Abstract 821: Loss and retention of mutations in cell culture model systems
Authors: Shaw Pamela S. , Nicoletti Rick , Salimi Naghmeh , Yang Helen L. , Witt Abigail E. , Agoston Agoston T. , Agoston Elin S. 
Published: July 2017

Abstract
Although relevant, the genomic and proteomic alterations between original tumor tissue and newly established cell lines are frequently uncharacterized. In developing a novel cell model (Powder) of high grade serous carcinoma (HGSC), we followed the status of clinically relevant biomarkers to identify changes taking place between the tissue and cultured cell population. Understanding these changes enables proper utilization of new models and continued model optimization. Using a validated panel, we analyzed 592 genes in the Powder cell model and tumor from which it was derived, detecting several classes of genomic alterations. This included point mutations, indels, copy number variations, fusions, and variant transcripts. p53 mutation status of Powder was matched to a panel of previously reported HGSC cell lines. We further subdivided the panel by p53 protein expression level by reanalyzing previously published reverse phase protein array (RPPA) data. Significance of differential expression between groups was determined with a Welch's t-test. A majority (14/21 or 67%) of the mutations detected in the HGSC tumor were conserved in the Powder cell model. Two additional mutations, undetected in the tumor, were found in the cell model. The tumor exhibited moderate to strong diffuse positive p53 immunostaining, and p53 mutations were measured in 79% of alleles. While the p53 mutation did not carry to the cell model, the cells were positive for CK7 and PAX8, consistent with ovarian cancer cells. In the panel of HGSC cell lines, we examined p53 mutation status and protein level, identifying 3 groups: (1) p53-mut/high protein, (2) p53-mut/low protein and (3) p53-WT/low protein. Powder identified with the p53-WT/low protein group. Previous work identifies the p53-WT/low protein group of cell models as part of a larger set of novel ovarian cell models with a stem-like molecular profile and higher drug resistance. Analysis of differential protein expression revealed upregulation in the p53 low protein group of both normal cell cycle genes and of notable cancer-related proteins. This included p21 and BAD, which are upregulated in cells with functional p53, eIF4E, a candidate cancer therapeutic target, and BOP1, which is disregulated in multiple solid cancers, including ovarian. These results underscore the need for further characterization of the Powder cell model to clarify its applications to specific research questions. Continued examination of Powder and other p53-WT cell models derived from HGSC tumors may uncover independent pathways driving disease. Additionally, understanding which mutations are underrepresented by cell models is necessary for ongoing methods development.
Citation Format: Pamela S. Shaw, Rick Nicoletti, Naghmeh Salimi, Helen L. Yang, Abigail E. Witt, Agoston T. Agoston, Elin S. Agoston. Loss and retention of mutations in cell culture model systems [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 821. doi:10.1158/1538-7445.AM2017-821