Expression of KRT7 and WT1 differentiates precursor lesions of Wilms' tumours from those of papillary renal cell tumours and mucinous tubular and spindle cell carcinomas.

Wilms' tumours (WT) and adult papillary renal cell tumours (pRCT) are associated with precursor lesions of embryonic origin. The aim of this study was to analyse the expression of WT1, KRT7, KRT8, KRT18 and KRT19 genes by immunohistochemistry in 74 precursor lesions associated with WTs, pRCTs and mucinous tubular and spindle cell carcinomas (MTSCC). All precursor lesions associated with Wilms' tumours were positive for WT1, whereas all precursor lesions in pRCT and MTSCC-bearing kidneys were negative. None of the WT-associated lesions were positive for KRT7, but 69-80% of lesions associated with pRCTs and MTSCCs were positive for KRT7. KRT8, KRT18 and KRT19 were found to be expressed in 80-100% of all types of precursor lesions. Our findings indicate that the precursor lesions analysed in this study are committed in an early stage of cellular differentiation to the development of either Wilms' tumours or papillary RCTs and MTSCCs.

Genomic profiling of papillary renal cell tumours identifies small regions of DNA alterations: a possible role of HNF1B in tumour development.

AIMS: Papillary renal cell tumours (RCT) are characterized by specific trisomies. The aim of this study was to identify small regions of duplication marking putative tumour genes. METHODS AND RESULTS: Full-tiling path bacterial artificial chromosome (BAC) array hybridization of 20 papillary RCTs confirmed the duplication of chromosomes 7 and 17 and also displayed smaller regions of gains/amplifications of 1.3-13.1 Mb in size. Detailed analysis showed a microamplification of BAC clones containing the MET at the 7q31.2 and also amplification of a DNA segment harbouring the transcription factor hepatocyte nuclear factor 1 beta (HNF1B) at chromosome 17q12. Nuclear expression of HNF1B protein was detected in 38 of 67 papillary RCTs, in five of five mucinous tubular and spindle cell carcinomas (MTSCC) and five of five metanephric adenomas by immunohistochemistry. Moreover, nine nephrogenic rests containing tubular differentiated structures and all 14 and five precursor lesions associated with papillary RCTs and MTSCCs, respectively, showed strong nuclear positivity when compared to the expression level in proximal tubules of the corresponding normal kidney. CONCLUSIONS: Our findings indicate a role of HNF1B in association with the high frequency of chromosome 17q duplication in the development of papillary RCTs and MTSCCs as well as in their precursor lesions.

High-resolution array CGH of metanephric adenomas: lack of DNA copy number changes.

AIMS: Previous karyotyping and fluorescence in situ hybridization analysis of metanephric adenomas (MAs) has yielded controversial data. The aim of this study was to detect small genomic alterations, if any, specific to MAs by applying high-resolution oligoarrays. METHODS AND RESULTS: DNA extracted from paraffin blocks of six metanephric adenomas was hybridized onto Agilent oligoarrays with approximately 43,000 in situ synthesized 60-mer oligonucleotide probes that span coding and non-coding sequences with an average spatial resolution of approximately 35 kb. None of the metanephric adenomas showed DNA copy number changes. To confirm our results, DNA extracted from the paraffin block of a chromophobe renal cell carcinoma (RCC) was simultaneously hybridized to one of the four arrays on the same slides as an internal control. The chromophobe RCC showed loss of several chromosomes but no alteration was seen in MAs. We have confirmed the negative results by dye-swap and sex mismatch hybridization experiments. CONCLUSIONS: Our high-resolution oligoarray analysis indicates that metanephric adenomas lack DNA copy number alterations. This finding may help to differentiate between metanephric adenomas from Wilms' tumour and papillary renal cell adenoma with overlapping phenotype.

Inflammatory protein serum amyloid A1 marks a subset of conventional renal cell carcinomas with fatal outcome.

BACKGROUND: Conventional renal cell carcinoma (RCC) is the most common renal cancer. As the metastatic conventional RCC is practically incurable, there is a need for markers to estimate the tumour aggressiveness. OBJECTIVE: To identify and characterise new marker(s) associated with the poor prognosis of conventional RCC. DESIGN, SETTING, AND PARTICIPANTS: RNA from 24 conventional RCCs was analysed for global gene expression by Affymetrix U133 Plus 2.0 arrays. Tissue microarrays containing 224 renal tumours including 87 conventional RCCs were used for immunohistochemistry. Cell lines HD2, HD48, HA344 and HA465 established in our laboratory were used for invasion assay and zymography. MEASUREMENTS: Serum amyloid A 1 (SAA1) was found to be upregulated in conventional RCCs and it has been analysed by quantitative RT-PCR and immunohistochemistry on TMAs to establish the correlation between SAA1 protein expression and patient survival by uni and multivariate analysis. The effect of SAA1 on tumour cell behaviour in vitro has also been examined by invasion assay and zymography. RESULTS AND LIMITATIONS: SAA1 RNA is expressed in conventional RCC samples of patients with poor prognosis. Immunohistochemistry of 72 conventional RCCs with a 5 yr follow up showed a correlation between SAA1 expression and the clinical outcome of disease. Stimulation of conventional RCC cell lines with recombinant SAA1 increased the expression of metalloproteinase (MMP)-9 and the invasive potential of tumour cells. Limitation of the study is a relatively small number (72) of patients having follow up. CONCLUSION: SAA1 seems to be a useful marker to estimate the prognosis of conventional RCCs.

Three genetic developmental stages of papillary renal cell tumors: duplication of chromosome 1q marks fatal progression.

Papillary renal cell tumors (RCT) make up a cytomorphologically and biologically heterogeneous group of kidney cancers including renal cell adenomas (RCA) and renal cell carcinomas (RCC). To find genetic markers landmarking the tumor progression, we have evaluated the genetic alterations obtained by karyotyping, chromosomal and array-CGH and compared with the cytological characteristics and biological behavior of 60 papillary RCTs. Based on the genetic and clinical data, we have separated 3 groups of tumors and proposed 3 genetically defined developmental stages of papillary RCTs. Papillary RCAs are characterized by combined trisomy of chromosomes 7 and 17, whereas papillary RCCs displayed additional trisomies of 3q, 8q, 12q, 16q and 20q. In addition to the genetic changes occurring in the second group, the third group of tumors was characterized by 1q gain and 6q, 8p, 9p and 14q losses. Kaplan-Meier analysis revealed a significant association between chromosome 1q gain and deadly outcome of the disease. The cytomorphological variation and size of tumors in the second and third groups did not correlate with the clinical outcome. Therefore, we suggest that our genetic classification system landmarking papillary RCA, papillary RCC without and with progression offer a better system to characterize the tumor biology of clinical significance than a cellular/morphological classification.