N-Terminal Domain Mediated Regulation of RORα1 Inhibits Invasive Growth in Prostate Cancer

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

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

Advances in SEMA3F regulation of clinically high-incidence cancers

Cancer has become a leading cause of morbidity and mortality in recent years. Its high prevalence has had a severe impact on society. Researchers have achieved fruitful results in the causative factors, pathogenesis, treatment strategies, and cancer prevention. Semaphorin 3F (SEMA3F), a member of the signaling family, was initially reported in the literature to inhibit the growth, invasion, and metastasis of cancer cells in lung cancer. Later studies showed it has cancer-inhibiting effects in malignant tumors such as breast, colorectal, ovarian, oral squamous cell carcinoma, melanoma, and head and neck squamous carcinoma. In contrast, recent studies have reported that SEMA3F is expressed more in hepatocellular carcinoma than in normal tissue and promotes metastasis of hepatocellular carcinoma. We chose lung, breast, colorectal, and hepatocellular carcinomas with high clinical prevalence to review the roles and molecular mechanisms of SEMA3F in these four carcinomas. We concluded with an outlook on clinical interventions for patients targeting SEMA3F.

ROS inhibits RORα degradation by decreasing its arginine methylation in liver cancer

Retinoic acid receptor-related orphan receptor α (RORα) is a transcription factor involved in nuclear gene expression and a known tumor suppressor. RORα was the first identified substrate of lysine methylation-dependent degradation. However, the mechanisms of other post-translational modifications (PTMs) that occur in RORα remain largely unknown, especially in liver cancer. Arginine methylation is a common PTM in arginine residues of nonhistone and histone proteins and affects substrate protein function and fate. We found an analogous amino acid disposition containing R37 at the ROR N-terminus compared to histone H3 residue, which is arginine methylated. Here, we provide evidence that R37 methylation-dependent degradation is carried out by protein arginine methyltransferase 5 (PRMT5). Further, we discovered that PRMT5 regulated the interaction between the E3 ubiquitin ligase ITCH and RORα through RORα arginine methylation. Arginine methylation-dependent ubiquitination-mediated RORα degradation reduced downstream target gene activation. H₂ O₂ -induced reactive oxygen species (ROS) decreased PRMT5 protein levels, consequently increasing RORα protein levels in HepG2 liver cancer cells. In addition, ROS inhibited liver cancer progression by inducing apoptosis via PRMT5-mediated RORα methylation and the ITCH axis. Our results potentiate PRMT5 as an elimination target in cancer therapy, and this additional regulatory level within ROS signaling may help identify new targets for therapeutic intervention in liver cancer.

Maresin-1 and Its Receptors RORα/LGR6 as Potential Therapeutic Target for Respiratory Diseases

Maresin-1 is one of the representative specialized pro-resolving mediators that has shown beneficial effects in inflammatory disease models. Recently, two distinct types of receptor molecules were discovered as the targets of maresin-1, further revealing the pro-resolution mechanism of maresin-1. One is retinoic acid-related orphan receptor α (RORα) and the another one is leucine-rich repeat domain-containing G protein-coupled receptor 6 (LGR6). In this review, we summarized the detailed role of maresin-1 and its two different receptors in respiratory diseases. RORα and LGR6 are potential targets for the treatment of respiratory diseases. Future basic research and clinical trials on MaR1 and its receptors should provide useful information for the treatment of respiratory diseases.

Orphan receptors in prostate cancer

BACKGROUND

The identification of new cellular receptors has been increasing rapidly. A receptor is called "orphan" if an endogenous ligand has not been identified yet.

METHODS

Here we review receptors that contribute to prostate cancer and are considered orphan or partially orphan. This means that the full spectrum of their endogenous ligands remains unknown.

