Suppression of Heregulin-β1/HER2-Modulated Invasive and Aggressive Phenotype of Breast Carcinoma by Pterostilbene via Inhibition of Matrix Metalloproteinase-9, p38 Kinase Cascade and Akt Activation

Experimental Studies on the Therapeutic Potential of Vaccinium Berries in Breast Cancer-A Review

Breast cancer (BC) is the largest contributor to cancer deaths in women worldwide. Various parts of plants, including fruits, are known for their therapeutic properties and are used in traditional medicine. Fruit species exhibit anticancer activities due to the presence of bioactive natural compounds such as flavonoids and carotenoids. The Vaccinium spp. are fleshy berry-like drupes and are rich in bioactive compounds, with flavonols, flavanols, chalcones, and phenolic acids as the major groups of compounds. While there is clear evidence linking Vaccinium berries with a decreased risk of BC both in in vivo and in vitro experiments, the exact mechanisms involved in the protective effects of Vaccinium spp. rich extracts on BC cells are not fully understood. Thus, the purpose of this review is to highlight the mechanisms of action involved in the therapeutic potential of Vaccinium berries against BC in experimental models.

Influence of Pterostilbene on Gene Expression in Liver Cancer: An In Silico Analysis

Background Liver cancer, in particular, is a serious threat to global health and has few viable treatments. One natural molecule that shows potential in cancer therapy is pterostilbene, especially for hepatocellular carcinoma (HCC). The molecular details of pterostilbene's interactions with liver cancer are uncovered in this study using an in silico method. Methodology This study determines the differentially expressed genes (DEGs) in HCC and the way pterostilbene affects them using data from Gene Expression Omnibus (GEO) datasets. To identify the intricate linkages and possible treatment targets, network pharmacology, protein-protein interaction (PPI) analysis, and pathway enrichment investigations were performed. Results The study revealed complex relationships between pterostilbene and liver cancer, identified important DEGs in HCC, and showed enriched pathways. Pterostilbene shows promise as a target for therapeutic approaches in HCC due to its modulation of important signaling pathways. Conclusions This work offers an extensive knowledge of pterostilbene's potential in liver cancer, despite intrinsic computational limitations. In addition to the importance of experimental validation, the pathways and DEGs that have been found provide insightful information for future investigation, highlighting the ongoing research that is necessary to create targeted therapeutics for HCC.

Pterostilbene-Mediated Inhibition of Cell Proliferation and Cell Death Induction in Amelanotic and Melanotic Melanoma

Melanoma is one of the fastest-growing cancers worldwide. Treatment of advanced melanoma is very difficult; therefore, there is growing interest in the identification of new therapeutic agents. Pterostilbene is a natural stilbene that has been found to have several pharmacological activities. The aim of this study was to evaluate the influence of pterostilbene on the proliferation and apoptosis of human melanoma cells. Proliferation of pterostilbene-treated amelanotic (C32) and melanotic (A2058) melanoma cells was determined by BRDU assay. Flow cytometric analyses were used to determine cell cycle progression, and further molecular investigations were performed using real-time RT-qPCR. The expression of the p21 protein and the DNA fragmentation assay were determined by the ELISA method. The results revealed that pterostilbene reduced the proliferation of both amelanotic and melanotic melanoma cells. Pterostilbene induced apoptosis in amelanotic C32 melanoma cells, and this effect was mediated by an increase in the expression of the BAX, CASP9, and CASP9 genes; induction of caspase 3 activity; and DNA degradation. Pterostilbene did not affect the activation of apoptosis in the A2058 cell line. It may be concluded that pterostilbene has anticancer potential against human melanoma cells; however, more studies are still needed to fully elucidate the effects of pterostilbene on amelanotic and melanotic melanoma cells.

