Genistein Suppresses v-Src-Driven Proliferative Activity by Arresting the Cell-Cycle at G2/M through Increasing p21 Level in Src-Activated Human Gallbladder Carcinoma cells.

Activated Src have been strongly implicated in the development, progression, and metastasis of many human cancers. Although soy isoflavones exhibit potential anticancer activity, effects of isoflavones on oncogenic activity of Src remains unknown. Using v-src-transfected human adenocarcinoma cells (HAG/src3-1), we investigated the functional role of Src in anti-proliferative activity of isoflavones including genistein, daidzein, glycitein and equol. The growth of HAG/neo3-5 vehicle control cells was inhibited potently by genistein and equol, but modestly by daidzein and glycitein. In contrast, Src activation conferred resistance to either daidzein, glycitein or equol, but rendered the cells more sensitive to genistein, compared to HAG/neo3-5 cells. Genistein significantly arrested HAG/src3-1 cells at G2/M, while neither daidzein, glycitein nor equol arrested the cells at any cell cycle phases. Apoptosis was not induced by either isoflavones. Genistein increased the expression levels of p53 and p21 with decreased phosphorylated p21, but did not affect the levels of major cyclin-CDK complexes. Taken together, genistein would be considered as the only isoflavone component that may potentially suppress Src-driven proliferative activity by arresting at G2/M induction through increasing the p21 levels, thus providing the mechanistic rationale for the potential use of genistein for the prevention of human cancers with activated Src.

Equol Enhances Apoptosis-inducing Activity of Genistein by Increasing Bax/Bcl-xL Expression Ratio in MCF-7 Human Breast Cancer Cells.

Anticancer activities of soy isoflavones, such as genistein and equol, a bioactive metabolite of daidzein, have been extensively studied because of possible involvement in the prevention of breast cancer. However, their interactions still remain unclear. We investigated here whether cytotoxic activity of genistein was enhanced by equol, using estrogen receptor positive MCF-7, HER2-positive SK-BR-3, and triple-negative MDA-MB-468 cell lines. Although cytotoxicity of genistein did not significantly differ between three subtypes of breast cancer cells, cytotoxic activities of genistein were significantly enhanced in combination with 50 µM equol in MCF-7 cells, but not in SK-BR-3 and MDA-MB-468 cells. In fluorescence activated cell sorting (FACS) analyses, MCF-7 cells were arrested at the G2/M by genistein but at G1/S by equol. Combination treatment arrested cells at G2/M but abolished equol-induced G1 block, indicating an antagonistic activity of genistein against equol in cell-cycle progression. Although apoptosis was not so evident with genistein alone, the combination made a drastic induction of apoptosis, accompanied by the increase of Bax/Bcl-xL expression ratio, without affecting the activities of Akt and mTOR. Taken together, these data suggest that enhancement of genistein activity by equol would be mainly mediated by augmented induction of apoptosis rather than arrest or delay of the cell cycle.

Differential Anticancer Activity of Pterostilbene Against Three Subtypes of Human Breast Cancer Cells.

Although pterostilbene, a natural analog of resveratrol, has potent antitumor activity against several human cancer types, the possible inhibitory mechanisms against subtypes of human breast cancer with different hormone receptor and human epidermal growth factor receptor 2 (HER2) status remain unknown. We investigated the anticancer activity of pterostilbene using three subtypes of breast cancer cell lines. Pterostilbene treatment exhibited a dose-dependent antiproliferative activity, with the greatest growth inhibition observed in triple-negative MDA-MB-468 cells. Although pterostilbene arrested cell-cycle progression at the G0/G1 phase regardless of breast cancer subtype, its apoptosis-inducing activity was highly apparent in MDA-MB-468 cells. Pterostilbene induced strong and sustained activation of extracellular signal-regulated kinase (ERK) 1/2, with concomitant cyclin D1 suppression and p21 up-regulation, and inhibited the phosphorylation of AKT and mammalian target of rapamycin (mTOR), followed by subsequent up-regulation of BAX without affecting B-cell lymphoma-extra large (BCL-xL). Oral administration of pterostilbene significantly suppressed tumor growth in nude mice xenotransplanted with MDA-MB-468 cells. These data suggest a potential role of pterostilbene for prevention and treatment of human breast cancer, especially of triple-negative breast cancer.

Anti-proliferative and apoptosis-inducing activity of lycopene against three subtypes of human breast cancer cell lines.

