Despite the therapeutic potential of PARP-1 inhibitors (such as olaparib), they can be used only for the treatment of tumors predominantly composed of HRR-deficient cells, since their use in a heterogeneous tumor cells population with a high rate of HRR-proficient cells can quickly lead to excessive growth of HRR-proficient clones and, therefore, to drug resistance [75,76]. Here, PARP1 is linked to neoplasm.