PARP1 and cancer: While PARP1 inhibition, on the one hand, has been shown effective in inducing synthetic lethality in XRCC1-deficient sporadic cancers (Ali et al. 2018, 2020), XRCC1 protein levels, on the other hand, demonstrate correlation with cancer resistance to CPT treatment, which is reversible by PARP inhibition (Park et al. 2002).