Secretion of sHLA-G molecules in malignancies

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.

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.

Prognostic significance of high circulating sHLA-G in ovarian carcinoma

HLA-G is a non-classical major histocompatibility complex class Ib molecule. Its expression has been described in various cancer types, including ovarian cancer. HLA-G molecule has been implicated in immune escape and in progression of ovarian tumor cells. Our goal was to assess if total soluble (s)HLA-G molecules or HLA-G5 and sHLA-G1 isoforms could be considered as circulating ovarian tumor biomarkers, we measured the concentration of these molecules in ovarian carcinoma patients stratified according with their clinicopathological parameters. sHLA-G, sHLA-G1 and HLA-G5 concentrations were dosed in plasma samples by sandwich-ELISA. The sHLA-G dimerization was analyzed after immunoprecipitation and SDS-PAGE migration. Total sHLA-G and sHLA-G1 levels were significantly represented in plasma of ovarian carcinoma patients compared to healthy controls. sHLA-G1 isoform concentration was highly represented in ovarian carcinoma compared to HLA-G5 isoforms. Additionally, high sHLA-G molecules have been found in aged patients, as well as in patients with advanced stages, and those with metastatic lymph nodes and those with distant metastasis. Elsewhere, sHLA-G monomers were highly represented in ovarian carcinoma patients compared to controls. sHLA-G plasmatic protein was highly represented in ovarian carcinoma. In effect, HLA-G might be considered as a new checkpoint molecule that could be used to assess progression and recurrence of the disease, thus placing it as a potential biomarker for advanced and complicated ovarian carcinoma.

Specific and Aspecific Molecular Checkpoints as Potential Targets for Dismantling Tumor Hierarchy and Preventing Relapse and Metastasis Through Shielded Cytolytic Treatments

I have recently theorized that several similarities exist between the tumor process and embryo development. Starting from an initial cancer stem cell (CSC0), similar to an embryonic stem cell (ESC), after implantation in a niche, primary self-renewing CSCs (CSC1s) would arise, which then generate secondary proliferating CSCs (CSC2s). From these epithelial CSCs, tertiary mesenchymal CSCs (CSC3s) would arise, which, under favorable stereotrophic conditions, by asymmetric proliferation, would generate cancer progenitor cells (CPCs) and then cancer differentiated cells (CDCs), thus giving a defined cell heterogeneity and hierarchy. CSC1s-CSC2s-CSC3s-CPCs-CDCs would constitute a defined "tumor growth module," able to generate new tumor modules, forming a spherical avascular mass, similar to a tumor sphere. Further growth in situ of this initial tumor would require implantation in the host and vascularization through the overexpression of some aspecific checkpoint molecules, such as CD44, ID, LIF, HSP70, and HLA-G. To expand and spread in the host tissues, this vascularized tumor would then carry on a real growth strategy based on other specific checkpoint factors, such as those contained in the extracellular vesicles (EVs), namely, microRNAs, messenger RNAs, long non-coding RNAs, and integrins. These EV components would be crucial in tumor progression because they can mediate intercellular communications in the surrounding microenvironment and systemically, dictating to recipient cells a new tumor-enslaved phenotype, thus determining pre-metastatic conditions. Moreover, by their induction properties, the EV contents could also frustrate in time the effects of cytolytic tumor therapies, where EVs released by killed CSCs might enter other cancer and non-cancer cells, thus giving chemoresistance, non-CSC/CSC transition (recurrence), and metastasis. Thus, antitumor cytotoxic treatments, "shielded" from the EV-specific checkpoints by suitable adjuvant agents, simultaneously targeting the aforesaid aspecific checkpoints should be necessary for dismantling the hierarchic tumor structure, avoiding recurrence and preventing metastasis.

Expression and change of miR-199b-5p, s HLA-G in thyroid carcinoma

OBJECTIVE

This research aims to investigate the relationship between the expression of microRNA-199b-5p (miR-199b-5p) and soluble human leukocyte antigen G (sHLA-G) in thyroid cancer tissues and its clinicopathological characteristics, as well as its impact on prognosis.

METHODS

Frozen tissues and serum from 85 patients with thyroid cancer, 27 with thyroid adenoma, 19 with Hashimoto's thyroiditis and 14 with nodular goiter from February 2014 to March 2016 were sampled. The miR-199b-5pmRNA expression in tissues was analyzed by real-time quantitative PCR. Serum HLA-G expression was detected by ELISA, and the relationship between s HLA-G expression and clinicopathological characteristics of thyroid cancer was analyzed. The relationship between 1- and 3-year survival rates of all patients and the expression of both detection indexes was observed.

RESULTS

Compared with normal thyroid specimens, nodular goiter, Hashimoto's thyroiditis, thyroid adenoma and thyroid cancer patients, the relative expression of miR-199b-5pmRNA in thyroid cancer tissues was the lowest, while that of s HLA-G was the highest in serum of patients (P < 0.05). The levels of miR-199b-5pmRNA and serum s HLA-G in tumor tissues were correlated with clinical pathological features such as tumor size, differentiation degree, capsule invasion, lymph node metastasis, etc. (all P < 0.05). The expression of miR-199b-5pmRNA and s HLA-G were negatively correlated. ROC curve identified that miR-199b-5pmRNA and HLA-g had obvious diagnostic value for thyroid cancer patients. Kaplan-Meier survival analysis manifested that the 1- and 3-year survival rates of the miR-199b-5p low expression group in thyroid cancer tissues were lower than the miR-199b-5p high expression group, and the rates of the s HLA-G low expression group were higher than the s HLA-G high expression group.

CONCLUSION

The miR-199b-5p expression in thyroid cancer tissues and HLA-g in serum were related to tumor size, differentiation degree, capsular invasion, lymph node metastasis and other characteristics. MiR-199b-5p may jointly affect the progression of thyroid cancer with s HLA-G.

