PARP1 and neoplasm: Although it is far beyond the scope of this review, we should note that fundamental research on cell lines or mouse models has described several genetic/epigenetic mechanisms (e.g., PARP1 mutations, miRNA-622 overexpression) that explain PARPi resistance, mainly based on HR restoration, DNA replication fork protection, drug efflux through overexpression of multidrug resistance protein (MDR1) and impact of the tumor microenvironment [93,94,95,96].