G1/S cell cycle regulators mediate effects of circadian dysregulation on tumor growth and provide targets for timed anticancer treatment

The Histone Variant MacroH2A1 Impacts Circadian Gene Expression and Cell Phenotype in an In Vitro Model of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide. A foremost risk factor for HCC is obesity/metabolic syndrome-related non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), which is prompted by remarkable changes in transcription patterns of genes enriching metabolic, immune/inflammatory, and circadian pathways. Epigenetic mechanisms play a role in NAFLD-associated HCC, and macroH2A1, a variant of histone H2A, is involved in the pathogenesis modulating the expression of oncogenes and/or tumor suppressor genes and interacting with SIRT1, which crucially impacts the circadian clock circuitry. Hence, we aimed to appraise if and how macroH2A1 regulated the expression patterns of circadian genes in the setting of NAFLD-associated HCC. We took advantage of an in vitro model of liver cancer represented by HepG2 (human hepatocarcinoma) cells stably knocked down for macroH2A1 and conducted whole transcriptome profiling and deep phenotyping analysis. We found up-regulation of PER1 along with several deregulated circadian genes, enriching several important pathways and functions related to cancer onset and progression, such as epithelial-to-mesenchymal transition, cell cycle deregulation, and DNA damage. PER1 silencing partially mitigated the malignant phenotype induced by the loss of macroH2A1 in HCC cells. In conclusion, our findings suggest a modulatory role for the core circadian protein PER1 in liver carcinogenesis in the context of a lack of the macroH2A1 epigenetic and transcriptional landscape.

Circadian clock, carcinogenesis, chronochemotherapy connections

The circadian clock controls the expression of nearly 50% of protein coding genes in mice and most likely in humans as well. Therefore, disruption of the circadian clock is presumed to have serious pathological effects including cancer. However, epidemiological studies on individuals with circadian disruption because of night shift or rotating shift work have produced contradictory data not conducive to scientific consensus as to whether circadian disruption increases the incidence of breast, ovarian, prostate, or colorectal cancers. Similarly, genetically engineered mice with clock disruption do not exhibit spontaneous or radiation-induced cancers at higher incidence than wild-type controls. Because many cellular functions including the cell cycle and cell division are, at least in part, controlled by the molecular clock components (CLOCK, BMAL1, CRYs, PERs), it has also been expected that appropriate timing of chemotherapy may increase the efficacy of chemotherapeutic drugs and ameliorate their side effect. However, empirical attempts at chronochemotherapy have not produced beneficial outcomes. Using mice without and with human tumor xenografts, sites of DNA damage and repair following treatment with the anticancer drug cisplatin have been mapped genome-wide at single nucleotide resolution and as a function of circadian time. The data indicate that mechanism-based studies such as these may provide information necessary for devising rational chronochemotherapy regimens.

MYC Ran Up the Clock: The Complex Interplay between MYC and the Molecular Circadian Clock in Cancer

The MYC oncoprotein and its family members N-MYC and L-MYC are known to drive a wide variety of human cancers. Emerging evidence suggests that MYC has a bi-directional relationship with the molecular clock in cancer. The molecular clock is responsible for circadian (~24 h) rhythms in most eukaryotic cells and organisms, as a mechanism to adapt to light/dark cycles. Disruption of human circadian rhythms, such as through shift work, may serve as a risk factor for cancer, but connections with oncogenic drivers such as MYC were previously not well understood. In this review, we examine recent evidence that MYC in cancer cells can disrupt the molecular clock; and conversely, that molecular clock disruption in cancer can deregulate and elevate MYC. Since MYC and the molecular clock control many of the same processes, we then consider competition between MYC and the molecular clock in several select aspects of tumor biology, including chromatin state, global transcriptional profile, metabolic rewiring, and immune infiltrate in the tumor. Finally, we discuss how the molecular clock can be monitored or diagnosed in human tumors, and how MYC inhibition could potentially restore molecular clock function. Further study of the relationship between the molecular clock and MYC in cancer may reveal previously unsuspected vulnerabilities which could lead to new treatment strategies.

