The circadian gene Period2 plays an important role in tumor suppression and DNA damage response in vivo

Circadian disruption in cancer hallmarks: Novel insight into the molecular mechanisms of tumorigenesis and cancer treatment

Circadian rhythms are 24-h rhythms governing temporal organization of behavior and physiology generated by molecular clocks composed of autoregulatory transcription-translation feedback loops (TTFLs). Disruption of circadian rhythms leads to a spectrum of pathologies, including cancer by triggering or being involved in different hallmarks. Clock control of phenotypic plasticity involved in tumorigenesis operates in aberrant dedifferentiating to progenitor-like cell states, generation of cancer stem cells (CSCs) and epithelial-to-mesenchymal transition (EMT) events. Circadian rhythms might act as candidates for regulatory mechanisms of cellular senescent and functional determinants of senescence-associated secretory phenotype (SASP). Reciprocal control between clock and epigenetics sheds light on post-transcriptional regulation of circadian rhythms and opens avenues for novel anti-cancer strategies. Additionally, disrupting circadian rhythms influences microbiota communities that could be associated with altered homeostasis contributing to cancer development. Herein, we summarize recent advances in support of the nexus between disruptions of circadian rhythms and cancer hallmarks of new dimensions, thus providing novel perspectives on potentially effective treatment approaches for cancer management.

Functional and regulatory diversification of Period genes responsible for circadian rhythm in vertebrates

The Period genes (Per) play essential roles in modulating the molecular circadian clock timing in a broad range of species, which regulates the physiological and cellular rhythms through the transcription-translation feedback loop. While the Period gene paralogs are widely observed among vertebrates, the evolutionary history and the functional diversification of Per genes across vertebrates are not well known. In this study, we comprehensively investigated the evolution of Per genes at the copy number and sequence levels, including de novo binding motif discovery by comparative genomics. We also determined the lineage-specific transcriptome landscape across tissues and developmental stages and phenotypic effects in public RNA-seq data sets of model species. We observed multiple lineage-specific gain and loss events Per genes, though no simple association was observed between ecological factors and Per gene numbers in each species. Among salmonid fish species, the per3 gene has been lost in the majority, whereas those retaining the per3 gene exhibit not a signature of relaxed selective constraint but rather a signature of intensified selection. We also determined the signature of adaptive diversification of the CRY-binding region in Per1 and Per3, which modulates the circadian rhythm. We also discovered putative regulatory sequences, which are lineage-specific, suggesting that these cis-regulatory elements may have evolved rapidly and divergently across different lineages. Collectively, our findings revealed the evolution of Per genes and their fine-tuned contribution to the plastic and precise regulation of circadian rhythms in various vertebrate taxa.

circE2F1-encoded peptide inhibits circadian machinery essential for nucleotide biosynthesis and tumor progression via repressing SPIB/E2F1 axis

Circadian clock dominates a variety of biological activities, while its roles and regulatory mechanisms in neuroblastoma (NB), a pediatric extracranial malignancy, still remain largely elusive. Herein, through comprehensive analyses of public datasets, E2F transcription factor 1 (E2F1) and its circular RNA (circE2F1)-encoded 99-amino acid peptide (E2F1-99aa) were identified as vital regulators of circadian machinery essential for purine and pyrimidine biosynthesis during NB progression. Mechanistically, through interaction with Spi-B transcription factor (SPIB), E2F1 was transactivated to up-regulate circadian machinery genes (CRY1 and TIMELESS), resulting in relief of CLOCK/BMAL1-repressed transcription of enzymes (DHODH, PAICS, or PPAT) essential for de novo purine and pyrimidine biosynthesis. The biogenesis of circE2F1 was repressed by eukaryotic translation initiation factor 4A3 (EIF4A3), while E2F1-99aa or its truncated peptide competitively bound to SPIB, leading to decrease in SPIB-E2F1 interaction, circadian machinery and nucleotide biosynthetic gene expression, purine or pyrimidine biosynthesis, tumorigenesis, and aggresiveness of NB cells. In clinical NB cases, high EIF4A3, E2F1 or SPIB expression was correlated with low survival possibility of patients, while lower circE2F1 or E2F1-99aa levels were associated with advanced stages and tumor progression. These results indicate that circE2F1-encoded peptide inhibits circadian machinery essential for nucleotide biosynthesis and tumor progression via repressing SPIB/E2F1 axis.

Circadian rhythms and breast cancer: from molecular level to therapeutic advancements

BACKGROUND AND OBJECTIVES

Circadian rhythms, the endogenous biological clocks that govern physiological processes, have emerged as pivotal regulators in the development and progression of breast cancer. This comprehensive review delves into the intricate interplay between circadian disruption and breast tumorigenesis from multifaceted perspectives, encompassing biological rhythms, circadian gene regulation, tumor microenvironment dynamics, and genetic polymorphisms.

METHODS AND RESULTS

Epidemiological evidence underscores the profound impact of external factors, such as night shift work, jet lag, dietary patterns, and exercise routines, on breast cancer risk and progression through the perturbation of circadian homeostasis. The review elucidates the distinct roles of key circadian genes, including CLOCK, BMAL1, PER, and CRY, in breast cancer biology, highlighting their therapeutic potential as molecular targets. Additionally, it investigates how circadian rhythm dysregulation shapes the tumor microenvironment, fostering epithelial-mesenchymal transition, chronic inflammation, and immunosuppression, thereby promoting tumor progression and metastasis. Furthermore, the review sheds light on the association between circadian gene polymorphisms and breast cancer susceptibility, paving the way for personalized risk assessment and tailored treatment strategies.

CONCLUSIONS

Importantly, it explores innovative therapeutic modalities that harness circadian rhythms, including chronotherapy, melatonin administration, and traditional Chinese medicine interventions. Overall, this comprehensive review emphasizes the critical role of circadian rhythms in the pathogenesis of breast cancer and highlights the promising prospects for the development of circadian rhythm-based interventions to enhance treatment efficacy and improve patient outcomes.

The interplay of the circadian clock and metabolic tumorigenesis

The circadian clock and cell metabolism are both dysregulated in cancer cells through intrinsic cell-autonomous mechanisms and external influences from the tumor microenvironment. The intricate interplay between the circadian clock and cancer cell metabolism exerts control over various metabolic processes, including aerobic glycolysis, de novo nucleotide synthesis, glutamine and protein metabolism, lipid metabolism, mitochondrial metabolism, and redox homeostasis in cancer cells. Importantly, oncogenic signaling can confer a moonlighting function on core clock genes, effectively reshaping cellular metabolism to fuel cancer cell proliferation and drive tumor growth. These interwoven regulatory mechanisms constitute a distinctive feature of cancer cell metabolism.

The Biological Clock of Liver Metabolism in Metabolic Dysfunction-Associated Steatohepatitis Progression to Hepatocellular Carcinoma

Circadian rhythms are endogenous behavioral or physiological cycles that are driven by a daily biological clock that persists in the absence of geophysical or environmental temporal cues. Circadian rhythm-related genes code for clock proteins that rise and fall in rhythmic patterns driving biochemical signals of biological processes from metabolism to physiology and behavior. Clock proteins have a pivotal role in liver metabolism and homeostasis, and their disturbances are implicated in various liver disease processes. Encoded genes play critical roles in the initiation and progression of metabolic dysfunction-associated steatohepatitis (MASH) to hepatocellular carcinoma (HCC) and their proteins may become diagnostic markers as well as therapeutic targets. Understanding molecular and metabolic mechanisms underlying circadian rhythms will aid in therapeutic interventions and may have broader clinical applications. The present review provides an overview of the role of the liver's circadian rhythm in metabolic processes in health and disease, emphasizing MASH progression and the oncogenic associations that lead to HCC.

