Genomic imbalances in 61 renal cancers from the proximal tubulus detected by comparative genomic hybridization

Modeling Neoplastic Growth in Renal Cell Carcinoma and Polycystic Kidney Disease

Renal cell carcinoma (RCC) and autosomal dominant polycystic kidney disease (ADPKD) share several characteristics, including neoplastic cell growth, kidney cysts, and limited therapeutics. As well, both exhibit impaired vasculature and compensatory VEGF activation of angiogenesis. The PI3K/AKT/mTOR and Ras/Raf/ERK pathways play important roles in regulating cystic and tumor cell proliferation and growth. Both RCC and ADPKD result in hypoxia, where HIF-α signaling is activated in response to oxygen deprivation. Primary cilia and altered cell metabolism may play a role in disease progression. Non-coding RNAs may regulate RCC carcinogenesis and ADPKD through their varied effects. Drosophila exhibits remarkable conservation of the pathways involved in RCC and ADPKD. Here, we review the progress towards understanding disease mechanisms, partially overlapping cellular and molecular dysfunctions in RCC and ADPKD and reflect on the potential for the agile Drosophila genetic model to accelerate discovery science, address unresolved mechanistic aspects of these diseases, and perform rapid pharmacological screens.

Chromosome 17p13 deletion is associated with an aggressive tumor phenotype in clear cell renal cell carcinoma

Background

Deletions of 17p13 recurrently occur in renal cell carcinoma (RCC) but their prognostic role seems to be uncertain.

Methods

To determine prevalence, relationship with tumor phenotype, and patient prognosis, a tissue microarray containing samples from 1809 RCCs was evaluated using dual labeling fluorescence in situ hybridization (FISH) with 17p13 and chromosome 17 centromere probes.

Results

A 17p13 deletion was found in 72 of 1429 interpretable tumors. The frequency of 17p13 deletions varied greatly between RCC subtypes and was highest in chromophobe RCC (24/72; 33.3%). 17p13 deletions were also found in 35 (3.7%) of 946 clear cell RCC, 9 (4.3%) of 208 papillary RCC, 1 of 121 oncocytomas (0.8%), as well as in several rare cases of comprising 1 of 7 Xp11.2 translocation cancers, 1 of 3 collecting duct carcinomas, and 1 of 20 not otherwise specified (NOS) carcinomas. In clear cell carcinomas, 17p13 deletions revealed a strong and consistent association with higher Fuhrman, ISUP, and Thoenes grade (p < 0.0001 each), and linked to advanced tumor stage (p = 0.0168), large tumor diameter (p = 0.0004), distant metastases (p = 0.0077), cancer-specific survival (p = 0.0391), and recurrence-free survival (p = 0.0072). In multivariate analysis, 17p13 deletions showed in clear cell RCC a dependent prognostic role for established clinical-pathological parameters.

Conclusion

17p13 deletions have a dual role in RCC. They are associated with disease progression in clear cell RCC and possibly other subtypes and they are linked to the development of chromophobe RCC—a subtype with a particularly favorable prognosis.

8p deletions in renal cell carcinoma are associated with unfavorable tumor features and poor overall survival

BACKGROUND AND METHODS

8p deletions are common in renal cell carcinoma. To study their prognostic impact and association with kidney cancer phenotype, a tissue microarray with 1,809 cancers was analyzed by fluorescence in situ hybridization for 8p21 copy numbers.

RESULTS

One thousand four hundred and seventy four interpretable tumors showed substantial differences between renal cancer subtypes. That 8p deletion was only seen in 1 (0.5%) of 216 papillary carcinomas underscores the biologic uniqueness of papillary kidney cancer, which is also defined by a highly distinct morphology. 8p deletions were found in 13.2% of 976 clear cell carcinomas, 7.8% of 77 chromophobe carcinomas, 0.8% of 119 oncocytomas, but also in several rare tumor entities including 1 of 4 collecting duct cancers, 1 of 3 multilocular cystic clear cell renal cell neoplasm of low malignancy, 2 of 10 Xp11.2 translocation cancers, 3 of 18 not otherwise specified carcinomas, and 1 analyzed medullary carcinoma. In clear cell carcinomas, 8p deletions were significantly associated with higher International Society of Urologic Pathologists (ISUP) grading (P = 0.0014), Fuhrman (P = 0.0003) and Thoenes grade (P = 0.0033), advanced tumor stage (P = 0.0002), large tumor diameter (P = 0.0019), distant metastases (P = 0.0183), overall survival (P = 0.0394), and recurrence free survival (P < 0.0001). In multivariate analysis, the prognostic role of 8p deletions was not independent of established clinic-pathological parameters. In conclusion, 8p deletions are strongly linked to tumor aggressiveness in clear cell kidney cancer.

