Circadian variations of rectal cell proliferation in patients affected by advanced colorectal cancer

Identification of potential circadian genes and associated pathways in colorectal cancer progression and prognosis using microarray gene expression analysis

Colorectal cancer (CRC) is third cancer causing death in the world. CRC is associated with disrupting the circadian rhythm (CR), closely associating the CRC progression and the dysregulation of genes involved in the biological clock. In this study, we aimed to understand the circadian rhythm changes in patients diagnosed with CRC. We used the GEO database with the ID GSE46549 for our analysis, which consists of 32 patients with CRC and one as normal control. Our study has identified five essential genes involved in CRC, HAPLN1, CDH12, IGFBP5, DCHS2, and DOK5, and had different enriched pathways, such as the Wnt-signaling pathway, at different time points of study. As a part of our study, we also identified various related circadian genes, such as CXCL12, C1QTNF2, MRC2, and GLUL, from the Circadian Gene Expression database, that played a role in circadian rhythm and CRC development. As circadian timing can influence the host tissue's ability to tolerate anticancer medications, the genes reported can serve as a potential drug target for treating CRC and become beneficial to translational settings.

Understanding the significance of biological clock and its impact on cancer incidence

The circadian clock is an essential timekeeper that controls, for humans, the daily rhythm of biochemical, physiological, and behavioral functions. Irregular performance or disruption in circadian rhythms results in various diseases, including cancer. As a factor in cancer development, perturbations in circadian rhythms can affect circadian homeostasis in energy balance, lead to alterations in the cell cycle, and cause dysregulation of chromatin remodeling. However, knowledge gaps remain in our understanding of the relationship between the circadian clock and cancer. Therefore, a mechanistic understanding by which circadian disruption enhances cancer risk is needed. This review article outlines the importance of the circadian clock in tumorigenesis and summarizes underlying mechanisms in the clock and its carcinogenic mechanisms, highlighting advances in chronotherapy for cancer treatment.

Bioinformatical identification of key genes regulated by IGF2BP2-mediated RNA N6-methyladenosine and prediction of prognosis in hepatocellular carcinoma

Background

The treatment of hepatocellular carcinoma (HCC), a malignant cancer with global spread, remains unsatisfactory, and novel prognostic biomarkers need to be identified. N6-methyladenosine (m⁶A) has been found to regulate tumor initiation and progression through different mechanisms. As a dynamic and reversible messenger RNA (mRNA) modification, m⁶A can be read by insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2). IGF2BP2 targets thousands of mRNA transcripts, which may be involved in HCC progression.

Methods

In this study, we integrated 4 classes of datasets including The Cancer Genome Atlas (TCGA)-LICH, m⁶A-sequencing data of HepG2 cells, and RNA-sequencing data of IGF2BP2-knockdown HepG2 cells to explore the key genes regulated by IGF2BP2-mediated m⁶A in HCC. The expression and m⁶A modification of candidates were validation in independent microarray expression profile of HCC tissue and annotated m⁶A database RMBase. The relationship of immune cell infiltration and the genes expression was estimated by CIBERSORT and TIMER.

Results

A total of 89 candidate genes were filtered. Next, cluster analysis was performed base on functions and pathways to identify the enrichment pathways. By constructing a protein-protein interaction (PPI) network, we found 54 nodes. Ten significant genes were filtered from the PPI. These genes were validated in data of an independent microarray and an m⁶A database. We found that the upregulation of these 10 genes was associated with poor prognosis. In addition, we showed the expression of these 10 genes was associated with the infiltration of variety of immune cell and tumor purity.

Conclusions

These identified genes may provide novel insights and facilitate the development of potential biomarkers for HCC diagnosis, as well as provide clues for IGF2BP2 inhibition therapy in HCC.

