Abstract 1699: The effects of hypoxia and oxidative stress on transcriptional regulation of carcinogen metabolizing enzymes

Enzymes are essential to every biochemical process; it is through the action of enzymes that the many metabolic pathways of the body can synchronize with one another to coordinate the processes needed to maintain life. Enzymes are also involved in the metabolism of xenobiotics including dietary chemicals, drugs and environmental chemicals. In this capacity they are very involved in chemical carcinogenesis. Cytochrome P450 1A1 (CYP1A1) and NAD(P)H: quinone oxidoreductase (NQO1) are two enzymes that play a vital role in the process of chemical carcinogenesis. The aryl hydrocarbon receptor (AhR), located in the cytoplasm, mediates various biological responses to environmental pollutants via the adaptive pathway. The binding of a xenobiotic to the AhR triggers transcriptional activation of xenobiotic metabolizing enzymes such as CYP1A1 and NQO1. Our current research investigates the contrast between oxidative stress and hypoxia on the transcriptional activation of CYP1A1 and NQO1 enzyme expression. Hypoxia is a frequent characteristic of tumors as a result of low vascualrization. The transcription factor HIF1alpha can serve as a marker of hypoxia, and aids as a key regulator of the hypoxic response. Previous research in our lab has shown that oxidative stress results in an increase in CYP1A1 and NQO1. We hypothesize that under hypoxic conditions the expression of NQO1 and CYP1A1 are altered which could indicate that hypoxia may possibly play a role in carcinogen metabolism. Two human cancerous cell lines, HEPG2 and HT29, were used to test this hypothesis. Both cells lines were treated with 500 µM of the hypoxic mimetic agent cobalt chloride and harvested at one, two and four hour increments. Hypoxic conditions were then confirmed via HIF1 alpha staining in immunocytochemistry. We then observed mRNA, protein and enzyme expression via RTPCR, Western Blots and enzyme assays, respectively. Altered levels of NQO1 and CYP1A1 suggest that these enzymes respond to hypoxia in a similar manner as they do to oxidative stress. This may provide preliminary evidence into one of the potential mechanisms by which hypoxia is chemopreventive. (Support: NIH MBRS/GM028248; RCMI RR033032). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1699.