Prediction of lung adenocarcinoma prognosis and diagnosis with a novel model anchored in circadian clock-related genes

Lung adenocarcinoma is the most common primary lung cancer seen in the world, and identifying genetic markers is essential for predicting the prognosis of lung adenocarcinoma and improving treatment outcomes. It is well known that alterations in circadian rhythms are associated with a higher risk of cancer. Moreover, circadian rhythms play a regulatory role in the human body. Therefore, studying the changes in circadian rhythms in cancer patients is crucial for optimizing treatment. The gene expression data and clinical data were sourced from TCGA database, and we identified the circadian clock-related genes. We used the obtained TCGA-LUAD data set to build the model, and the other 647 lung adenocarcinoma patients' data were collected from two GEO data sets for external verification. A risk score model for circadian clock-related genes was constructed, based on the identification of 8 genetically significant genes. Based on ROC analyses, the risk model demonstrated a high level of accuracy in predicting the overall survival times of lung adenocarcinoma patients in training folds, as well as external data sets. This study has successfully constructed a risk model for lung adenocarcinoma prognosis, utilizing circadian rhythm as its foundation. This model demonstrates a dependable capacity to forecast the outcome of the disease, which can further guide the relevant mechanism of lung adenocarcinoma and combine behavioral therapy with treatment to optimize treatment decision-making.

Circadian rhythm disruption and endocrine-related tumors

This review delved into the intricate relationship between circadian clocks and physiological processes, emphasizing their critical role in maintaining homeostasis. Orchestrated by interlocked clock genes, the circadian timekeeping system regulates fundamental processes like the sleep-wake cycle, energy metabolism, immune function, and cell proliferation. The central oscillator in the hypothalamic suprachiasmatic nucleus synchronizes with light-dark cycles, while peripheral tissue clocks are influenced by cues such as feeding times. Circadian disruption, linked to modern lifestyle factors like night shift work, correlates with adverse health outcomes, including metabolic syndrome, cardiovascular diseases, infections, and cancer. We explored the molecular mechanisms of circadian clock genes and their impact on metabolic disorders and cancer pathogenesis. Specific associations between circadian disruption and endocrine tumors, spanning breast, ovarian, testicular, prostate, thyroid, pituitary, and adrenal gland cancers, are highlighted. Shift work is associated with increased breast cancer risk, with PER genes influencing tumor progression and drug resistance. CLOCK gene expression correlates with cisplatin resistance in ovarian cancer, while factors like aging and intermittent fasting affect prostate cancer. Our review underscored the intricate interplay between circadian rhythms and cancer, involving the regulation of the cell cycle, DNA repair, metabolism, immune function, and the tumor microenvironment. We advocated for integrating biological timing into clinical considerations for personalized healthcare, proposing that understanding these connections could lead to novel therapeutic approaches. Evidence supports circadian rhythm-focused therapies, particularly chronotherapy, for treating endocrine tumors. Our review called for further research to uncover detailed connections between circadian clocks and cancer, providing essential insights for targeted treatments. We emphasized the importance of public health interventions to mitigate lifestyle-related circadian disruptions and underscored the critical role of circadian rhythms in disease mechanisms and therapeutic interventions.

The circadian gene ARNTL2 promotes nasopharyngeal carcinoma invasiveness and metastasis through suppressing AMOTL2-LATS-YAP pathway

Metastasis is the major culprit of treatment failure in nasopharyngeal carcinoma (NPC). Aryl hydrocarbon receptor nuclear translocator like 2 (ARNTL2), a core circadian gene, plays a crucial role in the development of various tumors. Nevertheless, the biological role and mechanism of ARNTL2 are not fully elucidated in NPC. In this study, ARNTL2 expression was significantly upregulated in NPC tissues and cells. Overexpression of ARNTL2 facilitated NPC cell migration and invasion abilities, while inhibition of ARNTL2 in similarly treated cells blunted migration and invasion abilities in vitro. Consistently, in vivo xenograft tumor models revealed that ARNTL2 silencing reduced nude mice inguinal lymph node and lung metastases, as well as tumor growth. Mechanistically, ARNTL2 negatively regulated the transcription expression of AMOTL2 by directly binding to the AMOTL2 promoter, thus reducing the recruitment and stabilization of AMOTL2 to LATS1/2 kinases, which strengthened YAP nuclear translocation by suppressing LATS-dependent YAP phosphorylation. Inhibition of AMOTL2 counteracted the effects of ARNTL2 knockdown on NPC cell migration and invasion abilities. These findings suggest that ARNTL2 may be a promising therapeutic target to combat NPC metastasis and further supports the crucial roles of circadian genes in cancer development.

Circadian control of tumor immunosuppression affects efficacy of immune checkpoint blockade

The circadian clock is a critical regulator of immunity, and this circadian control of immune modulation has an essential function in host defense and tumor immunosurveillance. Here we use a single-cell RNA sequencing approach and a genetic model of colorectal cancer to identify clock-dependent changes to the immune landscape that control the abundance of immunosuppressive cells and consequent suppression of cytotoxic CD8+ T cells. Of these immunosuppressive cell types, PD-L1-expressing myeloid-derived suppressor cells (MDSCs) peak in abundance in a rhythmic manner. Disruption of the epithelial cell clock regulates the secretion of cytokines that promote heightened inflammation, recruitment of neutrophils and the subsequent development of MDSCs. We also show that time-of-day anti-PD-L1 delivery is most effective when synchronized with the abundance of immunosuppressive MDSCs. Collectively, these data indicate that circadian gating of tumor immunosuppression informs the timing and efficacy of immune checkpoint inhibitors.

The circadian clock affects starvation resistance through the pentose phosphate pathway in silkworm, Bombyx mori

Disruption of the circadian clock can affect starvation resistance, but the molecular mechanism is still unclear. Here, we found that starvation resistance was significantly reduced in the core gene BmPer deficient mutant silkworms (Per-/-), but the mutant's starvation resistance increased with larval age. Under natural physiological conditions, the weight of mutant 5th instar larvae was significantly increased compared to wild type, and the accumulation ability of triglycerides and glycogen in the fat bodies was upregulated. However, under starvation conditions, the weight consumption of mutant larvae was increased and cholesterol utilization was intensified. Transcriptome analysis showed that beta-oxidation was significantly upregulated under starvation conditions, fatty acid synthesis was inhibited, and the expression levels of genes related to mitochondrial function were significantly changed. Further investigations revealed that the redox balance, which is closely related to mitochondrial metabolism, was altered in the fat bodies, the antioxidant level was increased, and the pentose phosphate pathway, the source of reducing power in cells, was activated. Our findings suggest that one of the reasons for the increased energy burden observed in mutants is the need to maintain a more robust redox balance in metabolic tissues. This necessitates the diversion of more glucose into the pentose phosphate pathway to ensure an adequate supply of reducing power.

The circadian clock as a potential biomarker and therapeutic target in pancreatic cancer

Pancreatic cancer (PC) has a very high mortality rate globally. Despite ongoing efforts, its prognosis has not improved significantly over the last two decades. Thus, further approaches for optimizing treatment are required. Various biological processes oscillate in a circadian rhythm and are regulated by an endogenous clock. The machinery controlling the circadian cycle is tightly coupled with the cell cycle and can interact with tumor suppressor genes/oncogenes; and can therefore potentially influence cancer progression. Understanding the detailed interactions may lead to the discovery of prognostic and diagnostic biomarkers and new potential targets for treatment. Here, we explain how the circadian system relates to the cell cycle, cancer, and tumor suppressor genes/oncogenes. Furthermore, we propose that circadian clock genes may be potential biomarkers for some cancers and review the current advances in the treatment of PC by targeting the circadian clock. Despite efforts to diagnose pancreatic cancer early, it still remains a cancer with poor prognosis and high mortality rates. While studies have shown the role of molecular clock disruption in tumor initiation, development, and therapy resistance, the role of circadian genes in pancreatic cancer pathogenesis is not yet fully understood and further studies are required to better understand the potential of circadian genes as biomarkers and therapeutic targets.