Understanding HLA-G driven journey from HPV infection to cancer cervix: Adding missing pieces to the jigsaw puzzle

Human Papillomavirus (HPV) is a vital risk-factor for cancer cervix. However, persistent HPV infection results in cervical cancer in only a minority. Probably, HPV subdues the host immune response for persistence, which includes augmentation of HLA-G and plausibly aids in progression to cervical cancer. HLA-G, which comprises of membrane and soluble form, downregulates the host's immune response and generate tolerance. The current study aimed to analyze both forms of HLA-G in fresh tissue and plasma of women with HPV-infected and uninfected cervix and cancer cervix using Western blot and ELISA. The study cohort included 30 women with cervical carcinoma and equal number with normal cervix and 6 with HPV infected cervix. We observed a significant upregulation of membranous HLA-G expression in HPV infected cervix and cervical carcinoma (P < 0.001). Interestingly, the pairwise comparison of HLA-G tissue protein expression of the normal cervix and cervical carcinoma, as well as the normal cervix with HPV infected cervix, was significant (P < 0.001). Levels of soluble HLA-G were significantly raised in carcinoma cervix. We observed a progressive increase in HLA-G protein expression in HPV infected cervix and cervical carcinoma. These findings compel us to hypothesize that the upregulation of HLA-G expression favors the persistence of HPV in a microenvironment of a submissive host response. This progressive upregulation further leads to cervical cancer. Thus elimination of HPV infection seems to be a desirable proposition to prevent cervical cancer. In the absence of antiviral therapy for HPV, exploration of HLA-G antibody-based therapeutic strategies appear promising.

NKG2A/CD94 Is a New Immune Receptor for HLA-G and Distinguishes Amino Acid Differences in the HLA-G Heavy Chain

Natural killer (NK) cell therapies are a tool to antagonize a dysfunctional immune system. NK cells recognize malignant cells, traffic to a tumor location, and infiltrate the solid tumor. The immune checkpoint molecule human leukocyte antigen (HLA)-G is upregulated on malignant cells but not on healthy surrounding cells, the requirement of understanding the basis of receptor mediated events at the HLA-G/NK cell interface becomes obvious. The NK cell receptors ILT2 and KIR2DL4 have been described to bind to HLA-G; however, their differential function and expression levels on NK cell subsets suggest the existence of an unreported receptor. Here, we performed a ligand-based receptor capture on living cells utilizing sHLA-G*01:01 molecules coupled to TriCEPS and bound to NK cells followed by mass spectrometric analyses. We could define NKG2A/CD94 as a cognate receptor of HLA-G. To verify the results, we used the reciprocal method by expressing recombinant soluble heterodimeric NKG2A/CD94 molecules and used them to target HLA-G*01:01 expressing cells. NKG2A/CD94 could be confirmed as an immune receptor of HLA-G*01:01. Despite HLA-G is marginal polymorphic, we could previously demonstrate that the most common allelic subtypes HLA-G*01:01/01:03 and 01:04 differ in peptide repertoire, their engagement to NK cells, their catalyzation of dNK cell proliferation and their impact on NK cell development. Continuing these studies with regard to NKG2A/CD94 engagement we engineered recombinant single antigen presenting K562 cells and targeted the surface expressed HLA-G*01:01, 01:03 or 01:04 molecules with NKG2A/CD94. Specificity and sensitivity of HLA-G*01:04/NKG2A/CD94 engagement could be significantly verified. The binding affinity decreases when using K562-G*01:03 or K562-G*01:01 cells as targets. These results demonstrate that the ligand-receptor assignment between HLA-G and NKG2A/CD94 is dependent of the amino acid composition in the HLA-G heavy chain. Understanding the biophysical basis of receptor-mediated events that lead to NK cell inhibition would help to remove non-tumor reactive cells and support personalized mild autologous NK cell therapies.

Vesicular-Bound HLA-G as a Predictive Marker for Disease Progression in Epithelial Ovarian Cancer

Extracellular vesicles (EV) and their tumor-supporting cargos provide a promising translational potential in liquid biopsies for risk assessment of epithelial ovarian cancer (EOC) patients frequently relapsing, despite initial complete therapy responses. As the immune checkpoint molecule HLA-G, which is operative in immune-escape, can be released by EV, we evaluate the abundance of EV and its vesicular-bound amount of HLA-G (HLA-G_EV) as a biomarker in EOC. After enrichment of EV from plasma samples, we determined the EV particle number and amount of HLA-G_EV by nanoparticle tracking analysis or ELISA. The association of results with the clinical status/outcome revealed that both, EV particle number and HLA-G_EV were significantly elevated in EOC patients, compared to healthy females. However, elevated levels of HLA-G_EV, but not EV numbers, were exclusively associated with a disadvantageous clinical status/outcome, including residual tumor, presence of circulating tumor cells, and disease progression. High HLA-G_EV status was an independent predictor of progression, besides residual tumor burden and platinum-sensitivity. Especially among patients without residual tumor burden or with platinum-sensitivity, HLA-G_EV identified patients with high risk of progression. Thus, this study highlights HLA-G_EV as a potential novel biomarker for risk assessment of EOC patients with a rather beneficial prognosis defined by platinum-sensitivity or lack of residual tumor burden.

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.

The Relationship between the HLA-G Polymorphism and sHLA-G Levels in Parental Pairs with High-Risk Pregnancy

Human leukocyte antigen G (HLA-G) is observed in immune system cells and other organs. It is a class Ib molecule, which plays a pivotal role in the implantation and maintenance of pregnancy. The aim of this study was to assess the relationship between serum sHLA-G levels and the HLA-G allele in parental pairs with complicated obstetric histories. The clinical material consisted of 210 women and 190 men with the experience of a complicated or an unsuccessful pregnancy. The control group included parents-89 women and 86 men-lacking complicated obstetric histories. We applied genetic analysis methods: isolation of genomic DNA, sequencing, and determination of serum sHLA-G levels. There were no statistically significant differences in the frequencies of the HLA-G -725 C>G polymorphism between particular experimental groups compared with the control group (p > 0.05). The median sHLA-G levels in the women with the HLA-G10101 allele (15.4 U/mL) were significantly higher than in the women with other alleles (p < 0.05). The HLA-G 10101 allele seems to protect against antiphospholipid syndrome, which may be associated with increased serum sHLA-G levels in its carriers. The relationship between serum sHLA-G levels and the HLA-G polymorphisms in the Polish population requires further investigation.

HLA-G 3' untranslated region variants +3187G/G, +3196G/G and +3035T define diametrical clinical status and disease outcome in epithelial ovarian cancer

Expression of the non-classical human leukocyte antigen-G (HLA-G) promotes cancer progression in various malignancies including epithelial ovarian cancer (EOC). As single nucleotide polymorphisms (SNPs) in the HLA-G 3' untranslated region (UTR) regulate HLA-G expression, we investigated HLA-G 3'UTR haplotypes arranged by SNPs in healthy controls (n = 75) and primary EOC patients (n = 79) and determined soluble HLA-G (sHLA-G) levels. Results were related to the clinical status and outcome. Although haplotype frequencies were similar in patients and controls, (i) sHLA-G levels were increased in EOC independent of the haplotype, (ii) homozygosity for UTR-1 or UTR-2 genotypes were significantly associated with metastases formation and presence of circulating tumor cells before therapy, whereas (iii) the UTR-5 and UTR-7 haplotypes were significantly associated with a beneficial clinical outcome regarding negative nodal status, early FIGO staging, and improved overall survival. Lastly, (iv) the ambivalent impact on clinical EOC aspects could be deduced to specific SNPs in the HLA-G 3'UTR: +3187G, +3196G and +3035T alleles. Our results give evidence that even if the genetic background of the HLA-G 3'UTR is identical between patients and controls, certain SNPs have the potential to contribute to diametrical clinical status/outcome in EOC.

