ERCC4 rs1800067, is a nonsynonymous SNP located on exon 8. SNPs located in exonic regions result in amino acid variation in the protein products of genes. To the best of our knowledge, this is the first study to demonstrate the association of ERCC4 SNP rs1800067 with gallbladder cancer and its prognosis. Our study demonstrates that the minor allele A is more frequent in control than patients. A variant allele may become a protective allele or associated with a disease when environment changes [15]. These environmental changes may also be a contributing factor for GBC. Since the geographic distribution of GBC is highly uneven, there may be differences in environmental exposures and regional intrinsic predisposition to carcinogenesis [16]. We demonstrate that genotype GA and allele A of ERCC4 rs1800067 is significantly associated with decreased risk of gallbladder cancer. Our results agree with previous studies linking the allele A with a significantly decreased risk of glioma cancer in the Asian population and lung cancer [17, 18]. Recent studies have shown a significant association of ERCC4 rs1800067 in glioma, gastrointestinal stromal, cervical and meningioma cancer [6, 19–22] but it does not show association with other cancers such as head and neck, thyroid, breast, and osteosarcoma [23–27]. Our results demonstrate that the association of rs1800067 follows the dominant model in gallbladder cancer. Our result similar to previous studies, Wang et al., [28], Ravegnini et al., [21], and Bajpai et al., [6] shows significant association of rs1800067 follows the dominant model in glioma, gastrointestinal stroma, and cervical cancers respectively. Previous studies have reported that genotypes of ERCC4 rs1800067 is not significantly associated with age of onset, gender and tumor stages in GIST [21], larynx cancer [29] and head and neck cancer [23]. However, in the present study, we have found that the genotypes of ERCC4 rs1800067 is significantly different between early and late age of onset of the disease. Also, ERCC4 rs1800067genotypes are significantly different between males and females in GBC patients. AA genotype of ERCC4 rs1800067 is more frequent in the early stages of tumors in GBC patients. These studies suggest that the AA genotype is less aggressive than the GG genotype. Earlier studies have demonstrated that there is no significant association of rs1800067 with overall survival in benign breast cancer, osteosarcoma, and gastrointestinal stromal tumors [21, 26, 30]. Similarly, in the present study, we did not find a significant association of rs1800067 genotypes with overall survival. Our study demonstrates that A carrier genotypes significantly increases the overall survival in patients with early stages of tumors and with chemotherapy. Discordant to our study, Sun et al. [27] have reported that ERCC4 rs1800067 genotypes did not significantly influence the response to chemotherapy in patients with osteosarcoma. Our result suggests that ERCC4 rs1800067 polymorphism can play an important role in the carcinogenesis of the gallbladder.
Higher expression of ERCC4 has been associated with a longer overall survival (OS) in male patients with colon cancer [10]. Also, ERCC4 has been reported to be a favourable prognostic marker in triple-negative breast cancer [31], esophageal cancer [32], serous ovarian cancer [11], and astrocytoma [33]. We did not find a significant difference in mRNA expression of ERCC4 between gallbladder cancer and control samples. Zhao et al., [11] found that high expression of ERCC4 indicates better survival in ovarian cancer patients. Our study demonstrates that high expression of ERCC4 does not associated with the overall survival of gallbladder cancer patients. Our data demonstrate significant differential ERCC4 expression among early and late stages of tumors. Discordant to our result, Schena et al., [34] have reported that ERCC4 expression did not significantly differentiate between stages of tumors in head and neck squamous cell cancer.
In conclusion, our study demonstrates that the minor allele A is a protective role in gallbladder carcinogenesis in the Indian population. The genotypes GA + AA, being the risk genotype, increases the overall survival in months with early stage of tumor and chemotherapy. Expression profiling results show that the up-regulation of ERCC4 is an early event in the progression of gallbladder cancer.