Influence of cytokines on the expression of Fas ligand and CD44 splice variants in colon carcinoma cells

The expression of Fas ligand (FasL) by malignant cells might be a mechanism for tumor immune escape. We investigated Fast expression by LS 174T colon carcinoma cells. Furthermore, the effects of in vitro stimulation with rIL- 2, rIFN-gamma and rTNF-alpha were investigated with regard to a possible re gulation of the Fast expression by cytokines. Fast expression was detected by flow cytometry and RT-PCR. We observed a spontaneous expression of Fast by LS 174T cells. Incubation with high-dose rTNF-alpha induced an upregulat ion of Fast of 23%. rIL-2 and rIFN-gamma did not significantly affect Fast expression. To control whether our cytokine stimulation experiments were su itable to prove an upregulation of membrane proteins by tumor cells, we inv estigated the expression of ICAM-1, N-CAM, CD44s, CD44v6 and CD44v10. These adhesion molecules were spontaneously expressed by LS 174T cells. Only ICA M-1 and CD44v10 were significantly upregulated by rIFN-gamma and rTNF-alpha , respectively. These results could indicate that cytokines, released by tu mor-infiltrating leukocytes, may induce the Fast-dependent apoptotic signal by which tumors downregulate an immunological host response. Copyright (C) 1999 S.Karger AG, Basel.