Abstract P6-08-04: Preclinical efficacy of dasatinib in combination with PARP inhibitor plus standard cytotoxic agent in triple-negative breast cancer xenograft model

Abstract

Abstract Background: Dasatinib is an orally-active ATP-competitive small molecule kinase inhibitor that potently inhibits Abl kinase, Src family kinases and other kinases (Lombardo et al., 2004). Src, one of the key targets of dasatinib is involved in the regulation of cell proliferation, survival and apoptotic ability of cancer cells (Tryfonopoulos et al., 2011; Pusztai et al., 2014). Dasatinib has shown its anti-proliferative and anti-metastatic effectiveness against triple-negative breast cancer (TNBC) in both preclinical and clinical studies (Finn et al., 2011). Several molecular targets including poly ADP ribose polymerase (PARP) are under clinical investigation for the treatment of TNBC. Recently, PARP inhibitors in combination with chemotherapy have shown promising results in this disease in clinical and preclinical studies (Tutt et al., 2010; Kim et al., 2013; De et al., 2014). Here, we hypothesize that dasatinib in combination with PARP inhibitor (ABT888) plus standard cytotoxic agent (carboplatin) will attenuate the growth of both TNBC cell lines and xenograft tumors. Methodology:We have used BT-20 (PIK3CA mutated, H1047R), HCC70 (PTEN null), HCC1937 (BRCA1 mutated, PTEN null), MDA-MB-231 (KRAS/BRAF mutated), MDA-MB-468 (PTEN null) and SUM149PT (BRCA1 mutated, PTEN null) cells for in vitro study. Survival/proliferation, colony formation and apoptosis were examined by using 2D proliferative/growth assay, 3D-ON-TOP assays, and annexinV staining respectively. We next studied the activation status of Src and its downstream signaling. We also have evaluated the effects on tumor growth inhibition of dasatinib/ABT888/carboplatin as a single agent or in combination by using mouse xenograft model. Results: We observed that 1) Dasatinib inhibited Src activation in all tested lines, induced dephosphorylation of ERK1/2 and S6 RP; 2) level of Cyclin D1 was decreased by dasatinib treatment; 3) high anti-proliferative activities were observed following the treatment of dasatinib along with ABT888 plus carboplatin in both 2D proliferation assay and 3D-ON TOP colony formation assay; 4) dasatinib in combination with ABT888 plus carboplatin inducing early stage apoptosis was seen by Annexin V staining in all tested cell lines; 5) dasatinib alone or combined with ABT888 or carboplatin or in triple combination inhibited tumor growth in TNBC xenograft models, the best tumor inhibition result was induced by triple combination (comparing to no treatment control, the mean tumor volume was decreased ~ 87% ). Conclusion: Our in vitro and in vivo studies suggest that dasatinib may enhance the antitumor activity of PARP inhibitor plus standard cytotoxic agent in TNBC. Mechanistic studies of xenograft tumor samples are ongoing, the results of which will be presented in the meeting. Citation Format: Sun Y, Lin X, Carlson JH, De P, Dey N, Jepperson T, R & D NCI, Williams C, Leyland-Jones B. Preclinical efficacy of dasatinib in combination with PARP inhibitor plus standard cytotoxic agent in triple-negative breast cancer xenograft model [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-08-04.