PARP1 and neoplasm: in 2018 (16): using xenograft models (patient derived xenograft) or original tumor tissue transplanted into immunodeficient guinea pigs, the study demonstrated how the state of zygosity of the BRCA promoter methylation changes the response to PARP inhibitors (the drug implied in this case was Rucaparib), highlighting how the homozygous - hence of both alleles – methylation of BRCA was predictive of a good response to PARP-inhibitors, unlike heterozygous methylation which was, on the contrary, associated with resistance to therapy.