RESULTS

The orphan receptors are divided into two major families. The first group includes G protein-coupled receptors. Most are orphan olfactory receptors. OR51E1 inhibits cell proliferation and induces senescence in prostate cancer. OR51E2 inhibits prostate cancer growth, but promotes invasiveness and metastasis. GPR158, GPR110, and GPCR-X play significant roles in prostate cancer development and progression. However, GPR160 induces cell cycle arrest and apoptosis. The other major subset of orphan receptors are nuclear receptors. Receptor-related orphan receptor α (RORα) inhibits tumor growth, but RORγ stimulates androgen receptor signaling. PXR contributes to metabolic deactivation of androgens and inhibits cell proliferation. TLX has protumorigenic effects in prostate cancer, while its knockdown triggers cellular senescence and growth arrest. Estrogen-related receptor ERRγ can inhibit tumor growth but ERRα is protumorigenic. Dax1 and short heterodimeric partner are also inhibitory in prostate cancer.

CONCLUSION

There is a "zoo" of relatively underappreciated orphan receptors that play key roles in prostate cancer.

Bmal1- and Per2-mediated regulation of the osteogenic differentiation and proliferation of mouse bone marrow mesenchymal stem cells by modulating the Wnt/β-catenin pathway

BACKGROUND

Bmal1 and Per2 are the core components of the circadian clock genes (CCGs). Bmal1-/- mice exhibit premature aging, as indicated by hypotrichosis and osteoporosis, with a loss of proliferation ability. The same occurs in Per2-/- mice, albeit to a less severe degree. However, whether the effects of Bmal1 and Per2 on proliferation and osteogenic differentiation are synergistic or antagonistic remains unclear. Thus, our study aimed to explore the effects and specific mechanism.

METHODS AND RESULTS

Lentiviral and adenoviral vectors were constructed to silence or overexpress Bmal1 or Per2 and MTT, flow cytometry, RT-qPCR, WB, immunohistochemistry, alizarin red staining and ChIP-Seq analyses were applied to identify the possible mechanism. The successful knockdown and overexpression of Bmal1/Per2 were detected by fluorescence microcopy. Flow cytometry found out that Bmal1 or Per2 knockdown resulted in G1-phase cell cycle arrest. RT-qPCR showed the different expression levels of Wnt-3a, c-myc1 and axin2 in the Wnt/β-catenin signaling pathway as well as the gene expression change of Rorα and Rev-erbα. Meanwhile, related proteins such as β-catenin, TCF-1, and P-GSK-3β were detected. ALP activity and the amount of mineral nodules were compared. ChIP-Seq results showed the possible mechanism.

CONCLUSIONS

Bmal1 and Per2, as primary canonical clock genes, showed synergistic effects on the proliferation and differentiation of BMSCs. They would inhibit the Wnt/β-catenin signaling pathway by downregulating Rorα expression or upregulating Rev-erbα expression, both of which were also key elements of CCGs. And this may be the mechanism by which they negatively regulate the osteogenic differentiation of BMSCs. Bmal1 and Per2 show synergistic effects in the proliferation of BMSCs. In addition, they play a synergistic role in negatively regulating the osteogenic differentiation ability of BMSCs. Bmal1 and Per2 may regulate the aging of BMSCs by altering cell proliferation and osteogenic differentiation through Rorα and Rev-erbα to affect Wnt/β-catenin pathway.

Circadian rhythms and cancers: the intrinsic links and therapeutic potentials

The circadian rhythm is an evolutionarily conserved time-keeping system that comprises a wide variety of processes including sleep-wake cycles, eating-fasting cycles, and activity-rest cycles, coordinating the behavior and physiology of all organs for whole-body homeostasis. Acute disruption of circadian rhythm may lead to transient discomfort, whereas long-term irregular circadian rhythm will result in the dysfunction of the organism, therefore increasing the risks of numerous diseases especially cancers. Indeed, both epidemiological and experimental evidence has demonstrated the intrinsic link between dysregulated circadian rhythm and cancer. Accordingly, a rapidly increasing understanding of the molecular mechanisms of circadian rhythms is opening new options for cancer therapy, possibly by modulating the circadian clock. In this review, we first describe the general regulators of circadian rhythms and their functions on cancer. In addition, we provide insights into the mechanisms underlying how several types of disruption of the circadian rhythm (including sleep-wake, eating-fasting, and activity-rest) can drive cancer progression, which may expand our understanding of cancer development from the clock perspective. Moreover, we also summarize the potential applications of modulating circadian rhythms for cancer treatment, which may provide an optional therapeutic strategy for cancer patients.

