SIRT1 and circadian gene expression in pancreatic ductal adenocarcinoma: Effect of starvation

Hypermetabolic state is associated with circadian rhythm disruption in mouse and human cancer cells

Crosstalk between metabolism and circadian rhythms is a fundamental building block of multicellular life, and disruption of this reciprocal communication could be relevant to disease. Here, we investigated whether maintenance of circadian rhythms depends on specific metabolic pathways, particularly in the context of cancer. We found that in adult mouse fibroblasts, ATP levels were a major contributor to signal from a clock gene luciferase reporter, although not necessarily to the strength of circadian cycling. In contrast, we identified significant metabolic control of circadian function across a series of pancreatic adenocarcinoma cell lines. Metabolic profiling of congenic tumor cell clones revealed substantial diversity among these lines that we used to identify clones to generate circadian reporter lines. We observed diverse circadian profiles among these lines that varied with their metabolic phenotype: The most hypometabolic line [exhibiting low levels of oxidative phosphorylation (OxPhos) and glycolysis] had the strongest rhythms, while the most hypermetabolic line had the weakest rhythms. Pharmacological enhancement of OxPhos decreased the amplitude of circadian oscillation in a subset of tumor cell lines. Strikingly, inhibition of OxPhos enhanced circadian rhythms only in the tumor cell line in which glycolysis was also low, thereby establishing a hypometabolic state. We further analyzed metabolic and circadian phenotypes across a panel of human patient-derived melanoma cell lines and observed a significant negative association between metabolic activity and circadian cycling strength. Together, these findings suggest that metabolic heterogeneity in cancer directly contributes to circadian function and that high levels of glycolysis or OxPhos independently disrupt circadian rhythms in these cells.

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.

Hypermetabolic state is associated with circadian rhythm disruption in mouse and human cancer cells

Crosstalk between cellular metabolism and circadian rhythms is a fundamental building block of multicellular life, and disruption of this reciprocal communication could be relevant to degenerative disease, including cancer. Here, we investigated whether maintenance of circadian rhythms depends upon specific metabolic pathways, particularly in the context of cancer. We found that in adult mouse fibroblasts, ATP levels were a major contributor to overall levels of a clock gene luciferase reporter, although not necessarily to the strength of circadian cycling. In contrast, we identified significant metabolic control of circadian function in an in vitro mouse model of pancreatic adenocarcinoma. Metabolic profiling of a library of congenic tumor cell clones revealed significant differences in levels of lactate, pyruvate, ATP, and other crucial metabolites that we used to identify candidate clones with which to generate circadian reporter lines. Despite the shared genetic background of the clones, we observed diverse circadian profiles among these lines that varied with their metabolic phenotype: the most hypometabolic line had the strongest circadian rhythms while the most hypermetabolic line had the weakest rhythms. Treatment of these tumor cell lines with bezafibrate, a peroxisome proliferator-activated receptor (PPAR) agonist shown to increase OxPhos, decreased the amplitude of circadian oscillation in a subset of tumor cell lines. Strikingly, treatment with the Complex I antagonist rotenone enhanced circadian rhythms only in the tumor cell line in which glycolysis was also low, thereby establishing a hypometabolic state. We further analyzed metabolic and circadian phenotypes across a panel of human patient-derived melanoma cell lines and observed a significant negative association between metabolic activity and circadian cycling strength. Together, these findings suggest that metabolic heterogeneity in cancer directly contributes to circadian function, and that high levels of glycolysis or OxPhos independently disrupt circadian rhythms in these cells.

