Upregulation of human leukocyte antigen–G expression and its clinical significance in ductal breast cancer

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.

Elevated sHLA-G plasma levels post chemotherapy combined with ILT-2 rs10416697C allele status of the sHLA-G-related receptor predict poorest disease outcome in early triple-negative breast cancer patients

Introduction

Triple negative breast cancer (TNBC) shows an aggressive growing and spreading behavior and has limited treatment options, often leading to inferior disease outcome. Therefore, surrogate markers are urgently needed to identify patients at high risk of recurrence and more importantly, to identify additional therapeutic targets enabling further treatment options. Based on the key role of the non-classical human leukocyte antigen G (HLA-G) and its related receptor immunoglobulin-like transcript receptor-2 (ILT-2) in immune evasion mechanisms of tumors, members of this ligand-receptor axis appear to be promising tool for both, defining risk groups and potential therapeutic targets.

Materials and methods

To follow this, sHLA-G levels before and after chemotherapy (CT), HLA-G 3' UTR haplotypes, and allele variations rs10416697 at the distal gene promoter region of ILT-2 were defined in healthy female controls and early TNBC patients. The results obtained were associated with clinical status, presence of circulating tumor cell (CTC) subtypes, and disease outcome of patients in terms of progression-free or overall survival.

Results

sHLA-G plasma levels were increased in TNBC patients post-CT compared to levels of patients pre-CT or controls. High post-CT sHLA-G levels were associated with the development of distant metastases, the presence of ERCC1 or PIK3CA-CTC subtypes post-CT, and poorer disease outcome in uni- or multivariate analysis. HLA-G 3' UTR genotypes did not influence disease outcome but ILT-2 rs10416697C allele was associated with AURKA-positive CTC and with adverse disease outcome by uni- and multivariate analysis. The prognostic value of the combined risk factors (high sHLA-G levels post-CT and ILT-2 rs10416697C allele carrier status) was an even better independent indicator for disease outcome in TNBC than the lymph nodal status pre-CT. This combination allowed the identification of patients with high risk of early progression/death with positive nodal status pre-CT or with non-pathological complete therapy response.

Conclusion

The results of this study highlight for the first time that the combination of high levels of sHLA-G post-CT with ILT-2 rs10416697C allele receptor status is a promising tool for the risk assessment of TNBC patients and support the concept to use HLA-G/ILT-2 ligand-receptor axis as therapeutic targets.

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.

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

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

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

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

HLA-G/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.

Peripheral blood immune markers in breast cancer: Differences in regulatory T cell abundance are related to clinical parameters

BACKGROUND

Cancer development is among other factors driven by tumor immune escape and tumor-mediated changes in the immune response. Investigating systemic immune changes may provide important knowledge for the improvement of patient prognosis and treatment opportunities.

METHODS

The systemic immune profile of patients with ER-positive breast cancer (n = 22) and healthy controls (n = 30) was investigated based on complete blood counts, flow cytometric analysis of T cell subsets including regulatory T cells (Tregs), and immune assays investigating soluble (s)HLA-G and the cytokine profile in plasma. We further examined the correlation between the immune markers and clinical parameters including tumor size, tumor grade and lymph node involvement.

RESULTS

Results indicated that breast cancer patients possessed a higher amount of neutrophils and monocytes and fewer lymphocytes and eosinophils compared with healthy controls. Breast cancer patients had significantly more CD25⁺CD127^low Tregs than controls, and both lymphocyte and Treg numbers were negatively correlated with tumor size. Furthermore, Treg numbers were elevated in grade I tumors compared with grade II tumors and with healthy controls. No difference in sHLA-G levels was observed between patients and controls. Higher levels of IL-6 and TNF-α were observed in breast cancer patients. Cytokine and sHLA-G levels were not associated with clinical parameters.

CONCLUSION

The results of this exploratory study contribute to the elucidation of the systemic immune response in breast cancer indicating a potential use of peripheral immune cell counts and Tregs to distinguish patients from healthy controls and as potential diagnostic and prognostic biomarkers to be investigated in future studies.

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.

