Resveratrol chemosensitizes breast cancer cells to melphalan by cell cycle arrest

Oxyresveratrol in Breast Cancer Cells: Synergistic Effect with Chemotherapeutics Doxorubicin or Melphalan on Proliferation, Cell Cycle Arrest, and Cell Death

Breast cancer is the second most common type of cancer in the world. Polyphenols can act at all stages of carcinogenesis and oxyresveratrol (OXY) promising anticancer properties, mainly associated with chemotherapy drugs. The aim of this study was to investigate the effect of OXY with doxorubicin (DOX) or melphalan (MEL), either isolated or associated, in MCF-7 and MDA-MB-231 breast cancer cells. Our results showed that OXY, DOX, and MEL presented cytotoxicity, in addition to altering cell morphology. The synergistic association of OXY + DOX and OXY + MEL reduced the cell viability in a dose-dependent manner. The OXY, DOX, or MEL and associations were able to alter the ROS production, ∆Ψm, and cell cycle; DOX and OXY + DOX led the cells to necrosis. Furthermore, OXY and OXY + MEL were able to lead the cells to apoptosis and upregulate caspases-3, -7, -8, and -9 in both cells. LC-HRMS showed that 7-deoxidoxorubicinone and doxorubicinol, responsible for the cardiotoxic effect, were not identified in cells treated with the OXY + DOX association. In summary, our results demonstrate for the first time the synergistic effect of OXY with chemotherapeutic agents in breast cancer cells, offering a new strategy for future animal studies.

Curcumin and melphalan cotreatment induces cell cycle arrest and apoptosis in MDA-MB-231 breast cancer cells

Breast cancer is the second most common type of cancer worldwide and the leading cause of cancer death in women. Dietary bioactive compounds may act at different stages of carcinogenesis, including tumor initiation, promotion, and progression. Spices have been used for thousands of years and have many bioactive compounds with chemopreventive and chemotherapeutic properties. Curcumin has a multitude of beneficial biological properties, including anti-inflammatory and anticancer effects. This study investigated the effects of cotreatment with curcumin and the chemotherapeutic drug melphalan in cultured MDA-MB-231 breast cancer cells. When used alone, both curcumin and melphalan had a cytotoxic effect on breast cancer cells. Combined treatment with 11.65 µM of curcumin and 93.95 µM of melphalan (CURC/MEL) reduced cell viability by 28.64% and 72.43% after 24 h and 48 h, respectively. CURC/MEL reduced the number of colony-forming units and increased ROS levels by 1.36-fold. CURC/MEL alter cell cycle progression, induce apoptosis, and upregulate caspases-3, -7, and -9, in MDA-MB-231 cells. Cotreatment with curcumin and melphalan have anti-breast cancer cells effects and represent a promising candidate for clinical testing.

Hypoxia, but Not Normoxia, Reduces Effects of Resveratrol on Cisplatin Treatment in A2780 Ovarian Cancer Cells: A Challenge for Resveratrol Use in Anticancer Adjuvant Cisplatin Therapy

Natural compounds, such as resveratrol (Res), are currently used as adjuvants for anticancer therapies. To evaluate the effectiveness of Res for the treatment of ovarian cancer (OC), we screened the response of various OC cell lines to the combined treatment with cisplatin (CisPt) and Res. We identified A2780 cells as the most synergistically responding, thus optimal for further analysis. Because hypoxia is the hallmark of the solid tumor microenvironment, we compared the effects of Res alone and in combination with CisPt in hypoxia (pO2 = 1%) vs. normoxia (pO2 = 19%). Hypoxia caused an increase (43.2 vs. 5.0%) in apoptosis and necrosis (14.2 vs. 2.5%), reactive oxygen species production, pro-angiogenic HIF-1α (hypoxia-inducible factor-1α) and VEGF (vascular endothelial growth factor), cell migration, and downregulated the expression of ZO1 (zonula occludens-1) protein in comparison to normoxia. Res was not cytotoxic under hypoxia in contrast to normoxia. In normoxia, Res alone or CisPt+Res caused apoptosis via caspase-3 cleavage and BAX, while in hypoxia, it reduced the accumulation of A2780 cells in the G2/M phase. CisPt+Res increased levels of vimentin under normoxia and upregulated SNAI1 expression under hypoxia. Thus, various effects of Res or CisPt+Res on A2780 cells observed in normoxia are eliminated or diminished in hypoxia. These findings indicate the limitations in using Res as an adjuvant with CisPt therapy in OC.

Potential Therapeutic Targets of Resveratrol, a Plant Polyphenol, and Its Role in the Therapy of Various Types of Cancer

Cancer is among the most prominent causes of mortality worldwide. Different cancer therapy modes employed, including chemotherapy and radiotherapy, have been reported to be significant in cancer management, but the side effects associated with these treatment strategies are still a health problem. Therefore, alternative anticancer drugs based on medicinal plants or their active compounds have been generating attention because of their less serious side effects. Medicinal plants are an excellent source of phytochemicals that have been recognized to have health-prompting effects through modulating cell signaling pathways. Resveratrol is a well-known polyphenolic molecule with antioxidant, anti-inflammatory, and health-prompting effects among which its anticancer role has been best defined. Additionally, this polyphenol has confirmed its role in cancer management because it activates tumor suppressor genes, suppresses cell proliferation, induces apoptosis, inhibits angiogenesis, and modulates several other cell signaling molecules. The anticancer potential of resveratrol is recognized in numerous in vivo and in vitro studies. Previous experimental data suggested that resveratrol may be valuable in cancer management or improve the efficacy of drugs when given with anticancer drugs. This review emphasizes the potential role of resveratrol as an anticancer drug by modulating numerous cells signaling pathways in different types of cancer.

Natural Small Molecules in Breast Cancer Treatment: Understandings from a Therapeutic Viewpoint

Breast cancer (BrCa) is the most common malignancy in women and the second most significant cause of death from cancer. BrCa is one of the most challenging malignancies to treat, and it accounts for a large percentage of cancer-related deaths. The number of cases requiring more effective BrCa therapy has increased dramatically. Scientists are looking for more productive agents, such as organic combinations, for BrCa prevention and treatment because most chemotherapeutic agents are linked to cancer metastasis, the resistance of the drugs, and side effects. Natural compounds produced by living organisms promote apoptosis and inhibit metastasis, slowing the spread of cancer. As a result, these compounds may delay the spread of BrCa, enhancing survival rates and reducing the number of deaths caused by BrCa. Several natural compounds inhibit BrCa production while lowering cancer cell proliferation and triggering cell death. Natural compounds, in addition to therapeutic approaches, are efficient and potential agents for treating BrCa. This review highlights the natural compounds demonstrated in various studies to have anticancer properties in BrCa cells. Future research into biological anti-BrCa agents may pave the way for a new era in BrCa treatment, with natural anti-BrCa drugs playing a key role in improving BrCa patient survival rates.

