HLA-G is differentially expressed in thyroid tissues

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.

HLA-G Gene Variability Is Associated with Papillary Thyroid Carcinoma Morbidity and the HLA-G Protein Profile

Human leukocyte antigen (HLA)-G is an immune checkpoint molecule that is highly expressed in papillary thyroid carcinoma (PTC). The HLA-G gene presents several functional polymorphisms distributed across the coding and regulatory regions (5'URR: 5' upstream regulatory region and 3'UTR: 3' untranslated region) and some of them may impact HLA-G expression and human malignancy. To understand the contribution of the HLA-G genetic background in PTC, we studied the HLA-G gene variability in PTC patients in association with tumor morbidity, HLA-G tissue expression, and plasma soluble (sHLA-G) levels. We evaluated 185 PTC patients and 154 healthy controls. Polymorphic sites defining coding, regulatory and extended haplotypes were characterized by sequencing analyses. HLA-G tissue expression and plasma soluble HLA-G levels were evaluated by immunohistochemistry and ELISA, respectively. Compared to the controls, the G0104a(5'URR)G*01:04:04(coding)UTR-03(3'UTR) extended haplotype was underrepresented in the PTC patients, while G0104a(5'URR)G*01:04:01(coding)UTR-03(3'UTR) was less frequent in patients with metastatic and multifocal tumors. Decreased HLA-G tissue expression and undetectable plasma sHLA-G were associated with the G010102a(5'URR)G*01:01:02:01(coding)UTR-02(3'UTR) extended haplotype. We concluded that the HLA-G variability was associated with PTC development and morbidity, as well as the magnitude of the encoded protein expression at local and systemic levels.

BRAF, TERT and HLA-G Status in the Papillary Thyroid Carcinoma: A Clinicopathological Association Study

As BRAF, TERT, HLA-G, and microRNAs have been individually associated with papillary thyroid carcinoma (PTC), we aimed to evaluate the individual and collaborative role of these markers in PTC in the same patient cohort. HLA-G and BRAF tumor expression was evaluated by immunohistochemistry. Using molecular methods, BRAFV600E and TERT promoter mutations were evaluated in thyroid fine needle aspirates. MicroRNA tumor profiling was investigated using massively parallel sequencing. We observed strong HLA-G (67.96%) while BRAF (62.43%) staining was observed in PTC specimens. BRAF overexpression was associated with poor response to therapy. The BRAFV600E (52.9%) and TERTC228T (13%) mutations were associated with extrathyroidal extension, advanced-age, and advanced-stage cancer. The TERT rs2853669 CC+TC genotypes (38%) were overrepresented in metastatic tumors. Nine modulated microRNAs targeting the BRAF, TERT, and/or HLA-G genes were observed in PTC and involved with cancer-related signaling pathways. The markers were individually associated with PTC features, emphasizing the synergistic effect of BRAFV600E and TERTC228T; however, their collaborative role on PTC outcome was not fully demonstrated. The differentially expressed miRNAs targeting the BRAF and/or HLA-G genes may explain their increased expression in the tumor milieu.

HLA-G/sHLA-G and HLA-G-Bearing Extracellular Vesicles in Cancers: Potential Role as Biomarkers

As a non-classic major histocompatibility complex (MHC) class I molecule, human leukocyte antigen G (HLA-G) is expressed in fetal-maternal interface and immunoprivileged site only in healthy condition, and in pathological conditions such as cancer, it can be de novo expressed. It is now widely accepted that HLA-G is a key molecule in the process of immune escape of cancer cells, which is ubiquitously expressed in the tumor environment. This raises the possibility that it may play an adverse role in tumor immunity. The expression level of HLA-G has been demonstrated to be highly correlated with clinical parameters in many tumors, and its potential significance in the diagnosis and prognosis of cancer has been postulated. However, because HLA-G itself has up to seven different subtypes, and for some subtypes, detected antibodies are few or absent, it is hard to evaluate the actual expression of HLA-G in tumors. In the present work, we described (a) the structure and three main forms of HLA-G, (b) summarized the mechanism of HLA-G in the immune escape of tumor cells, (c) discussed the potential role of HLA-G as a tumor marker, and reviewed (d) the methods for detecting and quantifying HLA-G.

