von Hippel-Lindau gene mutations in human and rodent renal tumors--association with clear cell phenotype

Epidemiology of Renal Cell Carcinoma

The increasing incidence of RCC in most populations may in part be due to increasing numbers of incidentally detected cancers with new imaging methods. Further, the increase is not only limited to small local tumours but also includes more advanced tumours, which may to some part explain the still high mortality rates. The variation in incidence between populations may have several other explanations. Traditionally the starting point has included thoughts of environmental exposures, which so far have only in part explained the causes of RCC, by means of cigarette smoking and obesity, which may account for approximately 40% of cases in high-risk countries (Table 2). Further, the genetic variations may be of importance as a cause of the difference between populations. Continued research in RCC is needed with the knowledge that nearly 50% of patients die within 5 years after diagnosis. The further search for environmental exposures should take in account the knowledge that RCC consists of different types with specific genetic molecular characteristics. These genetic alterations have in some cases been suggested to be associated with specific exposures. Furthermore, there might exist a modulating effect of genetic polymorphisms among metabolic activation and detoxification enzymes. Hence, a further understanding of the genetic and molecular processes involved in RCC will hopefully give us a better knowledge how to analyse and interpret exposure associations that have importance for both initiation and progression of RCC.

Occupational kidney cancer: exposure to industrial solvents

We report seven cases of renal cell carcinoma in workers diagnosed with occupational exposure via skin contact and inhalation to industrial solvents containing benzene. The clinical significance of these cases are: (a) all seven patients diagnosed with kidney cancer were seen by private physicians who missed addressing occupational history to industrial solvents; (b) emphasize the importance of taking an in-depth history including occupational history in any patient presented to the clinician, especially like in these cases, kidney cancer; and (c) demonstrate the importance of educating workers. We believe that there exist more patients with renal cancer whose diagnosis has been rendered "idiopathic" due to the lack of detailed occupational, environmental, personal, and family history.

Morphologic and Molecular Characterization of Renal Cell Carcinoma in Children and Young Adults

A new WHO classification of renal cell carcinoma has been introduced in 2004. This classification includes the recently described renal cell carcinomas with the ASPL-TFE3 gene fusion and carcinomas with a PRCC-TFE3 gene fusion. Collectively, these tumors have been termed Xp11.2 or TFE3 translocation carcinomas, which primarily occur in children and young adults. To further study the characteristics of renal cell carcinoma in young patients and to determine their genetic background, 41 renal cell carcinomas of patients younger than 22 years were morphologically and genetically characterized. Loss of heterozygosity analysis of the von Hippel-Lindau gene region and screening for VHL gene mutations by direct sequencing were performed in 20 tumors. TFE3 protein overexpression, which correlates with the presence of a TFE3 gene fusion, was assessed by immunohistochemistry. Applying the new WHO classification for renal cell carcinoma, there were 6 clear cell (15%), 9 papillary (22%), 2 chromophobe, and 2 collecting duct carcinomas. Eight carcinomas showed translocation carcinoma morphology (20%). One carcinoma occurred 4 years after a neuroblastoma. Thirteen tumors could not be assigned to types specified by the new WHO classification: 10 were grouped as unclassified (24%), including a unique renal cell carcinoma with prominently vacuolated cytoplasm and WT1 expression. Three carcinomas occurred in combination with nephroblastoma. Molecular analysis revealed deletions at 3p25-26 in one translocation carcinoma, one chromophobe renal cell carcinoma, and one papillary renal cell carcinoma. There were no VHL mutations. Nuclear TFE3 overexpression was detected in 6 renal cell carcinomas, all of which showed areas with voluminous cytoplasm and foci of papillary architecture, consistent with a translocation carcinoma phenotype. The large proportion of TFE3 "translocation" carcinomas and "unclassified" carcinomas in the first two decades of life demonstrates that renal cell carcinomas in young patients contain genetically and phenotypically distinct tumors with further potential for novel renal cell carcinoma subtypes. The far lower frequency of clear cell carcinomas and VHL alterations compared with adults suggests that renal cell carcinomas in young patients have a unique genetic background.

Age-specific familial risks for renal cell carcinoma with evidence on recessive heritable effects

BACKGROUND

Systematic comparisons of mode of inheritance for renal cell carcinoma (RCC) have not been carried out. The occurrence of cancer in parents and offspring may be due to dominant causes, whereas cancer affecting only siblings may indicate a recessive causation. Environmental effects need to be excluded.

METHODS

The Swedish Family-Cancer Database includes all Swedes born after 1931 with their biologic parents, totaling 10.2 million persons. Cancer data were retrieved from the Swedish Cancer Registry from years 1961 to 2000, included 2415 cases of RCC in offspring and 18531 in parents. Standardized incidence ratios (SIRs) and 95% CI limits were calculated for offspring whose parents or sibling were diagnosed with RCC.

