me resis tant after initial therapy, necessitating second and even third line treatment therapies. Thus, there is a need for additional new anti cancer drugs that induce specific cell death pathways in leukemia cells. It has recently been shown that the HIV protease inhibitor nelfinavir can induce cell death in a variety of human cancer types, and clinical studies with nelfinavir are currently INCB028050 proposed or underway. Nelfinavir appears to induce cell death in human cancer cells by rather pleiotropic mechanisms, including apoptosis, necrosis, and autophagy. Swelling of the endoplas mic reticulum by an accumulation of misfolded proteins appears to be a central mechanism in nelfinavir induced death in several cancer types, including lung cancer, glioma, and ovarian cancer cells, and precedes the activation of apoptosis.

Apoptosis can be induced by several pathways, includ ing an e trinsic pathway mediated by cell membrane bound death receptors and an intrinsic pathway mediated by activation of pro apoptotic intracellular mechanisms. Mitochondria play a central role in the induction and control of apoptosis because they harbour several apoptosis inducing proteins within their mem branes that can be released into the cytosol to induce caspase dependent cell death. Release of these mitochondrial factors occurs via outer mitochondrial membrane pore forma tion by pro apoptotic bcl 2 family members, such as ba , bak and t bid. The activities of these pro apoptotic molecules are counterbalanced by the anti apoptotic mitochondrial membrane proteins bcl 2, bcl L, and mcl 1.

Although there are several different the ories regarding how the pro and anti apoptotic bcl 2 family members interact, it has repeatedly been shown and is generally believed that increased e pres sion of pro apoptotic bcl 2 family members promotes cell death, whereas increased e pression of anti apopto tic bcl 2 family members facilitates cell survival. The most prominent anti apoptotic bcl 2 family members, including bcl 2, bcl L and mcl 1, were originally identified and found to be over e pressed in leukemia cells. Mcl 1 is a rather unique member of the bcl 2 family in that it has a rela tively large molecular weight of 40 42 kDa, compared to the molecular weight of ca. 26 kDa common to most other bcl 2 family members. Mcl 1 is a target of several pro apoptotic proteins and has been shown to undergo caspase mediated degradation during apoptosis.

Further, a shorter splice form of mcl 1 has been described and has been shown to e ert a pro apoptotic function. Thus, e pression Drug_discovery and modifica tion of mcl 1 appears to be crucial for regulation of cell survival and cell death in leukemia cells. In the present study, we show that despite its ability to induce apoptosis, nelfinavir enhances e pression of the mito chondria protective selleck chemicals mcl 1 protein in leukemia cells, resulting in a primarily mitochondria independent cas pase activation and cell death. Methods Cells and cell culture The human leukemia