Abstract 787: Aberrantly increased expression of ZIC2 is correlated with altered cellular metabolism in prostate cancer
Authors: Bowen Nathan J. , Danaher Alira 
Published: August 2019

Prostate cancer incidence and mortality rates are consistently reported to be higher in American men of recent African ancestry when compared to American men of recent European or Asian ancestry. However, actionable factors contributing to these different rates remain undefined. In order to identify common molecular events to assist in the design of interventions aimed at prevention and treatment of lethal prostate cancer, we analyzed existing public RNA-Seq data and report that Zic family member 2 (ZIC2) RNA levels are significantly higher in prostate and other cancers. ZIC2 encodes a C2H2 zinc finger domain containing protein that is expressed during embryonic development in metazoans. Altered ZIC2 expression results in holoprosencephaly in humans. The ZIC2 locus also encodes several RNA species that have been co-purified with members of the polycomb repressive complex 2 (PRC2). In prostate cancer, we found that ZIC2 levels correlated significantly with primary cancer grade, i.e., the highest ZIC2 expression was found in lethal, metastatic prostate cancer. Therefore, we hypothesize that increased ZIC2 contributes to cancer initiation and progression. To establish models for identifying functional roles for ZIC2 in cancer, we targeted the first exon in ZIC2 by CRISPR/Cas9, with the intent of abrogating ZIC2 expression. We established clonal cell lines from PC-3, E006AA-Par and 293T cells with mutant ZIC2 loci. ZIC2 mutant cells displayed significant decreases in proliferation and altered phenotypes. RNA-Seq revealed expression patterns consistent with reduced glycolysis and increased oxidative phosphorylation, as well as many altered signaling pathways, in cells with ZIC2 mutations. Metabolism was monitored by extracellular flux analysis and revealed increased oxygen consumption and significantly higher respiration rates in ZIC2 mutant cells. ZIC2 localization to mitochondria was predicted using computational methods and confirmed by sub cellular fractionation and immunoblot analysis as well as by GFP-tagged microscopy. JC-1 fluorescence indicated increased mitochondrial membrane potential in ZIC2 mutant cells. We present these results and suggest that ZIC2 promotes anabolic metabolism consistent with embryonic development and cancer cell proliferation. We found that altering ZIC2 expression in PC-3 cells increased oxidative phosphorylation and produced a 5X increase in the number of apoptotic cells. Our results suggest that ZIC2 expression contributes to the cancer phenotype, given that altered cellular energy metabolism and evasion of apoptosis are defining characteristics of nearly all cancers. We further propose that the targeted inhibition of ZIC2 in cancer cells will decrease mortality rates in men diagnosed with lethal prostate cancer.

Citation Format: Nathan J. Bowen, Alira Danaher. Aberrantly increased expression of ZIC2 is correlated with altered cellular metabolism in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 787.