The protein tyrosine phosphatase receptor type J is regulated by the pVHL-HIF axis in clear cell renal cell carcinoma.

Mass spectrometry analysis of renal cancer cell lines recently suggested that the protein-tyrosine phosphatase receptor type J (PTPRJ), an important regulator of tyrosine kinase receptors, is tightly linked to the von Hippel-Lindau protein (pVHL). Therefore, we aimed to characterize the biological relevance of PTPRJ for clear cell renal cell carcinoma (ccRCC). In pVHL-negative ccRCC cell lines, both RNA and protein expression levels of PTPRJ were lower than those in the corresponding pVHL reconstituted cells. Quantitative RT-PCR and western blot analysis of ccRCC with known VHL mutation status and normal matched tissues as well as RNA in situ hybridization on a tissue microarray (TMA) confirmed a decrease of PTPRJ expression in more than 80% of ccRCCs, but in only 12% of papillary RCCs. ccRCC patients with no or reduced PTPRJ mRNA expression had a less favourable outcome than those with a normal expression status (p = 0.05). Sequence analysis of 32 PTPRJ mRNA-negative ccRCC samples showed five known polymorphisms but no mutations, implying other mechanisms leading to PTPRJ's down-regulation. Selective silencing of HIF-α by siRNA and reporter gene assays demonstrated that pVHL inactivation reduces PTPRJ expression through a HIF-dependent mechanism, which is mainly driven by HIF-2α stabilization. Our results suggest PTPRJ as a member of a pVHL-controlled pathway whose suppression by HIF is critical for ccRCC development.

Genetic depletion of complement receptors CD21/35 prevents terminal prion disease in a mouse model of chronic wasting disease.

The complement system has been shown to facilitate peripheral prion pathogenesis. Mice lacking complement receptors CD21/35 partially resist terminal prion disease when infected i.p. with mouse-adapted scrapie prions. Chronic wasting disease (CWD) is an emerging prion disease of captive and free-ranging cervid populations that, similar to scrapie, has been shown to involve the immune system, which probably contributes to their relatively facile horizontal and environmental transmission. In this study, we show that mice overexpressing the cervid prion protein and susceptible to CWD (Tg(cerPrP)5037 mice) but lack CD21/35 expression completely resist clinical CWD upon peripheral infection. CD21/35-deficient Tg5037 mice exhibit greatly impaired splenic prion accumulation and replication throughout disease, similar to CD21/35-deficient murine prion protein mice infected with mouse scrapie. TgA5037;CD21/35(-/-) mice exhibited little or no neuropathology and deposition of misfolded, protease-resistant prion protein associated with CWD. CD21/35 translocate to lipid rafts and mediates a strong germinal center response to prion infection that we propose provides the optimal environment for prion accumulation and replication. We further propose a potential role for CD21/35 in selecting prion quasi-species present in prion strains that may exhibit differential zoonotic potential compared with the parental strains.

TP53 mutations are common in all subtypes of epithelial ovarian cancer and occur concomitantly with KRAS mutations in the mucinous type.

