Circadian disruption enhances HSF1 signaling and tumorigenesis in Kras-driven lung cancer

Epigenetic control of circadian clocks by environmental signals

Circadian clocks have evolved to enable organisms to respond to daily environmental changes. Maintaining a robust circadian rhythm under various perturbations and stresses is essential for the fitness of an organism. In the core circadian oscillator conserved in eukaryotes (from fungi to mammals), a negative feedback loop based on both transcription and translation drives circadian rhythms. The expression of circadian clock genes depends both on the binding of transcription activators at the promoter and on the chromatin state of the clock genes, and epigenetic modifications of chromatin are crucial for transcriptional regulation of circadian clock genes. Herein we review current knowledge of epigenetic regulation of circadian clock mechanisms and discuss how environmental cues can control clock gene expression by affecting chromatin states.

SE-lncRNAs in Cancer: Classification, Subcellular Localisation, Function and Corresponding TFs

Emerging evidence highlights certain long noncoding RNAs (lncRNAs) transcribed from or interacting with super-enhancer (SE) regulatory elements. These lncRNAs, known as SE-lncRNAs, are strongly linked to cancer and regulate cancer progression through multiple interactions with downstream targets. The expression of SE-lncRNAs is controlled by various transcription factors (TFs), and dysregulation of these TFs can contribute to cancer development. In this review, we discuss the characteristics, classification and subcellular distribution of SE-lncRNAs and summarise the role of key TFs in the transcription and regulation of SE-lncRNAs. Moreover, we examine the distinct functions and potential mechanisms of SE-lncRNAs in cancer progression.

Mini and enhanced CRISPR activators for cancer therapies

INTRODUCTION

The RNA-guided nuclease Cas9 can be used as a programmable transcription activator, but there is still room for improvement in its effectiveness in eukaryotes, and its potential in cancer genetic therapy has been poorly investigated.

OBJECTIVES

We aim to construct optimized CRISPRa tools and detect their potential role in cancer therapy by screening 9aa-TAD.

METHODS

We selected a range of transcriptional coactivators for programmable activation and analyzed their effects on the expression of multiple endogenous genes using Flow cytometry and qRT-PCR. In order to improve the activation capacity of the CRISPRa tool, we fused the coactivators with the efficient dCas9-VPR system to construct a new activation system. Utilize RNA-seq to assess the activation specificity of genome-wide. To evaluate the value of the newly constructed activation system in cancer gene therapy, we activated the expression of the tumor suppressor genes PER2 and ZNF382, and performed changes in cancer cell proliferation qRT-PCR and clonal formation analysis.

RESULTS

In this study, we screened the NHR module from C. elegans, which demonstrated a high transcription activation capacity with a compact size compared to VP64. We successfully demonstrated its efficiency in activating endogenous genes in mammalian cells. Furthermore, we developed an enhanced fused variant called NHR-VP64-p65-Rta (NVPR), which showed even higher efficiency compared to the previously established VPR module, making it an effective CRISPRa tool. The dCas9-NVPR complex also exhibited high specificity on a genome-wide scale. Finally, we utilized the dCas9-NVPR tool to restore the expression of tumor suppressor genes PER2 and ZNF382, effectively inhibiting the malignant phenotype of cancer cells.

CONCLUSION

We have successfully developed and demonstrated a breakthrough CRISPRa tool with promising implications for cancer genetic therapy. This innovation expands the range of available gene editing tools and further validates the immense potential of CRISPR-based approaches in precision medicine.

Circadian rhythms of macrophages are altered by the acidic tumor microenvironment

Tumor-associated macrophages (TAMs) are prime therapeutic targets due to their pro-tumorigenic functions, but varying efficacy of macrophage-targeting therapies highlights our incomplete understanding of how macrophages are regulated within the tumor microenvironment (TME). The circadian clock is a key regulator of macrophage function, but how circadian rhythms of macrophages are influenced by the TME remains unknown. Here, we show that conditions associated with the TME such as polarizing stimuli, acidic pH, and lactate can alter circadian rhythms in macrophages. While cyclic AMP (cAMP) has been reported to play a role in macrophage response to acidic pH, our results indicate pH-driven changes in circadian rhythms are not mediated solely by cAMP signaling. Remarkably, circadian disorder of TAMs was revealed by clock correlation distance analysis. Our data suggest that heterogeneity in circadian rhythms within the TAM population level may underlie this circadian disorder. Finally, we report that circadian regulation of macrophages suppresses tumor growth in a murine model of pancreatic cancer. Our work demonstrates a novel mechanism by which the TME influences macrophage biology through modulation of circadian rhythms.

