Circadian rhythm in gastrointestinal cancer: clinical applications and future perspectives

Abstract

Gastrointestinal cancer (GIC) ranks among the most fatal malignancies globally and is characterized by a significant propensity for metastasis. While surgical intervention can effectively cure GIC in its early stages, a substantial number of cases are diagnosed at advanced stages, where the response to current therapeutic options is markedly diminished. Increasing evidence highlights the pivotal role of circadian rhythm, an intrinsic 24-hour cyclical system regulating biological activities to adapt to the alternations of day and night in the progression, metastasis, and development of chemoresistance in GIC. Recent studies have disclosed that the modulation of key circadian rhythm genes (such as BMAL1 and PER1) can suppress tumor advancement through multiple pathways. This review compiles the most recent research concerning the circadian rhythm and its influence on GIC progression. It elucidates the role of circadian genes in the initiation, metastasis, metabolism, inflammatory response, and therapeutic resistance in GIC, including both chemotherapy and targeted therapies. Furthermore, the review discusses the current implementation and future outlook of therapeutic strategies based on circadian modulation in the treatment of GIC.

1. Introduction

Gastrointestinal cancer (GIC) constitutes a primary contributor to cancer-related deaths globally, presenting a significant challenge to human well-being [1]. Anatomically, GIC encompasses malignancies such as esophageal cancer (ESCA), gastric cancer (GC), colorectal cancer (CRC), hepatocellular carcinoma (HCC), and pancreatic cancer (PAAD). Globally, GICs constitute over a quarter of all cancer cases and account for nearly one-third of cancer-related deaths [2]. Epidemiological studies have demonstrated a notable rise in the incidence of CRC among younger individuals over the past thirty years, with a comparable pattern also evident in gastric, pancreatic, and biliary tract cancers [3,4]. Despite advancements in strategies like immunotherapy, radiotherapy, targeted therapy, and combination therapy, surgery and chemotherapy remain the primary treatment modalities for GIC [5]. Consequently, discovering new therapeutic targets is crucial for improving the clinical prognosis of individuals diagnosed with GIC.

Circadian rhythm is an intrinsic biological mechanism present in living organisms, which is crucial for regulating cellular processes such as DNA damage repair, metabolism, and the cell cycle [6]. An increasing volume of research has demonstrated that circadian rhythm disorders are associated with numerous health complications, encompassing metabolic syndrome, sleep disorders, cognitive impairments, cardiovascular diseases, immune dysfunction, and cancer progression [7–9]. Recent studies underscore the connection between GIC and circadian rhythm disorder. A recent publication from the Japan Collaborative Cohort Study (JACC Study) indicated that exposure to night shift work may elevate the risk of ESCA in Japanese men [10]. Similarly, a case-control study conducted in Spain found that night shift work could increase the likelihood of GIC, particularly following prolonged exposure [11]. Therefore, circadian rhythm modulation might represent a viable therapeutic approach in the management of GIC.

The circadian rhythm, situated within the suprachiasmatic nucleus of the hypothalamus, is vital for maintaining homeostasis through a transcription/translation feedback loop (TTFL). The principal genes involved in this loop include basic helix-loop-helix ARNT like 1 (BMAL1) and circadian locomotor output cycles protein kaput (CLOCK). These genes operate via heterodimerization, forming a transcription factor complex that propels the positive feedback arm of the TTFL. Additional regulators, such as the Cryptochrome (CRY) and Period (PER) gene families, REV-ERB (also known as nuclear receptor subfamily 1 group D member 2, NR1D2), Casein kinases 1ε (CK1ε), retinoic acid receptor-related orphan receptor α (RORA), and TIMELESS (TIM), contribute to the modulation of TTFL at multiple levels [12,13](Figure 1). Importantly, alterations in circadian rhythm by modulating these core genes can influence the progression of GI cancer. Studies have demonstrated that metformin-based chronotherapy may interfere with circadian rhythm by targeting the BMAL1-CLOCK-PER1-HK2 axis, thereby reversing trastuzumab resistance in HER2-positive GC resistant to trastuzumab [14]. Moreover, alterations in the expression of PERs, CLOCK, TIM, and CRY genes have been frequently correlated with the development of obesity-related cancers, including CRC [15]. Despite the documented associations between circadian rhythm disorder and GIC in both in vitro and in vivo studies, the integration of circadian rhythm into GIC therapeutic strategies remains limited.

Figure 1.

The regulation of transcriptional–translational feedback loop. CLOCK and BMAL1 bind to the E-box elements on the promoter of clock controlled genes (CCGs) and activate the expression of downstream genes such as PERs, CRYs, RORs and REVERBs.

This review provides a synthesis of the most recent research, aiming to elucidate the influence of circadian rhythm on GIC progression, including its roles in initiation, metastasis, and chemoresistance. Furthermore, current therapeutic strategies that incorporate circadian rhythm in the management of GIC are examined, with the intention of offering new perspectives on GIC treatment.

2. Can circadian rhythm impact GIC development?

2.1. Clinical studies of circadian rhythm in GIC

The International Agency for Research on Cancer has classified shift work that involves circadian disorder as a probable human carcinogen (Class 2 A). Moreover, evidence indicates that 25% of shift workers experience excessive sleepiness or notable insomnia symptoms, conditions identified as clinical disorders that impair daytime functioning [16]. Circadian or clock genes are essential in the regulation of daily rhythmic cellular functions, including metabolism and DNA repair processes. The disorder of these rhythms may result in uncontrolled cell proliferation, thereby facilitating the initiation and progression of GIC.