The Beneficial Roles of SIRT1 in Neuroinflammation-Related Diseases

Sirtuins are the class III of histone deacetylases whose deacetylate of histones is dependent on nicotinamide adenine dinucleotide (NAD+). Among seven sirtuins, SIRT1 plays a critical role in modulating a wide range of physiological processes, including apoptosis, DNA repair, inflammatory response, metabolism, cancer, and stress. Neuroinflammation is associated with many neurological diseases, including ischemic stroke, bacterial infections, traumatic brain injury, Alzheimer's disease (AD), and Parkinson's disease (PD). Recently, numerous studies indicate the protective effects of SIRT1 in neuroinflammation-related diseases. Here, we review the latest progress regarding the anti-inflammatory and neuroprotective effects of SIRT1. First, we introduce the structure, catalytic mechanism, and functions of SIRT1. Next, we discuss the molecular mechanisms of SIRT1 in the regulation of neuroinflammation. Finally, we analyze the mechanisms and effects of SIRT1 in several common neuroinflammation-associated diseases, such as cerebral ischemia, traumatic brain injury, spinal cord injury, AD, and PD. Taken together, this information implies that SIRT1 may serve as a promising therapeutic target for the treatment of neuroinflammation-associated disorders.

Circadian Dysregulation of the TGFβ/SMAD4 Pathway Modulates Metastatic Properties and Cell Fate Decisions in Pancreatic Cancer Cells

Impairment of circadian rhythms impacts carcinogenesis. SMAD4, a clock-controlled gene and central component of the TGFβ canonical pathway, is frequently mutated in pancreatic ductal adenocarcinoma (PDA), leading to decreased survival. Here, we used an in vitro PDA model of SMAD4-positive and SMAD4-negative cells to investigate the interplay between circadian rhythms, the TGFβ canonical signaling pathway, and its impact on tumor malignancy. Our data show that TGFβ1, SMAD3, SMAD4, and SMAD7 oscillate in a circadian fashion in SMAD4-positive PDA cells, whereas altering the clock impairs the mRNA dynamics of these genes. Furthermore, the expression of the clock genes DEC1, DEC2, and CRY1 varied depending on SMAD4 status. TGFβ pathway activation resulted in an altered clock, cell-cycle arrest, accelerated apoptosis rate, enhanced invasiveness, and chemosensitivity. Our data suggest that the impact of TGFβ on the clock is SMAD4-dependent, and S MAD3, SMAD4, DEC1, and CRY1 involved in this cross-talk affect PDA patient survival.

Period Family of Clock Genes as Novel Predictors of Survival in Human Cancer: A Systematic Review and Meta-Analysis

Background

Period genes are important core clock genes, including PER1, PER2, and PER3. A number of studies have demonstrated that the abnormal expression of the PER gene family of clock genes is associated with the survival and prognosis of patients with cancer; however, the sample sizes included in the majority of these studies were small, and the reported results were inconsistent. This study was the first to collect the relevant publications to systematically evaluate the value of the expression of the PER gene family in the prediction of survival and prognosis of human tumors.

Methods

The PubMed, Cochrane Library, Embase, and Web of Science databases were searched systematically, and a meta-analysis was performed.

Results

A total of 12 eligible publications met the inclusion criteria for the meta-analysis, including 1,369 patients and 9 different types of cancer. The pooled hazard ratio for overall survival indicated that the overall survival of patients in the high PER1, PER2, and PER3 protein expression group was significantly higher than that in the low-expression group, respectively. The sensitivity analysis revealed that the result was stable and reliable. The association between PER1 and PER3 mRNA expression levels and cancer prognosis was not meta-analyzed as the number of experimental studies was <3. There was no significant association between the expression of PER2 mRNA and the overall survival of patients with cancer.

Conclusion

PER1, PER2, and PER3 protein expression levels can be used as novel potential biomarkers for predicting cancer prognosis.

Low circadian clock genes expression in cancers: A meta-analysis of its association with clinicopathological features and prognosis

Background

Per1, Per2, Per3, Cry1, Cry2, Bmal1, Npas2 and CLOCK genes are the eight core circadian clock genes. Low expression of these circadian clock genes plays an important role in the progression of cancers. However, its clinicopathological and prognostic value in patients with cancers remains controversial and inconclusive. We performed a meta-analysis of studies assessing the clinicopathological and prognostic significance of low expression of these genes in cancers.

