Determining the Effect of Residual SWI/SNF Subunits on Small Cell Carcinoma of the Ovary Hypercalcemic Type (SCCOHT) Cell Lines

Abstract

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare and aggressive cancer which has an exceptionally high mortality rate. The main mutation correlated with this cancer type impacts the proper functioning of a major chromatin remodeling complex called SWI/SNF. One commonality of all SCCOHT cancers is deleterious mutation of the SMARCA4 gene that is known to encode for the SWI/SNF ATPase subunit, BRG1. Loss of BRG1 incorporation within SWI/SNF is the driving mutational event to promote tumorigenesis, and it has been difficult to find new therapy options for patients with this type of cancer resulting in a low survival rate. In other cancers defined by SWI/SNF subunit mutations like SCCOHT, there is a reliance of the cancer state on the SWI/SNF subunits that remain present in the cell. Two proteins with important functions in the SWI/SNF chromatin remodeling complexes that remain following BRG1 loss are BAF155 and ARID1A. To interrogate whether these two remaining SWI/SNF subunits are important for SCCOHT cancer processes, I determined in my thesis work whether knockdown in expression levels of these SWI/SNF subunits has any detrimental impact on SCCOHT cell proliferation and cell cycle progression. To achieve this, I introduced a new CRISPR technique called CRISPR interference (CRISPRi) into the laboratory to target BAF155 and ARID1A subunit expression. Results from this research show that CRISPRi worked more successfully for targeting knockdown of BAF155. However, in contrast to my hypothesis, decreasing BAF155 levels did not impair cell division but rather induced a trend towards increased cell function. Overall, my thesis research has provided insight into the dependency of SCCOHT cell lines on a core SWI/SNF subunit and helped to define the optimal parameters for future CRISPRi-based research in the laboratory that will assist the uncovering of essential proteins in various cancer cell lines.