Abstracts
1998 Digestive Disease Week

#1070

INVOLVEMENT OF FAS IN TAMOXIFEN-INDUCED APOPTOSIS OF CHOLANGIOCARCINOMA. A. Pickens, G. Pan, J. McDonald and
S.M. Vickers. The University of Alabama at Birmingham School of Medicine, Birmingham, AL.

Cholangiocarcinoma continues to have a dismal prognosis with a less than 10% survival. Thus, new modalities of treatment are needed. Tamoxifen (TAM) is an antiestrogen compound which has been shown to provide antimitogenic effects through numerous mechanisms. We have demonstrated that TAM inhibits human cholangiocarcinoma growth in vitro and in vivo (Canc Res 57:1997). Consequently, TAM may provide an effective treatment alternative. The purpose of this study is to evaluate the role of Fas receptor in TAM-induced cell death in cholangiocarcinomas. METHOD: Human cholangiocarcinoma cells, SK-ChA-1, were evaluated for Fas receptor expression using fluorescence-activated cell sorting (FACS). Distinct cell populations were isolated and cloned. Fas receptor expression was assessed using immunohistochemical staining (IHC), Western blot (WB) and RT-PCR. SK-ChA-1 cells were treated for 72 hours with 10µM TAM with and without inhibitory anti-Fas mab, which binds Fas receptor but does not induce apoptosis. Cell viability and apoptotic index were evaluated by trypan blue and TUNEL assay respectively. TAM treatment of these cells was evaluated in BALB/c nude mice (2.5 x 106 cells per subcutaneous injection, TAM IP injections of 0.1mg 3x/week). After four weeks, tumors were harvested and evaluated by IHC, WB and RT-PCR. RESULTS: Populations of Fas+ and Fas- cells were identified and confirmed by FACS, IHC, WB and RT-PCR. Treatment with TAM produced a 74% reduction in cell viability at 72 hours in Fas+ cells versus no decrease in viability in Fas- cells by trypan blue cell count. TUNEL staining showed an apoptotic index of 75% for Fas+ cells incubated in TAM, but no significant evidence of apoptosis in the Fas- cells. TAM-induced reduction in cell viability in Fas+ cells was blocked by inhibitory anti-Fas mab indicating involvement of the Fas pathway. No effect was seen in Fas- cells. In vivo, Fas- cells formed tumor nodules with and without TAM treatment. Fas+ cells failed to form subcutaneous nodules with and without TAM treatment. CONCLUSION: TAM induced apoptosis in vitro in Fas+ cells, and Fas receptor expression appears to be a critical determinant for cholangiocarcinoma in vivo tumor growth.

Copyright 1996 - 1998, SSAT, Inc. Revised 29 June 1998.