Telomerase: a nexus between cancer nanotherapy and circadian rhythm

Cancer represents a complex disease category defined by the unregulated proliferation and dissemination of anomalous cells within the human body. According to the GLOBOCAN 2020 report, the year 2020 witnessed the diagnosis of approximately 19.3 million new cases of cancer and 10.0 million individuals succumbed to the disease. A typical cell eventually becomes cancerous because of a long-term buildup of genetic instability and replicative immortality. Telomerase is a crucial regulator of cancer progression as it induces replicative immortality. In cancer cells, telomerase inhibits apoptosis by elongating the length of the telomeric region, which usually protects the genome from shortening. Many nanoparticles are documented as being available for detecting the presence of telomerase, and many were used as delivery systems to transport drugs. Furthermore, telomere homeostasis is regulated by the circadian time-keeping machinery, leading to 24-hour rhythms in telomerase activity and TERT mRNA expression in mammals. This review provides a comprehensive discussion of various kinds of nanoparticles used in telomerase detection, inhibition, and multiple drug-related pathways, as well as enlightens an imperative association between circadian rhythm and telomerase activity from the perspective of nanoparticle-based anticancer therapeutics.

Circadian regulation of cancer stem cells and the tumor microenvironment during metastasis

The circadian clock regulates daily rhythms of numerous physiological activities through tightly coordinated modulation of gene expression and biochemical functions. Circadian disruption is associated with enhanced tumor formation and metastasis via dysregulation of key biological processes and modulation of cancer stem cells (CSCs) and their specialized microenvironment. Here, we review how the circadian clock influences CSCs and their local tumor niches in the context of different stages of tumor metastasis. Identifying circadian therapeutic targets could facilitate the development of new treatments that leverage circadian modulation to ablate tumor-resident CSCs, inhibit tumor metastasis and enhance response to current therapies.

Investigation of Common Pathways and Putative Biomarker Candidates of Colorectal Cancer and Insomnia by Using Integrative In-Silico Approaches

Background

Colorectal cancer (CRC) is one of the leading causes of cancer-related mortalities across the globe. Accumulating evidence shows that individuals having sleep disorders such as insomnia are at high risk of developing CRC, yet the association of sleep disorders with CRC risk is still unclear. Here, we investigated the potential molecular connections between CRC and insomnia using integrative in silico approaches.

Objective

This study aims to explore the potential molecular connections between CRC and insomnia utilizing integrative in-silico methodologies.

Methods and Methods

Gene expression microarray datasets for CRC and insomnia samples were retrieved from the NCBI-GEO database and analyzed using R. Functional enrichment analysis of common differentially expressed genes (DEGs) was performed by the g: Profiler tool. Cytoscape software was used to construct a protein-protein interaction network and hub gene identification. Expression profiles of hub genes in TCGA datasets were also determined, and predicted miRNAs targeting hub genes were analyzed by miRNA target prediction tools.

Results

Our results revealed a total of 113 shared DEGs between the CRC and insomnia datasets. Six genes (HSP8A, GAPDH, HSP90AA1, EEF1G, RPS6, and RPLP0), which were also differently expressed in TCGA datasets, were prioritized as hub genes and were found to be enriched in pathways related to protein synthesis. hsa-miR-324-3p, hsa-miR-769-3p, and hsa-miR-16-5p were identified as promising miRNA biomarkers for two diseases.

Conclusions

Our in-silico analysis provides promising evidence of the molecular link between CRC and insomnia and highlights multiple potential molecular biomarkers and pathways. Validation of the results by wet lab work can be utilized for novel translational and precision medicine applications to alleviate the public health burden of CRC.

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.

Learning from circadian rhythm to transform cancer prevention, prognosis, and survivorship care

Circadian timekeeping mechanisms and cell cycle regulation share thematic biological principles in responding to signals, repairing cellular damage, coordinating metabolism, and allocating cellular resources for optimal function. Recent studies show interactions between cell cycle regulators and circadian clock components, offering insights into potential cancer treatment approaches. Understanding circadian control of metabolism informs timing for therapies to reduce adverse effects and enhance treatment efficacy. Circadian adaptability to lifestyle factors, such as activity, sleep, and nutrition sheds light on their impact on cancer. Leveraging circadian regulatory mechanisms for cancer prevention and care is vital, as most risk stems from modifiable lifestyles. Monitoring circadian factors aids risk assessment and targeted interventions across the cancer care continuum.

Tumor circadian clock strength influences metastatic potential and predicts patient prognosis in luminal A breast cancer

Studies in shift workers and model organisms link circadian disruption to breast cancer. However, molecular circadian rhythms in noncancerous and cancerous human breast tissues and their clinical relevance are largely unknown. We reconstructed rhythms informatically, integrating locally collected, time-stamped biopsies with public datasets. For noncancerous breast tissue, inflammatory, epithelial-mesenchymal transition (EMT), and estrogen responsiveness pathways show circadian modulation. Among tumors, clock correlation analysis demonstrates subtype-specific changes in circadian organization. Luminal A organoids and informatic ordering of luminal A samples exhibit continued, albeit dampened and reprogrammed rhythms. However, CYCLOPS magnitude, a measure of global rhythm strength, varied widely among luminal A samples. Cycling of EMT pathway genes was markedly increased in high-magnitude luminal A tumors. Surprisingly, patients with high-magnitude tumors had reduced 5-y survival. Correspondingly, 3D luminal A cultures show reduced invasion following molecular clock disruption. This study links subtype-specific circadian disruption in breast cancer to EMT, metastatic potential, and prognosis.

Impact of Long-Lasting Environmental Factors on Regulation Mediated by the miR-34 Family

The present review focuses on the interactions of newly emerging environmental factors with miRNA-mediated regulation. In particular, we draw attention to the effects of phthalates, electromagnetic fields (EMFs) and a disrupted light/dark cycle. miRNAs are small non-coding RNA molecules with a tremendous regulatory impact, which is usually executed via gene expression inhibition. To address the capacity of environmental factors to influence miRNA-mediated regulation, the miR-34 family was selected for its well-described oncostatic and neuro-modulatory properties. The expression of miR-34 is in a tissue-dependent manner to some extent under the control of the circadian system. There is experimental evidence implicating that phthalates, EMFs and the circadian system interact with the miR-34 family, in both lines of its physiological functioning. The inhibition of miR-34 expression in response to phthalates, EMFs and light contamination has been described in cancer tissue and cell lines and was associated with a decline in oncostatic miR-34a signalling (decrease in p21 expression) and a promotion of tumorigenesis (increases in Noth1, cyclin D1 and cry1 expressions). The effects of miR-34 on neural functions have also been influenced by phthalates, EMFs and a disrupted light/dark cycle. Environmental factors shifted the effects of miR-34 from beneficial to the promotion of neurodegeneration and decreased cognition. Moreover, the apoptogenic capacity of miR-34 induced via phthalate administration in the testes has been shown to negatively influence germ cell proliferation. To conclude, as the oncostatic and positive neuromodulatory functions of the miR-34 family can be strongly influenced by environmental factors, their interactions should be taken into consideration in translational medicine.

The Diurnal Transcriptome Reveals the Reprogramming of Lung Adenocarcinoma Cells Under a Time-Restricted Feeding-Mimicking Regimen

BACKGROUND

The processes of tumor growth and circadian rhythm are intimately intertwined; thus, rewiring circadian metabolism by time-restricted feeding (TRF) may contribute to delaying carcinogenesis. However, research on the effect of a TRF cellular regimen on cancer is lacking.

OBJECTIVE

Investigate the circadian signatures of TRF in lung cancer in vitro.

