The recently advanced cancer stem cell model postulates that progression and metastasis of cancer are mainly driven by tumor cells with stem cell properties. Intestinal cancer stem cells are difficult to study due to the lack of reliable markers, but expression of the Wnt target gene Lgr5 is promising to define at least stem cell like cells in intestinal and colorectal cancer. The aim of this study was to find a possible link of stem cell like cancer cells to the metastatic process of colorectal cancer. To this end, we evaluated immunohistochemical Lgr5 expression in 31 distant metastases and in primary tumor compartments with relevance for metastasizing, comprising 89 colorectal carcinomas. Lgr5 expression was seen in 51.6% of distant metastases. 12.9%, 14.8% and 26.7% of primary tumors with histologically confirmed tumor buds, angioinvasion and perineural infiltrates, respectively, showed evidence of Lgr5 expression in these tumor compartments. However, distant metastases, which were derived from carcinomas with such Lgr5 positive tumor compartments, showed 6- to 11.5-fold higher median value of Lgr5 expression compared to those metastases derived from tumors without Lgr5 expressing cells in these compartments. These differences between the metastases were statistically significant, if being related to tumor buds (all tumors; p = 0.047) and to vascular infiltrates (stage IV tumors; p = 0.007). In conclusion, our results point to rare evidence of Lgr5 positive stem cell like cells in the metastatic cascade of colorectal cancer, but these few cells might be biologically powerful in the metastatic process of cancer subsets. Clonal analysis is necessary to proof this hypothesis
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