Exploring the link between chronobiology and drug delivery: effects on cancer therapy

Circadian clock is an impressive timing system responsible for the control of several metabolic, physiological and behavioural processes. Nowadays, the connection between the circadian clock and cancer occurrence and development is consensual. Therefore, the inclusion of circadian timing into cancer therapy may potentially offer a more effective and less toxic approach. This way, chronotherapy has been shown to improve cancer treatment efficacy. Despite this relevant finding, its clinical application is poorly exploited. The conception of novel anticancer drug delivery systems and the combination of chronobiology with nanotechnology may provide a powerful tool to optimize cancer therapy, instigating the incorporation of the circadian timing into clinical practice towards a more personalized drug delivery. This review focuses on the recent advances in the field of cancer chronobiology, on the link between cancer and the disruption of circadian rhythms and on the promising targeted drug nanodelivery approaches aiming the clinical application of cancer chronotherapy.

Cistanche tubulosa Phenylethanoid Glycosides Induce Apoptosis of Hepatocellular Carcinoma Cells by Mitochondria-Dependent and MAPK Pathways and Enhance Antitumor Effect through Combination with Cisplatin

Cistanche tubulosa is a type of Chinese herbal medicine and exerts various biological functions. Previous studies have been demonstrated that Cistanche tubulosa phenylethanoid glycosides (CTPG) exhibit antitumor effects on a variety of tumor cells. However, the antitumor effects of CTPG on HepG2 and BEL-7404 hepatocellular carcinoma (HCC) cells are still elusive. Our study showed that CTPG significantly inhibited the growth of HepG2 and BEL-7404 cells through the induction of cell cycle arrest and apoptosis, which was associated with the activation of MAPK pathways characterized by the up-regulated phosphorylation of p38, JNK, and ERK1/2 and mitochondria-dependent pathway characterized by the reduction of mitochondrial membrane potential. The release of cytochrome c and the cleavage of caspase-3, -7, -9, and PARP were subsequently increased by CTPG treatment. Moreover, CTPG significantly suppressed the migration of HepG2 through reducing the levels of matrix metalloproteinase-2 and vascular endothelial growth factor. Interestingly, CTPG not only enhanced the proliferation of splenocytes but also reduced the apoptosis of splenocytes induced by cisplatin. In H22 tumor mouse model, CTPG combined with cisplatin further inhibited the growth of H22 cells and reduced the side effects of cisplatin. Taken together, CTPG inhibited the growth of HCC through direct antitumor effect and indirect immunoenhancement effect, and improved the antitumor efficacy of cisplatin.

Preclinical Advances in Theranostics for the Different Molecular Subtypes of Breast Cancer

Breast cancer is the most common cancer in women worldwide. The heterogeneity of breast cancer and drug resistance to therapies make the diagnosis and treatment difficult. Molecular imaging methods with positron emission tomography (PET) and single-photon emission tomography (SPECT) provide useful tools to diagnose, predict, and monitor the response of therapy, contributing to precision medicine for breast cancer patients. Recently, many efforts have been made to find new targets for breast cancer therapy to overcome resistance to standard of care treatments, giving rise to new therapeutic agents to offer more options for patients with breast cancer. The combination of diagnostic and therapeutic strategies forms the foundation of theranostics. Some of these theranostic agents exhibit high potential to be translated to clinic. In this review, we highlight the most recent advances in theranostics of the different molecular subtypes of breast cancer in preclinical studies.

Night shift schedule causes circadian dysregulation of DNA repair genes and elevated DNA damage in humans

Circadian disruption has been identified as a risk factor for health disorders such as obesity, cardiovascular disease, and cancer. Although epidemiological studies suggest an increased risk of various cancers associated with circadian misalignment due to night shift work, the underlying mechanisms have yet to be elucidated. We sought to investigate the potential mechanistic role that circadian disruption of cancer hallmark pathway genes may play in the increased cancer risk in shift workers. In a controlled laboratory study, we investigated the circadian transcriptome of cancer hallmark pathway genes and associated biological pathways in circulating leukocytes obtained from healthy young adults during a 24-hour constant routine protocol following 3 days of simulated day shift or night shift. The simulated night shift schedule significantly altered the normal circadian rhythmicity of genes involved in cancer hallmark pathways. A DNA repair pathway showed significant enrichment of rhythmic genes following the simulated day shift schedule, but not following the simulated night shift schedule. In functional assessments, we demonstrated that there was an increased sensitivity to both endogenous and exogenous sources of DNA damage after exposure to simulated night shift. Our results suggest that circadian dysregulation of DNA repair may increase DNA damage and potentiate elevated cancer risk in night shift workers.