Exploring the role of circadian clock gene and association with cancer pathophysiology

Most of the processes that occur in the mind and body follow natural rhythms. Those with a cycle length of about one day are called circadian rhythms. These rhythms are driven by a system of self-sustained clocks and are entrained by environmental cues such as light-dark cycles as well as food intake. In mammals, the circadian clock system is hierarchically organized such that the master clock in the suprachiasmatic nuclei of the hypothalamus integrates environmental information and synchronizes the phase of oscillators in peripheral tissues.The circadian system is responsible for regulating a variety of physiological and behavioral processes, including feeding behavior and energy metabolism. Studies revealed that the circadian clock system consists primarily of a set of clock genes. Several genes control the biological clock, including BMAL1, CLOCK (positive regulators), CRY1, CRY2, PER1, PER2, and PER3 (negative regulators) as indicators of the peripheral clock.Circadian has increasingly become an important area of medical research, with hundreds of studies pointing to the body's internal clocks as a factor in both health and disease. Thousands of biochemical processes from sleep and wakefulness to DNA repair are scheduled and dictated by these internal clocks. Cancer is an example of health problems where chronotherapy can be used to improve outcomes and deliver a higher quality of care to patients.In this article, we will discuss knowledge about molecular mechanisms of the circadian clock and the role of clocks in physiology and pathophysiology of concerns.

Cross-talk between the circadian clock and the cell cycle in cancer

The circadian clock is an endogenous timekeeper system that controls the daily rhythms of a variety of physiological processes. Accumulating evidence indicates that genetic changes or unhealthy lifestyle can lead to a disruption of circadian homeostasis, which is a risk factor for severe dysfunctions and pathologies including cancer. Cell cycle, proliferation, and cell death are closely intertwined with the circadian clock, and thus disruption of circadian rhythms appears to be linked to cancer development and progression. At the molecular level, the cell cycle machinery and the circadian clocks are controlled by similar mechanisms, including feedback loops of genes and protein products that display periodic activation and repression. Here, we review the circadian rhythmicity of genes associated with the cell cycle, proliferation, and apoptosis, and we highlight the potential connection between these processes, the circadian clock, and neoplastic transformations. Understanding these interconnections might have potential implications for the prevention and therapy of malignant diseases.

Circadian clock circuitry in colorectal cancer

Colorectal cancer is the most prevalent among digestive system cancers. Carcinogenesis relies on disrupted control of cellular processes, such as metabolism, proliferation, DNA damage recognition and repair, and apoptosis. Cell, tissue, organ and body physiology is characterized by periodic fluctuations driven by biological clocks operating through the clock gene machinery. Dysfunction of molecular clockworks and cellular oscillators is involved in tumorigenesis, and altered expression of clock genes has been found in cancer patients. Epidemiological studies have shown that circadian disruption, that is, alteration of bodily temporal organization, is a cancer risk factor, and an increased incidence of colorectal neoplastic disease is reported in shift workers. In this review we describe the involvement of the circadian clock circuitry in colorectal carcinogenesis and the therapeutic strategies addressing temporal deregulation in colorectal cancer.

The circadian clock in cancer development and therapy

Most aspects of mammalian function display circadian rhythms driven by an endogenous clock. The circadian clock is operated by genes and comprises a central clock in the brain that responds to environmental cues and controls subordinate clocks in peripheral tissues via circadian output pathways. The central and peripheral clocks coordinately generate rhythmic gene expression in a tissue-specific manner in vivo to couple diverse physiological and behavioral processes to periodic changes in the environment. However, with the industrialization of the world, activities that disrupt endogenous homeostasis with external circadian cues have increased. This change in lifestyle has been linked to an increased risk of diseases in all aspects of human health, including cancer. Studies in humans and animal models have revealed that cancer development in vivo is closely associated with the loss of circadian homeostasis in energy balance, immune function, and aging, which are supported by cellular functions important for tumor suppression including cell proliferation, senescence, metabolism, and DNA damage response. The clock controls these cellular functions both locally in cells of peripheral tissues and at the organismal level via extracellular signaling. Thus, the hierarchical mammalian circadian clock provides a unique system to study carcinogenesis as a deregulated physiological process in vivo. The asynchrony between host and malignant tissues in cell proliferation and metabolism also provides new and exciting options for novel anticancer therapies.

