Analysis of the substrates of the MALT1 para-caspase activity in the Jurkat T-ALL model system including CYLD1, BCL10 and RelB revealed a distinct attenuated proteolysis of all tested MALT1 substrates upon GSK3β inhibition either by pharmacological inhibition with SB21 or SB41, or by specific shRNA (Figs 1, 3A–C). This evidence concerns the gene RELB and acute lymphoblastic leukemia.