Cytoprotection and Immunomodulation in Cancer Therapy

Abstract

Bioprospecting and natural products drug development for cancer treatment has become an important area. Most of the cancer chemotherapeutic agents are associated with toxicity towards normal cells and tissues. Optimal dosing of cancer chemotherapeutic agents is often limited because of severe non-myelosuppressive and myelosuppressive toxicities. It is a continuing challenge to design therapy that is safer, effective and selective. Cytoprotective agents offer opportunities to reduce treatment related toxicity of anticancer therapy without diminution of efficacy. None of the available agents satisfy criteria for an ideal cytoprotection. This has stimulated research for discovering natural resources with immunomodulatory and cytoprotective activities. This article describes chemical agents presently employed in clinical practice and reviews ethnopharmacological agents reported to have chemoprotective, radioprotective, immunomodulating, adaptogenic and antitumour activities.

Full text

Curr. Med. Chem. - Anti-Cancer Agents, 2004, 4, 000-000 1
1568-0118/04 $45.00+.00 © 2004 Bentham Science Publishers Ltd.
Cytoprotection and Immunomodulation in Cancer Therapy
Sham Diwanaya, Manish Gautamb and Bhushan Patwardhanb,*
aDepartment of Microbiology, Abasaheb Garware College, Pune, Pune – 411004, India, bBioprospecting Laboratory,
Interdisciplinary School of Health Sciences, University of Pune, Pune - 411007, India
Abstract: Bioprospecting and natural products drug development for cancer treatment has become an important area.
Most of the cancer chemotherapeutic agents are associated with toxicity towards normal cells and tissues. Optimal dosing
of cancer chemotherapeutic agents is often limited because of severe non-myelosuppressive and myelosuppressive
toxicities. It is a continuing challenge to design therapy that is safer, effective and selective. Cytoprotective agents offer
opportunities to reduce treatment related toxicity of anticancer therapy without diminution of efficacy. None of the
available agents satisfy criteria for an ideal cytoprotection. This has stimulated research for discovering natural resources
with immunomodulatory and cytoprotective activities. This article describes chemical agents presently employed in
clinical practice and reviews ethnopharmacological agents reported to have chemoprotective, radioprotective,
immunomodulating, adaptogenic and antitumour activities.
Key Words: Chemoprotection, Cytoprotection, Immunomodulation, Radioprotection, Cancer Chemotherapy, Ayurveda,
Withania somnifera.
A. INTRODUCTION
Chemotherapy is a major treatment modality used for the
control of advanced stages of malignancies and also as a
prophylactic against possible metastases in combination with
the radiotherapy [1]. Most of the chemotherapeutic agents
available today are cytotoxic and exert variety of side effects
mainly immunosuppression. The metabolism and clinical
safety of these agents has not been clearly established.
Chemical agents preventing site-specific toxicity of cyto-
toxic drugs are in current practice of cancer chemotherapy;
however, their use is limited because of loco-regional protec-
tion offered. This has given rise to stimulation in research for
locating natural resources showing immuno-logical activity.
Number of plant extracts has been shown to be immunomo-
dulators [2]. In past, variety of naturally occurring agents
including living and attenuated micro-organisms, autologous
and heterologous proteins, injections of animal organ
preparations were used to restore and repair defense
mechanism. Botanicals reported by various researchers as
immunomodulators, have exhibited promise as adjuvants for
cancer therapy. We describe here the chemical agents
presently employed in clinical practice as chemoprotectors
for anticancer drugs and review potential immunomodulators
from plants, some of these mentioned in Ayurveda as
Rasayana, exhibiting chemo-, radio- protection. Figure (1)
gives a schematic overview of cancer therapy approaches.
B. CHEMOPROTECTION: CONCEPT AND DEFINI-
TION
Cytoprotection and chemoprotection terms are inter-
changeable in cancer chemotherapy. Cytoprotection is the
*Address correspondence to this author at the Bioprospecting Laboratory,
Interdisciplinary School of Health Sciences, University of Pune, Pune -
411007, India, Tel: 91-20-25690174; Email: bhushan@unipune.ernet.in
general term used to describe process by which chemical
compounds provide protection to cells against harmful
agents. In cancer chemotherapy, chemoprotection refers to
cytoprotection against chemotherapeutic agents. Modern
cancer therapy produces substantial acute and chronic
toxicity, which needs to be avoided or modulated to improve
effectiveness of treatment. A host of agents (toxicity
antagonists) are under development that modulate normal
tissue response or interfere with mechanisms of toxicity. The
routine application of such agents could reduce treatment-
related morbidity and may allow treatment intensification in
high-risk disease [3]. Further, a chemoprotectant should not
add new toxicities that might limit the administration of
chemotherapeutic agent. Chemoprotectants with site
specificity are currently under development [4, 5].
C. IMMUNOMODULATION
The control of disease by immunologic means has two
objectives: to improve immunity and to avoid undesired
immune reactions. Apart from being specifically stimulatory
or suppressive, certain agents have been shown to possess
activity to normalise or modulate pathophysiologically
processes and are hence called immunomodulatory agents
[7]. Modulation of immunity was previously attempted with
glucocorticoids and cytotoxic drugs like cyclophosphamide
[6]. It is now recognised that immunomodulatory therapy
could provide an alternative to conventional chemotherapy
especially where host’s defense mechanisms have to be
activated under immunocompromised conditions or immuno-
suppression in situations like inflammatory diseases, auto-
immune disorders and organ/bone marrow transplantation
[8]. All three classes of immunomodulators: biologicals,
chemicals and cytokines will continue to play a major role in
advancing and improving the quality of treatment of several
of human as well as animal diseases.

2 Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 Diwanay et al.
D. IMMUNOMODULATION IN CANCER THERAPY:
CONCEPT AND DEFINITION
Immunomodulators are Biological Response Modifiers
(BRM), used to treat cancer, exert their antitumour effects by
improving host defense mechanisms against the tumour.
They have a direct anti-proliferative effect on tumour cells
and also enhance the ability of the host to tolerate damage by
toxic chemicals that may be used to destroy the cancer.
