Fak Inhibition Resensitizes Platinum-Resistant Serous Ovarian Cancer

Platinum and taxol administration is standard of care chemotherapy for serous ovarian cancer. Tumor recurrence occurs in a high percentage of patients, and this is directly related to poor overall survival. Ovarian cancer stem cell (CSC) resistance to chemotherapy treatment can give rise to tumor recurrence. Focal adhesion kinase (FAK), an intracellular tyrosine kinase, has been linked to mesothelioma and breast CSC survival. Here, we find that FAK activation is elevated in platinum (CP)-resistant ovarian cancer cells and that FAK tyrosine phosphorylation is increased after CP treatment of CP-sensitive ovarian cancer cells. Nanomolar levels of FAK inhibitor (VS-4718) selectively blocked CP-resistant ovarian carcinoma methylcellulose colony growth via cell cycle inhibition but not apoptosis. Oral VS-4718 administration to mice reduces CP-resistant orthotopic tumor burden with a concomitant decrease in tumor-associated aldehyde dehydrogenase (ALDH) activity, a marker of ovarian CSCs. Residual ovarian tumor cells from VS-4718-treated mice exhibit reduced ALDH activity and secondary tumor initiating capacity. CRISPR-mediated FAK knockout or VS-4718 treated ovarian carcinoma cells exhibit diminished Oct-4 transcription factor and ALDH-1A1 CSC-associated protein marker expression. Co-administration of VS-4718 with CP-taxol chemotherapy reduced CP-resistant tumor burden and exhibited additive inhibitory effects on ovarian carcinoma spheroid growth. As we find that CP activates FAK and that FAK activity sustains ovarian carcinoma CSC phenotypes, our results support the testing of FAK inhibitors in combination with CP to prevent recurrent and chemo-resistant ovarian cancer. Citation Format: Lisa M. Bean, Florian J. Sulzmaier, Isabelle Tancioni, Sean Uryu, Christine Jean, Christine Lawson, Xiao Lei Chen, Elizabeth G. Kleinschmidt, Kristen M. Anderson, Edward A. Cordasco, Joshua Axelrod, Vihren N. Kolev, Jonathan A. Pachter, Dwayne G. Stupack, David D. Schlaepfer. FAK inhibition resensitizes platinum-resistant serous ovarian cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3812.