Uncontrolled cell growth within a tumor results in hypoxia as the metabolic needs of the cells exceed the ability of the tumor vasculature to provide oxygen and nutrients. In response to the hypoxic microenvironment, cells undergo a massive reprogramming of transcription to promote survival. The Hypoxia Inducible Transcription Factors (HIFs) are primary regulators of the hypoxic response and induce the expression of glycolytic genes, cell migration factors, and angiogenic factors. HIFs also induce expression of several transcriptional regulators, including several histone demethylases, providing a mechanism for the hypoxic cell to extend or fix the expression of pro-survival genes. One of these histone demethylases, JMJD2B, demethylates tri-methylated histone H3 lysine 9 (H3K9me3), a key marker of repressed chromatin structure. Hypoxic induction of JMJD2B may play an important role in activating gene expression to promote tumor growth. Consistent with this hypothesis, forced knock-down of JMJD2B expression reduces growth of tumor xenografts, and is overexpressed in ovarian cancers. In this proposal, the extent to which JMJD2B regulates tumor growth will be tested in vivo using tumor xenograft experiments and in vitro by assaying for cell proliferation, invasion, and angiogenesis as a result of JMJD2B expression (Specific Aim 1). Subsequent biochemical experiments will determine the mechanism of specific target gene regulation in hypoxia, identify new genes regulated by JMJD2B in hypoxia, and characterize the regulation of key pathways of genes important for the tumorigenic phenotype (Specific Aim 2). The experiments described in this proposal will establish the mechanisms utilized by JMJD2B to regulate tumorigenesis, while identifying new pathways to target for enhanced tumor therapies.
Cancer cells typically grow faster than the surrounding blood vessels can supply oxygen and nutrients. In response to decreased oxygen (hypoxia), cancer cells alter their gene expression to enhance survival, resulting in more aggressive tumors. In this study we will determine the function of JMJD2B, a regulator of hypoxic gene expression in cancer cells, with the ultimate goal of finding better targets for cancer therapy.
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