HLA-G 3'UTR polymorphism diplotypes and soluble HLA-G plasma levels impact cervical cancer susceptibility and prognosis

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.

Influence of HLA-G 3' Untranslated Region Haplotypes and SNP +3422 Gene Variants as Host Genetic Factors on the Outcomes of SARS-CoV-2 Infection During Acute and Post-Acute Phases in a German Cohort

HLA-G, an important immune-checkpoint (IC) molecule that exerts inhibitory signalling on immune effector cells, has been suggested to represent a key player in regulating the immune response to Severe Acute Respiratory Syndrome Coronavirus Type 2 (SARS-CoV-2). Since specific single-nucleotide polymorphisms (SNP) in the HLA-G 3'untranslated region (UTR), which arrange as haplotypes, are crucial for the regulation of HLA-G expression, we analysed the contribution of these genetic variants as host factors in SARS-CoV-2 infection during acute and post-acute phases. HLA-G gene polymorphisms in the 3'UTR were investigated by sequencing in an unvaccinated Coronavirus Disease 2019 (COVID-19) cohort during acute SARS-CoV-2 infection (N = 505) and in the post-acute phase (N = 253). The HLA-G 3'UTR haplotype known as UTR-3 (p = 0.002) and the variant rs17875408 (also known as +3422) T variant (p = 0.004) are independent prognostic risk factors for fatal COVID-19. The +3422T variant (p = 0.006) predicted also the early loss of neutralising SARS-CoV-2 antibodies. In addition, the HLA-G 3'UTR haplotype UTR-7 (p = 0.023) emerged as an independent prognostic factor for increased susceptibility to Long-COVID symptoms after SARS-CoV-2 infection. Our study highlights that due to the variability of the 3'UTR genetic background, HLA-G has the potential to contribute to the progression of SARS-CoV-2 infection, extending to the development of Long-COVID symptoms, despite the likely alterations in the microenvironment and associated HLA-G-specific regulatory elements over the course of the disease. By spotlighting HLA-G, the importance of the genetic background of IC and their pivotal role in modulating immune responses during and after COVID-19 are emphasised.

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.

Association of HLA-G Expression, Its Genetic Variants and Related Neuro-Immunomodulation with Characteristics of Bladder Carcinoma

BACKGROUND

Human leukocyte antigen G (HLA-G) is an immune checkpoint molecule with immunosuppressive and anti-inflammatory activities. It belongs to class I non-classical major histocompatibility complex molecules and has been upregulated in various cancer types. In bladder cancer (BC) tumors, the association of HLA-G with cancer progression has to be explained.

METHODS

A total of 89 BC patients and 74 control subjects were genotyped for the HLA-G 14 bp ins/del polymorphism. In urine cell samples, HLA-G mRNA expression was analyzed using real-time PCR. Soluble HLA-G (sHLA-G) serum levels were measured by ELISA. The associations between the HLA-G 14 bp ins/del polymorphism, HLA-G mRNA expression, and/or sHLA-G levels and selected variables including tumor grade, disease stage, body mass index, and heart rate variability (HRV) parameters were evaluated.

RESULTS

The protective HLA-G 14 bp ins/ins genotype under the recessive genetic model was associated with lower HLA-G mRNA expression in the BC group (p = 0.049). Significantly higher HLA-G mRNA expression was detected in patients with pT2 + pT3 as compared to those with pTa + pT1 stages (p = 0.0436). Furthermore, higher HLA-G mRNA expression was observed in high-grade muscle-infiltrating BC (MIBC) than in the low-grade non-MIBC group (p = 0.0365). Patients with a level of sHLA-G above 29 U/mL had shorter disease-free survival than patients with lower sHLA-G levels. Furthermore, the opposite HRV correlations with sHLA-G levels in BC patients as compared to controls probably reflect the different roles of HLA-G in health and cancer.

CONCLUSIONS

Our results suggest the impact of the HLA-G 14 bp ins/del variant, HLA-G expression, and autonomic nervous system imbalance on advanced stages of BC.

