Soluble Human Leukocyte antigen-G Research Articles

Association Study of rs1632947, rs1233334, and rs371194629 Polymorphisms in Human Leukocyte Antigen GGene Expression and soluble Human Leukocyte Antigen Gwith Lupus.

Systemic lupus erythematosus is a chronic autoimmune disease that has been associated with human leukocyte antigen G (HLA-G) in previous studies on immunological diseases. This study aimed to investigate the association between three HLA-G gene polymorphisms (rs1632947, rs1233334, and rs371194629) and their impact on HLA-G mRNA expression and soluble HLA-G levels in serum. Genotyping was performed using TaqMan probe PCR. RNA extraction, reverse transcription PCR, and real-time PCR assays were conducted to assess the expression of the HLA-G gene in tissue samples. Soluble HLA-G was measured using enzyme-linked immunosorbent assay in serum. Results show a significant difference in the frequency of the G allele for two 5'-untranslated region (UTR) polymorphisms of the HLA-G gene (rs1632947 and rs1233334) located at positions -964 and -725, respectively, between lupus patients and controls, with p-values of 0.009 and 0.040, respectively. In addition, the study identified the 14 bp insertion allele of the rs371194629 polymorphism located in the 3' UTR of the gene as a risk factor for lupus, with a p-value of 0.001. Our results also indicate that lupus-related alleles may increase the risk of developing the disease by upregulating the expression of HLA-G and increasing soluble HLA-G levels in serum. The findings of the study suggest that the identified genetic variants may play a role in the development of lupus and could be useful in identifying individuals at risk for the disease. These results are important for advancing our understanding of the genetic basis of lupus and may have implications for the development of new treatments and diagnostic tools for the disease.

The implication of serum HLA-G in angiogenesis of multiple myeloma

BackgroundDespite the advances of therapies, multiple myeloma (MM) remains an incurable hematological cancer that most patients experience relapse. Tumor angiogenesis is strongly correlated with cancer relapse. Human leukocyte antigen G (HLA-G) has been known as a molecule to suppress angiogenesis. We aimed to investigate whether soluble HLA-G (sHLA-G) was involved in the relapse of MM.MethodsWe first investigated the dynamics of serum sHLA-G, vascular endothelial growth factor (VEGF) and interleukin 6 (IL-6) in 57 successfully treated MM patients undergoing remission and relapse. The interactions among these angiogenesis-related targets (sHLA-G, VEGF and IL-6) were examined in vitro. Their expression at different oxygen concentrations was investigated using a xenograft animal model by intra-bone marrow and skin grafts with myeloma cells.ResultsWe found that HLA-G protein degradation augmented angiogenesis. Soluble HLA-G directly inhibited vasculature formation in vitro. Mechanistically, HLA-G expression was regulated by hypoxia-inducible factor-1α (HIF-1α) in MM cells under hypoxia. We thus developed two mouse models of myeloma xenografts in intra-bone marrow (BM) and underneath the skin, and found a strong correlation between HLA-G and HIF-1α expressions in hypoxic BM, but not in oxygenated tissues. Yet when stimulated with IL-6, both HLA-G and HIF-1α could be targeted to ubiquitin-mediated degradation via PARKIN.ConclusionThese results highlight the importance of sHLA-G in angiogenesis at different phases of multiple myeloma. The experimental evidence that sHLA-G as an angiogenesis suppressor in MM may be useful for future development of novel therapies to prevent relapse.

How the Soluble Human Leukocyte Antigen-G levels in Amniotic Fluid and Maternal Serum Correlate with the Feto-Placental Growth in Uncomplicated Pregnancies.

