PER2 and cancer: Collectively, our work provided the evidences showing that PIWIL1 regulates circadian rhythms at least via two pathways in cancer cells: (a) To activate SRC‐PI3K‐AKT signalling pathway to phosphorylate and inactivate GSK3β, preventing CLOCK and BMAL1 from GSK3β‐induced phosphorylation and degradation; (b) To bind with E‐BOX region together with CLOCK/BMAL1 complex to repress the transcriptional activities of PER2 and CRY1 promoters (Figure 7).