CONCLUSIONS

Because 8p deletions are easy to measure by fluorescence in situ hybridization, 8p deletion assessment, most likely in combination with other parameters, may have a role in future prognosis assessment in clear cell kidney cancer.

A genomic algorithm for the molecular classification of common renal cortical neoplasms: development and validation

PURPOSE

Accurate discrimination of benign oncocytoma and malignant renal cell carcinoma is useful for planning appropriate treatment strategies for patients with renal masses. Classification of renal neoplasms solely based on histopathology can be challenging, especially the distinction between chromophobe renal cell carcinoma and oncocytoma. In this study we develop and validate an algorithm based on genomic alterations for the classification of common renal neoplasms.

MATERIALS AND METHODS

Using TCGA renal cell carcinoma copy number profiles and the published literature, a classification algorithm was developed and scoring criteria were established for the presence of each genomic marker. As validation, 191 surgically resected formalin fixed paraffin embedded renal neoplasms were blindly submitted to targeted array comparative genomic hybridization and classified according to the algorithm. CCND1 rearrangement was assessed by fluorescence in situ hybridization.

RESULTS

The optimal classification algorithm comprised 15 genomic markers, and involved loss of VHL, 3p21 and 8p, and chromosomes 1, 2, 6, 10 and 17, and gain of 5qter, 16p, 17q and 20q, and chromosomes 3, 7 and 12. On histological rereview (leading to the exclusion of 3 specimens) and using histology as the gold standard, 58 of 62 (93%) clear cell, 51 of 56 (91%) papillary and 33 of 34 (97%) chromophobe renal cell carcinomas were classified correctly. Of the 36 oncocytoma specimens 33 were classified as oncocytoma (17 by array comparative genomic hybridization and 10 by array comparative genomic hybridization plus fluorescence in situ hybridization) or benign (6). Overall 93% diagnostic sensitivity and 97% specificity were achieved.

CONCLUSIONS

In a clinical diagnostic setting the implementation of genome based molecular classification could serve as an ancillary assay to assist in the histological classification of common renal neoplasms.

Subtyping of renal cortical neoplasms in fine needle aspiration biopsies using a decision tree based on genomic alterations detected by fluorescence in situ hybridization

OBJECTIVES

To improve the overall accuracy of diagnosis in needle biopsies of renal masses, especially small renal masses (SRMs), using fluorescence in situ hybridization (FISH), and to develop a renal cortical neoplasm classification decision tree based on genomic alterations detected by FISH.

PATIENTS AND METHODS

Ex vivo fine needle aspiration biopsies of 122 resected renal cortical neoplasms were subjected to FISH using a series of seven-probe sets to assess gain or loss of 10 chromosomes and rearrangement of the 11q13 locus. Using specimen (nephrectomy)-histology as the 'gold standard', a genomic aberration-based decision tree was generated to classify specimens. The diagnostic potential of the decision tree was assessed by comparing the FISH-based classification and biopsy histology with specimen histology.

RESULTS

Of the 114 biopsies diagnostic by either method, a higher diagnostic yield was achieved by FISH (92 and 96%) than histology alone (82 and 84%) in the 65 biopsies from SRMs (<4 cm) and 49 from larger masses, respectively. An optimized decision tree was constructed based on aberrations detected in eight chromosomes, by which the maximum concordance of classification achieved by FISH was 79%, irrespective of mass size. In SRMs, the overall sensitivity of diagnosis by FISH compared with histopathology was higher for benign oncocytoma, was similar for the chromophobe renal cell carcinoma subtype, and was lower for clear-cell and papillary subtypes. The diagnostic accuracy of classification of needle biopsy specimens (from SRMs) increased from 80% obtained by histology alone to 94% when combining histology and FISH.

CONCLUSION

The present study suggests that a novel FISH assay developed by us has a role to play in assisting in the yield and accuracy of diagnosis of renal cortical neoplasms in needle biopsies in particular, and can help guide the clinical management of patients with SRMs that were non-diagnostic by histology.

