Non-classical HLA-G antigen and its role in the cancer progression

HLA-G expression in Merkel cell carcinoma and the correlation with Merkel cell polyomavirus infection

Merkel cell carcinoma (MCC) is a rare aggressive neuroendocrine cutaneous carcinoma with a high mortality rate. The MCC etiology is not fully understood. Merkel cell-associated polyomavirus (MCPyV) was found in MCC patients, indicating a risk factor for the tumor. Caucasian, elderly, and immunocompromised individuals are more likely to develop this tumor. HLA-G consists of a non-classical class I (Ib) HLA molecule with an immunoregulatory function and was associated with tumor escape in different types of tumors, nonetheless, never been studied in MCC. The purpose of this study was to evaluate the HLA-G expression and also to detect the MCPyV in MCC patients and correlate it with the clinical course of the disease. Forty-five MCC patients were included in a retrospective study. Formalin-fixed paraffin-embedded cutaneous skin biopsies were used by immunohistochemistry and RT-PCR to verify the HLA-G expression and MCPyV infection. HLA-G expression was found in 7 (15.6%), while the presence of MCPyV was detected in 28 (62.2%) of the studied patients. No significant association was found between HLA-G expression and MCPyV infection (p = 0.250). The presence of MCPyV was associated with areas of low sunlight exposure (p = 0.042) and the HLA-G expression with progression to death (p = 0.038). HLA-G expression was detected in MCC patients, as well as the MCPyV presence was confirmed. These markers could represent factors with a possible impact on patient survival; however, further studies with a greater number of patients are needed, to better elucidate the possible role in disease progression.

Natural killer cell-based strategies for immunotherapy of cancer

Natural killer (NK) cells are a family of lymphocytes with a natural ability to kill infected, harmed, or malignantly transformed cells. As these cells are part of the innate immunity, the cytotoxic mechanisms are activated upon recognizing specific patterns without prior antigen sensitization. This recognition is crucial for NK cell function in the maintenance of homeostasis and immunosurveillance. NK cells not only act directly toward malignant cells but also participate in the complex immune response by producing cytokines or cross-talk with other immune cells. Cancer may be seen as a break of all immune defenses when malignant cells escape the immunity and invade surrounding tissues creating a microenvironment supporting tumor progression. This process may be reverted by intervening immune response with immunotherapy, which may restore immune recognition. NK cells are important effector cells for immunotherapy. They may be used for adoptive cell transfer, genetically modified with chimeric antigen receptors, or triggered with appropriate antibodies and other antibody-fragment-based recombinant therapeutic proteins tailored specifically for NK cell engagement. NK cell receptors, responsible for target recognition and activation of cytotoxic response, could also be targeted in immunotherapy, for example, by various bi-, tri-, or multi-specific fusion proteins designed to bridge the gap between tumor markers present on target cells and activation receptors expressed on NK cells. However, this kind of immunoactive therapeutics may be developed only with a deep functional and structural knowledge of NK cell receptor: ligand interactions. This review describes the recent developments in the fascinating protein-engineering field of NK cell immunotherapeutics.

HLA-G, cytokines, and cytokine receptors in the non-aggressive basal cell carcinoma microenvironment

Non-aggressive basal cell carcinoma (BCC) growth is slow and might be mediated by the immune system. This study analysed the human leukocyte antigen (HLA)-G expression and cytokine profile in non-aggressive BCC subtypes from distinct locations. HLA-G was evaluated via immunohistochemistry and cytokine expression was analysed by a quantitative real-time polymerase chain reaction in 26 primary BCC samples, including nodular BCC (nBCC, n = 16) and superficial BCC (n = 10) from cephalic (ceBCC, n = 12) and non-cephalic (n = 14) locations, and by bioinformatics analysis of public GEO databases. Inflammatory infiltrate was concentrated around the tumour nests. HLA-G-positive inflammatory cells (53.85%) were more abundant than HLA-G-positive tumour cells (21.54%, p < 0.001). HLA-G immunoreactivity was predominantly cytoplasmic in BCC cells and was primarily associated with lymphocytes and macrophages surrounding the tumour. nBCC showed a higher percentage of HLA-G-positive tumour cells (p = 0.04), and ceBCC showed stronger intensity (p = 0.04). IFN-gamma and IL-10 expression were 1.95 and 1.22-fold higher, respectively, relative to that in normal skin, with a positive correlation between them (r = 0.61; p = 0.002). IL-23 expression was higher in nBCC (p = 0.04) and positively correlated (r = 0.47; p = 0.05) with slight intensity of HLA-G-positive tumour cells. The up-regulation of IL23A and IL10RB and down-regulation of IFNGR1 and IL4R gene expression in BCC compared to levels in adjacent tissues were demonstrated in the GSE125285 dataset. The exhibited cytokine profile was consistent with the induction of HLA-G expression in non-aggressive BCC subtypes. HLA-G expression in tumour cells and inflammatory cells surrounding BCCs supports the generation of inhibitory signals on various immune cells that exert anti-tumour responses.