Methods

Relevant studies were searched from the Cochrane Central Register of Controlled Trials, Embase, EBSCO, Ovid, PubMed, Science Direct, Wiley Online Library database, CNKI and Wan Fang database. The meta-analysis was performed by using STATA version 12 software. A random-effect model was employed to evaluate all pooled hazard ratios (HRs) and odd ratios (ORs).

Results

A total of 36 studies comprising 7476 cases met the inclusion criteria. Meta-analysis suggested that low expression of Per1 was associated with poor differentiation (Per1: OR=2.30, 95%CI: 1.36∼3.87, P=0.002) and deeper invasion depth (Per1: OR=2.12, 95%CI: 1.62∼2.77, Ρ<0.001); low Per2 expression was correlated with poor differentiation (Per2: OR=2.41, 95%CI: 1.53∼3.79, Ρ<0.001), worse TNM stage (Per2:OR=3.47, 95%CI: 1.88∼6.42, P<0.001) and further metastasis (Per2:OR=2.35, 95%CI: 1.35∼4.11, Ρ=0.003). Furthermore, the results revealed that low expressions of Per1 and Per2 were also correlated with poor overall survival of cancers (Per1: HR=1.35, 95%CI: 1.06∼1.72, P=0.014; Per2: HR=1.43, 95%CI: 1.10∼1.85, P=0.007). Subgroup analysis indicated that low Per1 and Per2 expressions were especially associated with poor prognosis of gastrointestinal caners (Per1: HR=1.33, 95%CI: 1.14∼1.55, Ρ<0.001, Ι²=4.2%; Per2: HR=1.62, 95%CI: 1.25∼2.18, P<0.001, I²=0.0%).

Conclusions

Our study suggested that low Per1, Per2 and Npas2 expression played a distinct and crucial role in progression of cancers. Low expressions of Per1 and Per2 could serve as unfavorable indicators for cancers prognosis, especially for gastrointestinal cancers.

Circadian Genes as Therapeutic Targets in Pancreatic Cancer

Pancreatic cancer is one of the most lethal cancers worldwide due to its symptoms, early metastasis, and chemoresistance. Thus, the mechanisms contributing to pancreatic cancer progression require further exploration. Circadian rhythms are the daily oscillations of multiple biological processes regulated by an endogenous clock. Several evidences suggest that the circadian clock may play an important role in the cell cycle, cell proliferation and apoptosis. In addition, timing of chemotherapy or radiation treatment can influence the efficacy and toxicity treatment. Here, we revisit the studies on circadian clock as an emerging target for therapy in pancreatic cancer. We highlight those potential circadian genes regulators that are commonly affected in pancreatic cancer according to most recent reports.

Circadian rhythms: a regulator of gastrointestinal health and dysfunction

Circadian rhythms regulate much of gastrointestinal physiology including cell proliferation, motility, digestion, absorption, and electrolyte balance. Disruption of circadian rhythms can have adverse consequences including the promotion of and/or exacerbation of a wide variety of gastrointestinal disorders and diseases. Areas covered: In this review, we evaluate some of the many gastrointestinal functions that are regulated by circadian rhythms and how dysregulation of these functions may contribute to disease. This review also discusses some common gastrointestinal disorders that are known to be influenced by circadian rhythms as well as speculation about the mechanisms by which circadian rhythm disruption promotes dysfunction and disease pathogenesis. We discuss how knowledge of circadian rhythms and the advent of chrono-nutrition, chrono-pharmacology, and chrono-therapeutics might influence clinical practice. Expert opinion: As our knowledge of circadian biology increases, it may be possible to incorporate strategies that take advantage of circadian rhythms and chronotherapy to prevent and/or treat disease.