Similarities Between Embryo Development and Cancer Process Suggest New Strategies for Research and Therapy of Tumors: A New Point of View

Here, I propose that cancer stem cells (CSCs) would be equivalent to para-embryonic stem cells (p-ESCs), derived from adult cells de-re-programmed to a ground state. p-ESCs would differ from ESCs by the absence of genomic homeostasis. A p-ESC would constitute the cancer cell of origin (i-CSC or CSC0), capable of generating an initial tumor, corresponding to a pre-implantation blastocyst. In a niche with proper signals, it would engraft as a primary tumor, corresponding to a post-implantation blastocyst. i-CSC progeny would form primary pluripotent and slow self-renewing CSCs (CSC1s), blocked in an undifferentiated state, corresponding to epiblast cells; CSC1s would be tumor-initiating cells (TICs). CSC1s would generate secondary CSCs (CSC2s), corresponding to hypoblast cells; CSC2s would be tumor growth cells (TGCs). CSC1s/CSC2s would generate tertiary CSCs (CSC3s), with a mesenchymal phenotype; CSC3s would be tumor migrating cells (TMCs), corresponding to mesodermal precursors at primitive streak. CSC3s with more favorable conditions (normoxia), by asymmetrical division, would differentiate into cancer progenitor cells (CPCs), and these into cancer differentiated cells (CDCs), thus generating a defined cell hierarchy and tumor progression, mimicking somito-histo-organogenesis. CSC3s with less favorable conditions (hypoxia) would delaminate and migrate as quiescent circulating micro-metastases, mimicking mesenchymal cells in gastrula morphogenetic movements. In metastatic niches, these CSC3s would install and remain dormant in the presence of epithelial/mesenchymal transition (EMT) signals and hypoxia. But, in the presence of mesenchymal/epithelial transition (MET) signals and normoxia, they would revert to self-renewing CSC1s, reproducing the same cell hierarchy of the primary tumor as macro-metastases. Further similarities between ontogenesis and oncogenesis involving crucial factors, such as ID, HSP70, HLA-G, CD44, LIF, and STAT3, are strongly evident at molecular, physiological and immunological levels. Much experimental data about these factors led to considering the cancer process as ectopic rudimentary ontogenesis, where CSCs have privileged immunological conditions. These would consent to CSC development in an adverse environment, just like an embryo, which is tolerated, accepted and favored by the maternal organism in spite of its paternal semi-allogeneicity. From all these considerations, novel research directions, potential innovative tumor therapy and prophylaxis strategies might, theoretically, result.

HLA-G Expression in Tumor Tissues and Soluble HLA-G Plasma Levels in Patients with Gastrointestinal Cancer

Background:

Overexpression of human leukocyte antigen G (HLA-G) and increased plasma levels of soluble HLA-G (sHLA-G) have been reported in different human malignancies, and are believed to be involved in tumor immune evasion.

Objectives:

This study was designed to evaluate the expression of HLA-G in tumor tissues and the plasma levels of sHLA-G in patients with gastrointestinal cancer, and to determine their associations with clinicopathological factors. The link between Helicobacter pylori infection and increased HLA-G expression or sHLA-G levels was also investigated in patients with gastric cancer.

Methods:

HLA-G expression was investigated in tumor tissues from 100 patients with gastric and colorectal adenocarcinoma using immunohistochemistry test, and plasma levels of sHLA-G were measured in 82 patients with ELISA method. The presence of H. pylori genome was investigated in tumor tissues from 25 patients with gastric cancer by PCR method.

Results:

HLA-G expression was observed in 43% of colorectal cancers and 34.6% of gastric cancers, and was not related with any of the clinicopathological factors. There was a significant correlation between increased sHLA-G level and stage I tumors. Eight of 25 (32%) gastric cancer specimens were positive for H. pylori, of which 3 samples were positive for HLA-G. Soluble HLA-G levels were above the cut-off value in all H. pylori-positive patients.

Conclusion:

Plasma levels of sHLA-G were significantly increased in our patients with a sensitivity of 89% and a specificity of 62%. Soluble HLA-G level can be considered a useful indicator for the early diagnosis of gastric and colorectal adenocarcinoma.

HLA-G peptide preferences change in transformed cells: impact on the binding motif

HLA-G is known for its strictly restricted tissue distribution. HLA-G expression could be detected in immune privileged organs and many tumor entities such as leukemia, multiple myeloma, and non-Hodgkin and Hodgkin’s lymphoma. This functional variability from mediation of immune tolerance to facilitation of tumor immune evasion strategies might translate to a differential NK cell inhibition between immune-privileged organs and tumor cells. The biophysical invariability of the HLA-G heavy chain and its contrary diversity in immunity implicates a strong influence of the bound peptides on the pHLA-G structure. The aim was to determine if HLA-G displays a tissue-specific peptide repertoire. Therefore, using soluble sHLA-G technology, we analyzed the K562 and HDLM-2 peptide repertoires. Although both cell lines possess a comparable proteome and recruit HLA-G-restricted peptides through the same peptide-loading pathway, the peptide features appear to be cell specific. HDLM-2 derived HLA-G peptides are anchored by an Arg at p1 and K562-derived peptides are anchored by a Lys. At p2, no anchor motif could be determined while peptides were anchored at pΩ with a Leu and showed an auxiliary anchor motif Pro at p3. To appreciate if the peptide anchor alterations are due to a cell-specific differential peptidome, we performed analysis of peptide availability within the different cell types. Yet, the comparison of the cell-specific proteome and HLA-G-restricted ligandome clearly demonstrates a tissue-specific peptide selection by HLA-G molecules. This exclusive and unexpected observation suggests an exquisite immune function of HLA-G.