Identification of the RORα Transcriptional Network Contributes to the Search for Therapeutic Targets in Atherosclerosis

The retinoic acid receptor-related orphan receptor α (RORα) is involved in the regulation of several physiological processes, including development, metabolism, and circadian rhythm. RORα-deficient mice display profound atherosclerosis, in which hypoalphalipoproteinemia is reportedly associated with decreased plasma levels of high-density lipoprotein, increased levels of inflammatory cytokines, and ischemia/reperfusion-induced damage. The recent characterization of endogenous ligands (including cholesterol, oxysterols, provitamin D₃, and their derivatives), mediators, and initiation complexes associated with the transcriptional regulation of these orphan nuclear receptors has facilitated the development of synthetic ligands. These findings have also highlighted the potential of application of RORα as a therapeutic target for several diseases, including diabetes, dyslipidemia, and atherosclerosis. In this review, the current literature related to the structure and function of RORα, its genetic inter-individual differences, and its potential as a therapeutic target in atherosclerosis is discussed.

Unraveling the physiological roles of retinoic acid receptor-related orphan receptor α

Retinoic acid receptor-related orphan receptor-α (RORα) is a member of the orphan nuclear receptor family and functions as a transcriptional activator in response to circadian changes. Circadian rhythms are complex cellular mechanisms regulating diverse metabolic, inflammatory, and tumorigenic gene expression pathways that govern cyclic cellular physiology. Disruption of circadian regulators, including RORα, plays a critical role in tumorigenesis and facilitates the development of inflammatory hallmarks. Although RORα contributes to overall fitness among anticancer, anti-inflammatory, lipid homeostasis, and circadian clock mechanisms, the molecular mechanisms underlying the mode of transcriptional regulation by RORα remain unclear. Nonetheless, RORα has important implications for pharmacological prevention of cancer, inflammation, and metabolic diseases, and understanding context-dependent RORα regulation will provide an innovative approach for unraveling the functional link between cancer metabolism and rhythm changes.

ROR: Nuclear Receptor for Melatonin or Not?

Whether the retinoic acid-related orphan receptor (ROR) is a nuclear receptor of melatonin remains controversial. ROR is inextricably linked to melatonin in terms of its expression, function, and mechanism of action. Additionally, studies have illustrated that melatonin functions analogous to ROR ligands, thereby modulating the transcriptional activity of ROR. However, studies supporting these interactions have since been withdrawn. Furthermore, recent crystallographic evidence does not support the view that ROR is a nuclear receptor of melatonin. Some other studies have proposed that melatonin indirectly regulates ROR activity rather than directly binding to ROR. This review aims to delve into the complex relationship of the ROR receptor with melatonin in terms of its structure, expression, function, and mechanism. Thus, we provide the latest evidence and views on direct binding as well as indirect regulation of ROR by melatonin, dissecting both viewpoints in-depth to provide a more comprehensive perspective on this issue.

Prospects of circadian clock in joint cartilage development

Altering the food intake, exercise, and sleep patterns have a great influence on the homeostasis of the biological clock. This leads to accelerated aging of the articular cartilage, susceptibility to arthropathy and other aspects. Deficiency or overexpression of certain circadian clock-related genes accelerates the cartilage deterioration and leads to phenotypic variation in different joints. The process of joint cartilage development includes the formation of joint site, interzone, joint cavitation, epiphyseal ossification center, and cartilage maturation. The mechanism by which, biological clock regulates the cell-cycle, growth, metabolism, and other biological processes of chondrocytes is poorly understood. Here, we summarized the interaction between biological clock proteins and developmental pathways in chondrogenesis and provided the evidence from other tissues that further predicts the molecular patterns of these protein-protein networks in activation, proliferation, and differentiation. The purpose of this review is to gain deeper understanding of the evolution of cartilage and its irreversibility seen in damage and aging.

