PARP1 and cancer: Furthermore, molecular biology studies show that B18L dysregulates cancer signaling pathways resulting in decreased Src and Erk1/2 phosphorylation, increased expression of pro-apoptotic Bcl2 proteins, caspase 3 cleavage products, as well as processing of the caspase substrate, poly (ADP-ribose) polymerase-1 (PARP-1), to the characteristic apoptotic fragment.