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VHL substrate transcription factor ZHX2 as an oncogenic driver in clear cell renal cell carcinoma

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Science  20 Jul 2018:
Vol. 361, Issue 6399, pp. 290-295
DOI: 10.1126/science.aap8411

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Mechanistic insights into kidney cancer

Many clear cell renal cell carcinomas (ccRCCs) have alterations to the gene encoding the von Hippel-Lindau protein (VHL). VHL is a ubiquitin ligase that degrades target proteins when they are prolyl-hydroxylated. Zhang et al. performed a genome-wide search for VHL target (see the Perspective by Sanchez and Simon). They identified ZHX2, a protein with structural motifs that indicate DNA binding. ZHX2 has been implicated in tumor suppression. Loss of ZHX2 inhibited signaling through the transcription factor NF-κB, and ZHX2 bound to many NF-κB target genes. Depletion of ZHX2 slowed growth of ccRCC cells in vitro and in a mouse model.

Science, this issue p. 290; see also p. 226

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.

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