Colorectal cancer (CRC) is common in the United States and other Western countries. Compelling evidence indicates that environmental factors increase the risk of CRC. It is generally accepted that colorectal adenomas are precursors to CRC. Defining environmental and lifestyle factors that favor adenoma formation is integral to improved surveillance and prevention. Our group found that lower levels of apoptosis in normal appearing rectal mucosa and increased BMI were strong predictors of adenoma risk. This competing renewal will test the central hypothesis that systemic cytokines and adipokines or local biomarkers of inflammation predict risk for colorectal adenomas and low apoptosis within the normal colonic epithelium.
The specific aims are: (1) To measure circulating biomarkers of inflammation, C- reactive protein, interleukin-6 (IL-6), and TNFa, and test for associations with adenomas and apoptosis. (2) To measure circulating adipokines leptin and adiponectin and test for associations with adenomas and apoptosis. (3) To assay local activation or expression of TNFa and IL6 to test the hypothesis that high levels these local biomarkers of inflammation correlate with increased adenoma risk or low apoptosis. (4) To assess activation of NFkB and STATS, anti-apoptotic transcription factors in colonic epithelial cells;these factors are activated by multiple cytokines, adipokines and insulin, and are linked to colorectal neoplasia. Study subjects will be 600 consenting male and female patients who meet eligibility criteria. Blood samples will be collected immediately before routine colonoscopy and pinch biopsies of normal rectal mucosa will be collected during colonoscopy. Apoptosis will be measured in biopsies using morphological light microscopy-based assays and caspase-3 immunohistochemistry. Plasma levels of cytokines and adipokines will be measured by ELISA. Local expression of TNFa and IL6 will be measured by real time PCR. Tissue levels of activated NFkB and STATS will be measured by electromobility shift assay. This study is a logical extension of previous research. The proposal has the potential to improve our understanding of the role of obesity and inflammation in the development of colorectal neoplasia and to predict mechanistic links between inflammation and adenoma risk. Ultimately the results may inform surveillance and prevention strategies.
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