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.

Genetic and molecular biology of breast cancer among Iranian patients

Abstract

Background, Breast cancer (BC) is one of the leading causes of cancer related deaths in Iran. This high ratio of mortality had a rising trend during the recent years which is probably associated with late diagnosis.

Main body

Therefore it is critical to define a unique panel of genetic markers for the early detection among our population. In present review we summarized all of the reported significant genetic markers among Iranian BC patients for the first time, which are categorized based on their cellular functions.

Conclusions

This review paves the way of introducing a unique ethnic specific panel of diagnostic markers among Iranian BC patients. Indeed, this review can also clarify the genetic and molecular bases of BC progression among Iranians.

miR‑148a modulates the viability, migration and invasion of oral squamous cell carcinoma cells by regulating HLA‑G expression

Oral squamous cell carcinoma (OSCC) is a common malignancy of the oral and maxillofacial regions. MicroRNAs (miRs) are a group of endogenous small noncoding RNAs that inhibit gene expression by binding to the mRNA of target genes, and serve important roles in numerous biological processes. Reverse transcription-quantitative polymerase chain reaction and western blotting were used to detect gene and protein expression levels, respectively. Cell proliferation, migration and invasion were detected using MTT, wound healing and Matrigel assays, respectively. The association between miR-148a and human leukocyte antigen-G (HLA-G) was analyzed using Targetscan and Luciferase reporter assays. In the present study, miR-148a was revealed to be significantly downregulated in OSCC cells. To further investigate the functions of miR-148a in OSCC, the viability, migration, and invasive abilities of SCC-9 cells were investigated following transfection with miR-148a mimics or miR-148a inhibitor. It was revealed that transfection with miR-148a mimics significantly reduced the viability, migration and invasion of cells, whereas miR-148a inhibitor significantly enhanced these properties. In addition, HLA-G was identified as a direct target of miR-148a and demonstrated to be downregulated in OSCC cells. Furthermore, it was revealed that transfection with miR-148a mimics decreased the expression levels of HLA-G mRNA and protein in SCC-9 cells, whereas transfection with miR-148a inhibitor increased the expression of HLA-G mRNA and protein. The results indicated that there was an association between miR-148a and HLA-G expression, and suggested that miR-148a may be a potential target in the treatment of OSCC.

Oncolytic virus immunotherapy: future prospects for oncology

BACKGROUND

Immunotherapy is at the forefront of modern oncologic care. Various novel therapies have targeted all three layers of tumor biology: tumor, niche, and immune system with a range of promising results. One emerging class in both primary and salvage therapy is oncolytic viruses. This therapy offers a multimodal approach to specifically and effectively target and destroy malignant cells, though a barrier oncoviral therapies have faced is a limited therapeutic response to currently delivery techniques.

MAIN BODY

The ability to deliver therapy tailored to specific cellular targets at the precise locus in which it would have its greatest impact is a profound development in anti-cancer treatment. Although immune checkpoint inhibitors have an improved tolerability profile relative to cytotoxic chemotherapy and whole beam radiation, severe immune-related adverse events have emerged as a potential limitation. These include pneumonitis, pancreatitis, and colitis, which are relatively infrequent but can limit therapeutic options for some patients. Intratumor injection of oncolytic viruses, in contrast, has a markedly lower rate of serious adverse effects and perhaps greater specificity to target tumor cells. Early stage clinical trials using oncolytic viruses show induction of effector anti-tumor immune responses and suggest that such therapies could also morph and redefine both the local target cells' niche as well as impart distant effects on remote cells with a similar molecular profile.

CONCLUSION

It is imperative for the modern immuno-oncologist to understand the biological processes underlying the immune dysregulation in cancer as well as the effects, uses, and limitations of oncolytic viruses. It will be with this foundational understanding that the future of oncolytic viral therapies and their delivery can be refined to forge future horizons in the direct modulation of the tumor bed.

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).

