Abstract 1560: In vivo CRISPR/Cas9 transcriptional activation screen leads to discovery of INAFM2, a novel driver of metastasis

Abstract Metastasis is the main cause of mortality in cancer patients and accounts for about 90% of cancer deaths, which has not changed in the past 50 years. This indicates a significant need for further study of metastasis pathways to find novel druggable targets. Ewing sarcoma (ES) is an aggressive childhood cancer that occurs in the bones or soft tissue. The five-year survival rate for Ewing sarcoma patients diagnosed with metastatic disease is still only 25%, making ES a good model for studying metastasis. We performed a genome-wide CRISPR/Cas9 transcriptional activation screen in a zebrafish xenograft model to discover genes whose activation leads to increased metastasis. The screen identified a number of genes that may accelerate ES metastasis; we chose INAFM2 for further study because multiple unique INAFM2-targeting gRNAs were enriched in the screen and we discovered a potential link to metastasis and patient survival in publicly available clinical data. Overexpression of INAFM2 in six different cancer cell lines (four ES, one hepatocellular carcinoma, and one stomach adenocarcinoma) caused increased cell migration and chemotaxis in vitro, and increased intravasation in zebrafish xenografts. INAFM2 knockdown in four cancer cell lines (two ES, one clear cell renal cell carcinoma, and one stomach adenocarcinoma) decreased chemotaxis and rescue of INAFM2 expression restored the cells’ ability to migrate. Analysis of patient tumor RNA sequencing data from many different types of cancers revealed correlations between INAFM2 expression and both an increased metastatic phenotype and poor patient survival. Further in vivo studies by tail vein injection of ES cells in immunodeficient mice demonstrated significantly increased gross metastases with INAFM2 overexpression and decreased gross metastases with INAFM2 knockdown compared to the respective control groups. This provides strong evidence for a substantial role of INAFM2 in cancer metastasis. Human INAFM2 is an unstudied gene and our preliminary work has revealed that the INAFM2 protein localizes to the cell membrane, is glycosylated, and may be involved in Wnt and/or MAPK pathway signaling. Inafm2 silencing by morpholino in zebrafish embryos lead to significant mortality, necrosis, and developmental delays/defects including severe cardiac edema. Current studies are focused on further discerning the molecular pathways that mediate the role of INAFM2 in promoting metastasis using in vitro and in vivo models as well as characterizing the functional significance of the direct protein binding partners and post-translational modifications for INAFM2. Citation Format: Anna Molotkova, Emre Deniz, Matthew Swift, Eric Glasgow, Jeffrey Toretsky, Aykut Üren. In vivo CRISPR/Cas9 transcriptional activation screen leads to discovery of INAFM2, a novel driver of metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1560.