http://www.ovarianresearch.com/content/5/1/44
and non-mutation-carrying high-grade serous carcinomas of ovary.
PLoS One 2009, 4(10):e7314.
51. Yang H, Kong W, He L, Zhao JJ, O'Donnell JD, Wang J, Wenham RM,
Coppola D, Kruk PA, Nicosia SV, et al:MicroRNA expression profiling in
human ovarian cancer: miR-214 induces cell survival and cisplatin
resistance by targeting PTEN. Cancer Res 2008, 68(2):425–433.
52. Korpal M, Lee ES, Hu G, Kang Y: The miR-200 family inhibits epithelial-
mesenchymal transition and cancer cell migration by direct targeting of
E-cadherin transcriptional repressors ZEB1 and ZEB2. J Biol Chem 2008,
283(22):14910–14914.
53. Huber MA, Kraut N, Beug H: Molecular requirements for epithelial-
mesenchymal transition during tumor progression. Curr Opin Cell Biol
2005, 17(5):548–558.
54. Park SM, Gaur AB, Lengyel E, Peter ME: The miR-200 family determines the
epithelial phenotype of cancer cells by targeting the E-cadherin
repressors ZEB1 and ZEB2. Genes Dev 2008, 22(7):894–907.
55. Gregory PA, Bert AG, Paterson EL, Barry SC, Tsykin A, Farshid G, Vadas MA,
Khew-Goodall Y, Goodall GJ: The miR-200 family and miR-205 regulate
epithelial to mesenchymal transition by targeting ZEB1 and SIP1. Nat Cell
Biol 2008, 10(5):593–601.
56. Gregory PA, Bracken CP, Bert AG, Goodall GJ: MicroRNAs as regulators of
epithelial-mesenchymal transition. Cell Cycle 2008, 7(20):3112–3118.
57. Kong D, Li Y, Wang Z, Banerjee S, Ahmad A, Kim HR, Sarkar FH: miR-200
regulates PDGF-D-mediated epithelial-mesenchymal transition, adhesion,
and invasion of prostate cancer cells. Stem Cells 2009, 27(8):1712–1721.
58. Imai T, Horiuchi A, Shiozawa T, Osada R, Kikuchi N, Ohira S, Oka K, Konishi I:
Elevated expression of E-cadherin and alpha-, beta-, and gamma-
catenins in metastatic lesions compared with primary epithelial ovarian
carcinomas. Hum Pathol 2004, 35(12):1469–1476.
59. Leskela S, Leandro-Garcia LJ, Mendiola M, Barriuso J, Inglada-Perez L, Munoz
I, Martinez-Delgado B, Redondo A, de Santiago J, Robledo M, et al:The
miR-200 family controls beta-tubulin III expression and is associated with
paclitaxel-based treatment response and progression-free survival in
ovarian cancer patients. Endocr Relat Cancer 2011, 18(1):85–95.
60. Rosell R, Scagliotti G, Danenberg KD, Lord RV, Bepler G, Novello S, Cooc J,
Crino L, Sanchez JJ, Taron M, et al:Transcripts in pretreatment biopsies
from a three-arm randomized trial in metastatic non-small-cell lung
cancer. Oncogene 2003, 22(23):3548–3553.
61. Seve P, Mackey J, Isaac S, Tredan O, Souquet PJ, Perol M, Lai R, Voloch A,
Dumontet C: Class III beta-tubulin expression in tumor cells predicts
response and outcome in patients with non-small cell lung cancer
receiving paclitaxel. Mol Cancer Ther 2005, 4(12):2001–2007.
62. Seve P, Dumontet C: Is class III beta-tubulin a predictive factor in
patients receiving tubulin-binding agents? Lancet Oncol 2008,
9(2):168–175.
63. Koh Y, Kim TM, Jeon YK, Kwon TK, Hah JH, Lee SH, Kim DW, Wu HG, Rhee
CS, Sung MW, et al:Class III beta-tubulin, but not ERCC1, is a strong
predictive and prognostic marker in locally advanced head and neck
squamous cell carcinoma. Ann Oncol 2009, 20(8):1414–1419.
64. Ferrandina G, Zannoni GF, Martinelli E, Paglia A, Gallotta V, Mozzetti S,
Scambia G, Ferlini C: Class III beta-tubulin overexpression is a marker of
poor clinical outcome in advanced ovarian cancer patients. Clin Cancer
Res 2006, 12(9):2774–2779.