AIMS: Epithelial ovarian cancer (EOC) can be classified into four major types (serous, endometrioid, clear cell, mucinous). The prevalence of driver gene mutations in the different subtypes is controversial. High-grade serous carcinomas show frequent TP53 mutations, whereas KRAS and BRAF mutations are less common. In non-serous EOC, the relevance of these gene mutations remains to be elucidated. METHODS: We investigated 142 formalin-fixed, paraffin-embedded EOC, including serous (n=63), endometrioid (n=29), clear cell (n=25), mucinous (n=14), and others (n=11) for mutations in TP53 exons 5-8, KRAS exons 2 and 3, and BRAF exon 15 by pyro-sequencing using the GS Junior 454 platform. The mutational status was correlated with clinicopathological features and patient overall survival. RESULTS: We identified mutations in the coding region of TP53 in 51.4% (73/142), and of KRAS in 9.9% (14/142) but not of BRAF. TP53 mutations occurred frequently not only in high-grade serous carcinomas (58.7%), but also in mucinous (57%) and clear cell EOC (52%). TP53 mutations were associated with high-grade carcinomas (p=0.014), advanced FIGO stage (p=0.001), intraoperative residual disease >1cm (p=0.004), as well as poor overall survival (p=0.002). KRAS mutations were mainly identified in mucinous EOC (57%) and were concomitantly with TP53 mutations in five mucinous carcinomas (36%). CONCLUSIONS: TP53 gene driver mutations are a common feature of all advanced ovarian cancer subtypes, whereas BRAF mutations seem to be a rare event in EOC. KRAS mutations with synchronous TP53 mutations occur predominantly in low-grade mucinous carcinomas, suggesting a specific molecular background of this ovarian cancer type.

Tubular and endothelial chimerism in renal allografts using fluorescence and chromogenic in situ hybridization (FISH, CISH) technology.

The role of endothelial and tubular chimerism in renal allograft adaptation and rejection varies in different studies. We addressed the correlation between different clinico-pathological settings and sex-chromosomal endothelial and/or tubular chimerism in renal allografts. We examined the presence or absence of the X and Y chromosomes by fluorescence and chromogenic in situ hybridization (FISH, CISH) methodology on paraffin embedded kidney biopsies in 16 gender mismatched renal transplants (1 to 12 years post-transplantation). Twelve patients were male, four female. Four groups were selected: (i) Vascular calcineurin inhibitor toxicity without rejection; (ii) T-cell mediated vascular rejection; (iii) antibody mediated rejection; and (iv) C4d-positivity in AB0-incompatible transplants with or without rejection. Twelve non-transplant kidney biopsies (8 female, 4 male) were used as controls. Tubular chimerism was detected more frequently (69%) than endothelial chimerism (12%) in renal transplants. One of 12 control patients had tubular and endothelial chimeric cells (8%). The Y chromosome occurred in 8/12 male recipients (67%) in tubular epithelial cells and in 5/12 male recipients (42%) in endothelial cells. Double X chromosomes were detected in 3/4 female recipients in tubular epithelium. Tubular chimerism occurred more often with endothelial chimerism and capillaritis without correlation with other parameters, such as rejection. Combined Y chromosomal tubular and lymphatic endothelial chimerism correlated with T-cell mediated vascular rejection in two out of three patients (66%). Combined Y chromosomal tubular and peritubular capillary chimerism correlated with antibody mediated C4d+ rejection in one out of two patients (50%). Tubular and/or endothelial chimerism occur frequently in gender mismatched renal allografts and, when combined, this is associated with T-cell mediated rejection.

Next Generation Sequencing of Reactive Stroma and Residual Breast Cancer Cells in Tumor Bed after Neoadjuvant Chemotherapy.

Primary systemic or neoadjuvant chemotherapy of breast cancer has become a standard therapy option in locally advanced or predefined intrinsic subtypes such as triple negative or Her2 positive breast cancer. Neoadjuvant chemotherapy can result in complete pathological response without residual tumor cells (tumor bed) or partial response and non-response with different amounts of reactive stroma and residual tumor cells. The interaction between therapy regimens and tumoral driver mutations have been extensively studied, although the reactive stroma of the tumor bed received less attention. In this study, we characterized the mutational status of residual breast cancer cells and reactive tumor stroma devoid of residual tumor cells in partial or non-responders using next generation sequencing. Twenty-one post-therapeutic breast surgical specimens after neoadjuvant chemotherapy underwent pathogenic driver-mutation screening using microdissected residual breast cancer cells and in reactive stroma adjacent to tumor bed areas. In reactive stroma, no mutations could be validated. In residual breast cancer cells, mutations were detected in sixteen of twenty-one cases (76%). In nine of these twenty-one cases (43%), pathogenic driver mutations (PIK3CA, PTEN, TP53, FN1, PLAG1) were identified. Pathogenic driver-mutations are exclusively restricted to residual carcinoma cells and are absent in reactive stroma independently from intrinsic breast cancer subtypes or tumor stage. These data suggest that the absence of pathogenic mutations in a tumor bed without residual tumor cells may have prognostic implications after neoadjuvant chemotherapy.

