Colonic epithelial genes in the transition from chronic inflammation to carcinoma in human colitis-associated cancer: focus on the truncated neurokinin-1 receptor
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Patients with chronic ulcerative colitis (UC) are at high risk for developing colorectal cancer. Since there is a need for early detection and targeted therapeutics to treat this disease, the aim of this study was to identify changes in expression of pro-inflammatory and oncogenic genes and proteins in colonic tissue from patients with UC who developed colon cancer. Using laser capture microscopy, epithelia were microdissected from archival formalin-fixed paraffin-embedded colonic tissue that showed histologic evidence of carcinoma (CA), high-grade dysplasia (HGD), and non-neoplastic areas with evidence of prior inflammation (quiescent colitis, QC). mRNA was extracted from the dissected tissue and PCR array analysis was performed. Three proteins, plasminogen activator inhibitor-1 (PAI-1), the truncated neurokinin-1 receptor (tr-NK-1R) and its full-length isoform (fl-NK-1R), were quantitated using immunofluorescence. The biological properties of the tr-NK-1R and fl-NK-1R were further explored through stable transfection in HEK293 cells. mRNA expression of the tr-NK-1R is increased 14-fold (n=5, p=0.02) in carcinoma compared to HGD, while the fl-NK-1R transcript shows no significant differences amongst groups. mRNA expression of PAI-1 is increased 6-fold (n=5, p=0.02) in carcinoma compared to QC. Total NK-1R protein is increased by 40% (n=1 0, p=0.02) in HGD and by 80% (n=9, p=0.0007) in carcinoma compared to QC (n=11). There is no significant change in fl-NK-1R protein among groups, permitting the conclusion that the increase in total NK-1R protein in HGD and carcinoma is attributable to an increase in tr-NK-1R. PAI-1 protein is increased by 50% (n=1 0, p<0.001) in HGD and by 60% (n=9, p<0.001) in carcinoma compared to QC (n=11). HEK293 cells transfected with tr-NK-1R proliferate more rapidly. Tr-NK-1R transfectants also produce a greatly increased level of heat shock protein 70, an oncogenic protein that may participate in their proliferation. These data suggest there may be a functional role for PAI-1 and tr-NK-1R, perhaps through the upregulation of heat shock protein 70, in malignant transformation in colitis-associated cancer. The two proteins could prove useful as diagnostic markers to identify patients at risk for neoplasia and may serve as useful therapeutic targets in the treatment of colitis-associated cancer.
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