Abstract 4548: High throughput siRNA screens uncover a high rate of USP8 and ESCRT pathway dependency in squamous carcinoma cell lines

USP8 and the ESCRT pathway (endosomal sorting complex required for transport) are required for cellular homeostasis through key functions in shuttling ubiquitinated proteins towards lysosomal degradation, and through regulating the maturation of autophagosomal structures. In large-scale siRNA screens, the vast majority of cancer cell lines do not demonstrate dependency on USP8 or ESCRT pathway components for viability. However, we identified three cell lines (HCC70, HCC1954 and PFSK1) that are acutely dependent on USP8 and other ESCRT components (HGS, TSG101) for viability. Using a transcriptome-wide association approach, we found that these three USP8-dependent cell lines also had in common the expression of SerpinB3, also known as SCCA1 (Squamous Cell Carcinoma Antigen 1). After selecting additional Squamous Cell Carcinoma cell lines for further validation of USP8-dependency by siRNA screening, we found that Squamous Carcinoma cell lines, irrespective of their SerpinB3 expression status, were far more likely to be dependent on USP8 for viability (23%; N = 22) than cancer cell lines of non-Squamous epithelial origin (4.5%; N = 67). To unravel possible molecular mechanisms underpinning the requirement of USP8 for the viability of USP8-dependent Squamous Carcinoma cell lines (including SCABER, BICR22, CALU1 and EBC1), we conducted additional transcriptome association studies and genetic interaction screens to uncover genes that are synthetic lethal with USP8 knock-down. Citation Format: Wendy Zhong, Elissa Cosgrove, Elissa Swearingen, Mike Ollmann, Jayee Banerjee, Vivienne Watson, Peter Jaeckel, Mariana Pfreimer, Silvia Materna-Reichelt, Holger Beckmann, Paul Kassner, Astrid Ruefli-Brasse, Olivier Nolan-Stevaux. High throughput siRNA screens uncover a high rate of USP8 and ESCRT pathway dependency in squamous carcinoma cell lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4548.