Calorie Restriction for Cancer Prevention and Therapy: Mechanisms, Expectations, and Efficacy

Cancer is one of the most frequently diagnosed diseases, and despite the continuous efforts in searching for new and more effective treatments, its morbidity and mortality remain a significant health problem worldwide. Calorie restriction, a dietary manipulation that consists in a reduction of the calorie intake, is gaining attention as a potential adjuvant intervention for preventing and/or fighting cancer. Several forms of energy reduction intake, which includes caloric restriction tout-court, dietary restrictions, and intermittent fasting, are being explored for their ability to prevent or slow down cancer progression. Additionally, another anti-cancer approach being under investigation relies on the use of nutraceuticals known as “Caloric Restriction Mimetics” that can provide caloric restriction-mediated benefits without subjecting the patients to a strict diet. Preclinical in vitro and in vivo studies consistently show that diet modifiers reducing the calorie have impact on tumor microenvironment and cancer metabolism, resulting in reduced growth and progression of cancer. Preliminary clinical studies show that patients subjected to a reduced nutrient/energy intake experience improved outcomes from chemo- and radiotherapy while better tolerating the side effects. Here, we review the state of the art on the therapeutic potential of calorie restriction and of caloric restriction mimetics in preventing or retarding tumor development by modulating a subset of cellular processes. The most recent clinical progresses with caloric restriction mimetics in the clinical practice are also discussed.

Integrative investigation of the TF-miRNA coregulatory network involved in the inhibition of breast cancer cell proliferation by resveratrol

Resveratrol is a polyphenol with antiaging and anticancer effects. Most previous studies used a single analysis to determine the key functions of resveratrol in inhibiting cancer progression. However, most of the signal transmission pathways in biological processes are multilevel. We used bioinformatics to elucidate the mechanism of resveratrol inhibition of breast cancer development. The mRNA expression profile of GSE25412 from the National Center for Biotechnology Information (NCBI) and the microRNA (miRNA) expression profile of PubMed identifier (PMID) 26890143 were integrated. De novo motifs were used to obtain predicted transcription factor (TF) motifs for differentially expressed genes. The regulatory effect of resveratrol on key nodes in the comprehensive analysis results was verified. The TF–miRNA–mRNA interaction network based on the STITCH and miRDB databases showed that resveratrol exerted a dual inhibitory effect by activating inhibitory TFs to block the cell cycle and inhibit miRNAs from upregulating apoptosis. However, these two processes did not work completely independently. TP53 is the dominant hub gene associated with the cell cycle and apoptosis throughout the TF–miRNA network. Kaplan–Meier plotter analysis found that resveratrol‐induced expression changes in key RNAs, such as E2F2, JUN, FOS, BRCA1, CDK1, CDKN1A, TNF, and hsa‐miR‐34a‐5p, significantly improved the prognosis of breast cancer patients, which was further verified using real‐time quantitative PCR (qPCR) and western blotting. This study constructed a TF–miRNA regulatory network with TP53 and E2F as the main central genes to elucidate the molecular mechanism of resveratrol in the treatment of breast cancer.

Modulation of inflammation by phytochemicals to enhance efficacy and reduce toxicity of cancer chemotherapy

Treatment of cancer with chemotherapeutic drugs is associated with numerous adverse effects as well as the eventual development of resistance to chemotherapy. There is a great need for complementary therapies such as botanicals and nutritional supplements with little or no side effects that prevent resistance to chemotherapy and reduce its adverse effects. Inflammation plays a major role in the development of chemoresistance and the adverse effects of chemotherapy. Phytochemicals have well-established anti-inflammatory effects; thus, they could be used as complementary therapies along with chemotherapy to increase its efficacy and reduce its toxicity. Botanical compounds inhibit the NF-κB signaling pathway, which plays an important role in the generation of inflammation, chemotherapy resistance, and modulation of cell survival and apoptosis. Botanicals have previously been studied extensively for their cancer chemopreventive activities and are generally considered safe for human consumption. The present review focuses on the modulation of inflammation by phytochemicals and their role in increasing the efficacy and reducing the toxicity of cancer chemotherapy.

Chemo-Preventive Action of Resveratrol: Suppression of p53-A Molecular Targeting Approach

Extensive experimental, clinical, and epidemiological evidence has explained and proven that products of natural origin are significantly important in preventing and/or ameliorating various disorders, including different types of cancer that researchers are extremely focused on. Among these studies on natural active substances, one can distinguish the emphasis on resveratrol and its properties, especially the potential anticancer role. Resveratrol is a natural product proven for its therapeutic activity, with remarkable anti-inflammatory properties. Various other benefits/actions have also been reported, such as cardioprotective, anti-ageing, antioxidant, etc. and its rapid digestion/absorption as well. This review aims to collect and present the latest published studies on resveratrol and its impact on cancer prevention, molecular signals (especially p53 protein participation), and its therapeutic prospects. The most recent information regarding the healing action of resveratrol is presented and concentrated to create an updated database focused on this topic presented above.

A Comprehensive Review of the Use of Antioxidants and Natural Products in Cancer Patients Receiving Anticancer Therapy

Cancer is the leading cause of mortality and morbidity worldwide. The side effects of cancer treatment affect the quality of life. Cancer patients search for antioxidant dietary supplements and natural products during or after conventional cancer treatment for the alleviation of side effects, improvement of the benefits of treatment, and promotion of well-being. However, the efficacy and safety of these products remain controversial; moreover, previous data do not support the standardized use of those alternative treatments in clinics. The current study reviewed the manuscripts reporting the administration of antioxidants and natural products during cancer treatment and revised preclinical and clinical studies on various types of cancer. Most of the positive results were obtained from experimental animal models; however, human clinical studies are discouraging in this regard. Therefore, further precise and distinguishable studies are required regarding antioxidant dietary supplementation. Future studies are also needed to clarify dietary supplements' mechanism of action and pharmacokinetics in a suitable cancer patient population that will benefit the therapeutic regimens. Despite the popularity of dietary supplements, clinicians and patients should always consider their potential benefits and risks. Patients should discuss with their physician before taking any dietary antioxidant supplements or natural products.

