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Thymoquinone Anticancer Discovery: Possible Mechanisms
Abstract and Figures
Medicinal plants are noted for their many advantages, including the ability to treat diseases such as cancer. Nigella sativa and its active constituent thymoquinone (TQ) have long been used in traditional medicine for treating various conditions related to the respiratory and gastrointestinal systems as well as breast, colorectal, gastric, hepatic, pancreatic cancers and leukemia. TQ has been documented to possess chemo-preventive and chemotherapeutic antitumor effects. Studies reported that TQ inhibits the growth of cancer cells in animal models and culture tumors. This review summarizes the in vitro and in vivo possible mechanisms of TQ anticancer effect.
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... In particular, it has been demonstrated that various concentrations of quercetin, significantly inhibit tumor growth of various cancer cell lines, including breast, colorectal, stomach, head and neck, lung, ovarian, melanoma and leukemia [10,11]. Thymoquinone is the major active component present in the raw extracts of the Nigella sativa Linn seeds [12]. Anti-proliferative and pro-apoptotic features of thymoquinone have also been recognized in multiple cancer cell lines such as the human colon carcinoma, ovarian adenocarcinoma cells, breast adenocarcinoma and canine osteosarcoma cells [12]. ...
... Thymoquinone is the major active component present in the raw extracts of the Nigella sativa Linn seeds [12]. Anti-proliferative and pro-apoptotic features of thymoquinone have also been recognized in multiple cancer cell lines such as the human colon carcinoma, ovarian adenocarcinoma cells, breast adenocarcinoma and canine osteosarcoma cells [12]. Also, some of the recent studies have reported that quercetin and thymoquinone are important inducing factors of DDR, and inhibits the proliferation of cancer cells by inducing DNA damage and decreasing the potential of DNA repair machinery [13,14]. ...
Background
The recent decade has witnessed the increasing potential of various flavonoids such as quercetin and thymoquinone in inhibiting cancer cells proliferation and growth and their therapeutic effects in various cancers. Therefore, in the current study, we aim to evaluate the expression levels of key factors of DNA damage response in human breast, lung and prostate cancer cell lines in response to treatment with quercetin and thymoquinone.
Methods
MTT assay was applied to assess the effects of quercetin and thymoquinone on the viability of MCF-7, A549, and PC3 cancer cells. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to evaluate the expression levels of p53, RAD51, Ku70, XRCC1, and H2AX in treated cells. In addition, the expression rate of 8-hydroxy-deoxyguanosine (8-OH-dG) was assessed by ELISA kit.
Results
The quercetin and thymoquinone induce cytotoxicity in breast, lung, and prostate cancer cells effectively; MCF-7 cells were the most sensitive cells to quercetin with an IC50 value of 50 μM and PC3 cells were more sensitive to thymoquinone with an IC50 value of 20 μM. The expression levels of DNA damage markers, H2AX, and 8-OH-dG were significantly increased in all cancer cells treated with quercetin and thymoquinone (p<0.05). Moreover, both flavonoids significantly decreased the expression levels of DNA repair mediators, RAD51, Ku70, XRCC1, in cell lines. P53 was also increased in MCF-7 and A549 cells.
Conclusion
We concluded that quercetin and thymoquinone may exert their effects through modulation of DNA damage response, increasing DNA damage, and suppressing DNA repair genes.
... TQ is a commonly safe constituent, particularly when given orally to laboratory animals 3 . TQ has been shown to have different pharmacological actions, including anti-inflammatory, immunomodulatory, anti-diabetic, antioxidant, anticancer, and anti-aging properties [4][5][6][7][8][9][10][11][12][13][14][15] . Previous research has shown that TQ has a substantial antioxidant effect against a variety of free radical-producing chemicals, including diabetes-induced testicular atrophy 10 and cardiac 11 alterations, cisplatin-induced hepato-toxicity, doxorubicin-induced cardiotoxicity, and cadmiuminduced reproductive dysfunctions 16,17 . ...