Chemical immunomodulators combined with other therapeu-
tic modalities have been used. Levamisole combined with 5-
FU in the treatment of stage C colorectal carcinoma has
established the usefulness of chemicals to augment the
immune response. [9]. There is need for further research to
better understand the biochemical mechanisms involved in
immunoregulation to maximise the benefits of chemical
immunomodulators as single agents or adjuvants in cancer
therapy [10]. Safer immunomodulating agents suitable for
long-term therapy remain unmet therapeutic need. Figure (2)
gives a schematic overview of cytoprotection and immuno-
modulation.
E. IMMUNOMODULATION IN RADIOTHERAPY
Radio therapeutics is still one of the major treatment
modalities practiced for control of localised solid tumours.
Strategies for the prevention of radiation injuries are being
explored to develop newer radioprotective and nontoxic
pharmacologics include: development of radiosenstisers;
apoptosis inducers in tumour cells; radioprotectants to
increase radiosensitivity of resistant tumours, to reduce the
radiation dose and to protect the normal tissue morbidity
associated with tumouricidal radiation doses. Available
radioprotective agents have not yet reached the criteria of
optimal radioprotectant. The optimal effect includes effec-
tiveness, specificity, availability, toxicity and tolerance. Use
of immunomodulators to protect radiation injury may be a
better alternative in radioprotection. Natural compounds may
have an advantage, being structurally diverse and safer,
hence therapeutically better acceptable [11].
F. CHEMICAL AGENTS AS CHEMOPROTECTANTS
AND IMMUNOMODULATORS
1. Chemoprotectants for Antimetabolites
Methotrexate
The best-studied chemoprotectant regimen involves
rescue from high-dose methotrexate bone marrow toxicity
using reduced folate derivative leucovorin (folinic acid).
However, leucovorin rescue is not truly site-specific and will
Fig. (1).

Cytoprotection and Immunomodulation in Cancer Therapy Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 3
principally depend on differences in tumour and normal cell
growth rates [12]. Preclinical studies show that asparaginase
administered before methotrexate can attenuate its toxicity
by inhibiting cellular protein synthesis. Reduced intracellular
polyglutamation of methotrexate by asparaginase reduces
drug retention and thereby causes more rapid methotrexate
efflux, with reduced toxicity [13].
5-Fluorouracil (5-FU)
The best-studied clinical interaction involves the modu-
lation of 5-FU myelotoxicity with concomitant allopurinol.
Selective chemoprotection involves inhibition of orotidine
monophosphate decarboxylase by allopurinol metabolite
oxipurinol. Selectivity for allopurinol depends on different
primary pathways or ratios of 5-FU activation in normal cells
and tumour cells [14]. The RNA base uridine has also been
reported to block 5-FU lethal toxicity in mice and humans.
Uridine diphosphoglucose (URDP), precursor of uridine
resulted modulation of 5–FU associated gastrointestinal
toxicity leading to protection. Uridine rescue from 5-FU
toxicity depends on prolonged exposure to uridine rather
than attaining high peak plasma levels of uridine [15-17].
Arotinoid Ro 40-8757
The arotinoid Ro 40-8757 (mofarotene) exhibited high
degree of activity against established, chemically induced
mammary tumours in rats, reducing tumour numbers. The
toxicities associated with these therapeutic effects are rela-
tively mild compared to those of all -trans retinoic acid or
13-cis retinoic acid given at doses with little or no anti-
tumour efficacy. Long-term treatment with Ro 40-8757
results in new growth of tumours. In rat mammary tumour
model, chronic administration of cyclophosphamide (5 days/
Fig. (2).
N
H
N
N
H
N
H
N
H
N
H2N
O
O
COOH
COOH
CHO
Leucovorin
N
N
OH
N
N
H
Allopurinol

4 Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 Diwanay et al.
week at 10 mg/kg) plus daily administration of arotinoid at a
relatively low dose (75 mg/kg/day), antitumour effect was
additive. However, the therapeutic effects were synergistic
because all of the animals treated with cyclophosphamide as
a single agent died after 6 weeks of treatment, whereas all of
the animals given the combination survived the full 10 weeks
of the experiment. Pharmacodynamic studies have exhibited
that the protective effect of Ro 40-8757 occurred at the level
of the bone marrow progenitors [18]. Combination therapy
of arotinoid Ro 40-8757 and 5-FU in rats resulted significant
reduction in number and burden of chemically induced
mammary tumours. Ro 40-8757 alone did not have an effect
on tumour burden. This protective effect of arotinoid makes
it a useful potential partner for combination therapy with 5-
FU [19].
2. Nucleophilic Sulfur Thiols as Alkylating Agent
Chemoprotectants
Administration of supplemental thiols or other compound
with an available reduced sulfur atom against DNA-
alkylating or DNA-binding drugs has biochemical rationale
of chemoprotection. The specificity for chemoprotection by
sulfur nucleophiles lies in their physical and pharmacokinetic
properties. Sodium thiosulfate concentrates in the renal
tubules during its rapid urinary elimination, indicating that,
thiosulfate will directly (and nonspecifically) inactivate any
electrophilic (alkylating) species in the urine or in the
bloodstream [20]. For this reason sodium thiosulfate is only
useful as a local chemoprotectant for alkylating agents like
mechlorethamine. The poor distribution of sodium thiosul-
fate into bone marrow further lessens its chemoprotectant
utility for agents like mechlorethamine.
Thiol-Based Chemoprotectants for Cisplatin and
Oxazophosphorine-Based Alkylating Agents
Reduction of associated nephrotoxicity and bone marrow
suppression was dealt by allowing dose escalation and
designing pharmacokinetically based dosing schedules.
However, new dose-limiting toxicities consisting of peri-
pheral neuropathy and ototoxicity have emerged restricting
potential use of high dose cisplatin therapy. Chemo protec-
tive agents, including sodium thiosulfate, WR2721 and
diethyldithiocarbamate (DDTC) are being extensively
examined as "rescue agents" for either regional or systemic
administration of cisplatin.
Sodium thiosulfate (STS) given concurrently or follow-
ing Cisplatin can produce a 12-fold greater exposure to
cisplatin in the intraperitoneal space with tumour regression.
This approach remains locoregional drug treatment, since
active form of sulfur nucleophile is distributed in the blood-
stream and could complex with cisplatin to abrogate its
intended systemic therapeutic effects [21]. Local application
of STS to prevent cisplatin toxicity retaining systemic
antitumoural effectiveness of Cisplatin has been suggested.
