Introduction
Hepatitis B virus (HBV) infection affects approximately 250 million people worldwide, and there are 500,000 to 700,000 deaths each year due to complications caused by HBV infection [
1]. Chronic HBV infection leads to activation of the compensatory mechanism for liver cell death by triggering a sustained inflammatory response, which gradually worsens to cirrhosis and eventually to hepatocellular carcinoma (HCC) [
2,
3]. Accumulated evidence suggests that the development of HCC is closely related to the tumor microenvironment (TME), and cytokines/chemokines produced by immune cells and cancer cells are critical regulators of the TME [
4,
5]. Inflammatory cells infiltrate the liver and participate in tumor development and progression by stimulating an immune response. Notably, several cytokines/chemokines play essential roles in the pathogenesis, progression, invasion, and metastasis of HCC that progresses from chronic hepatitis B (CHB) [
5‐
7].
Unfortunately, HCC is often diagnosed in the middle or late stage, and the recurrence rate is as high as 70% [
8]. Therefore, serological detection of HBV-related liver disease is critical for monitoring progression and determining prognosis. Previous studies have investigated the role of serum cytokine detection in HBV-associated liver disease [
9,
10]. Most related studies have focused on the effect of only a single cytokine, but the regulatory network of cytokines is highly complex [
2,
11]. This complexity suggests that only simultaneous and consistent measurements of serum cytokine concentrations and a comprehensive understanding of how cytokines are related to each other will help define their roles in tumor development [
2,
12,
13]. Cytokines are also structurally pleiotropic, making specific targeting of critical cytokines extremely difficult [
11]. Ideal tumor markers should have strong tumor sensitivity and specificity. In recent years, to improve the percentage of positive cells, serological detection of tumor markers has developed in the direction of combined screening for multiple markers. The purpose of this study was to determine the expression patterns of 10 cytokines or chemokines in different stages of HBV-related liver disease and explore candidate biomarkers for determining the prognosis of HCC patients.
Materials and methods
Patient selection
This was a retrospective case‒control study. According to the diagnostic criteria of the Guidelines for the Prevention and Treatment of Chronic Hepatitis B (version 2015) and the Specifications for Diagnosis and Treatment of Primary Liver Cancer (version 2017), 106 individuals from the biological sample bank of Tianjin Third Central Hospital were included. This study included 20 healthy individuals (HI group), 11 self-limited hepatitis B virus (SL-HBV) infection patients (SL-HBV group), 20 CHB patients (CHB group), 18 hepatitis B virus liver cirrhosis (LC) patients (LC group), 18 hepatocellular dysplastic nodule (DN) patients (DN group; pathological diagnosis based on biopsy, including eight patients with low-grade dysplastic nodules and ten with high-grade dysplastic nodules) and 19 HCC patients undergoing radical resection (HCC group). One blood sample was collected from each patient in the HCC group before surgery, one blood sample was collected at two days post surgery, and one blood sample was collected at three months post surgery. All HCC patients were given cephalosporins (first or second generation) within 2 days after surgery, and there was no recurrence after a 3-month follow-up. The subjects in each group were of Han nationality in the Tianjin area. The routine blood and biochemical indices of the healthy individuals were normal, and the HBV immunological marker results were negative. The SL-HBV-infected patients had evidence of HBV infection (positive for at least two of the anti-HBs, anti-HBe, and anti-HBc antibodies; negative for HBsAg, HBeAg, and HBV-DNA); had a normal liver function indicator; had no history of liver disease or a clear history of acute hepatitis B; and had recovered without any treatment. The exclusion criteria included coinfection with other viruses, such as hepatitis A virus, hepatitis C virus, or hepatitis D virus, and other liver diseases, including alcoholic liver disease, metabolic liver disease, fatty liver disease, and liver fibrosis. All blood samples in this study were collected and processed with patient consent, and the study was approved by the Ethics Committee of Tianjin Third Central Hospital (IRB2019-040-01).
