RCC1 and cancer: Ras-related nuclear protein (Ran-GTP) can mediate the repair of DNA damage, while Ran-RCC1 inhibitory peptide (RAN-IP) derived from Ran protein sequence Ran-RCC1 inhibits the formation of Ran-GTP (Haggag et al., 2017; Haggag et al., 2019) by competitively binding to RCC1 (Haggag et al., 2020), which not only reduces the level of Ran-GTP but also makes the nuclear input and output pathways regulated by Ran-GTP defective, inhibiting its role in enhancing DNA repair in cancer cells.