Two German cohort studies involving 6,903 participants indicated that there is no significant association between night-shift work and CRC (incidence rate ratios: 1.03, 95% CI: 0.62–1.71). However, it was observed that rotating shift work markedly increased the risk of CRC (incidence rate ratio, IRR = 1.45 [95% confidence interval, CI: 0.72–2.92]), particularly with prolonged exposure (IRR: 1.79, 95% CI: 0.81; 3.92) [17]. Similarly, a case-control study conducted in Spain reported comparable findings, showing that relative to day workers, individuals engaged in rotating shift work exhibited a heightened risk for CRC [odds ratio, OR 1.22, 95% CI 1.04–1.43], with the odds ratio escalating alongside the cumulative duration of rotating shift work [11](Table 1). Additional studies further emphasize the critical impact of rotating shift work on CRC progression. They revealed that engaging in rotating night shifts for periods exceeding 10 and 15 years, respectively, may result in an elevated CRC risk among women [18,19]. Moreover, a meta-analysis encompassing six studies not only validated the connection between night shift work and an elevated risk of CRC [OR = 1.318, 95%CI: 1.121–1.551] but also highlighted a dose-response relationship, demonstrating that each five-year increment in night shift work correlates with an 11% rise in CRC risk [OR = 1.11, 95% CI: 1.03–1.20] [20].

Table 1.

Studies exploring the association between circadian rhythm and GIC.

Cancer types	Outcomes	Research method	Author, year
Colorectal cancer	No evidence of an association between rotating night shift work and colorectal cancer, but long-term circadian disorder could increase the risk of rectal cancer.	Prospective study	Papantoniou, 2018
	Night shift work for more than 10 years was associated with increased colorectal cancer risk	Prospective	Barber, 2023
	Rotating night shift at least three nights per month for 15 or more years may increase the risk of colorectal cancer in women	Prospective study	Schernhammer, 2003
	Working for more than 15 years of night shifts may had an increased overall risk of colorectal cancer for women with abnormal insulin receptor pathways	Prospective study	Shi, 2020
	Rotating shift work may increase the risk of colorectal cancer, especially after long-term exposures	Retrospective study	Papantoniou, 2017
	Frequent and long daytime naps increased the risk of colorectal, and the association was stronger among participants with night shift-work history	Retrospective study	Papantoniou, 2021
	Night-shift work was not associated with CRC, but rotating shift work significantly increased the CRC risk	Prospective study	Wichert, 2020
	Night shift work was associated with an increased risk of colorectal cancer	Meta-analysis	Wang, 2015
	Both extreme short and long sleep durations were associated with a moderate increase in the risk of CRC in postmenopausal women	Prospective study	Jiao, 2013
	Outdoor blue light spectrum exposure may increase the risk of colorectal cancer	Retrospective study	Garcia-Saenz, 2020
	No association	Meta-analysis	Wang, 2022
	No association	Retrospective study	Walasa, 2018
	No association	Meta-analysis	Dun, 2020
Gastric cancer	Frequent and long daytime naps increased the risk of gastric cancer, and the association was stronger among participants with night shift-work history	Retrospective study	Papantoniou, 2021
	Sleep duration of ≥9 h was associated with gastric cancer	Retrospective study	Collatuzzo, 2023
	No association	Retrospective study	Gyarmati, 2016
	No association	Meta-analysis	Dun, 2020
Esophageal cancer	Rotating shift work might contribute to the increased risk of esophageal cancer	Prospective study	Arafa, 2021
	Unhealthy sleep behaviors were associated with an increased risk of esophageal cancer, independent of genetic risk	Prospective study	Wang, 2023
	Short sleep duration (<7h) and regular snoring were significantly related to increased risk of esophageal squamous cell carcinoma independently	Retrospective study	Chen, 2019
Liver cancer	Rotating shift work might contribute to the decreased risk of liver cancer	Prospective study	Arafa, 2021
	U-shaped associations of nighttime sleep duration with the incidence of HCC, and daytime napping was associated with higher risk of HCC	Prospective study	Long, 2023
Pancreatic cancer	No association	Meta-analysis	Dun, 2020

Concerning other types of cancer, findings from the Japan Collaborative Cohort underscored that rotating shift work was markedly linked to a heightened risk of ESCA [hazard ratio, HR = 2.47, 95% CI, 1.42–4.31] and a reduced risk of liver cancer [HR = 0.54, 95% CI, 0.30–0.98] [10]. Conversely, some studies have presented contradictory results. For instance, research from Spain reported no association between a history of rotating night shifts (OR = 0.9, 95% CI 0.6–1.2) and the risk of GC, nor any correlation with the cumulative duration of such shifts (p = 0.68) [21]. Likewise, researchers in Australia did not identify evidence supporting an increased CRC risk among workers engaged in shift work for over 7.5 years [adjusted OR = 0.95, 95% CI 0.57–1.58] [22]. Furthermore, two meta-analyses were conducted to investigate whether exposure to night-shift work could elevate the risk of various cancers. These analyses found no supporting evidence for a link with pancreatic, colorectal, or GCs [23,24](Table 1).

More importantly, circadian disorder – induced by both excessively long (≥9 h) and short (5 < h) sleep durations – has been linked to an elevated risk of HCC [HR_{< 5 vs. 7–8 h} = 2.00, 95% CI: 1.22–3.26 and HR_{≥ 9 vs. 7–8 h} = 1.63, 95% CI: 1.04 − 2.65] [25]. A study conducted in the USA reported comparable findings regarding CRC in postmenopausal women, with HRs of 1.47 (95% CI: 1.10–1.96) and 1.36 (95% CI: 1.06 − 1.74) for long (≥9 h) and short (≤5 h) sleep durations, respectively [26]. Furthermore, unhealthy sleep patterns, such as insufficient sleep (<7 h), excessive sleep (>9 h), daytime sleepiness, and daytime napping, have been associated with a heightened likelihood of developing ESCA [27,28].