Ralationship between polymorphisms and diplotypes of HLA-G 3'UTR and fetuses with abnormal chromosomes or unexplained pregnancy loss (UPL)

OBJECTIVES

Human leukocyte antigen G (HLA-G) plays a crucial role in pregnancy. Pregnancy loss (PL) is caused by a variety of causes, such as fetal chromosomal abnormalities, maternal hypertension and diabetes, immune causes, spontaneous immune diseases, infections, unknown causes, etc. This study reports on the association of fetal HLA-G 3'UTR polymorphisms and diplotypes with chromosomally abnormal fetuses (CAF) or unexplained pregnancy loss (UPL).

METHODS

A total of 552 specimens were collected and grouped by next-generation sequencing technology (NGS) and fetal survival: UPL (112 cases), CAF (170 cases) and control (258 cases). The polymorphisms of HLA-G 3'UTR in all samples were detected by Sanger sequencing. The genotypes, haplotypes and diplotypes of HLA-G 3'UTR were analyzed. The classification and regression tree (CART) analysis was used to evaluate the role of HLA-G diplotypes in predicting fetal outcomes. The correlations between CAF or UPL and maternal age, paternal age, times of miscarrage, times of delivery were analyzed by logistic regression.

RESULTS

The frequencies of HLA-G + 2960del/del and + 3035CC genotypes were remarkablly increased in CAF than those in control group. The frequencies of HLA-G + 2960ins/del, + 3010CC, + 3035TC, + 3142GG, + 3187AA in CAF were significantly lower than those in normal fetuses. Through genetic models and logistic regression analysis, the dominant model of HLA-G 3'UTR genotypes [such as + 2960 (OR = 1.27, 95% CI = 1.05-1.54, p = 0.016), + 3010 (OR = 0.78, 95% CI = 0.63-0.97, p = 0.026), + 3035 (OR = 1.22, 95% CI = 1.00-1.49, p = 0.047), + 3142 (OR = 0.76, 95% CI = 0.62-0.95, p = 0.014) and + 3187 (OR = 0.80, 95% CI = 0.65-0.99, p = 0.041)] were dramatically associated with CAF. However, the frequencies of HLA-G + 3010GC, + 3142GC and + 3187AG in fetuses with UPL were memorably decreased than those in normal fetuses. No significant difference was found in the frequencies of HLA-G haplotypes in all groups. However, the frequency of UTR-1 positive specimens in CAF was significantly higher than that in UPL and control group. At the same time, the frequency of UTR-1/UTR-3 diplotypes in CAF was observably higher than that in UPL and control group, while the UTR-1/UTR-7 frequency in UPL was signally lower than that in control group. Multivariate logistic regression analysis indicated that positive HLA-G UTR-1 (OR = 1.8, 95% CI = 1.16-2.81, p = 0.009), times of abortion (OR = 1.23, 95% CI = 1.02-1.50, p = 0.035), and times of delivery (OR = 0.31, 95% CI = 0.20-0.48, p < 0.001) were correlated with CAF.

CONCLUSIONS

This study suggests that HLA-G 3'UTR polymorphisms and diplotypes play an important role in the process of successful pregnancy of the embryos with abnormal chromosomes after fertilization. At the same time, Different alleles or diplotypes also affect the development of embryos with UPL.

Relationships Between Polymorphisms in HLA-G 3'UTR Region and COVID-19 Disease Severity

The objective of this study is to investigate the the relationships between HLA-G gene variants and sHLA-G with susceptibility to SARS-CoV-2 infection. In this case-control study, 65 Patients with COVID-19 were and 67 healthy controls were genotyped for their main functional polymorphisms namely, the 14-bp Ins/Del (rs371194629), +3003C/T (rs1707), +3010C/G (rs1710), +3027A/C (rs17179101), +3035C/T (rs17179108), +3142C/G (rs1063320), +3187A/G (rs9380142) and +3196C/G (rs1610696) in the exon 8 of the 3' untranslated regions (3' UTRs) using sanger sequencing method. Associations were assessed for five inheritance models (codominant, dominant, recessive, over-dominant and log-additive). Moreover, the levels of plasma soluble HLA-G (sHLA-G) were explored using ELISA method. Our results revealed that the 14-bp INS/DEL polymorphism was strongly associated with COVID-19 symptoms development for almost all tested inheritance models (p < 0.001). Inversely, the (+3196C/G) polymorphism exhibited a protective effect against COVID-19. In addition, three haplotypes; UTR-1, UTR-3, and UTR-5 were found associated with COVID-19 symptoms (p < 0.05), The level of HLA-G in the serum was significantly higher in COVID-19 individuals than in healthy individuals (p < 0.001).These findings suggest that HLA-G gene polymorphisms in the regulatory 3'UTR region of the HLA-G gene may influence the host immune response to SARS-CoV-2 infection. A deeper comprehension of the functional effect of these associated polymorphisms could be useful in identifying high-risk individuals and in developing adaptive treatments for patients.

