Night shift schedule causes circadian dysregulation of DNA repair genes and elevated DNA damage in humans

Circadian-independent light regulation of mammalian metabolism

The daily light-dark cycle is a key zeitgeber (time cue) for entraining an organism's biological clock, whereby light sensing by retinal photoreceptors, particularly intrinsically photosensitive retinal ganglion cells, stimulates the suprachiasmatic nucleus of the hypothalamus, a central pacemaker that in turn orchestrates the rhythm of peripheral metabolic activities. Non-rhythmic effects of light on metabolism have also been long known, and their transduction mechanisms are only beginning to unfold. Here, we summarize emerging evidence that, in mammals, light exposure or deprivation profoundly affects glucose homeostasis, thermogenesis and other metabolic activities in a clock-independent manner. Such light regulation could involve melanopsin-based, intrinsically photosensitive retinal ganglion cell-initiated brain circuits via the suprachiasmatic nucleus of the hypothalamus and other nuclei, or direct stimulation of opsins expressed in the hypothalamus, adipose tissue, blood vessels and skin to regulate sympathetic tone, lipolysis, glucose uptake, mitochondrial activation, thermogenesis, food intake, blood pressure and melanogenesis. These photic signalling events may coordinate with circadian-based mechanisms to maintain metabolic homeostasis, with dysregulation of this system underlying metabolic diseases caused by aberrant light exposure, such as environmental night light and shift work.

Combined impact of sleep and obesity on female infertility in the NHANES 2017-2020

BACKGROUND

Sleep health and obesity may affect the risk of female infertility. However, few studies focused on the interaction of obesity and sleep health on the female infertility risk. This study aimed to evaluate the combined impact of trouble sleeping / sleep duration and overweight/obesity/ abdominal obesity on the risk of female infertility.

METHODS

The data for this cross-sectional study was obtained from National Health and Nutritional Examination Survey, which provided information on trouble sleeping, sleep duration, overweight/obesity, abdominal obesity, and confounding factors. Adopted weighted univariate and multivariate logistic regression models to explore the relationship between trouble sleeping, sleep duration, overweight/obesity, abdominal obesity, and the risk of infertility, respectively, and the combined effect of trouble sleeping and overweight/obesity, trouble sleeping and abdominal obesity, sleep duration and overweight/obesity, sleep duration and abdominal obesity, on the female infertility risk.

RESULTS

This study included a total of 1,577 women, and 191 were diagnosed with infertility. Women with infertility had a higher proportion of people with overweight/obesity, abdominal obesity, sleep duration ≤ 7 h and trouble sleeping than those with non-infertility. The result indicated that trouble sleeping [odds ratio (OR) = 2.25, 95% confidence intervals (CI): 1.49-3.39], sleep duration ≤ 7 h (OR = 1.59, 95% CI: 1.03-2.48), and the combined impact of abdominal obesity and trouble sleeping (OR = 2.18, 95% CI: 1.28-3.72), abdominal obesity and sleep duration ≤ 7 h (OR = 2.00, 95% CI: 1.17-3.40), overweight/obesity and trouble sleeping (OR = 2.29, 95% CI: 1.24-4.26), and overweight/obesity and sleep duration ≤ 7 h (OR = 1.88, 95% CI: 1.01-3.49) were associated with increased odds of infertility, respectively.

CONCLUSION

There was combined effects of trouble sleeping/sleep duration ≤ 7 h and overweight/obesity/ abdominal obesity on increased odds of female infertility.

Design of overnight radiology shifts - primum non nocere

Overnight radiology (ONR) is necessary for providing timely patient care but poses unique professional and personal challenges to the radiologists. Maintaining a sustainable, long-term overnight radiology program hinges on the retention of radiologists who grasp the institutional workflow and can adeptly navigate inherent disruptions while consistently delivering high-quality patient care. Design of radiology shifts can significantly impact the performance and well-being of radiologists, with downstream implications for patient care and risk management. We provide a narrative review of literature to make recommendations for optimally designing ONR shifts, with a focus on professional and personal challenges pertinent to overnight radiologists and system-based risk mitigation strategies.

Biological Clock Genes are Crucial and Promising Biomarkers for the Therapeutic Targets and Prognostic Assessment in Gastric Cancer

BACKGROUND

Gastric cancer is one of the major public health problems worldwide. Circadian rhythm disturbances driven by circadian clock genes play a role in the development of cancer. However, whether circadian clock genes can serve as potential therapeutic targets and prognostic biomarkers for gastric cancer remains elusive.

METHODS

In this study, we comprehensively analyzed the potential relationship between circadian clock genes and gastric cancer using online bioinformatics databases such as GEPIA, cBioPortal, STRING, GeneMANIA, Metascape, TIMER, TRRUST, and GEDS.

RESULTS

Biological clock genes are expressed differently in human tumors. Compared with normal tissues, only PER1, CLOCK, and TIMELESS expression differences were statistically significant in gastric cancer (p < 0.05). PER1 (p = 0.0169) and CLOCK (p = 0.0414) were associated with gastric cancer pathological stage (p < 0.05). Gastric cancer patients with high expression of PER1 (p = 0.0028) and NR1D1 (p = 0.016) had longer overall survival, while those with high expression of PER1 (p = 0.042) and NR1D1 (p = 0.016) had longer disease-free survival. The main function of the biological clock gene is related to the circadian rhythms and melatonin metabolism and effects. CLOCK, NPAS2, and KAT2B were key transcription factors for circadian clock genes. In addition, we also found important correlations between circadian clock genes and various immune cells in the gastric cancer microenvironment.

CONCLUSIONS

This study may establish a new gastric cancer prognostic indicator based on the biological clock gene and develop new drugs for the treatment of gastric cancer using biological clock gene targets.

Chronic circadian rhythm disorder induces heart failure with preserved ejection fraction-like phenotype through the Clock-sGC-cGMP-PKG1 signaling pathway

Emerging evidence has documented that circadian rhythm disorders could be related to cardiovascular diseases. However, there is limited knowledge on the direct adverse effects of circadian misalignment on the heart. This study aimed to investigate the effect of chronic circadian rhythm disorder on heart homeostasis in a mouse model of consistent jetlag. The jetlag model was induced in mice by a serial 8-h phase advance of the light cycle using a light-controlled isolation box every 4 days for up to 3 months. Herein, we demonstrated for the first time that chronic circadian rhythm disorder established in the mouse jetlag model could lead to HFpEF-like phenotype such as cardiac hypertrophy, cardiac fibrosis, and cardiac diastolic dysfunction, following the attenuation of the Clock-sGC-cGMP-PKG1 signaling. In addition, clock gene knock down in cardiomyocytes induced hypertrophy via decreased sGC-cGMP-PKG signaling pathway. Furthermore, treatment with an sGC-activator riociguat directly attenuated the adverse effects of jetlag model-induced cardiac hypertrophy, cardiac fibrosis, and cardiac diastolic dysfunction. Our data suggest that circadian rhythm disruption could induce HFpEF-like phenotype through downregulation of the clock-sGC-cGMP-PKG1 signaling pathway. sGC could be one of the molecular targets against circadian rhythm disorder-related heart disease.

