Mohamed R. Akl

Olive Phenolics as c-Met Inhibitors: (-)-Oleocanthal Attenuates Cell Proliferation, Invasiveness, and Tumor Growth in Breast Cancer Models

Dysregulation of the Hepatocyte growth factor (HGF)/c-Met signaling axis upregulates diverse tumor cell functions, including cell proliferation, survival, scattering and motility, epithelial-to-mesenchymal transition (EMT), angiogenesis, invasion, and metastasis. (-)-Oleocanthal is a naturally occurring secoiridoid from extra-virgin olive oil, which showed antiproliferative and antimigratory activity against different cancer cell lines. The aim of this study was to characterize the intracellular mechanisms involved in mediating the anticancer effects of (-)-oleocanthal treatment and the potential involvement of c-Met receptor signaling components in breast cancer. Results showed that (-)-oleocanthal inhibits the growth of human breast cancer cell lines MDA-MB-231, MCF-7 and BT-474 while similar treatment doses were found to have no effect on normal human MCF10A cell growth. In addition, (-)-oleocanthal treatment caused a dose-dependent inhibition of HGF-induced cell migration, invasion and G1/S cell cycle progression in breast cancer cell lines. Moreover, (-)-oleocanthal treatment effects were found to be mediated via inhibition of HGF-induced c-Met activation and its downstream mitogenic signaling pathways. This growth inhibitory effect is associated with blockade of EMT and reduction in cellular motility. Further results from in vivo studies showed that (-)-oleocanthal treatment suppressed tumor cell growth in an orthotopic model of breast cancer in athymic nude mice. Collectively, the findings of this study suggest that (-)-oleocanthal is a promising dietary supplement lead with potential for therapeutic use to control malignancies with aberrant c-Met activity.

Potential role of tocotrienols in the treatment and prevention of breast cancer.

Vitamin E is a generic term that refers to a family of compounds that is further divided into two subgroups called tocopherols and tocotrienols. Although all natural forms of vitamin E display potent antioxidant activity, tocotrienols are significantly more potent than tocopherols in inhibiting tumor cell growth and viability, and anticancer activity of tocotrienols is mediated independently of their antioxidant activity. In addition, the anticancer effects of tocotrienols are observed using treatment doses that have little or no effect on normal cell function or viability. This review will summarize experimental studies that have identified the intracellular mechanism mediating the anticancer effects of tocotrienols. Evidence is also provided showing that combined treatment of tocotrienol with other cancer chemotherapies can result in a synergistic inhibition in cancer cell growth and viability. Taken together, these findings strongly indicate that tocotrienols may provide significant health benefits in the prevention and/or treatment of cancer when used either alone as monotherapy or in combination with other anticancer agents.

Sesamin synergistically potentiates the anticancer effects of γ-tocotrienol in mammary cancer cell lines.

γ-Tocotrienol and sesamin are phytochemicals that display potent anticancer activity. Since sesamin inhibits the metabolic degradation of tocotrienols, studies were conducted to determine if combined treatment with sesamin potentiates the antiproliferative effects of γ-tocotrienol on neoplastic mouse (+SA) and human (MCF-7 and MDA-MB-231) mammary cancer cells. Results showed that treatment with γ-tocotrienol or sesamin alone induced a significant dose-responsive growth inhibition, whereas combination treatment with these agents synergistically inhibited the growth of +SA, MCF-7 and MDA-MB-231 mammary cancer cells, while similar treatment doses were found to have little or no effect on normal (mouse CL-S1 and human MCF-10A) mammary epithelial cell growth or viability. However, sesamin synergistic enhancement of γ-tocotrienol-induced anticancer effects was not found to be mediated from a reduction in γ-tocotrienol metabolism. Rather, combined treatment with subeffective doses of γ-tocotrienol and sesamin was found to induce G1 cell cycle arrest, and a corresponding decrease in cyclin D1, CDK2, CDK4, CDK6, phospho-Rb, and E2F1 levels, and increase in p27 and p16 levels. Additional studies showed that the antiproliferative effect of combination treatment did not initiate apoptosis or result in a decrease in mammary cancer cell viability. Taken together, these findings indicate that the synergistic antiproliferative action of combined γ-tocotrienol and sesamin treatment in mouse and human mammary cancer cells is cytostatic, not cytotoxic, and results from G1 cell cycle arrest.

Tocotrienol combination therapy results in synergistic anticancer response.