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

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

The Role of HLA-G in Tumor Escape: Manipulating the Phenotype and Function of Immune Cells

Human leukocyte antigen-G (HLA-G) is a non-classical major histocompatibility complex class I (MHC I) molecule, and under physiological conditions, its expression is strictly restricted to the maternal–fetal interface and immune-privileged organs where HLA-G is expected to contribute to establishment and maintenance of immune tolerance. However, the expression of HLA-G has been found in various types of tumors, and the level of its expression frequently correlates with high-grade histology and poor prognosis, raising the possibility that it may play a negative role in tumor immunity. ILT2 and ILT4, present on a broad of immune cells, have been identified as the main receptors engaging HLA-G, and their interactions have been found to allow the conversion of effectors like NK cells and T cells to anergic or unresponsive state, activated DCs to tolerogenic state, and to drive the differentiation of T cells toward suppressive phenotype. Therefore, tumors can employ HLA-G to modulate the phenotype and function of immune cells, allowing them to escape immune attack. In this review, we discuss the mechanism underlying HLA-G expression and function, its role played in each step of the tumor-immunity cycle, as well as the potential to target it for therapeutic benefit.

Intratumor Heterogeneity of HLA-G Expression in Cancer Lesions

Signaling pathway between human leukocyte antigen (HLA)-G and immune inhibitory receptors immunoglobulin-like transcript (ILT)-2/4 has been acknowledged as one of immune checkpoints, and as a potential target for cancer immunotherapy. Like other immune checkpoints, inter- and even intratumor heterogeneity of HLA-G could render a rather complexity for HLA-G-target immunotherapy. However, little information for intratumor heterogeneity of HLA-G is available. In this study, HLA-G expression in a serial section of colorectal cancer (CRC) lesions from three CRC patients (each sample with serial section of 50 slides, 10 randomized slides for each antibody), three different locations within a same sample (five CRC), and three case-matched blocks that each includes 36 esophageal cancer samples, were evaluated with immunohistochemistry using anti-HLA-G antibodies (mAbs 4H84, MEM-G/1 and MEM-G/2 probing for all denatured HLA-G isoforms, 5A6G7, and 2A12 probing for denatured HLA-G5 and HLA-G6 isoforms). Our results revealed that, in addition to the frequently observed inter-tumor heterogeneity, intratumor heterogeneous expression of HLA-G is common in different areas within a tumor in CRC and esophageal cancer samples included in this study. Moreover, percentage of HLA-G expression probed with different anti-HLA-G antibodies also varies dramatically within a tumor. Given HLA-G has been considered as an important immune checkpoint, intratumor heterogeneity of HLA-G expression, and different specificity of anti-HLA-G antibodies being used among studies, interpretation and clinical significance of HLA-G expression in cancers should be with caution.

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.

Expression analysis of immune-regulatory molecules HLA-G, HLA-E and IDO in endometrial cancer

HLA-G has been widely implicated in advanced cancers through different pathways of immunosuppression allowing tumor escape. Contrarily, HLA-E has a controversial role in the tumor escape from the immune system. IDO catabolic enzyme is known to be up-regulated in many tumors types allowing their immune escape. Based on these considerations, we investigated the expression of HLA-G, HLA-E and IDO molecules in endometrial cancer (EC) and their association with prognostic clinicopathologic parameters. Their expression were checked in tumoral and adjacent endometrial tissues. Both HLA-G and IDO immunostaining were significantly increased in EC tissues compared to normal residual endometrial glands (Mann Whitney U-test, p = 0.0001 and p = 0,020 respectively). However, HLA-E was highly expressed in tumoral tissues as well as in normal residual endometrial glands (respectively, 100% and 81.8%). Increased HLA-G expression levels were observed in high histological grade (grade 3), and in the non-endometrioid type 2 EC. Unexpectedly, patients with IDO Low expression had significantly impaired overall survival compared to patients with IDO High (log-rank p = 0.021). Conversely, HLA-E low expression was associated to an improved overall survival EC (log-rank p = 0.004). We concluded that, HLA-G and IDO are highly expressed in EC compared to adjacent normal endometrial tissues, that might be interesting for the EC outcome.

Serum sHLA-G: Significant diagnostic biomarker with respect to therapy and immunosuppressive mediators in Head and Neck Squamous Cell Carcinoma