Molecular-Level Dysregulation of Insulin Pathways and Inflammatory Processes in Peripheral Blood Mononuclear Cells by Circadian Misalignment

Circadian misalignment due to night work has been associated with an elevated risk for chronic diseases. We investigated the effects of circadian misalignment using shotgun protein profiling of peripheral blood mononuclear cells taken from healthy humans during a constant routine protocol, which was conducted immediately after participants had been subjected to a 3-day simulated night shift schedule or a 3-day simulated day shift schedule. By comparing proteomic profiles between the simulated shift conditions, we identified proteins and pathways that are associated with the effects of circadian misalignment and observed that insulin regulation pathways and inflammation-related proteins displayed markedly different temporal patterns after simulated night shift. Further, by integrating the proteomic profiles with previously assessed metabolomic profiles in a network-based approach, we found key associations between circadian dysregulation of protein-level pathways and metabolites of interest in the context of chronic metabolic diseases. Endogenous circadian rhythms in circulating glucose and insulin differed between the simulated shift conditions. Overall, our results suggest that circadian misalignment is associated with a tug of war between central clock mechanisms controlling insulin secretion and peripheral clock mechanisms regulating insulin sensitivity, which may lead to adverse long-term outcomes such as diabetes and obesity. Our study provides a molecular-level mechanism linking circadian misalignment and adverse long-term health consequences of night work.

Circadian rhythm regulates the function of immune cells and participates in the development of tumors

Circadian rhythms are present in almost all cells and play a crucial role in regulating various biological processes. Maintaining a stable circadian rhythm is essential for overall health. Disruption of this rhythm can alter the expression of clock genes and cancer-related genes, and affect many metabolic pathways and factors, thereby affecting the function of the immune system and contributing to the occurrence and progression of tumors. This paper aims to elucidate the regulatory effects of BMAL1, clock and other clock genes on immune cells, and reveal the molecular mechanism of circadian rhythm's involvement in tumor and its microenvironment regulation. A deeper understanding of circadian rhythms has the potential to provide new strategies for the treatment of cancer and other immune-related diseases.

The association between night shift work and osteoporosis risk in adults: A cross-sectional analysis using NHANES

Purpose

Through this study, we assess whether night shift work increases the risk of osteoporosis, and explore the effects of age, gender, or lifestyle differences.

Methods

This cross-sectional study included the collection of data from a sample of the US adults who participated in the National Health and Nutrition Examination Survey (NHANES) over a 7.3-year period (2007-2008, 2009-2010, 2017-March2020), including 4408 participants (2351[52.8%] men and 2057[47.2%] women), with an age range of 20-80 years. The primary variables, health status, nutrition, harmful lifestyle habits, and bone mineral density (BMD), were segregated, and analyzed according to different work schedules. Linear regression models were conducted to evaluate correlations of night shift work and T-scores. Associations between night shift work and osteoporosis were examined using logistic regression analyses. All regression models were stratified by gender and age ≥50 years. Osteoporosis was defined as BMD at the femoral neck or total spine equal to or less than 2.5 standard deviations below the mean for youthful people of the same gender. All data were obtained using questionnaires and examinations collected in mobile examination center (MEC) from NHANES.

Results

After multivariate adjustment, night shift work was related to statistically significant decreases of the total spine in T-scores of females aged ≥50 years. Furthermore, night shift work of the overall population (OR = 2.31 [95% CI, 1.03-5.18]; P = 0.043) and females aged ≥50 years (OR = 4.6 [95% CI, 1.21-17.54]; P = 0.025) was related to an increased prevalence of osteoporosis.

Conclusion

Night shift work correlates with a higher risk of osteoporosis in the population of the US adults, with the combined effect of age, gender, and harmful lifestyle.

Chronobiology of the Tumor Microenvironment: Implications for Therapeutic Strategies and Circadian-Based Interventions

Numerous research works have emphasized the critical role that circadian rhythm plays in the tumor microenvironment (TME). The goal of clarifying chrono-pharmacological strategies for improving cancer treatment in clinical settings is a continuous endeavor. Consequently, to enhance the use of time-based pharmaceutical therapies in oncology, combining existing knowledge on circadian rhythms' roles within the TME is essential. This perspective elucidates the functions of circadian rhythms in the TME across various stages of cancer development, progression, and metastasis. Specifically, aging, angiogenesis, and inflammation are implicated in modulating circadian rhythm within the TME. Furthermore, circadian rhythm exerts a profound influence on current cancer treatments and thereby generates chronotheray to manage tumors. From a TME perspective, circadian rhythm offers promising opportunities for cancer prevention and treatment; nevertheless, further study is needed to address unanswered scientific problems.

Circadian rhythm-associated lncRNA RP11-414H17.5 as a key therapeutic target in osteosarcoma affects the tumor immune microenvironment and enhances malignancy

BACKGROUND

It has previously been proven that circadian rhythm disruption is associated with the incidence and deterioration of several tumors, which potentially leads to increased tumor susceptibility and a worse prognosis for tumor-bearing patients. However, their potential role in osteosarcoma has yet to be sufficiently investigated.

METHODS

Transcriptomic and clinical data of 84 osteosarcoma samples and 70 normal bone tissue samples were obtained from the TARGET and GTEx databases, circadian rhythm-related genes were obtained from Genecards, and circadian rhythm-related lncRNAs (CRLs) were obtained by Pearson correlation analysis, differential expression analysis, and protein-protein interaction (PPI) analysis. COX regression and LASSO regression were performed on the CRLs in order to construct a circadian rhythm-related prognostic prediction signature (CRPS). CRPS reliability was verified by Kaplan-Meier (KM), principal component analysis (PCA), nomogram, and receiver operating characteristic (ROC) curve. CRPS effects on the immune microenvironment of osteosarcoma were explored by enrichment analysis and immune infiltration analysis, and the effect of critical gene RP11-414H17.5 on osteosarcoma was experimentally verified.