Long non-coding RNA HOTAIR modulates HLA-G expression by absorbing miR-148a in human cervical cancer

The long non-coding RNA HOX transcript antisense RNA (HOTAIR) has been found overexpressed in many human malignancies and involved in tumor progression and metastasis. However, little is known about the potential biological roles of HOTAIR in tumor escape. In the present study, the expression of HOTAIR was detected in 59 paired cervical cancer tissue samples by real-time PCR and then subjected to correlation analysis with clinical features. The effects of HOTAIR on cervical cancer cells as well as the expression of human leukocyte antigen (HLA)-G were studied by overexpression and RNA interference approaches. Insight into the mechanism of HOTAIR acting as competitive endogenous RNAs (ceRNAs) was gained from bioinformatic analysis and luciferase assays. HOTAIR expression was obviously increased in cervical cancer tissue. HOTAIR upregulation was associated with advanced pathological stage, histology, lymph node invasion and lymphatic metastasis, and also correlated with shorter overall survival of cervical cancer patients. Furthermore, HOTAIR overexpression promoted the proliferation, migration and invasion of cervical cancer cells, while HOTAIR knockdown inhibited cell invasion and cell viability, induced apoptosis and inhibited growth in vitro and in vivo. Moreover, HOTAIR modulated human leucocyte antigen-G (HLA-G) expression by competitively binding miR-148a. Our data suggest that HOTAIR plays an important oncogenic role in cervical cancer and might serve as a marker for cervical cancer prognosis and a potential target for therapeutic intervention.

14-bp Insertion/Deletion Polymorphism of the HLA-G gene in Breast Cancer among Women from North Western Iran

BACKGROUND

The human leukocyte antigen-G (HLA-G) gene is highly expressed in cancer pathologies and is one strategy used by tumor cells to escape immune surveillance. A 14-bp insertion/deletion (InDel) polymorphism of the HLA-G gene has been suggested to be associated with HLA-G mRNA stability and the expression of HLA-G. The aim of present study was to assess any genetic association between this polymorphism and breast cancer among Iranian-Azeri women.

MATERIALS AND METHODS

In this study 227 women affected with breast cancer, in addition to 255 age-sex and ethnically matched healthy individuals as the control group, participated. Genotyping was performed using polymerase chain reaction and electrophoresis assays. The data were compiled according to the genotype and allele frequencies, compared using the Chi-square test. Statistical significance was set at P<0.05.

RESULTS

In this case-control study, no significant difference was found between the case and control groups at allelic and genotype levels, although there is a slightly higher allele frequency of HLA-G 14bp deletion in breast cancer affected group. However,when the stage I subgroup was compared with stage II plus stage III subgroup of affected breast cancer, a significant difference was seen with the 14 bp deletion allele frequency. The stage II-III subgroup patients had higher frequency of deletion allele (57.4% vs 45.8%) than stage I cases (χ2=4.16, p-value=0.041).

CONCLUSIONS

Our data support a possible action of HLA-G 14bp InDel polymorphism as a potential genetic risk factor for progression of breast cancer. This finding highlights the necessity of future studies of this gene to establish the exact role of HLA-G in progression steps of breast cancer.

Diagnostic and Biological Significance of KIR Expression Profile Determined by RNA-Seq in Natural Killer/T-Cell Lymphoma

Natural killer/T-cell lymphoma (NKTCL) is a rare, aggressive form of non-Hodgkin lymphoma that is generally incurable at more advanced stages with systemic involvement. Clonal diagnostic markers (eg, unique T- or B-cell receptor rearrangements) are not available for NKTCLs. Killer cell immunoglobulin like receptors (KIRs) are a family of type I transmembrane glycoproteins involved in the inhibition or activation of NK cells. A restricted expression profile of KIRs has been proposed as clonal markers of NK-cell proliferations. Here we evaluated the transcription profile of all KIR family genes and C-type lectin receptor genes using RNA sequencing on NKTCL cases (n = 17) and NK-cell lines (n = 3). The expression of all KIRs tended to be markedly reduced or absent in NKTCL, except for the KIR family member killer Ig-like receptor 2DL4 (KIR2DL4; alias CD158D), which was selectively overexpressed in the majority (59%) of cases. No specific expression pattern was observed for C-type lectin receptors. KIR2DL4 is an unusual member of the KIR family that recognizes human leukocyte antigen G and mediates NK-cell activation through inducing proliferation and survival pathways such as AKT and NF-κB. Stable knockdown of KIR2DL4 in two malignant NK-cell lines with high KIR2DL4 expression significantly reduced cell growth. Selective overexpression of KIR2DL4 and down-regulation of inhibitory KIRs may contribute to NKTCL pathogenesis.