Association of HLA-G 3'UTR polymorphisms with hepatitis B virus infection in Tunisian population

Hepatitis B virus (HBV) infection is a major public health burden. The mechanisms of immune evasion during chronic HBV (CHB) infection are poorly understood. Human leukocyte antigen (HLA)-G, an immune checkpoint molecule, plays a crucial role in the tolerance mechanisms of various infectious diseases. The 3' untranslated region (3'UTR), including the HLA-G + 3142 C > G polymorphism (rs1063320) and the 14-pb Ins/Del (rs66554220) has been strongly suggested to influence HLA-G expression. This study conducted a case-control analysis to evaluate the potential correlation between the HLA-G + 3142 C > G polymorphism and HBV infection outcome in a Tunisian cohort. The HLA-G + 3142 C > G polymorphism was analysed by PCR-RFLP in 242 patients with chronic HBV infection (116 males and 126 females), 241 healthy controls (116 males and 125 females), and 100 spontaneously resolved subjects (52 males and 48 females). Patients with chronic HBV infection showed a higher frequency of the + 3142G allele compared to healthy controls and spontaneously resolved subjects (p = 0.001 and p = 0.002, respectively). An association between the + 3142G allele and high HBV DNA levels was observed when HBV patients were stratified based on their HBV DNA levels (p = 0.016). Furthermore, the dominant model (GG + GC vs CC) was associated with liver function parameters, including AST, ALT, and high HBV DNA levels (p = 0.04, p < 0.001 and p = 0.002, respectively). However, there was no significant association found between this polymorphism and the fibrosis stage (p = 0.32). The haplotype analysis, using a subset of previously published data on the HLA-G 14-pb Ins/Del polymorphism, revealed an association between the Ins/G haplotype and chronic HBV infection (H1: InsG, p < 0.001). Our findings suggest that the + 3142G allele is a risk factor for the persistence and progression of HBV infection, while the + 3142C allele serves as a protective allele associated with the spontaneous resolution of the infection. Additionally, the HLA-G 3'UTR haplotype Ins/G is associated with chronic HBV infection in the Tunisian population.

Association of HLA-E single nucleotide polymorphisms with human myeloid leukemia

Single nucleotide polymorphisms (SNPs) of HLA-E are related to the occurrence of many diseases, but their functions remain unclear. In this study, the function of SNPs at HLA-E rs76971248 and rs1264457 on the myeloid leukemia cells was analyzed by a progressive procedure, included genotyping, mRNA transcription, regulatory element, protein expression, and anti-tumor effect. The frequencies of rs76971248 G and rs1264457 G were found higher in myeloid leukemia patients than those in healthy blood donors (p < 0.05). For myeloid leukemia, rs76971248 T was protective, while rs1264457 G was susceptible. We also found that rs76971248 affected HLA-E mRNA transcription and membrane HLA-E (mHLA-E) expression in K562 cells through differently binding to transcription factor HOXA5 (p < 0.0001), while rs1264457 affected mHLA-E expression by changing mRNA transcription and an encoding amino acid (p < 0.01). In contrast, the expression of soluble HLA-E (sHLA-E) was not influenced by both rs1264457 and rs76971248. The higher HLA-E expression was detected among myeloid leukemia patients, and the K562 cells with higher HLA-E molecules played a significant inhibitory effect on the killing activity of NK-92MI cells (p < 0.05). In conclusion, the higher HLA-E expression of myeloid leukemia cells is promoted by rs76971248 G and rs1264457 G, which helps escape from NK-92MI cells' killing.