RESULT

CRPS consisting of three CRLs was constructed and its area under the curve (AUC) values predicted that osteosarcoma prognosis reached 0.892 in the training group and 0.843 in the test group, with a p value of < 0.05 for the KM curve and stable performance across different clinical subgroups. PCA analysis found that CRPS could significantly distinguish between different risk subgroups, and exhibited excellent performance in the prediction of the immune microenvironment. The experiment verified that RP11-414H17.5 can promote metastasis and inhibit apoptosis of osteosarcoma cells.

CONCLUSION

The study revealed that circadian rhythm plays a crucial role in osteosarcoma progression and identified the impact of the key gene RP11-414H17.5 on osteosarcoma, which provides novel insights into osteosarcoma diagnosis and therapy.

Crosstalk Between Aging, Circadian Rhythm, and Melatonin

Circadian rhythms (CRs) are 24-hour periodic oscillations governed by an endogenous circadian pacemaker located in the suprachiasmatic nucleus (SCN), which organizes the physiology and behavior of organisms. Circadian rhythm disruption (CRD) is also indicative of the aging process. In mammals, melatonin is primarily synthesized in the pineal gland and participates in a variety of multifaceted intracellular signaling networks and has been shown to synchronize CRs. Endogenous melatonin synthesis and its release tend to decrease progressively with advancing age. Older individuals experience frequent CR disruption, which hastens the process of aging. A profound understanding of the relationship between CRs and aging has the potential to improve existing treatments and facilitate development of novel chronotherapies that target age-related disorders. This review article aims to examine the circadian regulatory mechanisms in which melatonin plays a key role in signaling. We describe the basic architecture of the molecular circadian clock and its functional decline with age in detail. Furthermore, we discuss the role of melatonin in regulation of the circadian pacemaker and redox homeostasis during aging. Moreover, we also discuss the protective effect of exogenous melatonin supplementation in age-dependent CR disruption, which sheds light on this pleiotropic molecule and how it can be used as an effective chronotherapeutic medicine.

Identify and validate circadian regulators as potential prognostic markers and immune infiltrates in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneity pathological malignant cancer with leading causes of morbidity and mortality. EGFR inhibitors, immune checkpoint inhibitors have become novel treatments. However, the mechanism still remained uncertain. Several studies have confirmed that the circadian rhythms induce multiple malignancies developing. We utilized multi-omics analysis to demonstrate the crosstalk between circadian clock genes and tumor microenvironment in HNSCC. Firstly, we performed the LASSO Cox regression analysis based on the 16 important clock genes. A 7-gene risk model was successfully established in TCGA and validated in GEO datasets. Next, CIBERSORT and ESTIMATE methods were performed to display the immune landscape of high risk and low risk groups, and the results showed that high abundance of mast cells activated, dendritic cells activated and neutrophils were positively correlated with poor OS. To further identify hub genes, Kaplan Meier plot was applied in all TCGA and GEO datasets and two hub genes (PER2, and PER3) were identified, especially PER3, which was found strongly associated with immune score, PDCD1, CD4 + and CD8 + T cells in HNSCCC. Moreover, to explore the innate mechanism of circadian-induced pathway, we constructed a circadian-related ceRNA regulatory network containing 34 lncRNAs, 3 miRNAs and 4 core circadian genes. In-vitro experiments also verified that Per2 or Per3 could suppressed the proliferation, migration and invasion of HNSC. This study unraveled the association between PER3 and prognosis in patients with HNSC and the innate mechanism remains to be elucidated.

The impact of shift-work light conditions on tissue-specific circadian rhythms of canonical clock genes: insights from a mouse model study

Background: The natural day-night cycle synchronizes our circadian rhythms, but modern work practices like night shifts disrupt this pattern, leading to increased exposure to nighttime light. This exposure is linked to various health issues. While some studies have explored the effects of night shifts on human circadian rhythms, there is limited research on the consequences of long-term exposure to shift-work light conditions. Rodents can provide valuable insights into these effects. This study aimed to examine how short- or long-term exposure to rotating shifts and chronic jetlag affects the core circadian oscillators in the liver and skin of mammals. Methods: C57BL/6J male mice were subjected to simulated shift-work light conditions, including short-term or long-term rotating shifts and chronic jet-lag conditions. Liver and skin samples were collected every four hours over a 24-hour period on the second day of constant darkness. RNA was extracted and qRT-PCR analysis was conducted to measure the circadian gene expression in liver and skin tissues. Circadian rhythm analysis using CircaCompare compared the control group to mice exposed to shift-work light conditions. Results: The liver's circadian clock is significantly altered in mice under long-term rotating shift conditions, with a lesser but still noticeable impact in mice experiencing chronic jetlag. However, short-term rotating shift conditions do not significantly affect the liver's circadian clock. Conversely, all three simulated shift conditions affect the skin's circadian clock, indicating that the skin clock is more sensitive to shift-work light conditions than the liver clock. Compared to the liver, the skin's circadian clock is greatly affected by long-term rotating shift conditions. Conclusions: The study findings indicate more pronounced disturbances in the canonical clock genes of the skin compared to the liver under simulated shift-work light conditions. These results suggest that the skin clock is more vulnerable to the effects of shift-work.

Chrono-modulated effects of external stressors on oxidative stress and damage in humans: A scoping review on night shift work

BACKGROUND

Oxidative stress and tissue damage (OSD) play a pivotal role as an early-stage process in chronic disease pathogenesis. However, there has been little research to better understand the temporal (χρόνος[chronos]) dimensions of OSD process associated with environmental (non-genetic, including behaviors/lifestyle) and/or occupational stressors, like night shift work. OSD processes have recently attracted attention in relation to time-resolved external stressor trajectories in personalized medicine (prevention) initiatives, as they seem to interact with circadian clock systems towards the improved delineation of the early stages of (chronic) disease process.

OBJECTIVES

This work critically reviewed human studies targeting the temporal dynamics of OSD and circadian clock system's activity in response to environmental/occupational stressors; the case of night shift work was examined.

METHODS

Being a key stressor influencing OSD processes and circadian rhythm, night shift work was evaluated as part of a scoping review of research in OSD, including inflammatory and metabolic processes to determine the extent of OSD research undertaken in human populations, methodologies, tools and biomarkers used and the extent that the temporal dimensions of exposure and biological effect(s) were accounted for. Online databases were searched for papers published from 2000 onwards, resulting in the selection of 53 original publications.

RESULTS AND DISCUSSION

The majority of studies (n = 41) took place in occupational settings, while the rest were conducted in the general population or patient groups. Most occupational studies targeted outcomes of oxidative stress/damage (n = 19), followed by the combination of OSD with inflammatory response (n = 10), and studies focused on metabolic outcomes (n = 12). Only a minor fraction of the studies measured biomarkers related to circadian rhythm, such as, melatonin, its metabolite, or cortisol. Night shift work was associated with select biomarkers of OSD and inflammation, albeit with mixed results. Although much progress in delineating the biological mechanisms of OSD process has been made, an equally thorough investigation on the temporal trajectory of OSD processes as triggered by environmental/occupational stressors in human studies has yet to fully evolve.