65. Kavallaris M, Kuo DY, Burkhart CA, Regl DL, Norris MD, Haber M, Horwitz SB:
Taxol-resistant epithelial ovarian tumors are associated with altered
expression of specific beta-tubulin isotypes. J Clin Invest 1997,
100(5):1282–1293.
66. Mozzetti S, Ferlini C, Concolino P, Filippetti F, Raspaglio G, Prislei S, Gallo D,
Martinelli E, Ranelletti FO, Ferrandina G, et al:Class III beta-tubulin
overexpression is a prominent mechanism of paclitaxel resistance in
ovarian cancer patients. Clin Cancer Res 2005, 11(1):298–305.
67. Umezu T, Shibata K, Kajiyama H, Terauchi M, Ino K, Nawa A, Kikkawa F:
Taxol resistance among the different histological subtypes of ovarian
cancer may be associated with the expression of class III beta-tubulin.
Int J Gynecol Pathol 2008, 27(2):207–212.
68. Roush S, Slack FJ: The let-7 family of microRNAs. Trends Cell Biol 2008,
18(10):505–516.
69. Pasquinelli AE, Reinhart BJ, Slack F, Martindale MQ, Kuroda MI, Maller B,
Hayward DC, Ball EE, Degnan B, Muller P, et al:Conservation of the
sequence and temporal expression of let-7 heterochronic regulatory
RNA. Nature 2000, 408(6808):86–89.
70. Takamizawa J, Konishi H, Yanagisawa K, Tomida S, Osada H, Endoh H,
Harano T, Yatabe Y, Nagino M, Nimura Y, et al:Reduced expression of the
let-7 microRNAs in human lung cancers in association with shortened
postoperative survival. Cancer Res 2004, 64(11):3753–3756.
71. Yang N, Kaur S, Volinia S, Greshock J, Lassus H, Hasegawa K, Liang S,
Leminen A, Deng S, Smith L, et al:MicroRNA microarray identifies Let-7i
as a novel biomarker and therapeutic target in human epithelial ovarian
cancer. Cancer Res 2008, 68(24):10307–10314.
72. Johnson SM, Grosshans H, Shingara J, Byrom M, Jarvis R, Cheng A, Labourier
E, Reinert KL, Brown D, Slack FJ: RAS is regulated by the let-7 microRNA
family. Cell 2005, 120(5):635–647.
73. Bussing I, Slack FJ, Grosshans H: let-7 microRNAs in development, stem
cells and cancer. Trends Mol Med 2008, 14(9):400–409.
74. Johnson CD, Esquela-Kerscher A, Stefani G, Byrom M, Kelnar K, Ovcharenko
D, Wilson M, Wang X, Shelton J, Shingara J, et al:The let-7 microRNA
represses cell proliferation pathways in human cells. Cancer Res 2007,
67(16):7713–7722.
75. Schultz J, Lorenz P, Gross G, Ibrahim S, Kunz M: MicroRNA let-7b targets
important cell cycle molecules in malignant melanoma cells and
interferes with anchorage-independent growth. Cell Res 2008,
18(5):549–557.
76. Wang Y, Hu X, Greshock J, Shen L, Yang X, Shao Z, Liang S, Tanyi JL, Sood
AK, Zhang L: Genomic DNA Copy-Number Alterations of the let-7 Family
in Human Cancers. PLoS One 2012, 7(9):e44399.
77. Chen GQ, Zhao ZW, Zhou HY, Liu YJ, Yang HJ: Systematic analysis of
microRNA involved in resistance of the MCF-7 human breast cancer cell
to doxorubicin. Med Oncol 2010, 27(2):406–415.
78. Blower PE, Chung JH, Verducci JS, Lin S, Park JK, Dai Z, Liu CG, Schmittgen
TD, Reinhold WC, Croce CM, et al:MicroRNAs modulate the
chemosensitivity of tumor cells. Mol Cancer Ther 2008, 7(1):1–9.
79. Weidhaas JB, Babar I, Nallur SM, Trang P, Roush S, Boehm M, Gillespie E,
Slack FJ: MicroRNAs as potential agents to alter resistance to cytotoxic
anticancer therapy. Cancer Res 2007, 67(23):11111–11116.
80. Boyerinas B, Park SM, Murmann AE, Gwin K, Montag AG, Zillhardt M, Hua YJ,
Lengyel E, Peter ME: Let-7 modulates acquired resistance of ovarian
cancer to Taxanes via IMP-1-mediated stabilization of multidrug
resistance 1. Int J Cancer 2012, 130(8):1787–1797.