Histologic prognostic factors associated with chromosomal imbalances in a contemporary series of 89 clear cell renal cell carcinomas

Clear cell renal cell carcinoma (ccRCC) is the most common type of renal cancer. The aim of this study was to define specific chromosomal imbalances in ccRCC that could be related to clinical or histologic prognostic factors. Tumors and karyotypes of 89 patients who underwent nephrectomy for ccRCC were analyzed from April 2009 to July 2012. The mean number of chromosomal aberrations was significantly higher (7.8; P < .05) in Fuhrman grade 4 (F4) than in F3 (4) and F2 (3.4) cases. The results were similar, considering separately the mean number of chromosomal losses and gains. The F4 cases had a distinct pattern with more frequent losses of chromosomes 9, 13, 14, 18, 21, 22, and Y and gains of chromosome 20. Necrosis was associated with losses of chromosomes 7, 9, 18, and 22; sarcomatoid component, losses of chromosomes 7, 9, and 14 and gains of 20; and T stage, losses of chromosomes 18 and Y. After multivariate analysis, renal fat invasion, renal vein emboli, and microscopic vascular invasion were, respectively, associated with losses of chromosomes 13 and Y, loss of chromosome 13, and loss of chromosome 14 and gains of chromosomes 7 and 20. F4 was independently associated with losses of chromosomes 9 and Y; sarcomatoid component, loss of chromosome 9 and gain of 20; necrosis, loss of chromosome 18; and T stage, loss of chromosome Y. These chromosomal imbalances can be detected routinely by karyotype or fluorescence in situ hybridization analyses to stratify patients for risk of progression.

Clonal trisomy 4 cells detected in the ossifying renal tumor of infancy: study of 3 cases

The ossifying renal tumor of infancy is a rare neoplasm diagnosed in the first 2 years of life, predominantly in boys. The neoplasm is primarily characterized by the presence of a large ossifying component. Its most common mode of presentation is hematuria, and it has a uniformly benign behavior. The karyotypic makeup of the process has not been reported. Thus, a study was undertaken and it allowed demonstration of clonal trisomy 4, which was confirmed by the fluorescent in-situ hybridization-probing of two additional archival formalin-fixed, paraffin-imbedded similar tumors. On the basis of the findings in these three cases, it seems that clonal trisomy 4 may be considered as a characteristic of the tumor, which makes it distinct from any other infantile renal tumor.

Genetic characterization of large parathyroid adenomas

In this study, we genetically characterized parathyroid adenomas with large glandular weights, for which independent observations suggest pronounced clinical manifestations. Large parathyroid adenomas (LPTAs) were defined as the 5% largest sporadic parathyroid adenomas identified among the 590 cases operated in our institution during 2005-2009. The LPTA group showed a higher relative number of male cases and significantly higher levels of total plasma and ionized serum calcium (P<0.001). Further analysis of 21 LPTAs revealed low MIB1 proliferation index (0.1-1.5%), MEN1 mutations in five cases, and one HRPT2 (CDC73) mutation. Total or partial loss of parafibromin expression was observed in ten tumors, two of which also showed loss of APC expression. Using array CGH, we demonstrated recurrent copy number alterations most frequently involving loss in 1p (29%), gain in 5 (38%), and loss in 11q (33%). Totally, 21 minimal overlapping regions were defined for losses in 1p, 7q, 9p, 11, and 15q and gains in 3q, 5, 7p, 8p, 16q, 17p, and 19q. In addition, 12 tumors showed gross alterations of entire or almost entire chromosomes most frequently gain of 5 and loss of chromosome 11. While gain of 5 was the most frequent alteration observed in LPTAs, it was only detected in a small proportion (4/58 cases, 7%) of parathyroid adenomas. A significant positive correlation was observed between parathyroid hormone level and total copy number gain (r=0.48, P=0.031). These results support that LPTAs represent a group of patients with pronounced parathyroid hyperfunction and associated with specific genomic features.

Chromosomal amplification of leucine-rich repeat kinase-2 (LRRK2) is required for oncogenic MET signaling in papillary renal and thyroid carcinomas

The receptor tyrosine kinase MET is frequently amplified in human tumors, resulting in high cell surface densities and constitutive activation even in the absence of growth factor stimulation by its endogenous ligand, hepatocyte growth factor (HGF). We sought to identify mechanisms of signaling crosstalk that promote MET activation by searching for kinases that are coordinately dysregulated with wild-type MET in human tumors. Our bioinformatic analysis identified leucine-rich repeat kinase-2 (LRRK2), which is amplified and overexpressed in papillary renal and thyroid carcinomas. Down-regulation of LRRK2 in cultured tumor cells compromises MET activation and selectively reduces downstream MET signaling to mTOR and STAT3. Loss of these critical mitogenic pathways induces cell cycle arrest and cell death due to loss of ATP production, indicating that MET and LRRK2 cooperate to promote efficient tumor cell growth and survival in these cancers.