Upregulation of Soluble HLA-G in Chronic Left Ventricular Systolic Dysfunction

Left ventricular systolic dysfunction (LVSD) defined by ejection fraction (EF) <40% is common, serious but treatable, and correct diagnosis is the cornerstone of effective treatment. Biomarkers may help to diagnose LVSD and give insight into the pathophysiology. The immune system is activated in LVSD, and the immunomodulatory molecule human leukocyte antigen-G (HLA-G) may be involved. The primary aim was to measure soluble HLA-G (sHLA-G) in the blood in different stages of LVSD (<30% and 30–40%), in the midrange EF 40–50%, and in preserved EF ≥ 50% and to validate sHLA-G as a LVSD biomarker. The secondary aim was to examine associations between HLA-G gene polymorphisms influencing expression levels and LVSD. The 260 study participants were ≥75 years old, many with risk factors for heart disease or with known heart disease. Soluble HLA-G was significantly and uniformly higher in the groups with EF < 50% (<30, 30–40, and 40–50%) compared to EF > 50% (p < 0.0001). N-terminal fragment-pro-B-type natriuretic peptide (NT-proBNP) and uric acid values were inversely related to EF. According to Receiver Operating Characteristic (ROC) curves NT-proBNP outperformed both sHLA-G and uric acid as biomarkers of LVSD. Soluble HLA-G in blood plasma was elevated in LVSD regardless of EF. A novel finding was that a combined 14 bp ins-del/+3142 SNP HLA-G haplotype was associated with EF < 40%.

A novel tumor-promoting mechanism of IL6 and the therapeutic efficacy of tocilizumab: Hypoxia-induced IL6 is a potent autophagy initiator in glioblastoma via the p-STAT3-MIR155-3p-CREBRF pathway

Hypoxia induces protective autophagy in glioblastoma cells and new therapeutic avenues that target this process may improve the outcome for glioblastoma patients. Recent studies have suggested that the autophagic process is upregulated in glioblastomas in response to extensive hypoxia. Hypoxia also induces the upregulation of a specific set of proteins and microRNAs (miRNAs) in a variety of cell types. IL6 (interleukin 6), an inflammatory autocrine and paracrine cytokine that is overexpressed in glioblastoma, has been reported to be a biomarker for poor prognosis because of its tumor-promoting effects. Here, we describe a novel tumor-promoting mechanism of IL6, whereby hypoxia-induced IL6 acts as a potent initiator of autophagy in glioblastoma via the phosphorylated (p)-STAT3-MIR155-3p pathway. IL6 and p-STAT3 levels correlated with the abundance of autophagic cells and HIF1A levels in human glioma tissues and with the grade of human glioma, whereas inhibition of exogenous or endogenous IL6 repressed autophagy in glioblastoma cells in vitro. Knockdown of endogenous MIR155-3p inhibited IL6-induced autophagy, and enforced expression of MIR155-3p restored the anti-autophagic activity of IL6 inhibitors. We show that the hypoxia-IL6-p-STAT3-MIR155-3p-CREBRF-CREB3-ATG5 pathway plays a central role in malignant glioma progression, with blockade of the IL6 receptor by tocilizumab demonstrating a certain level of therapeutic efficacy in a xenograft model in vivo, especially in combination with temozolomide. Moreover, tocilizumab inhibits autophagy by promoting tumor apoptosis. Collectively, our findings provide new insight into the molecular mechanisms underlying hypoxia-induced glioma cell autophagy and point toward a possible efficacious adjuvant therapy for glioblastoma patients.

Immunomodulation of classical and non-classical HLA molecules by ionizing radiation

Radiotherapy has been employed for the treatment of oncological patients for nearly a century, and together with surgery and chemotherapy, radiation oncology constitutes one of the three pillars of cancer therapy. Ionizing radiation has complex effects on neoplastic cells and on tumor microenvironment: beyond its action as a direct cytotoxic agent, tumor irradiation triggers a series of alterations in tumoral cells, which includes the de novo synthesis of particular proteins and the up/down-regulation of cell surface molecules. Additionally, ionizing radiation may induce the release of "danger signals" which may, in turn lead to cellular and molecular responses by the immune system. This immunomodulatory action of ionizing radiation highlights the importance of the combined use (radiotherapy plus immunotherapy) for cancer healing. Major histocompatibility complex antigens (also called Human Leukocyte Antigens, HLA in humans) are one of those molecules whose expression is modulated after irradiation. This review summarizes the modulatory properties of ionizing radiation on the expression of HLA class I (classical and non-classical) and class II molecules, with special emphasis in non-classical HLA-I molecules.

The prognostic impact of soluble and vesicular HLA-G and its relationship to circulating tumor cells in neoadjuvant treated breast cancer patients

The non-classical human leukocyte antigen G (HLA-G) molecule and its soluble forms exert multiple immune suppressive regulatory functions in malignancy and in stem cells contributing to immune escape mechanisms. HLA-G can be secreted as free soluble HLA-G molecules or via extracellular vesicles (EVs). Here we evaluated these soluble HLA-G forms as prognostic marker for prediction of the clinical outcome of neoadjuvant chemotherapy (NACT) treated breast cancer (BC) patients. Plasma samples of BC patients procured before (n=142) and after (n=154) NACT were quantified for total soluble HLA-G (sHLA-Gtot) and HLA-G levels in ExoQuick™ derived EV fractions (sHLA-GEV) by ELISA. The corresponding increments were specified as free sHLA-G (sHLA-Gfree). Total and free sHLA-G were significantly increased in NACT treated BC patients compared to healthy controls (n=16). High sHLA-Gfree levels were exclusively associated to estrogen receptor expression before NACT. Importantly, high sHLA-GEV levels before NACT were related to disease progression and the detection of stem cell-like circulating tumor cells, but high sHLA-Gfree levels indicated an improved clinical outcome. Thus, this study demonstrates for the first time that the different sHLA-G subcomponents represent dissimilar qualitative prognostic impacts on the clinical outcome of NACT treated BC patients, whereas the total sHLA-G levels without separating into subcomponents are not related to clinical outcome.

