410 Background: Human colon stem cells share phenotypic hallmarks of self-renewal and proliferation that are associated with tumor cells. Lgr5 is a marker of colon stem cells and not colon differentiated cells. In mice, deletion of the adenomatous polyposis coli gene in colon stem cells but not in colon differentiated cells, rapidly gives rise to macroscopic adenomas. We investigated the role of Lgr5 colon stem cells in human colon tumors in relation to tumor cell of origin, tumor progression, tumor recurrence, and overall survival. Methods: Using in situ hybridization, we determined the histological distribution of Lgr5 mRNA in human colon specimens at different stages of tumor development and tumor recurrence after chemotherapy. Using gene expression analysis, we analysed Lgr5 mRNA expression levels in human normal colon (n = 33), normal liver (n = 13), colon adenomas (n = 45), primary colon adenocarcinomas (n = 170), liver metastates (n = 48) and lung metastates (n = 20). We examined the correlation between Lgr5 mRNA expression, K-ras mutation status and overall survival in stage IV colon adenocarcinomas. Results: Human normal colon Lgr5 mRNA was always expressed at basal level and restricted to human colon stem cells. In contrast, we observed an all (Lgr5(+)) or none (Lgr5(-)) expression in human colon adenomas, adenocarcinomas and liver metastases. When present Lgr5 mRNA expression was increased 3-10 fold compared to normal colon. The Lgr5 gene expression analysis provided similar results with increased expression in 66% of human colon adenomas, 62% of primary colon adenocarcinomas, 72% of colon liver metastases and 55% colon lung metastases when compared to normal colon. We have determined that 22.5% (18/80) of Lgr5(+)and 46.4% (26/56) of Lgr5(-) colon adenocarcinoma specimens have K-ras mutations. Kaplan-Meier estimates of median overall survival in Lgr5(+) and Lgr5(-) Stage IV colon adenocarcinomas were 20 months and 15 months, respectively. Conclusions: Human colon adenocarcinomas are derived predominantly from Lgr5 colon stem cells. Lgr5(+) colon adenocarcinomas required less frequent K-ras mutation for tumor progression then Lgr5(-) colon adenocarcinomas. No significant financial relationships to disclose.
Ibuprofen Inhibits Activation of Nuclear β-Catenin in Human Colon Adenomas and Induces the Phosphorylation of GSK-3β