Shift Work as a Cardiovascular Disease Risk Factor: A Narrative Review

Shift work has emerged as a significant health concern in recent years, and research has revealed a link to circadian rhythm dysregulation and atherosclerosis, both of which can increase the risk of cardiovascular disease (CVD). Currently, there is a lack of updated reviews regarding the impact of shiftwork on CVD. Thus, the present narrative review aims to provide a comprehensive summary of the latest research on the relationship between shift work and CVD, identify potential gaps in the current knowledge, and highlight areas for future research. Database searches for peer-reviewed articles published between January 2013 to January 2023 on shift work associated CVD revealed many studies that found shift work is linked with increased prevalence of carotid artery plaque, increased arterial stiffness, and carotid artery intima-media thickness (IMT) all suggestive of a progression of atherosclerosis attributable to shift work. Hypertension, diabetes, and a sedentary lifestyle are known risks for CVD, and the results of the present study suggest that shift work should be added to that list. The elevation of inflammatory markers and DNA damage in shift workers may be linked to their increased progression of atherosclerosis and the positive association of shift work with coronary artery disease. There are minimal studies on mitigating approaches for shift work-related CVD, such as diet modification or exercise, emphasizing the need for further directed research in this area.

Mitochondria Need Their Sleep: Redox, Bioenergetics, and Temperature Regulation of Circadian Rhythms and the Role of Cysteine-Mediated Redox Signaling, Uncoupling Proteins, and Substrate Cycles

Although circadian biorhythms of mitochondria and cells are highly conserved and crucial for the well-being of complex animals, there is a paucity of studies on the reciprocal interactions between oxidative stress, redox modifications, metabolism, thermoregulation, and other major oscillatory physiological processes. To address this limitation, we hypothesize that circadian/ultradian interaction of the redoxome, bioenergetics, and temperature signaling strongly determine the differential activities of the sleep–wake cycling of mammalians and birds. Posttranslational modifications of proteins by reversible cysteine oxoforms, S-glutathionylation and S-nitrosylation are shown to play a major role in regulating mitochondrial reactive oxygen species production, protein activity, respiration, and metabolomics. Nuclear DNA repair and cellular protein synthesis are maximized during the wake phase, whereas the redoxome is restored and mitochondrial remodeling is maximized during sleep. Hence, our analysis reveals that wakefulness is more protective and restorative to the nucleus (nucleorestorative), whereas sleep is more protective and restorative to mitochondria (mitorestorative). The “redox–bioenergetics–temperature and differential mitochondrial–nuclear regulatory hypothesis” adds to the understanding of mitochondrial respiratory uncoupling, substrate cycling control and hibernation. Similarly, this hypothesis explains how the oscillatory redox–bioenergetics–temperature–regulated sleep–wake states, when perturbed by mitochondrial interactome disturbances, influence the pathogenesis of aging, cancer, spaceflight health effects, sudden infant death syndrome, and diseases of the metabolism and nervous system.

Prognostic biomarker NEIL3 and its association with immune infiltration in renal clear cell carcinoma

Background

Kidney renal clear cell carcinoma (KIRC) is a malignant tumor with a high degree of immune infiltration. Identifying immune biomarkers is essential for the treatment of KIRC. Studies have identified the potential of NEIL3 to modulate the immune microenvironment and promote tumor progression. However, the role of NEIL3 in KIRC remains uncertain. This study was to investigate the effect of NEIL3 on the prognosis and immune infiltration of patients with KIRC.

Methods

TCGA and GEO databases were used to study the expression of NEIL3 in KIRC. Cox regression analysis was used to examine the relationship between the expression of NEIL3 and clinicopathological variables and survival. Furthermore, Gene Set Cancer Analysis (GSCA) was applied to study the impact of NEIL3 methylation on outcomes of KIRC. Through gene ontology (GO) and Gene set enrichment (GSEA) analysis, the biological processes and signal pathways related to NEIL3 expression were identified. In addition, immune infiltration analysis was conducted via CIBERSORT analysis, ssGSEA analysis and TISIDB database.

Results

NEIL3 was overexpressed in KIRC, and it was significantly related with histologic grade, pathologic stage, T stage, M stage, and vital status of KIRC patients (P < 0.001). The expression of NEIL3 was associated with worse outcomes. Univariate and multivariate Cox analysis showed that NEIL3 may be an indicator of adverse outcomes in KIRC. GSEA analysis revealed that NEIL3 may be involved in signal pathways including cell cycle, DNA replication, mismatch repair, P53 signal pathway, and antigen processing and presentation. In addition, immune infiltration analysis showed a positive correlation between NEIL3 expression and multiple immune cells (activated CD8 T cells, activated dendritic cells, myeloid-derived suppressor cells, follicular helper T cells, and regulatory T cells) and immunoinhibitors (PD1, CTLA4, LAG3, TIGHT, IL10, and CD96).

Conclusion

NEIL3 is a potential independent biomarker of KIRC, which is relevant to immune infiltration.

Major roles of the circadian clock in cancer

Circadian rhythms are natural rhythms that widely exist in all creatures, and regulate the processes and physiological functions of various biochemical reactions. The circadian clock is critical for cancer occurrence and progression. Its function is regulated by metabolic activities, and the expression and transcription of various genes. This review summarizes the composition of the circadian clock; the biological basis for its function; its relationship with, and mechanisms in, cancer; its various functions in different cancers; the effects of anti-tumor treatment; and potential therapeutic targets. Research in this area is expected to advance understanding of circadian locomotor output cycles kaput (CLOCK) and brain and muscle ARNT-like protein 1 (BMAL1) in tumor diseases, and contribute to the development of new anti-tumor treatment strategies.

