A meta-analysis involving 7,476 cancer patients revealed that decreased PER1 gene expression was associated with poorer tumor differentiation and greater invasion depth, whereas reduced PER2 expression was correlated with advanced pathological stages and increased metastasis; furthermore, lower levels of both PER1 and PER2 were linked to shorter overall survivals (Zhang et al., 2020). Here, PER2 is linked to neoplasm.