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-γ-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-γ, reversed by exposure to NOK-1+NOK-2 antibodies, and correlated with a 4-fold induction of Fas expression in the presence of IFN-γ 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-γ 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-Γ, exists in FUra/LV-induced cytotoxicity but requires FUra/LV-induced DNA damage for IFN-gamma-induced potentiation to occur.
|Number of pages||6|
|Journal||Clinical Cancer Research|
|Publication status||Published - Feb 1 1999|
ASJC Scopus subject areas
- Cancer Research