Association of Pro-inflammatory Cytokines with Gastric Cancer Risk: A Case-Cohort Study

Article information

J Korean Cancer Assoc. 2024;.crt.2024.718

Publication date (electronic) : 2024 November 19

doi : https://doi.org/10.4143/crt.2024.718

Seungju Baek¹, Eunjung Park², Eun Young Park^1,3,

¹Graduate School of Public Health, Korea University, Seoul, Korea

²Department of Cancer Control and Population Health, National Cancer Center Graduate School of Cancer Science and Policy, Goyang, Korea

³Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea

Correspondence: Eun Young Park, Department of Preventive Medicine, Korea University College of Medicine, 73 Goryeodae-ro, Seongbuk-gu, Seoul 02841, Korea Tel: 82-2-2286-1411 E-mail: eunyoungpark2022@gmail.com

*Seungju Baek and Eunjung Park contributed equally to this work.

Received 2024 July 29; Accepted 2024 November 18.

Abstract

Introduction

Gastric cancer (GC) ranks as the fourth most prevalent cause of global cancer mortality, demonstrating an alarming incidence of over one million newly diagnosed cases in the year 2020 (5.6%), accompanied by an estimated 768,793 mortalities (7.7%) [1]. In 2020, there were 247,952 newly diagnosed cases of cancer in South Korea, with GC accounting for 26,662 cases (10.8%) when combined for both genders, ranking fourth among all cancer types. Furthermore, the mortality associated with GC in the same year amounted to 7,510 deaths, resulting in a mortality rate of 14.6% per 100,000 population [2]. According to the latest data, the total number of cancer cases in 2021 was 277,523, with GC cases accounting for 29,361 [3]. The incidence rate of GC was 10.6%, showing a decreasing trend compared to the previous year. The mortality rate of GC in 2021 demonstrated a parallel decline with the incidence rate, registering at 14.1% [4]. Although there is an overall declining trend in the incidence and mortality rates of GC, it still has relatively higher rates compared to other types of cancer. Eastern Asia has recently reported over 60% of GC cases, which is significantly higher than in other countries, indicating a higher incidence and mortality rate of the disease in Asian countries compared to the rest of the world [5].

The high incidence and mortality rates of GC can be attributed to various factors, including dietary habits, smoking behaviors, alcohol consumption, and other environmental factors. Additionally, genetic factors also play a role in the etiology of GC. Therefore, the development of GC is influenced by a complex interplay of both environmental and genetic factors [6]. Furthermore, Helicobacter pylori infection is a major risk factor for the development of GC, and the International Agency for Research on Cancer (IARC) has classified H. pylori infection as group 1 carcinogen for GC [7]. Globally, there are approximately 2 million cancer cases related to infections each year, with H. pylori infection-associated GC accounting for one-third of these cases [8]. While there is a correlation between H. pylori infection and the incidence of GC, it is important to note that not all infected individuals will develop cancer. Only a subset of infected individuals will develop GC. Chronic inflammation is a significant factor in the development of various diseases, including GC [9]. In the process of inflammation influencing tumor formation, various mediators are involved, including proinflammatory cytokines (interleukin 6 [IL-6], tumor necrosis factor-α [TNF-α], interleukin 1β [IL-1β], interferon-γ [IFN-γ]), anti-inflammatory cytokines (interleukin 10 [IL-10]), inflammatory mediators (reactive oxygen species [ROS], nitric oxide [NO]), and immune cells. These mediators interact to regulate tumor cell proliferation, invasion, angiogenesis, and immune response, ultimately affecting tumor formation and progression [10].

The incidence rate of GC is significantly high among East Asian countries, including Korea [5]. However, there is a lack of research analyzing the association between inflammation and GC. Therefore, the aim of this study is to investigate the association between inflammatory indices—such as IL-6, TNF-α, IL-1β, IFN-γ, IL-10, ROS, and NO—and GC. We conducted a case-cohort study using serum samples collected before cancer diagnosis, based on the Korean National Cancer Center Community (KNCCC) cohort.

