Annals of Oncology 25 (Supplement 4): iv546–iv563, 2014 doi:10.1093/annonc/mdu358.28
translational research 1597P
B.S. Karaca, Z. Surmeli, P. Gursoy, A.P. Erdogan, U.A. Sanli, R. Uslu Division of Medical Oncology, Ege University, School of Medicine,Tulay Aktas Oncology Hospital, Izmir, TURKEY
Aim: In the present study, we have investigated the possible synergistic cytotoxic and apoptotic effects of AT-101 in combination with trastuzumab in HER2-positive human breast cancer cell lines, MDA-MB-453 and SKBR3. We have further investigated the effect of the combination treatment on the PI3K signaling pathway to elucidate the molecular targets of the combination treatment.
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TRASTUZUMAB/AT-101 COMBINATION INDUCES APOPTOSIS AND SHOWS SYNERGISTIC CYTOTOXICITY IN HER2-POSITIVE BREAST CANCER CELLS BY INHIBITION OF PI3K SIGNALING: A NOVEL COMBINATION TO OVERCOME RESISTANCE TO ANTI-HER2 THERAPY
Methods: Cytotoxicity was assessed by XTT cell viability assay. Apoptosis was shown by using Cell Death Detection ELISA Plus Kit and verified by measuring caspase 3/7 enzyme activity. In order to investigate the molecular mechanism of combination treatment-induced apoptotic activity, cells were pretreated with PI3K inhibitor (LY294002) before Trastuzumab/AT-101 combination treatment, and then DNA fragmentation analysis was done. Western blot analysis was done to determine the changes in PI3K and Akt proteins. Results: Combination of trastuzumab with AT-101 showed strong synergistic cytotoxicity in both breast cancer cells at 72 h, compared with any agent alone. Combined treatment also induced DNA fragmentation and caspase 3/7 activation in breast cancer cells. PI3K inhibitor LY294002 inhibited the apoptotic effect of combination treatment in both breast cancer cell lines indicating that this combination inhibits the PI3K signaling pathway leading to apoptotic cell death. PI3K and Akt proteins were inhibited by the combination treatment with this novel combination. Conclusions: PI3K pathway is mostly found in Her-2 resistance; thus this novel combination of trastuzumab and AT-101 might be promising for overcoming anti-Her-2 resistance. Disclosure: All authors have declared no conflicts of interest.