Expression of Human Collectins in Colorectal Carcinoma

Siassi, M.; Hohenberger, W.; Croner, R.

Introduction: The human collectins, mannan‐binding lectin (MBL), surfactant protein‐A (SP‐A) and surfactant‐protein‐D (SP‐D) play a central role in the innate immune system. Immunological responses to malignant transformation of epithelial cells gained increasing interest recently. A former study could demonstrate binding of MBL to certain colorectal carcinoma (CRC) cell lines in vitro. We therefore examined the expression of human collectins in normal colon mucosa and in colorectal carcinomas. Materials and methods: Colon samples from 20 CRC patients and 10 normal mucosa samples were collected immediately after surgery. The tissue was microdissected and RNA isolated (Qiagen, Rneasy‐Kit). Gene expression profiles were analysed using Gene‐chips (Affymetrix, HG‐U133). We analysed the data for the expression of MBL, its associated serine proteases mannan‐binding lectin‐associated serine protease 1/2 (MASP 1/2), SP‐A and SP‐D. The signal intensity of the genes of interest was compared using the Mann–Whitney U‐test. Results: The expression of human collectins in normal human colon mucosa was generally low. Only the expression of SP‐A and MASP‐2 reached the noise threshold of 250 signals. These genes were significantly downregulated in CRC specimens. The expression of the other proteins showed no difference in normal mucosa and CRC. Conclusion: As demonstrated before, the expression of human collectins in normal colon was low in this study. Only SP‐A showed a significant expression in normal mucosa which was downregulated in CRC. As the absolute signal level was below the noise threshold, these results have to be interpreted with caution and require confirmation by direct measurenment of the proteins. Our results suggest that there is no major role for the human collectins in colorectal cancer.