Materials and Methods

1. Case-cohort study design and study population

The KNCCC cohort, conducted between 1993 and 2010, was a community-based prospective study aimed at exploring the risk factors for cancer and protective factors associated with its prevention [11]. It involved 16,304 participants aged 30 years and older from Changwon, Chuncheon, Chungju, Sancheong, and Haman. Detailed information on demographics, lifestyle, and environmental factors was obtained through a structured questionnaire. Additionally, physical examinations and laboratory assessments were conducted, and blood and urine samples were collected at cohort enrollment. The collected serum samples were stored at ‒70°C (between 1993 and 2008) and were preserved at ‒140 °C (between 2009 and 2010). The obtained data were linked to the cancer registry data acquired from the Korea Central Cancer Registry and death records obtained from Statistics Korea, with follow-up until 31 December 2017.

A case-cohort study was designed to investigate the associations between serum levels of pro-inflammatory cytokines and the risk of GC. Of 16,304 men and women, participants with a follow-up period of less than 1 year for exclusion of undiagnosed cancer (n=446) and those who did not provide a serum sample (n=2,059) and information on other covariates (e.g., education achievement, cigarette smoking status, alcohol consumption status, body mass index [BMI]) (n=4,628) were excluded.

A representative subcohort of 822 participants was randomly selected by survey year, region, age, and sex from the eligible population who participated in the cohort between 2001 and 2010 (n=9,171). As a result, this study included 159 cases (148 cases plus 11 cases in the subcohort) and 822 participants in the subcohort (11 cases in the subcohort) (Fig. 1).

Fig. 1.

Study participant selection process.

This case-cohort study was reported following the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.

Results

1. Baseline characteristics of the study participants

A total of 981 participants were included in this case-cohort study, consisting of 159 GC cases (age [mean±standard deviation (SD)], 64.75±7.36 years) and the 822 subcohort cases (age [mean±SD], 60.11±10.80 years). The median follow-up periods were 5.82 years for GC cases (interquartile range [IQR], 3.57 to 8.63) and 11.43 years for the subcohort (IQR, 8.48 to 13.88), and the person-times were 997.33 years for GC cases and 9,004.12 years for the subcohort. GC cases had higher proportions of men, the elderly, low-educated persons, cigarette smokers, and drinkers than the subcohort. However, difference in proportions of obesity, meat consumption, and vegetable/fruit consumption was not observed. The detailed sociodemographic characteristics and lifestyle behaviors of the study participants are presented in Table 1.

Table 1.

Demographic characteristics of gastric cancer cases and the subcohort

At baseline, the serum levels of pro-inflammatory cytokines are presented in Table 2. The median IL-6, TNF-α, IL-1 β, IFNγ, and IL-10 values were higher in GC cases than in the subcohort.

Table 2.

Serum levels of pro-inflammatory cytokines stratified by gastric cancer cases and the subcohort

2. Risk of gastric cancer by serum levels of pro-inflammatory cytokines

The associations between serum levels of pro-inflammatory cytokines and the GC risk were shown in Fig. 2. For 2.74-fold increase, the risk of GC increased by 32% in IL-6 and 15% in IFNγ (HR, 1.32; 95% CI, 1.16 to 1.50), and IFNγ (HR, 1.15; 95% CI, 1.08 to 1.22).

Fig. 2.

Associations between serum pro-inflammatory cytokines and risk of gastric cancer in linear Cox proportional-hazards models. Gastric cancer risk for each unit increases in the natural log-transformed pro-inflammatory cytokines. Model 1 was unadjusted; Model 2 was adjusted for sex, year of entry into the cohort, and region; Model 3 was further adjusted for education, cigarette smoking (never, former, and current), alcohol consumption status (non-drinkers, < 24 g per day, and ≥ 24 g per day), and body mass index, physical activity, meat consumption, and vegetable/fruit consumption). CI, confidence interval; HR, hazard ratio; IFN-γ, interferon γ; IL-1β, interleukin 1β; IL-6, interleukin 6; IL-10, interleukin 10; NO, nitric oxide; ROS, reactive oxygen species; TNF-α, tumor necrosis factor-α.

In the Cox hazards models with categorized variables, the GC risk increased in the second, third, and fourth quartiles of serum IL-6 (HR [95% CI], 3.48 [1.73 to 6.99], 3.74 [1.91 to 7.29], 3.79 [1.93 to 7.48], respectively) compared with the lowest quartile. In addition, the GC risk was associated with higher levels of IL-1β and IFN-γ than the LOD value (HR [95% CI], 1.57 [1.12 to 2.21], 2.49 [1.73 to 3.58], respectively) (Table 3).

Table 3.