A Critical Assessment of the Association between HLA-G Expression by Carcinomas and Clinical Outcome

Human leukocyte antigen-G (HLA-G) conveys immunological tolerance at the maternal-foetal interface. HLA-G expression by tumour cells may also play such a role, resulting in tumour immune evasion, making HLA-G a potential target for immunotherapies. The aim of this review was to determine to what extent it is justified that HLA-G expression is considered as a target for immune checkpoint inhibiting therapy by critically assessing the association between HLA-G expression by carcinomas and clinical outcome of patients. The used HLA-G-detecting mAb, HLA-G quantification methods and statistically significant HLA-G-associated clinicopathological parameters are discussed. Tumour HLA-G expression correlated with poor clinical outcome in breast, esophageal, gastric and hepatocellular carcinoma patients. Tumour HLA-G expression was not associated with clinical outcome in ovarian and oral carcinoma patients. Cervical, colorectal, lung, and pancreatic carcinoma patients presented discrepant and therefore inconclusive results regarding the association between tumour HLA-G expression and clinical outcome. These disparities might partly be the result of differences in the methodological approach to quantify HLA-G expression between studies. Therefore, implementation of universal methodological procedures is strongly advised. Overall, HLA-G expression did not univocally result in poor clinical outcome of carcinoma patients. This implies that tumour HLA-G expression is not necessarily part of an inhibited tumour-immune response and tumour progression. Consequently, it remains elusive whether HLA-G expression by carcinomas functions as an immune checkpoint molecule affecting a tumour-immune response. It may also reflect derailed control of gene expression in tumours, with no real functional consequences.

Comprehensive Transcriptomic Analysis Reveals the Role of the Immune Checkpoint HLA-G Molecule in Cancers

Human leukocyte antigen G (HLA-G) is known as a novel immune checkpoint molecule in cancer; thus, HLA-G and its receptors might be targets for immune checkpoint blockade in cancer immunotherapy. The aim of this study was to systematically identify the roles of checkpoint HLA-G molecules across various types of cancer. ONCOMINE, GEPIA, CCLE, TRRUST, HAP, PrognoScan, Kaplan-Meier Plotter, cBioPortal, LinkedOmics, STRING, GeneMANIA, DAVID, TIMER, and CIBERSORT were utilized. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed. In this study, we comprehensively analysed the heterogeneous expression of HLA-G molecules in various types of cancer and focused on genetic alterations, coexpression patterns, gene interaction networks, HLA-G interactors, and the relationships between HLA-G and pathological stage, prognosis, and tumor-infiltrating immune cells. We first identified that the mRNA expression levels of HLA-G were significantly upregulated in both most tumor tissues and tumor cell lines on the basis of in-depth analysis of RNAseq data. The expression levels of HLA-G were positively associated with those of the other immune checkpoints PD-1 and CTLA-4. Abnormal expression of HLA-G was significantly correlated with the pathological stage of some but not all tumor types. There was a significant difference between the high and low HLA-G expression groups in terms of overall survival (OS) or disease-free survival (DFS). The results showed that HLA-G highly expressed have positive associations with tumor-infiltrating immune cells in the microenvironment in most types of tumors (P<0.05). Additionally, we identified the key transcription factor (TF) targets in the regulation of HLA-G expression, including HIVEP2, MYCN, CIITA, MYC, and IRF1. Multiple mutations (missense, truncating, etc.) and the methylation status of the HLA-G gene may explain the differential expression of HLA-G across different tumors. Functional enrichment analysis showed that HLA-G was primarily related to T cell activation, T cell regulation, and lymphocyte-mediated immunity. The data may provide novel insights for blockade of the HLA-G/ILT axis, which holds potential for the development of more effective antitumour treatments.

