We used human dermal fibroblasts immortalized by hTert, but not cancer cell lines such as HeLa cells, because cancers are often mutated in and lose expression of PARK2 gene, possibly due to the fragility of the PARK2 locus and long-term constitutive exposure of cancer cells to endogenous replication stress that is inherited into subsequent subpopulations6–11. This evidence concerns the gene PRKN and cancer.