Although various pieces of evidence support the aforementioned observation, some conflicting findings have not reached a consensus among scientists on whether disorder of the circadian rhythm contributes to a higher incidence of GIC. Therefore, additional multi-center clinical trials are required to substantiate this conclusion in the future.

2.2. Circadian rhythm and GIC risk factors

To investigate why people with disrupted circadian rhythm are more likely to develop GIC, we summarized the relationship between circadian rhythm and risk factors for tumorigenesis. Although different gastrointestinal tumors have diverse risk factors, we found obesity and unhealthy eating patterns play a vital role in these cancers. In 2019, convincing evidences demonstrated that obesity was associated with an increasing risk for at least 13 solid tumors, including esophageal cancer, gastric cancer, colorectal cancer, pancreatic adenocarcinomas and hepatocellular carcinoma [1]. Insulin resistance, chronic inflammation, changes in the tumor microenvironment and gut microbiota may be the underlying mechanism linking obesity to GIC development [2]. The traditional view holds that excessive energy intake and lack of exercise are the main causes of obesity. However, recent discoveries have revealed circadian rhythm disorder as a critical and independent risk factor in the pathogenesis of obesity among contemporary populations [3]. Energy metabolism is a complex system controlled by many components, which expression are influenced by day-and-night cycle. Several studies investigated the relationship between energy expenditure and circadian rhythm. They found that insufficient night-time sleep significantly increased 24-h energy expenditure about 100 kcal per day in healthy adults [4–6]. However, another study demonstrated that healthy adults have reduced energy expenditure after experiencing a period of shift work (sleep during the daytime and work at night) [7]. This may explain the increased risk of GIC in shift works.

In addition to energy expenditure, uncontrolled energy intake is also the cause of obesity induced by circadian rhythm disorder. Current studies revealed that leptin, ghrelin and peptide-YY, three main appetite-regulating hormones, are influenced by sleep and day-and-night cycle. The circulating levels of ghrelin and peptide-YY showed higher levels during the daytime and lower levels at night during the day, while leptin showed lower levels during the daytime and higher levels at night [8–9]. This timely expression of appetite hormones maintains a stable appetite in normal people. However, circadian rhythm disorder break this balance and resulted in an increase in energy intake of 253 and 385 calories per day in normal and obesity people, respectively [10,11]. Besides, it was found that shift workers tend to choose unhealthy food, such as less fresh vegetables and more sweets and saturated fats [12,13]. This may be another mechanism by which circadian rhythm disorder increases the risk of obesity (Figure 2).

Figure 2.

Differences between disorder and balanced circadian rhythm.

To date, evidence indicated that circadian rhythm disorder may improve the development of GIC by increasing the risk of obesity. Experimental and clinical studies are needed to investigate the association between circadian rhythm and other risk factors to better understand the role of circadian rhythm in carcinogenesis.

3. The novel functions of circadian rhythm in GIC development

Circadian genes are integral to sustaining a fundamental time-keeping mechanism within various organisms, thereby influencing their behaviors. Studies have previously demonstrated that alterations in circadian gene expression may result in the dysfunction of cellular mechanisms, such as the cell cycle, metabolic pathways, and DNA damage repair [29]. Clinical evidence suggests that disorder of circadian rhythms could represent a potential risk factor for GIC, primarily due to the dysregulated expression of circadian genes like CLOCK, BMAL1, PERs, TIM, and REV-ERBs. These genes, when dysregulated, exert significant effects on cellular proliferation, invasion, metabolism, and tumor immunity, thereby facilitating the progression of GIC.

3.1. Tumor initiation

A Canadian study illustrated the essential function of BMAL1 in the initiation of CRC [30]. The findings indicated that the loss of BMAL1, which causes circadian disorder, markedly facilitated tumor initiation within the intestine and disrupted tissue homeostasis. Mechanistically, RNA sequencing identified that transcripts regulated by the circadian clock are implicated in the regeneration and signaling of intestinal stem cells. The absence of BMAL1 was shown to enhance the self-renewal capacity of epithelial cells in a manner dependent on Yes-associated protein 1 (Hippo signaling), thereby contributing to an increased onset of CRC. Abnormal eating patterns, such as consuming large meals during physiological rest periods or eating late at night, have become increasingly prevalent worldwide [31,32]. However, these eating behaviors, which markedly disrupt circadian rhythms, might contribute to various health issues [33]. It has been demonstrated that irregular eating schedules, in conjunction with alcohol consumption, promote colon tumorigenesis [34]. This effect is mediated through circadian rhythm disorder by altering the phase of the colon rhythm and diminishing the levels of short-chain fatty acid-producing bacteria and butyrate, thereby leading to a pro-inflammatory state. Moreover, the expression of TIM was found to be notably elevated in CRC specimens relative to normal tissues and was closely linked with poor prognosis [35]. At the molecular level, TIM was activated by H3k27 acetylation, which subsequently enhanced proliferation and tumor growth both in vivo and in vitro by binding to Myosin-9.

Recent evidence has also suggested a correlation between liver cancer and circadian genes. Unrestricted proliferation is a fundamental hallmark of cancer. BMAL1 and CLOCK, the core transcription factors of circadian rhythm, have been recognized as crucial players in cell proliferation in HCC [36]. Specifically, the knockdown of BMAL1/CLOCK in HCC cells resulted in the activation of apoptosis and arrest of the cell cycle at the G2/M phase through the downregulation of Wee1 and upregulation of p21, respectively. This discovery provides insight into the cellular mechanisms by which clock genes may promote HCC carcinogenesis. A team of researchers in the USA found that the overexpression of BMAL1 in HNF4α-positive HCC suppressed tumor growth in mice [37]. Subsequently, they demonstrated that the simultaneous loss of both HNF4α and BMAL1 reduces HCC incidence in high-fat diet (HFD)-induced HCC models, with RNA-seq analysis revealing several pathways potentially involved in this reduction, including WNT and P53 pathways, fatty acid metabolism, and inflammation [38].

