Circadian Influences on Chemotherapy Efficacy in a Mouse Model of Brain Metastases of Breast Cancer

Prognostic value of circadian rhythm-associated genes in breast cancer

OBJECTIVE

Breast cancer (BC) remains the most prevalent malignancy among women. Clinical evidence indicates that genetic variations related to circadian rhythms, as well as the timing of therapeutic interventions, influence the response to radiation therapy and the toxicity of pharmacological treatments in women with BC. This study aimed to identify key circadian rhythm-related genes (CRGs) using bioinformatics and machine learning, and construct a prognostic model to predict clinical outcomes.

METHODS

Transcriptome data for BC were retrieved from The Cancer Genome Atlas database. Univariate Cox regression and least absolute shrinkage and selection operator regression analyses were used to develop a prognostic model based on CRGs. The predictive performance of the risk score model was evaluated. Univariate and multivariate Cox regression analyses were applied to construct the prognostic model and stratify patients into high-risk and low-risk groups. Additionally, differences in immune microenvironment, immunotherapy efficacy, and tumor mutation burden were assessed between risk groups.

RESULTS

A prognostic risk score model comprising 17 CRGs was developed. The areas under the receiver operating characteristic curve for overall survival at 1, 3, 5, and 7 years exceeded 0.6, indicating acceptable predictive performance. Calibration plots and decision curve analyses demonstrated the use of the model in prognostic prediction. Significant differences in immune microenvironment, immunotherapy efficacy, and tumor mutation burden were identified between the low-risk and high-risk groups.

CONCLUSION

The circadian rhythm-based gene model, effectively predicted the prognosis of individuals with BC, highlighting its potential to inform personalized therapeutic strategies and improve patient outcomes.

Nanoparticles targeting the central circadian clock: Potential applications for neurological disorders

Circadian rhythms and their involvement with various human diseases, including neurological disorders, have become an intense area of research for the development of new pharmacological treatments. The location of the circadian clock machinery in the central nervous system makes it challenging to reach molecular targets at therapeutic concentrations. In addition, a timely administration of the therapeutic agents is necessary to efficiently modulate the circadian clock. Thus, the use of nanoparticles in circadian clock dysfunctions may accelerate their clinical translation by addressing these two key challenges: enhancing brain penetration and/or enabling their formulation in chronodelivery systems. This review describes the implications of the circadian clock in neurological pathologies, reviews potential molecular targets and their modulators and suggests how the use of nanoparticle-based formulations could improve their clinical success. Finally, the potential integration of nanoparticles into chronopharmaceutical drug delivery systems will be described.

The role of cryptochrome (CRY) in cancer: molecular mechanisms and Clock-based therapeutic strategies

The circadian rhythm is a phenomenon in which physiological, behavioral, and biochemical processes within an organism naturally fluctuate over a period of approximately 24 hours. This phenomenon is ubiquitous in living organisms. Disruption of circadian rhythms in mammals leads to different diseases, such as cancer, and neurodegenerative and metabolic disorders. In specific tissues, numerous genes have been found to have circadian oscillations, suggesting a broad role for rhythm genes in the regulation of gene expression. This review systematically summarizes the role of cryptochromes (CRYs) in the initiation and progression of different types of cancer and discusses the relationships between Clock genes and the tumor microenvironment (TME), as well as clock-based therapeutic strategies.

Melatonin Alters Preference to Move Toward Monochromatic Lights in Female Syrian Hamsters: A Behavior Associated With Circadian Rhythm

Different light colors have different effects on endogenous melatonin. The preference for light colors has been studied in various animal species, except hamsters. Additionally, no research has been done on how melatonin affects color preference. In this study, I investigated whether melatonin can influence Syrian hamsters' preferences for various light colors. Eighteen female Syrian hamsters were divided into a control group and a test group orally administered 0.01 mg melatonin daily for 30 days. On Day 31, I placed each hamster in the test box at four stages: dark mid-phase; beginning, middle, and end of day. The box had four areas with red, yellow, green, and blue lamps. In each stage, the hamsters' movements were recorded for 5 min. I tested the effects of color, stage, and melatonin treatment using a mixed model analysis. The preferences of both groups changed between the stages (p < 0.001) with the except stages 1 and 4 of the control group (p = 0.012); and stages 2 and 3 of the test group for the yellow color (p = 0.104). There was a significant difference between the test and the control groups in all stages and all colors (p < 0.001) except the green light color in stage 2 (p = 0.007). The results suggest that exogenous melatonin controls the preference for monochromatic light by an unknown mechanism. Circadian endogenous melatonin levels are also effective. Scientists must consider melatonin levels in studies evaluating responses to light.

