In this study, we observed that the risk of developing cervical cancer was higher among women who had given birth to five or more children. During pregnancy, women are more sexually active and therefore more exposed to HPV, which is a major cause of the main types of cervical cancer. Also pregnant women are more vulnerable to cancer because of the hormonal changes and the immune system modulation (Shah, Imami et al. 2018, Jørgensen, Persson et al. 2019).
Furthermore, menopausal status may also be a potential factor. Post-menopausal women were at higher risk than those who were not yet at menopause. This is in agreement with other research papers; a study done by Gyllensten et al. has shown that post-menopausal women are at a higher risk of contracting HPV virus (Gyllensten, Gustavsson et al. 2012). Another similar study carried out by Singh B and Nalini N. estimates the incidence of cervical cancer in post-menopausal women at 16% (Singh and Nalini 2017).
There is growing evidence that Tunisian women who experience menarche before the age of 16 may have an increased risk for cervical cancer. Several studies have supported this finding and suggested that anovulatory cycles are common in the first years after menarche, which is associated with a decreased production of progesterone that leads to a decreased production of cervical mucus. That mucus acts as a barrier to sexually transmitted infections including HPV infection (Syrjänen, Shabalova et al. 2008).
Another theory also supported the probability of a higher risk of cervical cancer in women exposed to HPV infection immediately after menarche including greater areas of ectopy, a very active maturation process (active metaplasia), and higher affinity of high-risk HPV types with changes in the local immune response of an immature cervix. . The immature cervix is more vulnerable to HPV infection (Toon, Arrand et al. 1986, Castle, Jeronimo et al. 2006).
Having relatives with any type of cancer puts patients at a higher risk than healthy control women with no family history of the disease. We cannot be sure whether this is linked to genes, or whether it is due to common shared family habits like diet, healthcare, daily routine, socio-economic status or exposure to environmental risk factors.
The increased incidence of cervical cancer in the Tunisian population shows an urgent need to identify multiple genetic lesions leading to aberrant gene expression programs that are responsible for the cancer phenotype.
Recently, several studies have investigated genes coding for proteins, which regulate a variety of biological processes like cell growth, proliferation, apoptosis, and metabolic pathways that could be potentially useful in cancer diagnosis, prognosis, and therapy (Terasaka, Kim et al. 2019, Xie, Wang et al. 2021).
From this point of view, the study of polymorphisms in genes involved in carcinogenic mechanisms is promising, especially genes coding for RNA-binding proteins (RBPs). One such RBP is ELAVL1 also known as HuR (Szabo, Dalmau et al. 1991). Additionally, ELAVL1 binds almost exclusively to cellular mRNAs and more specifically at introns and 3’UTRs (Chen and Shyu 1995, Bakheet, Hitti et al. 2018).
The RBP Elavl1/HuR is believed to have ubiquitous expression patterns in most tissues (Ma, Cheng et al. 1996, Lu and Schneider 2004) and has three distinct and highly conserved RNA-binding domains belonging to the RNA-recognition motif (RRM) family (Wächter, Köhn et al. 2013). ELAVL1 has been shown to be primarily localized at the nucleus but can translocate to the cytoplasm via phosphorylation of Y200, S202, and S221, located in the hinge region of the protein between the second and third RRM (Chen and Shyu 1995).
Furthermore, HuR could contribute to the aberrant gene overexpression and promotes the tumorigenesis, by binding selectively to poly-U elements and AU-rich elements (AREs) in the 3'-UTR of target mRNAs for post-transcriptional regulation (Bakheet, Hitti et al. 2018).
The ELAVL1 gene located in chromosome 19p13.2 (Ma and Furneaux 1997) has been implicated in the occurrence and development of various human cancers. Although, abundant literature has highlighted its oncogenic effects (López de Silanes, Lal et al. 2005, Li, Huang et al. 2020, Ni, He et al. 2020, Palomo-Irigoyen, Pérez-Andrés et al. 2020).
Fang Xue’s study indicated that miRNA-139-3p inhibited the progression of ovarian cancer cells via inhibiting the expression of ELAVL1 (Xue, Li et al. 2019).
A previous study of Ming-Jun Fan and his colleagues observed that ELAVL1 was upregulated in cervical cancer cells and was reported to promote cancer cell growth through regulating RNA in the cell cytoplasm (Fan, He et al. 2020).
