To characterise the mechanism of GUT-70-induced cell death in MCL cells, we analysed the expression of apoptosis-related Bcl-2 family proteins, the BH3-only proteins Noxa, Puma, and Bim, and the other Bcl-2 family proteins, Mcl-1 and BAK, in MCL cell lines. This evidence concerns the gene BAK1 and mantle cell lymphoma.