Introduction: Trophoblast-derived angiogenic factors are considered to play an important role in the pathophysiology of various complications of pregnancy. Human Leukocyte Antigen-G (HLA-G) belongs to the non-classical human major histocompatibility complex (MHC-I) molecule and has membrane-bound and soluble forms. HLA-G is primarily expressed by extravillous cytotrophoblasts located in the placenta between the maternal and fetal compartments and plays a pivotal role in providing immune tolerance. The aim of this study was to establish a relationship between concentrations of soluble HLA-G (sHLA-G) in maternal serum and amniotic fluid at 16-22 weeks of gestation and the sonographic measurements of fetal and placental growth. Materials and methods: sHLA-G in serum and amniotic fluid, as well as fetal biometric data and placental volume and perfusion indices, were determined in 41 singleton pregnancies with no complications. The level of sHLA-G (U/mL) was tested with a sandwich enzyme-linked immunosorbent assay (ELISA) kit. Results: The sHLA-G levels were unchanged both in amniotic fluid and serum during mid-pregnancy. The sHLA-G level in serum correlated positively with amniotic sHLA-G level (β = 0.63, p < 0.01). Serum sHLA-G level was significantly correlated with abdominal measurements (β = 0.41, p < 0.05) and estimated fetal weight (β = 0.41, p < 0.05). Conversely, amniotic sHLA-G level and placental perfusion (VI: β = -0.34, p < 0.01 and VFI: β = -0.44, p < 0.01, respectively) were negatively correlated. A low amniotic sHLA-G level was significantly associated with nuchal translucency (r = -0.102, p < 0.05). Conclusions: sHLA-G assayed in amniotic fluid might be a potential indicator of placental function, whereas the sHLA-G level in serum can be a prognostic factor for feto-placental insufficiency.

Biomarker role of maternal soluble human leukocyte antigen G in pre-eclampsia: A meta-analysis.

Human leukocyte antigen-G (HLA-G) is a non-classical class I HLA molecule shown to regulate the immunomodulation of maternal immune cells to prevent fetal tissue destruction. Low levels of freely circulating maternal soluble HLA-G (sHLA-G) have been observed in pre-eclampsia, however, no pooled evidence exists. This meta-analysis aimed to generate pooled findings on the association of sHLA-G levels with pre-eclampsia and is the first study to perform a trimester-wise comparison of the levels of sHLA-G in preeclamptic cases and normal pregnant controls. The databases PubMed, Emba, Web of Science, and Google Scholar through May 31, 2023. Preeclamptic women were defined as cases and normal pregnancies as controls. Data on the level of sHLA-G in cases and controls was extracted and subjected to a meta-analysis using a random-effects model. The pooled effect was expressed in terms of standardized mean difference (SMD). Sensitivity analysis was performed to investigate the effect of the exclusion of each study on the pooled results. Publication bias was assessed statistically. Nine studies with altogether 567 PE cases and 1132 normal pregnancy controls were included in the meta-analysis. The first and third trimester levels of sHLA-G in PE cases were significantly lower than that of normal pregnant controls: (SMD: -0.84 [-1.29; -0.38]; p = .003; I2 = 54%) and (SMD: -0.39 [-0.71; -0.06]; p = .02; I2 = 79%) respectively. Sensitivity analysis revealed significant fluctuations in the pooled findings when few studies were excluded, raising questions on the consistency of results among studies. Although we found that first and third-trimester sHLA-G levels in pre-eclampsia are significantly lower, taking into consideration the inconsistent results from the sensitivity analysis, our findings advocate the demand for more studies with larger sample sizes to generate solid ground pooled evidence on the predictive role of sHLA-G in pre-eclampsia.

Predictive Capabilities of Human Leukocyte Antigen-G and Galectin-13 Levels in the Amniotic Fluid and Maternal Blood for the Pregnancy Outcome.

Background and Objectives: Increasing evidence points to the significant role of the angiogenic factor levels in screening for pregnancy outcome. To examine the potential relationship between concentrations of placental protein 13 (PP13) and soluble human leukocyte antigen-G (sHLA-G) in maternal serum and amniotic fluid at 16-23 weeks of gestation and the sonographic features of pregnancy as well as pregnancy outcome. Materials and Methods: PP13 and sHLA-G in serum and amniotic fluid, fetal biometrical data, and placental volume and perfusion indices were determined in 71 euploid, singleton pregnancies. Results: The serum sHLA-G level exhibits a negative correlation with the serum PP13 level (r = -0.186, p < 0.001) and a positive correlation with the sHLA-G level in amniotic fluid (r = 0.662, p < 0.001). A significant correlation was found between serum sHLA-G level and placental volume (r = 0.142, p < 0.05) and between amniotic sHLA-G level and placental perfusion (r = -0.450, p < 0.001). A low amniotic PP13 level significantly predicted the birth weight (r = -0.102, p < 0.05), the duration of pregnancy (r = -0.155, p < 0.05), and the fetal abdominal circumference (r = -0.098, p < 0.05). Conclusions: PP13 assayed in amniotic fluid might be a potential marker of fetal growth, and sHLA-G can be an adjunct modality reflecting placental sonographic parameters.