Resveratrol Modulation of Apoptosis and Cell Cycle Response to Cisplatin in Head and Neck Cancer Cell Lines

In head and neck cancers, the effectiveness of cisplatin (CisPt) treatment is limited by its toxicity, especially when higher doses are necessary, and the possible occurrence of cisplatin resistance. This study evaluated the effects of resveratrol (RSV) on the expression of different genes involved in the response of human tumor cells (FaDu, PE/CA-PJ49) to cisplatin therapy. Our results revealed that RSV induced apoptosis amplification in both FaDu and PE/CA-PJ49 cells and modulated the expression of specific genes differently than in normal HaCaT cells. In FaDu cells, combined CisPt + RSV treatment induced an increase in apoptosis, which was associated with an increase in c-MYC and TP53 and a decrease in BCL-2 expression. While CisPt + RSV treatment induced apoptosis in PE/CA-PJ49 cells by inhibition of BCL-2 associated with high levels of MDM-2 and subsequently led to inhibition of TP53 gene expression. Decreased c-MYC expression in PE/CA-PJ49 treated with CisPt + RSV was accompanied by cell cycle blockage in G0/G1 phase. In conclusion, RSV influences tumor cell response to CisPt by inducing apoptosis and modulating gene expression. In addition, in normal HaCaT cells, RSV was able to reduce the harmful effects of CisPt.

Anti-tumor activity of resveratrol against gastric cancer: a review of recent advances with an emphasis on molecular pathways

Gastric cancer (GC) is one of the most common cancers with high malignancy. In spite of the great development in diagnostic tools and application of anti-tumor drugs, we have not witnessed a significant increase in the survival time of patients with GC. Multiple studies have revealed that Wnt, Nrf2, MAPK, and PI3K/Akt signaling pathways are involved in GC invasion. Besides, long non-coding RNAs and microRNAs function as upstream mediators in GC malignancy. GC cells have acquired resistance to currently applied anti-tumor drugs. Besides, combination therapy is associated with higher anti-tumor activity. Resveratrol (Res) is a non-flavonoid polyphenol with high anti-tumor activity used in treatment of various cancers. A number of studies have demonstrated the potential of Res in regulation of molecular pathways involved in cancer malignancy. At the present review, we show that Res targets a variety of signaling pathways to induce apoptotic cell death and simultaneously, to inhibit the migration and metastasis of GC cells.

Bioactive Compounds and Metabolites from Grapes and Red Wine in Breast Cancer Chemoprevention and Therapy

Phytochemicals and their metabolites are not considered essential nutrients in humans, although an increasing number of well-conducted studies are linking their higher intake with a lower incidence of non-communicable diseases, including cancer. This review summarizes the current findings concerning the molecular mechanisms of bioactive compounds from grapes and red wine and their metabolites on breast cancer-the most commonly occurring cancer in women-chemoprevention and treatment. Flavonoid compounds like flavonols, monomeric catechins, proanthocyanidins, anthocyanins, anthocyanidins and non-flavonoid phenolic compounds, such as resveratrol, as well as their metabolites, are discussed with respect to structure and metabolism/bioavailability. In addition, a broad discussion regarding in vitro, in vivo and clinical trials about the chemoprevention and therapy using these molecules is presented.

Resveratrol, Curcumin and Piperine Alter Human Glyoxalase 1 in MCF-7 Breast Cancer Cells

Breast cancer is the leading cause of cancer mortality in women worldwide. Conventional cancer treatment is costly and results in many side effects. Dietary bioactive compounds may be a potential source for breast cancer prevention and treatment. In this scenario, the aim of this study was to investigate the effects of the bioactive compounds resveratrol, curcumin and piperine (R-C-P) on MCF-7 breast cancer cells and to associate them to Glyoxalase 1 (GLO1) activity. The findings indicate that R-C-P exhibits cytotoxicity towards MCF-7 cells. R-C-P decreased mitochondrial membrane potential (ΔΨm) by 1.93-, 2.04- and 1.17-fold, respectively. Glutathione and N-acetylcysteine were able to reverse the cytotoxicity of the assessed bioactive compounds in MCF-7 cells. R-C-P reduced GLO1 activity by 1.36-, 1.92- and 1.31-fold, respectively. R-C-P in the presence of antimycin A led to 1.98-, 1.65- and 2.16-fold decreases in D-lactate levels after 2 h of treatment, respectively. Glyoxal and methylglyoxal presented cytotoxic effects on MCF-7 cells, with IC₅₀ values of 2.8 and 2.7 mM and of 1.5 and 1.4 mM after 24 and 48 h of treatment, respectively. In conclusion, this study demonstrated that R-C-P results in cytotoxic effects in MCF-7 cells and that this outcome is associated with decreasing GLO1 activity and mitochondrial dysfunction.

Enhanced apoptogenesis and oncogene regulatory mechanism of troxerutin in triple negative breast cancer cells

Triple negative breast carcinoma (TNBC) is an aggressive form of cancer, with high rates of morbidity, mortality, poor prognosis and limited therapeutic options. The objective of the present study was to elaborate the anticancer activity of Troxerutin (TXN) in TNBC/MDA-MB-231 cells. Herein, we demonstrated the inhibitory effects of TXN on the breast cancer cell growth via induction of apoptosis. Mitochondrial membrane potential (∆Ψm), DNA damage and apoptotic nuclear changes were analyzed by flowcytometry, AO/EtBr and Hoechst staining, respectively. Furthermore, apoptotic protein and gene expressions were analyzed by western blot and reverse transcription polymerase chain reaction (RT-PCR), respectively. Our results indicated that TXN induces apoptosis as evidenced by inhibit the cell proliferation, enhanced apoptotic activation, altered mitochondrial membrane potential and elevated level of DNA damage in TNBC cells. Furthermore, the TXN inhibit anti-apoptotic protein expression with the subsequent upregulation of Cytochrome c, Caspase-9 and Caspase-3. Thus, TXN induces apoptosis in TNBC cells through inducing nuclear damage and altered apoptotic marker expressions. Therefore, TXN might be used as a potential therapeutic agent for the treatment of triple negative breast cancer.