81. Lu L, Schwartz P, Scarampi L, Rutherford T, Canuto EM, Yu H, Katsaros D:
MicroRNA let-7a: a potential marker for selection of paclitaxel in ovarian
cancer management. Gynecol Oncol 2011, 122(2):366–371.
82. Corney DC, Hwang CI, Matoso A, Vogt M, Flesken-Nikitin A, Godwin AK,
Kamat AA, Sood AK, Ellenson LH, Hermeking H, et al:Frequent
downregulation of miR-34 family in human ovarian cancers. Clin Cancer
Res 2010, 16(4):1119–1128.
83. Nagaraja AK, Creighton CJ, Yu Z, Zhu H, Gunaratne PH, Reid JG, Olokpa E,
Itamochi H, Ueno NT, Hawkins SM, et al:A link between mir-100 and
FRAP1/mTOR in clear cell ovarian cancer. Mol Endocrinol 2010,
24(2):447–463.
84. Peng DX, Luo M, Qiu LW, He YL, Wang XF: Prognostic implications of
microRNA-100 and its functional roles in human epithelial ovarian
cancer. Oncol Rep 2012, 27(4):1238–1244.
85. Mabuchi S, Kawase C, Altomare DA, Morishige K, Sawada K, Hayashi M,
Tsujimoto M, Yamoto M, Klein-Szanto AJ, Schilder RJ, et al:mTOR is a
promising therapeutic target both in cisplatin-sensitive and cisplatin-
resistant clear cell carcinoma of the ovary. Clin Cancer Res 2009,
15(17):5404–5413.
86. Creighton CJ, Fountain MD, Yu Z, Nagaraja AK, Zhu H, Khan M, Olokpa E,
Zariff A, Gunaratne PH, Matzuk MM, et al:Molecular profiling uncovers a
p53-associated role for microRNA-31 in inhibiting the proliferation of
serous ovarian carcinomas and other cancers. Cancer Res 2010,
70(5):1906–1915.
87. Ueda T, Volinia S, Okumura H, Shimizu M, Taccioli C, Rossi S, Alder H, Liu CG,
Oue N, Yasui W, et al:Relation between microRNA expression and
progression and prognosis of gastric cancer: a microRNA expression
analysis. Lancet Oncol 2010, 11(2):136–146.
88. Penna E, Orso F, Cimino D, Tenaglia E, Lembo A, Quaglino E, Poliseno L,
Haimovic A, Osella-Abate S, De Pitta C, et al:microRNA-214 contributes to
melanoma tumour progression through suppression of TFAP2C.
EMBO J 2011, 30(10):1990–2007.
89. Volinia S, Calin GA, Liu CG, Ambs S, Cimmino A, Petrocca F, Visone R, Iorio
M, Roldo C, Ferracin M, et al:A microRNA expression signature of human
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 10 of 11
http://www.ovarianresearch.com/content/5/1/44
solid tumors defines cancer gene targets. Proc Natl Acad Sci U S A 2006,
103(7):2257–2261.
90. Blenkiron C, Goldstein LD, Thorne NP, Spiteri I, Chin SF, Dunning MJ,
Barbosa-Morais NL, Teschendorff AE, Green AR, Ellis IO, et al:MicroRNA
expression profiling of human breast cancer identifies new markers of
tumor subtype. Genome Biol 2007, 8(10):R214.
91. Qiang R, Wang F, Shi LY, Liu M, Chen S, Wan HY, Li YX, Li X, Gao SY, Sun BC,
et al:Plexin-B1 is a target of miR-214 in cervical cancer and promotes
the growth and invasion of HeLa cells. Int J Biochem Cell Biol 2011,
43(4):632–641.
92. Testa JR, Bellacosa A: AKT plays a central role in tumorigenesis. Proc Natl
Acad Sci U S A 2001, 98(20):10983–10985.
93. Yin G, Chen R, Alvero AB, Fu HH, Holmberg J, Glackin C, Rutherford T, Mor
G: TWISTing stemness, inflammation and proliferation of epithelial
ovarian cancer cells through MIR199A2/214. Oncogene 2010,
29(24):3545–3553.
94. Lee MS, Lowe GN, Strong DD, Wergedal JE, Glackin CA: TWIST, a basic
helix-loop-helix transcription factor, can regulate the human osteogenic
lineage. J Cell Biochem 1999, 75(4):566–577.
95. Lee MS, Lowe G, Flanagan S, Kuchler K, Glackin CA: Human Dermo-1 has
attributes similar to twist in early bone development. Bone 2000,
27(5):591–602.