However, evidences in other types of GIC are insufficient to support a strong correlation between circadian rhythm and tumorigenesis. For example, a related study reported that H. pylori infection transcriptionally activates LIN28A and induces BMAL1 expression [39]. BMAL1, in turn, acts as a transcription factor that amplifies the production of the pro-inflammatory cytokine TNF-α, thus fostering inflammation in gastric epithelial cells. Nevertheless, this investigation failed to establish a clear link between BMAL1 expression and gastric carcinogenesis. Future studies should investigate the role of circadian rhythm in tumorigenesis of other types of GIC.

3.2. Metastasis

Metastasis represents a significant characteristic of cancers, often associated with poor prognosis. Within the tumor microenvironment (TME), cancer-associated fibroblasts (CAFs) interact with tumor cells and act as a facilitating factor in various metastatic processes, ranging from intravasation into the circulation to regrowth in distant tissues [40,41]. In CRC, BMAL1 is implicated not only in enhancing tumor initiation but also in influencing tumor metastasis. It has been demonstrated to induce an exacerbated fibrotic phenotype in several cancers and to promote tumor metastasis in CRC in BMAL1−/− mice models [42]. The deletion of BMAL1 was found to suppress the expression of the targeted plasminogen activator inhibitor-1 (PAI-1), subsequently activating plasmin and downstream transforming growth factor β (TGF-β). The activation of TGF-β facilitated tumor fibrosis and the transformation of CAFs into myoCAFs, ultimately contributing to enhanced tumor metastasis. In breast cancer (BC), the overexpression of BMAL1 was observed to markedly enhance migration and invasion through the upregulation of matrix metalloproteinase9 expression [43]. It is well recognized that the host stromal cells surrounding the tumor, referred to as the TME, are critical for facilitating tumor metastasis. PER2, rather than PER1, was shown to function as a key factor in the liver metastasis of colon cancer because the loss of PER2 in the TME led to significant transcriptional alterations that may create a tumor-suppressive microenvironment [44]. Tumor angiogenesis is a vital process in supplying energy and pathways for the proliferation and metastasis of malignant tumors. Evidence demonstrated that CLOCK promotes angiogenesis both in vitro and in vivo by regulating the HIFα/β-VEGFα pathway, leading to enhanced migration and invasion of CRC cells [45]. The epithelial-mesenchymal transition (EMT) is fundamental to embryonic development and tissue repair, contributing to organ fibrosis and tumor metastasis. This transcriptional program is regulated by various signaling pathways, encompassing Wnt–β-catenin, TGF-β, Hedgehog, Notch, and receptor tyrosine kinases. Both TIM and PER2 have been reported to influence tumor growth and metastasis by modulating EMT, with TIM positively regulating EMT and PER2 negatively regulating EMT [35,46]. This variability may be attributed to the heterogeneity of different cancers, and additional investigations are required to clarify BMAL1’s function in GIC metastasis.

There are also several studies that revealed the association between circadian rhythm and tumor metastasis. One research indicated that the downregulation of BMAL1 enhanced HCC growth and metastasis by promoting GPAM-regulated lipid biosynthesis [47], while several other studies have reported contrary findings. A report from China observed that increased BMAL1 expression was markedly linked to unfavorable outcomes in CRC and promoted cell migration and invasion via ERK- and JNK-dependent c-Myc expression [48]. A single-center study highlighted the potential role of NPAS2, a significant regulator within the TTFL, in predicting the prognosis of GC. The study found that elevated expression of NPAS2 was markedly linked to tumor-node-metastasis (TNM) stage (p < 0.05), venous invasion (p < 0.05), metastasis (p < 0.05), lymph node positivity (p < 0.05), lymphatic invasion (p < 0.05) in GC, and a lower 3-year overall survival (OS) rate (p < 0.0001) [49].

3.3. Metabolism

Enhanced glycolysis, recognized as a prominent hallmark of cancers, has been identified as a crucial mechanism by which CRC cells meet the increasing biosynthetic demands required for proliferation and angiogenesis [50]. A recent study revealed that BMAL1 is capable of promoting colorectal tumorigenesis both in vivo and in an intestinal organoid model [51]. The isolated intestinal crypts from BMAL1-knockout mice exhibit a tumor-like transformation driven by the loss of heterozygosity of Apc, leading to the activation of Wnt signaling. Consequently, this activation of Wnt signaling markedly enhances glycolysis through the upregulation of c-Myc. Interestingly, five genes related to glycolysis – ALDH3A2, ALDOC, HKDC1, PCK2, and PDHB – were found to display distinct mRNA expression patterns between SW480 and SW620 cell lines. It has been demonstrated that BMAL1 disorder leads to time-dependent metabolic shifts, notably enhanced glycolytic activity, and alters treatment responses through hexokinase domain containing 1 (HKDC1) expression [52]. The enzyme 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) is crucial for glycolysis. Studies indicate that inhibiting PFKFB3 with (E)-1-(pyridin-4-yl)-3-(quinolin-2-yl)prop-2-en-1-one (PFK15) can hinder proliferation and trigger apoptosis in the DLD1 human colon cancer cell line. In vivo, a reduction in tumor size was observed in the group treated with PFK15 in the morning but not in the evening-treated group, suggesting that this glycolytic process is regulated by circadian rhythms [53].