Role of natural compounds in preventing and treating breast cancer

Breast cancer (BrCa) is the most commonly diagnosed cancer and the second leading cause of cancer-related death in women. Alarming increases in the cases quests for more effective treatment of BrCa. As most chemotherapeutic drugs are associated with drug resistance, cancer relapse, and side effects, scientists are turning to agents with more efficacy, such as natural compounds for treatment and prevention of BrCa. Selected natural compounds, substances derived from living organisms, promote apoptosis and inhibit metastasis, preventing cancer growth. As a result, these compounds have the potential to suppress BrCa progression, thus increasing patient survival rates and decreasing the number of BrCa-related deaths. In this review, we summarize natural compounds that have displayed, anti-cancer effects on BrCa cells in various studies. These natural compounds inhibit the development of BrCa, suppress the growth of cancer cells, and promote cell death. We conclude that natural compounds are efficient, effective and promising agents for treating BrCa other than therapeutic methods.

Resveratrol Modifies Lipid Composition of Two Cancer Cell Lines

Resveratrol (Resv) offers health benefits in cancer and has been reported to modulate important enzymes of lipid metabolism. Studies of its effects on lipid composition in different subtypes of breast-cancer cells are scarce. Thus, we investigated the alterations in phospholipids (PL), fatty acids (FA), and lipid metabolism enzymes in two breast-cancer cell lines after Resv treatment. MCF-7 and MDA-MB-231 cells were treated with 80 and 200 μM of Resv, respectively, for 24 hours. We analyzed PL with radiolabeled inorganic phosphate (³²Pi) by thin-layer chromatography, FA by gas chromatography-mass spectrometry, and lipid metabolism enzymes (DGAT2, FAS, ρACCβ, pAMPKα, and AMPK) by Western blot. Resv treated MDA-MB-231 phospholipids showed a reduction in phosphatidylcholine (63%) and phosphatidylethanolamine (35%). We observed an increase in eicosapentaenoic acid (EPA) (73%) and docosahexaenoic acid (DHA) (65%) in MCF-7 cells after Resv treatment. Interestingly, the same treatment caused 50% and 90% increases in EPA and DHA, respectively, in MDA-MB-231 cells. In MCF-7 cells, Resv increased the expression of ρACCβ (3.3-fold) and AMPKα/ρAMPKα (1.5-fold) and in MDA-MB-231 cells it inhibited the expression of ρACCβ (111.8-fold) and AMPKα/ρAMPKα (1.2 fold). Our results show that Resv modified PL and saturated and unsaturated FA especially in MDA-MB-231 cells, and open new perspectives to the understanding of the reported anticancer effect of Resv on these cells.

Etiology of atherosclerosis informs choice of animal models and tissues for initial functional genomic studies of resveratrol

Resveratrol, a phytoalexin, is a natural polyphenol synthesized exclusively by plants in response to environmental stresses. However, the molecule has also many exogenous bioactivities in animal cells. These bioactivities may lead to anti-cancer and cardio-protective health benefits. Because cellular responses to the treatment with resveratrol include the changes of expression patterns, functional genomics is an attractive tool to study them. In recent and today's experimental practice, this mostly means microarray profiling of gene expression (using RNAs isolated from bulk tissues). Herein, we review such published studies undertaken in the context of cardiovascular diseases (CVDs). CVDs are a number one public health problem in developed countries, outweighing in magnitude even cancer. In particular, we review the studies of resveratrol in several animal models relevant to CVDs. These models included: normal and pre-mature aging in mice, as well as atherogenic diet in mice / pigs / non-human primates. Additionally, there were few clinical studies published in the context of the comorbidities of atherosclerosis in humans (e.g. obesity, diabetes, hypertension). For the purposes of these studies, three types of samples were most commonly profiled with microarrays: the liver, the skeletal muscle, and peripheral blood mononuclear cells. Resveratrol-induced changes of gene expression typically mimicked those associated with calorie restriction and lifespan extension. They also opposed changes induced by the atherogenic diet. We conclude by discussing few experimental factors that were relatively neglected thus far, but which could be interesting to investigate in the future. These factors include sex and the exact formulation of resveratrol (plant extract, or synthetic chemical).

Increase in fatty acids and flotillins upon resveratrol treatment of human breast cancer cells

Flotillin-1 and flotillin-2 are highly conserved proteins that localize into cholesterol-rich microdomains in cellular membranes. Flotillins are closely related to the occurrence and development of various types of human cancers. Flotillin-1 is highly expressed in breast cancer, and the high expression level of flotillin-1 is significantly correlated with poorer patient survival. Here we studied the relationship between the formation of lipid rafts and the expression of flotillins and lipids in human breast cancer cells. We used the polyphenol compound resveratrol to alter the structure and function of the plasma membrane. Our data revealed an increase in fatty acids in MCF-7 and MDA-MB-231 cells upon resveratrol treatment. Interestingly, we also found an increase in the expression of both flotillin-1 and flotillin-2 in breast tumor cells after treatment. Resveratrol also induced changes in the pattern of flotillin distribution among detergent-resistant lipid rafts fractions in both cell lines and induced the nuclear translocation of flotillin-2. Since resveratrol has been pointed out as a putative cancer therapy agent, our results could have an impact on the understanding of the effects of resveratrol in tumor cells.

The Anticancer and Antioxidant Effects of Muscadine Grape Extracts on Racially Different Triple-negative Breast Cancer Cells

BACKGROUND/AIM

Triple-negative breast cancer (TNBC) is the most aggressive subtype, predominant in African American women. In this study, the antioxidant/anticancer activity of muscadine grape extracts and the role of their phenolic and flavonoid contents in exerting these properties were investigated in TNBC cells.

MATERIALS AND METHODS

Berry extracts from muscadine genotypes were investigated for total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity, and anticancer effects using breast cancer cell lines, representing Caucasians and African Americans.

RESULTS

The antioxidant activity was associated with high TPC content. Extracts showed cytotoxicity up to 78.6% in Caucasians and 90.7% in African American cells, with an association with high antioxidant capacity. There was a strong correlation between TPC and anticancer/antioxidant activities.

CONCLUSION

The anticancer and antioxidant effects of muscadine grapes are attributed to the TPC of extracts, which showed a stronger positive correlation with growth inhibition of African American breast cancer cells compared to Caucasians.

A Review of Resveratrol as a Potent Chemoprotective and Synergistic Agent in Cancer Chemotherapy

Background: Cancer has become a major disease endangering human health around the world. Conventional chemotherapy suffers from many side effects including pain, cardiotoxicity, hepatotoxicity, and renal toxicity. This review aims to describe a natural product of resveratrol as a chemoprotective and synergistic agent in the modulation of cancer chemotherapy.

