Abstract 2976: Intratumoral cellular heterogeneity of epithelial ovarian carcinoma and its impact on tumor behavior

One of the challenging features of cancer is intratumoral heterogeneity (ITH). The existence of ITH can have profound consequences on tumor progression and drug sensitivity. However it is been essentially impossible to monitor the extent to which individual clonal populations contribute to and affect tumor behavior because of our inability to culture tumor cells from patients in vitro without loosing initial heterogeneity resulting from clonal selection under culture conditions. Through our collaboration with Dr. Tan Ince, we have access to cell culture medium (WIT-OC media) that allows primary tumor cells to undergo continuous population doublings without selecting for or against specific clones under culture conditions. By utilizing this media we have generated 80 single cell clones from a Clear cell Carcinoma (CCC) patient sample and monitored the extent of phenotypic and genomic heterogeneity among 12 of the clonal populations. These clones showed striking heterogeneity in copy number alterations as well as phenotypic heterogeneity in vitro as assessed by anoikis, growth in soft agar, doubling time, and growth in 3D reconstituted basement membrane cultures. We also examined correlations between in vitro properties and tumor formation in vivo using clones tagged with Gaussia-Luciferase (Gluc), a secreted luciferase that is secreted from cells and can be assayed in whole blood. We found that only three clones were transplantable by themselves; however, the clone which showed the most rapid expansion in the mouse was limited in it tumorigenic capacity, generating only ascitic tumor populations. To address whether clonal heterogeneity could contribute to tumor progression, we transplanted mixtures of clones and utilized barcoded clones to analyze the clonal composition of tumor masses. Interestingly, mixtures of the 12 clones resulted in the generation of more aggressive tumors, including the formation of solid tumors and metastases to lungs, liver and brain and allow in vivo growth; these metastatic growths contain distinct mixtures of individual clonal populations. Moreover, clones that could not initiate tumor formation individually could generate metastatic tumors, suggesting that there is cooperativity between the clones to enhance growth and induce metastasis. The study has provided evidence that cell lines generated from individual clones vary significantly in their functional activities in vitro and in vivo. Moreover, by studying the single cell clones, we have found evidence for the existence of interclonal crosstalk during tumor progression and are currently studying the nature and impact of such crosstalk on tumor progression and metastasis. Citation Format: Suha Naffar-Abu Amara, Laura Selfors, Marit Krohn, Tan Ince, Gordon Mills, Joan Brugge. Intratumoral cellular heterogeneity of epithelial ovarian carcinoma and its impact on tumor behavior. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2976. doi:10.1158/1538-7445.AM2014-2976