Circadian system disorder induced by aberrantly activated EFNB2-EPHB2 axis leads to facilitated liver metastasis in gastric cancer

BACKGROUND

Liver is one of the most preferred destinations for distant metastasis of gastric cancer (GC) and liver metastasis usually predicts poor prognosis. The achievement of liver metastasis requires continued cross-talk of complex members in tumor microenvironment (TME) including tumor associated macrophages (TAMs).

METHODS

Results from 35 cases of ex vivo cultured living tissues of GC liver metastasis have elucidated that circadian rhythm disorder (CRD) of key molecules involved in circadian timing system (CTS) facilitates niche outgrowth. We next analyzed 69 cases of liver metastasis from patients bearing GC and designed co-culture or 3D cell culture, discovering that TAMs expressing EFNB2 could interact with tumor cell expressing EPHB2 for forward downstream signaling and lead to CRD of tumor cells. Moreover, we performed intrasplenic injection models assessed by CT combined 3D organ reconstruction bioluminescence imaging to study liver metastasis and utilized the clodronate treatment, bone marrow transplantation or EPH inhibitor for in vivo study followed by exploring the clinical therapeutic value of which in patient derived xenograft (PDX) mouse model.

RESULTS

Ex vivo studies demonstrated that CRD of key CTS molecules facilitates niche outgrowth in liver metastases. In vitro studies revealed that TAMs expressing EFNB2 interact with tumor cells expressing EPHB2, leading to CRD and downstream signaling activation. The underlying mechanism is the enhancement of the Warburg effect in metastatic niches.

CONCLUSION

Overall, we aim to uncover the mechanism in TAMs induced CRD which promotes liver metastasis of GC and provide novel ideas for therapeutic strategies.

Disruption of Circadian Clock Induces Abnormal Mammary Morphology and Aggressive Basal Tumorigenesis by Enhancing LILRB4 Signaling

Epidemiological studies have shown that circadian rhythm disruption (CRD) is associated with the risk of breast cancer. However, the role of CRD in mammary gland morphology and aggressive basal mammary tumorigenesis and the molecular mechanisms underlying CRD and cancer risk remain unknown. To investigate the effect of CRD on aggressive tumorigenesis, a genetically engineered mouse model that recapitulates the human basal type of breast cancer was used for this study. The effect of CRD on mammary gland morphology was investigated using wild-type mice model. The impact of CRD on the tumor microenvironment was investigated using the tumors from LD12:12 and CRD mice via scRNA seq. ScRNA seq was substantiated by multiplexing immunostaining, flow cytometry, and realtime PCR. The effect of LILRB4 immunotherapy on CRD-induced tumorigenesis was also investigated. Here we identified the impact of CRD on basal tumorigenesis and mammary gland morphology and identified the role of LILRB4 on CRD-induced lung metastasis. We found that chronic CRD disrupted mouse mammary gland morphology and increased tumor burden, and lung metastasis and induced an immunosuppressive tumor microenvironment by enhancing LILRB4a expression. Moreover, CRD increased the M2-macrophage and regulatory T-cell populations but decreased the M1-macrophage, and dendritic cell populations. Furthermore, targeted immunotherapy against LILRB4 reduced CRD-induced immunosuppressive microenvironment and lung metastasis. These findings identify and implicate LILRB4a as a link between CRD and aggressive mammary tumorigenesis. This study also establishes the potential role of the targeted LILRB4a immunotherapy as an inhibitor of CRD-induced lung metastasis.

