Characterization of human leukocyte antigen-G (HLA-G) expression in endometrial adenocarcinoma.
ABSTRACT The current study sought to determine if endometrial adenocarcinomas express human leukocyte antigen-G (HLA-G), an immune-regulatory protein, and if degree of expression correlates with the stage of carcinoma.
Forty-four primary endometrial adenocarcinomas were tested using immunohistochemical staining with the 4H84 anti-HLA-G monoclonal antibody. Metastatic implants were not included. A subset of 10 samples was tested using RNA in situ hybridization to confirm the presence of HLA-G transcript. Results of staining were analyzed with respect to grade, tumor histology, and stage of disease. Spearman rank correlation was used to assess tumor grade, histology, and disease stage as a function of HLA-G protein staining. Receiver-operator characteristic (ROC) curve analysis was used to determine the feasibility of HLA-G protein staining as a clinical marker for advanced stage disease.
Immunohistochemical staining for HLA-G protein was seen in 55% (24/44) of primary site endometrial adenocarcinomas and localized to glandular but not stromal epithelium. RNA in situ hybridization confirmed the presence of transcript in the majority of samples tested and also localized to glandular epithelium. A significant correlation was seen with increasing HLA-G protein staining and increasing stage of endometrial cancer, P < 0.01. HLA-G was found to be a fair discriminator as a test for metastatic disease with an area under the ROC curve of 0.75 for metastatic versus non-metastatic disease.
HLA-G protein is expressed in a significant number of endometrial adenocarcinomas, in which it is localized to the glandular epithelium. HLA-G may serve as a clinical marker for the preoperative prediction of metastatic endometrial cancer.
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ABSTRACT: HLA-G belongs to the nonclassical MHC class Ib group of molecules and has been implicated in mediating immune-responsiveness in various cancerous and non-cancerous cell types. We have examined HLA-G expression in a number of human gastrointestinal malignancies, including pancreatic ductal adenocarcinoma, ampullary cancer, biliary cancer, and colorectal cancer by immunolabeling analysis. We used indices of <5% (negative), 6-25%, 26-50%, 51-75%, and >75% (diffuse) to subclassify lesions based on percentage of positive cell labeling. Across all cancer subtypes, 52-79% of lesions demonstrated expression of HLA-G, with up to 33% of lesions demonstrating diffuse (>75%) expression. In addition, we utilized the neoplastic progression model of colorectal cancer to evaluate HLA-G protein expression in normal colon, tubulovillous adenomas, invasive cancer, and liver metastases arising from colorectal cancer. Focal HLA-G expression was detected in regions of normal colon adjacent to sites of adenomatous and cancerous lesions, as well as in all stages of cancer progression. Overall, the percentage of diffusely (>75%) labeled lesions appeared increased in preneoplastic and neoplastic conditions, as compared to normal colon. Specifically, tubulovillous adnenomas demonstrated pronounced diffuse labeling in 58% of lesions examined. No correlation with HLA-G expression and CD4+ or CD8+ T cells was identified. We propose that HLA-G expression is upregulated in a large percentage of gastrointestinal lesions and may serve to mediate immune-responsiveness in certain instances.International Journal of Gastrointestinal Cancer 02/2005; 35(1):15-23.
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ABSTRACT: IFN-gamma regulates the immunogenicity of target cells by increasing their expression of HLA class I molecules. This facilitates the T cell receptor-mediated recognition by CD8(+) T cells but decreases target cell sensitivity to lysis by NK cells due to engagement of inhibitory NK receptors. In this study, short-term tumor cell lines from patients with advanced ovarian carcinomas were established. We demonstrate the paradoxical finding that IFN-gamma treatment of these short-term ovarian carcinoma cell lines (OVACs) resulted in resistance of tumor cells to lysis by peptide- and allospecific CD8(+) T cells. Blocking experiments revealed that this phenomenon was dependent on enhanced inhibitory signalling via CD94/NKG2A receptors expressed on the effector cells. This was associated with increased expression of HLA-E mRNA and HLA-G at the protein level in IFN-gamma-treated OVACs. Furthermore, pulsing of untreated OVACs with the leader sequence peptide of HLA-G protected these cells from lysis by CTLs, thus mimicking the inhibitory effect of IFN-gamma. This study provides evidence that CD94/NKG2A receptors play an important role in regulating T cell activity against tumors and shows that IFN-gamma modulation of target cells may shift the balance of triggering and inhibitory signals to T cells, turning off their cytolytic activity.Journal of Clinical Investigation 12/2002; 110(10):1515-23. · 12.81 Impact Factor
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ABSTRACT: The nonclassical HLA-G molecule exhibits a limited tissue distribution and exerts multiple immune regulatory functions. Recent studies indicate that HLA-G expression plays a key role in the induction of immune tolerance and may represent a novel immune escape mechanism of tumor cells. Despite a high frequency of tumor-infiltrating T lymphocytes in renal cell carcinoma (RCC) lesions, outgrowth of tumor cells occurs that might be attributable to abrogation-efficient antitumor responses. To delineate the potential role of HLA-G in RCC immunology, the HLA-G expression pattern and its functional consequences on immune responses were analyzed in cell lines and lesions derived from primary RCC lesions. A heterogeneous constitutive and IFN-gamma-inducible HLA-G mRNA and protein expression was found in 12.5% of RCC cell lines but not in autologous normal kidney cells. Western blot analysis of 37 primary RCC lesions revealed HLA-G protein expression in 27% of RCC lesions. Functional studies performed with alloreactive natural and lymphokine-activated killer cells as well as antigen-specific CD8(+) T-cell populations demonstrated that HLA-G expression inhibits lysis of RCC cells by these different immune effector cells, whereas HLA-G(-) normal kidney cells were recognized. Furthermore, the HLA-G-mediated counteraction of immune response could be restored by antibody blocking experiments. Thus, aberrant HLA-G expression is found at a relatively high frequency in RCC and might participate in evasion of these tumor cells from immunosurveillance.Cancer Research 08/2003; 63(14):4107-11. · 8.65 Impact Factor