Ovarian cancers with low CIP2A tumor expression constitute an APR-246 sensitive disease subtype

Identification of ovarian cancer (OvCa) patient subpopulations with increased sensitivity to targeted therapies could offer significant clinical benefit. We report that 22 % of the high grade OvCa tumors at diagnosis express CIP2A oncoprotein at low levels. Further, regardless of their significantly lower likelihood of disease relapse after standard chemotherapy, a portion of relapsed tumors retain their CIP2A-deficient phenotype. Through a screen for therapeutics that would preferentially kill CIP2A-deficient OvCa cells, we identified reactive oxygen species inducer APR-246, tested previously in OvCa clinical trials. Consistent with CIP2A-deficient OvCa subtype in humans, CIP2A is dispensable for development of MISIIR-Tag-driven mouse OvCa tumors. Nevertheless, CIP2A null OvCa tumor cells from MISIIR-Tag mice displayed APR-246 hypersensitivity both in vitro and in vivo. Mechanistically, the lack of CIP2A expression hypersensitizes the OvCa cells to APR-246 by inhibition of NF-kB activity. Accordingly, combination of APR-246 and NF-kB inhibitor compounds strongly synergized in killing of CIP2A positive OvCa cells. Collectively, the results warrant consideration of clinical testing of APR-246 for CIP2A-deficient OvCa tumor subtype patients. Results also reveal CIP2A as a candidate APR-246 combination therapy target for ovarian cancer. Three variants of HEY ovarian cancer cell lines were analyzed in triplicates (rep). The variants include the parental cell line (HEY), stable cell line expressing scrambled shRNA (HEY_NS_shRNA_520) and cell line expressing CIP2A targeted shRNA (HEY_shCIP2A_556).