Head & Neck Squamous Cell Carcinoma is one of the highest mortality factors in the world due to the lack of potential biomarker for early detection of disease. There is an urgent need for molecular marker involved in disease progression which remains suppressed normally, required for specificity. HLA-G is highly expressed in cancers and creates immune-suppressive microenvironment. Cancerous cells secrete inflammatory cytokines like IL-10,IFN-γ which increase expression of immunosuppressive molecules, such as HLA-G. We evaluated sHLA-G protein level in serum of 120 HNSCC patients at diagnosis and after therapy and compared with 99 individuals by SPR, ELISA and determined its mRNA level by qRT-PCR. sHLA-G was correlated with serum IL-10 and IFN-γ of the patients. Significant elevated levels of sHLA-G were observed in patients (8.25 ± 1.74 ng/µl) than control (6.45 ± 1.31 ng/µl). Levels were declined in (8.09 ± 1.79 ng/µl to 6.64 ± 1.33 ng/µl) patients in response to therapy. sHLA-G levels with tumor burden (8.16 ± 1.91 to 6.63 ± 1.32 ng/µl), node (8.62 ± 1.45 to 6.66 ± 1.26 ng/µl), PDSCC (8.14 ± 0.62 to 5.65 ± 0.27 ng/µl) and oropharynx (7.90 ± 1.24 to 6.10 ± 1.33 ng/µl) showed a positive and significant response to therapy. Findings indicate that sHLA-G can be a potential diagnostic serum protein marker for HNSCC due to its suppressive function and over expression in diseased condition with the influence of cytokines.

Killer Immunoglobulin-Like Receptor 2DL4 (CD158d) Regulates Human Mast Cells both Positively and Negatively: Possible Roles in Pregnancy and Cancer Metastasis

Killer immunoglobulin-like receptor (KIR) 2DL4 (CD158d) was previously thought to be a human NK cell-specific protein. Mast cells are involved in allergic reactions via their KIT-mediated and FcɛRI-mediated responses. We recently detected the expression of KIR2DL4 in human cultured mast cells established from peripheral blood of healthy volunteers (PB-mast), in the human mast cell line LAD2, and in human tissue mast cells. Agonistic antibodies against KIR2DL4 negatively regulate the KIT-mediated and FcɛRI-mediated responses of PB-mast and LAD2 cells. In addition, agonistic antibodies and human leukocyte antigen (HLA)-G, a natural ligand for KIR2DL4, induce the secretion of leukemia inhibitory factor and serine proteases from human mast cells, which have been implicated in pregnancy establishment and cancer metastasis. Therefore, KIR2DL4 stimulation with agonistic antibodies and recombinant HLA-G protein may enhance both processes, in addition to suppressing mast-cell-mediated allergic reactions.

Regulatory T cells in breast cancer as a potent anti-cancer therapeutic target

Despite marked advances in treatment approaches, breast cancer is still going to be more prevalent, worldwide. High levels of regulatory T (Treg) cells have repeatedly been demonstrated in circulation, lymph nodes, and tumor samples from patients with various cancer types. The transcription factor Forkhead box protein 3 (Foxp3)-expressing Treg cells have the high suppressive potential of the immune system and are fundamental in preserving immune homeostasis and self-tolerance. However, they enhance tumor development by curbing efficient anti-tumor immune mechanisms in malignancies. Moreover, the accumulation of Treg cells in breast tumors is related to the short overall survival of patients. Treg cell frequency has been applied as an independent predicting factor to diagnose patients with a high risk of relapse. Pulling out all populations of Treg cells to promote the efficacy of anticancer treatment methods may potentially lead to hazardous autoimmune disorders. Thus, realizing the exact structure of tumor-infiltrating Treg cells is pivotal to efficiently target Treg cells in tumors. There are exclusive and non-exclusive approaches to lower down and degrade the number/function of Treg cells. These approaches can include inhibiting tumoral migration, depletion, interference with function, and utilizing T cell plasticity. This review article attempts to clarify the implications concerning the involvement of Treg cells in breast cancer progression and discuss the current approaches in the treatment of this cancer via modulation of Treg cells function.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Implication of Soluble HLA-G and HLA-G +3142G/C Polymorphism in Breast Cancer Patients Receiving Adjuvant Therapy in Tanzania

BACKGROUND

During cancer growth, immunosuppressive microenvironment is created that enables tumour cells to evade an eliminative immune response and hence manage to grow into malignancy. HLA-G, existing as either membrane-bound (mHLA-G) or soluble (sHLA-G) molecule is thought to be immunosuppressive and produced more by tumor cells. The +3142G/C polymorphism in HLA-G gene affects its expression, and G allele is considered to be a protective mutant allele associated with less expression of HLA-G. The implication of HLA-G in cancer development has been reported in different cancers and populations. But, its implication in most African populations has not yet been investigated. The aim of this study was to determine the possible associations of soluble HLA-G and HLA-G +3142G/C SNP with breast cancer.

MATERIALS AND METHODS

75 breast cancer patients and 84 normal controls were recruited in this study. The genotyping of HLA-G +3142G/C polymorphism was determined by LightSNiP typing assay using quantitative Real-Time PCR and sHLA-G levels were determined by ELISA.

