A Fas-dependent component in 5-fluorouracil/leucovorin-induced cytotoxicity in colon carcinoma cells.
We have shown previously (J. A. Houghton et al., Proc. Natl. Acad. Sci. USA, 94: 8144-8149, 1997) that thymineless death in thymidylate synthase-deficient (TS-) colon carcinoma cells is mediated via Fas/FasL interactions after deoxythymidine (dThd) deprivation, and that Fas-dependent sensitivity of human colon carcinoma cell lines may be dependent upon the level of Fas expressed. The objective of this study was to elucidate whether a Fas-dependent component exists in 5-fluorouracil (FUra)/leucovorin (LV)-induced cytotoxicity of colon carcinoma cells, and whether this may be potentiated by IFN-gamma-induced elevation in Fas expression, using the HT29 cell line as a model. The cytotoxic activity of FUra/LV was inhibited by dThd in HT29 cells and also, in part, by NOK-1+NOK-2 MoAbs that prevent Fas/FasL interactions. FUra/LV-induced cytotoxicity was significantly potentiated by IFN-gamma, reversed by exposure to NOK-1+NOK-2 antibodies, and correlated with a 4-fold induction of Fas expression in the presence of IFN-gamma and significant elevation in expression of FasL. Using five additional human colon carcinoma cell lines, FUra/LV-induced cytotoxicity was dThd-dependent in GC3/c1, VRC5/c1, and Caco2 but not in HCT8 or HCT116 cells. Like HT29 cells, this cytotoxicity was potentiated by IFN-gamma in GC3/c1 and VRC5/c1 but not in Caco2, which fails to express Fas, nor in HCT8 and HCT116, in which no dThd-dependent FUra-induced cytotoxicity was demonstrated. Data suggest that a Fas-dependent component, potentiated by IFN-gamma, exists in FUra/LV-induced cytotoxicity but requires FUra/LV-induced DNA damage for IFN-gamma-induced potentiation to occur.
Department of Molecular Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
D M
DM
Tillman
I
I
Petak
J A
JA
Houghton
D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D004357:Drug Synergism; D053222:Fas Ligand Protein; D005472:Fluorouracil / Q000494:pharmacology*; D019073:HT29 Cells; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D002955:Leucovorin / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D009479:Neuropeptides / Q000096:biosynthesis / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D019014:fas Receptor
C491901:FAS protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D009479:Neuropeptides; D018124:Receptors, Tumor Necrosis Factor; D019014:fas Receptor; D007371:Interferon-gamma; D002955:Leucovorin; D005472:Fluorouracil