Targeting Epigenetic Processes in Photodynamic Therapy-Induced Anticancer Immunity

Photodynamic therapy (PDT) of cancer is an approved therapeutic procedure that generates oxidative stress leading to cell death of tumor and stromal cells. Cell death resulting from oxidative damage to intracellular components leads to the release of damage-associated molecular patterns (DAMPs) that trigger robust inflammatory response and creates local conditions for effective sampling of tumor-associated antigens (TAA) by antigen-presenting cells. The latter can trigger development of TAA-specific adaptive immune response. However, due to a number of mechanisms, including epigenetic regulation of TAA expression, tumor cells evade immune recognition. Therefore, numerous approaches are being developed to combine PDT with immunotherapies to allow development of systemic immunity. In this review, we describe immunoregulatory mechanisms of epigenetic treatments that were shown to restore the expression of epigenetically silenced or down-regulated major histocompatibility complex molecules as well as TAA. We also discuss the results of our recent studies showing that epigenetic treatments based on administration of methyltransferase inhibitors in combination with PDT can release effective mechanisms leading to development of antitumor immunity and potentiated antitumor effects.

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.

The use of anchored agonists of phagocytic receptors for cancer immunotherapy: B16-F10 murine melanoma model

The application of the phagocytic receptor agonists in cancer immunotherapy was studied. Agonists (laminarin, molecules with terminal mannose, N-Formyl-methioninyl-leucyl-phenylalanine) were firmly anchored to the tumor cell surface. When particular agonists of phagocytic receptors were used together with LPS (Toll-like receptor agonist), high synergy causing tumour shrinkage and a temporary or permanent disappearance was observed. Methods of anchoring phagocytic receptor agonists (charge interactions, anchoring based on hydrophobic chains, covalent bonds) and various regimes of phagocytic agonist/LPS mixture applications were tested to achieve maximum therapeutic effect. Combinations of mannan/LPS and f-MLF/LPS (hydrophobic anchors) in appropriate (pulse) regimes resulted in an 80% and 60% recovery for mice, respectively. We propose that substantial synergy between agonists of phagocytic and Toll-like receptors (TLR) is based on two events. The TLR ligand induces early and massive inflammatory infiltration of tumors. The effect of this cell infiltrate is directed towards tumor cells, bearing agonists of phagocytic receptors on their surface. The result of these processes was effective killing of tumor cells. This novel approach represents exploitation of innate immunity mechanisms for treating cancer.

The role of tumor-infiltrating immune cells and chronic inflammation at the tumor site on cancer development, progression, and prognosis: emphasis on non-small cell lung cancer

In addition to malignant neoplastic cells, cancer tissues also include immune cells, fibroblasts, and endothelial cells, including an abundant collection of growth factors, proangiogenic mediators, cytokines, chemokines, and components of the extracellular matrix. The main physiological function of the immune cells is to monitor tissue homeostasis, to protect against invading pathogens, and to eliminate transformed or damaged cells. Between immune cells and malignant cells in the tumor stroma, there is in fact a complex interaction which has significant prognostic relevance as the immune system has both tumor-promoting and -inhibiting roles. In non-small cell lung cancer (NSCLC), there is a marked infiltration of different types of immune cells, and the distribution, tissue localization, and cell types are significantly associated with progression and survival. Cancer immunotherapy has seen a significant progress during the last decade. An increased understanding of the mechanisms by which lung cancer cells escape the immune system, and the recognition of the key tumor antigens and immune system components in tumor ignorance have led to the development of several lung cancer vaccines. As the NSCLC prognosis in general is dismal, one may hope that future immunotherapy may be an effective adjunct to standard therapy, reversing immunologic tolerance in the tumor microenvironment. This review reports on the tumor stroma and in particular tumor-suppressing and -promoting roles of the immune system. Furthermore, it presents recent literature on relevant immune cell-related research in NSCLC.

