Compared to normal skin, patients with skin cutaneous melanoma (SKCM) present significant down-regulation in the expression of BMAL1, CRY1, CRY2, PER1, PER2, and PER3, and higher expression of CLOCK (de Assis et al., 2018), a similar pattern was also observed in patients with colon adenocarcinoma (COAD) (Fuhr et al., 2018; Krugluger et al., 2007; Neilsen et al., 2019). The gene discussed is PER2; the disease is colon adenocarcinoma.