Clocking onto chemotherapy to enhance cancer treatment

Awareness of the importance of circadian clocks has exploded in recent years. It is now well recognized that robust circadian rhythms improve health and well-being (Longo et al., 2021), and disruption of circadian clocks is associated with myriad chronic health issues, including cancer. However, there is still much to be understood about the mechanisms by which circadian rhythms influence the development, progression, and treatment of cancer. Epidemiological studies have demonstrated increased cancer rates in populations susceptible to circadian disruption, such as shift workers (Fagundo-Rivera et al., 2020, Pariollaud and Lamia, 2020). Furthermore, a strong body of evidence demonstrates that efficacy of chemotherapy differs depending on the time of day it is administered (Lévi, 1996), suggesting an interaction of treatment with the body’s internal circadian timing. The toxicity of chemotherapy may also be compounded if administered at inappropriate circadian phases (Hrushesky, 1985). In this issue of Brain, Behavior and Immunity, Sullivan et al (Sullivan et al., 2022) add a critical piece to this puzzle – they uncover that chemotherapy itself induces disruption of both central and peripheral circadian clocks. In other words, circadian timing affects cancer treatment efficacy, and this latest study shows that cancer treatment can also derange circadian clocks.