RESULTS

The sHLA-G levels were significantly lower in breast cancer patients than in controls (p<0.001). Also, they were significantly lower in mastectomized patients compared to non-mastectomized patients (p=0.018). The ROC analysis revealed a significant ability of sHLA-G to differentiate breast cancer patients versus normal controls (AUC=0.697, 95% CI= 0.619-0.767, p<0.001) and identify mastectomized patients (AUC=0.667, 95% CI= 0.549 to 0.772, p=0.041). The assessment of +3142G/C polymorphism revealed a relatively similar distribution of frequencies of genotypes and alleles between breast cancer patients and normal controls (p>0.05) and was neither associated with sHLA-G levels.

CONCLUSION

While the +3142G/C SNP was found not to be relevant to breast cancer, the changes of sHLA-G levels in response to medical interventions such as mastectomy may be translated into its potential prognostic utility for breast cancer. More studies are needed to provide clear evidence of sHLA-G as a diagnostic and prognostic marker of breast cancer in Tanzania.
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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.

HLA-G Gene Polymorphism in Egyptian Patients with Non-Hodgkin Lymphoma and its Clinical Outcome

BACKGROUND

Non-Hodgkin lymphoma (NHL) is a major cancer in Egypt and worldwide and has many risk factors including genes involved in the immune response.

AIM

we investigated the HLA-G 14bp gene polymorphism as a risk factor for NHL and its clinic pathologic features. The study involved 150 patients with NHL and 100 healthy control. Full histories, clinical examination, C.T scan and laboratory investigations such as CBC, LDH, ?2microglobulin and HCV RNA by qualitative real time PCR were performed for all subjects. HLA-G 14bp ins/del gene polymorphism was determined by PCR.

RESULTS

in our study, del/del, ins/del and dominant genotypes increased the risk of NHL by 11.01, 10.55 and 10.88 fold respectively (p<0.001) but the recessive genotype did not increase the risk of NHL (p=0.112). Cases with the del allele had a greater risk of NHL than those with the ins allele (p<0.001). del/del and ins/del genotypes were significantly associated with higher LDH and ?2microglobulin levels (p<0.001), lower Hb and platelet values (p<0.001), extra nodal sites (p=0.001), poor performance status (p=0.04) and relapse (p=0.001).  Conclusions:  the results suggest that HLA-G 14bp ins/del gene polymorphism is a risk factor for NHL in our Egyptian population and is associated with poor clinical pathological features.

ABBREVIATIONS

Non-Hodgkin lymphoma (NHL), Diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), Epstein-Barr virus (EBV), human T-cell lymphotropic/leukemia virus-1 (HTLV-1).

Evaluation of ascitic soluble human leukocyte antigen-G for distinguishing malignant ascites from benign ascites

The overexpression of soluble human leukocyte antigen-G is associated with malignant tumours. The purpose of our study was to detect soluble human leukocyte antigen-G concentrations in ascites and to evaluate the value of ascitic soluble human leukocyte antigen-G for the diagnosis of malignant ascites. Enzyme-linked immunosorbent assay was used to detect soluble human leukocyte antigen-G levels in 64 patients with malignant ascites and 30 patients with benign ascites. Receiver operating characteristic curves were used to evaluate the diagnostic efficacy of ascitic soluble human leukocyte antigen-G for the detection of malignant ascites. Ascitic soluble human leukocyte antigen-G levels were significantly higher in the malignant ascites group than in the benign ascites group (20.718 ± 3.215 versus 12.467 ± 3.678 µg/L, t = 7.425, p < 0.001). The area under the receiver operating characteristic curve for ascitic soluble human leukocyte antigen-G was 0.957 (95% confidence interval, 0.872-0.992). At a cut-off value of 19.60 µg/L, the sensitivity and specificity of ascitic soluble human leukocyte antigen-G were 87.5% (95% confidence interval, 71.0%-96.5%) and 100% (95% confidence interval, 88.4%-100%), respectively. With respect to area under the receiver operating characteristic curve, sensitivity and specificity, ascitic carcinoembryonic antigen (0.810, 68.75% and 83.33%, respectively) and carbohydrate antigen 19-9 (0.710, 65.63% and 70%, respectively) significantly differed (all p < 0.05). In malignant ascites that were cytology-negative and biopsy-positive, the rate of positivity for ascitic soluble human leukocyte antigen-G was 75%, which was higher than the corresponding rates for ascitic carcinoembryonic antigen (31.25%) and carbohydrate antigen 19-9 (6.25%; both p < 0.05). In conclusion, The detection of ascitic soluble human leukocyte antigen-G exhibited good performance for diagnosing malignant ascites, and particularly those that were cytology-negative and biopsy-positive.

