Matteo Montani

pVHL and GSK3|[beta]| are components of a primary cilium-maintenance signalling network

Defects in the structure or function of the primary cilium, an antennae-like structure whose functional integrity has been linked to the suppression of uncontrolled kidney epithelial cell proliferation, are a common feature of genetic disorders characterized by kidney cysts. However, the mechanisms by which primary cilia are maintained remain poorly defined. von Hippel-Lindau (VHL) disease is characterized by the development of premalignant renal cysts and arises because of functional inactivation of the VHL tumour suppressor gene product, pVHL. Here, we show that pVHL and glycogen synthase kinase (GSK)3β are key components of an interlinked signalling pathway that maintains the primary cilium. Although inactivation of either pVHL or GSK3β alone did not affect cilia maintenance, their combined inactivation leads to loss of cilia. In VHL patients, GSK3β is subjected to inhibitory phosphorylation in renal cysts, but not in early VHL mutant lesions, and these cysts exhibit reduced frequencies of primary cilia. We propose that pVHL and GSK3β function together in a ciliary-maintenance signalling network, disruption of which enhances the vulnerability of cells to lose their cilia, thereby promoting cyst formation.

pVHL and PTEN tumour suppressor proteins cooperatively suppress kidney cyst formation

In patients with von Hippel–Lindau (VHL) disease, renal cysts and clear cell renal cell carcinoma (ccRCC) arise from renal tubular epithelial cells containing biallelic inactivation of the VHL tumour suppressor gene. However, it is presumed that formation of renal cysts and their conversion to ccRCC involve additional genetic changes at other loci. Here, we show that cystic lesions in the kidneys of patients with VHL disease also demonstrate activation of the phosphatidylinositol‐3‐kinase (PI3K) pathway. Strikingly, combined conditional inactivation of Vhlh and the Pten tumour suppressor gene, which normally antagonises PI3K signalling, in the mouse kidney, elicits cyst formation after short latency, whereas inactivation of either tumour suppressor gene alone failed to produce such a phenotype. Interestingly, cells lining these cysts frequently lack a primary cilium, a microtubule‐based cellular antenna important for suppression of uncontrolled kidney epithelial cell proliferation and cyst formation. Our results support a model in which the PTEN tumour suppressor protein cooperates with pVHL to suppress cyst development in the kidney.

Molecular imaging of atherosclerotic plaques using a human antibody against the extra-domain B of fibronectin

Current imaging modalities of human atherosclerosis, such as angiography, ultrasound, and computed tomography, visualize plaque morphology. However, methods that provide insight into plaque biology using molecular tools are still insufficient. The extra-domain B (ED-B) is inserted into the fibronectin molecule by alternative splicing during angiogenesis and tissue remodeling but is virtually undetectable in normal adult tissues. Angiogenesis and tissue repair are also hallmarks of advanced plaques. For imaging atherosclerotic plaques, the human antibody L19 (specific against ED-B) and a negative control antibody were labeled with radioiodine or infrared fluorophores and injected intravenously into atherosclerotic apolipoprotein E–null (ApoE−/−) or normal wild-type mice. Aortas isolated 4 hours, 24 hours, and 3 days after injection exhibited a selective and stable uptake of L19 when using radiographic or fluorescent imaging. L19 binding was confined to the plaques as assessed by fat staining. Comparisons between fat staining and autoradiographies 24 hours after 125I-labeled L19 revealed a significant correlation (r=0.89; P<0.0001). Minimal antibody uptake was observed in normal vessels from wild-type mice receiving the L19 antibody and in atherosclerotic vessels from ApoE−/− mice receiving the negative control antibody. Immunohistochemical studies revealed increased expression of ED-B not only in murine but also in human plaques, in which it was found predominantly around vasa vasorum and plaque matrix. In summary, we demonstrate selective targeting of atheromas in mice using the human antibody to the ED-B domain of fibronectin. Thus, our findings may set the stage for antibody-based molecular imaging of atherosclerotic plaques in the intact organism.