VHL mutations and dysregulation of pVHL- and PTEN-controlled pathways in multilocular cystic renal cell carcinoma.

Multilocular cystic renal cell carcinoma is a rare renal cell carcinoma with an excellent prognosis. To clarify the relationship with typical clear cell renal cell carcinoma, we evaluated 15 cases of multilocular cystic renal cell carcinomas diagnosed according to the 2004 WHO classification. Von Hippel Lindau (VHL) gene mutations were determined by whole genome amplification and direct sequencing. Carbonic anhydrase 9 (CAIX), a hypoxia-inducible factor (HIF) target, paired box gene 2 (PAX2), cyclin-dependent kinase inhibitor p27 and glycogen synthase kinase 3-ß (GSK3ß) were immunohistochemically evaluated as members of the VHL protein (pVHL)- and phosphatase and tensin homolog (PTEN)-controlled pathways. VHL mutations were identified in 3 of 12 (25%) tumors. Inactivated GSK3ß, decreased PTEN expression and PAX2 positivity were observed in the vast majority of the multilocular cystic renal cell carcinomas. Strong nuclear staining of p27 was seen in 14 of 15 cases. Compared with multilocular cystic renal cell carcinomas, expression frequencies of PAX2, p-GSK3ß, PTEN and CAIX were similar in a set of low-grade, early-stage clear cell renal cell carcinomas, whereas only 30% had strong p27 positivity. These results are consistent with the hypothesis that multilocular cystic renal cell carcinomas are related at the molecular level with clear cell renal cell carcinomas. Maintenance of a strong subcellular p27 expression in all multilocular cystic renal cell carcinomas analyzed may in part explain the excellent prognosis of these tumor patients.

Tracing Clonal Dynamics Reveals that Two- and Three-dimensional Patient-derived Cell Models Capture Tumor Heterogeneity of Clear Cell Renal Cell Carcinoma.

BACKGROUND: Extensive DNA sequencing has led to an unprecedented view of the diversity of individual genomes and their evolution among patients with clear cell renal cell carcinoma (ccRCC). OBJECTIVE: To understand subclonal architecture and dynamics of patient-derived two-dimensional (2D) and three-dimensional (3D) ccRCC models in vitro, in order to determine whether they mirror ccRCC inter- and intratumor heterogeneity. DESIGN, SETTING, AND PARTICIPANTS: We have established a comprehensive platform of living renal cancer cell models from ccRCC surgical specimens. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We confirmed the concordance of 2D and 3D patient-derived cell (PDC) models with the original tumor tissue in terms of histology, biomarker expression, cancer driver mutations, and copy number alterations. We addressed inter- and intrapatient heterogeneity by analyzing clonal dynamics during serial passaging. RESULTS AND LIMITATIONS: In-depth genetic characterization verified the presence of heterogeneous cell populations, and revealed a high degree of similarity between subclonal compositions of monolayer and organoid cell cultures and the corresponding parental ccRCCs. Clonal dynamics were evident during serial passaging of cells in vitro, suggesting that PDC cultures can offer insights into evolutionary potential and treatment susceptibility of ccRCC subclones in vivo. Proof-of-concept drug profiling using selected ccRCC-targeted therapy agents highlighted patient-specific vulnerabilities in PDC models that could not be anticipated by interrogating commercially available cell lines. CONCLUSIONS: We demonstrate that PDC models mirror inter- and intratumor heterogeneity of ccRCC in vitro. Based on our findings, we envision that the use of these models will advance our understanding of the trajectories that cause genetic diversity and their consequences for treatment on an individual level. PATIENT SUMMARY: In this study, we developed two- and three-dimensional patient-derived models from clear cell renal cell carcinoma (ccRCC) as "mini-tumors in a dish." We show that these cell models retain important features of the human ccRCCs such as the profound tumor heterogeneity, thus highlighting their importance for cancer research and precision medicine.