Targeting Breast Cancer Stem Cells Using Naturally Occurring Phytoestrogens

Breast cancer therapies have made significant strides in improving survival for patients over the past decades. However, recurrence and drug resistance continue to challenge long-term recurrence-free and overall survival rates. Mounting evidence supports the cancer stem cell model in which the existence of a small population of breast cancer stem cells (BCSCs) within the tumor enables these cells to evade conventional therapies and repopulate the tumor, giving rise to more aggressive, recurrent tumors. Thus, successful breast cancer therapy would need to target these BCSCs, as well the tumor bulk cells. Since the Women’s Health Initiative study reported an increased risk of breast cancer with the use of conventional hormone replacement therapy in postmenopausal women, many have turned their attention to phytoestrogens as a natural alternative. Phytoestrogens are plant compounds that share structural similarities with human estrogens and can bind to the estrogen receptors to alter the endocrine responses. Recent studies have found that phytoestrogens can also target BCSCs and have the potential to complement conventional therapy eradicating BCSCs. This review summarized the latest findings of different phytoestrogens and their effect on BCSCs, along with their mechanisms of action, including selective estrogen receptor binding and inhibition of molecular pathways used by BCSCs. The latest results of phytoestrogens in clinical trials are also discussed to further evaluate the use of phytoestrogen in the treatment and prevention of breast cancer.

Apoptotic and Nonapoptotic Activities of Pterostilbene against Cancer

Cancer is a major cause of death. The outcomes of current therapeutic strategies against cancer often ironically lead to even increased mortality due to the subsequent drug resistance and to metastatic recurrence. Alternative medicines are thus urgently needed. Cumulative evidence has pointed out that pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene, PS) has excellent pharmacological benefits for the prevention and treatment for various types of cancer in their different stages of progression by evoking apoptotic or nonapoptotic anti-cancer activities. In this review article, we first update current knowledge regarding tumor progression toward accomplishment of metastasis. Subsequently, we review current literature regarding the anti-cancer activities of PS. Finally, we provide future perspectives to clinically utilize PS as novel cancer therapeutic remedies. We, therefore, conclude and propose that PS is one ideal alternative medicine to be administered in the diet as a nutritional supplement.

Promising therapeutic potential of pterostilbene and its mechanistic insight based on preclinical evidence

Pterostilbene (PS) is a well-recognized antioxidant that primarily exists in blueberries, grapevines and heartwood of red sandalwood. Interest in this compound has been renewed in recent years, and studies have found that PS possesses an array of pharmacological properties, including chemopreventive, antiinflammatory, antidiabetic, antidyslipidemic, antiatherosclerotic and neuroprotective effects. However, the greater in vivo bioavailability of PS, as compared to resveratrol, is an added advantage for its efficacy. This review provides a summary regarding the sources, pharmacokinetic aspects and pharmacodynamics of PS, with a focus on the molecular mechanisms underlying its protective effects against cancer, brain injuries and heart disease. Studies regarding the safety profile of PS have also been included. Based on the presently available evidence, we conclude that PS represents an active phytonutrient and a potential drug with pleiotropic health applications.

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.

Syringetin suppresses osteoclastogenesis mediated by osteoblasts in human lung adenocarcinoma

Bone metastasis in lung cancer results in an unfavorable outcome for patients by not only impairing the quality of life, yet also increasing the cancer-related death rates. In the present study, we discuss a novel treatment strategy that may benefit these patients. Human CD14+ monocytes treated with macrophage-colony stimulating factor (M-CSF)/receptor activator of nuclear factor κB ligand (RANKL) differentiated into osteoclasts, whereas syringetin (SGN), a flavonoid derivative found in both grapes and wine, suppressed the osteoclastogenesis in vitro in a dose-dependent manner. In addition, SGN inhibited osteoclast formation induced by human lung adenocarcinoma A549 and CL1-5 cells. The associated signaling transduction pathway in osteoclastogenesis and SGN inhibition was found to be via the AKT/mammalian target of rapamycin (mTOR) signaling pathway. Blocking AKT and mTOR by respective inhibitors significantly decreased lung adenocarcinoma-mediated osteoclastogenesis. Moreover, SGN regulated the lung adenocarcinoma-mediated interaction between osteoblasts and osteoclasts by suppressing the stimulatory effect of lung adenocarcinoma on M-CSF and RANKL production in osteoblasts, and reversing the inhibitory effect of the lung adenocarcinoma on OPG production in osteoblasts. The present study has two novel findings. It is the first to illustrate lung adenocarcinoma-mediated interaction between osteoblasts and osteoclasts, leading to osteolytic bone metastasis. It also reveals that SGN, a flavonoid derivative, directly inhibits osteoclastogenesis and reverses lung adenocarcinoma-mediated osteoclastogenesis. In conclusion, the present study suggests that SGN, a natural compound, prevents and treats bone metastasis in patients with lung cancer.