Diabetes mellitus (DM) is a complex metabolic condition that causes organ dysfunction. The current experiment sought to determine the effect of thymoquinone (TQ) on hyperglycemia, hyperlipidemia, oxidative/nitrosative stress, inflammation, and apoptosis in diabetic rats prompted by streptozotocin (STZ) (55 mg/kg body weight i/p). The animals were allocated into control, TQ (50 mg/kg B.W. orally administered for 4 succeeding weeks), Diabetic, and Diabetic + TQ groups. This study confirmed that TQ preserves the levels of insulin, fasting blood glucose, HOMA β-cell indices, HbA1c %, body weight, and lipid profile substantially relative to the DC group. Furthermore, hepatic antioxidant (CAT, GSH, and T-SOD) values were reduced. Conversely, the enzymatic activity of liver functions (AST, ALT, ALP, cytochrome P450, and hepatic glucose-6-phosphatase), lipid peroxidation (MDA), pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6), nitric oxide (NO) and inflammatory marker (CRP) enhanced with STZ administration, which is substantially restored after TQ treatment. Relative to the diabetic rats, TQ reestablished the hepatic architectural changes and collagen fibers. Additionally, TQ downregulated the intensity of the immunohistochemical staining of pro-apoptotic marker (caspase-3), p53, and tumor necrosis factor-alpha (TNF-α) proteins in hepatic tissues. Furthermore, TQ displayed abilities to interact and inhibit the binding site of caspase-3, interleukin-6 receptor, interleukin-1 receptor type 1, TNF receptor superfamily member 1A, and TNF receptor superfamily member 1B in rats following the molecular docking modeling. All these data re-establish the liver functions, antioxidant enzymes, anti-inflammatory markers, and anti-apoptotic proteins impacts of TQ in STZ-induced DM rats. Founded on these outcomes, the experiment proposes that TQ is a novel natural supplement with various clinical applications, including managing DM, which in turn is recommended to play a pivotal role in preventing the progression of diabetes mellitus.
... Thymoquinone (TQ) is a major bioactive constituent of the black seed (Nigella sativa) [15], it has shown different anticancer activities through cell proliferation inhibition, and apoptosis induction in cancer cells, the possible mechanisms of TQ anticancer activity against various proliferative cancer cells were summarized in the review article by El-Far [16]. Interestingly, TQ was reported to have a significant selectivity against various malignant cells [17][18][19][20][21]. ...
... Thymoquinone (TQ) is a major bioactive constituent of the black seed (Nigella sativa) [15], it has shown different anticancer activities through cell proliferation inhibition, and apoptosis induction in cancer cells, the possible mechanisms of TQ anticancer activity against various proliferative cancer cells were summarized in the review article by El-Far [16]. Interestingly, TQ was reported to have a significant selectivity against various malignant cells [17][18][19][20][21]. ...
Background
Traditional herbal medicine has been used for centuries to cure many pathological disorders, including cancer. Thymoquinone (TQ) and piperine (PIP) are major bioactive constituents of the black seed (Nigella sativa) and black pepper (Piper nigrum), respectively. The current study aimed to explore the potential chemo-modulatory effects, mechanisms of action, molecular targets, and binding interactions after TQ and PIP treatments and their combination with sorafenib (SOR) against human triple-negative breast cancer (MDA-MB-231) and liver cancer (HepG2) cells.
Methods
We determined drug cytotoxicity by MTT assay, cell cycle, and death mechanism by flow cytometry. Besides, the potential effect of TQ, PIP, and SOR treatment on genome methylation and acetylation by determination of DNA methyltransferase (DNMT3B), histone deacetylase (HDAC3) and miRNA-29c expression levels. Finally, a molecular docking study was performed to propose potential mechanisms of action and binding affinity of TQ, PIP, and SOR with DNMT3B and HDAC3.