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.

Evaluation of HLA-G, HLA-E, and PD-L1 proteins in oral osteosarcomas

OBJECTIVE

The aim of this study was to investigate the expression of human leukocyte antigens (HLAs) G and E and programmed death-ligand 1 (PD-L1) in oral osteosarcoma (OO) (n = 13). The relationship between the expression of these molecules and histologic grading and metastasis was also evaluated.

STUDY DESIGN

HLA-G, HLA-E, and PD-L1 were identified by immunohistochemistry. Samples of normal bone tissue (n = 6) were used as controls. The sections were evaluated using a semiquantitative scoring system with an immunoreactive score, where a score of 0 was considered absent, ≤2 was low, and >2 was high expression.

RESULTS

We identified high expression of HLA-G, HLA-E, and PD-L1 by malignant osteoblastic cells in 69.2% of OO cases, which was statistically higher than that in controls (P < .05). Overexpression of these proteins was identified in 8 of 11 samples of high-grade and 1 of 2 samples of low-grade OO. Additionally, 66.6% of patients with metastases (n = 4) and 71.4% of patients without metastases (n = 5) had high expression of HLA-G, HLA-E, and PD-L1 in tumor samples (P > .05).

CONCLUSION

OO had high expression of HLA-G, HLA-E, and PD-L1 irrespective of clinicopathologic parameters, including histologic grading and metastasis.

Pregnancy and breastfeeding: a new theory for sHLA-G in breast cancer patients?

It is now widely recognized that HLA-G molecule is implicated in immune tolerance and particularly in immune subversion of tumor cells. In this study, we explored levels of soluble HLA-G (sHLA-G) in plasma samples obtained from women with breast cancer (BC). Additionally, we correlated sHLA-G concentration with pregnancy and breastfeeding history. We reported in this preliminary work significant differences in sHLA-G levels between BC patients with/without breastfeeding experience (p = 0.04). Interestingly, among women with BC, only those without previous pregnancy experience present significant increase in sHLA-G (p = 0.02). Of relevance, we demonstrated that patients without both pregnancy and breastfeeding history have advanced SBR III grade, associated with significant enhancement in tumor size compared with patients who had both experiences (p = 0.028). Taken together, our results indicate the potential implication of previous pregnancy and breastfeeding experience in sHLA-G expression during BC. We theorized that having pregnancy and breastfeeding history may protect against advanced BC stages.

The Pathophysiological Impact of HLA Class Ia and HLA-G Expression and Regulatory T Cells in Malignant Melanoma: A Review

Malignant melanoma, a very common type of cancer, is a rapidly growing cancer of the skin with an increase in incidence among the Caucasian population. The disease is seen through all age groups and is very common in the younger age groups. Several studies have examined the risk factors and pathophysiological mechanisms of malignant melanoma, which have enlightened our understanding of the development of the disease, but we have still to fully understand the complex immunological interactions. The examination of the interaction between the human leucocyte antigen (HLA) system and prognostic outcome has shown interesting results, and a correlation between the down- or upregulation of these antigens and prognosis has been seen through many different types of cancer. In malignant melanoma, HLA class Ia has been seen to influence the effects of pharmaceutical drug treatment as well as the overall prognosis, and the HLA class Ib and regulatory T cells have been correlated with tumor progression. Although there is still no standardized immunological treatment worldwide, the interaction between the human leucocyte antigen (HLA) system and tumor progression seems to be a promising focus in the way of optimizing the treatment of malignant melanoma.

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.

Elevation of HLA-G-expressing DC-10 cells in patients with gastric cancer

DC-10 is a distinct subset of human tolerogenic dendritic cells (DCs) which express high levels of human leukocyte antigen-G (HLA-G). DC-10 could induce adaptive type 1 regulatory T cells through the IL-10 dependent ILT4/HLA-G signaling pathway. However, the significance of DC-10 in malignancies remains unclear. In this study, the frequency and mean fluorescence intensity (MFI) of HLA-G+ DC-10 in the peripheral blood of 124 patients with gastric cancer (GC) and 130 normal controls was analyzed with flow cytometry. Plasma sHLA-G was analyzed with ELISA. Results showed both the percentages of peripheral HLA-G+ DC-10 (median: 0.13% vs 0.01%; p<0.01) and MFI of HLA-G on these cells (median: 310.0 vs 91.5; p<0.01) were dramatically increased in GC patients than in normal controls. The frequency of HLA-G+ DC-10 in GC patients was strongly relative to the tumor grade (p=0.021). sHLA-G levels in GC patients were significantly higher than in healthy controls (median: 85.80U/ml vs 61.20U/ml; p<0.01). There was no significant correlation between the percentage of DC-10 and plasma sHLA-G (p>0.05). However, the increased HLA-G+ DC-10, HLA-G MFI and plasma sHLA-G in patients with gastric cancer could be a diagnostic factor with the area under the ROC curve with 0.947 (p<0.01), 0.882 (p<0.01) and 0.700 (p<0.01) respectively. Given the immune tolerant function of DC-10 could play, the increased DC-10 might play an important role in immune suppression for patients with gastric cancer, while more studies are necessary to illustrate the clinical relevance of DC-10 in cancer patients.