Biochemical parameters and virological detection
Parameters of liver function, including ALT, AST, AFP, AFU, TBIL, ALB, GLO, and the white-to-sphere ratio (A/G), were measured by a Roche automatic biochemical analyzer (Roche Cobas c 701; Roche, Switzerland). The serum HBV-DNA load was quantitated using an automatic nucleic acid purification and fluorescence PCR analysis system (Anadas9850, Amplly, China). The levels of HBsAg, anti-HBs, HBeAg, and anti-HBe were tested using an automatic microparticle chemiluminescence immune analyzer (ARCHITECT i4000SR, Abbott, USA). HBsAg negativity was defined as < 50 IU/ml.
Cytokine measurements
Fasting peripheral venous blood (3 ml) was collected from the subjects, and the serum was isolated and stored at -80 °C for cytokine detection. EMD Millipore’s MILLIPLEX® MAP Human Cytokine/Chemokine Magnetic Bead Panel (Cat. # HCYTOMAG-60 K; EMD Millipore, Billerica, MA, USA) was used for the simultaneous quantification of six human cytokines (fibroblast growth factor 2 (FGF-2), interferon-α2 (IFN-α2), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10) and vascular endothelial growth factor A (VEGF-A)) and four chemokines (growth-related oncogene-alpha (GRO-α/CXCL1), interleukin-8 (IL-8/CXCL8), interferon-γ-inducible protein 10 (IP-10/CXCL10) and monocyte chemotactic protein 1 (MCP-1/CCL2)). The experimental procedure was carried out according to the manufacturer’s protocol. Briefly, the main steps included preparing serum samples and immunoassay reagents, performing the immunoassay procedure, washing the plate, setting up equipment settings and on-machine storage, and analyzing average fluorescence intensity data. Each experiment was performed in duplicate using the same procedure. The analysis step was performed using a Luminex 200 System with xPONENT® software (Luminex, Austin, TX, USA).
Statistical analysis
Descriptive statistics were calculated to characterize the study population. Serum HBV-DNA levels and HBsAg concentrations were logarithmically transformed for analysis. Categorical variables are expressed as the absolute and relative frequencies, and comparisons between groups were performed using the chi-square test or Fisher’s exact test. Continuous variables with a normal distribution are expressed as the mean ± standard deviation (SD). One-way analysis of variance was used to compare the means of multiple samples. Continuous variables with a nonnormal distribution are expressed as medians (Q1, Q3), and the Mann‒Whitney U test and Kruskal‒Wallis test were used to compare two groups or multiple groups. A two-tailed p value less than 0.05 was considered to indicate statistical significance. A Spearman correlation matrix was used to analyze the correlations of the 10 cytokines/chemokines. Correlations with a p value < 0.05 were included in the network visualization. The statistical analyses were performed using SPSS version 26.0 (SPSS, Inc., Chicago, IL, USA) and GraphPad Prism 8.0 (GraphPad Software, La Jolla, CA, USA).
Discussion
HBV poses a severe threat to public health and is a high risk factor for chronic hepatitis, occult hepatitis, cirrhosis, and HCC [
1,
14]. As HBV is a noncytopathic virus, the associated inflammation and direct liver damage caused by this virus are mediated by the immune response [
9]. Understanding the expression levels of serum cytokines is crucial for understanding the development and metastasis of tumors and is helpful for determining the prognosis and treatment of tumors [
7,
15,
16]. Traditional enzyme-linked immunosorbent assays (ELISAs) usually detect only one cytokine at a time [
16]. Therefore, Luminex liquid chip analysis was used in this study because this technology has high sensitivity and can simultaneously detect ten serum cytokines associated with HBV infection [
11]. In addition, compared with solid-phase chip technology, the Luminex liquid chip has the advantages of a simple procedure, good repeatability, and high throughput [
9,
17].
