Development and progression of malignancy in human colon tissues are correlated with expression of specific Ca2+-binding S100 proteins

The expression levels of seven different S100 proteins (S100A1, S10OA2, S10 0A3, S100A4, S100A5, S100A6, and S100B) were characterized by immunohistoch emistry in the epithelial versus connective tissues of a series of 35 colon specimens, including 6 normal samples, 5 adenomas with low-grade dysplasia , 5 adenomas with high-grade dysplasia, and 19 cancers. The results showed that S10OA2, S100A3, and S100B proteins could not (or only marginally) be d etected in colon tissues. On the other hand, the expression of S100A6 incre ased in epithelial tissues directly proportional to the increase of maligna ncy. The percentage of epithelial (or connective tissue) cells expressing S 100A4 significantly decreased as the malignancy grade increased. The expres sion level of S100A1 proteins was somewhat higher in the connective tissues of normal cases and adenomas with low-grade dysplasia than in adenomas wit h high-grade dysplasia and cancers. This pattern of expression was not obse rved in epithelial tissues. While the node-positive cancers did not express S100A1, about half of the node-negative specimens did. The expression leve ls of S100A5 were similar in different epithelial tissues. However, in the connective tissues the expression levels decreased inversely proportional t o the increase in pathological grading of the specimens. Therefore, the pre sent study implicates several S100 proteins as useful tools for histochemic al typing of colon cancer malignancy development.