Association of HLA-G*01:01:02:01/G*01:04:01 polymorphism with gastric adenocarcinoma

Human leukocyte antigen-G (HLA-G) plays an important role in tumor cell escape from immune surveillance and HLA-G polymorphisms might service as a potential risk factor for clinical outcomes in GAC (gastric adenocarcinoma). We investigated the association between HLA-G polymorphisms as well as soluble HLA-G level and accordance of GAC. This case-control study included 100 GAC patients and 102 unrelated Iranian individual's samples as control. The clinical stages ranged from I to IV. PCR-RFLP method was carried out in order to specify the genotypes of the HLA-G gene. Concentrations of sHLA-G in serum were determined with the sHLA-G-specific enzyme linked immunosorbent assay (ELISA) kit. The G*01:04:01 and G*01:01:02:01 alleles were the predominant alleles in GAC patients and healthy controls. The G*01:01:03:01 and G*01:01:08 allele distributions are significantly higher among controls comparing to cases and seem to have protective effect (P value=0.026 and 0.007 respectively). There is a substantial differences in G*01:01:02:01/G*01:04:01 genotype frequencies between cases and controls (OR=2.8, P value<0.001). The G*01:01:03:01/G*01:04:01 and G*01:01:02:01/G*01:01:08 genotypes frequency are higher among controls in comparison to patients (P value=0.028 and 0.007 respectively). The polymorphisms in HLA-G could affect GAC induction and its outcome. Also, increased sHLA-G levels in serum might be a useful biomarker for diagnosis.

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.

Significance of tumour cell HLA-G5/-G6 isoform expression in discrimination for adenocarcinoma from squamous cell carcinoma in lung cancer patients

Human leucocyte antigen (HLA)-G has seven isoforms, of which HLA-G1-G4 are membrane-bound and HLA-G5-G7 are soluble. Previous studies reinforced HLA-G expression was strongly related to poor prognosis in different types of cancers. Among these studies, the monoclonal antibody (mAb) 4H84 was used which detects all HLA-G isoform heavy chain; unfortunately, leaves the specific types of isoforms expressed in lesions undistinguished and its clinical significance needs to be clarified. To explore clinical significance of lesion soluble HLA-G (sHLA-G) in non-small-cell lung cancer (NSCLC), mAb 5A6G7 recognizing HLA-G5/-G6 molecules was used. Tumour cell sHLA-G expression in 131 primary NSCLC lesions (66 squamous cell carcinoma, 55 adenocarcinoma and 10 adenosquamous carcinoma) were analysed with immunohistochemistry. Data showed that sHLA-G expression was observed in 34.0% (45/131) of the NSCLC lesions, which was unrelated to patient age, sex, lymph nodal status, tumour-node-metastasis stage and patient survival. However, tumour cell sHLA-G expression in lesions was predominately observed in adenocarcinoma lesions (73.0%, 40/55) which was significantly higher than that in squamous cell carcinoma (6.0%, 4/66) and adenosquamous carcinoma lesions (10.0%, 1/10, P < 0.001). The area under the receiver operating characteristic curve for lesion sHLA-G was 0.833 (95% CI: 0.754-0.912, P < 0.001) for adenocarcinoma versus squamous cell carcinoma. Our findings for the first time showed that tumour cell sHLA-G was predominately expressed in lung adenocarcinoma, which could be a useful biomarker to discriminate adenocarcinoma from squamous cell carcinoma in NSCLC patients.

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.

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.