HLA-G expression is associated with metastasis and poor survival in the Balb/c nu/nu murine tumor model with ovarian cancer

Aberrant HLA-G expression is associated with tumor invasiveness and poor clinical prognosis; however, there is a lack of preclinical animal model to address whether HLA-G plays a causal role in the unfavorable prognosis of malignancies. In the current study, ovarian carcinoma cell lines (HO-8910 and Ovcar-3) were transfected with HLA-G gene. HLA-G expression was analyzed with western blot and flow cytometry. Transwell experiment was performed to analyze the cell migration and invasion capability and/or multicellular spheroid formation was investigated with the 3D culture assay in vitro. The effects of HLA-G expression for tumor cell organ metastasis and for mouse survival was analyzed with the Balb/c nu/nu mouse model. Our data showed that HO-8910-G and Ovcar-3-G cells are of higher invasion potential compared with the parental HO-8910 and Ovcar-3 cells. Multicellular spheroid formation exists only in HO-8910-G cells in a 3D culture assay. In Balb/c nu/nu mouse model, widespread metastasis was observed in mice xenografted with HO-8910-G cells, but not in the group with parental cells. Mouse survival was dramatically decreased in HO-8910-G and Ovcar-3-G xenografted mice than that with HO-8910 and Ovcar-3 cells, respectively. In summary, our study provided the first evidence that HLA-G expression is associated with tumor metastasis and with poor survival in an animal model with ovarian cancer.

Natural innate and adaptive immunity to cancer

The immune system can identify and destroy nascent tumor cells in a process termed cancer immunosurveillance, which functions as an important defense against cancer. Recently, data obtained from numerous investigations in mouse models of cancer and in humans with cancer offer compelling evidence that particular innate and adaptive immune cell types, effector molecules, and pathways can sometimes collectively function as extrinsic tumor-suppressor mechanisms. However, the immune system can also promote tumor progression. Together, the dual host-protective and tumor-promoting actions of immunity are referred to as cancer immunoediting. In this review, we discuss the current experimental and human clinical data supporting a cancer immunoediting process that provide the fundamental basis for further study of immunity to cancer and for the rational design of immunotherapies against cancer.

Shifting the equilibrium in cancer immunoediting: from tumor tolerance to eradication

The continual interaction of the immune system with a developing tumor is thought to result in the establishment of a dynamic state of equilibrium. This equilibrium depends on the balance between effector and regulatory T-cell compartments. Whereas regulatory T cells can infiltrate and accumulate within tumors, effector T cells fail to efficiently do so. Furthermore, effector T cells that do infiltrate the tumor become tightly controlled by different regulatory cellular subsets and inhibitory molecules. The outcome of this balance is critical to survival, and whereas in some cases the equilibrium can rapidly result in the elimination of the transformed cells by the immune system, in many other cases the tumor manages to escape immune control. In this review, we discuss relevant work focusing on the establishment of the intratumor balance, the dynamic changes in the populations of effector and regulatory T cells within the tumor, and the role of the tumor vasculature and its activation state in the recruitment of different T-cell subsets. Finally, we also discuss work associated to the manipulation of the immune response to tumors and its impact on the infiltration, accumulation, and function of tumor-reactive lymphocytes within the tumor microenvironment.

Human leukocyte antigen G expression in breast cancer: role in immunosuppression

Human leukocyte antigen G (HLA-G) is an immunotolerant nonclassical major histocompatibility complex Class Ib molecule. It is expressed by trophoblastic placental cells during pregnancy to protect the fetus from maternal alloreactivity. HLA-G is overexpressed in tumors and involved in cancer immune evasion. Reverse transcription-polymerase chain reaction and immunohistochemistry (IHC) were used to examine HLA-G expression in normal mammary and breast cancer cell lines and normal and human breast cancer tissues. Reverse transcription-polymerase chain reaction confirmed that normal epithelial MCF-12A cells had no HLA-G mRNA expression, whereas cancer cell lines MCF-7, T47D, and MDA-MB-231 and NCI/Adr-Res had various levels of HLA-G mRNA expression. Twelve (12) normal and 38 breast cancer tissues were examined by IHC. Fifty-eight (58) percent (22/38) of cancers had medium to strong staining to HLA-G, whereas only 8% (1/12) of normal breast tissues had medium to strong staining, and the difference was significant (p < 0.05). HLA-G staining was found in the membranes and cytoplasm of cancer cells. In conclusion, breast cancer cells overexpress HLA-G mRNA and protein, and this probably contributes to immune evasion.

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

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

Implications of the polymorphism of HLA-G on its function, regulation, evolution and disease association

The HLA-G gene displays several peculiarities that are distinct from those of classical HLA class I genes. The unique structure of the HLA-G molecule permits a restricted peptide presentation and allows the modulation of the cells of the immune system. Although polymorphic sites may potentially influence all biological functions of HLA-G, those present at the promoter and 3′ untranslated regions have been particularly studied in experimental and pathological conditions. The relatively low polymorphism observed in the MHC-G coding region both in humans and apes may represent a strong selective pressure for invariance, whereas, in regulatory regions several lines of evidence support the role of balancing selection. Since HLA-G has immunomodulatory properties, the understanding of gene regulation and the role of polymorphic sites on gene function may permit an individualized approach for the future use of HLA-G for therapeutic purposes.