The correlation between soluble human leukocyte antigen (sHLA-G) levels and +3010 polymorphism.

Human leukocyte antigen-G (HLA-G) is classified as non-classical HLA, located in the short arm of chromosome 6 and composed of seven introns and eight exons. The HLA-G gene has a lower frequency polymorphism in the coding area and higher variability at the regulatory 5'- and 3'-untranslated regions linked to HLA-G microRNA regulation. HLA-G molecule is known to have an immunomodulatory and tolerogenic features role. In 199 Saudi individuals, we examined the association between plasma soluble HLA-G (sHLA-G) levels and eight polymorphic different sites, including 14bp ins/del/+3003T-C/+3010C-G/+3027C-A/+3035C-T/+3142C-G/+3187A-G/+3196C-G single nucleotide polymorphisms (SNPs) in exon 8 in the HLA-G gene. Our results revealed higher frequency for rs17179101C (97%), rs1707T (92%) and rs9380142A (73%) alleles. Greater frequencies for the tested genotypes were observed in 3027C/C (rs17179101) (93%), 14bp (rs1704) ins/del (92%), +3003T/T (rs1707) (85%) and +3035C/T (rs17179108) (79%) SNP genotypes. Moreover, we observed a significant association of sHLA-G with +3010G/C (rs1710) SNP. In conclusion, we showed a significant association between 3010G/C (rs1710) SNP and the sHLA-G level among our sample for Saudi populations. Our findings demonstrated that specific SNP within the HLA-G gene is linked to sHLA-G molecule secretion, suggesting sHLA-G levels may be regulated genetically.

Investigation the role of Human Leukocyte Antigen-G in Iraqi patients with papillary thyroid carcinoma

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex (MHC) protein with well-known immunomodulatory characteristics. It is also believed to be an important sign of immune tolerance in cancer cells. Immune Escape. HLA-G is also associated with disease development and prognosis in cancer patients. The goal of this study was to compare soluble HLA-G (sHLA-G) levels before and after radioactive iodine therapy (RAI) by enzyme immunoassay (ELISA). Immunohistochemistry was used to examine HLA-G protein expression in thyroid tissues from patients with papillary thyroid cancer (PTC) to investigate the relationship between HLA-G expression and patients' clinical variables. Prospective research included 138 blood samples from patients and controls, as well as 25 thyroid paraffin-embedded tissues from individuals suffering from papillary thyroid cancer (PTC) and controls. Our findings demonstrated a significant difference in the means of people who had radioactive iodine therapy against those who did not (Mean SE = 4.19 0.31, 2.216 0.08, respectively). HLA-G staining, on the other hand, was identified in tumor cells in papillary thyroid cancer, all sections were positive, strongly stained and completely membranous, indicating the presence of HLA-G protein in the tested material. These findings suggest that HLA-G may be involved in the pathogenesis of papillary thyroid cancer.

Expression and clinical implications of HLA-G and PD-L1 following kidney transplantation: A cohort study.