Time of day bias for biological sampling in studies of mammary cancer

Despite its demonstrated biological significance, time of day is a broadly overlooked biological variable in preclinical and clinical studies. How time of day affects the influence of peripheral tumors on central (brain) function remains unspecified. Thus, we tested the hypothesis that peripheral mammary cancer tumors alter the transcriptome of immune responses in the brain and that these responses vary based on time of day; we predicted that time of day sampling bias would alter the interpretation of the results. Brain tissues collected at mid dark and mid light from mammary tumor-bearing and vehicle injected mice were analyzed using the Nanostring nCounter immune panel. Peripheral mammary tumors significantly affected expression within the brain of over 100 unique genes of the 770 represented in the panel, and fewer than 25% of these genes were affected similarly across the day. Indeed, between 65 and 75% of GO biological processes represented by the differentially expressed genes were dependent upon time of day of sampling. The implications of time-of-day sampling bias in interpretation of research studies cannot be understated. We encourage considering time of day as a significant biological variable in studies and to appropriately control for it and clearly report time of day in findings.

Chronotherapeutics for Solid Tumors

Circadian rhythms are internal manifestations of the 24-h solar day that allow for synchronization of biological and behavioral processes to the external solar day. This precise regulation of physiology and behavior improves adaptive function and survival. Chronotherapy takes advantage of circadian rhythms in physiological processes to optimize the timing of drug administration to achieve maximal therapeutic efficacy and minimize negative side effects. Chronotherapy for cancer treatment was first demonstrated to be beneficial more than five decades ago and has favorable effects across diverse cancer types. However, implementation of chronotherapy in clinic remains limited. The present review examines the evidence for chronotherapeutic treatment for solid tumors. Specifically, studies examining chrono-chemotherapy, chrono-radiotherapy, and alternative chronotherapeutics (e.g., hormone therapy, TKIs, antiangiogenic therapy, immunotherapy) are discussed. In addition, we propose areas of needed research and identify challenges in the field that remain to be addressed.

The Blood-Brain Barrier: Implications for Experimental Cancer Therapeutics

The blood-brain barrier is critically important for the treatment of both primary and metastatic cancers of the central nervous system (CNS). Clinical outcomes for patients with primary CNS tumors are poor and have not significantly improved in decades. As treatments for patients with extracranial solid tumors improve, the incidence of CNS metastases is on the rise due to suboptimal CNS exposure of otherwise systemically active agents. Despite state-of-the art surgical care and increasingly precise radiation therapy, clinical progress is limited by the ability to deliver an effective dose of a therapeutic agent to all cancerous cells. Given the tremendous heterogeneity of CNS cancers, both across cancer subtypes and within a single tumor, and the range of diverse therapies under investigation, a nuanced examination of CNS drug exposure is needed. With a shared goal, common vocabulary, and interdisciplinary collaboration, the field is poised for renewed progress in the treatment of CNS cancers.

Circadian rhythms in the blood-brain barrier: impact on neurological disorders and stress responses

Circadian disruption has become more prevalent in society due to the increase in shift work, sleep disruption, blue light exposure, and travel via different time zones. The circadian rhythm is a timed transcription-translation feedback loop with positive regulators, BMAL1 and CLOCK, that interact with negative regulators, CRY and PER, to regulate both the central and peripheral clocks. This review highlights the functions of the circadian rhythm, specifically in the blood-brain barrier (BBB), during both healthy and pathological states. The BBB is a highly selective dynamic interface composed of CNS endothelial cells, astrocytes, pericytes, neurons, and microglia that form the neurovascular unit (NVU). Circadian rhythms modulate BBB integrity through regulating oscillations of tight junction proteins, assisting in functions of the NVU, and modulating transporter functions. Circadian disruptions within the BBB have been observed in stress responses and several neurological disorders, including brain metastasis, epilepsy, Alzheimer's disease, and Parkinson's disease. Further understanding of these interactions may facilitate the development of improved treatment options and preventative measures.