Burkitt Lymphoma (BL) cells are highly sensitive to suboptimal growth conditions and undergo apoptosis when seeded at low cell density or reduced serum concentration. Irradiated fibroblasts or a mix of pruvate, alpha-thioglycerol, and bathocuproine disulfonate can protect BL cells from apoptosis induced by lowering cell density or serum concentration by promoting cystine uptake in the cells. The availability of cystine is the limiting factor for glutathione biosynthesis in BL cells and thus for the ability of the cells to cope with oxidative stress. We have set up an expression cloning strategy to clone genes that protect BL cells from apoptosis induced by low cell density and/or serum. Using this approach we have cloned among others the cDNA for Phospholipid Hydroperoxide Glutathione Peroxidase (PHGPx).