Results
Collectively, our data show that combinations of TQ and/or PIP with SOR have significantly enhanced the SOR anti-proliferative and cytotoxic effects depending on the dose and cell line by enhancing G2/M phase arrest, inducing apoptosis, downregulation of DNMT3B and HDAC3 expression and upregulation of the tumor suppressor, miRNA-29c. Finally, the molecular docking study has identified strong interactions between SOR, PIP, and TQ with DNMT3B and HDAC3, inhibiting their normal oncogenic activities and leading to growth arrest and cell death.
Conclusion
This study reported TQ and PIP as enhancers of the antiproliferative and cytotoxic effects of SOR and addressed the mechanisms, and identified molecular targets involved in their action.
... It exhibits pleiotropic activity including anti-inflammatory, antihistaminic, antihypertensive, hypoglycemic, immune enhancement, and antiarthritic [3,4]. Furthermore, it has anticancer and antioxidant actions in various types of cancers such as breast, bone, cervix, liver, colon, blood, oral, head and neck, prostate, kidney, and bladder [5][6][7]. ...
The effects of thymoquinone (TQ) in a carcinogen-based models of urinary bladder cancer were evaluated, using 45 male rats in five groups. In negative control ( n = 10 ), only tap water was given. In positive control ( n = 10 ), the rats received 0.05% N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) in drinking water for 9 weeks. In preventive groups with 25 mg/kg ( n = 10 ) and 50 mg/kg ( n = 10 ), oral TQ was concurrently given with 0.05% BBN for 9 weeks and continued for one more week after cessation of BBN. Preventive-treatment group ( n = 5 ) received 50 mg/kg TQ orally for 20 weeks. Five rats from each group were sequentially sacrificed in two phases: the induction phase at 12th week (except the last group) and the rest in postinduction phase at 20th week. The bladders were examined macroscopically for lesion formation, and the masses were submitted for histopathological evaluation. Markers for total oxidant status (TOS), inflammation (nuclear factor kappa B (NF-κB)), and angiogenesis (vascular endothelial growth factor (VEGF)) were also assessed. There was a reduced number of bladder lesions in the TQ groups versus the carcinogen group at both phases. Histopathological findings demonstrated a significant improvement in the abnormal morphological changes in the urothelium of the TQ-treated groups. Thymoquinone exerted a significant antioxidant and anti-inflammatory effect by a decrease in serum level of TOS and NF-κB at week 12 which was maintained low in phase two at week 20. The serum level of VEGF was also alleviated in the induction phase at week 12 and maintained low in postinduction period. In TQ preventive-treatment approach, a nonsignificant elevation of serum level of TOS and NF-κB and slight reduction in VEGF were observed at the end of the experiment. These data suggest that TQ may be effective in preventing bladder carcinogenesis, and the suggested mechanisms might be related to antioxidant, prooxidant, and anti-inflammatory properties of TQ.
Cardiovascular conditions such as coronary artery disease, stroke, vascular disease, and heart failure are made more likely to occur by hypertension. Hypertension doesn't typically present with symptoms until it has progressed, but it can cause serious, lifelong health problems. The cost of and potential side effects from antihypertensive drugs are concerns. As a result, in the current environment, it is essential to investigate the therapeutic potential of herbal medications with minimal side effects. It is well known that Nigella sativa and its active components, including thymoquinone, thymol, and nigericin, are potential phytomedicines with anti-inflammatory, hypotensive, calcium channel blocker, and diuretic properties that significantly lower blood pressure.In this review, the chemical makeup, pharmacological effects, and antihypertensive properties of N. sativa are reviewed with particular focus on thimoquinone, and its nanoformulations & health benefits.This review highlighted the health benefits of N. sativa, which exhibits less toxicity at higher doses in animals, and L-blood NAME's pressure-raising effect is attenuated by its essential oil at a dose. Also, many nanotechnological formulaions are being used for the encapsulation of thymoquinone. Nano-TQ significantly enhances the anticancer effects of doxorubicin and increases the effects of paclitaxel by upregulating P53 and downregulating Bcl2. This review further provided the effectiveness of nanoparticles in lowering blood pressure and suggests combining them with N. sativa or thymoquinone to increase their antihypertensive effects.This study concluded the potential ofN. sativa as a antihypertensive agent. Thimoquinone, a major component in N. sativa is extensively studied and nanofromulated bioactive compound that can be used in many agri-food-pharma industries.
