CASP9 and renal cell carcinoma: Since the caspase-9 pathway was shown to be functionally involved in IR-induced apoptosis in other tumour models (Newton and Strasser, 2000; Joseph et al, 2001; Rudner et al, 2001), the impaired activation of caspase-9 might contribute to the well-known resistance of RCC to IR-induced apoptosis.