Abstract 3486: Novel cell models of ovarian cancer for target discovery and validation obtained through stem cell culturing technology

Abstract

Abstract Introduction: Ovarian cancer is the leading cause of death from gynecological malignancies with greater than 50% of patients succumbing to the disease within 5 years of initial diagnosis. Contributors to the overall poor survival rate include late diagnosis, development of drug resistance and persistence of cancer stem cell (CSC) populations. With increasing evidence that CSC drive tumor initiation and metastases, development of model systems to better characterize such populations are needed. We recently reported use of stem cell culturing conditions to generate cancer stem like cells (CSLC) from colon and lung cancer that exhibit CSC properties (1-2). Here we apply a similar approach to ovarian cancer. Methodology: Freshly resected ovarian cancer tissue was obtained, processed and cultured using serum-free defined culture media evolved from conditions previously employed to culture tissue-specific progenitor stem cells. Expanded cell lines were characterized for their tumor initiating properties in NSG mice upon implantation under the sub-renal capsule. Xenografts were analyzed by H&E and immunostaining with ovarian cancer associated markers. Cell surface protein profile was examined by flow cytometry using mAbs against putative CSC markers and with those generated through de novo whole cell immunization of the putative ovarian cancer stem cell lines. Results: Ovarian CSLC were successfully cultured from independent serous ovarian tumor specimens. These lines can be indefinitely passaged in vitro while retaining ability to form tumors that faithfully recapitulate original patient tumor morphology and metastasize. The CSLC express EpCAM consistent with their epithelial origin and both CD44 and CD133. Analyses of mAbs generated from whole cell immunization identified B7-H3 as an additional target expressed on the ovarian CSLC. IHC analyses demonstrated B7-H3 expression also on primary and metastatic ovarian CSLC xenografts consistent with expression observed on patient derived specimens. Conclusion: Ovarian cancer cell lines have been generated using conditions previously established for tissue stem cells. These lines, which can be maintained indefinitely in vitro while retaining cancer stem cell properties, provide opportunity to identify and characterize novel ovarian cancer targeting strategies such as those designed against B7-H3.