Vitamin E represents a family of compounds that is divided into two subgroups called tocopherols and tocotrienols, which act as important antioxidants that regulate peroxidation reactions and control free-radical production within the body. However, many of the biological effects of vitamin E are mediated independently of its antioxidant activity. Although tocopherols and tocotrienols have the same basic chemical structure characterized by a long phytyl chain attached to a chromane ring, only tocotrienols display potent anticancer activity, by modulating multiple intracellular signaling pathways associated with tumor cell proliferation and survival, and combination therapy with other chemotherapeutic agents result in a synergistic anticancer response. Combination therapy is most effective when tocotrienols are combined with agents that have complementary anticancer mechanisms of action. These findings strongly suggest that the synergistic antiproliferative and apoptotic effects demonstrated by combined low dose treatment of γ-tocotrienol with other chemotherapeutic agents may provide significant health benefits in the prevention and/or treatment of breast cancer in women, while at the same time avoiding tumor resistance and toxic side effects associated with high dose monotherapy.

Molecular and clinical significance of fibroblast growth factor 2 (FGF2 /bFGF) in malignancies of solid and hematological cancers for personalized therapies

Fibroblast growth factor (FGF) signaling is essential for normal and cancer biology. Mammalian FGF family members participate in multiple signaling pathways by binding to heparan sulfate and FGF receptors (FGFR) with varying affinities. FGF2 is the prototype member of the FGF family and interacts with its receptor to mediate receptor dimerization, phosphorylation, and activation of signaling pathways, such as Ras-MAPK and PI3K pathways. Excessive mitogenic signaling through the FGF/FGFR axis may induce carcinogenic effects by promoting cancer progression and increasing the angiogenic potential, which can lead to metastatic tumor phenotypes. Dysregulated FGF/FGFR signaling is associated with aggressive cancer phenotypes, enhanced chemotherapy resistance and poor clinical outcomes. In vitro experimental settings have indicated that extracellular FGF2 affects proliferation, drug sensitivity, and apoptosis of cancer cells. Therapeutically targeting FGF2 and FGFR has been extensively assessed in multiple preclinical studies and numerous drugs and treatment options have been tested in clinical trials. Diagnostic assays are used to quantify FGF2, FGFRs, and downstream signaling molecules to better select a target patient population for higher efficacy of cancer therapies. This review focuses on the prognostic significance of FGF2 in cancer with emphasis on therapeutic intervention strategies for solid and hematological malignancies.

Mechanisms mediating the synergistic anticancer effects of combined γ-tocotrienol and sesamin treatment.

Epidemiological studies have highlighted the ability of phytochemicals to reduce the risk of breast cancer by attenuating specific intracellular signaling pathways that regulate cell proliferation and survival. γ-Tocotrienol is a natural form of vitamin E that displays potent anticancer activity at doses that have no discernible toxicity toward normal cells. Sesamin is an abundant phytochemical found in sesame seed oil that also shows antiproliferative and antiangiogenic activity against human breast cancer cells. In this study, the combined treatment of subeffective doses of γ-tocotrienol and sesamin caused a synergistic inhibition of murine +SA mammary epithelial cell growth, as determined by the MTT assay and immunofluorescent Ki-67 staining. Western blot studies revealed that combined low-dose treatment of γ-tocotrienol and sesamin caused a marked reduction in EGF-induced ErbB3 and ErbB4 receptors phosphorylation (activation) and a relatively large decrease in intracellular levels of total and/or phosphorylated c-Raf, MEK1/2, ERK1/2, PI3K, PDK1, Akt, p-NFκB, Jak1, Jak2, and Stat1, as compared to cells treated with only one compound or in the vehicle-treated control group. These findings demonstrate that the synergistic growth inhibitory effects of γ-tocotrienol and sesamin treatment are associated with suppression of EGF-dependent mitogenic signaling in mammary tumor cells and suggest that dietary supplementation with these phytochemicals may provide some benefits in the prevention and/or treatment of breast cancer.