Kidney transplantation (KT) is the preferred treatment for end-stage renal diseases. Human leukocyte antigen G (HLA-G) and programmed death-ligand 1 (PD-L1) have notable clinical and therapeutic significance in transplantation because of their roles in promoting tolerance. This study aimed to assess HLA-G and PD-L1 levels at various stages following KT. A cohort of 12 patients was monitored from the pretransplant phase to 12 months post-surgery. Blood samples were taken at specific intervals: before kidney transplantation (T0), and then on the 7th (T7), 30th (T30), 90th (T90), 180th (T180), and 365th days post transplantation. Renal biopsies were performed in patients with graft dysfunction. Plasma levels of soluble HLA-G (sHLA-G) and PD-L1 were quantified using enzyme-linked immunosorbent assays. Additionally, immunohistochemistry was used to detect the presence of both molecules in biopsy samples. Multivariate analysis indicated that episodes of rejection were correlated with decreased expression of sHLA-G (P < .001) and PD-L1 (P < .001). Over the course of the study, the sHLA-G levels also declined (P < .001). Patients who had been transfused had lower PD-L1 levels (P = .03). Furthermore, kidney recipients from related live donors had increased HLA-G expression (P < .001). Our findings suggest that diminished HLA-G and PD-L1 levels correlate with an increased risk of graft rejection. Notably, HLA-G expression significantly decrease after the third-month posttransplantation.

Soluble HLA-G (sHLA-G) measurement might be useful as an early diagnostic biomarker and screening test for gastric cancer

Gastric cancer (GC) is the fifth most frequent malignancy worldwide and has a high mortality rate related to late diagnosis. Although the gold standard for the GC diagnosis is endoscopy with biopsy, nonetheless, it is not cost-effective and is invasive for the patient. The Human leukocyte antigen G (HLA-G) molecule is a checkpoint of the immune response. Its overexpression in cancer is associated with immune evasion, metastasis, poor prognosis, and lower overall survival. We evaluate the plasma levels of soluble HLA-G, (sHLA-G) in patients with GC and benign gastric pathologies using an ELISA test. A higher concentration of sHLA-G in patients with GC than in those with benign pathologies, higher levels of plasma sHLA-G in women with GC compared with men and significant differences in the sHLA-G levels between the benign gastric pathologies evaluated, was our main findings. As no significant differences were found between the GC assessed stages in our study population, we suggest that sHLA-G is not an adequate marker for staging GC, but it does have diagnostic potential. In addition to providing information on the potential of sHLA-G as a diagnostic marker for GC, our study demonstrate that HLA-G molecules can be found in the membrane of exosomes, which highlights the need to perform studies with a larger number of samples to explore the functional implications of HLA-G positive exosomes in the context of gastric cancer, and to determine the clinical significance and possible applications of these findings in the development of non-invasive diagnostic methods.

Association between Serum HLA-G Levels in The First Trimester of Pregnancy and The Onset of Preeclampsia: A Systematic Review and Meta-analysis Study.

Human leukocyte antigen G (HLA-G) levels are among the biomarkers suggested for pre-eclampsia (PE). This study is aimed at determining the possible relationship between low soluble HLA-G (sHLA-G) levels in maternal blood at the beginning of pregnancy and subsequent PE. We searched the international scientific databases of Web of Science, Embase, PubMed, Cochrane, and Scopus. We extracted the studies investigating the relationship between the serum levels of HLA-G in the first trimester of pregnancy and the onset of PE using the appropriate keywords. The collected data were analyzed using the random-effects meta-analysis model and STATA (version 14). A total of 5 studies met the eligibility criteria, and the total sample size was 668 subjects. The mean and SD age of case subjects was 31.41 ± 4.16 years, while it was 30.56 ± 3.5 for control subjects. According to the findings, there was an inverse relationship between HLA-G serum level in the first trimester of pregnancy and the subsequent onset of PE, standard mean difference (SMD)=-1.51 [95% confidence interval (CI): -2.26, -0.75, I2=90.8%, P=0.000]. Based on these results, low sHLA-G level in early pregnancy has a positive correlation with subsequent PE, and the significant role of sHLA-G in the early stages of placentation can be proven.