Circadian rhythm disruption in cancer biology

Circadian rhythms show universally a 24-h oscillation pattern in metabolic, physiological and behavioral functions of almost all species. This pattern is due to a fundamental adaptation to the rotation of Earth around its own axis. Molecular mechanisms of generation of circadian rhythms organize a biochemical network in suprachiasmatic nucleus and peripheral tissues, building cell autonomous clock pacemakers. Rhythmicity is observed in transcriptional expression of a wide range of clock-controlled genes that regulate a variety of normal cell functions, such as cell division and proliferation. Desynchrony of this rhythmicity seems to be implicated in several pathologic conditions, including tumorigenesis and progression of cancer. In 2007, the International Agency for Research on Cancer (IARC) categorized "shiftwork that involves circadian disruption [as] probably carcinogenic to humans" (Group 2A in the IARC classification system of carcinogenic potency of an agentagent) (Painting, Firefighting, and Shiftwork; IARC; 2007). This review discusses the potential relation between disruptions of normal circadian rhythms with genetic driving machinery of cancer. Elucidation of the role of clockwork disruption, such as exposure to light at night and sleep disruption, in cancer biology could be important in developing new targeted anticancer therapies, optimizing individualized chronotherapy and modifying lighting environment in workplaces or homes.

Beta-catenin induces beta-TrCP-mediated PER2 degradation altering circadian clock gene expression in intestinal mucosa of ApcMin/+ mice

Proliferation of intestinal epithelial cells is rhythmic throughout the day. This temporal organization occurs through the interaction between the endogenous peripheral circadian clock and pathways controlling cell cycle progression. Per2, a core clock gene with tumour suppresser function, is critical to clock function and to the regulation of cellular proliferation. Circadian disruption, which increases colon cancer incidence, may do so by deregulating clock controlled epithelial cell proliferation. Increased expression of beta-catenin is a contributing cause of most familial and spontaneous human colon cancer and the cause of multiple intestinal neoplasia of the Apc(Min/+) mouse. Here we report that increased beta-catenin destabilizes PER2 clock protein by inducing beta-TrCP, an F-box protein of SCF ubiquitin E3 ligase. In the intestinal mucosa of the Apc(Min/)(+) mouse, the decrease in PER2 protein levels is associated with altered circadian rhythms of clock genes, Per1 and Per2, and clock controlled genes, Dbp and Wee1. These findings suggest that disruption of the peripheral intestinal circadian clock may be intimately involved in beta-catenin induced intestinal epithelial neoplastic transformation in both mouse and man.

Intérêt de la chronothérapie dans le traitement pluridisciplinaire des cancers de l'œsophage et de l'estomac

The authors evaluated the impact of a chronotherapy with 5-FU, folinic acid and carboplatine (chronomodulated infusions by ambulatory pumps; 5/21 days) for the management of oesophagus (52 cases) and gastric (56 cases) cancer patients. The overall tolerance of treatment was gauged excellent (grade 3-4; % patients: mucitis: 11-23%; leucopenia 6-19%; thrombopenia 18-50%; almost no digestive disturbances nor alopecia). Also tumor outcome was considered interesting with major responses rate in 61% (gastric) to 79% (oesophagus) of patients. The median survival of oesophageal cancer was limited to 9.2 months; the one of disseminated gastric cancer was 12.7 months but 72% of curatively resected patients were alive at 5+ years.

Circadian variation in expression of G1 phase cyclins D1 and E and cyclin-dependent kinase inhibitors p16 and p21 in human bowel mucosa

AIM: To evaluate whether the cellular proliferation rate in the large bowel epithelial cells is characterized by circadian rhythm.

METHODS: Between January 2003 and December 2004, twenty patients who were diagnosed as suffering from primary, resectable, non-metastatic adenocarcinoma of the lower rectum, infiltrating the sphincter mechanism, underwent abdominoperineal resection, total mesorectal excision and permanent left iliac colostomy. In formalin-fixed and paraffin-embedded biopsy specimens obtained from the colostomy mucosa every six hours (00:00, 06:00, 12:00, 18:00 and 24:00), we studied the expression of G₁ phase cyclins (D₁ and E) as well as the expression of the G₁ phase cyclin-dependent kinase (CDK) inhibitors p16 and p21 as indicators of cell cycle progression in colonic epithelial cells using immunohistochemical methods.