Analysis of HLA-G 14 bp Insertion/Deletion Polymorphism and HLA-G, ILT2 and ILT4 Expression in Head and Neck Squamous Cell Carcinoma Patients

HLA-G is the checkpoint molecule involved in the suppression of the immune response. Increased expression of HLA-G and its ILTs receptors have been correlated with tumor progression in various cancer types. In head and neck squamous cell carcinoma (HNSCC) tumors, the effect of HLA-G, ILT2 and ILT4 expression on cancer development has to be explained. The 34 HNSCC patients and 98 controls were genotyped for the HLA-G 14 bp ins/del polymorphism. In HNSCC lesions, HLA-G, ILT2 and ILT4 mRNA expression was analysed using real-time PCR. The association between HLA-G, ILT2 and ILT4 mRNA expression and clinical variables (age at onset, TNM staging system and p16 positivity) was also evaluated. No genetic association between the HLA-G 14 bp ins/del and HNSCC risk was detected (p > 0.05). However, in the non-metastatic HNSCC group, a significantly higher HLA-G mRNA expression was noted in tumors in the T4 stage compared to those in the T1 and T2 stages (p = 0.0289). ILT2 mRNA expression was significantly increased in non-metastatic vs. metastatic tumors (p = 0.0269). Furthermore, a significantly higher ILT4 mRNA expression was noted in tumors in the T1+T2 stage compared to those in the T3 stage (p = 0.0495). Our results suggest that the HLA-G molecule creates an immunological microenvironment involved in HNSCC development.

Harnessing the potential of HLA-G in cancer therapy: advances, challenges, and prospects

Immune checkpoint blockades have been prized in circumventing and ablating the impediments posed by immunosuppressive receptors, reaching an exciting juncture to be an innovator in anticancer therapy beyond traditional therapeutics. Thus far, approved immune checkpoint blockades have principally targeted PD-1/PD-L1 and CTLA-4 with exciting success in a plethora of tumors and yet are still trapped in dilemmas of limited response rates and adverse effects. Hence, unveiling new immunotherapeutic targets has aroused immense scientific interest in the hope of expanding the clinical application of immune checkpoint blockades to scale new heights. Human leukocyte antigen-G (HLA-G), a non-classical major histocompatibility complex (MHC) class I molecule, is enriched on various malignant cells and is involved in the hindrance of immune effector cells and the facilitation of immunosuppressive cells. HLA-G stands out as a crucial next-generation immune checkpoint showing great promise for the benefit of cancer patients. Here, we provide an overview of the current understanding of the expression pattern and immunological functions of HLA-G, as well as its interaction with well-characterized immune checkpoints. Since HLA-G can be shed from the cell surface or released by various cells as free soluble HLA-G (sHLA-G) or as part of extracellular vesicles (EVs), namely HLA-G-bearing EVs (HLA-GEV), we discuss the potential of sHLA-G and HLA-GEV as predictive biomarkers. This review also addresses the advancement of HLA-G-based therapies in preclinical and clinical settings, with a focus on their clinical application in cancer.

Prognostic significance of HLA-G in patients with colorectal cancer: a meta-analysis and bioinformatics analysis

PURPOSE

Human leukocyte antigen-G (HLA-G) has been reported to be aberrantly expressed in colorectal cancer (CRC); however, its prognostic value remains controversial. Hence, our meta-analysis aims to assess the prognostic value of HLA-G in CRC patients based on published literature and The Cancer Genome Atlas (TCGA) datasets.

METHODS

A systematic search was conducted on relevant studies retrieved from four electronic databases including PubMed, Embase, Web of Science and Cochrane Library. Hazard ratios (HRs) with 95% confidence intervals (CIs) were recorded to be applied as effective values. Fixed-effects models or random-effects models were applied on the basis of the value of heterogeneity (I 2). Publication bias was analyzed by Begg's and Egger's tests. In addition, the results were validated by using TCGA datasets.

RESULTS

Thirteen studies comprising 3896 patients were incorporated into this meta-analysis. The pooled results showed that HLA-G expression was significantly associated with poor overall survival (OS) in both the univariate analysis (HR = 1.44, 95% CI: 1.14-1.83, P = 0.002) and the multivariate analysis (HR = 1.55, 95% CI: 1.23-1.95, P < 0.001). Nevertheless, the expression of HLA-G is not related to age, sex, tumor type, tumor differentiation, TNM stage, or distant metastasis but lymph node metastasis. Notably, the prognosis of colorectal cancer was not consistent with the analysis result from TCGA data.

CONCLUSION

HLA-G expression was significantly related to poor OS in CRC according to the results of our meta-analysis. However, we found that the prognostic significance was inconsistent with our results according to the TCGA data in CRC. Hence, more research is still needed to further illustrate the prognostic role of HLA-G in CRC.