Association of HLA-G +3142 C>G polymorphism and breast cancer in Tunisian population

Associations of HLA-G 3'UTR polymorphisms and increased HLA-G expression with gastric cancer susceptibility and prognosis

BACKGROUND

Gastric cancer (GC) remains a serious health concern and is characterized by a multifactorial etiology involving both genetic and epigenetic factors. The aim of the current study was to examine the relationship between Human leukocyte antigen (HLA)-G 3'UTR polymorphisms and the expression of HLA-G in both tumor tissues and plasma samples from patients with GC in the Tunisian population.

METHODS

HLA-G 3'UTR polymorphisms (14pb Insertion/deletion and + 3142C/G) were identified by polymerase chain reaction (PCR) or Sanger sequencing. Plasma levels of sHLA-G (total sHLA-G, shed HLA-G1 and HLA-G5) were determined. Immunohistochemistry was used to evaluate the expression of HLA-G in tumor tissues.

RESULTS

The Del/Del genotype and Del allele frequencies were different between GC patients and healthy donors (HD) (OR [95 % CI] = 2.483 [1.070-5.410], p = 0.025 vs. OR [95 % CI] = 1.537 [0.924-2.584], p = 0.099; respectively). The C/C genotype and C allele frequencies were significantly greater in GC patients than in HD (OR [95 % CI] = 2.269[0.1.070-4.904], p = 0.033 vs. OR [95 % CI] = 1.746[1.045-2.878], p = 0.034; respectively). Interestingly, the Del/Del genotype and Del allele were significantly associated with an increased risk of GC in patients aged ≥55 years at diagnosis. HLA-G was highly expressed in GC tissues, particularly in tissues with advanced tumor invasion (T3 + T4). Compared with HD, GC patients had higher soluble HLA-G, shed HLA-G1 and HLA-G5 levels (Mann-Whitney: p = 0.001, p = 0.001 and p = 0.643, respectively). Assessment of patients' survival by Kaplan-Meier analysis indicated that the Del allele was significantly associated with reduced overall survival (OS) in GC patients at advanced stages III + IV (p = 0.043).

CONCLUSIONS

These results suggest that HLA-G 3'UTR polymorphisms are associated with GC susceptibility in Tunisian population. The expression of HLA-G in both the tissue and plasma may play an important role in the development and progression of GC. Therefore, the current study supported the recommendation of investigating HLA-G 3'UTR polymorphisms in GC and indicated that HLA-G molecules could serve as promising therapeutic targets in GC.

HLA-G - evolvement from a trophoblast specific marker to a checkpoint molecule in cancer, a narrative review about the specific role in breast- and gynecological cancer

Human leukocyte antigen G (HLA-G) is known as a non-classical molecule of the major histocompatibility complex class Ib and downregulates the mother's immune response against the fetus during pregnancy, thereby generating immune tolerance. Due to the latter effect, HLA-G is also referred to as an immune checkpoint molecule. Originally identified on extravillous trophoblasts, HLA-G is already known to induce immune tolerance at various stages of the immune response, for example through cell differentiation and proliferation, cytolysis and cytokine secretion. Because of these functions, HLA-G is involved in various processes of cancer progression, but a comprehensive review of the role of HLA-G in gynecologic cancers is lacking. Therefore, this review focuses on the existing knowledge of HLA-G in ovarian cancer, endometrial cancer, cervical cancer and breast cancer. HLA-G is predominantly expressed in cancer tissues adjacent to the extravillous trophoblast. Therefore, modulating its expression in the cancer target tissues of cancer patients could be a potential therapeutic approach to treat these diseases.

The 14-bp insertion/deletion as a promising gene polymorphism to understand cancer risk: Evidence from a systematic review and comprehensive meta-analysis

Background

HLA-G is associated with cancer cell escape. The 3'UTR polymorphism is involved in the regulation of membrane-bound HLA-G and soluble HLA-G proteins. The aim of our study was to assess the association of the HLA-G 14-bp insertion (I)/deletion (D) polymorphism with cancer susceptibility and its interaction with clinicopathological features and environmental factors.

Methods

A meta-analysis was performed to investigate the association between the HLA-G 14-bp I/D polymorphism and different types of cancers according to the Prisma guidelines.

