KDM6B modulates MAPK pathway mediating multiple myeloma cell growth and survival

Recent studies have delineated cancer type-specific roles of histone 3 lysine 27 (H3K27) demethylase KDM6B/JMJD3 depending on its H3K27 demethylase activity. Here we show that KDM6B is expressed in multiple myeloma (MM); and that shRNA-mediated knockdown and CRISPR-mediated knockout of KDM6B abrogate MM cell growth and survival. TNFα or bone marrow stromal cell culture supernatants induce KDM6B, which is blocked by IKKβ inhibitor MLN120B, suggesting KDM6B is regulated by NF-κB signaling in MM cells. RNA-sequencing and subsequent ChIP-qPCR analyses reveal that KDM6B is recruited to the loci of genes encoding components of MAPK signaling pathway including ELK1 and FOS, and upregulates these genes expression without affecting H3K27 methylation level. Overexpression of catalytically-inactive KDM6B activates expression of MAPK pathway-related genes, confirming its function independent of demethylase activity. We further demonstrate that downstream targets of KDM6B, ELK1 and FOS, confer MM cell growth. Our study therefore delineates KDM6B function that links NF-κB and MAPK signaling pathway mediating MM cell growth and survival, and validates KDM6B as a novel therapeutic target in MM.