High levels of soluble MICA are significantly related to increased disease-free and disease-specific survival in patients with cervical adenocarcinoma

Downregulation of major histocompatibility complex class I chain-related molecule A (MICA) and upregulation of human leukocyte antigen G (HLA-G) on the tumor cells are important immune escape mechanisms for different epithelial tumors. In addition, upregulation of the soluble forms of the latter molecules in serum leads to peripheral T-cell and natural killer (NK)-cell tolerance. As for cervical cancer, it remains unknown whether soluble MICA (sMICA) and soluble HLA-G (sHLA-G) concentrations are related to tumor characteristics or patient survival rates. We measured sMICA and sHLA-G in pre-treatment sera of a large cohort of cervical cancer patients (n = 366) by enzyme-linked immunosorbent assay (ELISA). We detected a median sMICA of 174.73 pg/ml and a median sHLA-G of 5.35 U/ml. We did not find an association between sHLA-G levels and clinicopathological characteristics. In adenocarcinoma, low sMICA concentration was positively related to recurrent disease, a higher International Federation of Gynecology and Obstetrics (FIGO) stage and vaginal involvement (Mann-Whitney U-test; P = 0.018, P = 0.042 and P = 0.013, respectively). In the latter patient group, high sMICA levels were associated with better disease-free survival (DFS) and disease-specific survival (DSS) (P = 0.011 and P = 0.047). After adjusting for confounding factors, high sMICA proved to be an independent predictor for a better DFS and DSS [HR 0.16; 95% confidence interval (CI) 0.04-0.64; P = 0.009 and HR 0.12; 95% CI 0.03-0.50; P = 0.004]. sHLA-G did not influence survival in cervical cancer patients, regardless of histology. We conclude that cervical adenocarcinoma patients with high sMICA levels have an increased DFS and DSS. This data warrants a prospective trial to study the functional role of sMICA in cervical adenocarcinoma.

Analysis of Il-10 gene sequence in patients with sinonasal polyposis

Sinonasal polyposis (SNP) is a chronic inflammatory disease of nasal and paranasal cavities. Human leukocyte antigen-G molecules (HLA-G) are non-classic HLA-I molecules with anti-inflammatory and tolerogenic properties. HLA-G production is mainly induced by interleukin (IL)-10. IL-10 is an anti-inflammatory cytokine that inhibits the production of proinflammatory cytokines and induces HLA-class II down-modulation. Recent studies suggest that HLA-G could play a role in SNP pathogenesis; in SNP patients physiological levels of IL-10 (produced by activated peripheral blood CD14+ monocytes) are not able to induce production of HLA-G. Different mechanisms could justify these findings: genomic or amino-acidic sequence alterations in IL-10 lower IL-10 receptor expression, lower IL-10 receptor affinity, or alterations of the intracellular signal transmission. This study analyzes nucleotidic sequence of IL-10 gene in SNP patients. Sequencing of IL-10 gene shows that the lack of HLA-G production by peripheral blood CD14+ monocytes is not related to alterations in IL-10 gene nucleotidic sequence.

Human leukocyte antigen (HLA)-G and cervical cancer immunoediting: a candidate molecule for therapeutic intervention and prognostic biomarker?

While persistent infection with oncogenic types of human Papillomavirus (HPV) is required for cervical epithelial cell transformation and cervical carcinogenesis, HPV infection alone is not sufficient to induce tumorigenesis. Only a minor fraction of HPV infections produce high-grade lesions and cervical cancer, suggesting complex host-virus interactions. Based on its pronounced immunoinhibitory properties, human leukocyte antigen (HLA)-G has been proposed as a possible prognostic biomarker and therapeutic target relevant in a wide variety of cancers and viral infections, but to date remains underexplored in cervical cancer. Given the possible influence of HLA-G on the clinical course of HPV infection, cervical lesions and cancer progression, a better understanding of HLA-G involvement in cervical carcinogenesis might contribute to two aspects of fundamental importance: 1. Characterization of a novel diagnostic/prognostic biomarker to identify cervical cancer and to monitor disease stage, critical for patient screening; 2. Identification of HLA-G-driven immune mechanisms involved in lesion development and cancer progression, leading to the development of strategies for modulating HLA-G expression for treatment purposes. Thus, this systematic review explores the potential involvement of HLA-G protein expression and polymorphisms in cervical carcinogenesis.

Mechanisms of intimate and long-distance cross-talk between glioma and myeloid cells: how to break a vicious cycle

Glioma-associated microglia and macrophages (GAMs) and myeloid-derived suppressor cells (MDSCs) condition the glioma microenvironment to generate an immunosuppressed niche for tumour expansion. This immunosuppressive microenvironment is considered to be shaped through a complex multi-step interactive process between glioma cells, GAMs and MDSCs. Glioma cells recruit GAMs and MDSCs to the tumour site and block their maturation. Glioma cell-derived factors subsequently skew these cells towards an immunosuppressive, tumour-promoting phenotype. Finally, GAMs and MDSCs enhance immune suppression in the glioma microenvironment and promote glioma growth, invasiveness, and neovascularization. The local and distant cross-talk between glioma cells and GAMs and MDSCs is regulated by a plethora of soluble proteins and cell surface-bound factors, and possibly via extracellular vesicles and platelets. Importantly, GAMs and MDSCs have been reported to impair the efficacy of glioma therapy, in particular immunotherapeutic approaches. Therefore, advancing our understanding of the function of GAMs and MDSCs in brain tumours and targeted intervention of their immunosuppressive function may benefit the treatment of glioma.

HLA-G as a tolerogenic molecule in transplantation and pregnancy

HLA-G is a nonclassical HLA class I molecule. In allogeneic situations such as pregnancy or allograft transplantation, the expression of HLA-G has been related to a better acceptance of the fetus or the allograft. Thus, it seems that HLA-G is crucially involved in mechanisms shaping an allogeneic immune response into tolerance. In this contribution we focus on (i) how HLA-G is involved in transplantation and human reproduction, (ii) how HLA-G is regulated by genetic and microenvironmental factors, and (iii) how HLA-G can offer novel perspectives with respect to therapy.

Role of the innate immunity in female reproductive tract

The mucosal immune system in the female reproductive tract (FRT) is well equipped to meet the sexually transmitted pathogens, allogeneic sperm, and the immunologically distinct fetus. Analysis of the FRT indicates that epithelial cells provide a physical barrier against pathogens and microbial infections as well as secretions containing anti-microbial peptides, cytokines, and chemokines which recruit and activate immune cells. Epithelial and immune cells confer protection in part through Toll-like receptors. The aim of this literature is to review the diverse components of the innate immune system, contributing to an exclusive protection system throughout the FRT.

Role of non-classical MHC class I molecules in cancer immunosuppression

Growing neoplasms employ various mechanisms to evade immunosurveillance. The expression of non-classical MHC class I molecules by both immune and malignant cells in the tumor microenvironment constitute of the strategies used by tumors to circumvent the cytotoxic activity of effector cells of the immune system. The overexpression of HLA-G, -E, and -F is a common finding across a variety of malignancies. However, while the presence of HLA-G and HLA-E has been recently correlated with poor clinical outcome, information on the clinicopathological significance of HLA-F is limited. In the present review, we summarize studies on non-classical MHC class I molecules with special emphasis on their role in the modulation of anticancer immune responses.