Feasibility of differential diagnosis of kidney tumors by comparative genomic hybridization of fine needle aspiration biopsies

The association of a genetic analysis that could improve the diagnostic accuracy of renal cell tumors in biopsy samples would allow better-informed therapeutic decisions. We performed comparative genomic hybridization (CGH) on an ex vivo fine-needle aspiration (FNA) biopsy and a tumor fragment obtained from 75 patients consecutively diagnosed with renal tumors and subjected to radical nephrectomy. The pattern of genomic changes by CGH was used blindly to classify the renal tumors and the genetic findings were subsequently compared with the histopathologic diagnosis. In particular cases, including in two carcinomas with morphologically distinct tumor areas, we performed FISH with several locus-specific probes, and looked for VHL point mutations, exonic rearrangements, or promoter methylation. CGH was successful in 82.7% FNA biopsies and in 96% tumor fragments, with the former allowing genetic diagnosis in 75% of renal cell tumors. The genetic and the initial histological classification differed in two renal neoplasias, but the genetic diagnosis was confirmed after review. The genetic pattern correctly diagnosed 93.5% of clear cell renal cell carcinomas (RCC), 61.5% of chromophobe RCC, 100% of papillary RCC, and 14.3% of oncocytomas, with the negative predictive value being 93.9, 90.7, 100, and 90.2%, respectively. The positive predictive value and specificity of copy number profiles was 100%. We demonstrate that genetic diagnosis by CGH on FNA biopsies can improve differential diagnosis in patients with kidney tumors.

Allelic loss of 6q25-27, the PARKIN tumor suppressor gene locus, in cervical carcinoma

Studies on loss of heterozygosity have been made for Parkin gene-specific microsatellite markers in malignancies like breast, ovary and lungs, and the results have shown a significant association. However, till date, there is no study with respect to Parkin gene-associated microsatellite markers in cervical cancer. The present study deals with the Parkin gene-associated microsatellite markers and the occurrence of its loss of heterozygosity in patients with human cervical cancer. DNA was isolated from the 105 cervical carcinoma samples and matched control specimens. Polymerase chain reaction was performed using primer specific for two intragenic markers D6S1599 and D6S305 present in Parkin introns 2 and 7, respectively, and one marker (D6S1008) at telomeric end and further electrophoresed on 8% denaturing polyacrylamide gel. Overall, 59 of 105 (56%) samples showed loss of heterozygosity in at least one locus in the region examined. The percentage of loss of heterozygosity for these markers ranged from 25% (D6S1008) to 48% (D6S305). Chi-square test was performed, and loss of heterozygosity was found significantly higher in both the intragenic markers (D6S1599 and D6S305) when compared with the locus at telomeric end (D6S1008) with P<0.05. These data argue that Parkin is a tumor suppressor gene whose inactivation may play an important role in the carcinoma of uterine cervix.

A Comprehensive Study of Progressive Cytogenetic Alterations in Clear Cell Renal Cell Carcinoma and a New Model for ccRCC Tumorigenesis and Progression

We present a comprehensive study of cytogenetic alterations that occur during the progression of clear cell renal cell carcinoma (ccRCC). We used high-density high-throughput Affymetrix 100 K SNP arrays to obtain the whole genome SNP copy number information from 71 pretreatment tissue samples with RCC tumors; of those, 42 samples were of human ccRCC subtype. We analyzed patterns of cytogenetic loss and gain from different RCC subtypes and in particular, different stages and grades of ccRCC tumors, using a novel algorithm that we have designed. Based on patterns of cytogenetic alterations in chromosomal regions with frequent losses and gains, we inferred the involvement of candidate genes from these regions in ccRCC tumorigenesis and development. We then proposed a new model of ccRCC tumorigenesis and progression. Our study serves as a comprehensive overview of cytogenetic alterations in a collection of 572 ccRCC tumors from diversified studies and should facilitate the search for specific genes associated with the disease.

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.

Genome-wide profiling of chromosomal alterations in renal cell carcinoma using high-density single nucleotide polymorphism arrays