Associations between serum levels of pro-inflammatory cytokines and the gastric cancer risk by quartiles

Discussion

We identified potential biomarkers for identifying GC patients by analyzing five cytokines (IL-6, TNF-α, IL-1β, IFN-γ, and IL-10) and two inflammatory mediators (ROS, NO) associated with gastric inflammation. Our research elucidates a correlation between the serum concentrations of IL-6, IL-1β, and IFN-γ and the susceptibility to GC.

Previous studies have investigated various factors that influence the development and progression of GC and reported that increased levels of certain cytokines may play a role in the diagnosis of GC, which is partially consistent with our findings [14,15]. In a controlled study, it has been reported that the increase in levels of IL-6, IFN-γ, and IL-10 can be useful as diagnostic biomarkers for GC, particularly noting that the concentrations of IFN-γ and IL-10 vary according to the tumor-node-metastasis (TNM) staging of GC [16]. Several studies have reported differences in the genetic background between Asian and Caucasian populations concerning the epidemiology of different GC subtypes. Specifically, studies have indicated that variances in IL1B and IL10 gene polymorphisms could have varying impacts on the development of GC across different populations [17,18]. Although various studies have investigated the association between inflammatory cytokines and GC risk, our study was initiated due to the scarcity of research among Koreans and the inconsistent results stemming from population variances in gene polymorphisms.

GC, like other cancers, results from the complex interaction of various risk and protective factors. In its pathogenesis, genetic/epigenetic alterations and environmental factors, particularly H. pylori infection and diet, are recognized as significant contributors [19]. Immune cytokines produced during chronic inflammation have been shown to influence GC progression, though the exact roles of many cytokines remain unclear. Understanding the factors that affect cytokine levels is critical to elucidating their association with inflammation and GC. Previous studies have identified key factors that influence pro-inflammatory cytokine levels, such as age, BMI, smoking, alcohol consumption, physical activity, and dietary habits like red meat consumption [20- 22]. In this study, these factors were statistically adjusted to minimize their potential confounding effects, ensuring the association between pro-inflammatory cytokines and GC was not distorted, thereby increasing the validity and significance of the findings. In particular, smoking and alcohol consumption are well-known contributors to chronic inflammation, significantly raising pro-inflammatory cytokine levels. However, beyond smoking and alcohol, physiological and environmental factors like age, obesity, physical activity, and diet also play critical roles in regulating cytokine levels. Additionally, the mechanisms of inflammation can directly affect cytokine levels. Thus, while adjusting for these variables could lead to over-adjustment, potentially underestimating the association between cytokines and GC, the significant risks identified in this study highlight the importance of inflammation regulation in cancer management. These adjustments contribute to a more accurate reflection of the relationship between cytokines and GC, emphasizing inflammation control as a key aspect of cancer prevention.

Over the years, extensive research has been conducted on the correlation between inflammation and cancer, revealing that chronic inflammation and infections account for roughly 25% of all cancer incidences [23]. Specifically in GC, it has been demonstrated that chronic inflammation resulting from Helicobacter pylori infection and autoimmune gastritis escalates the susceptibility of an individual to gastric carcinogenesis [24]. GC mainly consists of adenocarcinomas (about 90%-95%) [25]. The two predominant subtypes of gastric adenocarcinomas are the intestinal type, distinguished by a more favorable prognosis attributed to distinct genetic mutations that may facilitate targeted pharmacotherapy, and the diffuse type, recognized for its aggressive growth pattern and advanced metastasis, posing greater therapeutic challenges compared to the intestinal counterpart [26]. Over 90% of adenocarcinomas are regarded as the culmination of prolonged mucosal inflammation. Intestinal type gastric adenocarcinomas are characterized by a series of events known as the “Correa pathway,” which initiates with chronic gastritis and advances through stages of gastric atrophy, intestinal metaplasia (IM), dysplasia, and cancer [27]. Preneoplastic lesions for GC, such as atrophic gastritis, IM, and dysplasia, occur in an inflamed environment influenced by a complex network of cytokines [28].