Loss of VHL and hypoxia provokes PAX2 up-regulation in clear cell renal cell carcinoma.

PURPOSE: The paired box gene 2, PAX2, encodes for a transcription factor that is up-regulated during nephrogenesis and becomes silenced in mature epithelium of the glomeruli, the proximal, and distal tubules. Reactivation of PAX2 has been frequently observed in clear cell renal cell carcinoma (ccRCC), a tumor type characterized by loss of von Hippel-Lindau (VHL) tumor suppressor function. The regulation of PAX2 expression in ccRCC is unknown. EXPERIMENTAL DESIGN: We applied reporter gene assays to investigate PAX2 promoter regulation. Furthermore, PAX2 expression was determined in ccRCC cell lines under normoxic and hypoxic condition in a VHL wild-type and mutated background. PAX2 expression was also assessed in 831 human ccRCC and correlated with hypoxia-inducible factor alpha (HIFalpha) and clinical parameters. RESULTS: Here, we show that both loss of VHL protein (pVHL) function and hypoxia leads to strong PAX2 reexpression. Using luciferase reporter gene assays, no induction was obtained in spite of six hypoxia response element motifs identified in the promoter of PAX2. Comprehensive immunohistochemical analyses showed significant correlations between PAX2, HIF1alpha, and HIF2alpha-target CCND1 expression patterns in ccRCC patients. Notably, PAX2 expression was highly associated with early-stage, well-differentiated ccRCC and, consequently, better clinical outcome (P < 0.0001 each). Additional analyses indicated that PAX2 repressor WT1 and cancer-linked hypomethylation are not important for transcriptional regulation of PAX2 in ccRCC. CONCLUSION: We conclude that in ccRCC, PAX2 reactivation is driven by HIF-dependent mechanisms following pVHL loss.

Clear cell papillary renal cell carcinoma and renal angiomyoadenomatous tumor: two variants of a morphologic, immunohistochemical, and genetic distinct entity of renal cell carcinoma.

Clear cell papillary renal cell carcinoma (ccpRCC) and renal angiomyoadenomatous tumor (RAT) share morphologic similarities with clear cell (ccRCC) and papillary RCC (pRCC). It is a matter of controversy whether their morphologic, immunophenotypic, and molecular features allow the definition of a separate renal carcinoma entity. The aim of our project was to investigate specific renal immunohistochemical biomarkers involved in the hypoxia-inducible factor pathway and mutations in the VHL gene to clarify the relationship between ccpRCC and RAT. We investigated 28 ccpRCC and 9 RAT samples by immunohistochemistry using 25 markers. VHL gene mutations and allele losses were investigated by Sanger sequencing and fluorescence in situ hybridization. Clinical follow-up data were obtained for a subset of the patients. No tumor recurrence or tumor-related death was observed in any of the patients. Immunohistochemistry and molecular analyses led to the reclassification of 3 tumors as ccRCC and TFE3 translocation carcinomas. The immunohistochemical profile of ccpRCC and RAT samples was very similar but not identical, differing from both ccRCC and pRCC. Especially, the parafibromin and hKIM-1 expression exhibited differences in ccpRCC/RAT compared with ccRCC and pRCC. Genetic analysis revealed VHL mutations in 2/27 (7%) and 1/7 (14%) ccpRCC and RAT samples, respectively. Fluorescence in situ hybridization analysis disclosed a 3p loss in 2/20 (10%) ccpRCC samples. ccpRCC and RAT have a specific morphologic and immunohistochemical profile, but they share similarities with the more aggressive renal tumors. On the basis of our results, we regard ccpRCC/RAT as a distinct entity of RCCs.