METHODS

We first developed a cellular paradigm mimicking in vivo TRF and collected cells for transcriptome analysis. We further confirmed the effect on tumor cells upon 6-h TRF-mimicking (6-h TRFM) by real-time PCR, Lumicycle experiments, CCK-8, and flow cytometry assays.

RESULTS

We found that A549 lung adenocarcinoma cells treated with 6-h TRFM conditions displayed robust diurnal rhythms of transcriptomes, as well as modulation of the core clock genes relative to other different cellular regimens used in this study, including the fasting-mimicking conditions (ie, short-term starvation) and the serum-free regime. Notably, pathway analysis of oscillating genes exclusively in 6-h TRFM showed that some circadian genes were enriched in tumor-related pathways, such as the oxytocin signaling pathway, HIF-1 signaling pathway, and pentose and glucuronate interconversions. Moreover, in line with the circadian pathway enrichment results, 6-h TRFM robustly inhibited cell proliferation and induced cell apoptosis and cell cycle arrest in lung adenocarcinoma A549 cells, lung adenocarcinoma H460 cells, esophageal carcinoma Eca-109 cells, and breast adenocarcinoma MCF-7 cells.

CONCLUSIONS

Our findings provide the first in vitro mimicking medium for TRF intervention and indicate that 6-h TRFM is sufficient to reprogram the circadian signatures of lung adenocarcinoma cells and inhibit the progression of multiple tumors.

Nutrition and dietary restrictions in cancer prevention

The composition and pattern of dietary intake have emerged as key factors influencing aging, regeneration, and consequently, healthspan and lifespan. Cancer is one of the major diseases more tightly linked with aging, and age-related mortality. Although the role of nutrition in cancer incidence is generally well established, we are far from a consensus on how diet influences tumour development in different tissues. In this review, we will discuss how diet and dietary restrictions affect cancer risk and the molecular mechanisms potentially responsible for their effects. We will cover calorie restriction, intermittent fasting, prolonged fasting, fasting-mimicking diet, time-restricted eating, ketogenic diet, high protein diet, Mediterranean diet, and the vegan and vegetarian diets.

Multitissue Circadian Proteome Atlas of WT and Per1-/-/Per2-/- Mice

The molecular basis of circadian rhythm, driven by core clock genes such as Per1/2, has been investigated on the transcriptome level, but not comprehensively on the proteome level. Here we quantified over 11,000 proteins expressed in eight types of tissues over 46 h with an interval of 2 h, using WT and Per1/Per2 double knockout mouse models. The multitissue circadian proteome landscape of WT mice shows tissue-specific patterns and reflects circadian anticipatory phenomena, which are less obvious on the transcript level. In most peripheral tissues of double knockout mice, reduced protein cyclers are identified when compared with those in WT mice. In addition, PER1/2 contributes to controlling the anticipation of the circadian rhythm, modulating tissue-specific cyclers as well as key pathways including nucleotide excision repair. Severe intertissue temporal dissonance of circadian proteome has been observed in the absence of Per1 and Per2. The γ-aminobutyric acid might modulate some of these temporally correlated cyclers in WT mice. Our study deepens our understanding of rhythmic proteins across multiple tissues and provides valuable insights into chronochemotherapy. The data are accessible at https://prot-rhythm.prottalks.com/.

Hypoxia Induces Alterations in the Circadian Rhythm in Patients with Chronic Respiratory Diseases

The function of the circadian cycle is to determine the natural 24 h biological rhythm, which includes physiological, metabolic, and hormonal changes that occur daily in the body. This cycle is controlled by an internal biological clock that is present in the body's tissues and helps regulate various processes such as sleeping, eating, and others. Interestingly, animal models have provided enough evidence to assume that the alteration in the circadian system leads to the appearance of numerous diseases. Alterations in breathing patterns in lung diseases can modify oxygenation and the circadian cycles; however, the response mechanisms to hypoxia and their relationship with the clock genes are not fully understood. Hypoxia is a condition in which the lack of adequate oxygenation promotes adaptation mechanisms and is related to several genes that regulate the circadian cycles, the latter because hypoxia alters the production of melatonin and brain physiology. Additionally, the lack of oxygen alters the expression of clock genes, leading to an alteration in the regularity and precision of the circadian cycle. In this sense, hypoxia is a hallmark of a wide variety of lung diseases. In the present work, we intended to review the functional repercussions of hypoxia in the presence of asthma, chronic obstructive sleep apnea, lung cancer, idiopathic pulmonary fibrosis, obstructive sleep apnea, influenza, and COVID-19 and its repercussions on the circadian cycles.

Circadian Clock Dysregulation and Prostate Cancer: A Molecular and Clinical Overview

Circadian clock dysregulation has been implicated in various types of cancer and represents an area of growing research. However, the role of the circadian clock in prostate cancer has been relatively unexplored. This literature review will highlight the potential role of circadian clock dysregulation in prostate cancer by examining molecular, epidemiologic, and clinical data. The influence of melatonin, light, night shift work, chronotherapy, and androgen independence are discussed as they relate to the existing literature on their role in prostate cancer.

Watching the clock in glioblastoma

Glioblastoma (GBM) is the most prevalent malignant primary brain tumor, accounting for 14.2% of all diagnosed tumors and 50.1% of all malignant tumors, and the median survival time is approximately 8 months irrespective of whether a patient receives treatment without significant improvement despite expansive research (Ostrom QT, Price M, Neff C, et al. CBTRUS statistical report: primary brain and other central nervous system tumors diagnosed in the United States in 2015-2019. Neurooncology. 2022; 24(suppl 5):v1-v95.). Recently, important roles for the circadian clock in GBM tumorigenesis have been reported. Positive regulators of circadian-controlled transcription, brain and muscle ARNT-like 1 (BMAL1), and circadian locomotor output cycles kaput (CLOCK), are highly expressed also in GBM and correlated with poor patient prognosis. BMAL1 and CLOCK promote the maintenance of GBM stem cells (GSCs) and the establishment of a pro-tumorigenic tumor microenvironment (TME), suggesting that targeting the core clock proteins may augment GBM treatment. Here, we review findings that highlight the critical role the circadian clock plays in GBM biology and the strategies by which the circadian clock can be leveraged for GBM treatment in the clinic moving forward.

Glucose restriction induces AMPK-SIRT1-mediated circadian clock gene Per expression and delays NSCLC progression

The rhythmic expression of the circadian clock is intimately linked to the health status of the body. Disturbed circadian clock rhythms might lead to a wide range of metabolic diseases and even cancers. Our previous study showed that glucose restriction was able to inhibit non-small cell lung cancer (NSCLC). In the current study, we found that glucose restriction enhanced apoptosis and cell growth delay in NSCLC cells. In addition, we used GEPIA database analysis to derive different effects of each circadian clock gene on lung cancer tissue. Among these circadian clock genes, Per (Period) is lowly expressed in cancer tissues and highly expressed in normal tissues. Moreover, the higher expression of Per in cancer patients has a better prognostic significance. Furthermore, we revealed that glucose restriction induced the expression of the circadian clock gene Per in NSCLC cells by upregulating SIRT1 (Sirtuin1) via activation of the energy response factor AMPK (AMP-activated protein kinase). Changes in Per expression following upregulation or downregulation of AMPK were consistent with AMPK expression. Additionally, a low-carbohydrate ketogenic diet significantly delayed tumor progression in a xenograft tumor model of severe combined immunodeficiency (SCID) mice. Meanwhile, the ketogenic diet increased the expression of AMPK, SIRT1 and Per in vivo. Besides, the ketogenic diet was found to restore the normal rhythmic level of Per by Zeitgeber Time (ZT) experiments. Taken these together, these results indicated a novel mechanism that glucose restriction induces AMPK-SIRT1 mediated circadian clock gene Per expression and delays NSCLC progression, which provided more evidence for glucose restriction as an adjuvant clinical therapeutic strategy in NSCLC.

