Stromal Expression of the Core Clock Gene Period 2 Is Essential for Tumor Initiation and Metastatic Colonization

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.

Circadian rhythm regulation in the immune system

Circadian rhythms are a ubiquitous feature in nearly all living organisms, representing oscillatory patterns with a 24-h cycle that are widespread across various physiological processes. Circadian rhythms regulate a multitude of physiological systems, including the immune system. At the molecular level, most immune cells autonomously express clock-regulating genes, which play critical roles in regulating immune cell functions. These functions encompass migration, phagocytic activity, immune cell metabolism (such as mitochondrial structural function and metabolism), signalling pathway activation, inflammatory responses, innate immune recognition, and adaptive immune processes (including vaccine responses and pathogen clearance). The endogenous circadian clock orchestrates multifaceted rhythmicity within the immune system, optimizing immune surveillance and responsiveness; this bears significant implications for maintaining immune homeostasis and resilience against diseases. This work provides an overview of circadian rhythm regulation within the immune system.

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.

Forces at play: exploring factors affecting the cancer metastasis

Metastatic disease, a leading and lethal indication of deaths associated with tumors, results from the dissemination of metastatic tumor cells from the site of primary origin to a distant organ. Dispersion of metastatic cells during the development of tumors at distant organs leads to failure to comply with conventional treatments, ultimately instigating abrupt tissue homeostasis and organ failure. Increasing evidence indicates that the tumor microenvironment (TME) is a crucial factor in cancer progression and the process of metastatic tumor development at secondary sites. TME comprises several factors contributing to the initiation and progression of the metastatic cascade. Among these, various cell types in TME, such as mesenchymal stem cells (MSCs), lymphatic endothelial cells (LECs), cancer-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), T cells, and tumor-associated macrophages (TAMs), are significant players participating in cancer metastasis. Besides, various other factors, such as extracellular matrix (ECM), gut microbiota, circadian rhythm, and hypoxia, also shape the TME and impact the metastatic cascade. A thorough understanding of the functions of TME components in tumor progression and metastasis is necessary to discover new therapeutic strategies targeting the metastatic tumor cells and TME. Therefore, we reviewed these pivotal TME components and highlighted the background knowledge on how these cell types and disrupted components of TME influence the metastatic cascade and establish the premetastatic niche. This review will help researchers identify these altered components' molecular patterns and design an optimized, targeted therapy to treat solid tumors and restrict metastatic cascade.

A new time dimension in the fight against metastasis

Despite advances in uncovering vulnerabilities, identifying biomarkers, and developing more efficient treatments, cancer remains a threat because of its ability to progress while acquiring resistance to therapy. The circadian rhythm governs most of the cellular functions implicated in cancer progression, and its exploitation therefore opens new promising directions in the fight against metastasis. In this review we summarize the role of the circadian rhythm in tumor development and progression, with emphasis on the circadian rhythm-regulated elements that control the generation of circulating tumor cells (CTCs) and metastasis. We then present data on chronotherapy and discuss how circadian rhythm investigations may open new paths to more effective anticancer treatments.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

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.

Activated fibroblasts in cancer: Perspectives and challenges

Activated fibroblasts in tumors, or cancer-associated fibroblasts (CAFs), have become a popular research area over the past decade. As important players in many aspects of tumor biology, with functions ranging from collagen deposition to immunosuppression, CAFs have been the target of clinical and pre-clinical studies that have revealed their potential pro- and anti-tumorigenic dichotomy. In this review, we describe the important role of CAFs in the tumor microenvironment and the technological advances that made these discoveries possible, and we detail the models that are currently available for CAF investigation. Additionally, we present evidence to support the value of encompassing CAF investigation as a future therapeutic avenue alongside immune and cancer cells while highlighting the challenges that must be addressed for successful clinical translation of new findings.

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.