96. Bialek P, Kern B, Yang X, Schrock M, Sosic D, Hong N, Wu H, Yu K, Ornitz
DM, Olson EN, et al:A twist code determines the onset of osteoblast
differentiation. Dev Cell 2004, 6(3):423–435.
97. Ota MS, Loebel DA, O'Rourke MP, Wong N, Tsoi B, Tam PP: Twist is
required for patterning the cranial nerves and maintaining the viability
of mesodermal cells. Dev Dyn 2004, 230(2):216–228.
98. Li Z, Lu J, Sun M, Mi S, Zhang H, Luo RT, Chen P, Wang Y, Yan M, Qian Z,
et al:Distinct microRNA expression profiles in acute myeloid leukemia
with common translocations. Proc Natl Acad Sci U S A 2008,
105(40):15535–15540.
99. Xu G, Zhong Y, Munir S, Yang BB, Tsang BK, Peng C: Nodal induces
apoptosis and inhibits proliferation in human epithelial ovarian cancer
cells via activin receptor-like kinase 7. J Clin Endocrinol Metab 2004,
89(11):5523–5534.
100. Li Y, Tan W, Neo TW, Aung MO, Wasser S, Lim SG, Tan TM: Role of the miR-
106b-25 microRNA cluster in hepatocellular carcinoma. Cancer Sci 2009,
100(7):1234–1242.
101. Fang L, Deng Z, Shatseva T, Yang J, Peng C, Du WW, Yee AJ, Ang LC, He C,
Shan SW, et al:MicroRNA miR-93 promotes tumor growth and
angiogenesis by targeting integrin-beta8. Oncogene 2011, 30(7):806–821.
102. Fu X, Tian J, Zhang L, Chen Y, Hao Q: Involvement of microRNA-93, a new
regulator of PTEN/Akt signaling pathway, in regulation of
chemotherapeutic drug cisplatin chemosensitivity in ovarian cancer
cells. FEBS Lett 2012, 586(9):1279–1286.
103. Altomare DA, Wang HQ, Skele KL, De Rienzo A, Klein-Szanto AJ, Godwin AK,
Testa JR: AKT and mTOR phosphorylation is frequently detected in
ovarian cancer and can be targeted to disrupt ovarian tumor cell
growth. Oncogene 2004, 23(34):5853–5857.
104. Si ML, Zhu S, Wu H, Lu Z, Wu F, Mo YY: miR-21-mediated tumor growth.
Oncogene 2007, 26(19):2799–2803.
105. Slaby O, Svoboda M, Fabian P, Smerdova T, Knoflickova D, Bednarikova M,
Nenutil R, Vyzula R: Altered expression of miR-21, miR-31, miR-143 and
miR-145 is related to clinicopathologic features of colorectal cancer.
Oncology 2007, 72(5–6):397–402.
106. Lou Y, Yang X, Wang F, Cui Z, Huang Y: MicroRNA-21 promotes the cell
proliferation, invasion and migration abilities in ovarian epithelial
carcinomas through inhibiting the expression of PTEN protein. Int J Mol
Med 2010, 26(6):819–827.
107. Polytarchou C, Iliopoulos D, Hatziapostolou M, Kottakis F, Maroulakou I,
Struhl K, Tsichlis PN: Akt2 regulates all Akt isoforms and promotes
resistance to hypoxia through induction of miR-21 upon oxygen
deprivation. Cancer Res 2011, 71(13):4720–4731.
108. Li J, Liang S, Yu H, Zhang J, Ma D, Lu X: An inhibitory effect of miR-22 on
cell migration and invasion in ovarian cancer. Gynecol Oncol 2010,
119(3):543–548.
109. Kim TH, Kim YK, Kwon Y, Heo JH, Kang H, Kim G, An HJ: Deregulation of
miR-519a, 153, and 485-5p and its clinicopathological relevance in
ovarian epithelial tumours. Histopathology 2010, 57(5):734–743.
110. Lu L, Katsaros D, de la Longrais IA, Sochirca O, Yu H: Hypermethylation of
let-7a-3 in epithelial ovarian cancer is associated with low insulin-like
growth factor-II expression and favorable prognosis. Cancer Res 2007,
67(21):10117–10122.
111. Hu X, Macdonald DM, Huettner PC, Feng Z, El Naqa IM, Schwarz JK,
Mutch DG, Grigsby PW, Powell SN, Wang X: A miR-200 microRNA cluster
as prognostic marker in advanced ovarian cancer. Gynecol Oncol 2009,
114(3):457–464.
