Circadian Rhythms and Cancer Hallmarks: Toward Advances in Immune-Based Therapeutics, and Outcomes

Circadian rhythms are the daily fluctuations in physiological processes that govern cell cycles and timing of behaviors. Cancer hallmarks are the cellular properties that drive the perennial growth, survival and spread of cancerous cells. The disruption of circadian rhythms can contribute to the development of some cancers by affecting the expression of genes that regulate cell growth and division, as well as their interaction with the host microenvironment and anti-cancer treatment. Some cancer cells have been found to have altered circadian rhythms compared to normal cells, which may contribute to their uncontrolled growth. Patients exhibiting disrupted circadian rhythms tend to suffer accelerated tumor growth and metastasis, tumors that are more resistant to treatment, and poorer health-related quality of life and overall survival. Circadian rhythms also temporally regulate cellular immunity, which has important implications for the burgeoning field of immune-based therapeutics. Further research is needed to better understand the relationship between circadian rhythms and cancer hallmarks, and how this knowledge can be used to improve immunotherapy outcomes, cancer patients’ well-being and survival. This timely research topic is focused within a field that produced two Nobel prize awards in Physiology or Medicine, in 2017 for circadian rhythm research, and in 2018 for the discovery of cancer immunotherapy. The aim of this special issue is to highlight clinical, translational and epidemiological science - that includes objective assessments of both circadian disruption and cancer hallmarks - in order to help elucidate the impact of circadian rhythms on processes associated with cancer and its treatments, immunotherapy in particular.