HLA-G/ILTs Targeted Solid Cancer Immunotherapy: Opportunities and Challenges

Immune checkpoint inhibitors (ICIs) have become a promising immunotherapy for cancers. Human leukocyte antigen-G (HLA-G), a neoantigen, its biological functions and clinical relevance have been extensively investigated in malignancies, and early clinical trials with “anti-HLA-G strategy” are being launched for advance solid cancer immunotherapy. The mechanism of HLA-G as a new ICI is that HLA-G can bind immune cell bearing inhibitory receptors, the immunoglobulin-like transcript (ILT)-2 and ILT-4. HLA-G/ILT-2/-4 (HLA-G/ILTs) signaling can drive comprehensive immune suppression, promote tumor growth and disease progression. Though clinical benefits could be expected with application of HLA-G antibodies to blockade the HLA-G/ILTs signaling in solid cancer immunotherapy, major challenges with the diversity of HLA-G isoforms, HLA-G/ILTs binding specificity, intra- and inter-tumor heterogeneity of HLA-G, lack of isoform-specific antibodies and validated assay protocols, which could dramatically affect the clinical efficacy. Clinical benefits of HLA-G-targeted solid cancer immunotherapy may be fluctuated or even premature unless major challenges are addressed.

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.

Inhibition of iNKT Cells by the HLA-G-ILT2 Checkpoint and Poor Stimulation by HLA-G-Expressing Tolerogenic DC

Invariant Natural Killer T (iNKT) cells are a small and distinct population of T cells crucial in immunomodulation. After activation by alpha-GalactosylCeramide (αGC), an exogenic glycolipid antigen, iNKT cells can rapidly release cytokines to enhance specific anti-tumor activity. Several human clinical trials on iNKT cell-based anti-cancer are ongoing, however results are not as striking as in murine models. Given that iNKT-based immunotherapies are dependent mainly on antigen-presenting cells (APC), a human tolerogenic molecule with no murine homolog, such as Human Leucocyte Antigen G (HLA-G), could contribute to this discrepancy. HLA-G is a well-known immune checkpoint molecule involved in fetal-maternal tolerance and in tumor immune escape. HLA-G exerts its immunomodulatory functions through the interaction with immune inhibitory receptors such as ILT2, differentially expressed on immune cell subsets. We hypothesized that HLA-G might inhibit iNKT function directly or by inducing tolerogenic APC leading to iNKT cell anergy, which could impact the results of current clinical trials. Using an ILT2-transduced murine iNKT cell line and human iNKT cells, we demonstrate that iNKT cells are sensitive to HLA-G, which inhibits their cytokine secretion. Furthermore, human HLA-G⁺ dendritic cells, called DC-10, failed at inducing iNKT cell activation compared to their autologous HLA-G^‒ DCs counterparts. Our data show for the first time that the HLA-G/ILT2 ICP is involved in iNKT cell function modulation.

The Potential of Soluble Human Leukocyte Antigen Molecules for Early Cancer Detection and Therapeutic Vaccine Design

Human leukocyte antigen (HLA) molecules are essential for anti-tumor immunity, as they display tumor-derived peptides to drive tumor eradication by cytotoxic T lymphocytes. HLA molecules are primarily studied as peptide-loaded complexes on cell membranes (mHLA) and much less attention is given to their secretion as soluble HLA–peptide complexes (sHLA) into bodily fluids. Yet sHLA levels are altered in various pathologies including cancer, and are thus of high interest as biomarkers. Disconcordance in results across studies, however, hampers interpretation and generalization of the relationship between sHLA levels and cancer presence, thereby impairing its use as a biomarker. Furthermore, the question remains to what extent sHLA complexes exert immunomodulatory effects and whether shifts in sHLA levels contribute to disease or are only a consequence of disease. sHLA complexes can also bear tumor-derived peptides and recent advancements in mass spectrometry now permit closer sHLA peptide cargo analysis. sHLA peptide cargo may represent a “liquid biopsy” that could facilitate the use of sHLA for cancer diagnosis and target identification for therapeutic vaccination. This review aims to outline the contradictory and unexplored aspects of sHLA and to provide direction on how the full potential of sHLA as a quantitative and qualitative biomarker can be exploited.

HLA-G: Function, polymorphisms and pathology

HLA-G immune modulatory genes and molecules are presently being studied by a widespread number of research groups. In the present study, we do not aim to be exhaustive since the number of manuscripts published every year is overwhelming. Instead, our aim is pointing out facts about HLA-G function, polymorphism and pathology that have been confirmed by several different researchers, together with exposing aspects that may have been overlooked or not sufficiently remarked in this productive field of study. On the other hand, we question whether performing mainly studies on HLA-G and disease associations is going to give a clear answer in the future, since 40 years of study of classical HLA molecules association with disease has still given no definite answer on this issue.