Host immune factors play important roles in the outcome of HBV infection. A natural complete response to HBV leads to self-healing, while an inadequate or deficient immune response may lead to persistent viral replication and necrotic liver inflammation, resulting in chronic HBV infection, cirrhosis, and even HCC [
9]. Cytokine/chemokine homeostasis plays a key role in the occurrence and development of hepatitis B. Abundant cytokines/chemokines not only participate in the initiation and regulation of the immune response but also directly or indirectly participate in the inhibition of viral replication and even malignant liver cell transformation [
9,
16]. Multiple cytokines are differentially expressed in patients with CHB, LC or HCC, suggesting that the cytokine profile may have certain diagnostic and prognostic value [
2,
6,
7,
16,
18,
19]. However, there are great differences among different researchers and among different detection methods. Moreover, there is a lack of dynamic analyses of liver disease progression at different stages and of HCC before and after surgery. Therefore, serum samples were collected from patients with CHB or HBV-related LC, DNs or HCC before and after HCC surgery for analysis; healthy controls and patients with SL-HBV infection were used as controls. The results showed that CHB patients with persistent HBV infection had a clear inflammatory biomarker profile and had the highest level of immune disorders, followed by patients with cirrhosis. Among the studied biomarkers, 4 cytokines (FGF-2, IFN-α2, IL-4 and IL-6) and 3 chemokines (IL-8, IP-10 and MCP-1) were highly expressed in the CHB group, 2 cytokines (IL-4 and IL-6) and 2 chemokines (IL-8 and IP-10) were highly expressed in the LC group, and only IP-10 and IL-10 were highly expressed in the DN group and the HCC group, respectively.
According to their receptors and roles in tumorigenesis and development, cytokines/chemokines can be divided into three categories. The cytokines/chemokines associated with the inflammatory response include IFN-α2 [
20], IL-4 [
21], IL-6 [
22], IL-10 [
23], IL-8 [
24] and IP-10 [
25], and IL-6 is an important proinflammatory cytokine. IFN-α2, IL-4 and IL-10 are important anti-inflammatory cytokines. IL-8 and IP-10 are chemokines that induce the migration of immune cells to inflamed tissues. Angiogenesis-related cytokines/chemokines include FGF-2 [
26], VEGF-A [
27] and GRO-α [
28]. MCP-1 is a chemokine associated with tumor growth, invasion, and metastasis [
29]. The functions of cytokines are multifaceted, and they can participate in the regulation of different signaling pathways in different immune microenvironments and even have bidirectional regulatory functions, such as proinflammatory/anti-inflammatory and procancer/anticancer functions [
3,
9,
10].
During HBV infection, especially in CHB patients, IFN-α2 is a vital cytokine for immune stimulation and viral clearance, and an increase in IFN-α2 is related to activation of the anti-HBV immune response [
18]. IFN-α expression is significantly increased in patients with CHB and might inhibit HBV replication by inhibiting the transcriptional activity of covalently closed circular DNA (cccDNA) [
30]. The results of this study confirmed that IFN-α2 was highly expressed in the CHB and HCC groups, with both of these groups exhibiting significantly greater IFN-α2 levels than the HI and SL-HBV groups.
Previous studies have shown that IL-4 plays dual roles in HBV infection. An increase in the IL-4 level in the peripheral blood can inhibit the production of IFN-γ and induce a Th1-type immune response, leading to continuous HBV replication and promoting the establishment of immune tolerance [
31]. Paradoxically, IL-4 also inhibits HBsAg production and HBV replication, thereby mediating the host antiviral response [
10]. In this study, IL-4 was highly expressed in the CHB and LC cohorts, which indicated that the CHB and LC cohorts were in a period of active viral replication and a strong antiviral response.
IL-6 is an inflammatory cytokine produced by macrophages that promotes tumor growth and progression by promoting chronic inflammation [
22]. In HBV infection, on the one hand, IL-6 can eliminate the virus by stimulating an immune response via infected hepatocytes; on the other hand, it can induce the occurrence of hepatitis, LC and HCC [
14]. In this study, the IL-6 levels in the CHB, LC and HCC groups were significantly greater than those in the HI and SL-HBV groups, which also confirmed the findings of the above study.
IL-10 is a multifunctional immunosuppressive cytokine secreted by Th2 cells, cancer cells and other cells and is an important cytokine that downregulates the activity of other immune cells and leads to persistent infection [
3,
31]. Chau GY et al. reported that tumor cells secreted IL-10 and that the level of IL-10 decreased significantly after HCC resection [
15]. Further research showed that the serum IL-10 concentration was a negative prognostic factor for a significantly shortened median survival time [
32,
33]. Therefore, in the present study, the high expression of IL-10 in the HCC group and its rapid decrease after surgery suggested that IL-10 can be secreted by cancer cells, and its dynamic changes before and after surgery can be used for prognostic evaluation. In contrast to the above results, the IL-10 level measured by Su Z et al. was significantly lower in the hepatoma group than in the CHB group [
34].
