Identification of WNK1 as a Therapeutic Target to Suppress IgH/MYC Expression in Multiple Myeloma

Abstract

Multiple myeloma (MM) remains an incurable hematological malignancy demanding innovative therapeutic strategies. Targeting MYC, the notorious yet traditionally undruggable oncogene, presents an appealing avenue. This thesis aims to identify and characterize novel regulators of MYC expression as therapeutic targets in MM. Using a genome-scale CRISPR/Cas9 screen, we identify the WNK lysine deficient protein kinase 1 (WNK1) as a regulator of MYC expression in MM cells. Genetic and pharmacological inhibition of WNK1 reduces MYC expression and, further, disrupts the MYC-dependent transcriptional program. Mechanistically, WNK1 inhibition attenuates the activity of the immunoglobulin heavy chain (IgH) enhancer, thus reducing MYC transcription when this locus is translocated near the MYC locus. Furthermore, we show in MM cells possessing distinct translocation profiles that WNK1 inhibition also downregulates other oncogenes frequently translocated near the IgH locus, including CCND1, FGFR3, and NSD2, broadening its potential therapeutic implications. WNK1 inhibition profoundly impacts MM cell behaviors, leading to growth inhibition, cell cycle arrest, senescence, and apoptosis. Importantly, the WNK inhibitor WNK463 inhibits MM growth in primary patient samples as well as xenograft mouse models, and exhibits synergistic effects with various anti-MM compounds. Collectively, this study uncovers WNK1 as a promising therapeutic target in MM, and suggests the utility of IgH translocations as useful biomarkers.