The role of the circadian clock in cancer hallmark acquisition and immune-based cancer therapeutics

The circadian system temporally regulates physiology to maintain homeostasis. Co-opting and disrupting circadian signals appear to be distinct attributes that are functionally important for the development of a tumor and can enable or give rise to the hallmarks that tumors use to facilitate their initiation, growth and progression. Because circadian signals are also strong regulators of immune cell proliferation, trafficking and exhaustion states, they play a role in how tumors respond to immune-based cancer therapeutics. While immuno-oncology has heralded a paradigm shift in cancer therapeutics, greater accuracy is needed to increase our capability of predicting who will respond favorably to, or who is likely to experience the troubling adverse effects of, immunotherapy. Insights into circadian signals may further refine our understanding of biological determinants of response and help answer the fundamental question of whether certain perturbations in circadian signals interfere with the activity of immune checkpoint inhibitors. Here we review the body of literature highlighting circadian disruption as a cancer promoter and synthesize the burgeoning evidence suggesting circadian signals play a role in how tumors respond to immune-based anti-cancer therapeutics. The goal is to develop a framework to advance our understanding of the relationships between circadian markers, cancer biology, and immunotherapeutics. Bolstered by this new understanding, these relationships may then be pursued in future clinical studies to improve our ability to predict which patients will respond favorably to, and avoid the adverse effects of, traditional and immune-based cancer therapeutics.

Clock at the Core of Cancer Development

To synchronize various biological processes with the day and night cycle, most organisms have developed circadian clocks. This evolutionarily conserved system is important in the temporal regulation of behavior, physiology and metabolism. Multiple pathological changes associated with circadian disruption support the importance of the clocks in mammals. Emerging links have revealed interplay between circadian clocks and signaling networks in cancer. Understanding the cross-talk between the circadian clock and tumorigenesis is imperative for its prevention, management and development of effective treatment options. In this review, we summarize the role of the circadian clock in regulation of one important metabolic pathway, insulin/IGF1/PI3K/mTOR signaling, and how dysregulation of this metabolic pathway could lead to uncontrolled cancer cell proliferation and growth. Targeting the circadian clock and rhythms either with recently discovered pharmaceutical agents or through environmental cues is a new direction in cancer chronotherapy. Combining the circadian approach with traditional methods, such as radiation, chemotherapy or the recently developed, immunotherapy, may improve tumor response, while simultaneously minimizing the adverse effects commonly associated with cancer therapies.

Clocks, cancer, and chronochemotherapy

The circadian clock coordinates daily rhythmicity of biochemical, physiologic, and behavioral functions in humans. Gene expression, cell division, and DNA repair are modulated by the clock, which gives rise to the hypothesis that clock dysfunction may predispose individuals to cancer. Although the results of many epidemiologic and animal studies are consistent with there being a role for the clock in the genesis and progression of tumors, available data are insufficient to conclude that clock disruption is generally carcinogenic. Similarly, studies have suggested a circadian time-dependent efficacy of chemotherapy, but clinical trials of chronochemotherapy have not demonstrated improved outcomes compared with conventional regimens. Future hypothesis-driven and discovery-oriented research should focus on specific interactions between clock components and carcinogenic mechanisms to realize the full clinical potential of the relationship between clocks and cancer.

The 2020 Pittendrigh/Aschoff Lecture: My Circadian Journey

The circadian field has come a long way since I started as a postdoctoral fellow ~30 years ago. At the time, the only known animal clock gene was period, so I had the privilege of witnessing, and participating in, the molecular revolution that took us from the discovery of the circadian clock mechanism to the identification of pathways that link clocks to behavior and physiology. This lecture highlights my role and perspective in these developments, and also demonstrates how the successful use of Drosophila for studies of circadian rhythms inspired us to develop a fly model for sleep. I also touch upon my experiences as a non-white immigrant woman navigating my way through the US science and education system, and hope my story will be of interest to some.