The identification of genetic aberrations may help understand the mechanisms of tumorigenesis and has important implications in diagnosis, prognosis and treatment. We applied Illumina's 317K high-density single nucleotide polymorphism (SNP) arrays to profile chromosomal aberrations in clear cell renal cell carcinoma (ccRCC) from 80 patients and analyzed the association of LOH/amplification events with clinicopathological characteristics and telomere length. The most common loss of heterozygosity (LOH) were 3p (69 cases) including 38 whole 3p arm losses, 30 large fragment LOH (spanning 3p21-36), and 1 interstitial LOH (spanning 3p12-14, 3p21-22, 3p24.1-24.2 and 3p24.3), followed by chromosome losses at 8p12-pter, 6q23.3-27, 14q24.1-qter, 9q32-qter, 10q22.3-qter, 9p13.3-pter, 4q28.3-qter and 13q12.1-21.1. We also found several smallest overlapping regions of LOH that contained tumor suppressor genes. One smallest LOH in 8p12 had a size of 0.29 Mb and only contained one gene (NRG1). The most frequent chromosome gains were at 5q (32 cases), including 10 whole 5q amplification, 21 large amplifications encompassing 5q32-ter and 1 focal amplification in 5q35.3 (0.42 Mb). The other common chromosome gains were 1q25.1-qter, 7q21.13-qter, 8q24.12-qter and whole 7p arm. Significant associations of LOH at 9p, 9q, 14q and 18q were observed with higher nuclear grade. Significant associations with tumor stage were observed for LOH at 14q, 18p and 21q. Finally, we found that tumors with LOH at 2q, 6p, 6q, 9p, 9q and 17p had significantly shorter telomere length than those without LOH. This is the first study to use Illumina's SNP-CGH array that provides a close estimate of the size and frequency of chromosome LOH and amplifications of ccRCC. The identified regions and genes may become diagnostic and prognostic biomarkers as well as potential targets of therapy.

Cytogenetic profile predicts prognosis of patients with clear cell renal cell carcinoma

PURPOSE

The majority of cytogenetic studies in renal cell carcinoma (RCC) have been impaired by small sample size, retrospective character, and lack of a survival end point. We prospectively studied the prognostic impact of cytogenetic abnormalities on a larger cohort of patients having up to 108 months of follow-up.

PATIENTS AND METHODS

Tumors of 282 patients who underwent nephrectomy for clear cell RCC were cytogenetically analyzed. Results were correlated with pathological factors and disease-specific survival.

RESULTS

The most frequently observed cytogenetic abnormalities were loss of 3p (60%), gain of 5q (33%), loss of 14q (28%), trisomy 7 (26%), loss of 8p (20%), loss of 6q (17%), loss of 9p (16%), loss of 4p (13%), and loss of chromosome Y in men (55%). Tumors with loss of 3p presented at lower TNM stages. Loss of 4p, 9p, and 14q were all associated with higher TNM stages, higher grade, and greater tumor size. A deletion of 3p was associated with better prognosis (P = .03), while loss of 4p (P < .001), loss of 9p (P < .01), and loss of 14q (P < .01) were each associated with worse prognosis. Loss of the Y chromosome led to improved progression-free survival in metastatic patients (P = .02). In multivariate analysis, loss of 9p was retained as an independent prognostic factor.

CONCLUSION

This cytogenetic study serves as a proof of principal that genetic information, such as loss of chromosome 9, can be obtained from widely available technology, and can provide additional prognostic information to standard clinicopathologic variables.

Frequent loss of SFRP1 expression in multiple human solid tumours: association with aberrant promoter methylation in renal cell carcinoma

Oncogenic wingless-related mouse mammary tumour virus (Wnt) signalling, caused by epigenetic inactivation of specific pathway regulators like the putative tumour suppressor secreted frizzled-related protein 1 (SFRP1), may be causally involved in the carcinogenesis of many human solid tumours including breast, colon and kidney cancer. To evaluate the incidence of SFRP1 deficiency in human tumours, we performed a large-scale SFRP1 expression analysis using immunohistochemistry on a comprehensive tissue microarray (TMA) comprising 3448 tumours from 36 organs. This TMA contained 132 different tumour subtypes as well as 26 different normal tissues. Although tumour precursor stages of, for example kidney, colon, endometrium or adrenal gland still exhibited moderate to abundant SFRP1 expression, this expression was frequently lost in the corresponding genuine tumours. We defined nine novel tumour entities with apparent loss of SFRP1 expression, i.e., cancers of the kidney, stomach, small intestine, pancreas, parathyroid, adrenal gland, gall bladder, endometrium and testis. Renal cell carcinoma (RCC) exhibited the highest frequency of SFRP1 loss (89% on mRNA level; 75% on protein level) and was selected for further analysis to investigate the cause of SFRP1 loss in human tumours. We performed expression, mutation and methylation analysis in RCC and their matching normal kidney tissues. SFRP1 promoter methylation was frequently found in RCC (68%, n=38) and was correlated with loss of SFRP1 mRNA expression (p<0.05). Although loss of heterozygosity was found in 16% of RCC, structural mutations in the coding or promoter region of the SFRP1 gene were not observed. Our results indicate that loss of SFRP1 expression is a very common event in human cancer, arguing for a fundamental role of aberrant Wnt signalling in the development of solid tumours. In RCC, promoter hypermethylation seems to be the predominant mechanism of SFRP1 gene silencing and may contribute to initiation and progression of this disease.