Plasma levels of soluble HLA-G and cytokines in papillary thyroid carcinoma before and after thyroidectomy

BACKGROUND

Increasing evidence shows that chronic inflammation plays an important role in thyroid tumorigenesis. Cytokines as central mediators in inflammatory microenvironment can present both pro-tumour and anti-tumour effects and cytokine release may be influenced by soluble HLA-G (sHLA-G), an immune checkpoint molecule whose expression can also be induced by certain cytokines.

AIM

To understand the role of these soluble factors in papillary thyroid cancer (PTC).

METHODS

We evaluated plasma levels of sHLA-G and of 13 cytokines using ELISA and flow cytometry, respectively, in PTC patients at two time points: pre- and post-thyroidectomy; and control subjects.

RESULTS

Compared with controls, IL-6 levels were increased, while IL-1β, IFN-α and TGF-β1 levels were decreased in pre-thyroidectomy PTC patients. IFN-α and TGF-β1 efficiently discriminated patients from controls and were associated with extrathyroidal extension and lymph node metastasis, respectively. In addition, TNF and IL-13 were associated with male gender, lymph node metastasis and Hashimoto thyroiditis, and sHLA-G with tumour invasion. Compared with pre-thyroidectomy, IL-4, IL-10, TNF, IFN-α and TGF-β1 levels were increased in post-thyroidectomy.

CONCLUSION

There are significant changes in the cytokine profile after surgical removal of the thyroid tumour, and IFN-α e TGF-β1 showed to be promising cytokines for discriminating PTC patients from controls. We also found that different cytokines are associated with clinicohistopathological characteristics of PTC related to poor prognosis, suggesting that cytokines seem to play an important role in PTC development and management.

HLA-G Neo-Expression on Tumors

HLA-G is known to modulate the immune system activity in tissues where physiological immune-tolerance is necessary (i.e., maternal-fetal interface, thymus, and cornea). However, the frequent neo-expression of HLA-G in many cancer types has been previously and extensively described and is correlated with a bad prognosis. Despite being an MHC class I molecule, HLA-G is highly present in tumor context and shows unique characteristics of tissue restriction of a Tumor Associated Antigen (TAA), and potent immunosuppressive activity of an Immune CheckPoint (ICP). Consequently, HLA-G appears to be an excellent molecular target for immunotherapy. Although the relevance of HLA-G in cancer incidence and development has been proven in numerous tumors, its neo-expression pattern is still difficult to determine. Indeed, the estimation of HLA-G's actual expression in tumor tissue is limited, particularly concerning the presence and percentage of the new non-canonical isoforms, for which detection antibodies are scarce or inexistent. Here, we summarize the current knowledge about HLA-G neo-expression and implication in various tumor types, pointing out the need for the development of new tools to analyze in-depth the HLA-G neo-expression patterns, opening the way for the generation of new monoclonal antibodies and cell-based immunotherapies.

Human Antigen Leucocyte (HLA)-G and HLA-E are differentially expressed in pancreatic disorders

BACKGROUND

Little information is available regarding the expression of the immunomodulatory Human Leukocyte Antigen (HLA)-G and -E molecules in pancreatic disorders.

AIM

To analyze HLA-G and -E expression in specimens of alcoholic chronic pancreatitis (ACP), idiopathic chronic pancreatitis (ICP), type 1 (T1D) and type 2 diabetes (T2D) and in histologically normal pancreas (HNP).

METHODS

HLA-G and -E expression (ACP = 30, ICP = 10, T1D = 10, T2D = 30 and HNP = 20) was evaluated by immunohistochemistry in three different areas (acini, islets and inflammatory infiltrate).

RESULTS

Acini and islets from HNP specimens exhibited higher HLA-G and -E expression compared to corresponding areas from all other patient groups. In inflammatory infiltrate, HLA-G and -E expression was observed only among the pancreatic disorders. We observed higher HLA-G and -E expression in acini from T2D compared to ACP, as well as higher HLA-G expression compared to ICP.

CONCLUSION

The decreased expression of HLA-G and -E in islets and acini together with the expression of these molecules in the inflammatory infiltrating cells were shared features among chronic inflammatory and autoimmune pancreatic disorders evaluated in this study, possibly reflecting tissue damage.

