Association study of IL10 gene polymorphisms (rs1800872 and rs1800896) with cervical cancer in the Bangladeshi women

Highlights

• Role of IL10 variants in Bangladeshi cervical cancer patients was evaluated by ARMS-PCR.

• Significantly increased cervical cancer risk was found for rs1800872 and rs1800896.

• Haplotype analysis found a strong linkage disequilibrium between two SNPs.

• An upregulated IL10 mRNA level was found in silico in cervical cancer tissues.

Abstract

Objective

Cervical cancer is one of the most destructive diseases among females worldwide, especially in developing countries. Interleukin-10 (IL10) is a multifunctional cytokine, and polymorphisms in the IL10 gene have been identified in multiple malignancies. However, no prior studies were conducted to determine the association of IL10 polymorphisms (rs1800872 and rs1800896) with cervical cancer patients in Bangladesh.

Methods

This case-control study was carried out on 240 cervical cancer patients and 204 healthy volunteers. Genotyping was performed using the tetra-primer amplification refractory mutation system polymerase chain reaction (ARMS-PCR).

Results

In the case of rs1800872, CA and AA genotypes significantly increased the risk of cervical cancer (OR = 1.59, 95% CI = 1.01–2.49, p = 0.043; OR = 2.75, 95% CI = 1.53–4.93, p = 0.0007, respectively) but the significance did not exist for CA genotype after Bonferroni correction (p < 0.025). An increased risk was also observed for the dominant model, recessive model, and allele model (A vs. C) of rs1800872 (dominant model: OR = 1.83, 95% CI = 1.18–2.80, p = 0.006; recessive model: OR = 2.00, 95% CI = 1.22–3.29, p = 0.006; allele model: OR = 1.55, 95% CI = 1.19–2.03, p = 0.001) which remained significant after the correction of Bonferroni. For rs1800896, only GG genotype and recessive model showed increased risk for cervical cancer (GG vs. AA: OR = 3.48, 95% CI = 1.46–8.31, p = 0.005; recessive model: OR = 3.57, 95% CI = 1.52–8.38, p = 0.003). These associations were statistically significant, and the significance existed after Bonferroni correction. Haplotype analysis revealed that AA haplotype significantly increased the risk (OR = 1.56, p = 0.001) whereas, CA haplotype significantly lowered the risk (OR = 0.42, p = 2.42x10^-8), and both rs1800872 and rs1800896 are strongly in linkage disequilibrium (D’=1, r² = 0.333). Moreover, the IL10 mRNA level was found up-regulated in silico in cervical squamous cell carcinoma tissues compared to healthy tissues (p = 1.11x10^-16).

Conclusion

Our study suggests that rs1800872 and rs1800896 polymorphisms of IL10 gene are associated with cervical cancer in Bangladeshi females.

Introduction

Cervical cancer is the second most common female malignancy after breast cancer in terms of occurrence and mortality throughout the world [1]. Overall, it is the fourth common type of cancer in women that commonly occurs in the lower end of the uterine cervix, affecting normal tissues of the epithelium of the cervix and subsequently leading to abnormal changes into the deeper tissues [2], [3], [4]. Each year, over half a million females are reported to be affected by cervical cancer globally, which leads to more than 300,000 deaths. More surprisingly, approximately 90% of cervical cancer patients are from middle-income and lower-income countries [5]. To be specific, around 569,847 new cervical cancer cases were recorded globally in 2018, which constitutes almost 3.2% and 6.6% respectively in terms of overall cases and female cancers, with a recorded death of 311,365 women [5], [6]. Bangladesh is one of the lower-middle-income countries, which has a severe cancer prevalence and associated deaths. According to World Health Organization (WHO) data published in 2018, about 5.4% of all cancer cases reported in Bangladesh were cervical cancer, and about 4.8% of deaths occurred due to this malignancy [7].

Human papillomavirus (HPV) is considered as the major causative agent for developing cervical cancer in women. However, HPV infection is not always adequate for this disease’s progression as most of the patients (70% to 90%) eliminate the agent within 1–2 years after the primary diagnosis [3], [4], [8]. Besides some specific high-risk types of HPV, other risk factors including, time of the first intercourse, early pregnancy, multiple pregnancies within a limited period of time, various sexual partners, oral contraceptive pills, race or ethnicity, smoking habit, and poor socioeconomic conditions play a role in cervical cancer development [8], [9], [10]. More importantly, investigations revealed that genetic heritability is one of the most common intrinsic factors that increase the probability of developing cervical tumors by almost 27% [11], [12]. Genetic differences in multiple immune mediators have been investigated and found to be associated with HPV-related epithelial transformation of the cervix that is a critical determinant for the progression of cervical neoplasia [13].

Even though HPV infection is responsible for developing cervical cancer in a specific percentage of infected women, there is a latent period after the infection and before diagnosing cancer, which demonstrates that cell-mediated immunity is a part of regular host immune activity, controlled by cytokines and the activities of cytokines are essential for cervical cancer development [14]. Indeed, variations in host genetic susceptibility and immune responses are linked to increased HPV-associated cervical carcinogenesis [15].

Interleukin-10 (IL10) is an important multifunctional cytokine produced from lymphocytes, monocytes, and other cell types with notable anti-inflammatory and immune-suppressive properties [16], [17]. IL10 comprises five exons and four introns and located on human chromosome 1 (1q31–1q32) [17], [18] and studies showed that IL10 is associated with tumor invasiveness and regulates angiogenesis in malignant cells [13], [17]. It has been found that IL10 prevents the generation of pro-inflammatory cytokines from activated lymphocytes and macrophages in these cells [19]. A recent investigation on four SNPs of IL10 gene including rs1800871 (-819C/T), 1,800,872 (-592C/A), rs1800890 (-3575 T/A), and rs1800896 (-1082A/G) reported that rs1800896 is associated with pediatric post‐bronchiolitis asthma [20]. A meta-analysis [17] explicated that rs1800872 may contribute to the susceptibility of smoking-related cancer development.

Multiple studies reported the association of IL10 gene polymorphisms with the risk of cancer in the cervix. For example, a recent case-control association study of IL10 rs1800872 polymorphism in Chinese women suggested that this variant is involved with the severity of cervical neoplasm [21]. Another study in the Chinese population investigated the correlation of rs1800871, rs1800872, and rs1800896 polymorphisms of IL10 gene and concluded that rs1800871 might contribute to the risk of cervical cancer [22]. Ni et al. [23] conducted a meta-analysis in the Asian population that demonstrated a significant association between the minor allele of rs1800872 and increased cervical carcinogenesis progression. However, they did not find any association for rs1800896 polymorphism. Association of rs1800872 is also found in Indian [24], Mexican [25], and Dutch population [26]. Interleukin-10 (-1082A/G) genetic polymorphism was also found to be associated with cervical cancer in Brazilian [27] and Japanese women [28]. These data suggest that rs1800872 and rs1800896 polymorphisms may be a risk factor for cervical cancer in Bangladeshi patients.

Based on geographical and biological diversity as well as ethnical variations in genetic makeup, the rate and extent of disease occurrences in different parts of the world may be different. Even the variations can be observed in the same origin or ethnicity [29], [30]. However, no genetic association studies have been performed in the Bangladeshi cervical cancer patients with rs1800872 and rs1800896 variants of the IL10 gene. Therefore, in line with previous findings in other populations, we have conducted the present case-control study to determine the association of the IL10 rs1800872 and rs1800896 polymorphisms.