Sporadic human renal tumors display frequent allelic imbalances and novel mutations of the HRPT2 gene

Inactivation of the HRPT2 gene encoding parafibromin was recently linked to the familial hyperparathyroidism-jaw tumor syndrome. Patients with this syndrome carry an increased risk of parathyroid and renal tumors. To determine the relevance of HRPT2 for sporadic renal tumors, clear cell, papillary and chromophobe renal cell carcinomas as well as oncocytomas and Wilms tumors were analysed for HRPT2 gene alterations. Loss of heterozygosity (LOH) of HRPT2 was found in seven of 56 (12.5%) clear cell, three of 14 (21%) papillary, six of 10 (60%) chromophobe renal cell carcinomas, three of eight (38%) oncocytomas and four of 10 (40%) Wilms tumors. In addition, two novel HRPT2 point mutations, causing K34Q and R292K changes in parafibromin, were detected in one clear cell carcinoma and one Wilms tumor, respectively. These tumors displayed LOH of the remaining wild-type allele, but interestingly no von Hippel-Lindau (VHL) mutation. Functional analysis revealed that the K34Q mutant species of parafibromin is, unlike wild-type protein, defective in suppressing cyclin D1 expression in vivo. Taken together, these results suggest that renal cancer-associated mutations in parafibromin occur in the absence of VHL mutation, which in turn may contribute to constitutively elevated cyclin D1 expression and abnormal cell proliferation.

Molecular pathogenetics of renal cancer

Recent developments in genetics and molecular biology have led to an increased understanding of the pathobiology of renal cancer. Thorough knowledge of the molecular pathways associated with renal cancer is a prerequisite for novel potential therapeutic interventions. Studies are ongoing to evaluate novel anticancer agents that target specific molecular entities. This article reviews current knowledge on the genetics and molecular pathogenesis of sporadic and inherited forms of renal cancer.

Zytogenetische Veränderungen bei Nierentumoren

The WHO classification of renal cell carcinomas (RCC) takes into account chromosomal alterations. New cytogenetic techniques such as comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) offer alternative methods to the classic cytogenetic banding technique. Clear cell (classic) RCC frequently show the loss of 3p. Papillary RCC are characterized by trisomies and tetrasomies as well as loss of the Y chromosome. CGH analysis demonstrates that DNA copy increase is more common in type I papillary RCC compared to type II. Chromophobe RCC are characterized by losses in chromosomes 1, 2, 6, 10, 13, 17, and 21. Oncocytomas can be divided into cases with rearrangements in the 11q13 region and those with loss of chromosome 1 and the sex chromosomes. Translocations involving chromosome 3, such as t(3;8)(p14;q24.13) and t(2;3)(q35;q21) have been described in familial clear cell RCC. The most recent class of RCC, seen only in men, is referred to as translocation tumors. These tumors demonstrate a tubulopapillary growth pattern and have a t(X;1)(p11.2;q21.2) translocation. Although not required for most clinical diagnoses, CGH and FISH complement the standard histologic diagnosis of RCC and may provide a definitive diagnosis in a small number of challenging cases.

A combination of molecular cytogenetic analyses reveals complex genetic alterations in conventional renal cell carcinoma

Here we report the complex pattern of genomic imbalances and rearrangements in a panel of 19 renal cell carcinoma cell lines detected with molecular cytogenetic analysis. Consistent heterogeneity in chromosome number was found, and most cell lines showed a near-triploid chromosome complement. Several cell lines showed deletions of the TP53 (alias p53), CDKN2A (alias p16), and VHL genes. Multiplex fluorescence in situ hybridization (M-FISH) analysis revealed chromosome 3 translocated to several other partners chromosomes, as well as breakage events commonly affecting chromosomes 1, 5, 8, 10, and 17. The most common abnormality detected with comparative genomic hybridization (CGH) was deletions of chromosome 3p, with loss of the RASSF1, FHIT, and p44S10 loci frequently involved. CGH gain of 5q showed overrepresentation of the EGR1 and CSF1R genes. Recurrent alterations to chromosome 7 included rearrangement of 7q11 and gains of the EGFR, TIF1, and RFC2 genes. Several lines exhibited rearrangement of 12q11 approximately q14 and overrepresentation of CDK4 and SAS loci. M-FISH revealed several other recurrent translocations, and CGH findings included loss of 9p, 14q, and 18q and gain of 8q, 12, and 20. Further genomic microarray changes included loss of MTAP, IGH@, HTR1B, and SMAD4 (previously MADH4) and gains of MYC and TOP1. An excellent correlation was observed between the genomic array and FISH data, demonstrating that this technique is effective and accurate. The aberrations detected here may reflect important pathways in renal cancer pathogenesis.

