Biological properties and expression of mucins in 5-fluorouracil resistantHT29 human colon cancer cells

We have previously reported that HT29 human colon cancer cells selected by adaptation to 5-fluorouracil (5FU) (HT29-5FU cells) express increased level s of a major intestinal mucin MUC2 mRNA compared with parental HT29 cells. In this study, we examined in detail the changes in synthesis and secretion of mucin that occur in these cells and accompanying changes in the express ion of cancer associated mucin related carbohydrate antigens and cell linea ge associated biochemical markers. We further investigated their relationsh ip to biological properties of cells. Northern blot analysis revealed a mar kedly increased level of MUC2 mRNA but no significant change in the mRNA le vels of other mucins in HT29-5FU cells compared with parental HT29 cells. L abeling with radiolabeled precursors demonstrated increased synthesis and s ecretion of mucin glycoproteins by HT29-5FU cells. Immunoblot analysis show ed a higher expression of mucin associated carbohydrate antigens such as T, Tn, sialyl Tn, sialyl Le(a), sialyl Le(x) and non-O-acetylated sialic acid concomitant with significant increases in the expression of goblet cell li neage marker, MUC2 apomucin and a panepithelial cell marker, carcinoembryon ic antigen. HT29-5FU cells showed significantly higher adhesion to E-select in and to matrigel and in vitro invasive properties and significantly incre ased liver colonization capacity in nude mice following splenic vein inject ion. Nude mouse xenograft tumors produced by HT29-5FU cells showed a greate r degree of differentiation, consisting of mucin secreting glands than thos e produced by parental HT29 cells. These results indicate that predominantl y colonic type mucin, MUC2, has been selectively induced in HT29-5FU cells and that altered regulation of mucin genes associated with altered synthesi s and secretion of mucin glycoproteins and the degree of differentiation in cancer cells may be responsible for the altered biological properties of t hese cells.