Time-of-day specificity of anticancer drugs may be mediated by circadian regulation of the cell cycle

Circadian rhythms are an integral part of physiology, underscoring their relevance for the treatment of disease. We conducted cell-based high-throughput screening to investigate time-of-day influences on the activity of known antitumor agents and found that many compounds exhibit daily rhythms of cytotoxicity concomitant with previously reported oscillations of target genes. Rhythmic action of HSP90 inhibitors was mediated by specific isoforms of HSP90, genetic perturbation of which affected the cell cycle. Furthermore, clock mutants affected the cell cycle in parallel with abrogating rhythms of cytotoxicity, and pharmacological inhibition of the cell cycle also eliminated rhythmic drug effects. An HSP90 inhibitor reduced growth rate of a mouse melanoma in a time-of-day-specific manner, but efficacy was impaired in clock-deficient tumors. These results provide a powerful rationale for appropriate daily timing of anticancer drugs and suggest circadian regulation of the cell cycle within the tumor as an underlying mechanism.

The interaction of the circadian and immune system: Desynchrony as a pathological outcome to traumatic brain injury

Traumatic brain injury (TBI) is a complex and costly worldwide phenomenon that can lead to many negative health outcomes including disrupted circadian function. There is a bidirectional relationship between the immune system and the circadian system, with mammalian coordination of physiological activities being controlled by the primary circadian pacemaker in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN receives light information from the external environment and in turn synchronizes rhythms throughout the brain and body. The SCN is capable of endogenous self-sustained oscillatory activity through an intricate clock gene negative feedback loop. Following TBI, the response of the immune system can become prolonged and pathophysiological. This detrimental response not only occurs in the brain, but also within the periphery, where a leaky blood brain barrier can permit further infiltration of immune and inflammatory factors. The prolonged and pathological immune response that follows TBI can have deleterious effects on clock gene cycling and circadian function not only in the SCN, but also in other rhythmic areas throughout the body. This could bring about a state of circadian desynchrony where different rhythmic structures are no longer working together to promote optimal physiological function. There are many parallels between the negative symptomology associated with circadian desynchrony and TBI. This review discusses the significant contributions of an immune-disrupted circadian system on the negative symptomology following TBI. The implications of TBI symptomology as a disorder of circadian desynchrony are discussed.

Circadian disruption promotes tumor-immune microenvironment remodeling favoring tumor cell proliferation

Circadian disruption negatively affects physiology, posing a global health threat that manifests in proliferative, metabolic, and immune diseases, among others. Because outputs of the circadian clock regulate daily fluctuations in the immune response, we determined whether circadian disruption results in tumor-associated immune cell remodeling, facilitating tumor growth. Our findings show that tumor growth rate increased and latency decreased under circadian disruption conditions compared to normal light-dark (LD) schedules in a murine melanoma model. Circadian disruption induced the loss or inversion of daily patterns of M1 (proinflammatory) and M2 (anti-inflammatory) macrophages and cytokine levels in spleen and tumor tissues. Circadian disruption also induced (i) deregulation of rhythmic expression of clock genes and (ii) of cyclin genes in the liver, (iii) increased CcnA2 levels in the tumor, and (iv) dampened expression of the cell cycle inhibitor p21WAF/CIP1 , all of which contribute to a proliferative phenotype.

Cancer in the Fourth Dimension: What Is the Impact of Circadian Disruption?

Circadian rhythms integrate many physiological pathways, helping organisms to align the timing of various internal processes to daily cycles in the external environment. Disrupted circadian rhythmicity is a prominent feature of modern society, and has been designated as a probable carcinogen. Here, we review multiple studies, in humans and animal models, that suggest a causal effect between circadian disruption and increased risk of cancer. We also discuss the complexity of this connection, which may depend on the cellular context. SIGNIFICANCE: Accumulating evidence points to an adverse effect of circadian disruption on cancer incidence and progression, indicating that time of day could influence the effectiveness of interventions targeting cancer prevention and management.