In liver cancer, lipid metabolism has attracted increasing attention due to its significant role in tumor initiation and metastasis, thereby representing a promising target for cancer treatment. Lipid metabolism is regulated by numerous signaling pathways, among which SREBPs, PPARα/γ, FASN, and SCD1 are the primary regulators. Recent evidence has demonstrated the interaction between lipid metabolism and circadian genes, suggesting a novel mechanism for cancer research. Chronic circadian disorder has been reported to induce spontaneous hepatocarcinogenesis in vivo [54]. This disorder was found to alter general metabolic patterns, including enhanced lipid synthesis and storage, increased cytoplasmic glycolysis, and elevated oxidative stress. Mechanistically, these metabolic changes facilitate the progression from non-alcoholic fatty liver disease (NAFLD) to HCC, a process that closely resembles human pathology. REV-ERBα, a core transcriptional regulator of the circadian clock, has been implicated in various biological processes, particularly glucose and lipid metabolism [55,56]. The simultaneous depletion of REV-ERBα and β in mice markedly disrupted the circadian clock and altered the overall expression of circadian genes [57]. Notably, tamoxifen-treated double knockout mice exhibited increased circulating glucose and triglyceride levels and decreased free fatty acid levels compared to the control group. The reduction in fatty acids may indicate a shift toward more oxidative metabolism in these double knockout mice. REV-ERBα assumes a crucial function in governing sterol regulatory element-binding protein (SREBP) expression in the liver by modulating the transcription of Insig2, resulting in downstream effects on cholesterol and lipid metabolism [58]. Agonists targeting REV-ERB have been developed and tested in vivo, demonstrating that upregulation of REV-ERB alters the expression of metabolic genes in the liver, skeletal muscle, and adipose tissue [59]. Furthermore, the administration of REV-ERB agonists induced weight loss and reduced plasma lipid levels in diet-induced obese mice, underscoring the potential role of REV-ERB in treating metabolic diseases. Additionally, REV-ERBα has also been reported to influence lipid absorption and export in intestinal epithelial cells via the Nfil3 (E4BP4) and HDAC3 pathways [60,61].

Although a range of evidence has investigated the association among circadian genes, metabolic patterns, and tumor development, the underlying mechanisms that connect these factors remain inadequately defined. Future research should aim to elucidate how these alterations influence tumor behavior and progression.

3.4. Inflammation

Inflammation has been acknowledged as a significant contributor to cancer development due to its genotoxic effects and the cellular damage caused by the substances it releases [62]. The dysfunction of inflammatory processes promotes tumor progression by enhancing cell proliferation, angiogenesis, and invasion. NF-κB, a key pro-inflammatory transcription factor, has been demonstrated to serve an essential function in the connection between circadian rhythm and inflammation. Activation of NF-κB due to inflammation markedly inhibited clock genes such as PER and REV-ERB, underscoring the pivotal role of NF-κB in linking circadian disorder to inflammatory responses [63]. Dysregulation of BMAL1 increased the sensitivity of H. pylori infection-induced inflammatory responses in a mouse model with rhythm disorders [39]. A recent study has elucidated the mechanism by which NF-κB regulates the circadian clock [64]. Specifically, the NF-κB subunit RELA was found to compete with CRY1 and coactivator CBP/p300, interacting with the transactivation domain of BMAL1, thereby suppressing BMAL1 activity. Additionally, REV-ERB also contributed to circadian behaviors in response to inflammation. An NF-κB-driven lncRNA (Lnc-UC) reduced mice’s sensitivity to colitis by transcriptionally activating the circadian clock gene REV-ERBα [65]. IL-1β, a key inflammatory cytokine, regulated the expression of core circadian genes PER2 and BMAL1 in primary human chondrocytes through the NF-κB signaling pathway [66]. Although initial studies have investigated the relationship between circadian disorder and inflammation in orthotopic BC, there remains a lack of consensus on their combined impact on GIC progression.

Th17 cells and innate lymphoid cells play a pivotal role in inflammation. Current studies indicated that these immune cells are regulated by circadian rhythm. Melatonin, a core hormone in circadian rhythm, was reported to reduce ocular inflammation in EAU mice by inhibiting Th17 transcription[14]. Another study found that eating at unnormal time (circadian disorder) combined with alcohol intake to induce inflammation of the colon through increasing T-helper cell 17/regulatory T cell ratio, which promoted colon carcinogenesis[15]. Additionally, core circadian genes were found to highly expressed in intestinal group 3 innate lymphoid cells (ILC3s) with a regular circadian oscillations[16]. REV-ERBα knockout impaired the NKp46⁺ ILC3 subset and IL-22 production in mouse model. Several high-impact researches also reported the vital role of circadian rhythm in modulating ILC3s and gut homeostasis [17–19]. Thus, further studies are urgently needed to investigate the molecular mechanism by which circadian rhythm regulates ILCs and T-helper 17 cells in tumorigenesis.