Although lycopene, a major carotenoid component of tomatoes, has been suggested to attenuate the risk of breast cancer, the underlying preventive mechanism remains to be determined. Moreover, it is not known whether there are any differences in lycopene activity among different subtypes of human breast cancer cells. Using ER/PR positive MCF-7, HER2-positive SK-BR-3 and triple-negative MDA-MB-468 cell lines, we investigated the cellular and molecular mechanism of the anticancer activity of lycopene. Lycopene treatment for 168 consecutive hours exhibited a time-dependent and dose-dependent anti-proliferative activity against these cell lines by arresting the cell cycle at the G0 /G1 phase at physiologically achievable concentrations found in human plasma. The greatest growth inhibition was observed in MDA-MB-468 where the sub-G0 /G1 apoptotic population was significantly increased, with demonstrable cleavage of PARP. Lycopene induced strong and sustained activation of the ERK1/2, with concomitant cyclin D1 suppression and p21 upregulation in these three cell lines. In triple negative cells, lycopene inhibited the phosphorylation of Akt and its downstream molecule mTOR, followed by subsequent upregulation of proapoptotic Bax without affecting anti-apoptotic Bcl-xL. Taken together, these data indicate that the predominant anticancer activity of lycopene in MDA-MB-468 cells suggests a potential role of lycopene for the prevention of triple negative breast cancer.

Differential anti-tumor activities of curcumin against Ras- and Src-activated human adenocarcinoma cells.

Although curcumin has been studied as a potential anticancer drug targeting multiple signaling molecules, the role of oncogenic Src and Ras in curcumin sensitivity remains unknown. Using HAG-1 human adenocarcinoma cells transfected with either activated Src or Ras, we investigated here the functional role of these oncogenes in curcumin sensitivity. Activation of either Src or Ras did not confer resistance to curcumin, compared to vehicle-transfected cells. Curcumin enhanced Erk1/2 predominantly in Ras-activated cells, but inhibited Akt and its downstream molecules (mTOR and S6K1) regardless of these oncogene activations. The sub-G0/G1 apoptotic populations were substantially increased with demonstrable cleavage of PARP, but this increase was most prominent in Src-activated cells. Suppression of Bcl-xL level and enhanced expression of Bax were demonstrated in Src-activated, but not Ras-activated cells. By contrast, drastic increases of G2/M cell populations were seen in Ras-activated cells rather than Src-activated cells, suggesting a potential role of Ras/Erk1/2 activation in curcumin-induced G2/M arrest. These data indicate that curcumin-induced growth inhibition would be mediated mainly by G2/M arrest in Ras-driven cells but by apoptosis induction in Src-driven cells, providing a mechanistic rationale for the potential use of curcumin in the treatment of human cancers with activated Src or Ras.

Antiproliferative and apoptosis-inducing activity of curcumin against human gallbladder adenocarcinoma cells.

AIM: Curcumin has potent antitumor activity against many types of human cancers. However, the inhibitory effects and possible mechanisms of curcumin on gallbladder cancer remains to be determined. MATERIALS AND METHODS: Using HAG-1 human gallbladder adenocarcinoma cells, we investigated the effects of curcumin on cell proliferation, apoptosis, cell-cycle perturbation, and signal proteins for survival, proliferation, and apoptosis. RESULTS: Curcumin exhibited dose-dependent antitumor activity against HAG-1 cells, arresting the cells in G2/M phase, with progressive expansion of the apoptotic cell population. Upon curcumin treatment, AKT activation was substantially suppressed, with subsequent reduction of activities of mammalian target of rapamycin (mTOR) and its downstream molecules S6 kinase-1 (S6K1) and elF4E-binding protein-1 (4E-BP1), but constitutive activity of extracellular signal-regulated kinase (ERK1/2) was clearly enhanced. Curcumin reduced the expression and phosphorylation of anti-apoptotic Bcl-2, but did not affect the expressions of pro-apoptotic Bax and anti-apoptotic nuclear factor (NF-κB). CONCLUSION: These results suggest that curcumin induces G2/M arrest and apoptosis through multiple mechanisms involving enhanced mitogen-activated protein (MAP) kinase activity, reduced AKT-mTOR activity, and reduced Bcl-2 function. These data provide a mechanistic rationale for the potential use of curcumin in the treatment of gallbladder cancer.