Impacts of Circadian Gene Period2 Knockout on Intestinal Metabolism and Hepatic Antioxidant and Inflammation State in Mice

The period circadian regulator 2 (Per2) gene is important for the modulations of rhythmic homeostasis in the gut and liver; disruption will cause metabolic diseases, such as obesity, diabetes, and fatty liver. Herein, we investigated the alterations in intestinal metabolic and hepatic functions in Per2 knockout (Per2^−/−, KO) and wild-type (Per2^+/+, WT) mice. Growth indices, intestinal metabolomics, hepatic circadian rhythms, lipid metabolism, inflammation-related genes, antioxidant capacity, and transcriptome sequencing were performed after euthanasia. Data indicated that KO decreased the intestinal concentrations of amino acids such as γ-aminobutyric acid, aspartic acid, glycine, L-allothreonine, methionine, proline, serine, and valine while it increased the concentrations of carbohydrates such as cellobiose, D-talose, fucose, lyxose, and xylose compared with WT. Moreover, the imbalance of intestinal metabolism further seemed to induce liver dysfunction. Data indicated that Per2 knockout altered the expression of hepatic circadian rhythm genes, such as Clock, Bmal1, Per1, Per3, Cry1, and Cry2. KO also induced hepatic lipid metabolism, because of the increase of liver index and serum concentrations of low-density lipoprotein, and the upregulated expression of Pparα, Cyp7a1, and Cpt1. In addition, KO improved hepatic antioxidant capacity due to the increase activities of SOD and GSH-Px and the decrease in concentrations of MDA. Lastly, KO increased the relative expression levels of hepatic inflammation-related genes, such as Il-1β, Il-6, Tnf-α, Myd88, and Nf-κB p65, which may potentially lead to hepatic inflammation. Overall, Per2 knockout induces gut metabolic dysregulation and may potentially trigger alterations in hepatic antioxidant and inflammation responses.

Period 2 Suppresses the Malignant Cellular Behaviors of Colorectal Cancer Through the Epithelial-Mesenchymal Transformation Process

Introduction

The PER2 (Period circadian regulator 2) gene is related to the circadian clock, and it has been deemed as a suppressor gene in osteosarcoma and lung carcinoma. However, the part of PER2 in CRC (colorectal cancer) needs to be further determined.

Methods

First, we collected clinical samples to detect PER2 expression in CRC. Then, we used cell transfection to knock down PER2 expression in CRC cell lines and performed a series of functional experiments to elucidate the effects of PER2 on CRC cells. We next verified whether PER2 affects the epithelial-mesenchymal transformation (EMT) process in CRC by conducting quantitative real-time PCR and western blotting.

Results

In the research, we revealed that the expression of PER2 decreased in CRC clinical samples. In addition, knocking down PER2 expression caused CRC cells to acquire malignant biological features. Finally, we found that PER2 knockdown may activate the Snail/Slug axis through inhibiting p53, therefore promote the activation of the EMT pathway.

Conclusion

In conclusion, low PER2 expression reinforces migration and activates EMT in CRC, suggesting that PER2 is closely related to CRC development and could be used as a potential treatment site in the clinic.

The Circadian Clock and Cancer: Links between Circadian Disruption and Disease Pathology

There is growing evidence that disruption of our 24-hour clock increases our risk for acquiring several diseases and disorders. One of these diseases is cancer. While the mechanistic links between circadian clock disruption and cancer initiation or progression are an active area of study, significantly more work needs to be done to understand the molecular substrates involved. Of particular complexity remains the functions of the clock in individual cells during the process of transformation (cancer initiation) vs. the functions of the clock in tumor-surrounding stroma in the process of tumor progression or metastasis. Indeed, the nexus of cellular circadian dynamics, metabolism, and carcinogenesis is drawing more attention, and many new studies are now highlighting the critical role of circadian rhythms and clock proteins in cancer prevention. In this brief review, we cover some of the basic mechanisms reported to link circadian disruption and cancer at the level of gene expression and metabolism. We also review some of the human studies addressing circadian disruption and cancer incidence as well as some controlled laboratory studies connecting the two in pre-clinical models. Finally, we discuss the tremendous opportunity to use circadian approaches for future prevention and treatment in the context of cancer in specific organs.

Development and performance evaluation of TaqMan real-time fluorescence quantitative methylation specific PCR for detecting methylation level of PER2

BACKGROUND

PER2 gene methylation is closely related to the occurrence and progress of some cancers, but there is no method to quantitatively detect PER2 methylation in conventional laboratories. So, we established a TaqMan real-time fluorescence quantitative methylation specific PCR (TaqMan real-time FQ-MSP) assay and use it for quantitative detection of PER2 methylation in leukemia patients.