WITHDRAWN: Mitochondria need their sleep: Sleep-wake cycling and the role of redox, bioenergetics, and temperature regulation, involving cysteine-mediated redox signaling, uncoupling proteins, and substrate cycles

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Shining light on the transcriptome: Molecular regulatory networks leading to a fast-growth phenotype by continuous light in an environmentally sensitive teleost (Atherinopsidae)

Photoperiod can profoundly affect the physiology of teleost fish, including accelerated growth here defined as "fast growth phenotypes". However, molecular regulatory networks (MRNs) and biological processes being affected by continuous illumination and which allow some teleost species evident plasticity to thrive under this condition are not yet clear. Therefore, to provide a broad perspective of such mechanisms, Chirostoma estor fish were raised and sampled for growth under a simulated control (LD) 12 h Light: 12 h Dark or a continuous illumination (LL) 24 h Light: 0 h Dark since fertilization. The experiment lasted 12 weeks after hatching (wah), the time at which fish were sampled for growth, length, and whole-body cortisol levels. Additionally, 3 heads of fish from each treatment were used to perform a de novo transcriptome analysis using Next-Generation Sequencing. Fish in LL developed the fast growth phenotype with significant differences visible at 4 wah and gained 66% more mass by 12 wah than LD fish. Cortisol levels under LL were below basal levels at all times compared to fish in LD, suggesting circadian dysregulation effects. A strong effect of LL was observed in samples with a generalized down-regulation of genes except for Reactive Oxygen Species responses, genome stability, and growth biological processes. To our knowledge, this work is the first study using a transcriptomic approach to understand environmentally sensitive MRNs that mediate phenotypic plasticity in fish submitted to continuous illumination. This study gives new insights into the plasticity mechanisms of teleost fish under constant illumination.

Complex physiology and clinical implications of time-restricted eating

Time-restricted eating (TRE) is a dietary intervention that limits food consumption to a specific time window each day. The effect of TRE on body weight and physiological functions has been extensively studied in rodent models, which have shown considerable therapeutic effects of TRE and important interactions among time of eating, circadian biology, and metabolic homeostasis. In contrast, it is difficult to make firm conclusions regarding the effect of TRE in people because of the heterogeneity in results, TRE regimens, and study populations. In this review, we 1) provide a background of the history of meal consumption in people and the normal physiology of eating and fasting; 2) discuss the interaction between circadian molecular metabolism and TRE; 3) integrate the results of preclinical and clinical studies that evaluated the effects of TRE on body weight and physiological functions; 4) summarize other time-related dietary interventions that have been studied in people; and 4) identify current gaps in knowledge and provide a framework for future research directions.

DNA Holliday Junction: History, Regulation and Bioactivity

DNA Holliday junction (HJ) is a four-way stranded DNA intermediate that formed in replication fork regression, homology-dependent repair and mitosis, performing a significant role in genomic stability. Failure to remove HJ can induce an acceptable replication fork stalling and DNA damage in normal cells, leading to a serious chromosomal aberration and even cell death in HJ nuclease-deficient tumor cells. Thus, HJ is becoming an attractive target in cancer therapy. However, the development of HJ-targeting ligand faces great challenges because of flexile cavities on the center of HJs. This review introduces the discovery history of HJ, elucidates the formation and dissociation procedures of HJ in corresponding bio-events, emphasizes the importance of prompt HJ-removing in genome stability, and summarizes recent advances in HJ-based ligand discovery. Our review indicate that target HJ is a promising approach in oncotherapy.

Tumor markers and depression scores are predictive of non-suicidal self-injury behaviors among adolescents with depressive disorder: A retrospective study

Background

Non-suicidal self-injury (NSSI) is an important risk factor for suicide in adolescents with depressive disorders; therefore, it is important to predict NSSI occurrence as early as possible. Disturbances in biological rhythms are characteristic manifestations of depressive disorders and can lead to immune dysfunction, leading to changes in tumor markers. This study aimed to produce an index that utilizes tumor markers to predict NSSI behaviors among adolescents with depressive disorders.

Methods

A total of 120 hospitalized adolescent patients with depressive disorders aged 14–24 years were included in this study. Participants were divided into NSSI and non-NSSI groups based on self-reports using the Ottawa Self-Injury Inventory. Demographics, tumor marker concentrations, other peripheral blood indices, Hamilton Depression Rating Scale (HDRS) scores, and Hamilton Anxiety Rating Scale (HAMA) scores were compared between the two groups. Logistic regression analysis was conducted to develop a joint index, and a receiver operating characteristic (ROC) curve was created to predict NSSI behaviors among adolescents with depressive disorders.

Results

Compared with the non-NSSI group, the NSSI group had significantly higher insight, retardation, insomnia, hopelessness, psychiatric anxiety, total HDRS and HAMA scores, and significantly higher levels of cancer antigen 125 (CA-125), cancer antigen 19-9 (CA19-9), and carcinoembryonic antigen (CEA). In addition, a joint index was developed by combining CA-125, CA19-9, CEA, HDRS total score, HAMA total score and age using multiple logistic regression to predict NSSI behaviors. The area under the curve was 0.831, with a sensitivity and specificity of 0.734 and 0.891, respectively.

Conclusion

A combination of depression score, tumor marker levels, and age can identify NSSI behaviors among adolescents with depressive disorders.

Human Variation in DNA Repair, Immune Function, and Cancer Risk

DNA damage constantly threatens genome integrity, and DNA repair deficiency is associated with increased cancer risk. An intuitive and widely accepted explanation for this relationship is that unrepaired DNA damage leads to carcinogenesis due to the accumulation of mutations in somatic cells. But DNA repair also plays key roles in the function of immune cells, and immunodeficiency is an important risk factor for many cancers. Thus, it is possible that emerging links between inter-individual variation in DNA repair capacity and cancer risk are driven, at least in part, by variation in immune function, but this idea is underexplored. In this review we present an overview of the current understanding of the links between cancer risk and both inter-individual variation in DNA repair capacity and inter-individual variation in immune function. We discuss factors that play a role in both types of variability, including age, lifestyle, and environmental exposures. In conclusion, we propose a research paradigm that incorporates functional studies of both genome integrity and the immune system to predict cancer risk and lay the groundwork for personalized prevention.

Dynamic molecular choreography of circadian rhythm disorders (DMCRD): a prospective cohort study protocol

BACKGROUND

Circadian rhythm disorders (CRDs) are closely associated with the occurrence and development of various diseases, such as inflammatory and cardiovascular diseases, as well as tumors. The impact of a CRD on bodily health is a complex and comprehensive process, and its molecular mechanisms and signaling pathways are still unclear. We therefore aimed to investigate the molecular mechanism variation and adverse outcomes associated with CRDs in a prospective cohort of CRD cases and controls at term using multiomics data. The study has been tasked with developing a precise health promotion model for the prevention and management of CRDs.

METHODS

This will be a 5-year prospective cohort study centered on the health management of individuals with CRDs. One hundred volunteers were recruited and had undergone baseline specimen collection, health examination, and health assessment. All of them will be followed up every year using the same protocol, and their biological specimens will be subjected to multiomics analysis after standardized processing.