Effect of miR-34a on the expression of clock and clock-controlled genes in DLD1 and Lovo human cancer cells with different backgrounds with respect to p53 functionality and 17β-estradiol-mediated regulation

The small non-coding RNA miR-34a is a p53-regulated miRNA that acts as a tumour suppressor of colorectal cancer (CRC). Oncogenesis is also negatively influenced by deregulation of the circadian system in many types of tumours with various genetic backgrounds. As the clock gene per2 was recently recognized as one of the target genes of miR-34a, we focused on the miR-34a-mediated influence on the circadian oscillator in CRC cell lines DLD1 and LoVo, which differ in their p53 status. Previously, a sex-dependent association between the expression of per2 and that of miR-34a was demonstrated in CRC patients. Therefore, we also investigated the effect of 17β-estradiol (E2) on miR-34a oncostatic functions. miR-34a mimic caused a pronounced inhibition of per2 expression in both cell lines. Moreover, miR-34a mimic significantly inhibited bmal1 expression in LoVo and rev-erbα expression in DLD1 cells and induced clock gene expression in both cell lines. miR-34a mimic caused a pronounced decrease in sirt1 and cyclin D1 expression, which may be related to the inhibition of proliferation observed after mir-34a administration in DLD1 cells. E2 administration inhibited the migration and proliferation of DLD1 cells. E2 and miR-34a, when administered simultaneously, did not potentiate each other's effects. To conclude, miR-34a strongly influences the expression of components of the circadian oscillator without respect to p53 status and exerts its oncostatic effects via inhibition of sirt1 and cyclin D1 mRNA expression. E2 administration inhibits the growth of DLD1 cells; however, this effect seems to be independent of miR-34a-mediated action. With respect to the possible use of miR-34a in cancer treatment, clock genes can be considered as off-target genes, as changes in their expression induced by miR-34a treatment do not contribute to the oncostatic functions of miR-34a. Possible ambiguous oncogenic characteristics should be taken into consideration in future clinical studies focused on miR-34a.

Circadian disruption does not alter tumorigenesis in a mouse model of lymphoma

Background: Disruption of natural light cycles, as experienced by shift workers, is linked to enhanced cancer incidence. Several mouse models of cancer develop more severe disease when exposed to irregular light/dark cycles, supporting the connection between circadian disruption and increased cancer risk. Cryptochrome 2 (CRY2), a repressive component of the molecular circadian clock, facilitates turnover of the oncoprotein c-MYC, one mechanism that may link the molecular clock to tumorigenesis. In Eμ-MYC mice, which express transgenic c-MYC in B cells and develop aggressive lymphomas and leukemia, global Cry2 deletion reduces survival and enhances tumor formation. Lighting conditions that mimic the disruption experienced by shift workers dampen Cry2 transcripts in peripheral tissues of C57BL/6J mice. Although it is milder than homozygous deletion of Cry2, we hypothesized that reduced Cry2 rhythmicity could alter MYC protein accumulation and contribute to enhanced cancer risk caused by circadian disruption. We tested this hypothesis in MYC-driven lymphoma. Methods: We housed Eμ-MYC mice in light-tight boxes set to either control (continuous cycles of 12-hours of light followed by 12-hours of dark, LD12:12) or chronic jetlag (eight-hour light phase advances every two to three days, CJL) lighting conditions and assessed the impact of disrupted light cycles on survival and tumor formation in Eμ-MYC mice. Results: Environmental disruption of circadian rhythms did not alter tumor location, tumor growth, or survival in Eμ-MYC mice. Conclusions: Dampened rhythms of Cry2 following disruption of circadian light exposures is milder than deletion of Cry2. The lack of phenotype caused by altered circadian gene expression in contrast to enhanced tumorigenesis caused by homozygous deletion of Cry2 suggests that CRY2 dosage impacts this model. Importantly, these findings indicate that increased cancer risk associated with circadian disruption arises from one or more mechanisms that are not recapitulated here, and may be different in distinct tumor types.

Circadian disruption does not alter tumorigenesis in a mouse model of lymphoma

Background: Disruption of natural light cycles, as experienced by shift workers, is linked to enhanced cancer incidence. Several mouse models of cancer develop more severe disease when exposed to irregular light/dark cycles, supporting the connection between circadian disruption and increased cancer risk. Cryptochrome 2 (CRY2), a repressive component of the molecular circadian clock, facilitates turnover of the oncoprotein c-MYC, one mechanism that may link the molecular clock to tumorigenesis. In Eμ-MYC mice, which express transgenic c-MYC in B cells and develop aggressive lymphomas and leukemia, global Cry2 deletion reduces survival and enhances tumor formation. Lighting conditions that mimic the disruption experienced by shift workers dampen Cry2 transcripts in peripheral tissues of C57BL/6J mice. Although it is milder than homozygous deletion of Cry2, we hypothesized that reduced Cry2 rhythmicity could alter MYC protein accumulation and contribute to enhanced cancer risk caused by circadian disruption. We tested this hypothesis in MYC-driven lymphoma. Methods: We housed Eμ-MYC mice in light-tight boxes set to either control (continuous cycles of 12-hours of light followed by 12-hours of dark, LD12:12) or chronic jetlag (eight-hour light phase advances every two to three days, CJL) lighting conditions and assessed the impact of disrupted light cycles on survival and tumor formation in Eμ-MYC mice. Results: Environmental disruption of circadian rhythms did not alter tumor location, tumor growth, or survival in Eμ-MYC mice. Conclusions: Dampened rhythms of Cry2 following disruption of circadian light exposures is milder than deletion of Cry2. The lack of phenotype caused by altered circadian gene expression in contrast to enhanced tumorigenesis caused by homozygous deletion of Cry2 suggests that CRY2 dosage impacts this model. Importantly, these findings indicate that increased cancer risk associated with circadian disruption arises from one or more mechanisms that are not recapitulated here, and may be different in distinct tumor types.

Metabolic and chemical architecture of the mammalian circadian clock

Circadian rhythms are endogenous periodic biological processes that occur on a daily timescale. These rhythms are generated by a transcriptional/translational feedback loop that consists of the CLOCK-BMAL1 heterodimeric transcriptional activator complex and the PER1/2-CRY1/2-CK1δ/ε repressive complex. The output pathways of this molecular feedback loop generate circadian rhythmicity in various biological processes. Among these, metabolism is a primary regulatory target of the circadian clock which can also feedback to modulate clock function. This intertwined relationship between circadian rhythms and metabolism makes circadian clock components promising therapeutic targets. Despite this, pharmacological therapeutics that target the circadian clock are relatively rare. In this review, we hope to stimulate interest in chemical chronobiology by providing a comprehensive background on the molecular mechanism of mammalian circadian rhythms and their connection to metabolism, highlighting important studies in the chemical approach to circadian research, and offering our perspectives on future developments in the field.

Circadian, hormonal, and sleep rhythms: effects on cancer progression implications for treatment

Circadian, hormonal, and sleep rhythm disruptions are commonly experienced concerns among cancer patients throughout the cancer care continuum. This review aims to summarize the existing literature on circadian, hormonal, and sleep rhythms in the oncological population, focusing on circadian disruption and physiological and psychological abnormalities, disease progression, and chronomodulated treatment approaches. The findings demonstrate that subjectively and objectively measured circadian rhythm disruption is associated with adverse mental health and disease outcomes in patients with cancer. Chronomodulated chemotherapy, light therapy, cognitive behavioral therapy for insomnia, and physical activity have shown evidence of effectiveness in improving sleep, and occasionally, disease outcomes.

Research progresses on the effects of heavy metals on the circadian clock system

Environmental pollution with heavy metals is widespread, thus increasing attention has been paid to their toxic effects. Recent studies have suggested that heavy metals may influence the expression of circadian clock genes. Almost all organs and tissues exhibit circadian rhythms. The normal circadian rhythm of an organism is maintained by the central and peripheral circadian clock. Thus, circadian rhythm disorders perturb normal physiological processes. Here, we review the effects of heavy metals, including manganese, copper, cadmium, and lead, on four core circadian clock genes, i.e., ARNTL, CLOCK, PER, and CRY genes.