Biological profile of the follicular fluid. A pilot study

BACKGROUND: One of the most important research areas in the field of reproductive medicine is the search for biochemical and immunological parameters of oocyte quality and predicting the effectiveness of assisted reproductive technology protocols.&#x0D; AIM: The aim of this study was to evaluate the expression of follicular fluid soluble human leukocyte antigen-G, human leukocyte antigen-E, human leukocyte antigen-C, progesterone-inducing blocking factor, and relaxin levels in women with reproductive disorders.&#x0D; MATERIALS AND METHODS: This prospective cohort study included 22 patients undergoing infertility treatment in a superovulation stimulation protocol using gonadotropin-releasing hormone antagonists. The inclusion criteria were age from 25 to 39 years, tubal-peritoneal factor infertility, and voluntary participation informed consent. The levels of soluble human leukocyte antigen-G, human leukocyte antigen-E, human leukocyte antigen-C, progesterone-inducing blocking factor, and relaxin in follicular fluid samples were determined on the day of transvaginal follicle puncture by enzyme immunoassay.&#x0D; RESULTS: We established an inverse correlation between the expression levels of progesterone-inducing blocking factor and relaxin (r = 0.450) in the follicular fluid, antibodies to thyroperoxidase (r = 0.649), and thyroid-stimulating hormone (r = 0.519). We also found a direct correlation between human leukocyte antigen-E parameters in the follicular fluid, age (r = 0.813) and Body Mass Index (r = 0.866), as well as between human leukocyte antigen-C expression levels and total testosterone (r = 0.960). No data were obtained on any significant correlations between the studied biomarkers and the number of received oocytes.&#x0D; CONCLUSIONS: In this comprehensive study, we were the first who found the expression levels of five different follicular fluid components, namely, soluble human leukocyte antigen-G, human leukocyte antigen-E, human leukocyte antigen-C, progesterone-inducing blocking factor, and relaxin. Such a complex assessment of the follicular fluid can allow for establishing the quality of the oocyte to predict the onset of pregnancy in an in vitro fertilization protocol.

Peripheral HLA-G/ILT-2 immune checkpoint axis in acute and convalescent COVID-19 patients

The immunosuppressive non-classical human leukocyte antigen-G (HLA-G) can elicits pro-viral activities by down-modulating immune responses. We analysed soluble forms of HLA-G, IL-6 and IL-10 as well as on immune effector cell expression of HLA-G and its cognate ILT-2 receptor in peripheral blood obtained from hospitalised and convalescent COVID-19 patients. Compared with convalescents (N = 202), circulating soluble HLA-G levels (total and vesicular-bound molecules) were significantly increased in hospitalised patients (N = 93) irrespective of the disease severity. During COVID-19, IL-6 and IL-10 levels were also elevated. Regarding the immune checkpoint expression of HLA-G/ILT-2 on peripheral immune effector cells, the frequencies of membrane-bound HLA-G on CD3+ and CD14+ cells were almost identical in patients during and post COVID-19, while the frequency of ILT-2 receptor on CD3+ and CD14+ cells was increased during acute infection. A multi-parametric correlation analysis of soluble HLA-G forms with IL-6, IL-10, activation markers CD25 and CD154, HLA-G, and ILT-2 expression on immune cells revealed a strong positive correlation of soluble HLA-G forms with membrane-bound HLA-G molecules on CD3+/CD14+ cells only in convalescents. During COVID-19, only vesicular-bound HLA-G were positively correlated with the activation marker CD25 on T cells. Thus, our data suggest that the elevated levels of soluble HLA-G in COVID-19 are due to increased expression in organ tissues other than circulating immune effector cells. The concomitant increased expression of soluble HLA-G and ILT-2 receptor frequencies supports the concept that the immune checkpoint HLA-G/ILT-2 plays a role in the immune-pathogenesis of COVID-19.

