BCL-XL inhibits apoptosis, while BCL-XS promotes apoptosis; BCL-XL is highly expressed in myeloid leukemia and indicates a poor prognosis, while BCL-XS is expressed at low levels in renal cancer, liver cancer, breast cancer, prostate cancer, and other tumor cell lines (5, 6). The gene discussed is BCL2L1; the disease is prostate carcinoma.