Gastric cancer (GC) is a serious global health concern. GC is a form of cancer that advances through the stomach lining. Therefore, there is a need to explore novel preventive strategies for GC. A novel study indicated that plant-derived compounds have significant anticancer characteristics and may provide a novel therapeutic approach for GC. Recent research has highlighted the potential role of natural compounds, particularly phytocompounds, in preventing GC. Compounds, such as curcumin, resveratrol, and epigallocatechin gallate, have significant anticancer properties against GC. The primary purpose of this study was to investigate the preventive properties of the phytocompounds against GC. The experimental findings included both in vitro and in vivo studies, clinical trials, and epidemiological investigations, providing a comprehensive evaluation of the potential impact of compounds on GC prevention. This review also provides a detailed overview of the probable medicinal effects of phytocompounds on the avoidance and treatment of GC, considering their complex molecular mechanisms of action, bioavailability, and safety. This study provides new perspectives on the possible significance of compounds in GC treatment and emphasizes their promise as a cutting-edge approach to anti-cancer methods.
Objective
Diabetic nephropathy is an unavoidable complication of chronic uncontrolled diabetes mellitus. The pathogenesis of diabetic nephropathy is multifactorial, and the development of an effective therapy remains to be elucidated. The aim of the present study was to assess the role of NOX2 and Nrf2 in the protective mechanism of thymoquinone (THQ) against streptozotocin (STZ)-induced diabetic nephropathy.
Methods
Rats were injected with STZ (55 mg/kg) to induce diabetes. The diabetic rats were orally treated with THQ (10 mg/kg/day) for eight weeks.
Results
STZ-treated rats exhibit an elevation of serum creatinine, serum urea, and creatinine clearance. The renal abnormalities were associated with increased NADPH oxidase isoform, NOX2 protein expression, and activity, along with elevated malondialdehyde (MDA). In addition, the tumor necrotic factor-alpha (TNF-α) level and nitric oxide (NO) bioavailability, as well as the transforming growth factor-beta (TGF)-β, were markedly increased. On the other hand, the nuclear factor-E2-related factor (Nrf2) protein expression was significantly reduced in diabetic rats compared to the control. However, treatment with THQ significantly reversed these alterations with subsequent ameliorating renal dysfunction and pathological abnormalities.
Conclusion
The present study demonstrates that THQ could protect against STZ-induced diabetic nephropathy by modulating the Nrf2/NOX2 signaling pathway.
There are many studies in the literature on thymoquinone (TQ)-related cancer cells and models, and there is no relevant study investigating the efficacy of the oxime derivative of TQ (TQ-Ox). This study synthesized TQ-Ox and examined its cytotoxic, genotoxic and apoptotic properties in ovarian cancer cells. The structure TQ-Ox was confirmed with NMR. The cytotoxicity by luminometric ATP, intracellular reactive oxygen species (iROS) by fluorometric, intracellular calcium (iCa²⁺) by fluorometric, mitochondrial membrane potential (MMP) by flow cytometry, glutathione (GSH) levels with GSH/GSSG-Glo assay, DNA damage by comet assay, and apoptosis by acridine orange/ethidium bromide dye were determined. Concentrations of TQ-Ox were statistically increased cytotoxicity, DNA damage, apoptosis, iROS, and iCa²⁺ in a concentration-dependent manner (p < 0.001). Besides, MMP and GSH levels also decreased statistically significantly (p < 0.001) with increasing concentrations. TQ-Ox would be an effective treatment option by increasing cytotoxicity, genotoxicity, and apoptosis in ovarian carcinoma.