Advanced molecular cytogenetics in human and mouse

Fluorescence in situ hybridization, spectral karyotyping, multiplex fluorescence in situ hybridization, comparative genomic hybridization, and more recently array comparative genomic hybridization, represent advancements in the field of molecular cytogenetics. The application of these techniques for the analysis of specimens from humans, or mouse models of human diseases, enables one to reliably identify and characterize complex chromosomal rearrangements resulting in alterations of the genome. As each of these techniques has advantages and limitations, a comprehensive analysis of cytogenetic aberrations can be accomplished through the utilization of a combination approach. As such, analyses of specific tumor types have proven invaluable in the identification of new tumor-specific chromosomal aberrations and imbalances (aneuploidy), as well as regions containing tumor-specific gene targets. Application of these techniques has already improved the classification of tumors into distinct categories, with the hope that this will lead to more tailored treatment strategies. These techniques, in particular the application of tumor-specific fluorescence in situ hybridization probes to interphase nuclei, are also powerful tools for the early identification of premalignant lesions.

Hepatitis A virus receptor blocks cell differentiation and is overexpressed in clear cell renal cell carcinoma

BACKGROUND

The molecular mechanisms underlying tumorigenesis and progression of clear cell renal cell carcinoma (ccRCC) are not well understood. We aimed to identify new molecular markers to provide insight into these processes.

METHODS

This work reports on the identification of human hepatitis A virus cellular receptor 1 (hHAVcr-1) as a differentially expressed gene in ccRCC using RNA-based arbitrarily primed polymerase chain reaction (RAP-PCR). Results were further confirmed by Northern and Western blot assays. Carcinoma 769-P and normal HK-2 cells derived from proximal tubule epithelial cells, grown under different culture conditions, were used to understand the putative role of hHAVcr-1 in renal malignancy. hHAVcr-1 stable transfected clones and dipeptidyl peptidase IV (DPPIV) assays allowed assessing its involvement in cell differentiation.

RESULTS

The hHAVcr-1 is overexpressed in eight out of 13 ccRCC and its expression neglected in benign oncocytomas. In culture, hhavcr-1 is dramatically overexpressed in normal and tumor cell lines that, having acquired the fully differentiated phenotype, are induced to de-differentiate by means of phorbol ester phorbol 12-myristate-13-acetate (PMA) treatment. Similarly, differentiation prevention by addition of PMA to confluent cells also increases hhavcr-1 expression. hHAVcr-1 stable transfected 769-P cells proved that hhavcr-1 itself blocks differentiation. Since hhavcr-1 is expressed at higher levels in tumor cells, we used an African green monkey cell model to show that immunotoxins directed against the monkey homologue of hhavcr-1 could kill kidney cells.

CONCLUSION

Our results showed that hHAVcr-1 blocks differentiation of proximal tubule epithelial cells and that it could be used as a target for therapy of kidney carcinomas.

SCC-112, a novel cell cycle-regulated molecule, exhibits reduced expression in human renal carcinomas

We report here the identification and an initial characterization of a novel cell cycle-regulated molecule, SCC-112. SCC-112 cDNA (6744 bp) encodes a longest open reading frame (ORF) comprised of 1297 amino acids, representing a approximately 150-kDa nuclear protein. SCC-112 mRNA and protein levels were relatively high during the G2/M phase of the cell cycle in MDA-MB 435 breast cancer cells. Transient expression of SCC-112 cDNA in COS-1 cells led to an increase in the number of cells in sub-G1 phase and enhanced activity of caspase-3, a downstream effector of apoptosis. Stable transfection of SCC-112 cDNA in MDA-MB 231 breast cancer cells also led to an increase in the number of cells in sub-G1 phase ( approximately 2-3-fold), indicative of apoptosis. The examination of the paired sets of human normal and tumor tissues revealed that the SCC-112 mRNA level was significantly high in normal breast and kidney tissues as compared to the corresponding primary tumor tissues (P<0.0001; breast, n=50, and kidney, n=20). Consistent with these observations, SCC-112 protein expression (150 kDa) was high in a majority of the normal renal tissues examined as compared to the matched renal tumor tissues (67%, 1.2-fold to>10-fold, n=18). Taken together, these findings suggest that the SCC-112 gene expression is likely to be associated with normal cell growth and proliferation.

Genomic alterations in renal tumours: what have we learned in the era of comparative genomic hybridisation?