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

Human leukocyte antigen G (HLA-G) is an immune checkpoint molecule with relevance in several cancers. The aim of this study was to evaluate the potential role of soluble HLA-G (sHLA-G), its genetic polymorphisms and its haplotype structure in the susceptibility and prognosis of primary cervical cancer in a Chinese Han population. We investigated sHLA-G plasma levels and 3' untranslated region (3'UTR) polymorphisms through ELISA and direct DNA sequencing, respectively, in cervical cancer patients (120 cases) and healthy control women (96 cases). The data were analyzed for associations using PowerMarker, Haploview, and GraphPad Prism. In this study, 8 polymorphic sites, 16 haplotypes and 23 diplotypes in the HLA-G 3'UTR were identified in our study population. We observed that each pair of 8 polymorphic sites exhibited linkage disequilibrium. The heterozygote CT genotype at position +3422 (rs17875408) was more common in cervical cancer patients than in healthy women (OR=5.285, P<0.05). Haplotypes UTR-1, UTR-3, and UTR-7 accounted for more than 85% of both groups, but no significant difference was found. The frequency of the UTR-1/UTR-3 diplotype in patients was significantly higher than that in controls (P<0.05). In addition, we further observed that HLA-G 3'UTR polymorphisms may influence the sHLA-G plasma level in patients' peripheral blood, especially 14 bp Ins/Del (rs371194629) and +3142 C/G (rs1063320). A receiver operating characteristic (ROC) curve analysis showed that the sHLA-G level had good diagnostic performance in differentiating patients with cervical cancer from healthy women (AUC>0.7). Among patients, mean sHLA-G levels increased with increasing FIGO stages but were not related to the overall survival time. The results of the present study enhance our understanding of how HLA-G 3'UTR polymorphisms can influence the peripheral sHLA-G plasma level and play a key role in cervical carcinogenesis. This study further confirmed that sHLA-G may represent a novel plasma biomarker for the prognosis and potential therapeutic target of cervical cancer.

Association of HLA-G 3'UTR Polymorphisms with Response to First-Line FOLFIRI Treatment in Metastatic Colorectal Cancer.

Microenvironmental factors such as non-classical human leukocyte antigen-G (HLA-G) have been associated with cancer invasiveness and metastatic progression. HLA-G expression has been associated with specific single-nucleotide polymorphisms (SNP) in HLA-G 3'untranslated region (UTR) in several diseases. The primary aim was to investigate the predictive role of HLA-G polymorphisms on treatment efficacy in metastatic colorectal cancer (mCRC) patients homogeneously treated with first-line FOLFIRI (irinotecan, 5-fluorouracil, and leucovorin) and their association with soluble HLA-G (sHLA-G) plasma concentration. HLA-G 3'UTR was sequenced in 248 patients. A set of eight polymorphisms and related haplotypes were analyzed for their association with best tumor response, overall survival (OS), and progression-free survival (PFS). sHLA-G was measured by immunoassay in 35 available plasma samples and correlated with HLA-G 3'UTR polymorphisms/haplotypes. Our results showed that carriers of rs371194629 (+2960)-Ins allele were at risk for lack of complete response (hazard ratio (HR):0.29, pBH = 0.0336), while carriers of rs1710 (+3010)-G allele (rs1063320 (+3142)-C allele in linkage-disequilibrium), and rs9380142 (+3187)-G allele had a higher chance of complete response according to additive models (HR:4.58, pBH = 0.0245; HR:3.18, pBH = 0.0336, respectively). The combination of rs371194629-Del, rs1710-G, and rs9380142-G alleles forms the UTR1 haplotype. Patients who were carriers of UTR1/UTR-1 diplotype had a greater chance of complete response to therapy (HR:10.59, pBH = 0.0294). The same three beneficial alleles showed a trend toward higher pre-treatment sHLA-G plasma levels, supporting a functional role for polymorphisms in protein secretion. In conclusion, genetic variants of HLA-G are associated with treatment efficacy in mCRC patients treated with first-line FOLFIRI. This finding shed light on the combined effect of this immune system factor and chemotherapy in cancer patients.

Prognostic role of serum cytokines and soluble HLA-G levels in children with leukemia who undergo allogeneic stem cell transplantation

This is the first study to have investigated the prognostic role of cytokines and soluble human leukocyte antigen-G (sHLA-G) levels in pediatric leukemia patients who have undergone allogeneic stem cell transplantation (allo-SCT). Forty-one patients with acute leukemia (n = 28, acute lymphoblastic leukemia (ALL) and n = 13, acute myeloblastic leukemia) were recruited. Patients were examined at diagnosis (n = 26), in the pre-transplantation period (PreTx) (n = 26), on the day of transplantation (Tx0) (n = 41), and on post-transplantation Days 14 (PostTx14) (n = 41) and 28 (PostTx28) (n = 41). Serum levels of pro-inflammatory cytokines (interleukin [IL]-1, IL-2, IL-6, Tumor necrosis factor [TNF]-α), anti-inflammatory cytokines (IL-4, IL-10), and sHLA-G were measured by Enzyme-Linked ImmunoSorbent Assay. Median levels of all cytokines tested and sHLA-G were significantly higher at diagnosis and at the post-transplant time points than at PreTx (all p < 0.05). At the time of diagnosis (specifically ALL) and at PostTx14, elevated IL-4, IL-10, and/or sHLA-G were associated with higher post-transplant relapse rates (all p < 0.05). Elevated IL-2 and TNF-α at Tx0 were associated with lower survival rates (both p < 0.05). Levels of serum cytokines and sHLA-G may be useful predictors of survival and relapse in pediatric leukemia patients who undergo allo-SCT.