Results

Thirty-nine publications that studied the 14-bp I/D polymorphism in cancers met our inclusion criteria. The findings of the meta-analysis showed a significant association between the 14-bp I/D polymorphism and cancer risk under the allelic contrast model D vs. I (OR = 1,112, 95 % CI = 1,009-1,227; P = 0,033) suggesting that the D allele was a risk factor for cancer susceptibility. Stratification by cancer type demonstrated a significant association of the 14-bp I/D polymorphism with breast cancer under the D vs. I contrast allele model (OR = 1,267, 95 % CI = 1,028-1,563; P = 0,027). No significant association was found for digestive, cervical, haematological and thyroid cancers. A comparison of groups stratified by ethnicity showed a significant association for Caucasians under the D vs. I model (OR = 1,147, 95 % CI = 1,002-1,313; P = 0,047); and for mixed ethnicities under the DD + DI vs. II (OR = 1,388, 95 % CI = 1,083-1,780; P = 0,010) and DI vs. II (OR = 1,402, 95 % CI = 1,077-1,824; P = 0,012) models. A comparison of cancer risks associated with the 14-bp I/D polymorphism according to geographic location revealed significant risks for the D allele and DD genotype in North Africa, the Middle East and South America. However, no significant susceptibility to cancer associated with the 14-bp I/D polymorphism was shown for Europe and North Asia. The findings of a meta-analysis of subgroups by disease stage showed a significant association in both early and advanced stages, with the 14-bp deletion variant being a risk factor. Similarly, a significant cancer risk was shown for the 14-bp deletion variant in both low- and high-grade cancers. Finally, the risk associated with the 14-bp I/D polymorphism was higher in cancers with concomitant viral infection with human papillomavirus (HPV), hepatitis B virus (HBV) or hepatitis C virus (HCV).

Conclusion

The findings of the overall meta-analysis showed a significant association between the HLA-G 14-bp I/D polymorphism and cancer susceptibility. The findings stratified analysis and subgroup comparisons showed that the 14-bp I/D deletion variant was associated with an increased risk of breast cancer. The HLA-G 14-bp I/D polymorphism may interact with individual and clinicopathological factors to alter cancer risk. These promising findings for cancer risk provide the basis for further studies that explore 14bp I/D polymorphism in cancer screening and immunotherapeutic approach.

3'UTR-HLA-G polymorphisms and circulating sHLA-G are associated with breast cancer: Evidence from a meta-analysis

BACKGROUND

Human leukocyte antigen-G (HLA-G) gene polymorphisms and circulating sHLA-G have often been linked to the risk of breast cancer (BC). However, the results remain controversial. To resolve this issue, we performed a meta-analysis of HLA-G gene polymorphisms and sHLA-G levels in BC.

METHODS

We performed a meta-analysis on the association of HLA-G 14-bp Insertion/Deletion (Ins/Del) and HLA-G +3142 C/G polymorphisms with BC as well as the relationship between sHLA-G and the disease outcome.

RESULTS

Pooled analysis showed a statistically significant association between the HLA-G 14-bp Ins/Del polymorphism and BC susceptibility for the overall population and for Caucasians. The Del allele and genotypes with at least one copy of the Del allele presented significant risks for BC. For HLA-G +3142 C/G polymorphism, the G allele significantly decreased the risk of BC for the overall population and for Caucasians, indicating that the G allele was a protective factor against BC and that the C allele was a significant risk factor for BC. The meta-analysis revealed a significantly increased level of sHLA-G patients with BC compared to the control group for the overall population, Caucasians and Asians.

CONCLUSION

The present meta-analysis showed a major association of both HLA-G 14-bp Ins/Del and +3142 C/G polymorphisms with BC susceptibility, suggesting Del and C variants as highly significant risk factors for BC. The present study also showed significantly higher sHLA-G levels in patients with BC compared to healthy controls. Our pooled results suggested a critical role of HLA-G in BC, thereby providing evidence to use HLA-G as a biomarker and a therapeutic tool.

