HLA-E expression and its clinical relevance in human renal cell carcinoma.

The non-classical human leukocyte antigen E (HLA-E) expression is frequently overexpressed in tumor diseases, transplants and virus-infected cells and represents an immunomodulatory molecule by binding to the receptors CD94/NKG2A, -B and -C on NK and T cells. Due to its immune suppressive features HLA-E expression might represent an important mechanism of tumors to escape immune surveillance.While an aberrant expression of the non-classical HLA-G antigen in human renal cell carcinoma (RCC) has been demonstrated to be associated with a worse outcome of patients and reduced sensitivity to immune effector cell-mediated cytotoxicity, the expression and function of HLA-E has not yet been analyzed in this tumor entity.Higher levels of HLA-E transcripts were detected in all RCC cell lines and tumor lesions, which were tested in comparison to normal kidney epithelium. Immunohistochemical staining of a tissue microarray (TMA) using the HLA-E-specific monoclonal antibody TFL-033 recognizing the cytoplasmic HLA-E α-chain as monomer revealed a heterogeneous HLA-E expression in RCC lesions with the highest frequency in chromophobe RCC when compared to other RCC subtypes. HLA-E expression did not correlate with the frequency of CD3+, CD4+, CD8+ and FoxP3+ immune cell infiltrations, but showed an inverse correlation with infiltrating CD56+ cells. In contrast to HLA-G, HLA-E expression in RCCs was not statistically significant associated with a decreased disease specific survival. These data suggest that HLA-E overexpression frequently occurs in RCC and correlates with reduced immunogenicity.

Clinical relevance of miR-mediated HLA-G regulation and the associated immune cell infiltration in renal cell carcinoma.

In human tumors of distinct origin including renal cell carcinoma (RCC), the non-classical human leukocyte antigen G (HLA-G) is frequently expressed, thereby inhibiting the cytotoxic activity of T and natural killer (NK) cells. Recent studies demonstrated a strong post-transcriptional gene regulation of the HLA-G by miR-152, -148A, -148B and -133A. Standard methods were applied to characterize the expression and function of HLA-G, HLA-G-regulatory microRNAs (miRs) and the immune cell infiltration in 453 RCC lesions using a tissue microarray and five RCC cell lines linking these results to clinical parameters. Direct interactions with HLA-G regulatory miRs and the HLA-G 3' untranslated region (UTR) were detected and the affinities of these different miRs to the HLA-G 3'-UTR compared. qPCR analyses and immunohistochemical staining revealed an inverse expression of miR-148A and -133A with the HLA-G protein in situ and in vitro. Stable miR overexpression caused a downregulation of HLA-G protein enhancing the NK and LAK cell-mediated cytotoxicity in in vitro CD107a activation assays revealing a HLA-G-dependent cytotoxic activity of immune effector cells. A significant higher frequency of CD3+/CD8+ T cell lymphocytes, but no differences in the activation markers CD69, CD25 or in the presence of CD56+, FoxP3+ and CD4+ immune cells were detected in HLA-G+ compared to HLA-G- RCC lesions. This could be associated with higher WHO grade, but not with a disease-specific survival. These data suggest a miR-mediated control of HLA-G expression in RCC, which is associated with a distinct pattern of immune cell infiltration.

Piwi-like 1 and 4 gene transcript levels are associated with clinicopathological parameters in renal cell carcinomas.

Piwi-like gene family members (Piwil 1-4) are considered stem cell-associated genes/proteins. These are expressed predominantly in germline cells, but are re-expressed in different tumors. Piwil 1-4 gene expression has not previously been studied and correlated with clinicopathological parameters in renal cell carcinomas (RCC). The Piwil 1-4 transcript levels were analyzed by quantitative real-time PCR in 73 clear cell RCC (ccRCC) tissues and corresponding normal tissues. The transcript levels of Piwil 1, 2 and 4 were strongly and significantly correlated with each other, in both the tumor tissues and the normal tissues (P<0.001; Spearman's rank test). Piwil 4 gene expression was significantly higher in the ccRCC tissues than that in the corresponding normal renal tissues (P<0.001; Wilcoxon signed-rank test). When the ccRCC patient cohort was divided according to the median Piwil 1-4 expression into low- and high-expression groups and according to age into younger (≤64years) and older patient groups (>64years), the younger patients displayed significantly higher levels of Piwil 1 mRNA in comparison to the older patients (P=0.010; Fisher's exact test). Interestingly, Piwil 1 expression was left-right polarized in the normal tissues but not in the tumor tissues (P=0.004; Fisher's exact test). Altogether, associations were determined between the Piwi-like family member expression levels and clinicopathological parameters of ccRCC, suggesting a potential role for these genes/proteins in ccRCC diagnostics and tumorigenesis as well as in renal tissue embryology.

Prognostic factors of papillary renal cell carcinoma: results from a multi-institutional series after pathological review.

PURPOSE: We examined papillary renal cell carcinoma prognostic variables and validated the 2002 UICC TNM staging system in a multicenter analysis. MATERIALS AND METHODS: From 10 urological institutions in Germany followup data were collected on a total of 675 patients with papillary renal cell carcinoma. Central pathological review was done to validate external histopathological diagnoses. The Kaplan-Meier method was used to derive cumulative cancer specific and overall survival, and the log rank test was used to compare the curves of 2 or more groups. For multivariate analysis of prognostic factors Cox regression analysis was done. All proportional hazard assumptions were systemically verified using the Grambsch-Therneau test. RESULTS: Cancer specific survival was significantly related to TNM stage and histological grading on univariate and multivariate analyses. Five-year cancer specific survival in pT1b cases was significantly shorter than in pT1a cases (90.0% vs 98.3%, p = 0.017). No significant difference was found between pT1b and pT2 tumors. Patients with pT3 or greater disease were at high risk for metastasis (50.6%) while metastatic disease associated with pT2 or less tumors occurred in 7.8% (p <0.0001). After metastatic disease was present the prognosis was poor with 7.2% 5-year cancer specific survival. Age was associated with poor prognosis in the subgroup with pT3 or greater tumors on univariate analysis (p = 0.026) but not on multivariate analysis. CONCLUSIONS: In its current form the 2002 UICC TNM staging system is not applicable to papillary renal cell carcinoma. Clinical and radiological followup should be offered at frequent intervals to patients with venous thrombus and/or locally advanced disease. The role of age remains unclear but should not be underestimated in risk stratification after surgery.