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

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

The prognostic role of classical and nonclassical MHC class I expression in endometrial cancer

The aim of this study was to investigate classical MHC class I and nonclassical MHC (human leukocyte antigen-G [HLA-G]) expression in a large cohort of patients with endometrial cancer, to determine the prognostic value of these cell surface markers and their relation with clinicopathological variables. Tissue microarrays containing epithelial endometrial carcinoma tissue from 554 patients were stained for classical and nonclassical MHC class I using the following monoclonal antibodies: 4H84 (anti-HLA-G), beta2-m (anti-beta-2-microglobulin) and HC-10 (MHC class I antigen heavy chain). Expression data were linked to known clinicopathological characteristics and survival. HLA-G upregulation and MHC class I downregulation in neoplastic cells was observed in 40% and 48%, respectively. Nonendometrioid tumor type, advanced stage disease (FIGO stage > or = II) and poorly or undifferentiated tumors were associated with MHC class I downregulation. Absence of HLA-G expression was independently associated with MHC class I downregulation. In univariate analysis, MHC class I downregulation was a predictor of worse disease-specific survival. Prognostic unfavorable tumor characteristics were correlated with downregulation of MHC class I expression in endometrial cancer cells. Furthermore, downregulated MHC class I has a negative impact on disease-specific survival, observed in a large cohort of patients with endometrial cancer. As there seems to be a relation between classical and nonclassical MHC class I molecules (HLA-G), further research is warranted to unravel this regulatory mechanism.

Tumor immunosuppressive environment: effects on tumor-specific and nontumor antigen immune responses

The interactions between cancer cells and host immune cells in tumoral microenvironments create an immunosuppressive network that promotes tumor growth, protects the tumor from immune attack and attenuates the efficacy of immunotherapeutic approaches. The development of immune tolerance becomes predominant in the immune system of patients with advanced-stage tumors. Several mechanisms have been described by which tumors can suppress the immune system, including secretion of cytokines, alterations in antigen-presenting cell subsets, costimulatory and coinhibitory molecule alterations and altered ratios of Tregs to effector T cells. It is well demonstrated that these mechanisms of immunosuppression can impair tumor specific immune responses. However, it is not well established whether this immunosuppressive environment can affect immune responses to nontumor antigens, specifically in regard to priming and the development of memory. The few existing studies indicate that responses to nontumor antigens seem unaffected, although there is still a deep lack of understanding of this phenomenon. This is an important issue regarding patient endurance and quality of life. Here, we review the existing evidence on immunosuppression promoted by tumors, with particular attention to its impact on specific immune responses. Understanding these interactions can help us subvert tumor-induced tolerance and optimize anti-tumor therapy.

Correlation of human leukocyte antigen-G (HLA-G) expression and disease progression in epithelial ovarian cancer

Human leukocyte antigen-G (HLA-G) expression has been reported to be relevant to cancer development and immune tolerance. The purpose of this study was to investigate the correlation between HLA-G expression and disease progression and to assess the use of HLA-G expression as a prognostic immunomarker in epithelial ovarian carcinoma. Human leukocyte antigen-G expression in 41 ovarian cancer tissues and 8 normal ovarian tissues was analyzed using immunohistochemistry and Western blot assay. Quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) was used for HLA-G messenger RNA (mRNA) expression. Human leukocyte antigen-G mRNA and protein levels were significantly greater in advanced ovarian cancer tissues than in normal or early stage ovarian cancer tissues (P < .05 and P < .05, respectively). Patients with HLA-G expression had a significantly worse prognosis. There is a significant correlation between HLA-G immunoreactivity and patient survival in univariate analysis (P = .04). Our data was consistent with the concept that HLA-G expression might play a pivotal role in the development and disease progression of epithelial ovarian cancer.

[Importance of HLA-G in therapy of cancer]

HLA-G (Human Leucocyte Antigen-G) is a non-classical HLA class I molecule observed for the first time in human cytotrophoblast. Numbers of investigations have demonstrated that HLA-G was broader than originally thought. In fact, it is expressed in pathological contexts as well as in physiological contexts. This expression of HLA-G and its receptors in immunity cells confer to it a major role in immune responses. Good issues were described in organ transplantation when HLA-G was expressed. But, HLA-G transcripts and/or proteins expression in tumor tissues was associated with tumor genesis and cancer progression. A focus on the expression and the role of HLA-G in tumor context will be developed in this review. In addition, regulation of HLA-G will be treated to improve strategies of cancer therapy.

