Blood 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 leukocyte PAH-DNA damage as a biomarker associated with increased risk of disease. We have extracted DNA and measured PAH-DNA adducts in 140 samples, and the epidemiological analysis is currently in progress. The high incidence of gastro-intestinal cancers in beluga whales inhabiting the mouth of the Saguenay River in the St. Lawrence Estuary (SLE) may be due to dietary PAH exposures. For 50 years, starting in 1926, PAH waste from an aluminum smelter was discarded into the river, and since the 1980s the SLE belugas found stranded presented with high occurrences of gastro-intestinal cancer. Because DNA adduct formation provides a critical link between exposure and tumor induction, we performed immunohistochemical (IHC) staining with an antiserum specific for DNA modified with several carcinogenic PAHs, to investigate PAH-DNA adduct formation in beluga intestine. Cryostat sections of paraffin blocks, obtained from SLE beluga (n=53) and control beluga (n=19, from aquariums and the Canadian arctic), were stained to visualize PAH-DNA adducts. Each tissue section was scanned digitally into the Aperio system and examined for nuclear staining in the small intestine crypt epithelial lining cells, the cells where tumors arise. Two different types of coded analysis were applied. The data showed significantly higher levels of PAH-DNA adduct in intestine from SLE beluga compared to the controls, as well as a significant increase in PAH-DNA adduct levels with age of the SLE beluga. Tamoxifen (TAM), used for adjuvant therapy of breast cancer, also increases the risk of endometrial cancer. To compare TAM-induced transcriptional changes in breast and endometrium we examined global 5-methyl cytosine (5-meC), TAM-induced microarray changes, 5-meC in promoter region CpG islands of TAM-upregulated genes, and protein levels for histone H3 lysine di-methylases. Evaluation of uterine DNA from women (n=15) and monkeys (Erythrocebus patas n=5, and Macaca fascicularis n=12), either unexposed or exposed long-term to oral TAM, showed no difference in 5-meC levels. Subsequent studies employed normal human mammary epithelial cells (NHMECs) and human endometrial stromal cells (HESCs) exposed to 10 microM TAM for 48 hr. By Affymetrix microarray, with confirmation by RT-PCR, TAM-exposed NHMECs showed significant up-regulation of interferon signaling and immune response pathways, while the TAM-exposed HESCs showed significant up-regulation of steroid and fatty acid biosynthesis pathways. Several genes, highly up-regulated by TAM in each cell type, were examined for 5-meC levels in promoter region CpG islands, but the 5-meC levels were too low to measure accurately. Subsequently we turned to histone H3 methylases. The di-methyl histone H3 lysine K4, K27, and K36 methylases, examined in TAM-exposed and unexposed NHMECs and HESCs by Western blot, showed a consistent depletion in both cell types with TAM exposure. Therefore, TAM exposure induced up-regulation of different transcriptional pathways in NHMECs and HESCs, and depleted some histone H3 methylase protein levels in both cell types.
Showing the most recent 10 out of 18 publications