HLA-dependent tumour development: a role for tumour associate macrophages?

HLA abnormalities on tumour cells for immune escape have been widely described. In addition, cellular components of the tumour microenvironment, in particular myeloid derived suppressor cells (MDSC) and alternatively activated M2 tumour-associated macrophages (TAMs), are involved in tumour promotion, progression, angiogenesis and suppression of anti-tumour immunity. However, the role of HLA in these activities is poorly understood. This review details MHC class I characteristics and describes MHC class I receptors functions. This analysis established the basis for a reflection about the crosstalk among the tumour cells, the TAMs and the cells mediating an immune response.The tumour cells and TAMs exploit MHC class I molecules to modulate the surrounding immune cells. HLA A, B, C and G molecules down-regulate the macrophage myeloid activation through the interaction with the inhibitory LILRB receptors. HLA A, B, C are able to engage inhibitory KIR receptors negatively regulating the Natural Killer and cytotoxic T lymphocytes function while HLA-G induces the secretion of pro-angiogenic cytokines and chemokine thanks to an activator KIR receptor expressed by a minority of peripheral NK cells. The open conformer of classical MHC-I is able to interact with LILRA receptors described as being associated to the Th2-type cytokine response, triggering a condition for the M2 like TAM polarization. In addition, HLA-E antigens on the surface of the TAMs bind the inhibitory receptor CD94/NKG2A expressed by a subset of NK cells and activated cytotoxic T lymphocytes protecting from the cytolysis.Furthermore MHC class II expression by antigen presenting cells is finely regulated by factors provided with immunological capacities. Tumour-associated macrophages show an epigenetically controlled down-regulation of the MHC class II expression induced by the decoy receptor DcR3, a member of the TNFR, which further enhances the M2-like polarization. BAT3, a positive regulator of MHC class II expression in normal macrophages, seems to be secreted by TAMs, consequently lacking its intracellular function, it looks like acting as an immunosuppressive factor.In conclusion HLA could cover a considerable role in tumour-development orchestrated by tumour-associated macrophages.

Suppression of natural killer cell cytotoxicity in postpartum women: time course and potential mechanisms

Little is known about the recovery of the immune system from normal pregnancy and whether the postpartum period is a uniquely adapted immune state. This report extends previous observations from our group of decreased natural killer (NK) cell cytotoxicity in the postpartum period. NK cytotoxicity was measured from 1 week through 9 months postpartum. In addition, NK cytotoxicity was assayed in the presence or absence of pooled plasmas collected from either postpartum or nonpostpartum women. Samples of cells were stained for inhibitory receptors and analyzed by flow cytometry. NK cytotoxicity remained decreased in postpartum women compared to controls through the first 6 postpartum months, returned to normal levels by 9 months, and remained normal at 12 months. NK cytotoxicity during the first 6 months was further inhibited by the addition of pooled plasma to NK cultures from postpartum women, but the addition of pooled plasma from the control group did not affect that group's NK cultures. There were differences in inhibitory receptor staining between the two groups, with decreased CD158a and CD158b and increased NKG2A expression on postpartum NK cells during the first 3 postpartum months. These data suggest that NK cytotoxicity postpartum inhibition lasts 6 months and is influenced by unidentified postpartum plasma components. The effect may also involve receptors on NK cells.

Ovarian cancer molecular pathology

Ovarian cancer (OVC) is the fourth leading cause of cancer mortality among women in Europe and the United States. Its early detection is difficult due to the lack of specificity of clinical symptoms. Unfortunately, late diagnosis is a major contributor to the poor survival rates for OVC, which can be attributed to the lack of specific sets of markers. Aside from patients sharing a strong family history of ovarian and breast cancer, including the BRCA1 and BRCA2 tumor suppressor genes mutations, the most used biomarker is the Cancer-antigen 125 (CA-125). CA-125 has a sensitivity of 80 % and a specificity of 97 % in epithelial cancer (stage III or IV). However, its sensitivity is 30 % in stage I cancer, as its increase is linked to several physiological phenomena and benign situations. CA-125 is particularly useful for at-risk population diagnosis and to assess response to treatment. It is clear that alone, CA-125 is inadequate as a biomarker for OVC diagnosis. There is an unmet need to identify additional biomarkers. Novel and more sensitive proteomic strategies such as MALDI mass spectrometry imaging studies are well suited to identify better markers for both diagnosis and prognosis. In the present review, we will focus on such proteomic strategies in regards to OVC signaling pathways, OVC development and escape from the immune response.

Role of HLA-G and other immune mechanisms in pregnancy

Pregnancy loss (abortion) and pre-eclampsia represent the most common disorders in pregnant women. Besides infection, there are anatomical, endocrinological, genetic and immunological factors that can induce pregnancy disorders. Because the exact mechanisms of physiological pregnancy maintenance are still not clearly understood, the search for genes and proteins fulfilling this role is still in progress. One of the immune molecules that plays a beneficial role in pregnancy is the nonclassical HLA-G molecule. The molecule is mainly expressed on trophoblast cells in the foetal placenta and induces the immune tolerance of the foetus via its interaction with inhibitory receptors on maternal NK cells and CD8+ T lymphocytes. In relation to pregnancy disorders, associations between HLA-G polymorphism, HLA-G level and HLA-G function were described. Thus, the HLA-G molecule can be used as a new diagnostic marker and, potentially, for the future therapy of pregnancy disorders.

Biomarkers in uterine leiomyoma

Biomarkers are biologic compounds that are easily accessible and reflect normal physiology or pathology. They are useful in a variety of clinical situations that involve detection of subclinical disease, risk stratification, preoperative planning, and monitoring treatment. A useful intervention needs to exist for a biomarker to be an effective tool. Many compounds have been investigated as potential biomarkers for the diagnosis and surveillance of uterine leiomyomas. Most of these compounds demonstrate subtle differences among patients when leiomyomas are compared with controls. The compounds investigated lack the diagnostic accuracy necessary to add any benefit to the current available modalities used to diagnose and monitor uterine leiomyomas.