Cocheal administration resulted complete protection against
CDDP-induced hearing loss, with no change in compound-
action-potential (CAP) [22]. However, alleviation of
cisplatin induced side effects by administration of sodium
thiosulfate was not observed in mice xenograft tumour
model suggesting cisplatin-STS treatment would provide no
benefit in patients treated with cisplatin [23]. Several other
thiol-based compounds have shown activity in preventing
cisplatin-induced toxicities. These include the experimental
aminothiol WR-2721, the disulfide metal chelator diethyl-
dithiocarbamate (DDTC), mesna, N-acetylcysteine (NAC)
and thiourea. In the absence of a chemoprotectant, active
doses of ifosfamide can produce dose-limiting urotoxicity
manifested by hemorrhagic cystitis, bladder fibrosis and
heightened long-term risk of bladder cancer, Similar toxi-
cities are noted with chronic or acute high-dose cyclophos-
phamide dosing. Thus, both ifosfamide and high-dose
cyclophosphamide have limited clinical efficiency in the
absence of effective chemoprotectant of urinary bladder [4].
Mesna, sodium salt of 2-mercaptoethanesulfonic acid, is
a selective urinary tract protectant for oxazophosphorine-
type alkylating agents. Mesna blocks bladder damage from
major toxic metabolites of both ifosfamide and cyclophos-
phamide [24-26]. Mesna can specifically bind to cisplatin or
alkylating agent generated free radicals or alkylating agent
metabolites to reduce the incidence of cisplatin-associated
neurotoxicity and nephrotoxicity, or alkylating agents asso-
ciated myelosuppression and urothelial toxicity [27, 28].
Mesna does not block the antitumour activity of oxazophos-
phorines nor other classes of antitumour agents. Mesna is
superior to previous urinary prophylaxis regimens, among a
large series of SH-based uroprotectants with least toxicity of
any of the agents tested [29]. Mesna also attenuates the lethal
effect and hematological toxicity of vespeside and taxol but
do not reduce specific activities in mice with transplanted
tumours [30].
Amifostine
Amifostine is organic thiophosphate compound able to
selectively protect normal tissues against cytotoxic agents in
cellular and animal models, without protecting tumour
tissues. Amifostine is a prodrug, which is dephosphorylated
into its active metabolite, a free thiol derivative, by mem-
brane alkaline phosphatase of target tissue. This unique
metabolism supports its cellular selectivity and its preferen-
tial uptake by normal tissues. Preclinical animal studies have
demonstrated that administration of amistofine protects
against irradiation and variety of chemotherapy related toxi-
cities including cisplatin induced nephrotoxicity, neurotoxi-
city, cyclophosphamide and bleomycin induced pulmonary
toxicity and cardiotoxicity induced by doxorubicin and other
related chemotherapeutic agents. In non-randomised and
randomised trials in malignant melanoma, colorectal cancer,
head and neck cancer, non-small cell lung cancer and epi-
thelial ovarian carcinoma, amifostine significantly reduced
the hematological and non-hematological toxicity of DNA-
damaging agents such as alkylators, platinum compounds, or
mitomycin C. In more recent studies, amistofine also protec-
ted patients from side effects produced by taxanes or topo-
isomerase I inhibitors [31-33]. Currently, there is no evi-
dence that amifostine compromises the antineoplastic effect
of the drugs studied. Moreover, amifostine appears to
produce growth factor like properties resulting in growth-
promoting effects on primitive blood progenitor cells ex vivo.
In a randomised phase III study conducted in patients with
ovarian carcinoma receiving a combination of cisplatin and
cyclophosphamide; a significant decrease in hematological,
renal and neurologic toxicity was observed in amifostine-

Cytoprotection and Immunomodulation in Cancer Therapy Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 5
treated patients compared with the control group [34]. The
protective effect of amifostine has been demonstrated for
cisplatin-induced toxicity in lung and ovarian cancer, with
particular regard to nephrotoxicity, neurotoxicity and
neutropenia. No protective effect has been seen for tumour
cells owing to a selective action of amifostine on healthy
tissues. A frequent side effect of amifostine is a transient
decrease in blood pressure; it is usually asymptomatic if an
easily handled premedication is given. Cytoprotection by
amifostine is also well known for alkalyting drugs and
radiation therapy, whereas it is still the object of study for
new drugs, especially taxanes [35]. Amifostine also protects
bone marrow from cumulative toxicity arising from chronic
exposure to therapeutic agents such as alkylating agents.
Well-controlled clinical trials have shown that amifostine
can ameliorate cumulative bone marrow toxicity and the
acute and chronic neutropenic and/or thrombocytopenic
effects of cyclophosphamide. In a pivotal phase III study of
cisplatin/cyclophosphamide with or without amifostine,
amifostine reduced course-by-course cumulative bone
marrow damage when compared with the course-by-course
cumulative myelosuppression experienced by those treated
with Cisplatin / cyclophosphamide alone [36].
Disulfiram
Disulfiram (tetraethylthioperoxidicarbonic diamide), an
aldehyde dehydrogenase inhibitor, prevented cyclophos-
phamide-induced bladder damage in a dose-dependent
manner when administered simultaneously with cyclophos-
phamide (100-400 mg/kg, i.p.), but failed to diminish the
acute toxicity, leucotoxicity and immunotoxicity of cyclo-
phosphamide. Diethyldithiocarbamate (DDTC), metabolite
of disulfiram did not interfere with cyclophosphamide
antitumour activity when administered 3 hours after cyclo-
phosphamide. Protective effect of disulfiram on the bladder
was critically dependent on administration timing. Disul-
firam slightly potentiated the antitumour activity of cyclo-
phosphamide against Sarcoma-180 or EL-4 leukemia in vivo
when administered simultaneously with cyclophosphamide
[37].