Circadian clock effects on cellular proliferation: Insights from theory and experiments

Oscillations of the cellular circadian clock have emerged as an important regulator of many physiological processes, both in health and in disease. One such process, cellular proliferation, is being increasingly recognized to be affected by the circadian clock. Here, we review how a combination of experimental and theoretical work has furthered our understanding of the way circadian clocks couple to the cell cycle and play a role in tissue homeostasis and cancer. Finally, we discuss recently introduced methods for modeling coupling of clocks based on techniques from survival analysis and machine learning and highlight their potential importance for future studies.

Cancer, hear my battle CRY

Circadian clocks are cell-autonomous self-sustaining oscillators that allow organisms to anticipate environmental changes throughout the solar day and persist in nearly every cell examined. Environmental or genetic disruption of circadian rhythms increases the risk of several types of cancer, but the underlying mechanisms are not well understood. Here, we discuss evidence connecting circadian rhythms-with emphasis on the cryptochrome proteins (CRY1/2)-to cancer through in vivo models, mechanisms involving known tumor suppressors and oncogenes, chemotherapeutic efficacy, and human cancer risk.

Circadian and Sleep Metabolomics Across Species

Under normal circadian function, metabolic control is temporally coordinated across tissues and behaviors with a 24-h period. However, circadian disruption results in negative consequences for metabolic homeostasis including energy or redox imbalances. Yet, circadian disruption has become increasingly prevalent within today's society due to many factors including sleep loss. Metabolic consequences of both have been revealed by metabolomics analyses of circadian biology and sleep. Specifically, two primary analytical platforms, mass spectrometry and nuclear magnetic resonance spectroscopy, have been used to study molecular clock and sleep influences on overall metabolic rhythmicity. For example, human studies have demonstrated the prevalence of metabolic rhythms in human biology, as well as pan-metabolome consequences of sleep disruption. However, human studies are limited to peripheral metabolic readouts primarily through minimally invasive procedures. For further tissue- and organism-specific investigations, a number of model systems have been studied, based upon the conserved nature of both the molecular clock and sleep across species. Here we summarize human studies as well as key findings from metabolomics studies using mice, Drosophila, and zebrafish. While informative, a limitation in existing literature is a lack of interpretation regarding dynamic synthesis or catabolism within metabolite pools. To this extent, future work incorporating isotope tracers, specific metabolite reporters, and single-cell metabolomics may provide a means of exploring dynamic activity in pathways of interest.

Reactive oxygen species-mediated cellular genotoxic stress is involved in 1-nitropyrene-induced trophoblast cycle arrest and fetal growth restriction

1-nitropyrene (1-NP) is a key component of diesel exhaust-sourced fine particulate matter (PM2.5). Our recent study demonstrated that gestational 1-NP exposure caused placental proliferation inhibition and fetal intrauterine growth restriction (IUGR). This study aimed to investigate the role of genotoxic stress on 1-NP-induced placental proliferation inhibition and fetal IUGR. Human trophoblasts were exposed to 1-NP (10 μM). Growth index was reduced and PCNA was downregulated in 1-NP-exposed placental trophoblasts. More than 90% of 1-NP-exposed trophoblasts were arrested in either G0/G1 or G2/M phases. CDK1 and cyclin B, two G2/M cycle-related proteins, and CDK2, a G0/G1 cycle-related protein, were reduced in 1-NP-exposed trophoblasts. Phosphorylated Rb, a downstream molecule of CDK2, was inhibited in 1-NP-exposed trophoblasts. Moreover, DNA double-strand break was observed and γ-H2AX, another indicator of DNA double-strand break, was upregulated in 1-NP-exposed trophoblasts. Phosphorylated ATM, a key molecule of genotoxic stress, and its downstream molecule Chk2 were elevated. By contrast, Cdc25A, a downstream target of Chk2, was reduced in 1-NP-exposed trophoblasts. Phenyl-N-t-butylnitrone (PBN), a free radical scavenger, inhibited 1-NP-induced genotoxic stress and trophoblast cycle arrest. Animal experiment showed that N-acetylcysteine (NAC), an antioxidant, rescued 1-NP-induced placental proliferation inhibition and fetal IUGR in mice. These results provide evidence that reactive oxygen species (ROS)-mediated cellular genotoxic stress partially contributes to 1-NP-induced placental proliferation inhibition and fetal IUGR.

