We demonstrate that the Smac mimetic BV6 and Dexa cooperate to trigger necroptotic cell death in acute lymphoblastic leukemia (ALL) cells that are deficient in caspase activation due to absent caspase-8 expression or pharmacological inhibition by the caspase inhibitor zVAD.fmk, since genetic silencing or pharmacological inhibition of RIP3 or MLKL significantly rescue BV6/Dexa-induced necroptosis.
Primary tumor cells from children with ALL were evaluated for expression levels of the caspase-8 protein, were amplified in nonobese diabetic/severe combined immunodeficient mice, transfected with siRNA, and evaluated for their chemosensitivity in vitro.
In the subgroup of primary ALL cells, with low expression of caspase-8, methotrexate (MTX) upregulated the expression of caspase-8 mediated by the transcription factor p53, suggesting epigenetic silencing of caspase-8.
Lower expression levels of CASP3, CASP8 and FAS gene were associated with a poor response at day 7 according the GBTLI-ALL 99 protocol (P = 0.03, P = 0.02 and P = 0.008, respectively).