We found that: (i) BID fused with TAT peptide is delivered to cells at the non-toxic dose; (ii) delivered BID sensitized PC3 cells to apoptosis induced by TRAIL and CPT; (iii) out of other cancer cell lines A549 and HeLa cells were sensitized to apoptosis induced by TRAIL and no line to apoptosis induced by CPT; (iv) unphosphorylable mutant of BID sensitized cells similarly as the wild type protein. The gene discussed is BID; the disease is cancer.