Disulfiram is an effective protective agent against bladder
damage caused by ifosfamide treatment [38]. Disulfiram
(DSF) in combination with ifosfamide (IFX) prevented IFX-
induced bladder damage, but failed to diminish the acute
lethal toxicity or leukocytotoxicity of IFX. Diethyldithio-
carbamate (DDTC) prevented IFX-induced bladder damage
when administered simultaneously with IFX or 1 to 5 hr
afterwards. The antitumour activity of IFX in ddY-mice
inoculated with Sarcoma 180 or in C57BL/6J mice inocula-
ted with EL-4 leukemia was not impaired when it was given
simultaneously with DSF or 3 hr before DDTC. Thus,
neither DSF nor DDTC impaired the antitumour effect of
IFX and both diminished its adverse effects. The bladder
protection of DSF and DDTC appeared to be resulting from
adduct formation with acrolein and not from inhibition of the
metabolic activation of IFX [39]. Disulfiram (DSF) blocks
the urotoxicity of cyclophosphamide in mice and increases
the oncolytic effect of cyclophosphamide in the L1210
murine leukemia. However, mice treated with cyclophos-
phamide and DSF appeared to have longer-lasting neutro-
penia than animals treated with cyclophosphamide alone.
Bone marrow granulocyte/macrophage progenitor cell (GM-
CFC) were relatively well preserved and the recovery of the
GM-CFC was not prolonged by DSF; indicating, acute cyto-
toxic effect of cyclophosphamide on the granulocyte/macro-
phage progenitor cells is not enhanced by DSF [40].
3. Chemoprotectants for Anthracyclines
Anthracyclins like doxorubicin and daunomycin com-
prise one of the most important classes of DNA-binding
antitumour agents. Short- and long-term cardiotoxicity can
occur at lower doses, the use of these drugs is limited by a
characteristic clinical cardio-myopathy that develops in
approximately 5% to 15 % patients after cumulative doxoru-
bicin doses greater than 450 mg/m2. Children and adole-
scents appear to be particularly sensitive to the cardiotoxic
effects of doxorubicin. Although cumulative doxorubicin
doses are usually limited to ≤450 mg/m2, up to 70 % of long-
term survivors of childhood cancer have evidence of cardiac
dysfunction, including overt congestive heart failure [41].
Anthracyclines complexed with metals can sustain lipid
peroxidation and scavengers of reduced oxygen free radicals
including superoxide dismutase, catalase and mannitol do
not block its action [42]. A variety of putative free radical
scavengers have been shown to protect against doxorubicin
cardiotoxicity in experimental animals. These include the
lipid-soluble antioxidant vitamin E [43] and N-acetylcysteine
(NAC). Despite positive preclinical results, NAC was not
effective in cancer patients given high cumulative doxoru-
bicin doses [44].
ICRF-187
Piperazine derivative of ethylenediaminetetraacetate
razoxane (ICRF-187) is a prodrug that is converted
intracellularly to an iron-chelating agent that removes iron
from doxorubicin-iron complexes in vitro. Dexrazoxane is a
cardioprotective antioxidant that is clinically used to reduce
the cardiotoxicity of the chemotherapeutic drug doxorubicin,
paclitaxel and other anthracyclins [45]. Although the cardio-
protective effect of dexrazoxane in cancer patients under-
going chemotherapy with anthracyclines is well documented,
the potential of this drug to modulate topoisomerase II
activity and cellular iron metabolism may hold the key for
future applications of dexrazoxane in cancer therapy,
immunology, or infectious diseases [46].
G. BOTANICALS AS CHEMOPROTECTANTS AND
IMMUNOMODULATORS
Various ethnopharmacological agents are under investi-
gation as immunomodulators. Modulation of immune res-
ponses to alleviate the diseases has been of interest for many
years and the concept of ‘Rasayana’ in Ayurveda is based on
related principles. Ayurveda remains one of the most ancient
and yet living traditions practiced widely in India, Sri Lanka
and other countries and has a sound philosophical and expe-
riential basis. A considerable research on pharmacognosy,
chemistry, pharmacology and clinical therapeutics has been
carried out and Ayurvedic database has detailed descriptions
of over 700 medicinal plants [47, 48]. Rasayanas are non-
toxic herbal preparations or individual herbs used to
rejuvenate or attain the complete potential of healthy and or
diseased individual in order to prevent diseases and degene-

6 Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 Diwanay et al.
rative changes that leads to disease. Pharmacodynamic
studies on Ayurvedic botanicals have suggested many possi-
ble mechanisms such as nonspecific and specific immuno-
stimulation, free radicals quenching, cellular detoxification,
cell proliferation and repair [49].
Withania Somnifera
It is an official drug mentioned in the Indian Herbal
Pharmacopoeia [48] and Ayurvedic Pharmacopoeia [49].
Studies indicate that Withania somnifera (Ashwagandha)
(WS) possesses anti-inflammatory, antitumour, antistress,
antioxidant, immunomodulatory, hemopoietic and rejuvenat-
ing properties. The chemistry of WS has been extensively
studied and over 35 chemical constituents have been
identified, extracted and isolated. The biologically active
chemical constituents are alkaloids (isopelletierine, anafer-
ine), steroidal lactones (withanolides, withaferins), saponins
containing an additional acyl group (sitoindoside VII and
VIII) and withanolides with a glucose at carbon 27
(sitoindoside IX and X) [50].
Withania Somnifera – Chemoprotection
Suppressive effect of cyclophosphamide-induced toxicity
by WS extracts was observed in mice. Administration of WS
extracts significantly reduced leucopenia induced by
cyclophosphamide treatment, resulting increase in bone
marrow cellularity. The major activity of WS may be due to
stimulation of stem cell proliferation, indicating that WS
could reduce the cyclophosphamide toxicity and its
usefulness in cancer chemotherapy [51]. WS was also shown
to prevent lipid peroxidation (LPO) in stress-induced animals
indicating its adjuvant well as chemoprotectant activity [52].
Significant modulation of immune reactivity was
observed in drug-induced myelosuppression animal model.
Significant increase in haemoglobin concentration, red blood
cell count, white blood cell count, platelet count, body
weight and haemolytic antibody titres was observed in
cyclophosphamide, azathioprin or prednisolone treated
animals receiving WS extract, indicating preventive action
against myelosuppression [6]. Pretreatment with WS,
Tinospora cordifolia, Asparagus racemosus, induced a
significant leucocytosis in cyclophosphamide-induced
myelosuppresed animals. PMN functions, in terms of
phagocytosis and intra-cellular killing were stimulated, as
well as reticulo-endothelial system functions were greatly
activated in treated animals. The phagocytic functions of
peritoneal and alveolar macrophages were also stimulated.
