Cervical cancer is a gynaecological malignancy with a high incidence worldwide that seriously influences women's lives. Many studies to date have shown that host genetic variation has a certain association with susceptibility to cervical cancer [23–28]. In the current study, we found that rs1800629 and rs361525 in the TNF-α gene promoter are related to susceptibility to cervical cancer in a Chinese Han population.
Recent studies have shown that TNF-α may promote the spread and metastasis of cancer, resulting in increased serum TNF-α levels in patients with advanced cervical cancer [29, 30]. In addition, studies have shown that TNF-α gene promoter polymorphisms are associated with TNF-α expression. For example, rs1800629 and rs361525 influence transcription of the TNF-α gene [31–34]. Moreover, several studies have found that rs1800629 and rs361525 are associated with breast cancer, liver cancer, gastric cancer and cervical cancer [12, 13, 15, 35–39]. In 2005, Duarte et al. reported that the A allele of rs1800629 is associated with an increased risk of invasive cervical cancer in the Portuguese population [13]. Singh et al. and Du et al. also found the rs1800629 A allele to be associated with an increased risk of cervical cancer in an Indian population and a Chinese population from Sichuan Province, southwestern China, respectively [12, 15]. However, in 2012, Wang et al. reported that rs1800629 was not significantly associated with cancer in a Chinese population from Liaoning Province, northeastern China [40]. The results of the current study show that the A allele of rs1800629 is a protective factor for cervical cancer, especially SCC, in the Chinese Han population. Our findings are similar to those of Zidi et al. in Tunisia [41]. In general, association results vary among different populations and even the same population. One of the reasons for such inconsistency is the different genetic backgrounds of different populations, even the same population. For example, the samples included in Du et al., Wang et al. and our study are from different provinces of China. Our previous study reported that the Han population in China could be categorized into southern Han and northern Han according to their distinction in genetic background [42]. Although Sichuan and Yunnan are located in southwestern China, the population from Sichuan Province belongs to the southern Chinese population, and the population from Yunnan Province has special genetic characteristics between the southern and northern Chinese Han populations. Other reasons for inconsistency among populations may be different sample sizes. For example, the sample in Du et al. involved 522 cervical cancer patients and 550 healthy individuals, whereas 1,173 healthy controls, 579 patients with CIN, and 980 patients with cervical cancer were enrolled in the current study.
In 2001, Jang et al. reported that the A allele of rs361525 is a protective factor for cervical cancer in a Korean population [14]. Nevertheless, in 2015, Zidi et al. showed that the A/A and G/A-A/A genotypes of rs361525 are related to the progression of CIN but not to the eventual occurrence of cervical cancer in Tunisia [41]. In 2018, Li et al. reported that the rs361525 A allele is a risk factor for cervical cancer in a Chinese population from Shandong Province, northern China [18], and in 2019, Du et al. showed that it is a protective factor against cervical cancer in Sichuan Province, southwestern China [12]. In the current study, the A allele of rs361525 was found to be a risk factor for cervical cancer in a Chinese population. Moreover, in subgroup analysis, the A allele was a risk factor for SCC but not AC. Our results are similar to those of Li et al., in which the rs361525 A allele was a risk factor for cervical cancer. One of the reasons for the discrepancy between the studies of Li et al. and Du et al. and ours may be the different pathological types of cervical cancer included; we found that the A allele of rs361525 is a risk factor for SCC, which indicates that the A allele has different roles in pathological types of cervical cancer. SCC is the most common pathological type of cervical cancer, accounting for approximately 75–80%, followed by AC, which accounts for approximately 10.0–25%, and adenosquamous carcinoma, which accounts for approximately 3–5% [43]. Therefore, in the future, it is necessary to study the role of rs361525 in the different pathological types of cervical cancer.
To date, there are no reports on the association between rs1800630 and cervical cancer. In the current study, we found that rs1800630 was associated with cervical cancer, but not CIN, in the Chinese Han population (P = 0.011). However, after Bonferroni correction, there was no significant difference between the control and cervical cancer groups. In inheritance model analysis, the A/C-A/A genotype was related to a reduced risk of cervical cancer (P = 0.006, OR = 0.77; 95% CI = 0.64–0.93) in the dominant model. Previous studies have shown that rs1800630 is associated with gastric cancer and hepatocellular carcinoma [44, 45], with the A allele of rs1800630 being a protective factor in the former but a risk factor in the latter. Our results show that the A allele of rs1800630 is a protective factor against cervical cancer (OR = 0.827; 95% CI = 0.715–0.959). The reason for this difference between gastric cancer and hepatocellular carcinoma may be the different cancer types. In 1998, Higuchi et al. reported that the A allele of rs1800630 increased the level of TNF-α in peripheral blood mononuclear cells [46], yet in 1999, Skoog et al. reported that it may decrease transcription of the TNF-α gene in HepG2 cells [47]. Therefore, the role of the A allele of rs1800630 differs among cells. More samples should be included In future studies, and the role of rs1800630 in cervical cancer should be investigated.
In the current study, we found that rs1800629 and rs361525 in the TNF-α promoter gene are associated with cervical cancer in a Chinese Han population. The A allele of rs1800629 is a protective factor for cervical cancer and SCC, whereas the A allele of rs361525 is a risk factor for cervical cancer and SCC. Nonetheless, association results vary among different populations. Thus, multicentre and more samples from different regions should be evaluated to study the association between TNF-α gene polymorphisms and cervical cancer. Moreover, the function of polymorphisms should be investigated in the future.