CASP3 and neoplasm: LPV-induced death of CSCs was accompanied by activated-caspase 3 (CASP3) expression and cleavage of the DNA repair enzyme poly (ADP-ribose) polymerase, that is, PARP-1, which represents a hallmark of apoptosis.35 Finally, in vivo treatment of mice with a fixed association of LPV and ritonavir (RTV) resulted in a reduction in allograft formation, indicating a beneficial effect on tumor regression.