The Circadian Rhythm of Itching among 241 Adults with Atopic Dermatitis: A Cross-sectional Study

The pattern of itching in patients with atopic dermatitis has not been systematically studied. Therefore, this study aimed to assess the pattern of itching in adults with atopic dermatitis using questionnaires to assess for a circadian rhythm of itching in participating patients at a single institution (n = 241). A self-report questionnaire was used to assess circadian rhythm and intensity of itching in patients. In addition, the patients' disease severity (Eczema Area and Severity Index [EASI]) and quality of life (Dermatology Life Quality Index [DLQI]) were assessed. Itching occurred most frequently (74.69%) and with the greatest severity (62.66%) between 20:00 and 00:00, and the least number of patients (25.31%) experienced itching between 04:00 and 08:00. The DLQI and EASI scores both correlated with the average and maximum itch intensity (r = 0.582, r = 0.533, respectively; r = 0.539, r = 0.517, respectively; p < 0.001). The DLQI and EASI scores were associated with average itch intensity (B = 0.179, B = 0.204, respectively; 95% CI: 0.112 to 0.246, 95% CI: 0.096 to 0.313, respectively; p < 0.001), and the EASI score was associated with males and family history (B = 0.285, B = 0.287, respectively; 95% CI: 0.094 to 0.476, 95% CI: 0.096 to 0.478, respectively; p = 0.003). Adult patients with atopic dermatitis exhibited a circadian rhythm of itching; these study results could positively impact treatment approaches.

Circadian rhythms of macrophages are altered by the acidic pH of the tumor microenvironment

Macrophages are prime therapeutic targets due to their pro-tumorigenic and immunosuppressive functions in tumors, but the varying efficacy of therapeutic approaches targeting macrophages highlights our incomplete understanding of how the tumor microenvironment (TME) can influence regulation of macrophages. The circadian clock is a key internal regulator of macrophage function, but how circadian rhythms of macrophages may be influenced by the tumor microenvironment remains unknown. We found that conditions associated with the TME such as polarizing stimuli, acidic pH, and elevated lactate concentrations can each alter circadian rhythms in macrophages. Circadian rhythms were enhanced in pro-resolution macrophages but suppressed in pro-inflammatory macrophages, and acidic pH had divergent effects on circadian rhythms depending on macrophage phenotype. While cyclic AMP (cAMP) has been reported to play a role in macrophage response to acidic pH, our results indicate that pH-driven changes in circadian rhythms are not mediated solely by the cAMP signaling pathway. Remarkably, clock correlation distance analysis of tumor-associated macrophages (TAMs) revealed evidence of circadian disorder in TAMs. This is the first report providing evidence that circadian rhythms of macrophages are altered within the TME. Our data further suggest that heterogeneity in circadian rhythms at the population level may underlie this circadian disorder. Finally, we sought to determine how circadian regulation of macrophages impacts tumorigenesis, and found that tumor growth was suppressed when macrophages had a functional circadian clock. Our work demonstrates a novel mechanism by which the tumor microenvironment can influence macrophage biology through altering circadian rhythms, and the contribution of circadian rhythms in macrophages to suppressing tumor growth.

Natural Compounds for Preventing Age-Related Diseases and Cancers

Aging is a multifaceted process influenced by hereditary factors, lifestyle, and environmental elements. As time progresses, the human body experiences degenerative changes in major functions. The external and internal signs of aging manifest in various ways, including skin dryness, wrinkles, musculoskeletal disorders, cardiovascular diseases, diabetes, neurodegenerative disorders, and cancer. Additionally, cancer, like aging, is a complex disease that arises from the accumulation of various genetic and epigenetic alterations. Circadian clock dysregulation has recently been identified as an important risk factor for aging and cancer development. Natural compounds and herbal medicines have gained significant attention for their potential in preventing age-related diseases and inhibiting cancer progression. These compounds demonstrate antioxidant, anti-inflammatory, anti-proliferative, pro-apoptotic, anti-metastatic, and anti-angiogenic effects as well as circadian clock regulation. This review explores age-related diseases, cancers, and the potential of specific natural compounds in targeting the key features of these conditions.

Environmental circadian disruption re-writes liver circadian proteomes

Circadian gene expression is fundamental to the establishment and functions of the circadian clock, a cell-autonomous and evolutionary-conserved timing system. Yet, how it is affected by environmental-circadian disruption (ECD) such as shiftwork and jetlag are ill-defined. Here, we provided a comprehensive and comparative description of male liver circadian gene expression, encompassing transcriptomes, whole-cell proteomes and nuclear proteomes, under normal and after ECD conditions. Under both conditions, post-translation, rather than transcription, is the dominant contributor to circadian functional outputs. After ECD, post-transcriptional and post-translational processes are the major contributors to whole-cell or nuclear circadian proteome, respectively. Furthermore, ECD re-writes the rhythmicity of 64% transcriptome, 98% whole-cell proteome and 95% nuclear proteome. The re-writing, which is associated with changes of circadian regulatory cis-elements, RNA-processing and protein localization, diminishes circadian regulation of fat and carbohydrate metabolism and persists after one week of ECD-recovery.