Inflammation, a crucial feature of both the innate and adaptive immune systems, is regulated by a variety of alternative mechanisms that aid in tissue restructuring and maintaining tissue balance, initiated by internal or external infections or injuries. Cells of the innate immune system, including macrophages, mast cells, dendritic cells, and natural killer cells, modulate the inflammatory response through the secretion of an array of molecules such as growth factors, cytokines, chemokines, proteases involved in matrix remodeling, as well as reactive oxygen and nitrogen species, thereby exerting control over the inflammatory cascade [10]. In a previous study, a comprehensive analysis was conducted on over 300 primary gastric carcinomas from distinct patient cohorts. The results revealed that most gastric malignancies exhibit dysregulation of key oncogenic pathways, including nuclear factor-κB (NF-κB) (39% of GCs), Wnt/beta-catenin (46% of GCs), and proliferation/stem cell (40% of GCs) cascades [29]. NF-κB pathway is well known for regulating pro-inflammatory cytokines such as TNF, IL-1, and IL-6, and previous study has demonstrated a significant correlation between NF-κB activation and IL-6 expression in human GC tissues [30]. Furthermore, previous research findings provide evidence indicating that the upregulation of integrin β3–mediated NF-κB signaling is partially responsible for the induction of GC cell proliferation and metastasis by IFN-γ [31].

Although our research revealed the association between serum levels of IL-6, IL-1β, and IFN-γ, and susceptibility to GC, there are several limitations. First, in this study, adjustment for H. pylori infection was not made due to a lack of data. Epidemiological studies conducted in Korea in 1998, 2005, and 2011 reported a prevalence of approximately 60%-70% among individuals aged 60 and above [32]. Given that the participants in this study have an average age in their 60s, where there is a high prevalence of H. pylori, the lack of adjustment for H. pylori is unlikely to distort the research findings. However, the lack of adjustment for H. pylori infection remains a limitation. Second, due to serum concentrations being measured only at the time of cohort enrollment, it is challenging to assess changes in serum concentrations after the time of measurement. Additionally, measurements taken at specific time points may not accurately reflect an individual’s average value. Single-point measurements may obscure the dynamic nature of cytokine levels and their relationships with disease processes, limiting the assessment of long-term exposure effects on disease onset. Cytokine levels fluctuate in various conditions, and not capturing their average may lead to misinterpretations regarding cancer progression and treatment response. Third, unlike general cohort studies, case-cohort studies focus on comparisons between cases and non-case groups, which can lead to selection bias. Additionally, the potential for bias inherent in the case-cohort design cannot be overlooked. Since this study was conducted on a specific subcohort, there is a risk of introducing biases that may affect the results. Therefore, the findings of this study have limitations in terms of generalizability and need to be replicated in a larger population or cohort. Fourth, like many observational studies, our research includes several potential confounding factors. To mitigate this limitation, we accounted for variables such as smoking, alcohol use, BMI, and dietary habits, all of which are strongly associated with the development of GC [6]. Nevertheless, our findings may still be subject to bias from other confounders (e.g., job story, previous medical conditions), due to self-reported data and the presence of unmeasured or omitted confounders (e.g., family history of cancer, exposure to stressful events).

Despite these limitations, our findings indicate that proinflammatory cytokines (IL-6, IL-1β, and IFN-γ) are associated with the risk of GC and suggest that their regulation could offer potential for GC prevention and treatment. The abnormal activation of pro-inflammatory cytokines plays a critical role in tumor growth and progression by influencing cancer development through modulation of immune responses and inflammation. Specifically, IL-6 is recognized for its role in promoting tumor growth, cell survival, proliferation, and angiogenesis, making elevated IL-6 levels a potential indicator of cancer development. This is supported by evidence demonstrating that drugs designed to block IL-6 signaling have shown positive effects in cancer patients [33]. Conversely, IL-1β and IFN-γ also impact the tumor microenvironment, but their effects are complex and vary depending on the cancer type [34,35]. Further research is needed to determine if elevated levels of IL-1β, and IFN-γ reliably indicate cancer development. While previous research suggests that smoking cessation, alcohol withdrawal, dietary changes, and lifestyle modifications such as exercise can reduce inflammatory cytokine levels, more investigation is required to establish the impact of these approaches on gastric cancer prevention [36-39]. The role of inflammatory cytokines can vary depending on factors such as the tumor microenvironment, gene expression, and interactions with other immune cells [40], highlighting the need for more in-depth research to fully understand their effects.

In this study, pro-inflammatory cytokines (IL-6, IL-1β, and IFN-γ) were found to be associated with the risk of GC. Our research findings can provide valuable insights for the development of GC prevention strategies and policies. The results suggest that these cytokines may serve as important indicators of cancer development, potentially aiding in the identification of high-risk populations and the formulation of personalized prevention strategies. Furthermore, given that GC is acknowledged as a major health concern worldwide, understanding the mechanisms of inflammation and cancer can be a valuable tool in comprehending cancer development and prognosis.

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