MYC disrupts transcriptional and metabolic circadian oscillations in cancer and promotes enhanced biosynthesis

The molecular circadian clock, which controls rhythmic 24-hour oscillation of genes, proteins, and metabolites in healthy tissues, is disrupted across many human cancers. Deregulated expression of the MYC oncoprotein has been shown to alter expression of molecular clock genes, leading to a disruption of molecular clock oscillation across cancer types. It remains unclear what benefit cancer cells gain from suppressing clock oscillation, and how this loss of molecular clock oscillation impacts global gene expression and metabolism in cancer. We hypothesized that MYC or its paralog N-MYC (collectively termed MYC herein) suppress oscillation of gene expression and metabolism to upregulate pathways involved in biosynthesis in a static, non-oscillatory fashion. To test this, cells from distinct cancer types with inducible MYC were examined, using time-series RNA-sequencing and metabolomics, to determine the extent to which MYC activation disrupts global oscillation of genes, gene expression pathways, and metabolites. We focused our analyses on genes, pathways, and metabolites that changed in common across multiple cancer cell line models. We report here that MYC disrupted over 85% of oscillating genes, while instead promoting enhanced ribosomal and mitochondrial biogenesis and suppressed cell attachment pathways. Notably, when MYC is activated, biosynthetic programs that were formerly circadian flipped to being upregulated in an oscillation-free manner. Further, activation of MYC ablates the oscillation of nutrient transporter proteins while greatly upregulating transporter expression, cell surface localization, and intracellular amino acid pools. Finally, we report that MYC disrupts metabolite oscillations and the temporal segregation of amino acid metabolism from nucleotide metabolism. Our results demonstrate that MYC disruption of the molecular circadian clock releases metabolic and biosynthetic processes from circadian control, which may provide a distinct advantage to cancer cells.

MYC disrupts transcriptional and metabolic circadian oscillations in cancer and promotes enhanced biosynthesis

The molecular circadian clock, which controls rhythmic 24-hour oscillation of genes, proteins, and metabolites in healthy tissues, is disrupted across many human cancers. Deregulated expression of the MYC oncoprotein has been shown to alter expression of molecular clock genes, leading to a disruption of molecular clock oscillation across cancer types. It remains unclear what benefit cancer cells gain from suppressing clock oscillation, and how this loss of molecular clock oscillation impacts global gene expression and metabolism in cancer. We hypothesized that MYC or its paralog N-MYC (collectively termed MYC herein) suppress oscillation of gene expression and metabolism to upregulate pathways involved in biosynthesis in a static, non-oscillatory fashion. To test this, cells from distinct cancer types with inducible MYC were examined, using time-series RNA-sequencing and metabolomics, to determine the extent to which MYC activation disrupts global oscillation of genes, gene expression pathways, and metabolites. We focused our analyses on genes, pathways, and metabolites that changed in common across multiple cancer cell line models. We report here that MYC disrupted over 85% of oscillating genes, while instead promoting enhanced ribosomal and mitochondrial biogenesis and suppressed cell attachment pathways. Notably, when MYC is activated, biosynthetic programs that were formerly circadian flipped to being upregulated in an oscillation-free manner. Further, activation of MYC ablates the oscillation of nutrient transporter proteins while greatly upregulating transporter expression, cell surface localization, and intracellular amino acid pools. Finally, we report that MYC disrupts metabolite oscillations and the temporal segregation of amino acid metabolism from nucleotide metabolism. Our results demonstrate that MYC disruption of the molecular circadian clock releases metabolic and biosynthetic processes from circadian control, which may provide a distinct advantage to cancer cells.

Lycium barbarum glycopeptide targets PER2 to inhibit lipogenesis in glioblastoma by downregulating SREBP1c

Lycium barbarum polysaccharide (LBP) is a substance with various biological activities extracted from Lycium barbarum. LbGPs are peptidoglycans with a short peptide backbone and a complex, branched glycan moiety, which is further extracted and isolated from LBPs. Previous studies have shown that LbGP can inhibit cancer cell growth, but its specific mechanism is not completely clear. In this study, we found that LbGP could inhibit the proliferation of glioma cells and promote the expression of period 2 (PER2) through the PKA-CREB pathway. In addition, LbGP could inhibit the de novo synthesis of lipids by downregulating SREBP1c and its target genes, which depended on the expression of PER2. Moreover, PER2 negatively regulated the expression of SREBP1c via suppressing PI3K/AKT/mTOR pathway. In summary, LbGP may upregulate the expression of PER2 to reduce the expression of SREBP1c, inhibit lipid synthesis in glioblastoma, and inhibit glioblastoma cell proliferation. This study provides an alternative drug for the treatment of glioma and elucidates its potential mechanism.

NR1D1 deficiency in the tumor microenvironment promotes lung tumor development by activating the NLRP3 inflammasome

Nuclear receptor Rev-erbα (NR1D1) is a major negative regulator of the circadian clock. Numerous studies have investigated the role of circadian clock-related factors in the tumorigenesis of multiple cancer types, but little is known about the role of NR1D1 in cancer development. In this study, we identified the role of NR1D1 in lung tumorigenesis using genetically engineered mouse models of Nr1d1. Although NR1D1 overexpression or knockdown had little effect on the proliferation of NSCLC cells in vitro, NR1D1 deficiency in the tumor microenvironment increased lung cancer development compared with the control in the orthotopic model. NR1D1-deficient mice showed increased NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome activation, and conditioned medium (CM) from NR1D1-deficient macrophages increased the proliferation and epithelial-mesenchymal transition (EMT) of lung cancer cells. Treatment with MCC950, a specific inhibitor of NLRP3 inflammasome, blocked tumorigenesis in NR1D1-deficient mice in an orthotopic lung cancer model. In addition, MCC950 treatment blocked the increased proliferation and EMT of cancer cells induced by CM from NR1D1-deficient macrophages in vitro. Our results showed that NR1D1 in the tumor microenvironment functions as a tumor suppressor by negatively regulating the NLRP3 inflammasome, suggesting that the NLRP3 inflammasome blockade via NR1D1 activation could be a therapeutic strategy to overcome lung cancer.

Chronotherapeutics for Solid Tumors

Circadian rhythms are internal manifestations of the 24-h solar day that allow for synchronization of biological and behavioral processes to the external solar day. This precise regulation of physiology and behavior improves adaptive function and survival. Chronotherapy takes advantage of circadian rhythms in physiological processes to optimize the timing of drug administration to achieve maximal therapeutic efficacy and minimize negative side effects. Chronotherapy for cancer treatment was first demonstrated to be beneficial more than five decades ago and has favorable effects across diverse cancer types. However, implementation of chronotherapy in clinic remains limited. The present review examines the evidence for chronotherapeutic treatment for solid tumors. Specifically, studies examining chrono-chemotherapy, chrono-radiotherapy, and alternative chronotherapeutics (e.g., hormone therapy, TKIs, antiangiogenic therapy, immunotherapy) are discussed. In addition, we propose areas of needed research and identify challenges in the field that remain to be addressed.

Differential expression of the circadian clock network correlates with tumour progression in gliomas

BACKGROUND

Gliomas are tumours arising mostly from astrocytic or oligodendrocytic precursor cells. These tumours are classified according to the updated WHO classification from 2021 in 4 grades depending on molecular and histopathological criteria. Despite novel multimodal therapeutic approaches, the vast majority of gliomas (WHO grade III and IV) are not curable. The circadian clock is an important regulator of numerous cellular processes and its dysregulation had been found during the progression of many cancers, including gliomas.