Unfavourable clinical implications for HLA-G expression in acute myeloid leukaemia

Human leukocyte antigen-G (HLA-G) molecule exerts multiple immunoregulatory functions that have been suggested to contribute to the immune evasion of tumour cells. Studies on HLA-G expression in malignant haematopoietic diseases are controversial, and the functions of HLA-G on this context are limited. In the current study, HLA-G expression was analysed in different types of patients: de novo acute myeloid leukaemia (AML, n = 54), B cell acute lymphoblastic leukaemia (B-ALL, n= 13), chronic myeloid leukaemia (CML, n= 9) and myelodysplastic syndrome (MDS, n= 11). HLA-G expression was observed in 18.5% cases of AML, 22.2% in CML and 18.2% in MDS, but not in B-ALL patients. In AML, HLA-G-positive patients had a significant higher bone marrow leukaemic blast cell percentage when compared with that of HLA-G-negative patients (P < 0.01). Total T-cell percentage was dramatically decreased in HLA-G-positive patients (P < 0.05). Cytogenetic karyotyping results showed that all HLA-G-positive AML patients (n= 5) were cytogenetically abnormal, which was markedly different from that of HLA-G-negative patients (P < 0.01). Ex vivo cytotoxicity analysis revealed that HLA-G expression in AML leukaemic cells could directly inhibit NK cell cytolysis (P < 0.01). These findings indicated that HLA-G expression in AML is of unfavourable clinical implications, and that HLA-G could be a potential target for therapy.

Epigenetic changes within the promoter region of the HLA-G gene in ovarian tumors

Background

Previous findings have suggested that epigenetic-mediated HLA-G expression in tumor cells may be associated with resistance to host immunosurveillance. To explore the potential role of DNA methylation on HLA-G expression in ovarian cancer, we correlated differences in HLA-G expression with methylation changes within the HLA-G regulatory region in an ovarian cancer cell line treated with 5-aza-deoxycytidine (5-aza-dC) and in malignant and benign ovarian tumor samples and ovarian surface epithelial cells (OSE) isolated from patients with normal ovaries.

Results

A region containing an intact hypoxia response element (HRE) remained completely methylated in the cell line after treatment with 5-aza-dC and was completely methylated in all of the ovarian tumor (malignant and benign) samples examined, but only variably methylated in normal OSE samples. HLA-G expression was significantly increased in the 5-aza-dC treated cell line but no significant difference was detected between the tumor and OSE samples examined.

Conclusion

Since HRE is the binding site of a known repressor of HLA-G expression (HIF-1), we hypothesize that methylation of the region surrounding the HRE may help maintain the potential for expression of HLA-G in ovarian tumors. The fact that no correlation exists between methylation and HLA-G gene expression between ovarian tumor samples and OSE, suggests that changes in methylation may be necessary but not sufficient for HLA-G expression in ovarian cancer.

HLA-G expression in human ovarian carcinoma counteracts NK cell function

BACKGROUND

Human leukocyte antigen-G (HLA-G) is an important immunotolerant which could be a part of the strategies applied by malignant cells applied to avoid host immunosurveillance. Aberrant expression of HLA-G has been found in ovarian carcinoma. The aim of this study was to evaluate the HLA-G expression in ovarian cancer tissues and to explore its function in vitro.

MATERIALS AND METHODS

HLA-G expression in 33 primary ovarian carcinoma tissues was analyzed using immunohistochemistry with the anti-HLA-G monoclonal antibody (mAb) 4H84. Furthermore, the function of HLA-G in NK cell cytotoxicity was determined in vitro by cloning and expression of HLA-G on the ovarian carcinoma cell OVCAR-3.

RESULTS

HLA-G expression was detected in 22/33 (66.7%) primary tumor tissues, but was absent in normal ovarian tissues (P<0.01). Cytotoxicity studies showed that HLA-G expression dramatically inhibits cell lyses by NK-92 cells (P<0.01), which could be restored by the anti-HLA-G conformational mAb 87G (P<0.01).

CONCLUSION

HLA-G was expressed in a significant number of primary ovarian carcinoma tissues, and HLA-G expression in OVCAR-3 could directly inhibit NK-92 cell lysis. Taken together, our results indicated that expression of HLA-G plays an important role in evasion of ovarian cancer cells from host immunosurveillance.