Effect of MRE11 loss on PARP-inhibitor sensitivity in endometrial cancer in vitro.

AIM OF THE STUDY: To evaluate the frequency of MRE11/RAD50/NBS1 (MRN)-complex loss of protein expression in endometrial cancers (EC) and to determine whether loss of MRE11 renders the cancer cells sensitive to Poly(ADP-ribose) polymerase (PARP)-inhibitory treatment. METHODS: MRN expression was examined in 521 samples of endometrial carcinomas and in 10 cancer cell lines. A putative mutation hotspot in the form of an intronic poly(T) allele in MRE11 was sequenced in selected cases (n = 26). Sensitivity to the PARP-inhibitor, BMN673 was tested in colony formation assays before and after MRE11 silencing using siRNA. Homologous recombination (HR) DNA repair was evaluated by RAD51-foci formation assay upon irradiation and drug treatment. RESULTS: Loss of MRE11 protein was found in 30.7% of EC tumours and significantly associated with loss of RAD50, NBS1 and mismatch repair protein expression. One endometrial cell line showed a markedly reduced MRE11 expression due to a homozygous poly(T) mutation of MRE11, thereby exhibiting an increased sensitivity to BMN673. MRE11 depletion sensitizes MRE11 expressing EC cell lines to the treatment with BMN673. The increased sensitivity to PARP-inhibition correlates with reduced RAD51 foci formation upon ionizing radiation in MRE11-depleted cells. CONCLUSION: Loss of the MRE11 protein predicts sensitivity to PARP-inhibitor sensitivity in vitro, defining it as an additional synthetic lethal gene with PARP. The high incidence of MRE11 loss in ECs can be potentially exploited for PARP-inhibitor therapy. Furthermore, MRE11 protein expression using immunohistochemistry could be investigated as a predictive biomarker for PARP-inhibitor treatment.

KRAS, BRAF, and TP53 deep sequencing for colorectal carcinoma patient diagnostics.

In colorectal carcinoma, KRAS (alias Ki-ras) and BRAF mutations have emerged as predictors of resistance to anti-epidermal growth factor receptor antibody treatment and worse patient outcome, respectively. In this study, we aimed to establish a high-throughput deep sequencing workflow according to 454 pyrosequencing technology to cope with the increasing demand for sequence information at medical institutions. A cohort of 81 patients with known KRAS mutation status detected by Sanger sequencing was chosen for deep sequencing. The workflow allowed us to analyze seven amplicons (one BRAF, two KRAS, and four TP53 exons) of nine patients in parallel in one deep sequencing run. Target amplification and variant calling showed reproducible results with input DNA derived from FFPE tissue that ranged from 0.4 to 50 ng with the use of different targets and multiplex identifiers. Equimolar pooling of each amplicon in a deep sequencing run was necessary to counterbalance differences in patient tissue quality. Five BRAF and 49 TP53 mutations with functional consequences were detected. The lowest mutation frequency detected in a patient tumor population was 5% in TP53 exon 5. This low-frequency mutation was successfully verified in a second PCR and deep sequencing run. In summary, our workflow allows us to process 315 targets a week and provides the quality, flexibility, and speed needed to be integrated as standard procedure for mutational analysis in diagnostics.

Combined mutation of Vhl and Trp53 causes renal cysts and tumours in mice.

