NPAS2 and Familial prostate cancer: Although a limited number of epidemiologic studies have been realized, several circadian genes have been implicated in prostate cancer regulation: ARNTL, CLOCK, CRY1-2, CSNK1e, MTNR1A and MTNR1B, NPAS2, NR1D1, PER1-3, RORA, RORB, and TIMELESS (4, 31, 56, 57).