PER2 and renal cell carcinoma: To achieve a systematic understanding of the circadian clock in pan-RCC, we first selected 15 well-known circadian genes in this study, namely; NPAS2, PER2, DBP, ARNTL, PER3, NR1D1, CRY1, NR1D2, CLOCK, CRY2, BHLHE40, PER1, BHLHE41, RORA, and TIMELESS (Qiu et al., 2019).