IBlood cell PAH-DNA adducts and lung cancer risk. Xuan Wei, in southern China, has the highest lung cancer rates in the country, and the etiologic cause is considered to be exposure to smoky coal, used for heating and cooking.
The aim of this study is to elucidate the interaction between environmental exposure and etiology of lung cancer among women in Xuan Wei by measuring PAH-DNA damage as a biomarker associated with increased risk of disease. Currently we have extracted DNA from 140 blood samples, and have assayed 40 of these for PAH-DNA adduct formation. The study will be complete this summer (2015). PAH-DNA adduct formation in whales correlates with high PAH exposure in areas with elevated risk of cancers in whales and humans. Using immunohistochemistry of paraffin embedded samples we have found high levels of PAH-DNA adduct formation in epithelium taken from pilot whales in the Gulf of Mexico in 2012, two years after the Deepwater Horizon oil spill. Similar whales, residing in the Pacific Ocean in areas with low PAH contamination, did not show evidence of epidermal PAH-DNA adduct formation. Furthermore, we have found intestinal PAH-DNA adduct formation in beluga whales from the St. Lawrence Estuary (SLE). These whales have high incidences of intestinal tumors as a result of PAH waste dumped into the river from an upstream aluminum foundry (1924-1975). The beluga food supply remains contaminated with PAHs, and we find high levels of PAH-DNA in the beluga intestinal nuclei. Belugas from Sea World, the Canadian arctic and Alaska have much lower levels of intestinal PAH-DNA adducts than those from the SLE. Workers from the aluminum foundry have increased risk of lung, stomach and bladder cancers, and we are examining paraffin blocks for evidence of PAH-DNA adduct formation in target tissues. (Study in progress.) In the area of Tamoxifen (TAM) carcinogenesis, we showed previously that human endometrium, a target for TAM-induced cancers, accumulates TAM-DNA adducts. From the literature it appears that TAM-DNA damage, cell proliferation and other factors likely contribute to TAM-induced endometrial cancer induction. We hypothesized that gene expression patterns and epigenetics may also contribute. Therefore, we used microarrays to evaluate gene expression in cultured normal human cells exposed to TAM. TAM-exposed normal human mammary epithelial cells (NHMECs) showed TAM-induced up-regulation of interferon signaling, complement pathways and immune function genes. In contrast, TAM-exposed human endometrial stromal cells (HESCs) showed up-regulation of steroid (cholesterol) biosynthesis and cell proliferation. There was very little down-regulation in TAM-exposed cells. For 7-8 of the most highly overexpressed genes, microarray expression changes in both cell types were confirmed by quantitative RT-PCR. To examine TAM-induced epigenetic changes we first measured global DNA methylation at the 5-position of cytosine (5-mC) in uterine tissue from primates (patas and macaque monkeys and humans) exposed to TAM for more than 3 months. The TAM-exposed patas monkeys had increased levels of uterine 5-mC compared to the controls (p = 0.04), but in the macaques and the humans TAM exposure did not make a difference. Assuming that global methylation might not be sufficiently sensitive, we evaluated 5-mC formation in promoter region CpG islands of genes significantly upregulated by TAM, in both the NHMECs and HESCs. Promoter region pyrosequencing was performed in 2 genes highly up-regulated by TAM in the breast cells and 4 genes highly up-regulated by TAM in the endometrial cells. We found that TAM exposure did not alter 5-meC levels in any of the CpG islands. Concluding that 5-mC might not be a major epigenetic player in modulating TAM effects, we have chosen to examine protein levels of histone methylases in the TAM-exposed breast and endometrial cells, and those studies are in progress.
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