Expression of S100A6 and S100A4 in matched samples of human colorectal mucosa, primary colorectal adenocarcinomas and liver metastases.

Objective: S100A6 and S100A4, two of S100 protein family, have been suggested to be associated with cancer tumorigenesis and metastasis. The aim of this study was to evaluate the expression levels of S100A6 and S100A4 in matched samples of primary human colorectal adenocarcinomas (T), adjacent normal colorectal mucosa (N) and liver metastases (M). This gave us the advantage of directly comparing levels of S100A6 and S100A4 expression within the same genetic background.

Methods: In matched samples of N, T and M from 10 colorectal adenocarcinoma patients, expressions of S100A6 and S100A4 were studied by Western blot and immunohistochemical analyses using specific antibodies against each protein.

Results: The expression levels of S100A6 were significantly higher in T than in N (p < 0.05), while those of S100A4 showed no difference between T and N. There were no significant differences in the expression levels of S100A6 or S100A4 between M and T. Similar results were obtained by immunohistochemical analysis. Moreover, S100A6 was stained more intensely in invading fronts than in central portions of both T and M.

Conclusions: The observed differential expression of S100A6 and S100A4 suggests that S100A6, rather than S100A4, is associated with human colorectal adenocarcinoma tumorigenesis and invasion/metastasis.