PARP1 and cancer: However, deregulation of H3K27me3 levels or macroH2A1 variant expression, and the associated HR defects, have both been linked to PARP inhibitor resistance, chromosomal abnormalities, and [...] PARP inhibitor resistance and chromosomal instability in cancer cells in cancer cells (Khurana et al., 2014; Karakashev et al., 2020).