ABSTRACT
Inactivation of the von Hippel-Lindau (VHL) E3 ubiquitin ligase protein is a hallmark of clear cell renal cell carcinoma (ccRCC). Identifying how pathways affected by VHL loss contribute to ccRCC remains challenging. We used a genome-wide in vitro expression strategy to identify proteins that bind VHL when hydroxylated. Zinc fingers and homeoboxes 2 (ZHX2) was found as a VHL target, and its hydroxylation allowed VHL to regulate its protein stability. Tumor cells from ccRCC patients with VHL loss-of-function mutations usually had increased abundance and nuclear localization of ZHX2. Functionally, depletion of ZHX2 inhibited VHL-deficient ccRCC cell growth in vitro and in vivo. Mechanistically, integrated chromatin immunoprecipitation sequencing and microarray analysis showed that ZHX2 promoted nuclear factor κB activation. These studies reveal ZHX2 as a potential therapeutic target for ccRCC.
Subject(s)
Carcinoma, Renal Cell/genetics , Homeodomain Proteins/metabolism , Kidney Neoplasms/genetics , Oncogenes , Transcription Factors/metabolism , Von Hippel-Lindau Tumor Suppressor Protein/metabolism , Animals , Carcinoma, Renal Cell/drug therapy , Chromatin Immunoprecipitation , Female , Gene Expression Regulation, Neoplastic , Homeodomain Proteins/genetics , Humans , Hydroxylation , Kidney Neoplasms/drug therapy , Mice , Mice, SCID , Molecular Targeted Therapy , Mutation , NF-kappa B/metabolism , Substrate Specificity , Transcription Factors/genetics , Von Hippel-Lindau Tumor Suppressor Protein/geneticsABSTRACT
Enhancer of zeste homology 2 (EZH2) is the methyltransferase component of the polycomb repressive complex (PRC2) which represses gene transcription via histone H3 trimethylation at lysine 23 (H3K27me3). EZH2 activity has been linked with oncogenesis where it is thought to block expression of certain tumor suppressors. Relative to a role in cancer, EZH2 functions to promote self-renewal and has been shown to be important for the tumor-initiating cell (TIC) phenotype in breast cancer. Recently a non-canonical role for EZH2 has been identified where it promotes transcriptional activation of certain genes. Here we show that EZH2, through a methyltransferase-independent mechanism, promotes the transcriptional activation of the non-canonical NF-κB subunit RelB to drive self-renewal and the TIC phenotype of triple-negative breast cancer cells.