Cancer is a challenging ailment and represents the main reason for death worldwide for humans and animals. Although great developments have hindered cancer progression, several adverse effects are associated with modern chemotherapy. Natural remedies, such as the usage of medicinal plant or their products in cancer treatment, may decrease prejudicial side properties. Recently, the modern research scheme and innovative screening practices for herbs or plants have enabled phytochemical discovery for the prevention and treatment of cancer. This criticism highlights herbs such as acacia, basil, black seeds, cedar, castus, ficus, garlic, ginger, indigo, onion, pomegranate, quince, and thyme, promising anticancer effects. The present review also revealed the mode of action of each herb as anticancer effects at level in vitro and in vivo studies. The item also totalizes the vital mechanisms and signaling molecules involved in preventing cancer diseases. This will fill the investigate gap in the exploration of using natural molecules and encourage researchers in clinical trials of anticancer agents from herbs for humans and animals.
Thymoquinone (TQ), a component of black seed essential oil, is known to induce apoptotic cell death and oxidative stress, however, the direct involvement of oxidants in TQ-induced cell death has not been established yet. Here, we show that TQ inhibited the proliferation of a panel of human colon cancer cells (Caco-2, HCT-116, LoVo, DLD-1 and HT-29), without exhibiting cytotoxicity to normal human intestinal FHs74Int cells. Further investigation in DLD-1 revealed that apoptotic cell death is the mechanism for TQ-induced growth inhibition as confirmed by flow cytometry, M30 cytodeath and caspase-3/7 activation. Apoptosis was induced via the generation of reactive oxygen species (ROS) as evidenced by the abrogation of TQ apoptotic effect in cells preincubated with the strong antioxidant N-acetyl cysteine (NAC). TQ increased the phosphorylation states of the mitogen-activated protein kinases (MAPK) JNK and ERK, but not of p38. Their activation was completely abolished in the presence of NAC. Using PD98059 and SP600125, specific ERK and JNK inhibitors, the two kinases were found to possess pro-survival activities in TQ-induced cell death. These data present evidence linking the pro-oxidant effects of TQ with its apoptotic effects in colon cancer and prove a protective role of MAPK.
Tumor suppressor p53 has recently been reported to have numerous functions independent of tumorigenesis, including neuronal survival during ischemia. The mammalian target of rapamycin (mTOR) signaling pathway plays a central role in the regulation of metabolism, cell growth, development, and cell survival. Our recent work has demonstrated the neuroprotective effects of the mTOR pathway. Considering that p53 is also an important regulator of mTOR, to further clarify the role of p53 and the mTOR signaling pathway in neuronal ischemic-reperfusion injury, we used mouse primary mixed cultured neurons with an oxygen glucose deprivation (OGD) model to mimic an ischemic-reperfusion injury in vitro. A lentiviral system was also used to inhibit or overexpress p53 to determine whether p53 alteration affects OGD and reperfusion injury. Our results show that activated p53 was induced and it suppressed mTOR expression in primary mixed cultured neurons after OGD and reperfusion. Inhibiting p53, using either a chemical inhibitor or lentiviral-mediated shRNA, exhibited neuroprotective effects in primary cultured neurons against OGD and reperfusion injury through the upregulation of mTOR activity. Such protective effects could be reversed by rapamycin, an mTOR inhibitor. Conversely, p53 overexpression tended to exacerbate the detrimental effects of OGD injury by downregulating mTOR activity. These results suggest that p53 inhibition has a pivotal protective effect against an in vitro ischemia-reperfusion injury via mTOR signaling and provides a potential and promising therapeutic target for stroke treatment.
Copyright © 2015. Published by Elsevier B.V.
Thymoquinone (TQ), an active ingredient of black seed oil (Nigella Sativa), has been shown to possess cytotoxic activity against a variety of cancer cell lines. Our purpose was to investigate if the cytotoxic and apoptotic effect of zoledronic acid (ZA) can be enhanced by the addition of the TQ in hormone- and drug-refractory prostate cancer cells PC-3 and DU-145.