The combinations of genetic alterations that cooperate with von Hippel-Lindau (VHL) mutation to cause clear cell renal cell carcinoma (ccRCC) remain poorly understood. We show that the TP53 tumour suppressor gene is mutated in approximately 9% of human ccRCCs. Combined deletion of Vhl and Trp53 in primary mouse embryo fibroblasts causes proliferative dysregulation and high rates of aneuploidy. Deletion of these genes in the epithelium of the kidney induces the formation of simple cysts, atypical cysts and neoplasms, and deletion in the epithelia of the genital urinary tract leads to dysplasia and tumour formation. Kidney cysts display a reduced frequency of primary cilia and atypical cysts and neoplasms exhibit a pro-proliferative signature including activation of mTORC1 and high expression of Myc, mimicking several cellular and molecular alterations seen in human ccRCC and its precursor lesions. As the majority of ccRCC is associated with functional inactivation of VHL, our findings suggest that for a subset of ccRCC, loss of p53 function represents a critical event in tumour development.

Whole genome and transcriptome amplification: practicable tools for sustainable tissue biobanking?

The use of whole genome amplification (WGA) and whole transcriptome amplification (WTA) techniques enables the enrichment of DNA and RNA from very small amounts of tissue. Here, we tested the suitability of WGA and WTA for tumor tissue biobanking. DNA and RNA from 13 standardized and seven non-standardized frozen and 12 formalin-fixed, paraffin-embedded (FFPE) clear cell renal cell carcinoma specimens (>9 years old) served to test the robustness of the WGA and WTA products by reidentifying von Hippel-Lindau (VHL) gene mutations known to exist in these samples. The enrichment of DNA and RNA from frozen tissue was up to 1,291-fold and 423-fold, respectively. The sizes and yields (10- to 73-fold) of the amplified DNA obtained from the 12 FFPE samples were generally lower. The quality of the RNA from the FFPE samples was too low to reliably perform WTA. Our results demonstrate that frozen tumor tissue is very suitable for WGA and WTA. All 20 VHL mutations were verified with WGA. Notably, we were able to show that 18 of the 20 (90 %) VHL mutations are also transcribed. In FFPE tumor tissue, 8 of 12 cases (67 %) showed the expected mutations after the first WGA. Accurate WTA with FFPE material is sophisticated and strongly depends on the modification and degradation status of the fixed tissue. We conclude that for sustainable tissue biobanking, the use of WGA and WTA is a unique opportunity to provide researchers with sufficient amounts of nucleic acids, preferably from limited frozen tissue material.

Characterization of periostin isoform pattern in non-small cell lung cancer.

INTRODUCTION: The extracellular matrix N-glycoprotein periostin (OSF-2, POSTN) is a major constituent of the desmoplastic stroma around solid tumors. It promotes tumor invasion and metastasis via epithelial-mesenchymal transition (EMT). In this study we investigated periostin expression at both RNA and protein level as well as the expression pattern of its splice isoforms in non-small cell lung cancer (NSCLC). METHODS: Thirty fresh frozen and corresponding formalin-fixed NSCLC tissues (adeno- and squamous cell carcinoma subtype, each n=15) and their matched non-neoplastic tissues were investigated. Periostin mRNA levels were analyzed by quantitative RT-PCR. The EMT-markers periostin and vimentin were analyzed by immunohistochemistry. Laser capture microdissection allowed for analysis of periostin expression in tumor epithelia and stroma, separately. Isoform patterns were investigated by isoform-specific PCR following sequencing in NSCLC, fetal and adult normal lung tissue. RESULTS: The qRT-PCR analysis showed periostin mRNA up-regulation in NSCLC tissue in relation to normal lung, with significantly higher levels in the adeno-compared to the squamous cell subtype (p<0.05). However, protein levels in both tumor epithelia and stroma correlated with squamous cell carcinoma (p<0.001) and larger tumor size (p<0.05). Further, periostin tumor epithelia expression, correlated with higher tumor grade (p<0.05). Sequence analysis detected eight periostin isoforms in fetal lung, but only five in both NSCLC and matched normal lung tissue. Among the eight isoforms, four are new and were labelled 5, 7, 8 and 9. The exclusive presence of isoforms 1 and 9 in fetal tissue suggests splice-specific regulation during lung embryogenesis. Finally, laser capture microdissection demonstrated that both tumor epithelia and stromal cells can be a source of periostin production in NSCLC. CONCLUSIONS: This study represents the first analysis of periostin isoform expression patterns in NSCLC and a characterization of periostin expression in cancer versus stromal cells at both RNA and protein level.