3.5. Chemotherapy and target therapy

Currently, surgery and chemotherapy are the predominant treatments for GIC. An increasing amount of evidence has demonstrated the link between circadian genes and chemotherapy sensitivity in GIC. A genome-wide CRISPR screening was conducted to elucidate possible genes or molecular pathways associated with 5-FU treatment, which highlighted pyrimidine metabolic genes such as UPP2, UCK2, and UMPS [67]. Additionally, BMAL1 has been identified as a key regulator of pyrimidine metabolism by binding to the E-box element in the promoter region of core genes, thereby enhancing the effectiveness of 5-FU in CRC treatment. BMAL1 notably induced G2-M phase arrest through the ATM pathway, suppressed CRC cell proliferation, and increased oxaliplatin-based chemosensitivity in both in vitro studies and mouse models [68]. BMAL1 exerts its effects by binding to the VEGFA gene promoter and enhancing VEGFA transcription, thereby diminishing the sensitivity of CRC to Bevacizumab. Overexpression of Cryptochrome 2 (CRY2) has been associated with chemoresistance in CRC, while a novel E3 ubiquitin ligase, FBXW7, was found to downregulate CRY2 expression and reverse chemoresistance in CRC cells [69]. The downregulation of BMAL1 expression was observed to reduce DNA damage induced by Cisplatin in murine colon cancer cells (CT26) [70]. A recent study indicated that the depletion of BMAL1 markedly increased the sensitivity of adrenocortical carcinoma (ACC) to chemotherapy via the BMAL1-CLOCK-H4Ac axis, offering a novel insight into GIC therapeutics [71].

PER family has been reported to be involved in the response of other tumors to chemotherapy and targeted therapy drugs. Trastuzumab, which serves as a first-line treatment for HER2-positive advanced GC, faces limitations due to a high rate of resistance. A study demonstrated that knockout of PER1 disrupted the circadian rhythm of glycolysis and reversed resistance to trastuzumab in trastuzumab-resistant GC cells [14]. Moreover, metformin markedly enhanced the sensitivity of GC to trastuzumab therapy by inhibiting glycolysis and PER1. Upregulation of PER2 was shown to reduce cellular proliferation and work synergistically with Cisplatin to induce apoptotic cell death in human PAAD cells; conversely, low expression of PER2 was correlated with increased sensitivity to Cisplatin in mouse esophageal squamous cell carcinoma [72,73]. PER2-mutant (PER2^m/m) mice exhibited resistance to several chemotherapy drugs due to the upregulation of the aldehyde dehydrogenase 3a1 (Aldh3a1) gene, while silencing Aldh3a1 expression reversed the chemoresistance of the PER2^m/m cells [74].

Clinical evidences indicated that among patients receiving FOLFOX or XELOX as their initial chemotherapy regimens, those with high BMAL1 expression were associated with a better prognosis compared to those with low BMAL1 expression. However, another study discovered that high BMAL1 expression was linked to clinical non-response to combination chemotherapy with Bevacizumab (p = 0.0061) and a reduction in progression-free survival (PFS) [*p = 0.0223, HR = 1.69] [75]. A study developed a circadian clock-related prognostic signature for PAAD and evaluated drug response to related targeted therapy. The findings indicated that Sabutoclax, Foretinib, BMS-536924, and Linsitinib were more effective in the low-risk group, whereas Erlotinib showed higher sensitivity in the high-risk group, thereby supporting the future use of circadian rhythm-based therapeutic strategies in PAAD [76]. Consequently, a novel approach called chronotherapy has been introduced to the treatment of GIC, which will be discussed further below.

4. Circadian rhythm in combination therapy

4.1. Chronotherapy

Chronotherapy represents an innovative approach to cancer treatment that is predicated on the circadian rhythm of biological activities within cancer cells. Chemotherapeutic agents are administered at specific times to maximize anti-cancer efficacy while minimizing adverse effects [77]. Several multi-center randomized controlled trials have validated the clinical relevance of chronotherapy principles in GIC. One clinical study compared two methods of drug administration (chrono-infusion aligned with the circadian rhythm and constant-rate infusion) involving oxaliplatin, fluorouracil, and folinic acid for the treatment of metastatic CRC. As anticipated, the chrono-infusion group demonstrated a higher objective response rate (51% vs. 29%, p = 0.003), a reduced rate of severe mucosal toxicity (14% vs. 76%, p < 0.0001), and a lower incidence of functional impairment due to peripheral sensory neuropathy (16% vs. 31%, p < 0.01) compared to the constant-rate infusion group [78]. However, the median survival times and 3-year overall survival rates were comparable between the two groups (15.9 vs. 16.9 months and 22% vs. 21%, respectively), which has limited the broader application of chronotherapy in clinical practice. Nevertheless, recent clinical trials have reported more favorable outcomes in CRC patients. Results from the international EORTC 05011 Trial indicated that patients with metastatic CRC experienced improved objective response rates, OS, and PFS when treated with circadian-based administration (chronoIFLO5) of irinotecan, oxaliplatin, and fluorouracil as either first- or second-line therapy [79].

Furthermore, research has indicated that gender can affect the efficacy of chronotherapy. A meta-analysis comparing the survival outcomes of patients receiving either chronomodulated (chronoFLO) or conventional (CONV) infusion of 5-fluorouracil, leucovorin, and oxaliplatin indicated that males had a longer overall survival with chronoFLO compared to CONV (p = 0.009), whereas females exhibited shorter overall survival (p = 0.012) [80]. Another clinical trial demonstrated that administering irinotecan in the morning to male patients and in the afternoon to female patients resulted in improved efficacy and reduced adverse events [81]. This variation can be partially explained by differences in the expression of circadian genes and alterations in pharmacokinetics between males and females.

The precise mechanisms through which circadian rhythms influence the effectiveness of chemotherapy remain unclear, although the expression of clock genes may contribute to this phenomenon. For example, the DNA alkylating agent temozolomide and the topoisomerase I inhibitor irinotecan exhibit minimal toxicity in CRC when BMAL1 expression is at its lowest [82]. In contrast, elevated BMAL1 expression has been associated with enhanced sensitivity to oxaliplatin [68]. Therefore, future research should concentrate on clock genes such as BMAL1 to optimize drug efficacy while minimizing side effects.

