Abstract C75: A novel multi-targeted Aurora A and VEGFR2 kinase inhibitor, ENMD-2076, demonstrates synergistic antiproliferative and proapoptotic effects in combination with chemotherapy and trastuzumab in breast cancer cell lines

Abstract

Abstract Introduction: ENMD-2076 is an orally bioavailable small molecule kinase inhibitor with antiproliferative activity via Aurora A kinase inhibition, and antiangiogenic activity via VEGFR2 inhibition. ENMD-2076 is being studied in a phase I clinical trial in advanced solid tumors and has demonstrated a tolerable side-effect profile. Due to the involvement of both Aurora A and angiogenic signaling pathways in breast cancer, we explored the combination of ENMD-2076 and chemotherapy or anti-HER2 therapy against a panel of breast cancer cell lines. Methods: Breast cancer cell lines were exposed to varying submicromolar concentrations of ENMD-2076 alone and in combination with carboplatin, docetaxel, or trastuzumab (HER2-overexpressing cell lines only). Proliferation was assessed using an SRB assay and analyzed using the Calcusyn program, whereby synergy was defined as a Combination Index of less than 1. FISH was performed to assess Aurora A gene amplification, VEGF concentrations were measured by ELISA, and apoptosis was analyzed using a caspase 3/7 assay. Results: The combination of ENMD-2076 and carboplatin resulted in synergistic inhibition of proliferation in both HER2 + (BT-474, SKBr3, ZR-75-30) and in triple negative (MDA 231, MDA 468) breast cancer cell lines. Likewise, ENMD-2076 and trastuzumab resulted in robust synergistic growth inhibition in HER2 + breast cancer cell lines. Synergy was not observed with the ENMD-2076 and docetaxel combination. FISH analysis demonstrated that tumor cells were sensitive to ENMD-2076 regardless of levels of Aurora A amplification. An increase in apoptosis that was maximal at 72 hours was observed with single agent ENMD-2076 and the combinations with carboplatin or trastuzumab. Similarly, VEGF concentrations were decreased in response to treatment with ENMD-2076 alone or in combination with the other agents. Discussion: These in vitro results demonstrate that ENMD-2076 acts synergistically with carboplatin to inhibit proliferation of triple negative breast cancer cell lines, and with both carboplatin and trastuzumab towards HER2+ breast cancer cell lines. This activity is associated with induction of cell death and reduction of VEGF secretion. These data are being confirmed in vivo using both trastuzumab-sensitive and trastuzumab-resistant xenograft models. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C75.