For example, in the lung cancer brain metastasis model constructed by the human NSCLC PC-9 cell line, Bcl-2 was also significantly upregulated, while Bcl-xl is not remarkably upregulated (Liu et al., 2021), suggesting that the expression of apoptosis-related proteins depends on the cancer cell lines. This evidence concerns the gene BCL2L1 and non-small cell lung carcinoma.