The present study investigated a possible association between the ELAVL1 gene SNPs and the risk of cervical cancer among Tunisian women.
The investigated SNPs were genotyped according to the difference in melting curves established by HRM. This method of post-PCR is used for identifying genetic variants in suitable regions of interest in our candidate gene.
As a result of this case-control study, no association was found between the ELAVL1 gene SNPs (rs14394, rs35986520, rs1298524 and rs2042920) and the risk of developing cervical cancer. Conversely, women carrying ELAVL1 gene SNPs (rs12983784, rs74369359 and rs10402477) have a high risk for this disease.
Rohit Upadhyay’s report indicated that according to db SNP (https://www.ncbi.nlm.nih.gov/snp/) the ELAVL1 gene has more than 400 SNPs, most of them have less than 5% MAF (Minor allele frequency). By contrast, the selected SNPs had a MAF that is superior to 5% and therefore chosen for our study (Upadhyay, Sanduja et al. 2013).
A study of Rothamel and al. showed that 3’UTR binding confers enrichment and transcript stability and demonstrated that ELAVL1 mediates the RNA stability of genes that regulate pathways essential to pathogen sensing and cytokine production (Wanke, Devanna et al. 2018).
Multiple diseases arising from anomalies in this region affect the expression of one or more genes, especially cancer.
According to previous studies and to our findings, the possible explanation is that ELAVL1 single nucleotide polymorphisms in the 3’UTR region can be in the AU-rich region, which leads to dysregulation of ARE-binding proteins and cause tumorigenesis. Thus, women with ELAVL1 gene SNPs rs12983784, rs74369359 and rs10402477, which are, located in the 3’UTR region, presented high risqué of cervical cancer disease.
In this study, we assessed the association between rs35986520 and rs2042920 SNPs and between rs2042920 and rs10402477 SNPs, using a haplotype-based case–control analysis. The rs10402477 was significantly different between cervical cancer patients and control participants, indicating that the risk of this cancer is increased among women with the T allele of rs10402477 and women with the C allele of the SNP rs12983784. A study of Morris and Kaplan indicated that when linkage disequilibria between SNPs, multiple susceptibility alleles, is weak, an analysis based on haplotypes has advantages over analysis based on individual SNPs (Morris and Kaplan 2002). Consequently, we established haplotypes for the ELAVL1 gene from the different combinations of the seven SNPs. The frequencies of the “C C G G C A G”, “T T G G T A T” and “T T T G C A T” were associated with a significant increased risk for cervical cancer. However, the “TCGACAT” and the “TTGGCAT” frequencies were associated with a decreased risk for cervical cancer.
rs2042920, which was in strong LD with rs10402477, was reported to be associated with increased cervical cancer risk in the Tunisian population. Although this study suggested that rs2042920 had no impact on cervical cancer risk in Tunisian women, only its association with the rs10402477 SNP can lead to a rise in cancer risk. As rs10402477 SNP was uniquely higher in patients compared with control subjects, it is obvious that this SNP is a genetic risk factor for cervical cancer among Tunisian women.
The same results were obtained for rs35986520, which was in strong LD with rs2042920; no significant association was seen with cervical cancer in Tunisian participants.
A possible explanation for the observed results is a possible functional combination of SNP alleles that could alter the ELAVL1 function. The presence of several simultaneous SNPs could alter more the interaction between ELAVL1 and AREs.
In summary, the current study detected the genotypes of patients with cervical cancer and healthy controls in a Tunisian population using the HRM. A significant association was observed between the ELAVL1 gene SNPs (rs12983784, rs74369359 and rs10402477) and the risk of cervical cancer. Also, Haplotype consisting of the two SNPs rs2042920 and rs10402477 strengthened the association with this cancer susceptibility. This finding provides evidence that ELAVL1 gene SNPs may be applied as a promising marker of genetic susceptibility to cervical cancer in Tunisian population.
Additional studies can confirm our results of genetic variation in ELAVL1 as a novel prognostic marker and therapeutic target of cervical cancer.
Nevertheless, the low sample size is a limitation of our study. Therefore, enlarging our sample size and providing more clinical analysis should be considered in the future to confirm this study finding.