PANCREATIC TRYPSINOGEN I EXPRESSION DURING CELL-GROWTH AND DIFFERENTIATION OF 2 HUMAN COLON-CARCINOMA CELLS

Pancreatic trypsin has been found to induce tight junction or dome for mation in some colon cancer cell lines (HT-29, Caco-2), and a tumor-as sociated trypsinogen, trypsinogen type II, has been isolated from anot her colon cancer cell line (COLO 205). We have tried to determine if t rypsinogen is present and how its expression varies during cell cultur e in KT-29 Glc+/- and Caco-2 cells, which exhibit enterocytic differen tiation, and in HT-29 Glc+ cells, which never differentiate. Trypsinog en mRNA presence and expression were demonstrated in these cells by mR NA hybridization, RT-PCR, cytoimmunofluorescence, Western immunoblot a nalysis, and gel filtration. Trypsinogen was found to be trypsinogen t ype I and was mainly in zymogen form in culture media. Differentiating cells exhibited variations in trypsinogen I expression, but cells tha t remained undifferentiated did not. In the differentiated cells, a hi gh and transient peak in trypsinogen I expression was observed during the first steps of differentiation.