Predictive value of the MGMT promoter methylation status in metastatic melanoma patients receiving first-line temozolomide plus bevacizumab in the trial SAKK 50/07.

The O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation status is a predictive parameter for the response of malignant gliomas to alkylating agents such as temozolomide. First clinical trials with temozolomide plus bevacizumab therapy in metastatic melanoma patients are ongoing, although the predictive value of the MGMT promoter methylation status in this setting remains unclear. We assessed MGMT promoter methylation in formalin-fixed, primary tumor tissue of metastatic melanoma patients treated with first-line temozolomide and bevacizumab from the trial SAKK 50/07 by methylation-specific polymerase chain reaction. In addition, the MGMT expression levels were also analyzed by MGMT immunohistochemistry. Eleven of 42 primary melanomas (26%) revealed a methylated MGMT promoter. Promoter methylation was significantly associated with response rates CR + PR versus SD + PD according to RECIST (response evaluation criteria in solid tumors) (p<0.05) with a trend to prolonged median progression-free survival (8.1 versus 3.4 months, p>0.05). Immunohistochemically different protein expression patterns with heterogeneous and homogeneous nuclear MGMT expression were identified. Negative MGMT expression levels were associated with overall disease stabilization CR+PR+SD versus PD (p=0.05). There was only a poor correlation between MGMT methylation and lack of MGMT expression. A significant proportion of melanomas have a methylated MGMT promoter. The MGMT promoter methylation status may be a promising predictive marker for temozolomide therapy in metastatic melanoma patients. Larger sample sizes may help to validate significant differences in survival type endpoints.

Identification and functional characterization of pVHL-dependent cell surface proteins in renal cell carcinoma.

The identification of cell surface accessible biomarkers enabling diagnosis, disease monitoring, and treatment of renal cell carcinoma (RCC) is as challenging as the biology and progression of RCC is unpredictable. A hallmark of most RCC is the loss-of-function of the von Hippel-Lindau (pVHL) protein by mutation of its gene (VHL). Using the cell surface capturing (CSC) technology, we screened and identified cell surface N-glycoproteins in pVHL-negative and positive 786-O cells. One hundred six cell surface N-glycoproteins were identified. Stable isotope labeling with amino acids in cell culture-based quantification of the CSC screen revealed 23 N-glycoproteins whose abundance seemed to change in a pVHL-dependent manner. Targeted validation experiments using transcriptional profiling of primary RCC samples revealed that nine glycoproteins, including CD10 and AXL, could be directly linked to pVHL-mediated transcriptional regulation. Subsequent human tumor tissue analysis of these cell surface candidate markers showed a correlation between epithelial AXL expression and aggressive tumor phenotype, indicating that pVHL-dependent regulation of glycoproteins may influence the biologic behavior of RCC. Functional characterization of the metalloprotease CD10 in cell invasion assays demonstrated a diminished penetrating behavior of pVHL-negative 786-O cells on treatment with the CD10-specific inhibitor thiorphan. Our proteomic surfaceome screening approach in combination with transcriptional profiling and functional validation suggests pVHL-dependent cell surface glycoproteins as potential diagnostic markers for therapeutic targeting and RCC patient monitoring.

VHL gene mutations and their effects on hypoxia inducible factor HIFα: identification of potential driver and passenger mutations.