The Human Leukocyte Antigen G as an Immune Escape Mechanism and Novel Therapeutic Target in Urological Tumors.

The non-classical human leukocyte antigen G (HLA-G) is a potent regulatory protein involved in the induction of immunological tolerance. This is based on the binding of membrane-bound as well as soluble HLA-G to inhibitory receptors expressed on various immune effector cells, in particular NK cells and T cells, leading to their attenuated functions. Despite its restricted expression on immune-privileged tissues under physiological conditions, HLA-G expression has been frequently detected in solid and hematopoietic malignancies including urological cancers, such as renal cell and urothelial bladder carcinoma and has been associated with progression of urological cancers and poor outcome of patients: HLA-G expression protects tumor cells from anti-tumor immunity upon interaction with its inhibitory receptors by modulating both the phenotype and function of immune cells leading to immune evasion. This review will discuss the expression, regulation, functional and clinical relevance of HLA-G expression in urological tumors as well as its use as a putative biomarker and/or potential therapeutic target for the treatment of renal cell carcinoma as well as urothelial bladder cancer.

Systematic Evaluation of HLA-G 3'Untranslated Region Variants in Locally Advanced, Non-Metastatic Breast Cancer Patients: UTR-1, 2 or UTR-4 are Predictors for Therapy and Disease Outcome.

Despite major improvements in diagnostics and therapy in early as well as in locally advanced breast cancer (LABC), metastatic relapse occurs in about 20% of patients, often explained by early micro-metastatic spread into bone marrow by disseminated tumor cells (DTC). Although neoadjuvant chemotherapy (NACT) has been a successful tool to improve overall survival (OS), there is growing evidence that various environmental factors like the non-classical human leukocyte antigen-G (HLA-G) promotes cancer invasiveness and metastatic progression. HLA-G expression is associated with regulatory elements targeting certain single-nucleotide polymorphisms (SNP) in the HLA-G 3’ untranslated region (UTR), which arrange as haplotypes. Here, we systematically evaluated the impact of HLA-G 3’UTR polymorphisms on disease status, on the presence of DTC, on soluble HLA-G levels, and on therapy and disease outcome in non-metastatic LABC patients. Although haplotype frequencies were similar in patients (n = 142) and controls (n = 204), univariate analysis revealed that the UTR-7 haplotype was related to patients with low tumor burden, whereas UTR-4 was associated with tumor sizes >T1. Furthermore, UTR-4 was associated with the presence of DTC, but UTR-3 and UTR-7 were related to absence of DTC. Additionally, increased levels of soluble HLA-G molecules were found in patients carrying UTR-7. Regarding therapy and disease outcome, univariate and multivariate analysis highlighted UTR-1 or UTR-2 as a prognostic parameter indicative for a beneficial course of disease in terms of complete response towards NACT or progression-free survival (PFS). At variance, UTR-4 was an independent risk factor for a reduced OS besides already known parameters. Taken into account the most common HLA-G 3’UTR haplotypes (UTR-1–UTR-7, UTR-18), deduction of the UTR-1/2/4 haplotypes to specific SNPs revealed that the +3003C variant, unique for UTR-4, seemed to favor a detrimental disease outcome, while the +3187G and +3196G variants, unique for UTR-1 or UTR-2, were prognostic parameters for a beneficial course of disease. In conclusion, these data suggest that the HLA-G 3’UTR variants +3003C, +3187G, and +3196G are promising candidates for the prediction of therapy and disease outcome in LABC patients.

