PCNA and colorectal cancer: Nevertheless, some other binding partners, particularly those only identified in colorectal cancer HCT-8 cells (such as ATP synthase subunit beta, mitochondrial, and phosphoglucomutase-2) or only found in resistant A2780cis cells (such as proliferating cell nuclear antigen, polyubiquitin-B, and COP9 signalosome complex subunit 4), are worth investigating further in light of their relevance for intrinsic and acquired cisplatin resistance, respectively.