Methods: The publications were identified by comprehensive searching of SciFinder, PubMed, Web of Science, and our own reference library. Search terms included combinations of “resveratrol,” “cancer,” “natural products,” “chemotherapy,” and “side effects.” Selection of material focused on resveratrol reducing the side effects on cancer chemotherapy.

Results: Thirty one references were referred in this review to outline resveratrol as a potent chemoprotective and synergistic agent in cancer chemotherapy, including 22 papers for describing the chemoprotective effects, and 9 papers for illustrating the synergistic effects.

Conclusion: This study provides a systematic summary of resveratrol serving as a potent chemoprotective and synergistic agent to reduce the associated-side effects and enhance the therapeutic outcomes in cancer chemotherapy. Further studies in terms of resveratrol on a large amount of preclinical tests and clinical trials are highly demanded.

Preparation and in vitro-in vivo characterization of trans-resveratrol nanosuspensions

Nanosuspensions technique is an important tool to enhance the saturation solubility and dissolution velocity of poorly soluble drugs. Trans-resveratrol (t-Res) with extensive pharmacological effects was severely restricted by poor solubility and short biological half-life. In this study, anti-solvent precipitation was employed to development trans-resveratrol nanosuspensions (t-Res NS) with PVPK30 as stabilizer. The physicochemical properties, in vitro release and in vivo pharmacokinetics of t-Res NS were investigated. The mean particle size, zeta potential, encapsulation efficiency and drug loading of t-Res NS prepared by the optimal prescription were 96.9 nm, -20.4mV, 78% and 28.1%, respectively. The morphology of t-Res nanoparticles was spherical indicated by SEM with amorphous phase verified by XRD and DSC. The t-Res NS present a good physical stability as well as enhanced chemical stability. Compared to crude drug, the in vitro dissolution rate of t-Res NS was increased with fitting Higuchi equation (Q=0.3215t1/2+0.0070). The in vivo pharmacokinetic test in rats showed that the AUC0∼t of t-Res NS (559.4 μg/mL·min) was about 3.6-fold higher than that of t-Res solution. Meanwhile, the MRT of t-Res nanosuspensions was longer than that of t-Res solution. These results suggested that NS may be a potentially nanocarrier for clinical delivery of t-Res.

In vitro and in vivo anti-inflammatory properties of imine resveratrol analogues

Resveratrol is a natural polyphenol found mainly on red grapes and in red wine, pointed as an important anti-inflammatory/immunomodulatory molecule. However, its bioavailability problems have limited its use encouraging the search for new alternatives agents. Thus, in this study, we synthetize 12 resveratrol analogues (6 imines, 1 thioimine and 5 hydrazones) and investigated its cytotoxicity, antioxidant activity and in vitro anti-inflammatory/immunomodulatory properties. The most promising compounds were also evaluated in vivo. The results showed that imines presented less cytotoxicity, were more effective than resveratrol on DPPH scavenger and exhibited an anti-inflammatory profile. Among them, the imines with a radical in the para position, on the ring B, not engaged in an intramolecular hydrogen-interaction, showed more prominent anti-inflammatory activity modulating, in vivo, the edema formation, the inflammatory infiltration and cytokine levels. An immunomodulatory activity also was observed in these molecules. Thus, our results suggest that imines with these characteristics presents potential to control inflammatory disorders.

Mechanistic evaluation of phytochemicals in breast cancer remedy: current understanding and future perspectives

Breast cancer is one of the most commonly diagnosed cancers around the globe and accounts for a large proportion of fatalities in women. Despite the advancement in therapeutic and diagnostic procedures, breast cancer still represents a major challenge. Current anti-breast cancer approaches include surgical removal, radiotherapy, hormonal therapy and the use of various chemotherapeutic drugs. However, drug resistance, associated serious adverse effects, metastasis and recurrence complications still need to be resolved which demand safe and alternative strategies. In this scenario, phytochemicals have recently gained huge attention due to their safety profile and cost-effectiveness. These phytochemicals modulate various genes, gene products and signalling pathways, thereby inhibiting breast cancer cell proliferation, invasion, angiogenesis and metastasis and inducing apoptosis. Moreover, they also target breast cancer stem cells and overcome drug resistance problems in breast carcinomas. Phytochemicals as adjuvants with chemotherapeutic drugs have greatly enhanced their therapeutic efficacy. This review focuses on the recently recognized molecular mechanisms underlying breast cancer chemoprevention with the use of phytochemicals such as curcumin, resveratrol, silibinin, genistein, epigallocatechin gallate, secoisolariciresinol, thymoquinone, kaempferol, quercetin, parthenolide, sulforaphane, ginsenosides, naringenin, isoliquiritigenin, luteolin, benzyl isothiocyanate, α-mangostin, 3,3'-diindolylmethane, pterostilbene, vinca alkaloids and apigenin.

The comparative study among different fractions of muscadine grape 'Noble' pomace extracts regarding anti-oxidative activities, cell cycle arrest and apoptosis in breast cancer

As a by-product of wine making, pomace contains rich amounts of phenolic compounds that can be potentially utilized as raw materials to make beneficial products especially for the anti-cancer agents including the breast cancer. Muscadinia rotundifolia ‘Noble’ is a wine-making grape cultivar, and to better use ‘Noble’ pomace, the most effective phenolic fractions in cancer inhibition must be identified. In this study, anti-oxidative activities of three separated fractions of ‘Noble’ pomace (F1, F2 and F3) were compared in 2,2-diphenyl-1-picrylhydrazyl and 2,2ʹ-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging (DPPH and ABTS) assays as well as the ferric-reducing antioxidant power (FRAP) assay. The ability of different fractions to induce cell cycle arrest and apoptosis in MDA-MB-231 breast cancer cells was also evaluated by flow cytometry and Western blot analysis. Fraction F3, which contained a mixture of anthocyanidins and ellagic acids, exhibited the strongest anti-oxidative activity, as determined at both low and high concentrations in the DPPH and FRAP assays. F3 also demonstrated the greatest ability to induce apoptosis via caspase activation and cell cycle arrest by downregulating cyclin A and upregulating p21. F3 was thus the most effective bioactive fraction among those prepared from muscadine grape ‘Noble’ pomace.