RESULTS

In this study, we explore expression patterns of clock-controlled genes in low-grade glioma (LGG) and glioblastoma multiforme (GBM) and show that a set of 45 clock-controlled genes can be used to distinguish GBM from normal tissue. Subsequent analysis identified 17 clock-controlled genes with a significant association with survival. The results point to a loss of correlation strength within elements of the circadian clock network in GBM compared to LGG. We further explored the progression patterns of mutations in LGG and GBM, and showed that tumour suppressor APC is lost late both in LGG and GBM. Moreover, HIF1A, involved in cellular response to hypoxia, exhibits subclonal losses in LGG, and TERT, involved in the formation of telomerase, is lost late in the GBM progression. By examining multi-sample LGG data, we find that the clock-controlled driver genes APC, HIF1A, TERT and TP53 experience frequent subclonal gains and losses.

CONCLUSIONS

Our results show a higher level of disrgulation at the gene expression level in GBM compared to LGG, and indicate an association between the differentially expressed clock-regulated genes and patient survival in both LGG and GBM. By reconstructing the patterns of progression in LGG and GBM, our data reveals the relatively late gains and losses of clock-regulated glioma drivers. Our analysis emphasizes the role of clock-regulated genes in glioma development and progression. Yet, further research is needed to asses their value in the development of new treatments.

The circadian clock, aging and its implications in cancer

Circadian clock orchestrates the intergenic biochemical, physiological and behavioral changes to form an approximate 24h oscillation through the transcription-translation feedback loop (TTFL). Mechanistically, a heterodimer of transcriptional activator formed by BMAL1 and CLOCK, governs the expression of its transcriptional repressors, CRY, PER and REV-ERBα/β proteins, thereby controlling more than 50 % of protein encoding genes in human. There is also increasing evidence showing that tumor microenvironment can disrupt specific clock gene functions to facilitate tumorigenesis. Although there is great progress in understanding the molecular mechanisms of the circadian clock, aging and cancer, elucidating their complex relationships among these processes remains challenging. Herein, the optimization of the chronochemotherapy regimen has not been justified yet for treatment of cancer. Here, we discuss the hypothesis of relocalization of chromatin modifiers (RCM) along with function(s) of the circadian rhythm on aging and carcinogenesis. We will also introduce the function of the chromatin remodeling as a new avenue for rejuvenation of competent tissues to combat aging and cancer.

Integrative analysis of circadian clock with prognostic and immunological biomarker identification in ovarian cancer

Objective: To identify circadian clock (CC)-related key genes with clinical significance, providing potential biomarkers and novel insights into the CC of ovarian cancer (OC). Methods: Based on the RNA-seq profiles of OC patients in The Cancer Genome Atlas (TCGA), we explored the dysregulation and prognostic power of 12 reported CC-related genes (CCGs), which were used to generate a circadian clock index (CCI). Weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network were used to identify potential hub genes. Downstream analyses including differential and survival validations were comprehensively investigated. Results: Most CCGs are abnormally expressed and significantly associated with the overall survival (OS) of OC. OC patients with a high CCI had lower OS rates. While CCI was positively related to core CCGs such as ARNTL, it also showed significant associations with immune biomarkers including CD8⁺ T cell infiltration, the expression of PDL1 and CTLA4, and the expression of interleukins (IL-16, NLRP3, IL-1β, and IL-33) and steroid hormones-related genes. WGCNA screened the green gene module to be mostly correlated with CCI and CCI group, which was utilized to construct a PPI network to pick out 15 hub genes (RNF169, EDC4, CHCHD1, MRPL51, UQCC2, USP34, POM121, RPL37, SNRPC, LAMTOR5, MRPL52, LAMTOR4, NDUFB1, NDUFC1, POLR3K) related to CC. Most of them can exert prognostic values for OS of OC, and all of them were significantly associated with immune cell infiltration. Additionally, upstream regulators including transcription factors and miRNAs of key genes were predicted. Conclusion: Collectively, 15 crucial CC genes showing indicative values for prognosis and immune microenvironment of OC were comprehensively identified. These findings provided insight into the further exploration of the molecular mechanisms of OC.

Circadian PER1 controls daily fat absorption with the regulation of PER1-PKA on phosphorylation of bile acid synthetase

Several epidemiological studies suggest a correlation between eating time and obesity. Night eating syndrome characterized by a time-delayed eating pattern is positively associated with obesity in humans as well as in experimental animals. Here, we show that oil intake at night significantly makes more fat than that at day in wild-type mice, and circadian Period 1 (Per1) contributes to this day-night difference. Per1-knockout mice are protected from high-fat diet-induced obesity, which is accompanied by a reduction in the size of the bile acid pool, and the oral administration of bile acids restores fat absorption and accumulation. We identify that PER1 directly binds to the major hepatic enzymes involved in bile acid synthesis such as cholesterol 7alpha-hydroxylase and sterol 12alpha-hydroxylase. A biosynthesis rhythm of bile acids is accompanied by the activity and instability of bile acid synthases with PER1/PKA-mediated phosphorylation pathways. Both fasting and high fat stress enhance Per1 expression, increasing the fat absorption and accumulation. Our findings reveal that Per1 is an energy regulator and controls daily fat absorption and accumulation. Circadian Per1 controls daily fat absorption and accumulation, suggesting Per1 is a potential candidate of a key regulator in stress response and the relevant obesity risk.

Subtype-specific circadian clock dysregulation modulates breast cancer biology, invasiveness, and prognosis

Studies in shift workers and model organisms link circadian disruption to breast cancer. However, molecular rhythms in non-cancerous and cancerous human breast tissues are largely unknown. We reconstructed rhythms informatically, integrating locally collected, time-stamped biopsies with public datasets. For non-cancerous tissue, the inferred order of core-circadian genes matches established physiology. Inflammatory, epithelial-mesenchymal transition (EMT), and estrogen responsiveness pathways show circadian modulation. Among tumors, clock correlation analysis demonstrates subtype-specific changes in circadian organization. Luminal A organoids and informatic ordering of Luminal A samples exhibit continued, albeit disrupted rhythms. However, CYCLOPS magnitude, a measure of global rhythm strength, varied widely among Luminal A samples. Cycling of EMT pathway genes was markedly increased in high-magnitude Luminal A tumors. Patients with high-magnitude tumors had reduced 5-year survival. Correspondingly, 3D Luminal A cultures show reduced invasion following molecular clock disruption. This study links subtype-specific circadian disruption in breast cancer to EMT, metastatic potential, and prognosis.

Circadian clocks in health and disease: Dissecting the roles of the biological pacemaker in cancer

In modern society, there is a growing population affected by circadian clock disruption through night shift work, artificial light-at-night exposure, and erratic eating patterns. Concurrently, the rate of cancer incidence in individuals under the age of 50 is increasing at an alarming rate, and though the precise risk factors remain undefined, the potential links between circadian clock deregulation and young-onset cancers is compelling. To explore the complex biological functions of the clock, this review will first provide a framework for the mammalian circadian clock in regulating critical cellular processes including cell cycle control, DNA damage response, DNA repair, and immunity under conditions of physiological homeostasis. Additionally, this review will deconvolute the role of the circadian clock in cancer, citing divergent evidence suggesting tissue-specific roles of the biological pacemaker in cancer types such as breast, lung, colorectal, and hepatocellular carcinoma. Recent evidence has emerged regarding the role of the clock in the intestinal epithelium, as well as new insights into how genetic and environmental disruption of the clock is linked with colorectal cancer, and the molecular underpinnings of these findings will be discussed. To place these findings within a context and framework that can be applied towards human health, a focus on how the circadian clock can be leveraged for cancer prevention and chronomedicine-based therapies will be outlined.