DISCUSSION

Longitudinal health examination, health assessment, and multiomics data will be analyzed to study the impact of CRDs on the volunteers' health status. The results of this study will promote the development of targeted health management programs based on precision medicine.

TRIAL REGISTRATION

The clinical study registration has been completed (Trial Registration No. ChiCTR2100047242 ).

Night shift work and depression among Chinese workers: the mediating role of sleep disturbances

BACKGROUND

Depression is considered as a global problem. Recently, the prevalence of depression among night shift workers has been attracting people's attention. This study aims to explore the associations among night shift work, shift frequency and depression among Chinese workers and to explore whether sleep disturbances are a critical factor.

METHODS

The cross-sectional survey consists of 787 autoworkers from a manufacturing plant in Fuzhou, China. Information about night shift work, shift frequency, depression, and sleep disturbances were collected from work records and responses to the Patient Health Questionnaire (PHQ-9) and the Pittsburgh Sleep Quality Index (PSQI). A mediation model was generated to examine relationship between night shift work, sleep disturbances, and depression.

RESULTS

Our results found that night shift work, shift frequency, sleep disturbances, and depression had positive and significant relationships in a sample of Chinese workers. Night shift work, shift frequency and sleep disturbances were associated with an increased risk of depression among workers (OR: 4.23, 95% CI 2.55-7.00; 3.91, 2.31-6.63; 6.91, 4.40-10.86, respectively). Subsequent mediation analysis found that the association between night shift work and depression appeared to be partially mediated by sleep disturbances.

CONCLUSION

These findings suggest that appropriate intervention and management strategies should be considered to alleviate the mental health burden of night shift workers.

Cosmeceutical Therapy: Engaging the Repercussions of UVR Photoaging on the Skin's Circadian Rhythm

Sunlight is an important factor in regulating the central circadian rhythm, including the modulation of our sleep/wake cycles. Sunlight had also been discovered to have a prominent influence on our skin’s circadian rhythm. Overexposure or prolonged exposure to the sun can cause skin photodamage, such as the formation of irregular pigmentation, collagen degradation, DNA damage, and even skin cancer. Hence, this review will be looking into the detrimental effects of sunlight on our skin, not only at the aspect of photoaging but also at its impact on the skin’s circadian rhythm. The growing market trend of natural-product-based cosmeceuticals as also caused us to question their potential to modulate the skin’s circadian rhythm. Questions about how the skin’s circadian rhythm could counteract photodamage and how best to maximize its biopotential will be discussed in this article. These discoveries regarding the skin’s circadian rhythm have opened up a completely new level of understanding of our skin’s molecular mechanism and may very well aid cosmeceutical companies, in the near future, to develop better products that not only suppress photoaging but remain effective and relevant throughout the day.

Circadian rhythms and cancers: the intrinsic links and therapeutic potentials

The circadian rhythm is an evolutionarily conserved time-keeping system that comprises a wide variety of processes including sleep-wake cycles, eating-fasting cycles, and activity-rest cycles, coordinating the behavior and physiology of all organs for whole-body homeostasis. Acute disruption of circadian rhythm may lead to transient discomfort, whereas long-term irregular circadian rhythm will result in the dysfunction of the organism, therefore increasing the risks of numerous diseases especially cancers. Indeed, both epidemiological and experimental evidence has demonstrated the intrinsic link between dysregulated circadian rhythm and cancer. Accordingly, a rapidly increasing understanding of the molecular mechanisms of circadian rhythms is opening new options for cancer therapy, possibly by modulating the circadian clock. In this review, we first describe the general regulators of circadian rhythms and their functions on cancer. In addition, we provide insights into the mechanisms underlying how several types of disruption of the circadian rhythm (including sleep-wake, eating-fasting, and activity-rest) can drive cancer progression, which may expand our understanding of cancer development from the clock perspective. Moreover, we also summarize the potential applications of modulating circadian rhythms for cancer treatment, which may provide an optional therapeutic strategy for cancer patients.

Metabolomics and the Multi-Omics View of Cancer

Cancer is widely regarded to be a genetic disease. Indeed, over the past five decades, the genomic perspective on cancer has come to almost completely dominate the field. However, this genome-only view is incomplete and tends to portray cancer as a disease that is highly heritable, driven by hundreds of complex genetic interactions and, consequently, difficult to prevent or treat. New evidence suggests that cancer is not as heritable or purely genetic as once thought and that it really is a multi-omics disease. As highlighted in this review, the genome, the exposome, and the metabolome all play roles in cancer’s development and manifestation. The data presented here show that >90% of cancers are initiated by environmental exposures (the exposome) which lead to cancer-inducing genetic changes. The resulting genetic changes are, then, propagated through the altered DNA of the proliferating cancer cells (the genome). Finally, the dividing cancer cells are nourished and sustained by genetically reprogrammed, cancer-specific metabolism (the metabolome). As shown in this review, all three “omes” play roles in initiating cancer. Likewise, all three “omes” interact closely, often providing feedback to each other to sustain or enhance tumor development. Thanks to metabolomics, these multi-omics feedback loops are now much more evident and their roles in explaining the hallmarks of cancer are much better understood. Importantly, this more holistic, multi-omics view portrays cancer as a disease that is much more preventable, easier to understand, and potentially, far more treatable.

Circadian disruption and cisplatin chronotherapy for mammary carcinoma

Solid tumors are commonly treated with cisplatin, which can cause off-target side effects in cancer patients. Chronotherapy is a potential strategy to reduce drug toxicity. To determine the effectiveness of timed-cisplatin treatment in mammals, we compared two conditions: clock disrupted jet-lag and control conditions. Under normal and disrupted clock conditions, triple-negative mammary carcinoma cells were injected subcutaneously into eight-week-old NOD.Cg-Prkdc^scid/J female mice. Tumor volumes and body weights were measured in these mice before and after treatment with cisplatin. We observed an increase in tumor volumes in mice housed under disrupted clock compared to the normal clock conditions. After treatment with cisplatin, we observed a reduced tumor growth rate in mice treated at ZT10 compared to ZT22 and untreated cohorts under normal clock conditions. However, these changes were not seen with the jet-lag protocol. We also observed greater body weight loss in mice treated with ZT10 compared to ZT22 or untreated mice in the jet-lag protocol. Our observations suggest that the effectiveness of cisplatin in mammary carcinoma treatment is time-dependent in the presence of the circadian clock.

Circadian Clocks, Redox Homeostasis, and Exercise: Time to Connect the Dots?