KIR2DL4 (CD158d): An activation receptor for HLA-G

KIR2DL4 is an unusual killer cell immunoglobulin-like receptor (KIR) family member in terms of its structure, expression, cellular localization, and signaling properties. The most conserved KIR in evolution, it is referred to as a framework KIR gene and is expressed by all natural killer (NK) cells and a subset of T cells. Although it has a long cytoplasmic tail that is typical of inhibitory KIR, engagement of this receptor results in the activation of NK cells, not for cytotoxicity, but for cytokine and chemokine secretion. Unlike all other KIRs, which are expressed on the surface of NK cells, KIR2DL4 resides in endosomes. It signals from this intracellular site for a proinflammatory and proangiogenic response, using a novel endosomal signaling pathway that involves the serine/threonine kinases DNA-PKcs and Akt. The only known ligand of KIR2DL4 is HLA-G. Soluble HLA-G accumulates in KIR2DL4⁺ endosomes. Unlike classical HLA molecules that serve as ligands for other KIR family members, in healthy individuals, HLA-G expression is restricted to the fetal trophoblast cells that invade the maternal decidua during early pregnancy. Since NK cells constitute the predominant lymphocyte subset at this site, the proinflammatory/proangiogenic outcome of the interaction between KIR2DL4 and soluble HLA-G supports a role for KIR2DL4 in the extensive remodeling of the maternal vasculature during the early weeks of pregnancy.

The immunosuppressive molecule HLA-G and its clinical implications

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex (MHC) class I molecule that, through interaction with its receptors, exerts important tolerogenic functions. Its main physiological expression occurs in placenta where it seems to participate in the maternal tolerance toward the fetus. HLA-G has been studied as a marker of pregnancy complications such as abortion or pre-eclapmsia. Although HLA-G is not expressed in most adult tissues, its ectopic expression has been observed in some diseases such as viral infections, autoimmune disorders, and especially cancer. HLA-G neo-expression in cancer is associated with the capability of tumor cells to evade the immune control. In this review, we will summarize HLA-G biology and how it participates in these physiopathological processes. Special attention will be paid to its role as a diagnostic tool and also as a therapeutic target.

Serum soluble HLA-E in melanoma: a new potential immune-related marker in cancer

BACKGROUND

Tumor-derived soluble factors, including soluble HLA molecules, can contribute to cancer immune escape and therefore impact on clinical course of malignant diseases. We previously reported that melanoma cells produce, in vitro, soluble forms of the non-classical MHC class I molecule HLA-E (sHLA-E). In order to investigate sHLA-E production by various tumors and to address its potential value as a tumor-associated marker, we developed a specific ELISA for the quantification of sHLA-E in biological fluids.

METHODOLOGY/PRINCIPAL FINDINGS

We developed a sHLA-E specific and sensitive ELISA and we showed that serum sHLA-E levels were significantly elevated (P<0.01) in melanoma patients (n = 127), compared with healthy donors (n = 94). sHLA-E was also detected in the culture supernatants of a wide variety of tumor cell lines (n = 98) including melanomas, kidney, colorectal and breast cancers. Cytokines regulation of sHLA-E production by tumor cells was also carried out. IFN-γ, IFN-α and TNF-α were found to upregulate sHLA-E production by tumor cells.

CONCLUSIONS/SIGNIFICANCE

In view of the broad tumor tissue release of HLA-E and its up-regulation by inflammatory cytokines, sHLA-E should be studied for its involvement in immune responses against tumors. Interestingly, our results demonstrated a positive association between the presence of serum sHLA-E and melanoma. Therefore, the determination of sHLA-E levels, using ELISA approach, may be investigated as a clinical marker in cancer patients.

Identification of circulating nonclassic human leukocyte antigen G (HLA-G)-like molecules in exudates

BACKGROUND

HLA-G in biological fluids has been proposed to be useful as a tumor marker as both a diagnostic and prognostic factor. Most HLA-G measurement procedures are based on ELISA methods using highly specific antibodies. However, results of published studies are in conflict regarding the clinical utility and even the nature of HLA-G present in circulation.

METHODS

We collected 118 exudates, 94 from cancer patients and 24 from patients without tumors. We measured HLA-G concentrations by ELISA using MEM-G/9 or G233 as capture antibody. Samples were immunoprecipitated with an anti-HLA-G antibody and analyzed by Western blot using a different anti-HLA-G antibody.

RESULTS

Discrepancies in HLA-G concentrations in exudates were observed depending on what capture anti-HLA-G antibody was used for ELISA (r = 0.376). These discrepancies were not observed when the ELISAs were performed using culture supernatants from HLA-G1-transfected cells (r = 0.983). Immunoprecipitation and Western blot of cell culture supernatants with 2 different anti-HLA-G antibodies produced the typical band at 39 kDa assigned to HLA-G. When the immunoprecipitation and western blot were performed with exudates, however, there were bands at 53 kDa and 70-76 kDa, higher molecular weights than those usually assigned to HLA-G. These HLA-G-like molecules were associated with β(2)-microglobulin and could also form disulfide bridges with other HLA-G-like molecules.

CONCLUSIONS

The main HLA-G antigenic molecules in exudates are HLA-G-like complexes, a factor that should be considered when analyzing HLA-G in biological fluids.

The immunohistochemical analysis of RCAS1, HLA-G, and B7H4-positive macrophages in partial and complete hydatidiform mole in both applied therapeutic surgery and surgery followed by chemotherapy

INTRODUCTION

The suppressive microenvironment developing around the implantating ovum in normal pregnant women may correlate with the development in cancer patients of a suppressive microenvironment of neoplasmatic cells derived from trophoblasts, such as occurs in molar lesions. Macrophages are suitable candidates for mediating not only the balance of the maternal defensive immune responses to external antigens, but also a tolerance to tumor cells. The aim of our study has been to gain information about the expression of RCAS1, B7H4, and HLA-G within the macrophages present in the microenvironment of the molar lesion.

METHODS

We analyzed the immunoreactivity of such antigens as B7H4, RCAS1, and HLA-G on the macrophages present in tissue samples derived from patients on whom curettage was performed after a diagnosis of molar pregnancy. These patients were then divided into two subgroups according to whether or not they required chemotherapy after the surgical procedure.

RESULTS

We observed a statistically significant increase in the RCAS1-positive macrophage infiltration within the microenvironment of the molar lesions in patients with partial hydatidiform mole in comparison with those patients who exhibited complete hydatidiform mole. There were no such differences, however, in the infiltration of HLA-G- and B7H4-positive macrophages between the two groups of patients. Additionally, we showed that RCAS1- and HLA-G-positive macrophages are more distinct in those cases of complete molar pregnancy where chemotherapy was necessary after surgical treatment while no such differences with respect to B7H4-positive macrophages were observed.