Sex-dependent least toxic timing of irinotecan combined with chronomodulated chemotherapy for metastatic colorectal cancer: Randomized multicenter EORTC 05011 trial

The least toxic time (LTT) of irinotecan varied by up to 8 hours according to sex and genetic background in mice. The translational relevance was investigated within a randomized trial dataset, where no LTT stood out significantly in the whole population. 130 male and 63 female eligible patients with metastatic colorectal cancer were randomized to receive chronomodulated Irinotecan with peak delivery rate at 1 of 6 clock hours staggered by 4 hours on day 1, then fixed-time chronomodulated Fluorouracil-Leucovorin-Oxaliplatin for 4 days, q3 weeks. The sex-specific circadian characteristics of grade (G) 3-4 toxicities were mapped with cosinor and time*sex interactions confirmed with Fisher's exact test. Baseline characteristics of male or female patients were similar in the six treatment groups. Main grade 3-4 toxicities over six courses were diarrhea (males vs females, 39.2%; vs 46.0%), neutropenia (15.6% vs 15.0%), fatigue (11.5% vs 15.9%), and anorexia (10.0% vs 7.8%). They were reduced following irinotecan peak delivery in the morning for males, but in the afternoon for females, with statistically significant rhythms (P < .05 from cosinor) and sex*timing interactions (Fisher's exact test, diarrhea, P = .023; neutropenia, P = .015; fatigue, P = .062; anorexia, P = .032). Irinotecan timing was most critical for females, with grades 3-4 ranging from 55.2% of the patients (morning) to 29.4% (afternoon) for diarrhea, and from 25.9% (morning) to 0% (afternoon) for neutropenia. The study results support irinotecan administration in the morning for males and in the afternoon for females, in order to minimize adverse events without impairing efficacy.

Analysis of the Circadian Regulation of Cancer Hallmarks by a Cross-Platform Study of Colorectal Cancer Time-Series Data Reveals an Association with Genes Involved in Huntington's Disease

Accumulating evidence points to a link between circadian clock dysfunction and the molecular events that drive tumorigenesis. Here, we investigated the connection between the circadian clock and the hallmarks of cancer in an in vitro model of colorectal cancer (CRC). We used a cross-platform data normalization method to concatenate and compare available microarray and RNA-sequencing time series data of CRC cell lines derived from the same patient at different disease stages. Our data analysis suggests differential regulation of molecular pathways between the CRC cells and identifies several of the circadian and likely clock-controlled genes (CCGs) as cancer hallmarks and circadian drug targets. Notably, we found links of the CCGs to Huntington’s disease (HD) in the metastasis-derived cells. We then investigated the impact of perturbations of our candidate genes in a cohort of 439 patients with colon adenocarcinoma retrieved from the Cancer Genome Atlas (TCGA). The analysis revealed a correlation of the differential expression levels of the candidate genes with the survival of patients. Thus, our study provides a bioinformatics workflow that allows for a comprehensive analysis of circadian properties at different stages of colorectal cancer, and identifies a new association between cancer and HD.

miR-21-5p promotes cell proliferation and G1/S transition in melanoma by targeting CDKN2C

Human melanoma is a highly malignant tumor originating from cutaneous melanocytes. The noncoding RNA microRNA (miR)‐21‐5p has been reported to be expressed at high levels in malignant melanocytic skin tissues, but its potential functional role in melanoma remains poorly understood. Here, we explored the cellular effects of miR‐21‐5p on melanoma in vitro and the underlying mechanisms. Quantitative real‐time PCR was used to show that miR‐21‐5p is significantly up‐regulated in clinical samples from patients with melanoma as compared with adjacent noncancerous tissues. Overexpression of miR‐21‐5p significantly enhanced, whereas knockdown attenuated, cell proliferation and G1/S transition in melanoma cell lines (A375 and M14). Luciferase reporter assays were used to show that the cyclin‐dependent kinase inhibitor 2C (CDKN2C) is a downstream target of miR‐21‐5p. Furthermore, miR‐21‐5p mimics resulted in a decrease in CDKN2C expression, and CDKN2C expression was observed to be inversely correlated with miR‐21‐5p expression in melanoma tissues. Rescue experiments were performed to show that overexpression of CDKN2C partially reversed the effects of miR‐21‐5p up‐regulation on A375 cells. Consistently, knockdown of CDKN2C abolished the effects of miR‐21‐5p down‐regulation on A375 cells. Overall, our studies demonstrate that miR‐21‐5p can promote the growth of melanoma cells by targeting CDKN2C, which may induce G0/G1 phase arrest of melanoma cells.