Compelling research has documented how the circadian system is essential for the maintenance of several key biological processes including homeostasis, cardiovascular control, and glucose metabolism. Circadian clock disruptions, or losses of rhythmicity, have been implicated in the development of several diseases, premature ageing, and are regarded as health risks. Redox reactions involving reactive oxygen and nitrogen species (RONS) regulate several physiological functions such as cell signalling and the immune response. However, oxidative stress is associated with the pathological effects of RONS, resulting in a loss of cell signalling and damaging modifications to important molecules such as DNA. Direct connections have been established between circadian rhythms and oxidative stress on the basis that disruptions to circadian rhythms can affect redox biology, and vice versa, in a bi-directional relationship. For instance, the expression and activity of several key antioxidant enzymes (SOD, GPx, and CAT) appear to follow circadian patterns. Consequently, the ability to unravel these interactions has opened an exciting area of redox biology. Exercise exerts numerous benefits to health and, as a potent environmental cue, has the capacity to adjust disrupted circadian systems. In fact, the response to a given exercise stimulus may also exhibit circadian variation. At the same time, the relationship between exercise, RONS, and oxidative stress has also been scrutinised, whereby it is clear that exercise-induced RONS can elicit both helpful and potentially harmful health effects that are dependent on the type, intensity, and duration of exercise. To date, it appears that the emerging interface between circadian rhythmicity and oxidative stress/redox metabolism has not been explored in relation to exercise. This review aims to summarise the evidence supporting the conceptual link between the circadian clock, oxidative stress/redox homeostasis, and exercise stimuli. We believe carefully designed investigations of this nexus are required, which could be harnessed to tackle theories concerned with, for example, the existence of an optimal time to exercise to accrue physiological benefits.

Exogenous melatonin protects preimplantation embryo development from decabromodiphenyl ethane-induced circadian rhythm disorder and endogenous melatonin reduction

Decabromodiphenyl ethane (DBDPE) is a novel flame retardant that is widely used in plastics, electronic products, building materials and textiles. Our previous studies have revealed the oocyte toxicity of DBDPE, but the effect of DBDPE on preimplantation embryo development has not been reported. Here, we investigated whether and how DBDPE exposure affects preimplantation embryo development. Adult female mice were orally exposed to DBDPE (0, 5, 50, 500 μg/kg bw/day) for 14 days. First, we found that after DBDPE exposure, mice showed obvious circadian rhythm disorder. Moreover, the development of preimplantation embryos was inhibited in DBDPE-exposed mice after pregnancy. Then, we further explored and revealed that DBDPE exposure reduced the endogenous melatonin (MLT) level during pregnancy, thereby inhibiting the development of preimplantation embryos. Furthermore, we discovered that exogenous MLT supplementation (15 mg/kg bw/day) rescued the inhibition of preimplantation embryo development induced by DBDPE, and a mechanistic study demonstrated that exogenous MLT inhibited the overexpression of ROS and DNA methylation at the 5-position of cytosine (5-mC) in DBDPE-exposed preimplantation embryos. Simultaneously, MLT ameliorated the DBDPE-induced mitochondrial dysfunction by increasing the mitochondrial membrane potential (MMP), ATP, and Trp1 expression. Additionally, MLT restored DBDPE-induced changes in zona pellucida (ZP) hardness and trophectoderm (TE) cortical tension. Finally, the protective effect of MLT on embryos ameliorated the adverse reproductive outcomes (dead fetus, fetus with abnormal liver, fetal weight loss) induced by DBDPE. Collectively, DBDPE induced preimplantation embryo damage leading to adverse reproductive outcomes, and MLT has emerged as a potential tool to rescue adverse reproductive outcomes induced by DBDPE.

Circadian effects on UV-induced damage and mutations

Skin cancer is the most diagnosed type of cancer in the United States, and while most of these malignancies are highly treatable, treatment costs still exceed $8 billion annually. Over the last 50 years, the annual incidence of skin cancer has steadily grown; therefore, understanding the environmental factors driving these types of cancer is a prominent research-focus. A causality between ultraviolet radiation (UVR) exposure and skin cancer is well-established, but exposure to UVR alone is not necessarily sufficient to induce carcinogenesis. The emerging field of circadian biology intersects strongly with the physiological systems of the mammalian body and introduces a unique opportunity for analyzing mechanisms of homeostatic disruption. The circadian clock refers to the approximate 24-hour cycle, in which protein levels of specific clock-controlled genes (CCGs) fluctuate based on the time of day. Though these CCGs are tissue specific, the skin has been observed to have a robust circadian clock that plays a role in its response to UVR exposure. This in-depth review will detail the mechanisms of the circadian clock and its role in cellular homeostasis. Next, the skin's response to UVR exposure and its induction of DNA damage and mutations will be covered - with an additional focus placed on how the circadian clock influences this response through nucleotide excision repair. Lastly, this review will discuss current models for studying UVR-induced skin lesions and perturbations of the circadian clock, as well as the impact of these factors on human health.

Psychological intervention to treat distress: An emerging frontier in cancer prevention and therapy

Psychological distress, such as chronic depression and anxiety, is a topical problem. In the context of cancer patients, prevalence rates of psychological distress are four-times higher than in the general population and often confer worse outcomes. In addition to evidence from epidemiological studies confirming the links between psychological distress and cancer progression, a growing body of cellular and molecular studies have also revealed the complex signaling networks which are modulated by psychological distress-derived chronic stress during cancer progression. In this review, aiming to uncover the intertwined networks of chronic stress-driven oncogenesis and progression, we summarize physiological stress response pathways, like the HPA, SNS, and MGB axes, that modulate the release of stress hormones with potential carcinogenic properties. Furthermore, we discuss in detail the mechanisms behind these chronic stimulations contributing to the initiation and progression of cancer through direct regulation of cancer hallmarks-related signaling or indirect promotion of cancer risk factors (including obesity, disordered circadian rhythms, and premature senescence), suggesting a novel research direction into cancer prevention and therapy on the basis of psychological interventions.

Circadian regulation of cancer cell and tumor microenvironment crosstalk

Circadian rhythms regulate a remarkable variety of physiologic functions in living organisms. Circadian disruption is associated with tumorigenesis and tumor progression through effects on cancer cell biological properties, including proliferation, DNA repair, apoptosis, metabolism, and stemness. Emerging evidence indicates that circadian clocks also play an influential role in the tumor microenvironment (TME). This review outlines recent discoveries on how cancer cell clock components (including circadian clock and clock genes/proteins) regulate TME biology and, reciprocally, how TME clock components affect tumor growth, metastasis, and therapeutic response. An improved understanding of how clock components regulate the symbiosis between cancer cells and the TME will inform the development of novel clock-oriented therapeutic strategies, including immunotherapy.

