Previous data from our research group also indicate remarkable differences in the levels of poly (ADP-ribose) polymerase-1 (PARP-1) enzyme between the drug-sensitive leukemia cell line (K562) and the most resistant leukemia cell line of our experimental model (FEPS), wherein only FEPS cells have detectable levels of the 24 kDa fragment of PARP-1 [26]. The gene discussed is PARP1; the disease is leukemia.