IL-8, a proinflammatory CXC chemokine, is significantly elevated in the serum of CHB and HBV-associated HCC patients [
35,
36]. However, the results of this study showed that IL-8 was highly expressed in the CHB and LC groups, with significantly greater levels in those groups than in the HCC group. However, the IL-8 concentration significantly increased 3 months after surgery, and these changes need to be further confirmed in HCC patients.
According to the analysis of the three groups before and after HCC surgery, the expression levels of IL-4, VEGF-A and IL-8 tended to increase, and the expression levels of IL-10 and GRO-α tended to decrease, suggesting that these 5 cytokines/chemokines may be closely related to HCC progression or prognosis. It was speculated that these factors may be useful in evaluating patient prognosis after HCC surgery. Similarly, Chen et al. used preoperative serum to select 6 out of 39 cytokines/chemokines to construct a novel cytokine-based prognostic classifier (CBPC) to predict HCC recurrence [
16]. The levels of 4 cytokines/chemokines (GRO, IL-8, IP-10 and VEGF) were consistent with the findings of this paper. Jekarl et al. analyzed the changes in 13 cytokine profiles in HCC patients treated with transarterial chemoembolization (TACE). This study indicated that TACE increased or decreased the levels of most cytokines, including the three cytokines also studied in this paper, within 60 days after treatment. The change in IL-10 was consistent with that reported in this paper, in which a decreasing trend was shown, while the IL-6 level increased and the IL-4 level remained stable [
6]. Therefore, it is speculated that the differential expression of cytokines/chemokines may reflect the therapeutic differences between radical resection and TACE.
Analysis of the correlations of the 10 cytokines/chemokines in the three periods before and after HCC surgery revealed that most of the cytokines/chemokines with significant correlation differences were positively correlated before and after surgery, suggesting that increases in the levels of these cytokines/chemokines might be accompanied by increases in other inflammatory molecules. Vinhaes et al. used molecular degree of perturbation (MDP) scores to assess global inflammatory imbalances associated with unitary HBV infection and found that the significant associations of most factors were positive despite the use of different clinical groups [
14]. That is, increased expression of a specific marker is usually accompanied by increased levels of perturbations in other inflammatory molecules, especially in chronic HBV carriers. Ribeiro et al. also reported positive correlations between IFN-γ, TNF-α, IL-10, IL-6, IL-4, and IL-2 in HBV-positive individuals, with the levels of these cytokines tending to increase together [
37].
Correlation analysis between cytokines/chemokines and clinical indicators revealed that in the CHB, LC, DN and HCC groups, there were 6 pairs of positive correlations and 1 pair of negative correlations; 18 pairs of positive correlations and 5 pairs of negative correlations; 3 pairs of positive correlations and 2 pairs of negative correlations; and 8 pairs of positive correlations and 5 pairs of negative correlations, respectively. Although no consistency or regular change in any index was found among the groups due to the large number of indicators, small sample size, or complexity of the factor network, similar research results were obtained in similar studies [
13,
19,
25,
34]. Lian et al. reported that, compared with those in the HI and SL-HBV groups, the serum IL-10 and IP-10 concentrations in the CHB patient group were increased and positively correlated with ALT levels [
13]. Wiegand et al. reported the highest concentration of CXCL10 (IP-10) in hepatitis patients (the HBeAg-positive hepatitis phase [EPH]), and this concentration significantly differed from that in HBV carriers (inactive carriers [ENIs]). Furthermore, IP-10 concentrations showed the strongest correlation with ALT titers in EPH (
r = 0.53,
P < 0.001) and ENH patients [
19]. Su Z et al. showed significantly elevated levels of IP-10 in CHB patients with abnormal liver function, and IP-10 was positively correlated with ALT and AST levels [
34]. These results suggest that CXCL10 (IP-10) may be a useful marker for further characterizing the stage of chronic HBV infection.
This study has several potential limitations. First, the sample size was small, and the number of time points for dynamic monitoring was also small. In addition, cytokine levels might be affected by other diseases, anti-inflammatory drugs, or individual differences. Moreover, this study focused on only 10 circulating cytokines and chemokines. Finally, enzyme-linked immunospot (ELISPOT) assays were not used to detect HBV-specific T-cell responses in the peripheral circulation.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.