Mutations of the von Hippel-Lindau (VHL) gene are frequent in clear cell renal cell carcinomas (ccRCC). Nonsense and frameshift mutations abrogate the function of the VHL protein (pVHL), whereas missense mutations can have different effects. To identify those missense mutations with functional consequences, we sequenced VHL in 256 sporadic ccRCC and identified 187 different VHL mutations of which 65 were missense mutations. Location and destabilizing effects of VHL missense mutations were determined in silico. The majority of the thermodynamically destabilizing missense mutations were located in exon 1 in the core of pVHL, whereas protein surface mutations in exon 3 affected the interaction domains of elongin B and C. Their impact on pVHL's functionality was further investigated in vitro by stably reintroducing VHL missense mutations into a VHL null cell line and by monitoring the green fluorescent protein (GFP) signals after the transfection of a hypoxia inducible factor (HIF)α-GFP expression vector. pVHL's functionality ranged from no effect to complete HIF stabilization. Interestingly, Asn78Ser, Asp121Tyr, and Val130Phe selectively influenced HIF1α and HIF2α degradation. In summary, we obtained three different groups of missense mutations: one with severe destabilization of pVHL; a second without destabilizing effects on pVHL but relevance for the interaction with HIFα, elongin B, and elongin C; and a third with pVHL functions comparable with wild type. We therefore conclude that the specific impact of missense mutations may help to distinguish between driver and passenger mutations and may explain responses of ccRCC patients to HIF-targeted therapies.

VHL-gene deletion in single renal tubular epithelial cells and renal tubular cysts: further evidence for a cyst-dependent progression pathway of clear cell renal carcinoma in von Hippel-Lindau disease.

Inheritance of a mutant allele of the von Hippel-Lindau tumor suppressor gene predisposes affected individuals to develop renal cysts and clear cell renal cell carcinoma. Von Hippel-Lindau gene inactivation in single renal tubular cells has indirectly been showed by immunohistochemical staining for the hypoxia-inducible factor alpha target gene product carbonic anhydrase IX. In this study we were able to show von Hippel-Lindau gene deletion in carbonic anhydrase IX positive nonneoplastic renal tubular cells, in epithelial cells lining renal cysts and in a clear cell renal cell carcinoma of a von Hippel-Lindau patient. This was carried out by means of laser confocal microscopy and immunohistochemistry in combination with fluorescence in situ hybridization. Carbonic anhydrase IX negative normal renal tubular cells carried no von Hippel-Lindau gene deletion. Furthermore, recent studies have indicated that the von Hippel-Lindau gene product is necessary for the maintenance of primary cilia stability in renal epithelial cells and that disruption of the cilia structure by von Hippel-Lindau gene inactivation induces renal cyst formation. In our study, we show a significant shortening of primary cilia in epithelial cells lining renal cysts, whereas, single tubular cells with a von Hippel-Lindau gene deletion display to a far lesser extent signs of cilia shortening. Our in vivo results support a model in which renal cysts represent precursor lesions for clear cell renal cell carcinoma and arise from single renal tubular epithelial cells owing to von Hippel-Lindau gene deletion.

Stromal complement receptor CD21/35 facilitates lymphoid prion colonization and pathogenesis.

We have studied the role of CD21/35, which bind derivatives of complement factors C3 and C4, in extraneural prion replication and neuroinvasion. Upon administration of small prion inocula, CD21/35(-/-) mice experienced lower attack rates and delayed disease over both wild-type (WT) mice and mice with combined C3 and C4 deficiencies. Early after inoculation, CD21/35(-/-) spleens were devoid of infectivity. Reciprocal adoptive bone marrow transfers between WT and CD21/35(-/-) mice revealed that protection from prion infection resulted from ablation of stromal, but not hemopoietic, CD21/35. Further adoptive transfer experiments between WT mice and mice devoid of both the cellular prion protein PrP(C) and CD21/35 showed that splenic retention of inoculum depended on stromal CD21/35 expression. Because both PrP(C) and CD21/35 are highly expressed on follicular dendritic cells, CD21/35 appears to be involved in targeting prions to follicular dendritic cells and expediting neuroinvasion following peripheral exposure to prions.