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.

Mapping stress-responsive signaling pathways induced by mitochondrial proteostasis perturbations

Imbalances in mitochondrial proteostasis are associated with pathologic mitochondrial dysfunction implicated in etiologically diverse diseases. This has led to considerable interest in defining the mechanisms responsible for regulating mitochondria in response to mitochondrial stress. Numerous stress-responsive signaling pathways have been suggested to regulate mitochondria in response to proteotoxic stress. These include the integrated stress response (ISR), the heat shock response (HSR), and the oxidative stress response (OSR). Here, we define the stress signaling pathways activated in response to chronic mitochondrial proteostasis perturbations by monitoring the expression of sets of genes regulated downstream of each of these signaling pathways in published Perturb-seq datasets from K562 cells CRISPRi-depleted of mitochondrial proteostasis factors. Interestingly, we find that the ISR is preferentially activated in response to chronic, genetically-induced mitochondrial proteostasis stress, with no other pathway showing significant activation. Further, we demonstrate that CRISPRi depletion of other mitochondria-localized proteins similarly shows preferential activation of the ISR relative to other stress-responsive signaling pathways. These results both establish our gene set profiling approach as a viable strategy to probe stress responsive signaling pathways induced by perturbations to specific organelles and identify the ISR as the predominant stress-responsive signaling pathway activated in response to chronic disruption of mitochondrial proteostasis.

Interorgan rhythmicity as a feature of healthful metabolism

The finding that animals with circadian gene mutations exhibit diet-induced obesity and metabolic syndrome with hypoinsulinemia revealed a distinct role for the clock in the brain and peripheral tissues. Obesogenic diets disrupt rhythmic sleep/wake patterns, feeding behavior, and transcriptional networks, showing that metabolic signals reciprocally control the clock. Providing access to high-fat diet only during the sleep phase (light period) in mice accelerates weight gain, whereas isocaloric time-restricted feeding during the active period enhances energy expenditure due to circadian induction of adipose thermogenesis. This perspective focuses on advances and unanswered questions in understanding the interorgan circadian control of healthful metabolism.

Embracing cancer complexity: Hallmarks of systemic disease

The last 50 years have witnessed extraordinary developments in understanding mechanisms of carcinogenesis, synthesized as the hallmarks of cancer. Despite this logical framework, our understanding of the molecular basis of systemic manifestations and the underlying causes of cancer-related death remains incomplete. Looking forward, elucidating how tumors interact with distant organs and how multifaceted environmental and physiological parameters impinge on tumors and their hosts will be crucial for advances in preventing and more effectively treating human cancers. In this perspective, we discuss complexities of cancer as a systemic disease, including tumor initiation and promotion, tumor micro- and immune macro-environments, aging, metabolism and obesity, cancer cachexia, circadian rhythms, nervous system interactions, tumor-related thrombosis, and the microbiome. Model systems incorporating human genetic variation will be essential to decipher the mechanistic basis of these phenomena and unravel gene-environment interactions, providing a modern synthesis of molecular oncology that is primed to prevent cancers and improve patient quality of life and cancer outcomes.

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.

Mapping Stress-Responsive Signaling Pathways Induced by Mitochondrial Proteostasis Perturbations

Imbalances in mitochondrial proteostasis are associated with pathologic mitochondrial dysfunction implicated in etiologically-diverse diseases. This has led to considerable interest in defining the biological mechanisms responsible for regulating mitochondria in response to mitochondrial stress. Numerous stress responsive signaling pathways have been suggested to regulate mitochondria in response to proteotoxic stress, including the integrated stress response (ISR), the heat shock response (HSR), and the oxidative stress response (OSR). Here, we define the specific stress signaling pathways activated in response to mitochondrial proteostasis stress by monitoring the expression of sets of genes regulated downstream of each of these signaling pathways in published Perturb-seq datasets from K562 cells CRISPRi-depleted of individual mitochondrial proteostasis factors. Interestingly, we find that the ISR is preferentially activated in response to mitochondrial proteostasis stress, with no other pathway showing significant activation. Further expanding this study, we show that broad depletion of mitochondria-localized proteins similarly shows preferential activation of the ISR relative to other stress-responsive signaling pathways. These results both establish our gene set profiling approach as a viable strategy to probe stress responsive signaling pathways induced by perturbations to specific organelles and identify the ISR as the predominant stress-responsive signaling pathway activated in response to mitochondrial proteostasis disruption.