Discovery, Optimization, and Pharmacophore Modeling of Oleanolic Acid and Analogues as Breast Cancer Cell Migration and Invasion Inhibitors Through Targeting Brk/Paxillin/Rac1 Axis

Bioassay‐guided fractionation of Terminalia bentzoe L. leaves methanol extract identified the known triterpene oleanolic acid (1) as its major breast cancer cell migration inhibitor. Further chemical optimization afforded five new (9–12 and 15) and seven known (4–8, 13, and 14) semisynthetic analogues. All compounds were tested for their ability to inhibit human breast cancer MDA‐MB‐231 cells migration, proliferation, and invasion. The results revealed that 3‐O‐[N‐(3′‐chlorobenzenesulfonyl)‐carbamoyl]‐oleanolic acid (11) and 3‐O‐[N‐(5′‐fluorobenzenesulfonyl)‐carbamoyl]‐oleanolic acid (12) were the most active hits at low μm concentration. Western blot analysis indicated the activity of 1, 11, and 12 might be related, at least in part, to the suppression of Brk/Paxillin/Rac1 signaling pathway. Pharmacophore modeling study was conducted to better understand the common structural binding epitopes important for the antimigratory activity. The sulfonyl carbamoyl moiety with an optimal bulkiness electron‐deficient phenyl ring is associated with improved activity. This study is the first to discover the antimigratory and anti‐invasive activities of oleanolic acid and analogues through targeting the Brk/Paxillin/Rac1 axis.

Molecular and clinical profiles of syndecan-1 in solid and hematological cancer for prognosis and precision medicine

Syndecan-1 (SDC1, CD138) is a key cell surface adhesion molecule essential for maintaining cell morphology and interaction with the surrounding microenvironment. Deregulation of SDC1 contributes to cancer progression by promoting cell proliferation, metastasis, invasion and angiogenesis, and is associated with relapse through chemoresistance. SDC1 expression level is also associated with responses to chemotherapy and with prognosis in multiple solid and hematological cancers, including multiple myeloma and Hodgkin lymphoma. At the tissue level, the expression levels of SDC1 and the released extracellular domain of SDC1 correlate with tumor malignancy, phenotype, and metastatic potential for both solid and hematological tumors in a tissue-specific manner. The SDC1 expression profile varies among cancer types, but the differential expression signatures between normal and cancer cells in epithelial and stromal compartments are directly associated with aggressiveness of tumors and patients clinical outcome and survival. Therefore, relevant biomarkers of SDC signaling may be useful for selecting patients that would most likely respond to a particular therapy at the time of diagnosis or perhaps for predicting relapse. In addition, the reciprocal expression signature of SDC between tumor epithelial and stromal compartments may have synergistic value for patient selection and the prediction of clinical outcome.

Araguspongine C induces autophagic death in breast cancer cells through suppression of c-Met and HER2 receptor tyrosine kinase signaling.

Receptor tyrosine kinases are key regulators of cellular growth and proliferation. Dysregulations of receptor tyrosine kinases in cancer cells may promote tumorigenesis by multiple mechanisms including enhanced cell survival and inhibition of cell death. Araguspongines represent a group of macrocyclic oxaquinolizidine alkaloids isolated from the marine sponge Xestospongia species. This study evaluated the anticancer activity of the known oxaquinolizidine alkaloids araguspongines A, C, K and L, and xestospongin B against breast cancer cells. Araguspongine C inhibited the proliferation of multiple breast cancer cell lines in vitro in a dose-dependent manner. Interestingly, araguspongine C-induced autophagic cell death in HER2-overexpressing BT-474 breast cancer cells was characterized by vacuole formation and upregulation of autophagy markers including LC3A/B, Atg3, Atg7, and Atg16L. Araguspongine C-induced autophagy was associated with suppression of c-Met and HER2 receptor tyrosine kinase activation. Further in-silico docking studies and cell-free Z-LYTE assays indicated the potential of direct interaction between araguspongine C and the receptor tyrosine kinases c-Met and HER2 at their kinase domains. Remarkably, araguspongine C treatment resulted in the suppression of PI3K/Akt/mTOR signaling cascade in breast cancer cells undergoing autophagy. Induction of autophagic death in BT-474 cells was also associated with decreased levels of inositol 1,4,5-trisphosphate receptor upon treatment with effective concentration of araguspongine C. In conclusion, results of this study are the first to reveal the potential of araguspongine C as an inhibitor to receptor tyrosine kinases resulting in the induction of autophagic cell death in breast cancer cells.

Combined γ-tocotrienol and Met inhibitor treatment suppresses mammary cancer cell proliferation, epithelial-to-mesenchymal transition and migration

Dysregulation of Met signalling is associated with malignant transformation. Combined treatment has been shown to reduce Met activation and mammary tumour cell proliferation. Experiments here, were conducted to determine mechanisms involved in mediating anti‐cancer effects of combined γ‐tocotrienol and SU11274 (Met inhibitor) treatment in various mammary cancer cell lines.