Soluble human leukocyte antigen-G is a potential embryo viability biomarker and a positive predictor of live-births in humans.

Human infertility affects 15-20% of reproductive-age couples and it is mitigated by assisted reproductive technology (ART) approaches. Poor biological viability of embryos contributes to implantation failure and live birth rate (LBR). This study is aimed to examine whether or not embryo-secreted soluble human leukocyte antigen-G (sHLA-G) is (i) associated with developing embryos and (ii) able to predict successful pregnancy outcome. A retrospective, multicentric study using 539 human embryo spent medium samples (E-SMs), analysed for sHLA-G levels by ELISA. Correlation analysis was performed on sHLA-G levels with developing embryonic stages, their quality scores and pregnancy outcome in terms of LBR. Of 539 E-SMs analysed, 445 had detectable sHLA-G (83%) with levels varying within and across clinics and, between stages of embryonic development. Levels of sHLA-G (ng/mL) were significantly (P<.05) different in E-SMs of cleavage-stage embryos versus blastocysts. There was an insignificant correlation between the sHLA-G levels and morphology scores of embryos. But, sHLA-G levels showed a positive correlation with grades of blastocysts and importantly, its levels were significantly (P<.05) higher in live-birth vis-a-vis no-birth cases. Also, levels were higher in live-births out of blastocysts-ETs versus cleavage-stage-embryo transfers. Altered levels were observed with embryos, which resulted in miscarriages. Overall, a significant (P<.0001) association of sHLA-G with live births was observed. Embryo-derived sHLA-G can be a valuable embryo viability, independent, biomarker, which can predict live-birth outcome and it could be useful as an adjunct to existing criteria for elective single embryo transfer.

Circulating HLA-G and its association with cardiovascular markers in pregnancy

Human Leukocyte Antigen-G (HLA-G) prevents the activity of immune cells and is decreased in women with preeclampsia. We aimed to investigate the associations between circulating soluble HLA-G (sHLA-G) and 92 cardiovascular disease-related biomarkers from a previously published multiplex study in women with preeclampsia and controls. We found 15 markers significantly associated with circulating sHLA-G in univariate analyses. After multivariable adjusted regression, only proto-oncogene tyrosine-protein kinase Src (SRC) and vascular endothelial growth factor D were significantly associated with sHLA-G. Low SRC, previously observed in the circulation of preeclamptic women, may be regulated by low sHLA-G, and reflect decreased trophoblast differentiation and syncytical formation.

New markers for predictions of acute and chronic rejection and graft outcomes in kidney transplant recipients; HLA-G gene 3'UTR 14bp polymorphism and sHLA-G.

The aim of this study was to evaluate the relation of Human Leukocyte Antigen-G (HLA-G) 14bp ins/del (insertion/deletion) polymorphism and soluble HLA-G (sHLA-G) level with rejection in kidney transplant recipients. The study was planned as a case-control study involving two hundred fifty kidney transplant recipients. The case group consisted of 125 (female/male: 56/69) kidney transplant recipients diagnosed with acute (n=52) and chronic rejection (n=73). The control group consisted of one hundred twenty-five kidney transplant patients with no acute or chronic rejection matched by gender and age in the case group. The sHLA-G level in the recipient's plasma (at the time of rejection for the case, the same time as the case after the transplant for control) was analyzed by Enzyme-Linked Immunosorbent Assay (ELISA). HLA-G 3' untranslated region (3'UTR) polymorphism of recipient and donor was determined using agarose gel electrophoresis and DNA sequencing method. In our study, it was shown that acute rejection rate increased 1.06 times and chronic rejection rate increased 1.14 times in kidney transplant recipients with low serum sHLA-G levels. The rejection patients with the HLA-G 14bp del/del genotype had higher sHLA-G levels post-transplantation. The frequency of acute rejection was lower in patients with HLA-G 14bp del/del polymorphism than those with ins/ins and ins/del polymorphisms. This study proposes that HLA-G 3'UTR polymorphism and sHLA-G level might be useful in prediction of rejection in kidney transplant recipients.