Circadian misalignment impairs oligodendrocyte myelination via Bmal1 overexpression leading to anxiety and depression-like behaviors

Circadian misalignment (CM) caused by shift work can increase the risk of mood impairment. However, the pathological mechanisms underlying these deficits remain unclear. In the present study, we used long-term variable photoperiod (L-VP) in wild-type mice to better simulate real-life shift patterns and study its effects on the prefrontal cortex (PFC) and hippocampus, which are closely related to mood function. The results showed that exposure to L-VP altered the activity/rest rhythms of mice, by eliciting phase delay and decreased amplitude of the rhythms. Mice with CM developed anxiety and depression-like manifestations and the number of mature oligodendrocytes (OL) was reduced in the medial prefrontal cortex and hippocampal CA1 regions. Mood impairment and OL reduction worsened with increased exposure time to L-VP, while normal photoperiod restoration had no effect. Mechanistically, we identified upregulation of Bmal1 in the PFC and hippocampal regions of CM mice at night, when genes related to mature OL and myelination should be highly expressed. CM mice exhibited significant inhibition of the protein kinase B (AKT)/mTOR signaling pathway, which is directly associated to OL differentiation and maturation. Furthermore, we demonstrated in the OL precursor cell line Oli-Neu that overexpression of Bmal1 inhibits AKT/mTOR pathway and reduces the expression of genes OL differentiation. In conclusion, BMAL1 might play a critical role in CM, providing strong research evidence for BMAL1 as a potential target for CM therapy.

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.

Six-hour time-restricted feeding inhibits lung cancer progression and reshapes circadian metabolism

BACKGROUND

Accumulating evidence has suggested an oncogenic effect of diurnal disruption on cancer progression. To test whether targeting circadian rhythm by dietary strategy suppressed lung cancer progression, we adopted 6-h time-restricted feeding (TRF) paradigm to elucidate whether and how TRF impacts lung cancer progression.

METHODS

This study used multiple lung cancer cell lines, two xenograft mouse models, and a chemical-treated mouse lung cancer model. Stable TIM-knockdown and TIM-overexpressing A549 cells were constructed. Cancer behaviors in vitro were determined by colony formation, EdU proliferation, wound healing, transwell migration, flow cytometer, and CCK8 assays. Immunofluorescence, pathology examinations, and targeted metabolomics were also used in tumor cells and tissues. mCherry-GFP-LC3 plasmid was used to detect autophagic flux.

RESULTS

We found for the first time that compared to normal ad libitum feeding, 6-h TRF inhibited lung cancer progression and reprogrammed the rhythms of metabolites or genes involved in glycolysis and the circadian rhythm in tumors. After TRF intervention, only timeless (TIM) gene among five lung cancer-associated clock genes was found to consistently align rhythm of tumor cells to that of tumor tissues. Further, we demonstrated that the anti-tumor effect upon TRF was partially mediated by the rhythmic downregulation of the TIM and the subsequent activation of autophagy. Combining TRF with TIM inhibition further enhanced the anti-tumor effect, comparable to treatment efficacy of chemotherapy in xenograft model.

CONCLUSIONS

Six-hour TRF inhibits lung cancer progression and reshapes circadian metabolism, which is partially mediated by the rhythmic downregulation of the TIM and the subsequent upregulation of autophagy.

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.

Environmental circadian disruption re-programs liver circadian gene expression

Circadian gene expression is fundamental to the establishment and functions of the circadian clock, a cell-autonomous and evolutionary-conserved timing system. Yet, how it is affected by environmental-circadian disruption (ECD) such as shiftwork and jetlag, which impact millions of people worldwide, are ill-defined. Here, we provided the first comprehensive description of liver circadian gene expression under normal and after ECD conditions. We found that post-transcription and post-translation processes are dominant contributors to whole-cell or nuclear circadian proteome, respectively. Furthermore, rhythmicity of 64% transcriptome, 98% whole-cell proteome and 95% nuclear proteome is re-written by ECD. The re-writing, which is associated with changes of circadian cis-regulatory elements, RNA-processing and protein trafficking, diminishes circadian regulation of fat and carbohydrate metabolism and persists after one week of ECD-recovery.

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.

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.