Abstract 3095: The molecular, cellular, and physiological consequences of disrupting the HIF-1α interaction

Many cancers contain regions of hypoxia due to rapid cell proliferation and the presence of blood vessels within the tumor that are structurally and functionally abnormal, resulting in the heterogeneity of blood flow. This state of hypoxia is associated with increased risk of treatment failure, metastasis and patient mortality. A principal mechanism by which cancer cells adapt to the hypoxic microenvironment is through the activity of hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor composed of an O2-regulated HIF-1α subunit that dimerizes with a constitutively expressed HIF-1β subunit. HIF-1α expression under hypoxic conditions regulates hundreds of genes including those that play key roles in invasion/metastasis, angiogenesis, tumor cell immortalization, and resistance to chemotherapy and radiation. Therefore, the inhibition of transcription driven by HIF has the potential for cancer treatment. One way to reduce the activity of this protein is by disrupting the complex that HIF forms with p300, an essential transcriptional coactivator. Previous data from our laboratory showed that several members of the epidithiodiketopiperazine (ETP) family of natural products are able to block the interaction between HIF-1α and p300. Here, we extend these studies by examining the comprehensive effect that select ETPs have on the disruption of the HIF/p300 complex at the molecular, cellular, and physiological levels. We began our studies by performing a series of rat aortic ring assays to determine the antiangiogenic effect of selected ETPs, namely chetomin, chaetocin, and gliotoxin. Chetomin and chaetocin concentrations of 50 nM inhibited approximately 90% of outgrowth, while 500 nM of gliotoxin was needed to achieve a similar effect; these compounds had GI50 of 22, 11, and 175 nM, respectively. In ongoing work, we hope to determine if the antiangiogenic effects that were observed in our rat aortic ring assays, are due to disruption of the HIF/p300 complex. To this end we are immunoprecipitating the complex from cells in the absence or presence of the aforementioned ETPs. The molecular consequences of blocking the HIF/p300 interaction will be assayed by qRT-PCR for hypoxia-regulated genes such as VEGF and GLUT1; cell proliferation and migration assays will also be performed to monitor cellular effects. Together, these results will be key in determining the feasibility of targeting this interaction for cancer therapeutics. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3095. doi:10.1158/1538-7445.AM2011-3095