Interestingly, proteins involved in circadian rhythm control, e.g., PER, CRY, BMAL1, CLOCK, are highly expressed in the ovaries, where they regulate ovulation and hormonal cycles in general (43, 48), and alterations in their expression levels are associated with an increased risk of ovarian cancer and affect cancer growth, invasiveness, and drug sensitivity (49–51). Here, PER1 is linked to cancer.