On the Neuroprotective Effects of Naringenin: Pharmacological Targets, Signaling Pathways, Molecular Mechanisms, and Clinical Perspective

As a group of progressive, chronic, and disabling disorders, neurodegenerative diseases (NDs) affect millions of people worldwide, and are on the rise. NDs are known as the gradual loss of neurons; however, their pathophysiological mechanisms have not been precisely revealed. Due to the complex pathophysiological mechanisms behind the neurodegeneration, investigating effective and multi-target treatments has remained a clinical challenge. Besides, appropriate neuroprotective agents are still lacking, which raises the need for new therapeutic agents. In recent years, several reports have introduced naturally-derived compounds as promising alternative treatments for NDs. Among natural entities, flavonoids are multi-target alternatives affecting different pathogenesis mechanisms in neurodegeneration. Naringenin is a natural flavonoid possessing neuroprotective activities. Increasing evidence has attained special attention on the variety of therapeutic targets along with complex signaling pathways for naringenin, which suggest its possible therapeutic applications in several NDs. Here, in this review, the neuroprotective effects of naringenin, as well as its related pharmacological targets, signaling pathways, molecular mechanisms, and clinical perspective, are described. Moreover, the need to develop novel naringenin delivery systems is also discussed to solve its widespread pharmacokinetic limitation.

The Cancer Clock Is (Not) Ticking: Links between Circadian Rhythms and Cancer

Circadian rhythms regulate many physiological and behavioral processes, including sleep, metabolism and cell division, which have a 24-h oscillation pattern. Rhythmicity is generated by a transcriptional–translational feedback loop in individual cells, which are synchronized by the central pacemaker in the brain and external cues. Epidemiological and clinical studies indicate that disruption of these rhythms can increase both tumorigenesis and cancer progression. Environmental changes (shift work, jet lag, exposure to light at night), mutations in circadian regulating genes, and changes to clock gene expression are recognized forms of disruption and are associated with cancer risk and/or cancer progression. Experimental data in animals and cell cultures further supports the role of the cellular circadian clock in coordinating cell division and DNA repair, and disrupted cellular clocks accelerate cancer cell growth. This review will summarize studies linking circadian disruption to cancer biology and explore how such disruptions may be further altered by common characteristics of tumors including hypoxia and acidosis. We will highlight how circadian rhythms might be exploited for cancer drug development, including how delivery of current chemotherapies may be enhanced using chronotherapy. Understanding the role of circadian rhythms in carcinogenesis and tumor progression will enable us to better understand causes of cancer and how to treat them.

Predictability of individual circadian phase during daily routine for medical applications of circadian clocks

BACKGROUNDCircadian timing of treatments can largely improve tolerability and efficacy in patients. Thus, drug metabolism and cell cycle are controlled by molecular clocks in each cell and coordinated by the core body temperature 24-hour rhythm, which is generated by the hypothalamic pacemaker. Individual circadian phase is currently estimated with questionnaire-based chronotype, center-of-rest time, dim light melatonin onset (DLMO), or timing of core body temperature (CBT) maximum (acrophase) or minimum (bathyphase).METHODSWe aimed at circadian phase determination and readout during daily routines in volunteers stratified by sex and age. We measured (a) chronotype, (b) every minute (q1min) CBT using 2 electronic pills swallowed 24 hours apart, (c) DLMO through hourly salivary samples from 1800 hours to bedtime, and (d) q1min accelerations and surface temperature at anterior chest level for 7 days, using a teletransmitting sensor. Circadian phases were computed using cosinor and hidden Markov modeling. Multivariate regression identified the combination of biomarkers that best predicted core temperature circadian bathyphase.RESULTSAmong the 33 participants, individual circadian phases were spread over 5 hours, 10 minutes (DLMO); 7 hours (CBT bathyphase); and 9 hours, 10 minutes (surface temperature acrophase). CBT bathyphase was accurately predicted, i.e., with an error less than 1 hour for 78.8% of the subjects, using a new digital health algorithm (INTime), combining time-invariant sex and chronotype score with computed center-of-rest time and surface temperature bathyphase (adjusted R2 = 0.637).CONCLUSIONINTime provided a continuous and reliable circadian phase estimate in real time. This model helps integrate circadian clocks into precision medicine and will enable treatment timing personalization following further validation.FUNDINGMedical Research Council, United Kingdom; AP-HP Foundation; and INSERM.

