Browsing by Author "Cirak, Y"

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    Combined gossypol and zoledronic acid treatment results in synergistic induction of cell death and regulates angiogenic molecules in ovarian cancer cells
    Atmaca, H; Gorumlu, G; Karaca, B; Degirmenci, M; Tunali, D; Cirak, Y; Purcu, DU; Uzunoglu, S; Karabulut, B; Sanli, UA; Uslu, R
    In the present study, we aimed to evaluate the possible synergistic, cytotoxic effects of combination treatment of gossypol and zoledronic acid, in human ovarian cancer cell lines, OVCAR-3 and MDAH-2774, and to elucidate the role of this novel combination treatment on angiogenesis-related molecules in ovarian cancer. The XTT cell viability assay was used for showing cytotoxicity. Both DNA fragmentation by ELISA assay and caspase 3/7 activity measurement were used for demonstrating apoptosis. To elucidate the angiogenic molecules affected by combination treatment, mRNA levels of angiogenic molecules were measured using the Human Angiogenesis RT2 Profiler (TM) PCR Array (SuperArray, Frederick, MD) in ovarian cancer cell lines, OVCAR-3 and MDAH-2774. The combined treatment resulted in significant, synergistic cytotoxicity, and induced apoptosis. This effect was observed to happen in a dose- and time-dependent manner. Moreover, the combination treatment of 10 mu M gossypol and 5 mu M zoledronic acid resulted in significant down-regulation (>= thee-fold) in mRNA levels of some pivotal angiogenic molecules in OVCAR-3 and MDAH-2774 cells as compared to the untreated control. However, this effect was different in the two ovarian cancer cell lines observed. Gossypol, in combination with zoledronic acid, may provide a rational treatment option for ovarian cancer, not only by direct inhibition of cell proliferation, but also inhibition of angiogenesis-related molecules.
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    Zoledronic acid in combination with serine/threonine phosphatase inhibitors induces enhanced cytotoxicity and apoptosis in hormone-refractory prostate cancer cell lines by decreasing the activities of PP1 and PP2A
    Cirak, Y; Varol, U; Atmaca, H; Kisim, A; Sezgin, C; Karabulut, B; Uzunoglu, S; Uslu, R; Karaca, B
    OBJECTIVES To investigate if the cytotoxic and apoptotic effect of zoledronic acid (ZA) can be enhanced by the addition of the serine/threonine protein phosphatase inhibitors calyculin A (CA) and okadaic acid (OA) in hormone and drug refractory prostate cancer cells, PC-3 and DU-145. To discover the effect of these combination treatments on phosphatase 1 (PP1) and PP2A protein expression levels in prostate cancer cells. MATERIALS AND METHODS An XTT cell viability assay was used to determine cytotoxicity. Apoptosis was evaluated by enzyme-linked immunosorbent assay (ELISA) using a Cell Death Detection ELISA Plus Kit and verified by measuring caspase 3/7 enzyme activity. The PP1 and PP2A enzyme activities were evaluated by serine/threonine phosphatase ELISA and expression levels of PP1 and PP2A proteins were then re-assessed by Western blot analysis. RESULTS Combination of ZA with either CA or OA showed synergistic cytotoxicity and apoptosis compared with any agent alone in both PC-3 and DU-145 prostate cancer cells. The combination of ZA with phosphatase inhibitors resulted in enhanced suppression of both PP1 and PP2A enzyme activity and protein levels, which was more overt with the ZA/CA combination. CONCLUSION Results from our study increase the translational potential of our in vitro findings and offer the basic rationale for the design of new combinatory strategies with ZA and phosphatase inhibitors for the treatment of prostate cancer, which may become resistant to conventional therapy.