Heterogeneity of HLA-G Expression in Cancers: Facing the Challenges

Phenotypic heterogeneity has been observed in most malignancies, which represents a considerable challenge for tumor therapy. In recent decades, the biological function and clinical significance of the human leukocyte antigen (HLA)-G have been intensively explored. It is now widely accepted that HLA-G is a critical marker of immunotolerance in cancer cell immune evasion and is strongly associated with disease progress and prognosis for cancer patients. Moreover, it has recently been emphasized that the signaling pathway linking HLA-G and immunoglobulin-like transcripts (ILTs) is considered an immune checkpoint. In addition, HLA-G itself can generate at least seven distinct isoforms, and intertumor and intratumor heterogeneity of HLA-G expression is common across different tumor types. Furthermore, HLA-G heterogeneity in cancers has been related to disease stage and outcomes, metastatic status and response to different therapies. This review focuses on the heterogeneity of HLA-G expression in malignant lesions, and clinical implications of this heterogeneity that might be relevant to personalized treatments are also discussed.

Human leukocyte antigen-G expression and polymorphisms promote cancer development and guide cancer diagnosis/treatment

Human leukocyte antigen-G (HLA-G) is a non-classical HLA molecule, predominantly expressed in cytotrophoblast cells to protect the fetus during pregnancy. Notably, a high frequency of HLA-G expression has been observed in a wide variety of cancer types in previous studies. Furthermore, HLA-G expression in cancer has been considered to be detrimental, since it can protect cancer cells from natural killer cell cytotoxic T lymphocyte-mediated destruction, promote tumor spreading and shorten the survival time of patients by facilitating tumor immune evasion. In addition, HLA-G polymorphisms have been investigated in numerous types of cancer and are considered as risk factors and predictive markers of cancer. This review focuses on HLA-G expression and its polymorphisms in cancer, analyzing the mechanisms of HLA-G in promoting cancer development, and evaluating the potential and value of its clinical application as a diagnostic and prognostic biomarker, or even as a prospective therapeutic target in certain types of tumors.

Plasma human leukocyte antigen-G (HLA-G) in patients with thyroid cancer

Background/aim: A number of tumor markers detected in the serum or pathological specimens using immunohistochemical methods are used for early detection of malignancies and postoperative follow-up. Human leukocyte antigen-G (HLA-G) is a nonclassic HLA class I molecule. Recent studies suggested a relationship between HLA-G positivity and the stage or the phenotype of the malignancy. In this study, the relationship between serum HLA-G positivity and thyroid cancer was investigated. Materials and methods: Fifty patients with thyroid cancer and 45 healthy volunteers were included in this study. Serum HLA-G levels were measured using ELISA. Results: HLA-G was positive in only 3 out of 50 patients with thyroid cancer (2 papillary, 1 follicular type). On the other hand, HLA-G was positive in 20 out of 45 healthy subjects (P < 0.001). The prevalence of detectable levels of serum HLA-G was independent of sex and age in the whole study population. No correlation was found between serum HLA-G value and thyroid hormone profile, neither in papillary thyroid cancer nor follicular thyroid cancer patients. Conclusion: In this study, serum HLA-G was significantly less common in patients with thyroid cancer than in healthy controls.

HLA-G 3' untranslated region polymorphic sites associated with increased HLA-G production are more frequent in patients exhibiting differentiated thyroid tumours

BACKGROUND

HLA-G is a nonclassical class I histocompatibility molecule implicated on the immune escape mechanism of tumour cells. We evaluated the genetic diversity of HLA-G 3' untranslated region (3'UTR) and associated polymorphic sites with clinical presentation and with the magnitude of HLA-G thyroid expression.

PATIENTS AND METHODS

Polymorphic sites at 3'UTR (14bpINS/DEL, +3003C/T, +3010C/G, +3027A/C, +3035C/T, +3142C/G, +3187A/G, +3196C/G) were characterized by sequencing analyses in blood samples of 72 patients exhibiting papillary thyroid carcinoma (PTC), 22 follicular thyroid carcinomas (FTC), 19 follicular adenomas (FA), 21 colloid goitres and 156 healthy controls.