Furthermore, other treatments may also benefit from this chronomodulated approach (Figure 3). Although evidence regarding chronomodulated radiotherapy in GIC is limited and often inconsistent, this field continues to attract increasing attention [83]. It has been demonstrated that the radiosensitivity of cancer cells fluctuates at different times of the day [84]. A clinical trial involving patients with locally advanced rectal cancer indicated that those who received radiotherapy after 12:00 pm showed a better pathological response (p = 0.035) [85]. Another study using a mouse model confirmed that timing plays a significant role in enhancing the efficacy of radiotherapy and reducing the toxic side effects of HCC [86]. The primary limitation of these studies is that most are retrospective and involve a small number of cases. In addition, many patients underwent other anti-cancer therapies, such as chemotherapy, during these studies, which could potentially compromise the accuracy of the results. Thus, chrono-radiotherapy remains an underexplored yet important topic that warrants further investigation.

Figure 3.

The roles of circadian rhythm in gastrointestinal cancer development and treatment. Circadian rhythm is involved in GIC initiation, metastasis, metabolism, inflammation and therapy. Circadian-related therapies synergize with current methods (chemotherapy, radiotherapy and even immunotherapy) to enhance their effectiveness.

However, several challenges hinder the implementation of chronotherapy. The aforementioned evidence has demonstrated the significance of chronotherapy in enhancing the therapeutic efficacy of CRC, but there are limited studies on its application in other types of GIC. Given the crucial role of circadian rhythms in the biological behaviors of GIC, further extensive research is warranted in this domain. Additionally, because each individual, and even each organ, exhibits distinct rhythmic characteristics, personalized therapy should be tailored according to an individual’s circadian rhythm. Recently, a model of irinotecan cellular pharmacokinetics was developed, which has shown effectiveness in predicting treatment toxicity in CRC [87]. In the future, more models evaluating optimal drug administration timing based on a patient’s gene expression profile could be utilized to support personalized treatment strategies.

4.2. Melatonin

Melatonin, a versatile hormone synthesized by the pineal gland and other organs, is essential for the regulation of circadian rhythms, enabling adaptation to the cycles of light and darkness [88]. A growing body of evidence has indicated that melatonin can suppress tumor progression through multiple mechanisms, either by directly influencing tumor cell functions or by indirectly enhancing the sensitivity of tumor cells to chemotherapy [89]. Given that the majority of studies in recent years have been experimental in nature and lack substantial clinical validation, the subsequent sections will outline the latest discoveries regarding the role of melatonin in tumor development and provide suggestions for its clinical application.

Melatonin has the ability to induce both apoptosis and autophagy, and these two processes are primarily responsible for its effects on tumor development. It has been reported that melatonin inhibits the proliferation of CRC cells and triggers apoptosis by upregulating the expression of the miR-34a/449a cluster [90]. The application of melatonin notably lowered the IC50 value of 5-fluorouracil (5-FU) from 100 μM to 50 μM in the SW480 cell line [91]. Furthermore, it works synergistically with 5-FU to promote apoptosis by elevating intracellular ROS levels and reducing antioxidant enzyme activities. Andrographis, a natural compound, is known for its anti-carcinogenic properties. A combination therapy of melatonin and andrographis demonstrated synergistic anti-tumor effects both in vivo and in vitro. RNA-sequencing analysis suggested that the autophagy pathway might contribute to this synergistic effect [92]. Agomelatine, a naphthalene analogue derived from melatonin, exhibits a higher affinity for MT1/MT2 receptors compared to melatonin. Interestingly, research has indicated that agomelatine exerts a more substantial inhibitory effect on HCT-116 and HCT-116 p53-null cell lines than melatonin, and only agomelatine was capable of suppressing tumor growth generated by HCT-116 p53-null cells in vivo [93]. This characteristic is partially attributed to differences in clock gene regulation.

CAFs interact with cancer cells within the TME, which is pivotal in the progression of tumors. Research has demonstrated that CAFs can promote the proliferation, migration, and invasion of GC cells, effects that can be reversed by the administration of melatonin [94]. Mechanistically, melatonin was found to inhibit the expression of MMP2 and MMP9 in CAFs, leading to cell cycle arrest. The deactivation of CAFs hinders GC growth by blocking the NF-κB signaling pathway. These findings provide novel insights into the relationship between melatonin and the TME, suggesting a potential role for melatonin in strategies for GC treatment. Moreover, studies have also shown that melatonin has encouraging anti-cancer effects in GC when used in conjunction with Cisplatin and 5-fluorouracil [95,96]. Several studies have also indicated that melatonin is extensively involved in regulating antioxidant activity, cell cycle arrest, apoptosis, and autophagy, which are also critical in other GICs, both in vivo and in vitro [97–99].

As previously mentioned, clinical evidence supporting the use of melatonin in the treatment of GIC remains scarce. A clinical trial conducted among CRC patients indicated that individuals aged 60 years and older who used melatonin had a lower risk of developing CRC compared to those who did not use melatonin [100]. Additionally, a prospective clinical study in Japan identified a negative association between melatonin intake and the risk of liver cancer [101]. These findings suggest that melatonin consumption may play a role in cancer prevention rather than in direct treatment. Nevertheless, this intriguing observation requires further validation through future research. Two studies have examined the prognostic significance of melatonin receptors in GIC. Wang et al. evaluated the relationship between the expression of melatonin receptor type 1 (MT1) and the prognosis of gastric adenocarcinoma (RGA). Their findings demonstrated that high MT1 expression was correlated with a lower survival rate (p = 0.002), an increased metastasis rate (p = 0.004), and a reduced median overall survival (p = 0.02) in comparison to low MT1 expression [102]. Data from a Taiwan cohort indicated that all single-nucleotide polymorphisms (SNPs) of melatonin receptor 1B (MTNR1B) were linked to a decrease in 5-year OS. Furthermore, MTNR1B SNPs, when combined with the methylation status of CDKN2A and MGMT genes, may serve as a potential prognostic tool for CRC [103].