Current Status of Research on the Period Family of Clock Genes in the Occurrence and Development of Cancer

Several physiological activities of organisms are coordinated based on periodic variations of ~24 h, which is called a circadian rhythm. Circadian rhythms, driven by circadian clock genes, play an important role in the regulation of various complex life activities of organisms, in an orderly and coordinated manner. Period (Per)1/2/3 genes are important core clock genes and part of the Per gene family. Current research has demonstrated that the abnormal expression of Per genes and disruption of circadian rhythms can lead to the occurrence and development of cancer; however, the exact mechanism has not yet been elucidated. Further study on this mechanism may lead to the discovery of new, effective therapies for the prevention and treatment of cancer. The present review summarizes the status of current research with regards to the association between the abnormal expression and rhythmic variation of the Per gene family, and carcinogenesis and progression of cancer.

Oxysterols and Gastrointestinal Cancers Around the Clock

This review focuses on the role of oxidized sterols in three major gastrointestinal cancers (hepatocellular carcinoma, pancreatic, and colon cancer) and how the circadian clock affects the carcinogenesis by regulating the lipid metabolism and beyond. While each field of research (cancer, oxysterols, and circadian clock) is well-studied within their specialty, little is known about the intertwining mechanisms and how these influence the disease etiology in each cancer type. Oxysterols are involved in pathology of these cancers, but final conclusions about their protective or damaging effects are elusive, since the effect depends on the type of oxysterol, concentration, and the cell type. Oxysterol concentrations, the expression of key regulators liver X receptors (LXR), farnesoid X receptor (FXR), and oxysterol-binding proteins (OSBP) family are modulated in tumors and plasma of cancer patients, exposing these proteins and selected oxysterols as new potential biomarkers and drug targets. Evidence about how cholesterol/oxysterol pathways are intertwined with circadian clock is building. Identified key contact points are different forms of retinoic acid receptor related orphan receptors (ROR) and LXRs. RORs and LXRs are both regulated by sterols/oxysterols and the circadian clock and in return also regulate the same pathways, representing a complex interplay between sterol metabolism and the clock. With this in mind, in addition to classical therapies to modulate cholesterol in gastrointestinal cancers, such as the statin therapy, the time is ripe also for therapies where time and duration of the drug application is taken as an important factor for successful therapies. The final goal is the personalized approach with chronotherapy for disease management and treatment in order to increase the positive drug effects.

An Overview of the Polymorphisms of Circadian Genes Associated With Endocrine Cancer

A major consequence of the world industrialized lifestyle is the increasing period of unnatural light in environments during the day and artificial lighting at night. This major change disrupts endogenous homeostasis with external circadian cues, which has been associated to higher risk of diseases affecting human health, mainly cancer among others. Circadian disruption promotes tumor development and accelerate its fast progression. The dysregulation mechanisms of circadian genes is greatly affected by the genetic variability of these genes. To date, several core circadian genes, also called circadian clock genes, have been identified, comprising the following: ARNTL, CLOCK, CRY1, CRY2, CSNK1E, NPAS2, NR1D1, NR1D2, PER1, PER2, PER3, RORA, and TIMELESS. The polymorphic variants of these circadian genes might contribute to an individual's risk to cancer. In this short review, we focused on clock circadian clock-related genes, major contributors of the susceptibility to endocrine-dependent cancers through affecting circadian clock, most likely affecting hormonal regulation. We examined polymorphisms affecting breast, prostate and ovarian carcinogenesis, in addition to pancreatic and thyroid cancer. Further study of the genetic composition in circadian clock-controlled tumors will be of great importance by establishing the foundation to discover novel genetic biomarkers for cancer prevention, prognosis and target therapies.