RESULTS

The SIRs for siblings for RCC depended on their age difference. SIR was 7.63 (95% CI 3.63-14.08) when the age difference was less than 3 years and compared to 3.43 (95% CI 1.77-6.02) for large age difference. SIRs for familial risk of RCC were 1.73 (95% CI 1.31-2.26) when a parent and 4.58 (95% CI 2.87-6.94) when a sibling had RCC. Age-specific analysis of familial RCC among siblings revealed maxima at ages 40 to 49 and 60 to 68 years.

CONCLUSION

The findings in the present study offer evidence on recessive effects in early onset RCC.

Familial risk of cancer by site and histopathology

Familial risks for histopathology-specific cancers have not been determined. We used the nationwide Swedish Family-Cancer Database on 10.2 million individuals and 1 million tumors to calculate standardized incidence ratios (SIRs) for familial cancers of specific histology and morphology among 0- to 66-year-old offspring. We used histology codes for both offspring and parents, but because of the limited number of cases, the morphology-specific classification could be used only for offspring by all site-specific cancers in parents, resulting in inflated risk estimates. A number of novel findings emerged in the histopathology-specific analysis of familial risks, in addition to some known associations. Overall, specific histology showed an SIR of 2.07 for all cancers compared to an SIR of 2.00 for any histology. However, the small effect was due to breast and prostate cancers, which showed a negligible effect of specific histology. Familial risks of over 4.0 were found for serous papillary cystadenocarcinoma of the ovary, papillary thyroid cancer and low-grade astrocytoma. Familial risks of over 3.0 were found for signet-ring gastric cancer, various forms of ovarian cancer and squamous cell skin cancer. Also noteworthy were familial risks of hepatocellular carcinoma (2.48), pancreatic adenocarcinoma (1.92), large cell carcinoma and adenocarcinoma of the lung (2.29 and 2.18, respectively) and clear cell carcinoma of the kidney (2.73). Many of the findings were novel and could be revealed only by applying codes for specific histopathology. These data call for a closer description of familial aggregations and probing for the underlying genetic mechanisms.

Aberrant methylation of the ATM promoter correlates with increased radiosensitivity in a human colorectal tumor cell line

Recent findings suggest that DNA alkylating agents trigger cellular responses that overlap those activated after ionizing radiation. Moreover, activation of these responses is dependent upon a functional mismatch repair (MMR) system. These developments led us to test if MMR-deficient cells may be compromised in their ability to activate appropriate cellular signaling pathways after ionizing radiation. An initial experiment to address this notion was to determine the level of radiosensitivity of several MMR-deficient cell lines derived from patients with Hereditary Non-Polyposis Colorectal Cancer (HNPCC). While two of the three HNPCC lines investigated show levels of radiosensitivity consistent with that displayed by normal human fibroblasts, HCT-116 cells display moderate radiosensitivity compared to the other MMR-deficient lines. This increased sensitivity to ionizing radiation correlates with lowered levels of ATM expression in HCT-116. Analysis of genomic DNA from HCT-116 cells determined that these cells possess aberrant methylation of multiple CpG dinucleotides within the proximal promoter region of the ATM gene. The significance of this finding is underscored by our observations that co-culturing HCT-116 cells with the DNA demethylating agent 5-azacytidine reverses promoter methylation, promotes normal levels of ATM expression, and restores normal radiosensitivity. The proximal ATM promoter is a approximately 520 bp region shared with the NPAT gene, and current evidence suggests that this region functions as a bi-directional promoter. We found that, unlike ATM, the methylation status of this intergenic region does not effect the expression of the NPAT gene. In sum, these observations indicate that the ATM gene is a novel target for epigentic silencing through inappropriate methylation of its proximal promoter region.

Mutational analysis of the von hippel lindau gene in clear cell renal carcinomas from tuberous sclerosis complex patients

Tuberous sclerosis complex (TSC) is an autosomal-dominant disorder characterized by seizures, mental retardation, autism, and tumors of multiple organs. Renal disease in TSC includes angiomyolipomas, cysts, and renal cell carcinomas. It is known that somatic mutations in the von Hippel Lindau (VHL) tumor suppressor gene occur in most clear cell renal carcinomas. To determine whether TSC-associated clear cell carcinomas also contain VHL mutations, we analyzed six tumors for loss of heterozygosity in the VHL gene region of chromosome 3p and for mutations in the VHL gene. Four of the patients were women between the ages of 34 and 68 years, and two were males under the age of 21 years. The loss of heterozygosity analysis was performed using polymorphic microsatellite markers, and the mutational analysis was performed using direct sequencing. Chromosome 3p loss of heterozygosity was not detected, and no VHL mutations were identified. These findings suggest that mutations in the TSC1 and TSC2 genes lead to clear cell renal carcinogenesis via an alternate pathway not involving VHL mutations.