RESULTS

Compared to goitre and/or controls, patients with PTC exhibited higher frequency of 14bpDEL (P = 0·030), +3010G (P = 0·034), +3010CG (P = 0·044), +3142CG (P = 0·040), +3035C (P = 0·050) and +3187GG (P = 0·032). Patients with FTC presented higher frequency of 14bpINS/DEL (P = 0·020). The UTR-5 haplotype was underrepresented in PTC (P = 0·050). The +3003TT was more frequent in patients with PTC older than 45 years (P = 0·030). Male patients had a higher frequency of +3196GG (P = 0·040). Tumour multicentricity was associated with UTR-2 (P = 0·030). The following associations were observed in PTC and FTC combined: i) tumour size <2 cm with 14bpINS/INS (P = 0·030); ii) multicentricity with +3035CC (P = 0·030) and +3196GG (P = 0·030); iii) decreased thyroid HLA-G expression with +3196C and +3196CC; and iv) moderate HLA-G thyroid staining with UTR-2.

CONCLUSIONS

HLA-G 3'UTR polymorphisms associated with a greater magnitude of HLA-G production were associated with differentiated thyroid tumours and with variables implicated in poor prognosis. These findings corroborate the unfavourable role of HLA-G in thyroid cancer.

High IL-17 expression is associated with an unfavorable prognosis in thyroid cancer

Previous studies have indicated that cancer may be promoted and/or exacerbated by inflammation and infection. The cytokines produced by activated innate immune cells that stimulate tumor growth and progression are considered as important components in this process. The interleukin (IL)-23/T helper (Th)17 axis, which exerts marked pro-inflammatory effects, has emerged as an important mediator in inflammation-associated cancer. Increasing clinical evidence indicates that Th17 may promote or inhibit tumor progression, however, the function of Th17 in the pathogenesis of benign and malignant thyroid neoplasms remains unclear. The present study investigated the association between the IL-23/Th17 axis and neoplastic and non-neoplastic thyroid lesions using immunohistochemistry. A total of 131 thyroid biopsy specimens were analyzed, which revealed high IL-17 and IL-23 expression in differentiated thyroid cancer and medullary thyroid cancer tissues when compared with benign lesions, including follicular thyroid adenoma and goiter tissues. Furthermore, high IL-17 expression was associated with recurrence and mortality. These results indicate that the IL-23/Th17 axis exhibits a pivotal function in the development of thyroid neoplasms.

Human leukocyte antigen-G overexpression predicts poor clinical outcomes in low-grade gliomas

Overexpression of human leukocyte antigen-G (HLA-G), a non-classical major histocompatibility complex class-I molecule associated with immunosuppression, has been reported in various human malignancies. In the present study, we examined the role of HLA-G in gliomas. Clinical characteristics, mRNA expression microarrays and follow-up data pertaining to 293 patients with histologically confirmed gliomas were analyzed. The expression levels of HLA-G were compared between different grades of gliomas and correlated with progression-free survival (PFS) and overall survival (OS) to evaluate its prognostic value. We found that HLA-G was overexpressed in gliomas as compared to that in normal brain tissue samples (-1.288±0.265). The highest expression levels were in glioblastomas (GBMs), anaplastic gliomas (AGs) and low-grade gliomas (LGGs), in that order (0.328±0.778, 0.176±0.881, -0.388±0.686, respectively). Significant inter-group differences were observed between low-grade and high-grade glioma tissues (p<0.001 and p<0.001, t-test, AGs and GBMs, respectively). More astrocytoma patients exhibited increased HLA-G expression as compared to other LGG patients (p=0.004, Chi-square test). Significant differences were observed with respect to PFS and OS (p=0.009 and 0.032, log-rank test, for PFS and OS, respectively) between the high- and low-expression subgroups in patients with LGGs. On Cox regression analysis, overexpression of HLA-G appeared to be an independent predictor of clinical outcomes (p=0.007 and 0.026, for PFS and OS, respectively). Our results suggest that HLA-G expression may serve as a potential biomarker for predicting aggressive tumor grades of gliomas and for histological subtype of LGGs. Elevated HLA-G expression could serve as an independent predictor of poor clinical outcomes in patients with low-grade gliomas.