Human leukocyte antigen-G (HLA-G) polymorphism and expression in breast cancer patients

Human leukocyte antigen-G (HLA-G) is known to be implicated in a tumor-driven immune escape mechanism in malignancies. The purpose of this study was to investigate HLA-G polymorphism and expression in breast cancer. HLA-G alleles were determined by direct DNA sequencing procedures from blood samples of 80 breast cancer patients and 80 healthy controls. Soluble HLA-G (sHLA-G) was measured by enzyme-linked immunosorbent assay (ELISA) from serum specimens. HLA-G expression in breast cancer lesions was also analyzed by immunohistochemistry staining. The presence of HLA-G 3' untranslated region (UTR) 14-bp sequence was analyzed and found to be associated with reduced risk of breast cancer susceptibility based on HLA-G expression in tissues (P = 0.0407). Levels of sHLA-G were higher in the breast cancer group (median 117.2 U/mL) compared to the control group (median 10.1 U/mL, P<0.001). The area under the receiver operating characteristic curve (AU-ROC) values of sHLA-G for differentiating breast cancer from normal controls and for detecting metastasis from other stages of breast cancer were 0.89 and 0.79, respectively. HLA-G polymorphism and expression may be involved in breast carcinogenesis and sHLA-G concentrations could be used as a diagnostic marker for detecting breast cancer.

Human leukocyte antigen G is associated with esophageal squamous cell carcinoma progression and poor prognosis

Human leukocyte antigen G (HLA-G) is a non-classical HLA class I molecule thought to play a key role in maternal-fetal tolerance and cancer immune evasion. This study aimed to investigate the HLA-G expression in lesion sections and plasma sHLA-G levels of primary esophageal squamous cell carcinoma (ESCC) patients and its clinical significance in diagnosis and prognosis of ESCC. 60 ESCC patients and 28 healthy controls were recruited, and the positive expression of HLA-G in ESCC lesions and adjacent normal tissues were 70% (42/60) and 8.6% (5/60) (P<0.05), respectively, while no expression was found in normal controls. HLA-G1 and HLA-G5 were determined to be dominating isoforms measured by RT-PCR. There was a significant difference in plasma sHLA-G levels between patients with ESCC (15.04 U/ml, range 4.33-250.00 U/ml) and healthy controls (6.81 U/ml, range 0-29.27 U/ml) (P<0.01). The plasma IL-10 level was higher in ESCC patients than the controls (23.86 pg/ml vs. 12.81 pg/ml, P<0.01). HLA-G expression in lesion tissues was correlated with cancer cell differentiation (P=0.033), lymph node metastasis (P=0.035) of ESCC. However, no obvious correlations were demonstrated between the plasma sHLA-G levels and the clinicopathological parameters. There was a significant correlation between sHLA-G and IL-10 expression (r=0.353, P=0.006) in patients with Esophageal squamous cell carcinoma. HLA-G positive expression showed poorer prognosis of ESCC. HLA-G positive expression might serve as a potential marker in the diagnosis or prediction of ESCC.

Pregnancy-associated miRNA-clusters

MicroRNAs (miRNAs) are expressed in the placenta and can be detected in maternal plasma. An increasing number of studies have been published on the cellular origin, distribution and function of miRNAs in pregnancy. Specific miRNA profiles have been described for the placenta, maternal plasma and several pregnancy disorders. It has been observed that numerous miRNAs, which are predominantly or exclusively expressed during pregnancy, are clustered in chromosomal regions, may be controlled by the same promoters, may have similar seed regions and targets, and work synergistically. The three most eminent clusters are the chromosome 19 miRNA cluster (C19MC), C14MC and miR-371-3 cluster, which is also localized on chromosome 19. MiRNA members of these clusters are not only detected in the placenta, but also in other compartments, e.g. in serum where they have the potential to become novel biomarkers of pregnancy disorders. Additionally, some members are also expressed in a variety of tumors. Antagonism of selected miRNAs or their targets may lead to novel strategies for the development of new drug classes in pregnancy disorders or other diseases. This review summarizes current knowledge on the pregnancy-related miRNA clusters - the C19MC, C14MC and miR-371-3 cluster - in regard to pregnancy and also other, mostly pathological circumstances.

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.

Further evidence for the existence of major susceptibility of nasopharyngeal carcinoma in the region near HLA-A locus in Southern Chinese

Background

Nasopharyngeal carcinoma (NPC) is a multi-factorial malignancy closely associated with environmental factors, genetic factors and Epstein-Barr virus infection. Human leukocyte antigen (HLA) complex, specially the region near HLA-A locus, was regarded as a major candidate region bearing NPC genetic susceptibility loci in many previous studies including two recent genome-wide association (GWA) studies. To provide further evidence for the NPC susceptibility in the region near HLA-A locus based on other previous studies, we carried out a two-stage hospital-based case control association study including 535 sporadic NPC patients and 525 cancer-free control subjects from Guangdong, a high prevalence area of NPC in China.