Roles of HLA-G/KIR2DL4 in Breast Cancer Immune Microenvironment

Human leukocyte antigen (HLA)-G is a nonclassical MHC Class I molecule, which was initially reported as a mediator of immune tolerance when expressed in extravillous trophoblast cells at the maternal-fetal interface. HLA-G is the only known ligand of killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4), an atypical family molecule that is widely expressed on the surface of NK cells. Unlike other KIR receptors, KIR2DL4 contains both an arginine-tyrosine activation motif in its transmembrane region and an immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytoplasmic tail, suggesting that KIR2DL4 may function as an activating or inhibitory receptor. The immunosuppressive microenvironment exemplified by a rewired cytokine network and upregulated immune checkpoint proteins is a hallmark of advanced and therapy-refractory tumors. Accumulating evidence has shown that HLA-G is an immune checkpoint molecule with specific relevance in cancer immune escape, although the role of HLA-G/KIR2DL4 in antitumor immunity is still uncharacterized. Our previous study had shown that HLA-G was a pivotal mediator of breast cancer resistance to trastuzumab, and blockade of the HLA-G/KIR2DL4 interaction can resensitize breast cancer to trastuzumab treatment. In this review, we aim to summarize and discuss the role of HLA-G/KIR2DL4 in the immune microenvironment of breast cancer. A better understanding of HLA-G is beneficial to identifying novel biomarker(s) for breast cancer, which is important for precision diagnosis and prognostic assessment. In addition, it is also necessary to unravel the mechanisms underlying HLA-G/KIR2DL4 regulation of the immune microenvironment in breast cancer, hopefully providing a rationale for combined HLA-G and immune checkpoints targeting for the effective treatment of breast cancer.

HLA-G: Too Much or Too Little? Role in Cancer and Autoimmune Disease

HLA-G is a non-classical HLA class I molecule with immunomodulatory properties. It was initially described at the maternal-fetal interface, and it was later found that this molecule was constitutively expressed on certain immuneprivileged tissues, such as cornea, endothelial and erythroid precursors, and thymus. The immunosuppressive effect of HLA-G is exerted through the interaction with its cognate receptors, expressed on immunocompetent cells, like ILT2, expressed on NK, B, T cells and APCs; ILT4, on APCs; KIR, found on the surface of NK cells; and finally, the co-receptor CD8. Because of these immunomodulatory functions, HLA-G has been involved in several processes, amongst which organ transplantation, viral infections, cancer progression, and autoimmunity. HLA-G neo-expression on tumors has been recently described in several types of malignancies. In fact, tumor progression is tightly linked to the presence of the molecule, as it exerts its tolerogenic function, inhibiting the cells of the immune system and favoring tumor escape. Several polymorphisms in the 3'UTR region condition changes in HLA-G expression (14bp and +3142C/G, among others), which have been associated with both the development and outcome of patients with different tumor types. Also, in recent years, several studies have shown that HLA-G plays an important role in the control of autoimmune diseases. The ability of HLA-G to limit the progression of these diseases has been confirmed and, in fact, levels of the molecule and several of its polymorphisms have been associated with increased susceptibility to the development of autoimmune diseases, as well as increased disease severity. Thus, modulating HLA-G expression in target tissues of oncology patients or patients with autoimmune diseases may be potential therapeutic approaches to treat these pathological conditions.

Association of HLA-G 3'UTR polymorphisms and haplotypes with colorectal cancer susceptibility and prognosis

