CLONING AND EXPRESSION OF THE MESSENGER-RNA OF HUMAN GALECTIN-4, AN S-TYPE LECTIN DOWN-REGULATED IN COLORECTAL-CANCER

We are interested in the characterization of genes whose expressions i n the colon are modified during colorectal carcinogenesis. Our approac h was to establish the phenotype of a colon tumor by partial sequencin g of a large number of transcripts, then to select mRNAs of potential interest by differential screening with complex probes from normal or cancerous colon. In this paper, we report the cloning and sequencing o f a mRNA strongly underexpressed in colorectal cancer. It corresponded to a protein comprising 323 amino acids, that appeared to be human ga lectin-4 on the basis of 76% and 79% amino acid identity to the rat an d pig counterparts, respectively. Tissue distribution analysis showed that its expression was restricted to the small intestine, colon and r ectum. Galectin-4 expression was compared in tumor and normal adjacent colon of 19 patients. In 18 patients, the mRNA concentration was 1.5- 50-times lower in the tumor. No significant correlation was observed b etween decreased expression of galectin-4 and the degree of differenti ation of the tumor or Duke's state. These results suggest that decreas ed galectin-4 mRNA expression may be an early event in colon carcinoge nesis. Among five cell lines derived from colon carcinoma, only two (H T29 and LS174T) expressed galectin-4 mRNA.