Methods

38 tag SNPs were initially selected by Heploview from the segment around HLA-A locus (from D6S211 to D6S510) and genotyped on GenomeLab SNPstream platform in 206 cases and 180 controls in the stage 1. Subsequently, the stage 1 significant SNPs and 17 additional SNPs were examined on another platform (Sequenom iPlex Assay) in another independent set of study population including 329 cases and 345 controls.

Results

Totally eight SNPs from the segment from D6S211 to D6S510 within HLA complex were found to be significantly associated with NPC. Two of the most significant SNPs (rs9260734 and rs2517716) located near to HLA-A and HCG9 respectively were in strong LD with some other SNPs of this region reported by two previous GWA studies. Meanwhile, Meanwhile, novel independent susceptibility loci (rs9404952, Pcombined = 6.6 × 10^-5, OR combined = 1.45) was found to be close to HLA-G.

Conclusion

Therefore, our present study supports that the segment from D6S211 to D6S510 in HLA complex region might contain NPC susceptibility loci which indeed needs to be fully investigated in the future.

Altered HLA class I and HLA-G expression is associated with IL-10 expression in patients with cervical cancer

Although high-risk human papillomaviruses (HPVs) are an important risk factor in the etiopathogenesis of cervical cancer, increasing evidence suggests that the ability to avoid immune surveillance seems to be linked to the transforming potential of HPV and a rapid progression to cancer. In other cancer models, IL-10 contributes to impair anti-tumor immune response either by downregulating human leukocyte antigen Class I (HLA-I) expression or by increasing HLA-G expression. To comprehend how these alterations could contribute to evasion of immune surveillance in cervical cancer, we analyzed HLA-I, HLA-G and IL-10 expressions by immunohistochemistry in 63 biopsies from patients with cervical intraepithelial neoplasia III (CIN-III) and cervical cancer. Immunohistochemistry showed absent or weak HLA-I expression in 50/59 cases. In these cases, a high percentage had loss of heterozygosis. IL-10 and HLA-G expression were observed in 46.6 and 27.6% of cases, respectively. Concurrent upregulation of IL-10 was found in 87.5% of HLA-G positive cases (p = 0.000). Similarly, a significant association between IL-10 expression and HLA-I downregulation was found (p = 0.028). Finally, we observed higher HLA-G expression in patients with HLA-I downregulation than in those with normal HLA-I expression (p = 0.004). Our results suggest that, in cervical cancer, the IL-10 expression may induce an immunosuppressive environment by upregulating HLA-G expression and downregulating HLA class I expression.

Relationship between HLA-G gene polymorphism and the susceptibility of esophageal cancer in Kazakh and Han nationality in Xinjiang

OBJECTIVE

To explore the association between polymorphism of the human leukocyte antigen G (HLA-G) and susceptibility of esophageal carcinoma (EC) in Kazakh and Han nationality in Xinjiang.

METHODS

The 14 bp deletion/insertion (rs16375) and 0105N (rs41557518) of HLA-G genotyping were determined by PCR and PCR-RFLP, respectively in 239 patients and 467 controls.

RESULTS

There was a 2.69-fold (P(c) = 0.04, 95% CI: 1.30-5.55) increased risk of developing EC in individuals with the -14 bp/-14 bp genotype (rs16375) compared with those carrying +14 bp/+14 bp genotype in Kazakh after Bonferroni correction, there was no association of 0105N (rs41557518) both in Kazak and Han population. And there was a 2.82-fold (P(c) = 0.04, 95% CI: 1.32-6.04) increased risk of developing EC in individuals with -14 bp/-14 bp and C/C genotypes compared with those who had +14 bp/+14 bp and C/C genotypes in Kazakh.

CONCLUSIONS

The study demonstrates that EC is associated with polymorphism of HLA-G14 bp in Chinese Kazak population. The 14 bp deletion/insertion of HLA-G gene may play a role in EC susceptibility of Kazakh.

Human leukocyte antigen-G in cancer: are they clinically relevant?

The immunotolerant human leukocyte antigen (HLA)-G has direct inhibitory effects on natural killer cells (NK), dendritic cells (DC), T cells and can induce tolerant regulatory cells. The expression of HLA-G has been correlated with the tolerance of the fetus, the acceptance of organ transplants, and the immune escape of tumor cells and virus-infected cells. In the context of malignancies, aberrant induction of HLA-G expression has been extensively investigated and its clinical relevance has been postulated. We here focus on the HLA-G expression in malignancies and its relevance to tumor cell immune escaping and disease progression.