The Role of Resveratrol in Cancer Therapy

Natural product compounds have recently attracted significant attention from the scientific community for their potent effects against inflammation-driven diseases, including cancer. A significant amount of research, including preclinical, clinical, and epidemiological studies, has indicated that dietary consumption of polyphenols, found at high levels in cereals, pulses, vegetables, and fruits, may prevent the evolution of an array of diseases, including cancer. Cancer development is a carefully orchestrated progression where normal cells acquires mutations in their genetic makeup, which cause the cells to continuously grow, colonize, and metastasize to other organs such as the liver, lungs, colon, and brain. Compounds that modulate these oncogenic processes can be considered as potential anti-cancer agents that may ultimately make it to clinical application. Resveratrol, a natural stilbene and a non-flavonoid polyphenol, is a phytoestrogen that possesses anti-oxidant, anti-inflammatory, cardioprotective, and anti-cancer properties. It has been reported that resveratrol can reverse multidrug resistance in cancer cells, and, when used in combination with clinically used drugs, it can sensitize cancer cells to standard chemotherapeutic agents. Several novel analogs of resveratrol have been developed with improved anti-cancer activity, bioavailability, and pharmacokinetic profile. The current focus of this review is resveratrol’s in vivo and in vitro effects in a variety of cancers, and intracellular molecular targets modulated by this polyphenol. This is also accompanied by a comprehensive update of the various clinical trials that have demonstrated it to be a promising therapeutic and chemopreventive agent.

Cancer Chemoprevention by Resveratrol: The p53 Tumor Suppressor Protein as a Promising Molecular Target

Increasing epidemiological and experimental evidence has demonstrated an inverse relationship between the consumption of plant foods and the incidence of chronic diseases, including cancer. Microcomponents that are naturally present in such foods, especially polyphenols, are responsible for the benefits to human health. Resveratrol is a diet-derived cancer chemopreventive agent with high therapeutic potential, as demonstrated by different authors. The aim of this review is to collect and present recent evidence from the literature regarding resveratrol and its effects on cancer prevention, molecular signaling (especially regarding the involvement of p53 protein), and therapeutic perspectives with an emphasis on clinical trial results to date.

Preclinical Efficacy and Safety Assessment of Artemisinin-Chemotherapeutic Agent Conjugates for Ovarian Cancer

Artemisinin (ARS) and its derivatives, which are clinically used antimalarial agents, have shown antitumor activities. Their therapeutic potencies, however, are limited by their low solubility and poor bioavailability. Here, through a pharmacophore hybridization strategy, we synthesized ARS-drug conjugates, in which the marketed chemotherapeutic agents chlorambucil, melphalan, flutamide, aminoglutethimide, and doxifluridine, were separately bonded to Dihydroartemisinin (DHA) through various linkages. Of these, the artemisinin-melphalan conjugate, ARS4, exhibited most toxicity to human ovarian cancer cells but had low cytotoxicity to normal cells. ARS4 inhibited the growth and proliferation of ovarian cancer cells and resulted in S-phase arrest, apoptosis, and inhibition of migration; these effects were stronger than those of its parent drugs, DHA and melphalan. Furthermore, ARS4 modulated the expression of proteins involved in cell cycle progression, apoptosis, and the epithelial–mesenchymal transition (EMT). Moreover, in mice, ARS4 inhibited growth and intraperitoneal dissemination and metastasis of ovarian cancer cells without observable toxic effects. Our results provide a basis for development of the compound as a chemotherapeutic agent.

Research in context

Artemisinin compounds have recently received attention as anticancer agents because of their clinical safety profiles and broad efficacy. However, their therapeutic potencies are limited by low solubility and poor bioavailability. Here, we report that ARS4, an artemisinin-melphalan conjugate, possesses marked in-vitro and in-vivo antitumor activity against ovarian cancer, the effects of which are stronger than those for its parent drugs, Dihydroartemisinin and melphalan. In mice, ARS4 inhibits localized growth of ovarian cancer cells and intraperitoneal dissemination and metastasis without appreciable host toxicity. Thus, for patients with ovarian cancer, ARS4 is a promising chemotherapeutic agent.

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Artemisinin-drug conjugates were designed via pharmacophore hybridization strategy

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ARS4 induced apoptosis of ovarian cancer cells and cell cycle arrest and reversed the EMT polarity

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In mice, ARS4 inhibited growth and intraperitoneal dissemination of ovarian cancer cells with no appreciable host toxicity

Unraveling the Anticancer Effect of Curcumin and Resveratrol

Resveratrol and curcumin are natural products with important therapeutic properties useful to treat several human diseases, including cancer. In the last years, the number of studies describing the effect of both polyphenols against cancer has increased; however, the mechanism of action in all of those cases is not completely comprehended. The unspecific effect and the ability to interfere in assays by both polyphenols make this challenge even more difficult. Herein, we analyzed the anticancer activity of resveratrol and curcumin reported in the literature in the last 11 years, in order to unravel the molecular mechanism of action of both compounds. Molecular targets and cellular pathways will be described. Furthermore, we also discussed the ability of these natural products act as chemopreventive and its use in association with other anticancer drugs.

Characterization of the 5'-flanking region of the human TP53 gene and its response to the natural compound, Resveratrol

Tumour suppressor p53, which is encoded by theTP53gene, is widely known to play an important role in response to DNA damage and various stresses. It has recently been reported that p53 regulates glucose metabolism and that an increase in p53 protein level is induced after serum deprivation or treatments with a natural compound,trans-Resveratrol (Rsv). In this study, we constructed a Luciferase expression vector, pGL4-TP53-551, containing 551 bp of the 5'-upstream region of the humanTP53gene, which was then transfected into HeLa S3 cells. A Luciferase assay showed that Rsv treatment increased the promoter activity of theTP53gene in comparison to that ofPIF1 Detailed deletion and mutation analyses revealed that Nkx-2.5 and E2F-binding elements are required in addition to duplicated GGAA (TTCC), for the regulation ofTP53promoter activity. In this study, it is suggested that the transient induction ofTP53gene expression by Rsv treatment might be partly involved in its anti-aging effect through maintenance of chromosomal DNAs.