XTT cell proliferation assay was used to assess cytotoxicity; DNA fragmentation and caspase 3/7 activity were also measured.
The combination of TQ and ZA resulted in a significant synergistic cytotoxic activity and DNA fragmentation when compared to any single agent alone, in a dose- and time-dependent manner. In addition, TQ and ZA combination increased the caspase 3/7 activity in PC-3 cell line, while this activity could not be demonstrated in DU-145 cell line.
TQ and ZA had minimal hematological and non-hematological toxicity profile compared to cytotoxic agents. So, this combination may be an alternative approach for patients who are unable to be treated by conventional treatments because of poor performance status.
Purpose: Thymoquinone (TQ), an active ingredient of black seed oil (Nigella Sativa), has been shown to possess cytotoxic activity against a variety of cancer cell lines. Our purpose was to investigate if the cytotoxic and apoptotic effect of zoledronic acid (ZA) can be enhanced by the addition of the TQ in hormone- and drug-refractory prostate cancer cells PC-3 and DU-145. Methods: XTT cell proliferation assay was used to assess cytotoxicity; DNA fragmentation and caspase 3/7 activity were also measured. Results: The combination of TQ and ZA resulted in a significant synergistic cytotoxic activity and DN A fragmentation when compared to any single agent alone, in a dose- and time-dependent manner. In addition, TQ and ZA combination increased the caspase 3/7 activity in PC-3 cell line, while this activity could not be demonstrated in DU-145 cell line. Conclusion: TQ and ZA had minimal hematological and non-hematological toxicity profile compared to cytotoxic agents. So, this combination may be an alternative approach for patients who are unable to be treated by conventional treatments because of poor performance status.
Cell cycle regulates proliferative cell capacity under normal or pathologic conditions, and in general it governs all in vivo/in vitro cell growth and proliferation processes. Mathematical simulation by means of reliable and predictive models represents an important tool to interpret experiment results, to facilitate the definition of the optimal operating conditions for in vitro cultivation, or to predict the effect of a specific drug in normal/pathologic mammalian cells. Along these lines, a novel model of cell cycle progression is proposed in this work. Specifically, it is based on a population balance (PB) approach that allows one to quantitatively describe cell cycle progression through the different phases experienced by each cell of the entire population during its own life. The transition between two consecutive cell cycle phases is simulated by taking advantage of the biochemical kinetic model developed by Gérard and Goldbeter (2009) which involves cyclin-dependent kinases (CDKs) whose regulation is achieved through a variety of mechanisms that include association with cyclins and protein inhibitors, phosphorylation-dephosphorylation, and cyclin synthesis or degradation. This biochemical model properly describes the entire cell cycle of mammalian cells by maintaining a sufficient level of detail useful to identify check point for transition and to estimate phase duration required by PB. Specific examples are discussed to illustrate the ability of the proposed model to simulate the effect of drugs for in vitro trials of interest in oncology, regenerative medicine and tissue engineering.
Topotecan has shown promising antineoplastic activity in solid tumors and acute leukemia. Because of the primary dose-limiting toxicity of topotecan, it is necessary to identify other agents that can work synergistically with topotecan, potentially increasing its efficacy while limiting its toxicity. Many studies showed synergism in combination of topotecan with gemcitabine and bortezomib. Other studies report the increase in growth inhibition of gemcitabine or oxaliplatin when cells were preexposed to naturally occurring drugs such as thymoquinone. The aim of this project was to study the mode of action of topotecan along with thymoquinone, on survival and apoptosis pathways in acute myelogenous leukemia (AML) cell lines, and to investigate the potential synergistic effect of thymoquinone on topotecan.
U937 cells were incubated with different topotecan and thymoquinone concentrations for 24 and 48 hours, separately and in combination. Cell proliferation was determined using WST-1 (Roche) reagent. The effect of the compounds on protein expression of Bax, Bcl2, p53, caspase-9, -8, and -3 was determined using Western blot analysis. Cell cycle analysis was performed in addition to annexin/propidium iodide staining.