Human leukocyte antigen (HLA)-G has been considered as an immune modulator in several types of cancers. Its genetic polymorphisms may potentially affect the risk of developing colorectal cancer (CRC). The overall purpose of this study was to analyze the implication of HLA-G 3'untranslated region (3'UTR) polymorphisms particularly 14 pb insertion/deletion (Ins/Del; rs371194629) and + 3142C/G (rs1063320) in CRC susceptibility and progression. A comparative analysis between patients (N = 233) and controls (N = 241) demonstrated that Del allele (Odds Ratios (OR) = 1.41, 95% CI = 1.091-1.819, p = 0.008), the homozygous Del/Del genotype (OR = 1.80, 95% CI = 1.205-2.664, p = 0.003) and the codominant C/G genotype (OR = 1.59, 95% CI = 1.106-2.272, p = 0.013) were associated to CRC risk. As expected, the DelG haplotype was associated with CRC susceptibility (OR = 1.47, 95% CI = 1.068-2.012, p = 0.018). Assessment of patients' survival by Kaplan-Meier analysis indicated that the Del allele and the homozygous Del/Del genotype were associated with reduced event free survival (EFS) (Respectively, p = 0.009 and p = 0.05). Interestingly, the Del allele and the homozygous Del/Del genotype have been revealed as independent prognostic factors for poor EFS in patients with CRC. Additionally, haplotypes analysis revealed that DelG haplotype was linked with significant increase in CRC risk (log-rank; EFS: p = 0.02). Inversely, the InsC haplotype was associated with a significant reduced CRC risk (log-rank; Overall survival (OS): p < 10^-6; EFS: p = 0.01). Multivariate Cox regression analysis revealed that the InsC haplotype was independently associated with significantly longer EFS (p = 0.021, HR = 0.636, 95% CI = 0.433-0.935). These findings support the implication of HLA-G polymorphisms in the CRC susceptibility suggesting HLA-G as a potent prognostic and predictive indicator for CRC. Insight into mechanisms underlying HLA-G polymorphisms could allow for the development of targeted care for CRC patients according to their genetic profile.

Rapid high-resolution melting method to identify human leukocyte antigen-G (HLA-G) 3' untranslated region polymorphism +3142C/G (rs1063320)

Background

HLA‐G is a non‐classical class I gene of the human Major Histocompatibility encoding molecules with immune‐modulatory properties. Expression of HLA‐G is being largely studied in pathological conditions, such as tumors, viral infections, inflammation, and autoimmune diseases, grafted tissues, among others. HLA‐G +3142C/G (rs1063320: dbSNP database) polymorphism is located in 3′ UTR of HAL‐G and plays a key role in determining the magnitude of gene and protein expression. The detection of HLA‐G +3142C/G polymorphism in the most published report is done through polymerase chain reaction followed by enzymatic digestion. Therefore, it is so interesting to develop a rapid and sensitive assay to genotype HLA‐G +3142C/G polymorphism. High‐resolution melt analysis (HRM) is a technology that is based on the analysis of the melting profile of PCR products through gradual temperature increase. The aim of this work is to apply high‐resolution melt method for genotyping the HLA‐G +3142C/G polymorphism.

Methods

DNA from 118 individuals was extracted from whole blood with QIAamp^® DNA blood mini kit (Qiagen, Germany). Primer couple was designed using Primer 3 online tools so as to have only one SNP in the target sequence for high HRM efficiency. Positive Controls were identified using DNA sequencing and used as reference when assigning genotypes for trial samples.

Results

We were able to recognize the three genotypes with similar accuracy than DNA sequencing using high resolution melting method. Hardy‐Weinberg equilibrium test shows that our population is in equilibrium for the studied SNP. Genotypes frequencies of +3142C/G polymorphism in Tunisian general population are 0.475 for heterozygote G/C, 0.186 for homozygote G/G and 0.339 for homozygote C/C.

Conclusion

HRM is a cost‐effective method suitable for SNP genotyping.

HLA-G and single nucleotide polymorphism (SNP) associations with cancer in African populations: Implications in personal medicine

The immune system plays an important role in protecting the body against malignancy. During cancer immunoediting, the immune system can recognize and keep checking the tumor cells by down-expression of some self-molecules or by increasing expression of some novel molecules. However, the microenvironment created in the course of cancer development hampers the immune ability to recognize and destroy the transforming cells. Human Leukocyte Antigen G (HLA-G) is emerging as immune checkpoint molecule produced more by cancer cells to weaken the immune response against them. HLA-G is a non-classical HLA class I molecule which is normally expressed in immune privileged tissues as a soluble or membrane-bound protein. HLA-G locus is highly polymorphic in the non-coding 3′ untranslated region (UTR) and in the 5′ upstream regulatory region (5′ URR). HLA-G expression is controlled by polymorphisms located in these regions, and several association studies between these polymorphic sites and disease predisposition, response to therapy, and/or HLA-G protein expression have been reported. Various polymorphisms are demonstrated to modulate its expression and this is increasingly finding more significance in cancer biology. This review focuses on the relevance of the HLA-G gene and its polymorphisms in cancer development. We highlight population genetics of HLA-G as evidence to espouse the need and importance of exploring potential utility of HLA-G in cancer diagnosis, prognosis and immunotherapy in the currently understudied African population.