METHODS

According to the PER2 sequence searched by GenBank, a CpG sequence enrichment region of the PER2 gene promoter was selected, and the methylated and unmethylated target sequences were designed according to the law of bisulfite conversion of DNA to construct PER2 methylation positive and negative reference materials. Specific primers and probe were designed. The reference materials were continuously diluted into gradient samples by tenfold ratio to evaluate the analytical sensitivity, specificity, accuracy and reproducibility of the method, and the analytical sensitivity of TaqMan real-time FQ-MSP assay was compared with that of the conventional MSP assay. At the same time, the new-established TaqMan real-time FQ-MSP assay and the conventional MSP assay were used to detect the PER2 methylation level of 81 patients with leukemia, and the samples with inconsistent detection results of the two assays were sent to pyromethylation sequencing to evaluate the clinical detection performance.

RESULTS

The minimum detection limit of TaqMan real-time FQ-MSP assay for detecting PER2 methylation level established in this study was 6 copies/uL, and the coefficient of variation(CV) of intra-assay and inter-assay was less than 3%. Compared with the conventional MSP assay, it has higher analytical sensitivity. For the samples with inconsistent detection results, the results of pyrosequencing and TaqMan real-time FQ-MSP assay are consistent.

CONCLUSION

TaqMan real-time FQ-MSP assay of PER2 methylation established in this study has high detection performance and can be used for the detection of clinical samples.

Circadian regulation of cancer cell and tumor microenvironment crosstalk

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

PER2: a potential molecular marker for hematological malignancies

Circadian rhythm is a periodic change of organism according to the law of external environment, which is manifested in metabolism, cell proliferation, physiology and behavior. In recent years, the role of circadian genes in the occurrence and progression of hematological malignancies have been continuously demonstrated. PER2 is the core component of the circadian rhythm playing an important role in regulating the circadian rhythm of the biological clock. This review summarizes the research progress of PER2 in hematological malignancies, especially leukemia, in order to better understand its role in hematological malignancies, and provide new ideas for clinical diagnosis and treatment.

Current Trends and Research Topics Regarding Intestinal Organoids: An Overview Based on Bibliometrics

Currently, research on intestinal diseases is mainly based on animal models and cell lines in monolayers. However, these models have drawbacks that limit scientific advances in this field. Three-dimensional (3D) culture systems named organoids are emerging as a reliable research tool for recapitulating the human intestinal epithelium and represent a unique platform for patient-specific drug testing. Intestinal organoids (IOs) are crypt–villus structures that can be derived from adult intestinal stem cells (ISCs), embryonic stem cells (ESCs), or induced pluripotent stem cells (iPSCs) and have the potential to serve as a platform for individualized medicine and research. However, this emerging field has not been bibliometric summarized to date. Here, we performed a bibliometric analysis of the Web of Science Core Collection (WoSCC) database to evaluate 5,379 publications concerning the use of organoids; the studies were divided into four clusters associated with the current situation and future directions for the application of IOs. Based on the results of our bibliometric analysis of IO applications, we systematically summarized the latest advances and analyzed the limitations and prospects.

Circadian Rhythm Gene PER3 Negatively Regulates Stemness of Prostate Cancer Stem Cells via WNT/β-Catenin Signaling in Tumor Microenvironment

Prostate cancer (PCa) cells are heterogeneous, containing a variety of cancer cells with phenotypical and functional discrepancies in the tumor microenvironment, where prostate cancer stem cells (PCSCs) play a vital role in PCa development. Our earlier studies have shown that ALDH^hiCD44⁺ (DP) PCa cells and the corresponding ALDH^loCD44^– (DN) PCa cells manifest as PCSCs and non-PCSCs, respectively, but the underlying mechanisms regulating stemness of the PCSCs are not completely understood. To tackle this issue, we have performed RNA-Sequencing and bioinformatic analysis in DP (versus DN) cells in this study. We discovered that, PER3 (period circadian regulator 3), a circadian rhythm gene, is significantly downregulated in DP cells. Overexpression of PER3 in DP cells significantly suppressed their sphere- and colony-forming abilities as well as tumorigenicity in immunodeficient hosts. In contrast, knockdown of PER3 in DN cells dramatically promoted their colony-forming and tumor-initiating capacities. Clinically, PER3 is downregulated in human prostate cancer specimens and PER3 expression levels are highly correlated with the prognosis of the PCa patient. Mechanistically, we observed that low levels of PER3 stimulates the expression of BMAL1, leading to the phosphorylation of β-catenin and the activation of the WNT/β-catenin pathway. Together, our results indicate that PER3 negatively regulates stemness of PCSCs via WNT/β-catenin signaling in the tumor microenvironment, providing a novel strategy to treat PCa patients.