Targeting Loss of the Tumor Suppressor TENT5C in Multiple Myeloma

Introduction: Multiple myeloma (MM) is a genetically complex and heterogeneous neoplasm in which multiple genomic events lead to tumor development and progression. Loss of TENT5C through mutation or deletion on chromosome 1p occurs in more than 20% of newly diagnosed MM patients and is associated with a poor progression free and overall survival. Although, many studies have identified TENT5C as a tumor suppressor gene in MM, the impact of gene loss on MM physiopathology remain to be elucidated. Here we sought to identify drugs which may specifically target TENT5C-null MM cells using targeted and high-throughput drug screens (HTS). Methods: We generated CRISPR/Cas9 knockout (ko) of TENT5C in wild type (wt) U266 and KMS-11 MM cell lines and over-expressed (oe) TENT5C in MM cell lines with biallelic inactivation (H929 -/- and LP-1 -/-). Modified cell lines were compared to their original counterparts for gene expression, proliferation, and cell cycle differences. Targeted and HTS were performed to identify synthetic lethal pathways related to loss of TENT5C in MM that will result in specific cell death. Results: In TENT5Cko cells the RNA poly(A) polymerase activity was decreased at two TENT5C top targeted substrates, immunoglobulin kappa light chain and signal sequence receptor. Consistent with TENT5C tumor suppressor function, cell proliferation analysis showed that TENT5Cko cells had a higher growth rate than TENT5Cwt cells. Cell cycle analysis, after nocodazole synchronization, showed TENT5C-null cells had an increased G2/M population compared to TENT5C-positive cells (U266 TENT5Cko 19.86% vs. TENT5Cwt 2.6%, p