Thymoquinone and topotecan exhibited antiproliferative effects on U937 cells when applied separately. In combination, the reduction in proliferation was extremely significant with a major increase in the expression levels of Bax/Bcl2, p53, and caspase-3 and -9. Preexposure with thymoquinone resulted in an increase in cell growth inhibition compared with topotecan treatment.
Thymoquinone, when combined with topotecan in noncytotoxic doses, produced synergistic antiproliferative and proapoptotic effects in AML cells. Preexposure to thymoquinone seems to be more effective than simultaneous application with topotecan.
Copyright © 2014 Elsevier Inc. All rights reserved.
Background:
Thymoquinone (TQ) has been documented to possess chemo-preventive and chemotherapeutic antitumor effects. Studies reported that TQ inhibits the growth of cancer cells in animal models, culture and xenografted tumors. Molecular mechanisms underlying these anticancer effects were attributed to inductions of cell cycle arrest, apoptosis, oxidative damage of cellular macromolecules, blockade of tumor angiogenesis and inhibitions in migration, invasion and metastasis of cancer cells. On the other hand, human telomere DNA plays a role in regulating genes' transcriptions. It folds up into G-quadruplex structures that inhibit telomerase enzyme over-expressed in cancerous cells. Molecules that selectively stabilize G-quadruplex are potential anticancer agents. Therefore, this work aimed to explore the interaction of TQ with G-quadruplex DNA as a possible underlying mechanism for the anticancer effect of TQ.
Methods:
Interactions of TQ with telomeric G-quadruplex (5'-AGGG(TTAGGG)3-3') and duplex DNAs were studied using UV-vis, fluorescence, circular dichroism, liquid and solid NMR (1H and 13C), melting temperature and docking simulation.
Results:
Changes in UV-vis, CD, fluorescence, 1H NMR and 13C NMR, spectra as well as melting temperatures and docking simulations provided evidences for TQ's interactions with G-quadruplex. TQ was found to interact with G-quadruplex on two binding sites adjacent to the TTA loop with binding constants 1.80×10(5) and 1.12×10(7) M(-1). Melting temperatures indicated that TQ stabilized G-quadruplex by 5.6 °C and destabilized ct-DNA by 5.1 °C. Selectivity experiment indicated that TQ is preferentially binding to G-quadruplex over duplex with selectivity coefficients of 2.80-3.33×10(-3). Results suggested an intercalation binding mode based on π-π stacking.
Conclusion:
Our results propose that TQ can possibly act as a G-quadruplex DNA stabilizer and subsequently contribute to the inhibition of telomerase enzyme and cancer's proliferation.
General significance:
Our results represent a change in the paradigms reported for structural features of G-quadruplex's stabilizers and anticancer mechanisms of TQ.
DBC1 is a major inhibitor of SIRT1, which plays critical roles in the control of diverse cellular processes, including stress response and energy metabolism. Therefore, the DBC1-SIRT1 interaction should finely be regulated. Here we report that DBC1 modification by Small Ubiquitin-like Modifier 2/3 (SUMO 2/3), but not by SUMO1, is crucial for p53 transactivation under genotoxic stress. Whereas etoposide treatment reduced the interaction of DBC1 with SENP1, it promoted that with PIAS3, resulting in an increase in DBC1 sumoylation. Remarkably, the switching from SENP1 to PIAS3 for DBC1 binding was achieved by ATM/ATR-mediated phosphorylation of DBC1. Furthermore, DBC1 sumoylation caused an increase in the DBC1-SIRT1 interaction, leading to the release of p53 from SIRT1 for transcriptional activation. Consistently, SENP1 knockdown promoted etoposide-induced apoptosis, whereas knockdown of PIAS3 or SUMO2/3 and overexpression of sumoylation-deficient DBC1 mutant inhibited it. These results establish the role of DBC1 sumoylation in the promotion of p53-mediated apoptosis in response to genotoxic stress.