Resveratrol for breast cancer prevention and therapy: Preclinical evidence and molecular mechanisms

Globally, breast cancer is the most frequently diagnosed cancer among women. The major unresolved problems with metastatic breast cancer is recurrence after receiving objective response to chemotherapy, drug-induced side effects of first line chemotherapy and delayed response to second line of treatment. Unfortunately, very few options are available as third line treatment. It is clear that under such circumstances there is an urgent need for new and effective drugs. Phytochemicals are among the most promising chemopreventive treatment options for the management of cancer. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a non-flavonoid polyphenol present in several dietary sources, including grapes, berries, soy beans, pomegranate and peanuts, has been shown to possess a wide range of health benefits through its effect on a plethora of molecular targets.The present review encompasses the role of resveratrol and its natural/synthetic analogue in the light of their efficacy against tumor cell proliferation, metastasis, epigenetic alterations and for induction of apoptosis as well as sensitization toward chemotherapeutic drugs in various in vitro and in vivo models of breast cancer. The roles of resveratrol as a phytoestrogen, an aromatase inhibitor and in stem cell therapy as well as adjuvent treatment are also discussed. This review explores the full potential of resveratrol in breast cancer prevention and treatment with current limitations, challenges and future directions of research.

Role of Natural Stilbenes in the Prevention of Cancer

Natural stilbenes are an important group of nonflavonoid phytochemicals of polyphenolic structure characterized by the presence of a 1,2-diphenylethylene nucleus. Stilbenes have an extraordinary potential for the prevention and treatment of different diseases, including cancer, due to their antioxidant, cell death activation, and anti-inflammatory properties which associate with low toxicity under in vivo conditions. This review aims to discuss various approaches related to their mechanisms of action, pharmacological activities in animal models and humans, and potential chemoprevention in clinical studies. The biological activity of natural stilbenes is still incompletely understood. Furthermore, after administration to animals or humans, these molecules are rapidly metabolized. Thus pharmacokinetics and/or activities of the natural structures and their metabolites may be very different. Novel drug formulations have been postulated in order to improve stability and bioavailability, to minimize side effects, and to facilitate interaction with their domains in target proteins. These pharmacological improvements should lead stilbenes to become effective candidates as anticancer drugs.

Strategy to enhance efficacy of doxorubicin in solid tumor cells by methyl-β-cyclodextrin: Involvement of p53 and Fas receptor ligand complex

Doxorubicin (DOX) is one of the preferred drugs for treating breast and liver cancers. However, its clinical application is limited due to severe side effects and the accompanying drug resistance. In this context, we investigated the effect on therapeutic efficacy of DOX by cholesterol depleting agent methyl-β-cyclodextrin (MCD), and explored the involvement of p53. MCD sensitizes MCF-7 and Hepa1–6 cells to DOX, Combination of MCD and marginal dose of DOX reduces the cell viability, and promoted apoptosis through induction of pro-apoptotic protein, Bax, activation of caspase-8 and caspase-7, down regulation of anti-apoptotic protein Bcl-2 and finally promoting PARP cleavage. Mechanistically, sensitization to DOX by MCD was due to the induction of FasR/FasL pathway through p53 activation. Furthermore, inhibition of p53 by pharmacological inhibitor pifithrin-α (PFT-α) or its specific siRNA attenuated p53 function and down-regulated FasR/FasL, thereby preventing cell death. Animal experiments were performed using C57BL/6J mouse isografted with Hepa1–6 cells. Tumor growth was retarded and survival increased in mice administered MCD together with DOX to as compared to either agent alone. Collectively, these results suggest that MCD enhances the sensitivity to DOX for which wild type p53 is an important determinant.

Resveratrol Enhances Etoposide-Induced Cytotoxicity through Down-Regulating ERK1/2 and AKT-Mediated X-ray Repair Cross-Complement Group 1 (XRCC1) Protein Expression in Human Non-Small-Cell Lung Cancer Cells

Etoposide (VP-16), a topoisomerase II inhibitor, is an effective anti-cancer drug used for the treatment of non-small-cell lung cancer (NSCLC). Resveratrol is a naturally occurring polyphenolic compound that has been proved to have anti-cancer activity. XRCC1 is an important scaffold protein involved in base excision repair that is regulated by ERK1/2 and AKT signals and plays an important role in the development of lung cancer. However, the role of ERK1/2 and AKT-mediated XRCC1 expression in etoposide treatment alone or combined with resveratrol-induced cytotoxicity in NSCLC cells has not been identified. In this study, etoposide treatment increased XRCC1 mRNA and protein expression through AKT and ERK1/2 activation in two NSCLC cells, H1703 and H1975. Knockdown of XRCC1 in NSCLC cells by transfection of XRCC1 siRNA or inactivation of ERK1/2 and AKT resulted in enhancing cytotoxicity and cell growth inhibition induced by etoposide. Resveratrol inhibited the expression of XRCC1 and enhanced the etoposide-induced cell death and anti-proliferation effect in NSCLC cells. Furthermore, transfection with constitutive active MKK1 or AKT vectors could rescue the XRCC1 protein level and also the cell survival suppressed by co-treatment with etoposide and resveratrol. These findings suggested that down-regulation of XRCC1 expression by resveratrol can enhance the chemosensitivity of etoposide in NSCLC cells.

Resveratrol suppresses TPA-induced matrix metalloproteinase-9 expression through the inhibition of MAPK pathways in oral cancer cells

BACKGROUND

Naturally occurring agents, such as resveratrol, have been determined to benefit health. Numerous studies have demonstrated that resveratrol has antioxidative, cardioprotective, and neuroprotective properties. However, the effect of resveratrol exerts on the metastasis of oral cancer cells remains unclear. In this study, we investigated the effect the anti-invasive activity of resveratrol on a human oral cancer cell line (SCC-9) in vitro and the underlying mechanisms.

METHODS

Cell viability was examined by MTT assay, whereas cell motility was measured by migration and wound-healing assays. Zymography, reverse-transcriptase polymerase chain reaction (PCR), and promoter assays confirmed the inhibitory effects of resveratrol on matrix metalloproteinase-9 (MMP-9) expression in oral cancer cells.

RESULTS

We established that various concentrations (0-100 μM) of resveratrol inhibited the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced migration capacities of SCC-9 cells and caused no cytotoxic effects. Zymography and Western blot analyses suggested that resveratrol inhibited TPA-induced MMP-9 gelatinolytic activity and protein expression. In addition, the results indicated that resveratrol inhibited the phosphorylation of c-Jun N-terminal kinase (JNK)1/2 and extracellular-signal-regulated kinase (ERK)1/2 involved in downregulating protein expression and the transcription of MMP-9.

CONCLUSION

In summary, resveratrol inhibited MMP-9 expression and oral cancer cell metastasis by downregulating JNK1/2 and ERK1/2 signals pathways and, thus, exerts beneficial effects in chemoprevention.