KPNA2 Expression Is an Independent Adverse Predictor of Biochemical Recurrence after Radical Prostatectomy

Purpose: To analyze rates of expression of karyopherin alpha 2 (KPNA2) in different prostate tissues and to evaluate the prognostic properties for patients with primary prostate cancer. Experimental Design: Tissue microarrays (TMA) contained 798 formalin-fixed, paraffin-embedded prostate tissue cores from two different institutes of pathology. TMAs were stained immunohistochemically for KPNA2 and NBS1. SiRNA technologies were used to inhibit KPNA2 expression in vitro, and the effect of this inhibition on cellular viability was determined. Efficiency of knockdown experiments was determined by Western blot analysis. Results: KPNA2 expression was significantly upregulated in carcinomas of the prostate, especially in metastatic and castration-resistant prostate cancer samples. Positive nuclear KPNA2 immunoreactivity was identified as a novel predictor of biochemical recurrence after radical prostatectomy (n = 348), and was independent of the well-established predictive factors preoperative PSA value, Gleason score, tumor stage, and surgical margin status. These results were validated by analyzing a second and independent prostate cancer cohort (n = 330). Further, in vitro experiments showed that the cell proliferation and viability of PC3 cells was significantly reduced when KPNA2 expression was inhibited. KPNA2 knockdown did not induce PARP cleavage as marker for apoptosis. No significantly increased sub-G1 fraction could be found by FACS analysis. Conclusions: KPNA2 is a novel independent prognostic marker for disease progression after radical prostatectomy. This allows to identify patients who need more aggressive treatment. It can moreover be speculated that patients not suited for surveillance regimens might be identified at initial biopsy by a positive KPNA2 immunohistochemistry. Clin Cancer Res; 17(5); 1111–21. ©2011 AACR.

Mining Tissue Microarray Data to Uncover Combinations of Biomarker Expression Patterns that Improve Intermediate Staging and Grading of Clear Cell Renal Cell Cancer

Purpose: Tumor stage and nuclear grade are the most important prognostic parameters of clear cell renal cell carcinoma (ccRCC). The progression risk of ccRCC remains difficult to predict particularly for tumors with organ-confined stage and intermediate differentiation grade. Elucidating molecular pathways deregulated in ccRCC may point to novel prognostic parameters that facilitate planning of therapeutic approaches. Experimental Design: Using tissue microarrays, expression patterns of 15 different proteins were evaluated in over 800 ccRCC patients to analyze pathways reported to be physiologically controlled by the tumor suppressors von Hippel-Lindau protein and phosphatase and tensin homologue (PTEN). Tumor staging and grading were improved by performing variable selection using Cox regression and a recursive bootstrap elimination scheme. Results: Patients with pT2 and pT3 tumors that were p27 and CAIX positive had a better outcome than those with all remaining marker combinations. A prolonged survival among patients with intermediate grade (grade 2) correlated with both nuclear p27 and cytoplasmic PTEN expression, as well as with inactive, nonphosphorylated ribosomal protein S6. By applying graphical log-linear modeling for over 700 ccRCC for which the molecular parameters were available, only a weak conditional dependence existed between the expression of p27, PTEN, CAIX, and p-S6, suggesting that the dysregulation of several independent pathways are crucial for tumor progression. Conclusions: The use of recursive bootstrap elimination, as well as graphical log-linear modeling for comprehensive tissue microarray (TMA) data analysis allows the unraveling of complex molecular contexts and may improve predictive evaluations for patients with advanced renal cancer. Clin Cancer Res; 16(1); 88–98

FOXA1 Promotes Tumor Progression in Prostate Cancer and Represents a Novel Hallmark of Castration-Resistant Prostate Cancer

