ACTIVATED RAS AND SRC INDUCE CD44 OVEREXPRESSION IN RAT INTESTINAL EPITHELIAL-CELLS

CD44 is an adhesion molecule that is involved in the progression of se veral tumor types, including those originating in the intestine. There are several alternatively spliced forms of CD44. Here we show that in testinal epithelial cells express the standard form of CD44 (CD44s). T he same form of CD44 is found in IEC-18, a cell line derived from norm al rat intestinal crypts. Upon transfection of IEC-18 cells with vas o r src, two oncogenes that are frequently activated in intestinal tumor s, a significant induction of CD44s is observed. A causal role for vas in this induction is shown by using IEC clones transfected with an in ducible vas expression vector. The oncogene-transformed IEC clones dis play a high degree of hyaluronic acid-dependent cell-cell adhesion tha t is not observed in the parental IEC-18 cells suggesting that ras- an d src-induced overexpression of CD44 c;ln alter the adhesion propertie s of intestinal cells.