WS treatment also improved the carbon clearance, indicating
stimulation of the reticulo-endothelial system [53]. In a
comparative pharmacological investigation of WS and
Ginseng treatment showed a significant difference in anti-
stress activity. Ginseng exhibited higher anti-stress activity,
however, gastric ulcers due to swimming stress were notably
less in WS treated mice. The anabolic study revealed that
WS treated group had a greater gain in the body weight than
the Ginseng treated group [54]. Glycowithanolides, consis-
ting of equimolar concentrations of sitoindosides VII-X and
withaferin A, isolated from the roots of WS were evaluated
for protection in iron induced hepatoxicity in rats. 10 days of
oral administration of these active principles, in graded doses
(10, 20 and 50 mg/kg), resulted attenuation of hepatic lipid
peroxidation (LPO), the serum enzymes, alanine aminotrans-
ferase, aspartate aminotransferase and lactate dehydrogenase
during iron-induced hepatoxicity [55].
Withania Somnifera as Radioprotectant and Radiosensi-
tiser
Withaferin A: a steroidal lactone from WS inhibited
growth of Ehrlich ascites carcinoma in Swiss mice with
increased survival and life span. Antitumour and radiosensi-
tising effect was observed with combination treatment of
abdominal gamma irradiation with withaferin A, resulting in
increased tumour cure and tumour-free survival [56].
Withaferin A showed growth inhibitory effect in vitro on
both Chinese hamster V79 cells and HeLa cells. It reduced
the survival of V79 cells in a dose-dependent manner [57].
Withaferin A pretreatment before irradiation significantly
enhanced cell killings and showed radiosensitising potential.
It induces G2 M block with maximum accumulation of cells
in G2 –M phase. Withaferin A in combination with radio-
therapy synergistically increased the response to radioresis-
tant tumours [58]. Combination treatment of alcoholic
extract of Withania somnifera (500 mg/kg, i.p., 10 days)
with one local exposure to gamma radiation (10 Gy)
followed by hyperthermia (430 C for 30 minutes) signifi-
cantly increased the tumour cure (Sarcoma 180 grown on the
dorsum of adult BALB/c mouse), growth delay and animal
survival. This combination was also significantly and
synergistically depleted the tumour GSH level. Thus,
Ashwagandha, in addition to having a tumour inhibitory
effect, also acts as a radiosensitiser. The severe depletion in
the tumour GSH content by the combination treatment must
have enhanced the tumour response, as the inherent protec-
tion by the thiol will be highly reduced [59]. The presence of
a wide variety of effects such as hypotensive, antispasmodic,
antitumour, anti-arthritic, antipyretic, analgesic, anti-
inflammatory and hepatoprotective activities and antistress
properties show that WS may be acting by non-specifically
increasing the resistance of the animals to various stressful
conditions [60].
One of the major side effects of radiotherapy is tissue
injury in the target and non-target cells, especially cells of
immune system. Owing to the extremely high radiosensi-
tivity of bone marrow, damage to hemopoietic system to
some extent is always observed in whole body irradiation as
its typical manifestation. Administrations of methanolic
extract of the plant was found to significantly increase white
cell total counts in normal BALB/c mice and reduce the
leucopenia induced by sublethal dose of gamma radiation.
Treatment with WS was found to increase the bone marrow
cellularity significantly, normalisation of normochromatic
erythrocyte and polychromatic erythrocyte ratio in mice after
the radiation exposure. Major activity of WS seemed to be in
the stimulation of stem cell proliferation [61]. The finding
that withaferin A has a good cytotoxic effect at higher doses
and radiosensitising effect even at subtoxic doses in
encouraging. This property can be exploited to the advantage
of cancer patients. The pilot clinical studies have already
indicated the effectiveness of oral administration and lack of
systemic toxicity even after repeated administration. Some
preclinical studies suggest that the extract may also act as a
chemopreventive against tumour induction [58].

Cytoprotection and Immunomodulation in Cancer Therapy Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 7
Withania Somnifera as Antitumour
In a recent report 12 withanolides were isolated from
leaves and were evaluated for their antiproliferative activity
on NCI-H460 (Lung), HCT-116 (Colon), SF-268 (Central
Nervous System; CNS and MCF-7 (Breast) human tumour
cell lines. Withaferin A and its derivatives exhibited
inhibitory concentrations (50%) ranging from 0.24 +/- 0.01
to 11.6 +/- 1.9 microg/mL. Viscosalactone B (12) showed
the 50% inhibition at concentrations ranging from 0.32 +/-
0.05 to 0.47 +/- 0.15 microg/mL whereas its 27-O-glucoside
derivative (10) exhibited IC50 between 7.9 +/- 2.9 and 17.3
+/- 3.9 microg/ml. However, Physagulin D type withanolides
showed either weak or no activity at 30 microg/mL [62].
Withaferin A also exhibited dose dependent in vivo growth
inhibitory effects in Swiss albino mice inoculated with 106
Ehrlich ascites carcinoma cells at 30mg/kg dose.
Withania Somnifera as Immunomodulator
Glycowithanolides and a mixture of sitoindosides IX and
X isolated from WS were evaluated for their immuno-
modulatory and central nervous system effects (antistress,
memory and learning). Both materials produced statistically
significant mobilisation and activation of peritoneal macro-
phages, phagocytosis and increased activity of the lysosomal
enzymes. Both compounds produced significant antistress
activity in albino mice and rats and augmented learning
acquisition and memory retention in both young and old rats
[63].
2. Tinospora Cordifolia
It is widely used in Ayurvedic medicines and is known
for its immunomodulatory, antihepatotoxic, antistress and
antioxidant properties. It has been used in combination with
other plant products to prepare a number of Ayurvedic
preparations. The chemistry has been extensively studied and
its chemical constituents can be broadly divided into alka-
loids, diterpenoids, steroids, flavanoids and lignans. Reviews
have appeared on quaternary alkaloids and biotherapeutic
diterpene glucosides of Tinospora species. Much of the work
has been carried out on berberine, jatrorrhizine, tinosporaside
and columbin [64]. Extracts of Tinospora cordifolia (TC)
has been shown to inhibit the lipid peroxidation and super-
oxide and hydroxyl radicals in vitro. The extract was also
found to reduce the toxic side effects of cyclophosphamide
(25 mg/kg, 10 days) in mice hematological system by the
free radical formation as seen from total white cell count,
bone marrow cellularity and α-esterase positive cells [65].