Association between circadian gene CLOCK and cisplatin resistance in ovarian cancer cells: A preliminary study

The present study aimed to observe the expression of circadian gene clock circadian regulator (CLOCK) in ovarian cancer cells and the effects of circadian gene CLOCK on cis-dichlorodiamine platinum (cisplatin) resistance in ovarian cancer cells. The expression of CLOCK mRNA and protein in cisplatin-sensitive A2780 and cisplatin-resistant CP70 cells were detected by quantitative polymerase chain reaction and western blot assay. Cisplatin-sensitive A2780 and cisplatin-resistant CP70 cells were treated with different concentrations of cisplatin for 48 h, and the expression of hCLOCK protein in the two types of cells was detected by western blot assay. RNA interference method was used to knock down the expression of CLOCK in cisplatin-resistant CP70 cells. Subsequently, the cisplatin-resistant CP70 cells were treated with cisplatin. The proliferation of cisplatin-resistant CP70 cells was observed following treatment with cisplatin. The expression of CLOCK mRNA was significantly higher in cisplatin-resistant CP70 cells (1.58±0.49) compared with cisplatin-sensitive A2780 cells (0.44±0.13) (P<0.01). Western blot assay results demonstrated that the expression of CLOCK protein was significantly greater in the cisplatin-resistant CP70 cells (1.47±0.34) compared with the cisplatin-sensitive A2780 cells (0.48±0.15) (P<0.01). Following the treatment of A2780 and CP70 cells with cisplatin, CLOCK protein expression increased with an increased concentration of cisplatin, in a dose-dependent manner (P<0.01). Following the knockdown of CLOCK in cisplatin-resistant CP70 cells by RNA interference, cisplatin treatment was able to significantly inhibit the proliferation of cells and induce apoptosis (P<0.01). The expression of circadian gene CLOCK in ovarian cancer cells was strongly associated with cisplatin resistance. The upregulation of circadian gene CLOCK in ovarian cancer cells may reduce its sensitivity to cisplatin treatment.

The MiR-135b-BMAL1-YY1 loop disturbs pancreatic clockwork to promote tumourigenesis and chemoresistance

Circadian disruption has been implicated in tumour development, but the underlying mechanism remains unclear. Here, we show that the molecular clockwork within malignant human pancreatic epithelium is disrupted and that this disruption is mediated by miR-135b-induced BMAL1 repression. miR-135b directly targets the BMAL1 3'-UTR and thereby disturbs the pancreatic oscillator, and the downregulation of miR-135b is essential for the realignment of the cellular clock. Asynchrony between miR-135b and BMAL1 expression impairs the local circadian gating control of tumour suppression and significantly promotes tumourigenesis and resistance to gemcitabine in pancreatic cancer (PC) cells, as demonstrated by bioinformatics analyses of public PC data sets and in vitro and in vivo functional studies. Moreover, we found that YY1 transcriptionally activated miR-135b and formed a 'miR-135b-BMAL1-YY1' loop, which holds significant predictive and prognostic value for patients with PC. Thus, our work has identified a novel signalling loop that mediates pancreatic clock disruption as an important mechanism of PC progression and chemoresistance.

Maternal obesity alters endoplasmic reticulum homeostasis in offspring pancreas

The prevalence of non-alcoholic fatty pancreas disease (NAFPD) is increasing in parallel with obesity rates. Stress-related alterations in endoplasmic reticulum (ER), such as the unfolded protein response (UPR), are associated with obesity. The aim of this study was to investigate ER imbalance in the pancreas of a mice model of adult and perinatal diet-induced obesity. Twenty female C57BL/6J mice were assigned to control (Con) or obesogenic (Ob) diets prior to and during pregnancy and lactation. Their offspring were weaned onto Con or Ob diets up to 6 months post-partum. Then, after sacrifice, plasma biochemical analyses, gene expression, and protein concentrations were measured in pancreata. Offspring of Ob-fed mice had significantly increased body weight (p < 0.001) and plasma leptin (p < 0.001) and decreased insulin (p < 0.01) levels. Maternal obesogenic diet decreased the total and phosphorylated Eif2α and increased spliced X-box binding protein 1 (XBP1). Pancreatic gene expression of downstream regulators of UPR (EDEM, homocysteine-responsive endoplasmic reticulum-resident (HERP), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP)) and autophagy-related proteins (LC3BI/LC3BII) were differently disrupted by obesogenic feeding in both mothers and offspring (from p < 0.1 to p < 0.001). Maternal obesity and Ob feeding in their offspring alter UPR in NAFPD, with involvement of proapoptotic and autophagy-related markers. Upstream and downstream regulators of PERK, IRE1α, and ATF6 pathways were affected differently following the obesogenic insults.