Estrogen receptor-α36 is involved in pterostilbene-induced apoptosis and anti-proliferation in in vitro and in vivo breast cancer

Pterostilbene (trans-3,5-dimethoxy-4′-hudroxystilbene) is an antioxidant primarily found in blueberries. It also inhibits breast cancer regardless of conventional estrogen receptor (ER-α66) status by inducing both caspase-dependent and caspase-independent apoptosis. However, the pterostilbene-induced apoptosis rate in ER-α66-negative breast cancer cells is much higher than that in ER-α66-positive breast cancer cells. ER-α36, a variant of ER-α66, is widely expressed in ER-α66-negative breast cancer, and its high expression mediates the resistance of ER-α66-positive breast cancer patients to tamoxifen therapy. The aim of the present study is to determine the relationship between the antiproliferation activity of pterostilbene and ER-α36 expression in breast cancer cells. Methyl-thiazolyl-tetrazolium (MTT) assay, apoptosis analysis, and an orthotropic xenograft mouse model were used to examine the effects of pterostilbene on breast cancer cells. The expressions of ER-α36 and caspase 3, the activation of ERK and Akt were also studied through RT-PCR, western blot analysis, and immunohistochemical (IHC) staining. ER-α36 knockdown was found to desensitize ER-α66-negative breast cancer cells to pterostilbene treatment both in vitro and in vivo, and high ER-α36 expression promotes pterostilbene-induced apoptosis in breast cancer cells. Western blot analysis data indicate that MAPK/ERK and PI3K/Akt signaling in breast cancer cells with high ER-α36 expression are mediated by ER-α36, and are inhibited by pterostilbene. These results suggest that ER-α36 is a therapeutic target in ER-α36-positive breast cancer, and pterostilbene is an inhibitor that targets ER-α36 in the personalized therapy against ER-α36-positive breast cancer.

The novel pterostilbene derivative ANK-199 induces autophagic cell death through regulating PI3 kinase class III/beclin 1/Atg‑related proteins in cisplatin‑resistant CAR human oral cancer cells

Pterostilbene is an effective chemopreventive agent against multiple types of cancer cells. A novel pterostilbene derivative, ANK-199, was designed and synthesized by our group. Its antitumor activity and mechanism in cisplatin-resistant CAR human oral cancer cells were investigated in this study. Our results show that ANK-199 has an extremely low toxicity in normal oral cell lines. The formation of autophagic vacuoles and acidic vesicular organelles (AVOs) was observed in the ANK-199-treated CAR cells by monodansylcadaverine (MDC) and acridine orange (AO) staining, suggesting that ANK-199 is able to induce autophagic cell death in CAR cells. Neither DNA fragmentation nor DNA condensation was observed, which means that ANK-199-induced cell death is not triggered by apoptosis. In accordance with morphological observation, 3-MA, a specific inhibitor of PI3K kinase class III, can inhibit the autophagic vesicle formation induced by ANK-199. In addition, ANK-199 is also able to enhance the protein levels of autophagic proteins, Atg complex, beclin 1, PI3K class III and LC3-II, and mRNA expression of autophagic genes Atg7, Atg12, beclin 1 and LC3-II in the ANK-199-treated CAR cells. A molecular signaling pathway induced by ANK-199 was therefore summarized. Results presented in this study show that ANK-199 may become a novel therapeutic reagent for the treatment of oral cancer in the near future (patent pending).

Pterostilbene-isothiocyanate conjugate suppresses growth of prostate cancer cells irrespective of androgen receptor status

Chemotherapy and anti-hormonal therapies are the most common treatments for non-organ-confined prostate cancer (PCa). However, the effectiveness of these therapies is limited, thus necessitating the development of alternative approaches. The present study focused on analyzing the role of pterostilbene (PTER)-isothiocyanate (ITC) conjugate--a novel class of hybrid compound synthesized by appending an ITC moiety on PTER backbone--in regulating the functions of androgen receptor (AR), thereby causing apoptosis of PCa cells. The conjugate molecule caused 50% growth inhibition (IC50) at 40 ± 1.12 and 45 ± 1.50 μM in AR positive (LNCaP) and negative (PC-3) cells, respectively. The reduced proliferation of PC-3 as well as LNCaP cells by conjugate correlated with accumulation of cells in G2/M phase and induction of caspase dependent apoptosis. Both PI3K/Akt and MAPK/ERK pathways played an important and differential role in conjugate-induced apoptosis of these PCa cells. While the inhibitor of Akt (A6730) or Akt-specific small interference RNA (siRNA) greatly sensitized PC-3 cells to conjugate-induced apoptosis, on the contrary, apoptosis was accelerated by inhibition of ERK (by PD98059 or ERK siRNA) in case of LNCaP cells, both ultimately culminating in the expression of cleaved caspase-3 protein. Moreover, anti-androgenic activity of the conjugate was mediated by decreased expression of AR and its co-activators (SRC-1, GRIP-1), thus interfering in their interactions with AR. All these data suggests that conjugate-induced inhibition of cell proliferation and induction of apoptosis are partly mediated by the down regulation of AR, Akt, and ERK signaling. These observations provide a rationale for devising novel therapeutic approaches for treating PCa by using conjugate alone or in combination with other therapeutics.