Loss of diurnal behavioral rhythms and impaired lipid metabolism in growing pigs with mistimed feeding

The misalignment of eating time and the endogenous circadian rhythm impairs the body's ability to maintain homeostasis. Although it is well established that children and growing animals differ from adults in their energy metabolism and behavioral patterns, little is known about how mistimed feeding disturbs the diurnal rhythms of behavior and metabolism in children and growing diurnal animals. In this study, growing pigs (diurnal animal) were randomly assigned to the daytime-restricted feeding (DRF) and nighttime-restricted feeding (NRF) groups for 5 weeks. Compared with observations in the DRF group, NRF disrupted the diurnal rhythm of behavior and clock genes and lowered the serum ghrelin, dopamine, and serotonin levels during the daytime and nighttime. Microbiome analysis results suggested that NRF altered the diurnal rhythm and composition of the gut microbiota, and increased log-ratios of Catenibacterium:Butyrivibrio and Streptococcus:Butyrivibrio. Based on the serum proteome, the results further revealed that rhythmic and upregulated proteins in NRF were mainly involved in oxidative stress, lipid metabolism, immunity, and cancer biological pathways. Serum physiological indicators further confirmed that NRF decreased the concentration of melatonin and fibroblast growth factor 21 during the daytime and nighttime, increased the diurnal amplitude and concentrations of very-low-density lipoprotein cholesterol, triglyceride, and total cholesterol, and increased the apolipoprotein B/ApoA1 ratio, which is a marker of metabolic syndrome. Taken together, this study is the first to reveal that mistimed feeding disrupts the behavioral rhythms of growing pigs, reprograms gut microbiota composition, reduces the serum levels of hormones associated with fighting depression and anxiety, and increases the risk of lipid metabolic dysregulation.

Circadian Rhythms, Disease and Chronotherapy

Circadian clocks are biological timing mechanisms that generate 24-h rhythms of physiology and behavior, exemplified by cycles of sleep/wake, hormone release, and metabolism. The adaptive value of clocks is evident when internal body clocks and daily environmental cycles are mismatched, such as in the case of shift work and jet lag or even mistimed eating, all of which are associated with physiological disruption and disease. Studies with animal and human models have also unraveled an important role of functional circadian clocks in modulating cellular and organismal responses to physiological cues (ex., food intake, exercise), pathological insults (e.g. virus and parasite infections), and medical interventions (e.g. medication). With growing knowledge of the molecular and cellular mechanisms underlying circadian physiology and pathophysiology, it is becoming possible to target circadian rhythms for disease prevention and treatment. In this review, we discuss recent advances in circadian research and the potential for therapeutic applications that take patient circadian rhythms into account in treating disease.

TIMELESS Promotes Tumor Progression by Enhancing Macrophages Recruitment in Ovarian Cancer

Objective

Ovarian cancer (OV) is the most fatal and frequent type of gynecological malignancy worldwide. TIMELESS (TIM), as a circadian clock gene, has been found to be highly expressed and predictive of poor prognosis in various cancers. However, the function of TIM in OV is not known. This study was designed to investigate the biological functions and underlying mechanisms of TIM during OV progression.

Methods

Cell viability assay, cell migration assay, immunohistochemistry staining, qPCR analyses, and tumor xenograft model were used to identify the functions of TIM in OV. Bioinformatics analyses, including GEPIA, cBioPortal, GeneMANIA, and TIMER, were used to analyze the gene expression, genetic alteration, and immune cell infiltration of TIM in OV.

Results

TIM is highly expressed in OV patients. TIM knockdown inhibited OV cell proliferation, migration, and invasion both in vitro and in vivo. Genetic alteration of TIM was identified in patients with OV. TIM co-expression network indicates that TIM had a wide effect on the immune cell infiltration and activation in OV. Further analysis and experimental verification revealed that TIM was positively correlated with macrophages infiltration in OV.

Conclusions

Our study unveiled a novel function of highly expressed TIM associated with immune cell especially macrophages infiltration in OV. TIM may serve as a potential prognostic biomarker and immunotherapy target for OV patients.

MYC Ran Up the Clock: The Complex Interplay between MYC and the Molecular Circadian Clock in Cancer

The MYC oncoprotein and its family members N-MYC and L-MYC are known to drive a wide variety of human cancers. Emerging evidence suggests that MYC has a bi-directional relationship with the molecular clock in cancer. The molecular clock is responsible for circadian (~24 h) rhythms in most eukaryotic cells and organisms, as a mechanism to adapt to light/dark cycles. Disruption of human circadian rhythms, such as through shift work, may serve as a risk factor for cancer, but connections with oncogenic drivers such as MYC were previously not well understood. In this review, we examine recent evidence that MYC in cancer cells can disrupt the molecular clock; and conversely, that molecular clock disruption in cancer can deregulate and elevate MYC. Since MYC and the molecular clock control many of the same processes, we then consider competition between MYC and the molecular clock in several select aspects of tumor biology, including chromatin state, global transcriptional profile, metabolic rewiring, and immune infiltrate in the tumor. Finally, we discuss how the molecular clock can be monitored or diagnosed in human tumors, and how MYC inhibition could potentially restore molecular clock function. Further study of the relationship between the molecular clock and MYC in cancer may reveal previously unsuspected vulnerabilities which could lead to new treatment strategies.

The Time for Chronotherapy in Radiation Oncology

Five decades ago, Franz Halberg conceived the idea of ​​a circadian-based therapy for cancer, given the differential tolerance to treatment derived from the intrinsic host rhythms. Nowadays, different experimental models have demonstrated that both the toxicity and efficacy of several anticancer drugs vary by more than 50% as a function of dosing time. Accordingly, it has been shown that chemotherapeutic regimens optimally timed with the circadian cycle have jointly improved patient outcomes both at the preclinical and clinical levels. Along with chemotherapy, radiation therapy is widely used for cancer treatment, but its effectiveness relies mainly on its ability to damage DNA. Notably, the DNA damage response including DNA repair, DNA damage checkpoints, and apoptosis is gated by the circadian clock. Thus, the therapeutic potential of circadian-based radiotherapy against cancer is mainly dependent upon the control that the molecular clock exerts on DNA repair enzymes across the cell cycle. Unfortunately, the time of treatment administration is not usually considered in clinical practice as it varies along the daytime working hours. Currently, only a few studies have evaluated whether the timing of radiotherapy affects the treatment outcome. Several of these studies show that it is possible to reduce the toxicity of the treatment if it is applied at a specific time range, although with some inconsistencies. In this Perspective, we review the main advances in the field of chronoradiotherapy, the possible causes of the inconsistencies observed in the studies so far and provide some recommendations for future trials.