112. Taylor DD, Gercel-Taylor C: MicroRNA signatures of tumor-derived
exosomes as diagnostic biomarkers of ovarian cancer. Gynecol Oncol
2008, 110(1):13–21.
113. Shell S, Park SM, Radjabi AR, Schickel R, Kistner EO, Jewell DA, Feig C,
Lengyel E, Peter ME: Let-7 expression defines two differentiation stages
of cancer. Proc Natl Acad Sci U S A 2007, 104(27):11400–11405.
114. Garzon R, Marcucci G, Croce CM: Targeting microRNAs in cancer:
rationale, strategies and challenges. Nat Rev Drug Discov 2010,
9(10):775–789.
115. Lu Y, Xiao J, Lin H, Bai Y, Luo X, Wang Z, Yang B: A single anti-microRNA
antisense oligodeoxyribonucleotide (AMO) targeting multiple microRNAs
offers an improved approach for microRNA interference. Nucleic Acids Res
2009, 37(3):e24.
116. Trang P, Medina PP, Wiggins JF, Ruffino L, Kelnar K, Omotola M, Homer R,
Brown D, Bader AG, Weidhaas JB, et al:Regression of murine lung tumors
by the let-7 microRNA. Oncogene 2010, 29(11):1580–1587.
117. Trang P, Wiggins JF, Daige CL, Cho C, Omotola M, Brown D, Weidhaas JB,
Bader AG, Slack FJ: Systemic delivery of tumor suppressor microRNA
mimics using a neutral lipid emulsion inhibits lung tumors in mice.
Mol Ther 2011, 19(6):1116–1122.
118. Pramanik D, Campbell NR, Karikari C, Chivukula R, Kent OA, Mendell JT,
Maitra A: Restitution of tumor suppressor microRNAs using a systemic
nanovector inhibits pancreatic cancer growth in mice. Mol Cancer Ther
2011, 10(8):1470–1480.
119. Suzuki HI, Yamagata K, Sugimoto K, Iwamoto T, Kato S, Miyazono K:
Modulation of microRNA processing by p53. Nature 2009,
460(7254):529–533.
120. Liu C, Kelnar K, Liu B, Chen X, Calhoun-Davis T, Li H, Patrawala L, Yan H,
Jeter C, Honorio S, et al:The microRNA miR-34a inhibits prostate cancer
stem cells and metastasis by directly repressing CD44. Nat Med 2011,
17(2):211–215.
121. Melo S, Villanueva A, Moutinho C, Davalos V, Spizzo R, Ivan C, Rossi S,
Setien F, Casanovas O, Simo-Riudalbas L, et al:Small molecule enoxacin is
a cancer-specific growth inhibitor that acts by enhancing TAR RNA-
binding protein 2-mediated microRNA processing. Proc Natl Acad Sci
USA2011, 108(11):4394–4399.
122. Shan G, Li Y, Zhang J, Li W, Szulwach KE, Duan R, Faghihi MA, Khalil AM,
Lu L, Paroo Z, et al:A small molecule enhances RNA interference and
promotes microRNA processing. Nat Biotechnol 2008, 26(8):933–940.
123. Jeon HM, Sohn YW, Oh SY, Kim SH, Beck S, Kim S, Kim H: ID4 imparts
chemoresistance and cancer stemness to glioma cells by derepressing
miR-9*-mediated suppression of SOX2. Cancer Res 2011, 71(9):3410–3421.
124. Cittelly DM, Das PM, Salvo VA, Fonseca JP, Burow ME, Jones FE: Oncogenic
HER2{Delta}16 suppresses miR-15a/16 and deregulates BCL-2 to
promote endocrine resistance of breast tumors. Carcinogenesis 2010,
31(12):2049–2057.
125. Hwang JH, Voortman J, Giovannetti E, Steinberg SM, Leon LG, Kim YT, Funel
N, Park JK, Kim MA, Kang GH, et al:Identification of microRNA-21 as a
biomarker for chemoresistance and clinical outcome following adjuvant
therapy in resectable pancreatic cancer. PLoS One 2010, 5(5):e10630.
doi:10.1186/1757-2215-5-44
Cite this article as: Zaman et al.:Current status and implications of
microRNAs in ovarian cancer diagnosis and therapy. Journal of Ovarian
Research 2012 5:44.
Zaman et al. Journal of Ovarian Research 2012, 5:44 Page 11 of 11
http://www.ovarianresearch.com/content/5/1/44