A Review of Cancer Genetics and Genomics Studies in Africa

Cancer is the second leading cause of death globally and is projected to overtake infectious disease as the leading cause of mortality in Africa within the next two decades. Cancer is a group of genomic diseases that presents with intra- and inter-population unique phenotypes, with Black populations having the burden of morbidity and mortality for most types. At large, the prevention and treatment of cancers have been propelled by the understanding of the genetic make-up of the disease of mostly non-African populations. By the same token, there is a wide knowledge gap in understanding the underlying genetic causes of, and genomic alterations associated with, cancer among black Africans. Accordingly, we performed a review of the literature to survey existing studies on cancer genetics/genomics and curated findings pertaining to publications across multiple cancer types conducted on African populations. We used PubMed MeSH terms to retrieve the relevant publications from 1990 to December 2019. The metadata of these publications were extracted using R text mining packages: RISmed and Pubmed.mineR. The data showed that only 0.329% of cancer publications globally were on Africa, and only 0.016% were on cancer genetics/genomics from Africa. Although the most prevalent cancers in Africa are cancers of the breast, cervix, uterus, and prostate, publications representing breast, colorectal, liver, and blood cancers were the most frequent in our review. The most frequently reported cancer genes were BRCA1, BRCA2, and TP53. Next, the genes reported in the reviewed publications’ abstracts were extracted and annotated into three gene ontology classes. Genes in the cellular component class were mostly associated with cell part and organelle part, while those in biological process and molecular function classes were mainly associated with cell process, biological regulation, and binding, and catalytic activity, respectively. Overall, this review highlights the paucity of research on cancer genomics on African populations, identified gaps, and discussed the need for concerted efforts to encourage more research on cancer genomics in Africa.

HLA-G 14 bp In/Del and +3142 C/G genotypes are differentially expressed between patients with grade IV gliomas and controls

Aim: Human Leukocyte Antigen-G (HLA-G) is a non-classical class I molecule that is involved in maternal-fetal immunotolerance. In cancer, this molecule contributes to the tumor escape. The aim of this study was to evaluate the 14 bp In/Del and +3142 C > G polymorphisms of the HLA-G 3' UTR and its relation with plasma and tissue HLA-G expression in patients with grade IV (high-grade) and grade I/II (low-grade) gliomas and controls.Patients and methods: Peripheral blood and tumor biopsies were collected from 85 patients with gliomas and blood samples from 94 controls. Polymorphisms were analyzed from blood DNA. Soluble HLA-G (sHLA-G) was measured by ELISA in plasma of the subjects and the tissue expression by immunohistochemistry on patient's tissue.Results: Higher levels of sHLA-G were observed in grade IV gliomas patients than in controls (p < 0.0001). In grade IV patients, the heterozygous 14pb In/Del, +3142 C/G genotypes and Del/C*In/G haplotype were associated with higher sHLA-G levels (p < 0.0001) when compared with controls. GBM patients were stratified into high and low sHLA-G expression and an association was found between +3142 C allele and high sHLA-G plasmatic levels (p = 0.0095). Tissue HLA-G immunolabel was higher in high-grade than low-grade gliomas (p = 0.0033).Conclusion: This was the first study evaluating HLA-G 3' UTR polymorphisms and expression in patients with gliomas. The 14 bp In/Del and +3142 C/G genotypes and haplotypes showed high influence over sHLA-G expression, suggesting a heterozygous advantage in the tumor context and may contribute to a worse prognosis in glioma patients.

Association of HLA-G 3'UTR 14-bp Ins/Del polymorphism with breast cancer among South Indian women

AIM

Human leucocyte antigen-G (HLA-G) and tumour necrosis factor-alpha (TNF-α) are potent immune mediators implicated in the pathogenesis of breast cancer. The polymorphisms in the 3' untranslated region (3'UTR) of HLA-G and promoter region of TNF-α are well known to influence their expression levels and may consequently contribute to varied disease predisposition. Therefore, in the present study, we explored the effect of HLA-G 3'UTR (14-bp Ins/Del and +3142 C/G) and TNF-α promoter (-238 G/A and -308 G/A) polymorphisms on breast cancer risk among South Indian women.