Although melatonin has been shown to markedly inhibit tumor growth both in vitro and in mouse models, clinical evidence from studies on other cancers suggests that it is more beneficial when used in combination with existing therapies (such as chemotherapy, radiotherapy, and immunotherapy) rather than as a standalone treatment. Moreover, melatonin is a multifunctional hormone that exerts a broad spectrum of effects on various organs. Future research should focus on elucidating the mechanisms through which melatonin enhances the sensitivity of tumor cells to anti-cancer agents and determine the optimal dosage and potential side effects of melatonin.

5. Conclusions and perspectives

The circadian rhythm is fundamentally important in the development of GIC, encompassing processes such as initiation, metastasis, metabolism, and inflammation. Core clock genes, including BMAL1, RORA, and PER, exhibit differential expression between tumorous and normal tissues and have been demonstrated to play a role in cancer treatment. Despite significant advancements in incorporating circadian rhythm into GIC therapies, such as in combination with chronotherapy and melatonin, the clinical application remains constrained. There is a necessity for extensive validation to determine the efficacy of circadian rhythms in augmenting current cancer treatment strategies.

Infiltrating immune cells are critical determinants in regulating tumor growth and modulating the response to immunotherapy, including in GIC. In glioblastoma (GBM) mouse models, the suppression of the CLOCK-OLFML3-HIF1α-LGMN-CD162 axis has been shown to increase CD⁸⁺ T-cell infiltration, activation and cytotoxicity, thereby enhancing the efficacy of anti-PD-1 therapy [104]. Research by Wang et al. demonstrated that leukocyte infiltration within tumors follows circadian oscillations, with a peak in leukocyte infiltration occurring in the evening [105]. Regarding T lymphocytes, CD⁸⁺ T cells displayed an immunosuppressive phenotype in the morning and exhibited an anti-tumor profile in the evening. In a mouse colon carcinoma model (MC38), anti-PD-1 therapy was found to markedly suppress tumor growth when administered in the evening compared to the morning. Conversely, another study reported elevated CD8 T cell activation markers and associated signaling pathways, such as IRF4, mTOR, and AKT, following a vaccine injection during the day as opposed to the night, suggesting a more effective CD8 T cell response to antigen presentation by dendritic cells (DCs) [106]. PER2 interacts with heat shock protein 90 (HSP90) to inhibit the IKK/NF-κB pathway and reduce PD-L1 expression, which is crucial in anti-PD-L1 therapy by promoting CD⁸⁺ T-cell infiltration [107]. Circadian rhythm is not only linked with infiltrating immune cells but also regulates immune inhibitory molecules, including PD-L1 and CTLA-4, through circadian genes. A comprehensive study revealed that circadian clock genes are broadly dysregulated across multiple cancers, and the disorder of the circadian clock led to T cell exhaustion and heightened expression of immune inhibitory molecules such as CTLA-4 and PD-L1 [108]. While the specific mechanisms by which circadian rhythms influence the expression of immune checkpoint molecules and modulate immunotherapy in GIC remain unclear, substantial evidence from other cancers suggests that targeting circadian genes could potentially enhance the immunotherapy response in GIC patients.

Apart from chronotherapy and melatonin, recent studies suggest that gut microbiota may represent a novel application of circadian rhythm. It is widely recognized that alterations in the species composition and metabolites of gut microbiota have profound effects on metabolism, inflammation, and carcinogenesis [109]. Disorders in the host’s circadian rhythm can impact the circadian and metabolic balance of the gut microbiota, and conversely, microbiota metabolites can also influence the host’s circadian rhythm [110]. For example, one study found that the intestinal epithelial circadian rhythm was regulated by short-chain fatty acids, which induced histone deacetylase 3 (HDAC3) inhibition generated by the intestinal microbiota [111]. Additionally, the intestinal microbiota can convert trimethylamine into trimethylamine N-oxide (TMAO), thereby affecting the expression of circadian genes such as CLOCK and BMAL1 in liver endothelial cells [112]. Historically, research on circadian rhythms and gut microbiota has primarily focused on sleep disorders and metabolic syndrome; however, recent investigations have begun to examine their roles in cancer development. Notably, disorder of circadian rhythm has been shown to induce the production of gut microbiota and its metabolite, taurocholic acid (TCA). This metabolite facilitates the accumulation of myeloid-derived suppressor cells (MDSCs) in the lungs of mice and contributes to CRC lung metastasis [113]. Another study concerning lung cancer indicated that time-restricted feeding markedly inhibited tumor growth by modulating the abundances of the fecal microbiome, metabolome, and circadian oscillation [114]. Despite these findings, further comprehensive studies are required to elucidate the mechanisms by which circadian rhythms interact with gut microbiota in GIC treatment.

However, there are certain limitations associated with the application of circadian rhythm in GIC treatment. Firstly, because circadian rhythms are influenced by numerous factors, such as diet and light exposure, accurately assessing an individual’s circadian rhythm is challenging. Furthermore, as with other therapeutic approaches, substantial interindividual variability exists in circadian rhythms due to genetic differences and lifestyle habits [109]. Therefore, therapies must be tailored to the specific characteristics of each patient, which poses additional challenges to the clinical implementation of circadian rhythm-based treatments.

In summary, this review compiles compelling evidence supporting the notion that circadian rhythm can impact GIC development through multiple pathways. Despite the limitations in its application, integrating circadian rhythm with other therapeutic strategies remains a promising area of research that warrants further exploration.

Funding Statement

This work was supported by grants from the National Natural Science Foundation of China (81972881).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

This review contains no data.