Active principles of TC were found to possess anti-comple-
mentary and immunomodulatory activities [66]. TC is
reported for its various immunopharmacological activities
e.g. inhibition of C3-convertase of the classical complement
pathway. Humoral and cell-mediated immunity were
reported for cardioside, cardifolioside A and cardiol and its
activation were more pronounced with increasing incubation
time [67]. Treatment with aqueous, alcohol, acetone and
petroleum ether extracts of stem of TC resulted in significant
improvement in mice swimming time and body weights,
petroleum ether extract showed significant protective effect
against cyclophosphamide-induced immunosuppression.
Prevention of cyclophosphamide-induced anemia was also
reported [67]. Hepatoprotective effects against carbon
tetrachloride induced liver damage have been reported [68].
Tinospora Cordifolia and Radioprotection
Arabinogalactan polysaccharide (TSP) isolated from TC
conferred good protection against iron-mediated lipid
peroxidation of rat brain homogenate as revealed by the
thiobarbituric acid reactive substances (TBARS) and lipid
hydroperoxide (LOOH) assays. TSP also provided signi-
ficant protection to protein against gamma ray induced
damage [69].
Antitumour activity of TC was evaluated in cultured
HeLa cells revealed that the effect of extract was comparable
and better than doxorubicin treatment [70].
Tinospora Cordifolia and Immunomodulation
Syringin, cordiol, cordioside and coriofolioside were
found to possess immunopotentiating activity [65]. The
possible mechanism of immunomodulatory activity was
elucidated as activation of macrophages leading to increase
in GM-CSF, which in turn leads to leukocytosis and
improved neutrophil function [71]. An arabinogalactan has
been isolated from the dried stems of TC showed polyclonal
mitogenic activity against B-cells; their proliferation did not
require macrophages [72].
Tinospora Bakis
A dose dependent cytoprotection by Tinospora bakis; a
plant from Senegalese pharmacopoeia was observed in in
vitro model. Lyophilised aqueous extract of plant roots
decreased intracellular enzyme release (LDH and ASAT)
from CCL4-intoxicated hepatocytes isolated from rats.
Cytoprotective effect was more effective for long course
treatment [73].
3. Asparagus Racemosus
Recent research has shown it to be an immunomodulator
with antioxidant and adaptogenic activities. Chemically
Asparagus racemosus (AR) contains steroidal saponins,
known as shatavarins, isoflavaones, isoflavones including 8-
methoxy-5, 6, 4’-trihydroxyisoflavone 7-O-beta-D-Glucopy-
ranoside, asparagamine, a polycyclic alkaloid, racemosol, a
cyclic hydrocarbon (9, 10-dihydrophenanthrene), polysac-
charides and mucilage. It has been shown to stimulate
macrophages and influence favorably long term adaptation.
Possible links between immunomodulatory and neuro-
pharmacological activity have been suggested. Extracts of
O
O
CH2OH
O
O
H
H
H
H
H
H
OH Withaferin A

8 Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 Diwanay et al.
AR were evaluated for its neuroendocrine immune modulat-
ing effect. It prevents stress-induced increase in plasma
cortisol along with an activation of peritoneal macrophages
and inhibition in gastric vascular damage [74]. A compa-
rative study between AR, TC, glucan and lithium carbonate
against the myelosuppressive effects of single (200 mg/kg,
subcut.) and multiple doses (three doses, 30 mg/kg, i.p.) of
cyclophosphamide in mice revealed all four drugs prevented,
to varying degrees, leucopenia produced by cyclophos-
phamide [75]. Treatment of AR significantly inhibited
Ochratoxin A induced suppression of chemotactic activity
and production of IL-1 and TNF-alpha by macrophages [76].
Our studies on these plants i.e. WS, TC and AR revealed
that these plants have significant immunomodulatory acti-
vity. This activity can be useful in different conditions such
as myeloprotection in cancer chemotherapy or immuno-
protection during infection. We observed that treatment of
ascitic sarcoma bearing mice with formulation of total
extracts of WS and TC and alkaloid free polar extract of WS
resulted in protection towards cyclophosphamide induced
myelo- and immuno-suppression. In another situation, these
plants were evaluated for their immunoadjuvant potential in
pertussis model where aqueous extracts of these plants
reduced the dose of vaccine required to confer protection
against pertussis intracerebral challenge, increasing survival
percentage and significant increase in pertussis antibody
titres. These observations are of major importance in immu-
nochemical industry and vaccination strategies [77, 78].
4. Crocetin
A natural carotenoid, crocetin, at a dose of 50 mg/kg
modulated the release of chloroaceteldehyde; an urotoxic
metabolite of cyclophosphamide in the urine of mice
receiving combined treatment. Crocetin at the same dose
significantly elevated glutathione-S-transferase enzyme
activity both in the bladder and the liver of mice treated with
cyclophosphamide. In Sarcoma-180 tumour bearing mice,
crocetin has the ability to protect against cyclophosphamide
induced bladder toxicity without altering its antitumour
activity [79]. Crocetin also inhibited Benzo(a) pyrene
induced genotoxicity and neoplastic transformation in
C3H10T1/2 cells. Crocetin was found to increase the activity
of GST and decreases the formation of a Benzo(a) Pyrene-
DNA adduct [80].
Berberine
N
O
O
OMe
OMe
I-
+
O
O
O
O
O
H
CH3
CH3
H
Tinosporaside
Glucosyl
O
O
O
H
CH3
CH3
O
O
OH
Columbin
O
O
O
H
CH3
O
H
COOCH3
O
CH2OR
RO OR
OR R=Acyl
Cordifoliside A
O
CH2OR
RO OR
OR R=Acyl
Cordifoliside B
O
O
H
CH3
O
H
COOCH3
O
R=Acyl
O
O
H
CH3
H
O
O
CH3OOC OCH2OR
OR
OR
RO
Cordifolioside C
R=Acyl
O
O
H
CH3
O
O
OH
CH3OOC OCH2OR
OR
OR
RO
Cordioside
O
O
CH3
CH3
O
CH3
Glu
Glu
Glu
Rhamnose Shatavarin

Cytoprotection and Immunomodulation in Cancer Therapy Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 9
5. UL-409
Oral administration of UL-409, a herbal formulation at a
dose of 600 mg/kg significantly prevented the occurrence of
cold-resistant stress induced ulcerations in Wistar rats,
alcohol and aspirin induced gastric ulcerations as well as
cysteamine and histamine induced duodenal ulcers in rats
and guinea pigs, respectively. The volume and acidity of
gastric juice in pyloric-ligated rats was also reduced by UL-
409. It also significantly and dose dependently, promoted
gastric mucus secretion in normal as well as in stress, drug
and alcohol induced ulceration in animals [81].