METHODS

A total of 342 women (100 patients with breast cancer, 142 patients with benign breast disorder and 100 healthy women volunteers) were enrolled for this study. Genotyping of HLA-G and TNF-α polymorphisms were performed by direct PCR DNA amplification and amplification refractory mutation system PCR methods, respectively.

RESULTS

Significantly higher frequencies of HLA-G 14-bp Ins allele and Ins/+3142G haplotype were observed in patients with breast cancer than healthy controls (OR=1.56, P_c=0.036) and patients with benign breast disorder (OR=1.47, P_c=0.046). Similarly, subgroup analysis based on age at diagnosis (age≤50 years and >50 years) of breast cancer revealed higher frequencies of 14-bp Ins allele and Ins/+3142G haplotype in the patients of age >50 years than healthy controls (OR=1.77, P_c=0.03). Additionally, the extended haplotypes and multifactor dimensionality reduction analysis of the studied polymorphisms revealed significant contribution of HLA-G 14-bp Ins/Del polymorphism towards breast cancer risk.

CONCLUSION

The findings of the present study suggest that the HLA-G 14-bp Ins/Del polymorphism could influence breast cancer pathogenesis among South Indian women.

The Impact of HLA-G 3'UTR Polymorphisms in Breast Cancer in a Tunisian Population

Human leukocyte antigens G and E (HLA-G and HLA-E) are nonclassical major histocompatibility complex (MHC) class I molecules. These molecules play an important role in immune surveillance by inhibiting natural killer and cytotoxic T cells responsible for immune escape. The expression of HLA-G and HLA-E has been associated with several diseases including tumor. The main objective of the study is to evaluate the impact of three HLA-G 3'UTR potential polymorphisms: +3187 A > G (rs9380142), +3142 G > C (rs1063320), +2960 14-base pair (bp) Insertion/Deletion (Ins/Del) (rs66554220), and the HLA-E*01:01/01:03 A > G (rs1264457) polymorphism in Tunisian breast cancer population. A total of 355 patients and 381 controls were genotyping for HLA-G and HLA-E polymorphisms using a Taq Man assay. +3142 C allele and +3142 C/C genotype were significantly associated with increased risk of breast cancer (p = 0.00002; OR = 1.58; 95% CI = 27-1.97) (49% versus 35%; p = 0.0001; OR = 1.79; 95% CI = 1.32-2.44). In addition, Del allele and the homozygous state for Del/Del genotype confer a risk for breast cancer (52% versus 45%, p = 0.006; OR = 1.33, 95% CI = 1.08-1.64) (28% versus 22%, p = 0.039; OR = 1.43, 95% CI = 0.90-2.25). However, no statistical significant differences were reported for HLA-G + 3187 A > G and HLA-E variations and breast cancer in a Tunisian population. The found results indicate that HLA-G may play an important role in the breast cancer.

HLA-G +3142 C>G polymorphism and cancer risk: Evidence from a meta-analysis and trial sequential analysis

BACKGROUND

Human leukocyte antigen-G (HLA-G) plays an important role in the development of human cancers. Several published studies have investigated the relationship between the HLA-G +3142 C>G (rs1063320) polymorphism and cancer susceptibility in different populations. However, the results have yet to reach a consensus in different types of cancers. Therefore, we performed a meta-analysis to evaluate the effect of the HLA-G +3142 C>G polymorphism on cancer risk.

METHODS

A systematic literature search was performed in PubMed, Web of Science, CNKI, VIP, and Wanfang databases to acquire eligible studies up to February 20, 2019. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to assess the correlation between the HLA-G +3142 C>G polymorphism and cancer risk in a fixed-effects or random-effects model. Publication bias assessments, sensitivity analysis and stratified analyses were performed. To reduce the risk of type I error and assess whether the present evidence of the results was adequate and conclusive, trial sequential analysis (TSA) was also performed.