Forkhead box protein A1 (FOXA1) modulates the transactivation of steroid hormone receptors and thus may influence tumor growth and hormone responsiveness in prostate cancer. We therefore investigated the correlation of FOXA1 expression with clinical parameters, prostate-specific antigen (PSA) relapse-free survival, and hormone receptor expression in a large cohort of prostate cancer patients at different disease stages. FOXA1 expression did not differ significantly between benign glands from the peripheral zone and primary peripheral zone prostate carcinomas. However, FOXA1 was overexpressed in metastases and particularly in castration-resistant cases, but was expressed at lower levels in both normal and neoplastic transitional zone tissues. FOXA1 levels correlated with higher pT stages and Gleason scores, as well as with androgen (AR) and estrogen receptor expression. Moreover, FOXA1 overexpression was associated with faster biochemical disease progression, which was pronounced in patients with low AR levels. Finally, siRNA-based knockdown of FOXA1 induced decreased cell proliferation and migration. Moreover, in vitro tumorigenicity was inducible by ARs only in the presence of FOXA1, substantiating a functional cooperation between FOXA1 and AR. In conclusion, FOXA1 expression is associated with tumor progression, dedifferentiation of prostate cancer cells, and poorer prognosis, as well as with cellular proliferation and migration and with AR signaling. These findings suggest FOXA1 overexpression as a novel mechanism inducing castration resistance in prostate cancer.

IGFII and MIB1 immunohistochemistry is helpful for the differentiation of benign from malignant adrenocortical tumours

Aims:  The differentiation of adrenocortical carcinomas from adenomas may be difficult based on morphology alone. Differential expression of insulin‐like growth factor (IGF) II and cyclin‐dependent kinase (CDK) 4 has recently been described in these tumours. The aim of this study was to investigate the diagnostic usefulness of these markers immunohistochemically.

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 α 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.

Pancreatic endocrine tumors are a rare manifestation of the neurofibromatosis type 1 phenotype: molecular analysis of a malignant insulinoma in a NF-1 patient.

The tumorigenesis of sporadic endocrine tumors is still not fully understood. It is well known that patients with von Recklinghausen syndrome (NF-1) (OMIM 162200) carrying NF1 germline mutations are predisposed to endocrine tumors including pheochromocytomas and duodenal somatostatinomas. It is unclear, however, whether the rarely reported occurrence of pancreatic insulinomas in NF-1 patients represents a coincidental finding or whether insulinomas are a rare manifestation of the NF-1 syndrome. To determine the potential association between the NF-1 syndrome and pancreatic endocrine tumors, we analyzed a NF-1 patient with a well-differentiated pancreatic endocrine carcinoma for NF1 mutation, allelic loss of the NF1 gene and its expression in peripheral blood and tumor cells. The germline mutation c. 499 del TGTT known in the family was confirmed by polymerase chain reaction (PCR) and direct sequencing of exon 4 in DNA extracted from peripheral blood. Loss of heterozygosity (LOH) analysis of the NF1 gene was carried out using 3 intragenic microsatellite markers on 17q11.2. RNA expression was examined by reverse transcription and a consecutive PCR spanning intron 3 of the NF1 gene including the mutated site in exon 4. Immunohistochemistry was used to analyze NF-1 protein expression. Mutation analysis of peripheral blood leukocytes confirmed the 4 base pair deletion in exon 4 starting at codon 167 (499 del TGTT). LOH analysis of tumor tissue revealed retention of both NF1 alleles. While reverse transcriptase-PCR of peripheral blood showed bi-allelic expression of both the wild-type NF1 and the mutated form, reverse transcriptase-PCR of tumor extracts demonstrated expression of the mutated but not the wild-type NF1 allele. Additionally, neurofibromin, the NF1 gene product, was absent in the tumor tissue of the NF-1 patient. These results show that the wild-type NF1 transcrips and protein are reduced, in the reported insulinoma, supposedly by epigenetic mechanisms. This provides strong evidence that there is a relationship between von Recklinghausen disease and the patients insulinoma. In this line, insulinomas may be viewed as a rare manifestation of the NF-1 syndrome. Furthermore, the NF1 gene must be considered as a candidate tumor suppressor gene for sporadic insulinomas and probably other pancreatic endocrine tumors.

Profiling Gastrin-Releasing Peptide Receptor in Prostate Tissues: Clinical Implications and Molecular Correlates

The gastrin‐releasing peptide receptor (GRPR) has emerged as an attractive target for both therapeutic and diagnostic appliances, but has only insufficiently been characterized in the human prostate so far. The aim of this study is to profile GRPR in a large cohort and correlate it with clinicopathologic and molecular parameters.