PER2 and neoplasm: As a crucial and powerful clock gene, Per2 has been found to be involved in physio/pathological pathways in tissue development (McQueen et al., 2018), cell differentiation (Huang et al., 2021), cell metabolism (Grimaldi et al., 2010), cell aging (Levine et al., 2020), tumor development (Guo et al., 2023), oxidative stress (Magnone et al., 2014), and neurobiological activities (Sayson et al., 2023).