Role of IRF-1 and caspase-7 in IFN-γ enhancement of Fas-mediated apoptosis in achn renal cell carcinoma cells

Abstract

Caspases exist as zymogens, and are activated by various extracellular stimuli, leading to apoptosis. One such stimulus is Fas/CD95, a member of the tumor necrosis factor receptor family, providing one means of cytotoxic T lymphocyte (CTL)-mediated cell lysis. Clinical evidence has shown that administration of cytokine leads to regression in selected patients with renal cell carcinomas (RCCs). Interferon-γ (IFN-γ) indicates its contribution to anti-tumor activity of immune cells. IFN-γ elicits its effect through the transcription factor signal transducer and activator of transcription-1 (STAT-1), and through interferon regulatory factor-1 (IRF1), one of the target genes of STAT-1. Our previous study demonstrated an increase in the susceptibility of ACHN cells, established from RCC, to Fas-mediated apoptosis by IFN-γ, and the inhibition of this effect by the caspase-3 and -7 inhibitor, DEVD-CHO. We demonstrated the following phenomena in IFN-γ-treated ACHN cells: 1) enhanced transcription of caspase-1, 3 and 7 mRNAs without any change in cleavage of their substrates; 2) increased cleavage DEVD (specific for caspase-3 and 7), but not YVAD (for caspase-1) or DMQD (for caspase-3), after anti-Fas/CD95 MAb treatment; 3) activation of the STAT-1 and IRF-1 pathway; and 4) partial abrogation of the IFN-γ-induced increase in Fas-mediated apoptosis by antisense IRF-1 oligodeoxynucleotide. These results suggest that IRF-1 plays a pivotal role in the IFN-γmediated-enhancement of Fas/CD95-mediated apoptosis, through regulation of DEVD-CHO-sensitive caspases, most likely caspase-7. © 2003 Wiley-Liss, Inc.