Fisetin inhibits migration and invasion of human cervical cancer cells by down-regulating urokinase plasminogen activator expression through suppressing the p38 MAPK-dependent NF-κB signaling pathway

Fisetin (3,3',4',7-tetrahydroxyflavone), a naturally occurring flavonoid, has been reported to inhibit proliferation and induce apoptosis in several cancer types. However, its effect on the anti-metastatic potential of cervical cancer cells remains unclear. In the present study, we found that fisetin inhibits the invasion and migration of cervical cancer cells. The expression and activity of urokinase plasminogen activator (uPA) was significantly suppressed by fisetin in a dose-dependent manner. We also demonstrated that fisetin reduces the phosphorylation of p38 MAPK, but not that of ERK1/2, JNK1/2, or AKT. Addition of a p38 MAPK inhibitor, SB203580, further enhanced the inhibitory effect of fisetin on the expression and activity of uPA and the invasion and motility in cervical cancer cells. Fisetin suppressed the TPA (tetradecanoylphorbol-13-acetate)-induced activation of p38 MAPK and uPA, and inhibited the TPA-enhanced migratory and invasive abilities. Furthermore, the promoter activity of the uPA gene was dramatically repressed by fisetin, which disrupted the nuclear translocation of NF-κB and its binding amount on the promoter of the uPA gene, and these suppressive effects could be further enhanced by SB203580. This study provides strong evidence for the molecular mechanism of fisetin in inhibiting the aggressive phenotypes by repression of uPA via interruption of p38 MAPK-dependent NF-κB signaling pathway in cervical cancer cells and thus contributes insight to the potential of using fisetin as a therapeutic strategy against cervical cancer by inhibiting migration and invasion.

Phytoalexins, miRNAs and breast cancer: a review of phytochemical-mediated miRNA regulation in breast cancer

There is growing interest in the diverse signaling pathways that regulate and affect breast tumorigenesis, including the role of phytochemicals and the emerging role of microRNAs (miRNAs). Recent studies demonstrate that miRNAs regulate fundamental cellular and developmental processes at the transcriptional and translational level under normal and disease conditions. While there is growing evidence to support the role of phytoalexin-mediated miRNA regulation of cancer, few reports address this role in breast cancer. Recent reports by our group and others demonstrate that natural products, including stilbenes, curcumin, and glyceollins, could alter the expression of specific miRNAs, which may lead to increased sensitivity of cancer cells to conventional anti-cancer agents and, therefore, hormone-dependent and hormone-independent tumor growth inhibition. This review will discuss how dietary intake of natural products, by regulating specific miRNAs, contribute to the prevention and treatment of breast cancer.

Invadopodia-associated proteins blockade as a novel mechanism for 6-shogaol and pterostilbene to reduce breast cancer cell motility and invasion

SCOPE

Invadopodia are actin-rich membrane protrusions of tumor cells that are thought to initiate the local migration and invasion during cancer metastasis. The blockade of invadopodia-associated proteins has been reported as a promising approach for prevention of tumor metastasis. The aim of this study was to investigate the modulatory effects of 6-shogaol and pterostilbene on invadopodia in aggressive breast cancer cells.

METHODS AND RESULTS

By wound-healing, transwell, and gelatin zymography assays, we found that 6-shogaol and pterostilbene effectively attenuated the motility and invasion of MDA-MB-231 cells, and suppressed the activities of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). Further investigation into the underlying molecular mechanisms revealed that the levels of key modulators of invadopodium maturation, including c-Src kinase, cortactin, and membrane type 1-matrix metalloproteinase (MT1-MMP) decreased when cells were treated with 6-shogaol or pterostilbene.

