Resistance to UV in HR18 cells depends on DDB2 and cFLIP. (A) Attenuation of DDB2 protection against UV-induced apoptosis by knockdown of cFLIP using antisense oligonucleotides. HR18 cells were treated as described in the Materials and methods. The plotted values represent means ± S.D. of experiments performed in triplicates. Inset: immunoblot with specific antibodies. (B) Attenuation of UV-induced caspase activity by forced expression of DDB2, and resensitization by cFLIP antisense oligonucleotides.