Gallotannin imposes S phase arrest in breast cancer cells and suppresses the growth of triple-negative tumors in vivo

Triple-negative breast cancers are associated with poor clinical outcomes and new therapeutic strategies are clearly needed. Gallotannin (Gltn) has been previously demonstrated to have potent anti-tumor properties against cholangiocarcinoma in mice, but little is known regarding its capacity to suppress tumor outgrowth in breast cancer models. We tested Gltn for potential growth inhibitory properties against a variety of breast cancer cell lines in vitro. In particular, triple-negative breast cancer cells display higher levels of sensitivity to Gltn. The loss of proliferative capacity in Gltn exposed cells is associated with slowed cell cycle progression and S phase arrest, dependent on Chk2 phosphorylation and further characterized by changes to proliferation related genes, such as cyclin D1 (CcnD1) as determined by Nanostring technology. Importantly, Gltn administered orally or via intraperitoneal (IP) injections greatly reduced tumor outgrowth of triple-negative breast cells from mammary fat pads without signs of toxicity. In conclusion, these data strongly suggest that Gltn represents a novel approach to treat triple-negative breast carcinomas.

Resveratrol inhibits the growth of gastric cancer by inducing G1 phase arrest and senescence in a Sirt1-dependent manner

Resveratrol, a naturally occurring polyphenolic compound, has been reported to exert anticancer activity by affecting diverse molecular targets. In this study, we examined the effects and the underlying mechanisms of resveratrol on gastric cancer. We found that resveratrol inhibited the proliferation of gastric cancer cells in a dose-dependent manner. At the concentration of 25 and 50 µM, resveratrol inhibited the cell viability and diminished the clonogenic potential of gastric cancer cells. Resveratrol treatment arrested gastric cancer cells in the G1 phase and led to senescence instead of apoptosis. Regulators of the cell cycle and senescence pathways, including cyclin D1, cyclin-dependent kinase (CDK4 and 6), p21 and p16, were dysregulated by resveratrol treatment. The inhibitory effects of resveratrol on gastric cancer were also verified in vivo using a nude mice xenograft model. Resveratrol (40 mg/kg/d) exerted inhibitory activities on gastric cancer development and significantly decreased the fractions of Ki67-positive cells in the tumor specimens from the nude mice. After resveratrol treatment, the induction of senescence and the changes in the expression of the regulators involved in the cell cycle and senescence pathways were similar to what we observed in vitro. However, the depletion of Sirtuin (Sirt)1 reversed the above-described effects of resveratrol both in vitro and in vivo. Our data suggest that resveratrol inhibits gastric cancer in a Sirt1-dependent manner and provide detailed evidence for the possibility of applying resveratrol in gastric cancer prevention and therapy.

Resveratrol contributes to chemosensitivity of malignant mesothelioma cells with activation of p53

Resveratrol is a naturally occurring polyphenolic phytoalexin with chemopreventive properties. We previously reported a synergistic anti-proliferative effect of resveratrol and clofarabine against malignant mesothelioma (MM) cells. Here, we further investigated molecular mechanisms involved in the synergistic interaction of these compounds in MM MSTO-211H cells. Resveratrol, in combination with clofarabine, time-dependently induced a strong cytotoxic effect with the nuclear accumulation of phospho-p53 (p-p53) in MSTO-211H cells, but not in normal mesothelial MeT-5A cells. Combination treatment up-regulated the levels of p-p53, cleaved caspase-3, and cleaved PARP proteins. Gene silencing with p53-targeting siRNA attenuated the sensitivity of cells to the combined treatment of two compounds. Analyses of p53 DNA binding assay, p53 reporter gene assay, and RTP-CR toward p53-regulated genes, including Bax, PUMA, Noxa and p21, demonstrated that induced p-p53 is transcriptionally active. These results were further confirmed by the siRNA-mediated knockdown of p53 gene. Combination treatment significantly caused the accumulation of cells at G1 phase with the increases in the sub-G0/G1 peak, DNA ladder, nuclear fragmentation, and caspase-3/7 activity. Taken together, these results demonstrate that resveratrol and clofarabine synergistically elicit apoptotic signal via a p53-dependent pathway, and provide a scientific rationale for clinical evaluation of resveratrol as a promising chemopotentiator in MM.

Apoptosis and autophagy induction as mechanism of cancer prevention by naturally occurring dietary agents

Nontoxic naturally occurring compounds, especially those from dietary sources, are receiving increasing consideration for prevention and treatment of diseases including cancer. There is a growing need for innovative anticancer therapies and therefore search for natural compounds with novel biological activities or antineoplastic potential is currently an important area in drug discovery. Support for this interest also comes from increasing concern over the efficacy and safety of many conventional therapies, especially those that run over a long course of time. Laboratory studies in different in vitro and in vivo systems have shown that many natural compounds possess the capacity to regulate response to oxidative stress and DNA damage, suppress angiogenesis, inhibit cell proliferation and induce autophagy and apoptosis. This review discusses the induction of apoptosis and autophagy as a mechanism of cancer prevention by some of the most studied naturally occurring dietary compounds.

Resveratrol enhances chemosensitivity of doxorubicin in multidrug-resistant human breast cancer cells via increased cellular influx of doxorubicin

BACKGROUND

Multidrug resistance is a major problem in the treatment of breast cancer, and a number of studies have attempted to find an efficient strategy with which to overcome it. In this study, we investigate the synergistic anticancer effects of resveratrol (RSV) and doxorubicin (Dox) against human breast cancer cell lines.

METHODS

The synergistic effects of RSV on chemosensitivity were examined in Dox-resistant breast cancer (MCF-7/adr) and MDA-MB-231 cells. In vivo experiments were performed using a nude mouse xenograft model to investigate the combined sensitization effect of RSV and Dox.

RESULTS AND CONCLUSION

RSV markedly enhanced Dox-induced cytotoxicity in MCF-7/adr and MDA-MB-231 cells. Treatment with a combination of RSV and Dox significantly increased the cellular accumulation of Dox by down-regulating the expression levels of ATP-binding cassette (ABC) transporter genes, MDR1, and MRP1. Further in vivo experiments in the xenograft model revealed that treatment with a combination of RSV and Dox significantly inhibited tumor volume by 60%, relative to the control group.

GENERAL SIGNIFICANCE

These results suggest that treatment with a combination of RSV and Dox would be a helpful strategy for increasing the efficacy of Dox by promoting an intracellular accumulation of Dox and decreasing multi-drug resistance in human breast cancer cells.