CONCLUSION

These data suggest that the repression of these factors might affect the maturation of invadopodia, inhibiting the metastasis of MDA-MB-231 cells. In conclusion, the present study demonstrates for the first time that 6-shogaol and pterostilbene can inhibit invadopodium formation and MMP activity in highly invasive breast cancer cells. We suggest that these compounds may be clinically useful in chemopreventive treatments for metastatic breast cancer.

Influence of berry polyphenols on receptor signaling and cell-death pathways: implications for breast cancer prevention

Breast cancer is the most commonly diagnosed cancer among women worldwide. Many women have become more aware of the benefits of increasing fruit consumption, as part of a healthy lifestyle, for the prevention of cancer. The mechanisms by which fruits, including berries, prevent breast cancer can be partially explained by exploring their interactions with pathways known to influence cell proliferation and evasion of cell-death. Two receptor pathways, estrogen receptor (ER) and tyrosine kinase receptors, especially the epidermal growth factor receptor (EGFR) family, are drivers of cell proliferation and play a significant role in the development of both primary and recurrent breast cancer. There is strong evidence to show that several phytochemicals present in berries such as cyanidin, delphinidin, quercetin, kaempferol, ellagic acid, resveratrol, and pterostilbene interact with and alter the effects of these pathways. Furthermore, they also induce cell death (apoptosis and autophagy) via their influence on kinase signaling. This review summarizes in vitro data regarding the interaction of berry polyphenols with the specific receptors and the mechanisms by which they induce cell death. This paper also presents in vivo data of primary breast cancer prevention by individual compounds and whole berries. Finally, a possible role for berries and berry compounds in the prevention of breast cancer and a perspective on the areas that require further research are presented.

Pterostilbene and cancer: current review

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is an antioxidant that is primarily found in blueberries. Studies suggest that pterostilbene exhibits the hallmark characteristics of an effective anticancer agent based on its antineoplastic properties in several common malignancies. In vitro models have shown that pterostilbene inhibits cancer growth through alteration of the cell cycle, induction of apoptosis, and inhibition of metastasis. In vivo, pterostilbene inhibits tumorigenesis and metastasis with negligible toxicity. Pterostilbene has also been shown to be effective as an inducer of antioxidant capacity in multiple cancer cell lines that may facilitate its function as an anticarcinogenic compound. Additionally, preliminary studies show that pterostilbene exhibits much greater bioavailability compared with other stilbene compounds; however the exact pharmacologic mechanism of pterostilbene and its effects in humans are still under investigation. In this review, we present a comprehensive summary of the antineoplastic mechanisms of pterostilbene based on the results of preclinical studies and highlight recent advances in the study of this dietary compound.

Pterostilbene inhibits colorectal aberrant crypt foci (ACF) and colon carcinogenesis via suppression of multiple signal transduction pathways in azoxymethane-treated mice

Pterostilbene (PS), a natural dimethylated analogue of resveratrol, is known to have diverse pharmacologic activities including anticancer, anti-inflammation, antioxidant, apoptosis, antiproliferation, and analgesic potential. This paper reports the inhibitory effect of dietary administration of pterostilbene against the formation of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) preneoplastic lesions and adenomas in male ICR mice and delineates its possible molecular mechanisms. ICR mice were given two AOM injections intraperitoneal and continuously fed a 50 or 250 ppm pterostilbene diet for 6 or 23 weeks. It was found that the dietary administration of pterostilbene effectively reduced AOM-induced formation of ACF and adenomas and inhibited the transcriptional activation of iNOS and COX-2 mRNA and proteins in mouse colon stimulated by AOM. Treatment with pterostilbene resulted in the induction of apoptosis in mouse colon. Moreover, administration of pterostilbene for 23 weeks significantly suppressed AOM-induced GSK3beta phosphorylation and Wnt/beta-catenin signaling. It was also found that pterostilbene significantly inhibited AOM-induced expression of VEGF, cyclin D1, and MMPs in mouse colon. Furthermore, pterostilbene markedly inhibited AOM-induced activation of Ras, phosphatidylinositol 3 kinase/Akt, and EGFR signaling pathways. All of these results revealed that pterostilbene is an effective antitumor agent as well as its inhibitory effect through the down-regulation of inflammatory iNOS and COX-2 gene expression and up-regulation of apoptosis in mouse colon, suggesting that pterostilbene is a novel functional agent capable of preventing inflammation-associated colon tumorigenesis.