Decreased circadian component Bmal1 predicts tumor progression and poor prognosis in human pancreatic ductal adenocarcinoma

The circadian clock has been demonstrated playing important roles in human tumorigenic process; however, the detailed clinical implications of circadian disruption on tumors have not been well understood. In this study, we investigated the expression pattern of Bmal1, the core component of the circadian system, in human pancreatic ductal adenocarcinoma (PDA). Our immunohistochemistry analysis showed that the protein level of Bmal1 was significantly decreased in tumor tissues from 87 patients with PDA compared with adjacent non-cancerous tissues. Low Bmal1 expression was associated with the TNM/clinical stage, histological differentiation, and vascular invasion of PDA; but no significant relevance to patient age, gender, the tumor location, or the size. Furthermore, Kaplan-Meier survival analysis revealed that PDA patients with low Bmal1 expression had shorter overall survival (OS) times as well as disease-free times (DFS) compared to the patients with high Bmal1 expression. Lastly, univariate and multivariate analyses identified low Bmal1 expression as an independent prognostic factor for poor survival outcome for patients with PDA. Collectively, our present study demonstrated that the decreased expression of Bmal1 is correlated with the tumor progression and poor prognosis in human PDA, which implicated its potential to be used as a biomarker for diagnosis and prognosis of PDA.

The circadian clock gene Bmal1 acts as a potential anti-oncogene in pancreatic cancer by activating the p53 tumor suppressor pathway

Disruption of the circadian clock has been shown to be associated with tumor development. This study aimed to investigate the role of the core circadian gene Bmal1 in pancreatic cancer (PC). We first found that the levels of Bmal1 were downregulated in PC samples and were closely correlated with the clinicopathological features of patients. To dissect the underlying mechanism, we performed a RNA-seq assay followed by systematic gene function and pathway enrichment analyses. We detected an anti-apoptotic and pro-proliferative transcriptome profile after Bmal1 knockdown in PC cells. Further in vitro and in vivo studies confirmed that Bmal1 overexpression significantly inhibited cell proliferation and invasion and induced G2/M cell cycle arrest, whereas Bmal1 knockdown promoted PC growth, as demonstrated in Bmal1-manipulated AsPC-1 and BxPC-3 cell lines. Our mechanistic studies indicated that Bmal1 could directly bind to the p53 gene promoter and thereby transcriptionally activate the downstream tumor suppressor pathway in a p53-dependent manner. In sum, our findings suggest that Bmal1 acts as an anti-oncogene in PC and represents a potential biomarker for its diagnosis.

Sirtuin-dependent clock control: new advances in metabolism, aging and cancer

PURPOSE OF REVIEW

The circadian clock is an intricate biological timekeeper that is subject to fine-tuning mechanisms in order to maintain synchrony with the surrounding environment. One such mechanism is performed by the mammalian sirtuins that provide plasticity to the circadian clock by sensing cellular metabolic state. The sirtuins modulate the circadian epigenome and subsequent transcriptional control, and alterations to this organized system manifest in metabolic consequences, aging phenotypes and possibly cancer.

RECENT FINDINGS

New information regarding sirtuin-dependent control of the circadian clock has emerged. In addition to sirtuin (SIRT)1 and SIRT3, SIRT6 has been demonstrated as a critical regulator of circadian transcription that also serves as an interface with metabolic homeostasis. Also, new metabolic functions of SIRT1 have been described in the brain, which are critical to relay nutritional inputs to the central clock.

SUMMARY

This review focuses on the link between the circadian clock and the sirtuins, with an emphasis on new findings. In addition, speculation on the possible connections at the physiological level will be made that could further link the clock to aging and cancer.