Human Leukocyte Antigen-G (HLA-G) Expression in Cancers: Roles in Immune Evasion, Metastasis and Target for Therapy

Aberrant induction of human leukocyte antigen-G (HLA-G) expression has been observed in various malignancies and is strongly associated with tumor immune escape, metastasis and poor prognosis. To date, great achievements have been made in understanding the underlying mechanisms of HLA-G involved in tumor progression. HLA-G could lead to tumor evasion by inhibition of immune cell cytolysis, differentiation and proliferation and inhibition of cytokine production, induction of immune cell apoptosis, generation of regulatory cells and expansion of myeloid-derived suppressive cells and by impairment of chemotaxis. Moreover, HLA-G could arm tumor cells with a higher invasive and metastatic potential with the upregulation of tumor-promoting factor expression such as matrix metalloproteinases (MMPs), indicating that ectopic HLA-G expression could render multiple effects during the progression of malignancies. In this review, we summarized the mechanisms of HLA-G involved in promoting tumor cell immune escaping, metastasis and disease progression. Special attention will be paid to its significance as an attractive therapeutic target in cancers.

The Role of HLA-G Molecule and HLA-G Gene Polymorphisms in Tumors, Viral Hepatitis, and Parasitic Diseases

Considering that the non-classical HLA-G molecule has well-recognized tolerogenic properties, HLA-G expression is expected to be deleterious when present in tumor cells and in cells chronically infected by viruses, whereas HLA-G expression is expected to be advantageous in autoimmune disorders. The expression of HLA-G on tissue or peripheral blood cells, the levels of soluble HLA-G and polymorphic sites along the gene have been studied in several disorders. In this study, we revised the role of the molecule and polymorphic sites along the HLA-G gene in tumors, viral hepatitis, and parasitic disorders. Overall, several lines of evidence clearly show that the induction of HLA-G expression in tumors has been associated with worse disease outcome and disease spread. In addition, the few studies conducted on hepatitis and parasitic disorders indicate that HLA-G may contribute to disease pathogenesis. Few isolated polymorphic sites, primarily located at the coding or 3′ untranslated HLA-G region, have been evaluated in these disorders, and a complete HLA-G typing together with the study of gene regulatory elements may further help on the understanding of the influence of the genetic background on disease susceptibility.

BRAF V600E in papillary thyroid carcinoma is associated with increased programmed death ligand 1 expression and suppressive immune cell infiltration

BACKGROUND

There remain a small number of patients with papillary thyroid cancer (PTC) who suffer recurrence, metastases, or death. While mutation of the BRAF gene, corresponding to the constitutively active BRAF(V600E) protein, has been associated with worse clinical outcomes in thyroid cancer, the reasons underlying this observation are presently unknown. Disruption of endogenous host immune surveillance and promotion of tumor immune escape is one mechanism by which BRAF(V600E) tumors may achieve more aggressive behavior. This study evaluated the relationship between BRAF(V600E) status and known strategies of tumor-mediated immune suppression.

METHODS

Tissue sections of PTC tumors from 33 patients were evaluated by immunohistochemistry for tumor-expressed suppressive ligands and enzymes and effector and suppressor populations of tumor-infiltrating immune cells. Presence of BRAF(V600E) was evaluated by direct DNA sequencing of PTC specimens and the results correlated with tumor-expressed molecules and tumor-infiltrating immune cell populations, as well as patient characteristics and pathologic findings.

RESULTS

BRAF(V600E) tumors more often express high levels of immunosuppressive ligands programmed death ligand 1 (53% vs. 12.5%) and human leukocyte antigen G (41% vs. 12.5%) compared to BRAF wild-type tumors. There was no association between indoleamine 2,3-dioxygenase 1 expression and BRAF(V600E) status. Furthermore, BRAF(V600E) tumors demonstrate both lower CD8(+) effector to FoxP3(+) regulatory T cell, and CD68(+) pan-macrophage to CD163(+) M2 macrophage ratios, indicating relative increases in suppressive T cell and macrophage components, respectively.

CONCLUSIONS

Overall, BRAF(V600E) PTC tumors display a broadly immunosuppressive profile and evidence of disturbed host tumor immune surveillance that may contribute to the poorer outcomes observed in this subset of patients with thyroid cancer.