Circadian genes and non-coding RNAs: interactions and implications in cancer.

Circadian rhythms are 24-hour cycles in various biological processes, such as sleep, wake, and hormone secretion, controlled by an internal clock. Disruption of circadian rhythms has been related to various human diseases. Abnormal expression of circadian rhythm-related genes, such as CLOCK, BMAL1, PER1, PER2, CRY1, CRY2, RORα, NPAS2, REV-ERBα and TIMELESS has also been reported to be associated with cancer. CLOCK, CRY1, NPAS2 and TIMELESS are related to cancer development. In contrast, BMAL1, PER1, PER2, CRY2, RORα and REV-ERBα related to inhibit cancer development and progression. Furthermore, studies suggest that circadian genes related to cancer can be regulated by ncRNAs such as miRNAs, lncRNAs and circRNAs and that dysregulation of these ncRNAs contributes to cancer development. Here, we summarize the mechanisms whereby ncRNA dysregulation leads to the abnormal expression of circadian genes in several cancers and the ncRNA and circadian gene-associated regulatory mechanisms that contribute to resistance to chemo - and radiotherapy. This review provides insights into the mechanistic involvements of the regulatory network of circadian genes and ncRNAs in cancer development.