Activated ras and src induce CD44 overexpression in rat intestinal epithelial cells.

CD44 is an adhesion molecule that is involved in the progression of several tumor types, including those originating in the intestine. There are several alternatively spliced forms of CD44. Here we show that intestinal epithelial cells express the standard form of CD44 (CD44s). The same form of CD44 is found in IEC-18, a cell line derived from normal rat intestinal crypts. Upon transfection of IEC-18 cells with ras or src, two oncogenes that are frequently activated in intestinal tumors, a significant induction of CD44s is observed. A causal role for ras in this induction is shown by using IEC clones transfected with an inducible ras expression vector. The oncogene-transformed IEC clones display a high degree of hyaluronic acid-dependent cell-cell adhesion that is not observed in the parental IEC-18 cells suggesting that ras- and src-induced overexpression of CD44 can alter the adhesion properties of intestinal cells.