One of the major challenges in cancer research is to generate molecular profiles of tumours and establish correlations between genetic changes and clinical parameters by screening technologies. The identification of tumour-specific gene targets has potential diagnostic and therapeutic implications. Metaphase comparative genomic hybridisation has been used to detect relative DNA-sequence copy number gains (including high-level amplifications of chromosomal regions) and copy number losses in human neoplasms. In the past, metaphase comparative genomic hybridisation has been shown to be a powerful genome-wide screening method and this has considerably advanced our understanding of renal cancer biology. Novel molecular technologies, including array-based comparative genomic hybridisation, fluorescence in situ hybridisation (FISH), cDNA and tissue microarrays will serve to facilitate further characterisation of candidate genes residing in chromosomal regions defined by metaphase comparative genomic hybridisation. This review concentrates on the application of metaphase comparative genomic hybridisation in the area of renal cancer research and summarises data obtained from comparative genomic hybridisation studies.

The genetic basis of renal cell carcinoma

The recognition of hereditary forms of renal cancer and the development of high-throughput genetic analysis have led to the identification of genes responsible for familial renal epithelial tumors of differing histologies and cytogenetic features. Some of these genes (VHL) are known to have an important role in sporadic renal neoplasia. This article describes the various epithelial renal tumors most commonly encountered by the urologist, the molecular and cytogenetic distinctions between them, and the hereditary syndromes that predispose to these tumors. Consideration of these syndromes is important for proper treatment when one encounters patients with multiple renal tumors, tumors at an early age of onset, or patients with a positive family history of renal cell carcinoma.

Patterns of aneuploidy in stage IV clear cell renal cell carcinoma revealed by comparative genomic hybridization and spectral karyotyping

We report the use of spectral karyotyping (SKY) and comparative genomic hybridization (CGH) to describe the numerous genomic imbalances characteristic of stage IV clear cell renal cell carcinoma (CCRCC). SKY and CGH were performed on 10 cell lines established from nephrectomy specimens, and CGH on uncultured material from five of the primary renal tumors. The mutational status of VHL (3p25) and MET (7q31), genes implicated in renal carcinogenesis, were determined for each case. Each case showed marked aneuploidy, with an average number of copy alterations of 14.6 (+/-2.7) in the primary tumors and 19.3 (+/-4.6) in the cell lines. Both whole-chromosome and chromosome-segment imbalances were noted by CGH: consistent losses or gains included +5q23-->ter (100%), -3p14-->ter (80%), and +7 (70%). All VHL mutations and 83% of the genomic imbalances found in the primary tumors were also found in the cell lines derived from them. SKY showed many complex structural rearrangements that were undetected by conventional banding analysis in these solid tumors. All cases with VHL inactivation had 3p loss and 5q gain related primarily to unbalanced translocations between 3p and 5q. In contrast, gains of chromosome 7 resulted primarily from whole-chromosome gains and were not associated with mutations of MET. SKY and CGH demonstrated that genomic imbalances in advanced RCC were the result of either segregation errors [i.e., whole chromosomal gains and losses (7.8/case)] or chromosomal rearrangements (10.7/case), of which the majority were unbalanced translocations.

Chromosome 6 suffers frequent and multiple aberrations in thymoma

Thymoma is the most frequent tumor arising in human thymus. In this study, we performed a detailed mapping of deleted regions on chromosome 6 shown previously to harbor the most frequent genetic aberrations in this cancer. We analyzed 40 thymomas using 41 microsatellites. Two hundred ninety-four (23.5%) of 1253 informative genotypes showed loss of heterozygosity (LOH), only 39 (2.4%) were positive for microsatellite instability (MSI). Genetic aberrations on chromosome 6 were found in 31 of 40 cases (77.5%) in five hot spots. The most frequent LOHs (48.6%) occurred in region 6q25.2 within a 0.7-Mb interval flanked by markers D6S441 and D6S290. Another hot spot showing LOH in 32.4% of tumors was located between markers D6S442 and D6S1708 (0.4 Mb apart) on 6q25.2-25.3, just 1.1 Mb from the D6S441-D6S290 deletions. The third hot spot (30%) showing LOH appeared in region 6p21.31 including the MHC locus (markers D6S1666-D6S1560, 1 Mb apart). The fourth hot spot (26.3%) was detected on 6q14.1-14.3 (D6S1596-D6S284, 5.2 Mb apart). Some tumors (21.6%) showed LOHs within a fifth hot spot on 6q21 (D6S447-D6S1592, 0.3 Mb apart). Thus, several tumor suppressor genes on chromosome 6 seem to be involved in the pathogenesis of thymoma.