Structure, expression and function of HLA-G in renal cell carcinoma

Tumors have developed different strategies to escape from immune cell recognition which include the downregulation or loss of the classical HLA class I antigens as well as aberrant expression of non-classical HLA antigens like HLA-G. Abnormalities in MHC class surface expression have also been described in renal cell carcinoma (RCC) and represent mechanisms to avoid elimination by immune effector cells. We here review the structure/polymorphism, mRNA and protein expression profile of HLA-G in RCC and corresponding normal kidney epithelium, its mode of regulation and its functional consequences on immune responses. A heterogeneous constitutive HLA-G mRNA and/or protein expression was found in both RCC lesions and RCC cell lines, whereas normal kidney epithelium totally lack HLA-G mRNA and protein expression. In comparison to other tumor entities, the frequency of HLA-G expression is relatively high in RCC. Since HLA-G expression is lost during cultivation of RCC cells, the tumor microenvironment and/or endothelium appear to be involved in the regulation of HLA-G expression in this disease. HLA-G expression could be transcriptionally upregulated in RCC by interferons, IL-10 and gangliosides. Silencing of HLA-G expression in RCC is often associated with methylation of the HLA-G promoter which could be reverted by the treatment with demethylating agents. Functional studies using natural killer cells, lymphokine activated killer cells as well as antigen-specific CD8+ cytotoxic T lymphocytes demonstrated that HLA-G expression prevents lysis of RCC cells by these different immune effector cells. In contrast, HLA-G-negative normal kidney cells as well as HLA-G-negative RCC cells were not recognized by NK and T cells. Thus, HLA-G represents one important immune escape mechanism of human RCC which has an impact on the design of T and NK cell-based immunotherapies in this disease.

Lenatural killer, fer de lance des futures immunothérapies anti-tumorales ?

Natural Killer (NK) cells are no longer considered as relatively unimportant bystander cells having the capacity to kill certain tumor and virus-infected cells in a mysterious way. During the last decade a significant progress has been made in understanding biology of NK cells in particular their mechanisms of recognition and killing of target cells. This progress has led to novel knowledge-based clinical applications of NK cells as immunotherapeutic tools in various disease settings, especially in bone marrow transplantation for leukemia patients. The potential of NK cell therapy for eradicating solid tumors has not been fully exploited. In this mini-review, we examine the rationale behind these therapies and discuss the problems confronting researchers in their usage as therapeutic agents.

Soluble HLA-G is absent from human embryo cultures: a reassessment of sHLA-G detection methods

In recent years, the number of patients receiving in vitro fertilization (IVF) has been increasing, though the rate of successful implantations has remained at 10-20%. A major goal of this procedure is to afford the ability to select embryos with the most potential for implantation and development. Previous studies claimed to have detected soluble HLA-G (sHLA-G) protein in culture supernatant from 2 to 3-day embryos using ELISA methods, and concluded that sHLA-G protein levels were associated with successful implantation. This result, if substantiated could provide an important tool for IVF. In this study, we have re-examined these experiments by attempting to detect sHLA-G in the medium from 2 to 3-day embryos (84 samples) and 4 to 6-day embryos (25 samples) in which a part of blastocyst has started to differentiate into trophoblasts. Using a highly specific and sensitive ELISA, no sHLA-G protein was detectable in any sample, despite the fact that 27 of the 109 samples were from successfully implanted embryos. These results indicate that 2-6-day embryos do not secrete sHLA-G detectable by ELISA, and therefore that sHLA-G in culture medium is not a useful for successful implantation at this stage of development.

Immune surveillance of tumors

The ability of the immune system to identify and destroy nascent tumors, and to thereby function as a primary defense against cancer, has been debated for many decades. Recent findings by a number of investigators in both mouse models of cancer and humans with cancer now offer compelling evidence that particular immune cell types, effector molecules, and pathways can sometimes collectively function as extrinsic tumor suppressor mechanisms. This work provides the basis for further study of natural immunity to cancer and for rational use of this information in the design of immunotherapies in combination with other conventional cancer treatments.

Play it in E or G: utilization of HLA-E and -G in xenotransplantation

Human NK cell-mediated graft rejection is likely to be one of several biological obstacles to routine pig-to-human xenotransplantation. Abrogating NK cell activation by either elimination of activating ligands on porcine cells or expression of molecules serving as ligands for NK cell inhibitory receptors, or both, could overcome this hurdle. HLA-E and -G exhibit very limited polymorphism and are ligands for NK cell inhibitory receptors. This review summarizes successes and limitations of their use in xenotransplantation as inferred from ex vivo analyses of NK cell activity, highlights potential effects they may have on T-cell responses, and considers prospects of preclinical trials and potential outcomes.