Chromobox homolog 8 (CBX8) Interacts with Y-Box binding protein 1 (YBX1) to promote cellular proliferation in hepatocellular carcinoma cells

Polycomb group (PcG) proteins have recently been identified as critical regulators in tumor initiation and development. However, the function of CBX8 in human hepatocellular carcinoma (HCC) remains largely unknown. Our study was designed to explore the biological function and clinical implication of CBX8 in HCC. We investigated the interplay between CBX8 and cell cycle through Gene Set Enrichment Analysis and western blotting. Bioinformatics tools and co-immunoprecipitation were used to explore cell cycle regulation. Finally, we studied the expression and clinical significance of CBX8 in HCC through 3 independent datasets. CBX8 was upregulated in HCC and its expression correlated with cell cycle progression. CyclinD1 was downregulated by CBX8 knockdown but upregulated by CBX8 overexpression. YBX1 interacted with CBX8 and regulated the cell cycle. Moreover, targeting YBX1 with specific siRNA impaired CBX8-mediated regulation of CyclinD1. CBX8 overexpression boosted HCC cell growth, while CBX8 knockdown suppressed cell proliferation. Further, YBX1 interacted with CBX8. YBX1 knockdown compromised the proliferation of CBX8 overexpressing cells. CBX8 promotes HCC cell proliferation through YBX1 mediated cell cycle progression and is related to poor HCC prognoses. Therefore, CBX8 may serve as a potential target for the diagnosis and treatment of HCC.

Interplay between Circadian Clock and Cancer: New Frontiers for Cancer Treatment

Circadian clocks constitute the evolutionary molecular machinery that dictates the temporal regulation of physiology to maintain homeostasis. Disruption of the circadian rhythm plays a key role in tumorigenesis and facilitates the establishment of cancer hallmarks. Conversely, oncogenic processes directly weaken circadian rhythms. Pharmacological modulation of core clock genes is a new approach in cancer therapy. The integration of circadian biology into cancer research offers new options for making cancer treatment more effective, encompassing the prevention, diagnosis, and treatment of this devastating disease. This review highlights the role of the circadian clock in tumorigenesis and cancer hallmarks, and discusses how pharmacological modulation of circadian clock genes can lead to new therapeutic options.

THAP7 promotes cell proliferation by regulating the G1/S phase transition via epigenetically silencing p21 in lung adenocarcinoma

PURPOSE

Lung adenocarcinoma (LUAD) is one of the most common cancers worldwide. The THanatos-Associated Proteins (THAP) family plays an essential role in multiple cancers. However, the role of THAP7 in cancers has remained elusive.

METHODS

THAP7 expression status in LUAD tissues was analysed by using the Oncomine database and qRT-PCR, and its expression level in LUAD cell lines was detected by qRT-PCR and Western blotting. The role of THAP7 in LUAD cells was determined by proliferation, colony formation, and cell cycle analyses. In vivo role of THAP7 was studied on xenograft models. Luciferase reporter assays and chromatin immunoprecipitation (ChIP) were used to determine the activity and acetylation of the p21 promoter.

RESULTS

THAP7 expression was increased in LUAD tissues and cell lines. Moreover, the high expression of THAP7 was correlated with poor prognosis. The overexpression of THAP7 accelerated the G1/S phase transition and promoted tumour growth both in vitro and in vivo. A mechanistic study revealed that THAP7 reduced the acetylation of histone H3 on the p21 promoter to suppress p21 transcription.

CONCLUSION

For the first time, we demonstrated the function of THAP7 in LUAD, and our findings suggested that THAP7 may be a potential molecular therapy target in LUAD.