RESULTS: The expression of both cyclins showed a similar circadian fashion obtaining their lowest and highest values at 00:00 and 18:00, respectively (P< 0.001). A circadian rhythm in the expression of CDK inhibitor proteins p16 and p21 was also observed, with the lowest levels obtained at 12:00 and 18:00 (P< 0.001), respectively. When the complexes cyclins D₁ - p21 and E - p21 were examined, the expression of the cyclins was adversely correlated to the p21 expression throughout the day. When the complexes the cyclins D₁ - p16 and E - p16 were examined, high levels of p16 expression were correlated to low levels of cyclin expression at 00:00, 06:00 and 24:00. Meanwhile, the highest expression levels of both cyclins were correlated to high levels of p16 expression at 18:00.

CONCLUSION: Colonic epithelial cells seem to enter the G₁ phase of the cell cycle during afternoon (between 12:00 and 18:00) with the highest rates obtained at 18:00. From a clinical point of view, the present results suggest that G₁-phase specific anticancer therapies in afternoon might maximize their anti-tumor effect while minimizing toxicity.

Daily timed meals dissociate circadian rhythms in hepatoma and healthy host liver

Dividing cells, including human cancers, organize processes necessary for their duplication according to circadian time. Recent evidence has shown that disruption of central regulation of circadian rhythms can increase the rate at which a variety of cancers develop in rodents. To study circadian rhythms in liver tumors, we have chemically induced hepatocellular carcinoma in transgenic rats bearing a luciferase reporter gene attached to the promoter of a core circadian clock gene (Period 1). We explanted normal liver cells and hepatomas, placed them into short-term culture, and precisely measured their molecular clock function by recording light output. Results show that isolated hepatocellular carcinoma is capable of generating circadian rhythms in vitro. Temporally restricting food availability to either day or night altered the phase of the rhythms in both healthy and malignant tissue. However, the hepatomas were much less sensitive to this signal resulting in markedly different phase relationships between host and tumor tissue as a function of mealtime. These data support the conclusion that hepatoma is differentially sensitive to circadian timing signals, although it maintains the circadian organization of the nonmalignant cells from which it arose. Because circadian clocks are known to modulate the sensitivity of many therapeutic cytotoxic targets, controlling meal-timing might be used to increase the efficacy of treatment. Specifically, meal and treatment schedules could be designed that take advantage of coincident times of greatest tumor sensitivity and lowest sensitivity of host tissue to damage.

Differential role of vagus nerve in maintaining diurnal gene expression rhythms in the proximal small intestine

BACKGROUND

We have documented previously diurnal rhythms in intestinal sugar transporter expression. We set out to identify the role of the vagus nerve in these rhythms.

MATERIALS AND METHODS

Sprague-Dawley rats underwent truncal vagotomy (V; n = 9) and were pair-fed with sham-operated (n = 4) and unoperated rats (n = 6). Rats were killed at ZT3 and ZT9 (ZT: Zeitgeber time with ZT0 set at lights-on), the time interval over which sucrase, SGLT1, GLUT2, and GLUT5 expression exhibit significant anticipatory increases. Jejunal RNA expression for the four genes were assessed by Northern blot analysis. SGLT1 and GLUT2 expression was further studied by Western blot analysis and in situ hybridization.

RESULTS

Control rats (sham-operated plus unoperated rats) exhibited the expected increase in RNA levels at ZT9 versus ZT3 for SGLT1, GLUT2, GLUT5, and sucrase (P < 0.01 for each). The diurnal rhythm of mRNA levels for GLUT2 and sucrase, but not for SGLT1 or GLUT5, were blunted in V rats. At protein level, SGLT1 was induced 4.3-fold in control rats (P < 0.01) and 3.8-fold in V rats (P < 0.01), whereas GLUT2 was induced 3.3-fold in control rats (P < 0.01) but only 1.4-fold in V rats (N.S.).

CONCLUSIONS

Our results indicate that signaling through the vagus nerve is necessary for the anticipatory induction of GLUT2 and sucrase. Persistence of normal rhythms in both SGLT1 and GLUT5 indicates that diurnal induction of these genes is independent of vagal innervation. Entrainment of anticipatory diurnal gene expression in the intestine occurs via two separate pathways that are differentially dependent on vagal input.