The role of FAM46C in myeloma cells [array]

FAM46C is one of the most recurrently mutated genes in multiple myeloma (MM), however its role in disease pathogenesis is not determined. Here we demonstrate that wild type (WT) FAM46C overexpression induces substantial cytotoxicity in MM cells. In contrast, FAM46C mutations found in MM patients abrogate this cytotoxicity indicating a MM survival advantage conferred by the FAM46C mutant phenotype. WT FAM46C overexpression downregulated IRF4, CEBPB, MYC and upregulated immunoglobulin (Ig) light chain and HSPA5/BIP. Furthermore, pathway analysis suggests that enforced FAM46C expression activates the unfolded protein response (UPR) pathway and induces mitochondrial dysfunction. In contrast, endogenous CRISPR FAM46C depletion enhanced MM cell growth and notably decreasing Ig light chain and BIP expression, activating of ERK and anti-apoptotic signaling and conferring relative resistance to dexamethasone and lenalidomide treatment. The genes altered in FAM46C depleted cells are enriched for signaling pathways regulating estrogen, glucocorticoid, B cell receptor signaling and ATM signaling. Together these results implicate FAM46C in myeloma cell growth and survival. FAM46C mutation contributes to myeloma pathogenesis and disease progression by perturbation in plasma cell differentiation and endoplasmic reticulum homeostasis. To assess the gene expression changes induced by FAM46C depletion, three samples, including OCIMY5 cells harboring, respectively, control, FAM46C gRNA #1 and FAM46C #6 gRNA, were harvested and processed for gene expression analysis.