Abstract 2956: High throughput RNAi screening of synthetic lethal genes interacting with the common TP53 mutation R175H

Abstract

Abstract The R175H mutation of p53 which account for approximately 6% of the missense mutations of identified in human cancer is one of the most common mutations, and cancer cells with this mutation stably express the R175H protein in the nucleus. Targeting R175H overexpressing cells by synthetic lethality is one of the extremely effective strategies for cancer therapy. To identify the synthetic lethal gene interacting with R175H, we conducted high throughput screening using a tetracycline-inducible R175H expression system in SF126 cells and comprehensive shRNA library carried by lentivirus. We identified 906 candidate gene suppressions that may lead to accelerated cell growth inhibition in the presence of R175H (p<0.05, n=3). Among these, we selected 50 genes (21 genes from the group with the smallest p-values, 20 genes from the group with the largest fold change, and 9 genes reproduced by different siRNA sequences) for further validation testing. By transfection of siRNA of these candidate genes into five R175H expressing cell lines and four TP53-null cell lines, we selected five candidate genes that significantly lead R175H expressing cells to strong cell growth inhibition. Inhibitor of differentiation 1 (ID1) was one of the five candidate genes, and its suppression by siRNA resulted in the acceleration of growth inhibition in cell lines expressing endogenous R175H; however, this was not observed in TP53-null cell lines. The transient expression of R175H in TP53-null cell lines (PC3) and suppression of ID1 and/or TP53 R175H in cell lines with endogenous R175H revealed that cell growth inhibition by ID1 suppression depended on the expression of R175H, and not that of other common p53 mutants (e.g., R273H). Flow cytometric analysis exhibited that ID1 suppression resulted in G1 arrest, and the arrest was accelerated by the expression of R175H. In conclusion, ID1 is a synthetic lethal gene that interacts with R175H and is considered to be a novel molecular target for cancer therapy in R175H expressing cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2956. doi:1538-7445.AM2012-2956