RESULTS

Eight case-control studies comprising 1546 cases and 1595 controls were included in the present meta-analysis. The results revealed that the HLA-G +3142 C>G mutation significantly decreased the total cancer risk in recessive comparison model and allelic comparison model. Further stratified analyses showed that the HLA-G +3142 C>G mutation significantly decreases the risk of cancer in Asian populations. No similar relationship was found in other subgroups. No publication bias was identified in our present study. Omitting a single study at a time had no significant impact on the pooled OR of the sensitivity analysis assessing the association between the HLA-G +3142 C>G polymorphism and cancer risk, which demonstrates the stability of the current meta-analysis. TSA also identified our current findings.

CONCLUSIONS

The results of our meta-analysis show that the HLA-G +3142 C>G polymorphism plays a protect role in the occurrence of human cancers, particularly in Asian populations. More case-control studies with different types of cancer in various ethnicities are needed to verify the findings.

Genetic variation in the HLA-G 3'UTR 14-bp insertion/deletion and the associated cancer risk: evidence from 25 case-control studies

Human leucocyte antigen-G (HLA-G) plays an important role in the progression of human cancers. A growing number of published studies have investigated the correlation between the HLA-G 3' untranslated region (3'UTR) 14-bp insertion/deletion (Ins/Del) polymorphism and the associated cancer risk in different populations. However, results from previous studies are inconclusive and inconsistent for the different type of cancers. Therefore, we undertook a meta-analysis to assess the effects of the HLA-G 14-bp Ins/Del polymorphism on cancer risk. A systematic literature search was conducted in PubMed, Web of Science, CNKI, VIP, and Wanfang databases to obtain relevant studies up to 28 January 2019. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used. Twenty-five published case-control studies comprising 4981 cases and 6391 controls were included in the current meta-analysis. The results of the overall analysis revealed that the HLA-G 14-bp Ins/Ins genotype and Ins allele were associated with the total cancer risk in the homozygote comparison model (Ins/Ins vs. Del/Del: OR = 0.80, CI = 0.64-1.00; P=0.049) and the allelic comparison model (Ins vs. Del: OR = 0.89, CI = 0.81-0.99; P=0.035), with a protective role. Further subgroup analyses indicated that the HLA-G 14-bp Ins/Del polymorphism was associated with the risk of breast cancer and oesophageal cancer (EC), and significant risk of cancer was also observed in Mixed populations and population-based (PB). The results of our meta-analysis show that the HLA-G 14-bp Ins/Del polymorphism plays an important role in cancer risk, particularly in breast cancer and esophageal cancer in Mixed populations. Additional case-control studies with different types of cancer spanning different ethnicities are needed to extend the present findings.

Genetic association between HLA-G 14-bp polymorphism and diseases: A systematic review and meta-analysis

BACKGROUND

HLA-G is an immune checkpoint molecule. Since a differential molecule expression has been reported even for healthy individuals, many studies have focused on polymorphisms at HLA-G regulatory regions, particularly the 3' untranslated region (3'UTR). The presence/absence of a 14-bp sequence was the first polymorphism described and it is the most studied in association between HLA-G and disorders.

METHODS

In this study, we performed a systematic review and meta-analysis of all association studies published regarding the HLA-G 14-bp.

RESULTS

We verified association between 14-bp alleles and diseases in the following situations: (1) presence of 14-bp (insertion) conferred susceptibility to preeclampsia (child alleles evaluated) and systemic lupus erythematosus (OR = 1.42; 95%CI = 1.04-1.93; p = 0.026 and OR = 1.13; 95%CI = 1.01-1.27, p = 0.028); (2) 14-bp absence (deletion) was associated with increased risk to breast cancer (OR = 1.23; 95%CI = 1.06-1.43; p = 0.006) and human Cytomegalovirus infection (OR = 2.06; 95%CI = 1.60-2.64; p < 0.0001); and (3) a risk association was observed between the group of reproductive disorders and the 14-bp insertion (OR = 1.12; 95%CI = 1.01-1.24; p = 0.034).

CONCLUSIONS

Considering that others 14-bp associations were inconclusive and that other variation sites observed at HLA-G 3'UTR exhibit a proven role on post-transcriptional regulation of HLA-G expression, the complete 3'UTR segment should be analyzed in terms of disease susceptibility, instead of a single polymorphism.