CONCLUSION

The immune-suppressive endometrial microenvironment represented by suppressive macrophages may have an influence on the clinical course of hydatidiform mole.

Expression of HLA-G in patients with hepatocellular carcinoma

BACKGROUND

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex class I molecule that has multiple immune regulatory functions including the induction of immune tolerance. The detection of HLA-G expression might serve as a clinical marker in the prediction of clinical outcomes for certain types of carcinoma. Currently, we investigated whether or not HLA-G is also expressed in patients with hepatocellular carcinoma (HCC), and whether the expression has clinical value.

METHODS

Serum levels of secreted HLA-G (sHLA-G) were measured by ELISA in 36 patients with HCC, 25 patients with liver cirrhosis (LC) and 25 healthy individuals. The expression of HLA-G in liver tissue was further studied using Western blotting in 36 patients with HCC and 25 with LC. The correlations between HLA-G status and various clinicopathological parameters including survival were analyzed.

RESULTS

The ELISA assay showed that the serum levels of sHLA-G in the HCC, LC and healthy groups were 132.6+/-31.4, 63.5+/-22.1, and 47.0+/-15.5 U/ml, respectively. Analysis of variance was used for inter-group comparison and differences were found between the HCC group and the other two groups (both P<0.01), while no difference was found between the LC group and the healthy group (P=0.112). HLA-G protein expression in liver tissue was found in 66.7% (24/36) of the primary sites of HCC, but not in benign lesions (LC). Further, the HLA-G expression in tumors had no significant correlation with the parameters of age, gender, histological grade and alpha-fetoprotein level. However, patients with HLA-G-positive tumors had a shorter postoperative survival time than those with HLA-G-negative tumors (P=0.014). Also, univariate analysis showed that HLA-G was an independent prognostic factor.

CONCLUSION

Our results indicated that the expression of HLA-G was a characteristic feature of HCC and patients with positive expression of HLA-G in malignant liver tissue had a poor prognosis.

Clinical relevance and functional implications for human leucocyte antigen-g expression in non-small-cell lung cancer

HLA-G has been documented both in establishment of anti-tumour immune responses and in tumour evasion. To investigate the clinical relevance of HLA-G in non-small-cell lung cancer (NSCLC), expression status and potential significance of HLA-G in NSCLC were analysed. In this study, HLA-G expression in 101 NSCLC primary lesions and plasma soluble HLA-G (sHLA-G) from 91 patients were analysed with immunohistochemistry and ELISA, respectively. Correlations between HLA-G status and various clinical parameters including survival time were evaluated. Meanwhile, functional analysis of transfected cell surface HLA-G expression and plasma sHLA-G form NSCLC patients on natural killer (NK) cell cytolysis were performed. Data revealed that HLA-G was expressed in 41.6% (42/101) NSCLC primary lesions, while undetectable in adjacent normal lung tissues. HLA-G expression in NSCLC lesions was strongly correlated to disease stages (P= 0.002). Plasma sHLA-G from NSCLC patients was markedly higher than that in normal controls (P= 0.004), which was significantly associated with the disease stages (I versus IV, P= 0.025; II versus IV, P= 0.029). Patient plasma sHLA-G level (≥median, 32.0 U/ml) had a significantly shorter survival time (P= 0.044); however, no similar significance was observed for the lesion HLA-G expression. In vitro data showed that both cell surface HLA-G and patient plasma sHLA-G could dramatically decrease the NK cell cytolysis. Our findings indicated that both lesion HLA-G expression and plasma sHLA-G in NSCLC is related to the disease stage and can exert immunosuppression to the NK cell cytolysis, indicating that HLA-G could be a potential therapeutic target. Moreover, plasma sHLA-G in NSCLC patients could be used as a prognosis factor for NSCLC.

Aberrant human leucocyte antigen-G expression and its clinical relevance in hepatocellular carcinoma

The clinical relevance of human leucocyte antigen-G (HLA-G) has been postulated in malignancies. Hepatocellular carcinoma (HCC) is a major contributor to cancer incidence and mortality worldwide; however, potential roles of HLA-G in HCC remain unknown. In the current study, HLA-G expression in 219 primary HCC lesions and their adjacent non-tumourous samples was analysed with immunohistochemistry. Correlations among HLA-G expression and various clinical parameters were evaluated. Meanwhile, functional analysis of transfected cell surface HLA-G expression on NK cell cytolysis was performed in vitro. HLA-G expression was observed in 50.2% (110/219) of primary HCC lesions, and undetectable in corresponding adjacent normal liver tissues. HLA-G expression was found in 37.8%, 41.9% and 71.4% of stage I, II and III HCC lesions, respectively. Data revealed that HLA-G expression in HCC was strongly correlated to advanced disease stage (I versus II, P= 0.882; I versus III, P= 0.020; II versus III, P= 0.037). HLA-G expression was also more frequently observed in elder patients (≥median 52 years, 57.5%versus 43.4%, P= 0.004). Meanwhile, plasma soluble HLA-G in HCC patients was significantly higher than that in normal controls (median, 92.49U/ml versus 9.29U/ml, P= 0.000). Functional assay showed that HLA-G expression in transfected cells could dramatically decrease the NK cell cytolysis (P= 0.036), which could be markedly restored by the blockade of HLA-G (P= 0.004) and its receptor ILT2 (P= 0.019). Our finding indicated that HLA-G expression was strongly correlated to advanced disease stage, and more frequently observed in elder patients. Its relevance to HCC progression might be result from the inhibition of NK cell cytolysis.

Increased soluble human leukocyte antigen-G levels in peripheral blood from climbers on Mount Everest

Soluble human leukocyte antigen-G (HLA-G) is involved in maternal-fetal tolerance, transplant acceptance, and tumor escape from immunosurveillance, operating by inhibiting activity of T, antigen presenting cells (APC), and natural killer (NK) cells. HLA-G gene expression is modulated in vitro after hypoxic conditions, a situation evidenced during pregnancy and tumor progression. In extreme altitude, mountaineers are in hypoxic conditions that generate physiologic adaptative responses, some of them giving rise to pathologic signs. We performed measurements of plasma soluble HLA-G in six climbers before departure of the expedition and during their ascent to and descent from summit of Mount Everest, and in 3 Sherpas at 5300-6400 m. We found that HLA-G levels are upregulated during the ascent with a unique pattern in comparison with angiogenic/lymphangiogenic factors. Our data suggest that HLA-G has to be taken into account in the mechanisms participating in adaptation to high altitudes and reinforce hypoxia as an important factor in the regulation of HLA-G expression.