Interactions of circadian clock genes with the hallmarks of cancer

The molecular machinery of the circadian clock regulates the expression of many genes and processes in the organism, allowing the adaptation of cellular activities to the daily light-dark cycles. Disruption of the circadian rhythm can lead to various pathologies, including cancer. Thus, disturbance of the normal circadian clock at both genetic and environmental levels has been described as an independent risk factor for cancer. In addition, researchers have proposed that circadian genes may have a tissue-dependent and/or context-dependent role in tumorigenesis and may function both as tumor suppressors and oncogenes. Finally, circadian clock core genes may trigger or at least be involved in different hallmarks of cancer. Hence, expanding the knowledge of the molecular basis of the circadian clock would be helpful to identify new prognostic markers of tumorigenesis and potential therapeutic targets.

The impact of biological clock and sex hormones on the risk of disease

Molecular clocks are responsible for defining 24-h cycles of behaviour and physiology that are called circadian rhythms. Several structures and tissues are responsible for generating these circadian rhythms and are named circadian clocks. The suprachiasmatic nucleus of the hypothalamus is believed to be the master circadian clock receiving light input via the optic nerve and aligning internal rhythms with environmental cues. Studies using both in vivo and in vitro methodologies have reported the relationship between the molecular clock and sex hormones. The circadian system is directly responsible for controlling the synthesis of sex hormones and this synthesis varies according to the time of day and phase of the estrous cycle. Sex hormones also directly interact with the circadian system to regulate circadian gene expression, adjust biological processes, and even adjust their own synthesis. Several diseases have been linked with alterations in either the sex hormone background or the molecular clock. So, in this chapter we aim to summarize the current understanding of the relationship between the circadian system and sex hormones and their combined role in the onset of several related diseases.

Modeling the Circadian Control of the Cell Cycle and Its Consequences for Cancer Chronotherapy

The mammalian cell cycle is governed by a network of cyclin/Cdk complexes which signal the progression into the successive phases of the cell division cycle. Once coupled to the circadian clock, this network produces oscillations with a 24 h period such that the progression into each phase of the cell cycle is synchronized to the day-night cycle. Here, we use a computational model for the circadian clock control of the cell cycle to investigate the entrainment in a population of cells characterized by some variability in the kinetic parameters. Our numerical simulations showed that successful entrainment and synchronization are only possible with a sufficient circadian amplitude and an autonomous period close to 24 h. Cellular heterogeneity, however, introduces some variability in the entrainment phase of the cells. Many cancer cells have a disrupted clock or compromised clock control. In these conditions, the cell cycle runs independently of the circadian clock, leading to a lack of synchronization of cancer cells. When the coupling is weak, entrainment is largely impacted, but cells maintain a tendency to divide at specific times of day. These differential entrainment features between healthy and cancer cells can be exploited to optimize the timing of anti-cancer drug administration in order to minimize their toxicity and to maximize their efficacy. We then used our model to simulate such chronotherapeutic treatments and to predict the optimal timing for anti-cancer drugs targeting specific phases of the cell cycle. Although qualitative, the model highlights the need to better characterize cellular heterogeneity and synchronization in cell populations as well as their consequences for circadian entrainment in order to design successful chronopharmacological protocols.

The neural addiction of cancer

The recently uncovered key role of the peripheral and central nervous systems in controlling tumorigenesis and metastasis has opened a new area of research to identify innovative approaches against cancer. Although the 'neural addiction' of cancer is only partially understood, in this Perspective we discuss the current knowledge and perspectives on peripheral and central nerve circuitries and brain areas that can support tumorigenesis and metastasis and the possible reciprocal influence that the brain and peripheral tumours exert on one another. Tumours can build up local autonomic and sensory nerve networks and are able to develop a long-distance relationship with the brain through circulating adipokines, inflammatory cytokines, neurotrophic factors or afferent nerve inputs, to promote cancer initiation, growth and dissemination. In turn, the central nervous system can affect tumour development and metastasis through the activation or dysregulation of specific central neural areas or circuits, as well as neuroendocrine, neuroimmune or neurovascular systems. Studying neural circuitries in the brain and tumours, as well as understanding how the brain communicates with the tumour or how intratumour nerves interplay with the tumour microenvironment, can reveal unrecognized mechanisms that promote cancer development and progression and open up opportunities for the development of novel therapeutic strategies. Targeting the dysregulated peripheral and central nervous systems might represent a novel strategy for next-generation cancer treatment that could, in part, be achieved through the repurposing of neuropsychiatric drugs in oncology.

Single nucleotide polymorphisms (SNPs) in circadian genes: Impact on gene function and phenotype

Circadian rhythm is an endogenous timing system that allows an organism to anticipate and adapt to daily changes and regulate various physiological variables such as the sleep-wake cycle. This rhythm is governed by a molecular circadian clock mechanism, generated by a transcriptional and translational feedback loop (TTFL) mechanism. In mammals, TTFL is determined by the interaction of four main clock proteins: BMAL1, CLOCK, Cryptochromes (CRY), and Periods (PER). BMAL1 and CLOCK form dimers and initiate the transcription of clock-controlled genes (CCG) by binding an E-box element with the promotor genes. Among CCGs, PERs and CRYs accumulate in the cytosol and translocate into the nucleus, where they interact with the BMAL1/CLOCK dimer and inhibit its activity. Several epidemiological and genetic studies have revealed that circadian rhythm disruption causes various types of disease. In this chapter, we summarize the effect of core clock gene SNPs on circadian rhythm and diseases in humans.

"Time" for obesity-related cancer: The role of the circadian rhythm in cancer pathogenesis and treatment

The circadian rhythm is regulated by an intrinsic time-tracking system, composed both of a central and a peripheral clock, which influences the cycles of activities and sleep of an individual over 24 h. At the molecular level, the circadian rhythm begins when two basic helix-loop-helix/Per-ARNT-SIM (bHLH-PAS) proteins, BMAL-1 and CLOCK, interact with each other to produce BMAL-1/CLOCK heterodimers in the cytoplasm. The BMAL-1/CLOCK target genes encode for the repressor components of the clock, cryptochrome (Cry1 and Cry2) and the Period proteins (Per1, Per2 and Per3). It has been recently demonstrated that the disruption of circadian rhythm is associated with an increased risk of developing obesity and obesity-related diseases. In addition, it has been demonstrated that the disruption of the circadian rhythm plays a key role in tumorigenesis. Further, an association between the circadian rhythm disruptions and an increased incidence and progression of several types of cancer (e.g., breast, prostate, colorectal and thyroid cancer) has been found. As the perturbation of circadian rhythm has adverse metabolic consequences (e.g., obesity) and at the same time tumor promoter functions, this manuscript has the aim to report how the aberrant circadian rhythms affect the development and prognosis of different types of obesity-related cancers (breast, prostate, colon rectal and thyroid cancer) focusing on both human studies and on molecular aspects.

Circadian disruption: from mouse models to molecular mechanisms and cancer therapeutic targets

The circadian clock is a timekeeping system for numerous biological rhythms that contribute to the regulation of numerous homeostatic processes in humans. Disruption of circadian rhythms influences physiology and behavior and is associated with adverse health outcomes, especially cancer. However, the underlying molecular mechanisms of circadian disruption-associated cancer initiation and development remain unclear. It is essential to construct good circadian disruption models to uncover and validate the detailed molecular clock framework of circadian disruption in cancer development and progression. Mouse models are the most widely used in circadian studies due to their relatively small size, fast reproduction cycle, easy genome manipulation, and economic practicality. Here, we reviewed the current mouse models of circadian disruption, including suprachiasmatic nuclei destruction, genetic engineering, light disruption, sleep deprivation, and other lifestyle factors in our understanding of the crosstalk between circadian rhythms and oncogenic signaling, as well as the molecular mechanisms of circadian disruption that promotes cancer growth. We focused on the discoveries made with the nocturnal mouse, diurnal human being, and cell culture and provided several circadian rhythm-based cancer therapeutic strategies.