6. Mikania Cordata
Induction of Phase 2 enzymes is an effective and
sufficient strategy for achieving protection against the toxic
and neoplastic effects of many carcinogens [82]. Literature
reports suggest that chemo preventive action of Mikania
cordata is because of its effect on Phase 2 enzymes. Mikani
cordata oral administration resulted in increased activities of
microsomal uridine diphosphoglucose dehydrogenase,
reduced nicotinamide adenine dinucleotide (phosphate),
quinine reductase and cytosolic glutathione s-transferases
with a concomitant elevation in the contents of reduced
glutathione. Mikania chordata was also found to increase
total protein mass, fractional rate of protein synthesis,
ribosomal capacity and efficiency (rate/ribosome) and high
turnover rate of protein (protein/DNA) on pretreatment in
CCL4 treated hepatic tissue. This indicated the tissue repair
leading to a functional improvement of the CCL4 disorgan-
ised hepatocytes [83]. Oral administration of methanolic
fraction of Mikania cordata (Burm, B. L. Robinson) signifi-
cantly prevented occurrence of water immersion stress-
induced gastric ulcers in a dose-responsive manner. The
extract also dose-dependently inhibited gastric ulcers induced
by ethanol, aspirin and phenylbutazone. The volume, acidity
and peptic activity of the gastric juice in pylorus-ligated rates
were not altered upon administration of the extract but
significantly and dose-dependently promoted gastric mucus
secretion in normal as well as stress- and ethanol-induced
ulcerated animals. It was claimed that, the observed activity
might be due to the modulation of defensive factors through
an improvement of gastric cytoprotection [84].
7. Mistletoe Lectin
Defined, non-toxic doses of the galactoside-specific
mistletoe lectin (mistletoe lectin-I, a constituent of clinically
approved plant extract) have immunomodulatory potencies.
The obvious ability of certain lectins to activate non-specific
mechanisms supports the assumption that, lectin-carbo-
hydrate interactions may induce clinically beneficial immu-
nomodulation. Randomised multicentre trials are being
performed to evaluate the ability of complementary mistletoe
lectin-I treatment to reduce the rate of tumour recurrences
and metastases, to improve overall survival as well as the
quality of life and to exert immunoprotection in cancer
patients under tumour destructive therapy [85].
8. Panax Ginseng
A Korean/Chinese medicine Panax ginseng, (Araliaceae),
employed for its putative medicinal properties in South Asia
stimulated basal natural killer (NK) cell-activity following
sub chronic exposure and helped stimulate recovery of NK
function in cyclophosphamide-immunosuppressed mice but
did not further stimulate NK activity in poly I: C treated
mice, T and B cell responses were not affected. Panax
ginseng provided a degree of protection against infection
with Listeria monocytogenes but did not inhibit growth of
transplanted syngenetic tumour cells. Increased resistance to
L. monocytogenes was not detected in challenged mice
previously given immunosuppressive doses of cyclophos-
phamide. These data suggest that Panax ginseng have some
immunomodulatory properties, primarily associated with NK
cell activity [86]. Ginseng alone, or in combination with
vitamins and minerals, is mainly being promoted as general
tonics, which increases non-specific resistance and
sometimes even as an aphrodisiac. Ginseng on prolonged use
shows a few adverse effects, notable of which is the
‘Ginseng abuse syndrome’ [87].
9. Achyranthes Bidentata
Achyranthes bidentata polysaccharide (ABP), root extract
(25-100 mg/kg, day – 1 to 7), could inhibit tumour growth
(S-180) by 31-40 %. Combination of cyclophosphamide and
ABP increased the rate of tumour growth inhibition by 58%.
ABP could potentiate LAK cell activity and increase the Con
A induced production of tumour necrosis factor (TNF-β)
from murine spleenocytes. The S-180 cell membrane content
of sialic acid was increased and phospholipid decreased after
ABP acting on cells for 24 hours. Data suggest that the
antitumour mechanism of ABP may be related to
potentiation of host immunosurveillance mechanism and the
changes in cell membrane features [88].
10. Viscum Album and Echinacea Purpurea
Extracts of Viscum album (Plenosol) and Echinacea
purpurea (Echinacin) are used clinically for their non-
specific action on cell-mediated immunity. These two were
shown to posses a stimulating effect on the production of
lymphokines by lymphocytes and in the transformation test.
A toxic effect on cells was produced only with very high,
clinically irrelevant concentrations. Clinical application of
these extracts can produce a stimulation of cell-mediated
immunity (one therapeutic administration followed by a free
interval of one week) or can have a depressive action (daily
administration of higher doses). These observations were
confirmed by lymphokine production and 3H thymidine
incorporation assay and a skin test with recall antigens, for at
least 3 months [89].
11. Ocimum Sanctum
Aqueous extract of leaves of Ocimum sanctum was found
to protect from radiation lethality. Pretreatment before
irradiation resulted in increase of spleen colony unit assay as
COOH
HOOC
Crocetin

10 Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 Diwanay et al.
compared to radiotherapy. Extract and radiotherapy in
combination gave higher stem cell survival as compared to
radiotherapy and WR-2721 (WR). WR alone was found
toxic whereas extract showed no such effect suggesting
extract might have advantage over WR in clinical application
[90]. Radio protective effect of the leaf extract of Ocimum
sanctum was studied in combination with WR on mouse
bone marrow. Pretreatment with both in combination resul-
ted in reduction of percent aberrant cells. The extract also
modulated toxicity associated with long-term administration
of WR Significant elevation of chromosome protection was
obtained by combining both [91]. Pretreatment with extract
protects against radiation induced lipid peroxidation. Two
flavanoids - orienten and vicenin isolated from leaves of
Ocimum sanctum showed reduction in aberrations and
showed no systemic toxicity even at 200 mg/kg body weight.
Considering low dose protection and high margin between
effective dose and toxic dose the flavanoids may be
promising for human applications [92].
