CYTOKINE-MEDIATED APOPTOSIS AND INHIBITION OF VIRUS PRODUCTION AND ANCHORAGE-INDEPENDENT GROWTH OF VIRAL TRANSFECTED HEPATOBLASTOMA CELLS

Cytokine-mediated apoptotic destruction of viral-infected cells, downr egulation of virus production and inhibition of anchorage dependent (c lonal) cell growth were evaluated using virus-transfected human hepato blastoma (HepG2) cells, The cytokines evaluated,were interferon alpha (IFN-alpha), tumour necrosis factor alpha (TNF-alpha) and thymosin alp ha 1 (T alpha 1), all of which have previously been implicated in cont rol of various viral infections. The viruses evaluated were Hepatitis B (HBV) and the transforming virus, SV-40. TNF-alpha-induced apoptosis in the HBV-transfected cell line and the control HepG2 cells but not the HepG2 cells transfected with SV-40 virus, IFN-alpha and T alpha 1 had no effect on apoptosis, TNF-alpha also prevented the clonal growth of the HBV-HepG2 and control HepG2 but enhanced the growth of the SV- 40-transfected HepG2 cells, IFN-alpha inhibited the clonal growth of a ll three cell lines in contrast to T alpha 1 which inhibited the clona l growth of only the HBV-transfected cells, Although TNF-alpha, IFN-al pha, and T alpha 1 when given alone did not significantly inhibit HBV- DNA production in the culture supernatant from HBV-HepG2 cells, the co mbination of T alpha 1 and IFN-alpha resulted in a statistically signi ficant inhibition of virus production. These studies demonstrate that HepG2 cells transfected with HBV and SV-40 are useful for defining the mechanisms of cytokine activity, The HBV-transfected cells are especi ally useful in defining possible in vivo differences in responses to c ytokines with respect to HBV production, apoptosis and clonal cell gro wth. Multiple mechanisms through which different cytokines can influen ce HBV infection and hepatoblastoma growth were identified and the imp ortance of defining effective combinations to improve therapy in vivo demonstrated. (C) 1998 Academic Press.