Isoform-Specific Lysine Methylation of RORα2 by SETD7 Is Required for Association of the TIP60 Coactivator Complex in Prostate Cancer Progression

The retinoid acid-related orphan receptor α (RORα), a member of the orphan nuclear receptor superfamily, functions as an unknown ligand-dependent transcription factor. RORα was shown to regulate a broad array of physiological processes such as Purkinje cell development in the cerebellum, circadian rhythm, lipid and bone metabolism, inhibition of inflammation, and anti-apoptosis. The human RORα gene encodes at least four distinct isoforms (RORα1, -2, -3, -4), which differ only in their N-terminal domain (NTD). Two isoforms, RORα2 and 3, are not expressed in mice, whereas RORα1 and 4 are expressed both in mice and humans. In the present study, we identified the specific NTD of RORα2 that enhances prostate tumor progression and proliferation via lysine methylation-mediated recruitment of coactivator complex pontin/Tip60. Upregulation of the RORα2 isoform in prostate cancers putatively promotes tumor formation and progression. Furthermore, binding between coactivator complex and RORα2 is increased by lysine methylation of RORα2 because methylation permits subsequent interaction with binding partners. This methylation-dependent activation is performed by SET domain containing 7 (SETD7) methyltransferase, inducing the oncogenic potential of RORα2. Thus, post-translational lysine methylation of RORα2 modulates oncogenic function of RORα2 in prostate cancer. Exploration of the post-translational modifications of RORα2 provides new avenues for the development of tumor-suppressive therapeutic agents through modulating the human isoform-specific tumorigenic role of RORα2.

Impact of chronically alternating light-dark cycles on circadian clock mediated expression of cancer (glioma)-related genes in the brain

Disruption of the circadian rhythm is a risk factor for cancer, while glioma is a leading contributor to mortality worldwide. Substantial efforts are being undertaken to decrypt underlying molecular pathways. Our understanding of the mechanisms through which disrupted circadian rhythm induces glioma development and progression is incomplete. We, therefore, examined changes in the expression of glioma-related genes in the mouse brain after chronic jetlag (CJL) exposure. A total of 22 candidate tumor suppressor (n= 14) and oncogenes (n= 8) were identified and analyzed for their interaction with clock genes. Both the control and CJL groups were investigated for the expression of candidate genes in the nucleus accumbens, hippocampus, prefrontal cortex, hypothalamus, and striatum of wild type, Bmal1-/- and Cry1/2 double knockout male mice. We found significant variations in the expression of candidate tumor suppressor and oncogenes in the brain tissues after CJL treatment in the wild type, Bmal1-/- and Cry1/2 double knockout mice. In response to CJL treatment, some of the genes were regulated in the wild type, Bmal1-/- and Cry1/2 similarly. However, the expression of some of the genes indicated their association with the functional clock. Overall, our result suggests a link between CJL and gliomas risk at least partially dependent on the circadian clock. However, further studies are needed to investigate the molecular mechanism associated with CJL and gliomas.

The Role of Nuclear Receptors in Prostate Cancer

The nuclear receptor (NR) superfamily consists of 48 members that are divided into seven subfamilies. NRs are transcription factors that play an important role in a number of biological processes. The NR superfamily includes androgen receptor, which is a key player in prostate cancer pathogenesis, suggesting the functional roles of other NRs in prostate cancer. The findings on the roles of NRs in prostate cancer thus far have shown that several NRs such as vitamin D receptor, estrogen receptor β, and mineralocorticoid receptor play antioncogenic roles, while other NRs such as peroxisome proliferator-activated receptor γ and estrogen receptor α as well as androgen receptor play oncogenic roles. However, the roles of other NRs in prostate cancer remain controversial or uninvestigated. Further research on the role of NRs in prostate cancer is required and may lead to the development of novel preventions and therapeutics for prostate cancer.