H. INDIGENOUS HERBAL DRUG FORMULATIONS
AND CHEMOPROTECTION
Brahma Rasayana and Ashwagandha Rasayana were
found to protect mice from cyclophosphamide-induced (50
mg/kg daily for 14 days) myelosuppression and subsequent
leucopenia [93]. Treatment with Asparagus racemosus,
Tinospora cordifolia, Withania somnifera and Picrorhiza
kurrooa significantly inhibited carcinogen ochratoxin A
(OTA)-induced suppression of chemotactic activity and
production of interleukin-1 (IL-1) and tumour necrosis
factor-alpha (TNF-α) by macrophages [75]. Immu-21, poly
herbal formulation that contains extracts of Ocimum
sanctum, Withania somnifera, Emblica officinalis and
Tinospora cordifolia at 100 mg/kg, daily, over 7 days and
30-mg/kg daily over 14 days prevented cyclophosphamide-
induced genotoxicity in mice [94]. Many indigenous herbal
drug formulations have been studied as possible radiopro-
tectants. In one study Cystone – an Ayurvedic herbal formu-
lation when administered intraperitoneally consecutively for
five days resulted in reduction in onset of mortality and
reduced the symptoms of radiation-induced sickness [95].
Similar trends were observed with adminstration of Triphala
- Ayurvedic herbal medicine and Mentat - herbal preparation
when administered consecutively for five days before
irradiation [96, 97]. Radio protective effect was seen with
oral adminstration of Rasayanas. Rasayanas significantly
increased total WBC count, bone marrow cellularity, natural
killer cell and antibody-mediated cytotoxicity in gamma
irradiated mice [98].
I. ANTIOXIDANTS IN CYTOPROTECTION
A number of phytochemicals like Caffeine, Genistein,
Melatonin, Silymarin, Squalene, Glycyrrhizic acid, Plum-
bagin, Eugenol, etc. have multiple physiological effects as
well as antioxidant activity which result in cytoprotection in
vivo. Many antioxidants have additional immunomodulatory
and antimutagenic properties and their modulation of
cytotoxicity needs further examination and evaluation [99,
100].
J. DISCUSSION
Chemoprotection by an immunomodulatory drug is said
to be ideal when it is able to activate immune function
without altering other basic parameters, does not interfere
with antitumour efficacy and thirdly do not add new toxi-
cities that may limit the tolerated doses of chemotherapeutic
agent. In recent years there is an increasing interest in drugs
that are capable of modifying the immune response with few
or no side effects. Most of the current drugs do not fulfill
criteria of ideal chemoprotection. Cytokines are now being
considered as novel immunomodulators however,; they too
exhibit acute and chronic side effects. This has stimulated
interest in exploring natural resources for immunomo-
dulatory activity. Many botanicals have been investigated for
potential adjuvants in cancer therapy and Rasayana drugs
described in Ayurveda provide excellent resource.
Rasayana drugs have been under investigation as possible
immunomodulatory drugs for quite a long time. Several
reports including our studies suggest that treatment with
Rasayana drugs results in protection towards cyclophosph-
amide -induced myelo- and immunoprotection as evident by
significant increase in white cell counts and hemaggluti-
nating and haemolytic antibody titers. However, this
enhancement did not exceed the normal range of respective
cells in peripheral blood that is usually observed with
cytokines and other immunomodulators and no interference
with antitumour efficacy of cyclophosphamide. Thus, it
O
OH
HO
Glu
O
OH
OH
Orienten
O
O
H
COOH
Glucouronic Acid
Glucouronic Acid Glycyrrhizic Acid
OMe
OH
Eugenol
COOH
HO OH O
Plumbagin

Cytoprotection and Immunomodulation in Cancer Therapy Curr. Med. Chem. – Anti-Cancer Agents, 2004, Vol. 4, No. 6 11
qualifies essential characteristics of an ideal chemoprotec-
tion. Moreover, like many of immunomodulators some of
herbs mentioned under Rasayanas are not directly toxic to
tumour cells. However, they are found to have significant
inhibitory effect on ascites tumour development and solid
tumour growth in mice during treatment period. Several
reports indicated that they result in enhanced immune
function via enhancement of NK-cell activity and ADCC in
tumour bearing mice. They have also been reported to
enhance production of cytokines such as IL-2, IFN-gamma
and GM-CSF. These cytokines are not only cytotoxic to
tumour cells but also activate other immune cells such as NK
and T cells that mediate tumour cell cytotoxicity.
Metabolites of active components present in Rasayanas may
also inhibit or interfere with tumour growth and metastasis.
Chemoprofiling of these botanicals have been reported
but most of activity reports are on crude, semi processed
extracts and or fractions. Several reports suggest cytostatic,
cytotoxic properties along with enhanced immune function
in extract and or poly herbal formulations. Nevertheless any
single component isolated from extract or formulation may
not retain all the three desired properties. There have been
attempts to isolate and characterise active moieties with
limited success. Many authors have hypothesised presence of
synergism and buffering in extracts however, systematic
scientific investigations on pharmacodyanmics, kinetics,
dosing and interactions needs to be undertaken to study these
principles. Furthermore studies are required to better
understand the molecular and biochemical mechanisms
involved in immunoregulation and its role in cytoprotection
and radioprotection [6]. Such efforts might lead to effective
integration of botanical medicine in cancer therapy.
Many molecular mechanisms and targets have been
identified for modulation of radiation response with the
advancement in understanding of tumour cell biology. Some
important ones are COX-II, MMPs, TRAIL (TNF-related
apoptosis inducing ligand)/Apo2L, epidermal growth factor
receptor (EGFR), etc [101-103]. Natural compounds may
have an advantage, being structurally diverse and safer11].
CONCLUSION
Many chemical agents are used as cytoprotectants for
conventional cancer chemotherapy and/or radiation therapy.
However, their effects are locoregional that are dependent on
dose and time of administration in context to anticancer
drugs. Such therapeutic limitations have stimulated research
for discovering natural resources with immunological
activity. Various botanicals and ethnopharmacological
agents such as Rasayanas showing promises in cancer
treatment are reviewed here for their chemoprotective and
immunomodulatory activities. This review will be useful in
the bioprospecting exercises for developing newer, safer and
effective agents for therapeutic management of cancer.
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