Epithelial tissues rely on a highly coordinated balance between self-renewal, proliferation, and differentiation, disruption of which may drive carcinogenesis. The epigenetic regulator () is one of the most frequently mutated genes in all cancers, particularly epithelial cancers, yet its normal function in these tissues is unknown. Here, we identify a novel role for KMT2D in coordinating this fine balance, as depletion of KMT2D from undifferentiated epidermal keratinocytes results in reduced proliferation, premature spurious activation of terminal differentiation genes, and disorganized epidermal stratification. Genome-wide, KMT2D interacts with p63 and is enriched at its target enhancers. Depletion of KMT2D results in a broad loss of enhancer histone modifications H3 Lys 4 (H3K4) monomethylation (H3K4me1) and H3K27 acetylation (H3K27ac) as well as reduced expression of p63 target genes, including key genes involved in epithelial development and adhesion. Together, these results reveal a critical role for KMT2D in the control of epithelial enhancers and p63 target gene expression, including the requirement of KMT2D for the maintenance of epithelial progenitor gene expression and the coordination of proper terminal differentiation.

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Mature B-cell neoplasms are the fifth most common neoplasm. Due to significant heterogeneity at the clinical and genetic levels, current therapies for these cancers fail to provide long-term cures. The clinical success of proteasome inhibition for the treatment of multiple myeloma and B-cell lymphomas has made the ubiquitin pathway an important emerging therapeutic target. In this study, we assessed the role of the E3 ligase FBXW7 in mature B-cell neoplasms. FBXW7 targeted the frequently inactivated tumor suppressor KMT2D for protein degradation, subsequently regulating gene expression signatures related to oxidative phosphorylation (OxPhos). Loss of FBXW7 inhibited diffuse large B-cell lymphoma cell growth and further sensitized cells to OxPhos inhibition. These data elucidate a novel mechanism of regulation of KMT2D levels by the ubiquitin pathway and uncover a role of FBXW7 in regulating oxidative phosphorylation in B-cell malignancies.Significance: These findings characterize FBXW7 as a prosurvival factor in B-cell lymphoma via degradation of the chromatin modifier KMT2D.

Human acute myeloid cell lines can be induced to differentiate into macrophage-like cells by phorbol esters. Differentiation is accompanied by cessation of cell proliferation and initiation of apoptosis. Many of these cell lines, like HL-60, are p53 deficient and therefore execute a differentiation-induced, p53-independent program of cell death. Evaluating changes in gene expression during a time course of PMA-induced HL-60 cell differentiation by DNA microarray analyses and RT-qPCR reveals up-regulation of several pro-apoptotic genes (ex. TNF, MCL1, EGR2, BCL3) and down-regulation of several anti-apoptotic genes (ex. BCL2, ANXA3, TSC22D3). Interestingly, RNA levels of p73 are unchanged, suggesting p73 does not substitute for the missing p53 function via activation of p73 gene transcription, however, we report here that p73 protein levels increase dramatically during the differentiation time course. By reintroducing p53 into HL-60 cells, we compare the changing gene expression profile during p53-mediated apoptosis versus that which occurs during phorbol ester-induced p73 accumulation through protein stabilization. Common and unique gene expression changes define the putative p73-dependent apoptosis program compared to p53-dependent apoptosis. Citation Format: Michael Roberts, Rizwan Saffie, Harold Salmons, Mansoor Ghoto, Juliana Schneider, Jeffrey Forrester. Differentiation induced apoptosis in AML cells: The role of p73 in p53-independent versus p53-mediated apoptosis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 346. doi:10.1158/1538-7445.AM2014-346