MCL1 and cancer: In human cancer cells, the downregulation of pro-apoptotic proteins (e.g. Bax, Bak, Bad, Bim) and the upregulation of anti-apoptotic proteins (e.g. BCL-2, BCL-xl, MCL-1), inhibits the release of cytochrome c from mitochondria, leads to the immortal character of the cancer cells9.