PARP1 and neoplasm: As epigenetic silencing of the MLH1 promoter is commonly seen in tumours showing acquired resistance (Herman and Baylin, 2003), our work also suggests that combining strategies designed to reactivate the silenced MLH1 (such as treatment with DAC; Plumb et al, 2000) with SN1 methylating agents may promote PARP-mediated cell death.