Development of papillary renal cell tumours is associated with loss of Y-chromosome-specific DNA sequences

Recalling Cohnheim's Theory: Papillary Renal Cell Tumor as a Model of Tumorigenesis from Impaired Embryonal Differentiation to Malignant Tumors in Adults

We have suggested that papillary renal cell tumor (PRCT) of the kidney arises from nephrogenic rest-like lesions. To approve our hypothesis, we worked up 14 kidneys bearing papillary and 14 ones with conventional renal cell carcinoma (CRCC) histologically and found 42 papillary lesions in average per kidney bearing PRCT. PRCTs are characterized by loss of the Y chromosome and trisomy of chromosomes 7 and 17. The MET and HNF1B are localized to chromosome 7q31 and 17q21 and are frequently amplified in PRCT. We have analyzed the expression of the mutant MET in hereditary PRCTs and precursor lesions and found duplication and expression of the mutated allele. Because both genes are involved in early stage of nephron development, we have analyzed the expression of MET and HNF1B by immunohistochemistry in fetal kidneys, precursor lesions and PRCTs. We detected strong expression of MET and HNF1B in distal compartment of S-shaped body of fetal kidneys and in nephrogenic rest-like precursor lesions. Our finding suggests an association between expression of MET and HNF1B in precursor lesions and development of PRCT. We propose a model involving chromosomal clonal evolution and corresponding gene expression for development of PRCTs from embryonic rests due to impaired differentiation. Our model suggests that PRCT have a natural history distinct from that of most common CRCC.

Origin of renal cell carcinomas

Cancer is a heritable disorder of somatic cells: environment and heredity are both important in the carcinogenic process. The primal force is the "two hits" of Knudson's hypothesis, which has proved true for many tumours, including renal cell carcinoma. Knudson et al. [1, 2] recognised that familial forms of cancer might hold the key to the identification of important regulatory elements known as tumour-suppressor genes. Their observations (i.e., that retinoblastoma tend to be multifocal in familial cases and unifocal in sporadic presentation) led them to propose a two-hit theory of carcinogenesis. Furthermore, Knudson postulated that patients with the familial form of the cancer would be born with one mutant allele and that all cells in that organ or tissue would be at risk, accounting for early onset and the multifocal nature of the disease. In contrast, sporadic tumours would develop only if a mutation occurred in both alleles within the same cell, and, as each event would be expected to occur with low frequency, most tumours would develop late in life and in a unifocal manner [3, 4]. The kidney is affected in a variety of inherited cancer syndromes. For most of them, both the oncogene/tumour-suppressor gene involved and the respective germline mutations have been identified. Each of the inherited syndromes predisposes to distinct types of renal carcinoma. Families with hereditary predisposition to cancer continue to provide a unique opportunity for the identification and characterisation of genes involved in carcinogenesis. A surprising number of genetic syndromes predispose to the development of renal cell carcinoma, and genes associated with five of these syndromes have been already identified: VHL, MET, FH, BHD and HRPT2. Few cancers have as many different types of genetic predisposition as renal cancer, although to date only a small proportion of renal cell cancers can be explained by genetic predisposition.

Second primary malignancies associated with renal cell carcinoma histological subtypes

PURPOSE

Renal cell carcinoma has been linked to numerous secondary malignancies. We evaluated the risk of secondary malignancies by renal cell carcinoma histological subtype in patients with clear cell, papillary and chromophobe renal cell carcinoma.

MATERIALS AND METHODS

We studied 2,722 patients who underwent nephrectomy for sporadic renal cell carcinoma at our institution between 1970 and 2000. All specimens were reviewed by a single urological pathologist for histological subtype. Associations of second primary malignancies by histological subtype were evaluated using the chi-square and Fisher exact tests.

RESULTS

Of the patients studied 2,188 (80.4%) had clear cell, 378 (13.9%) had papillary and 128 (4.7%) had chromophobe renal cell carcinoma. Patients with papillary renal cell carcinoma were significantly more likely to have colon cancer (p = 0.041), prostate cancer (p = 0.003), any second malignancy (p <0.001) and multiple malignancies (p <0.001) compared with patients with clear cell renal cell carcinoma. In addition, patients with chromophobe renal cell carcinoma were significantly more likely to have colon cancer than patients with clear cell renal cell carcinoma (p = 0.020). Although patients with papillary renal cell carcinoma were more likely to have bladder cancer, the incidence did not differ significantly compared with that in patients harboring clear cell and chromophobe renal cell carcinoma (p = 0.193). We did not find a significant difference in the incidence of breast cancer, lung cancer, rectal cancer or lymphoma among histological subtypes.

CONCLUSIONS

Our data indicate that patients with papillary renal cell carcinoma are more likely to harbor secondary malignancies, including colon and prostate cancer, than patients with clear cell renal cell carcinoma. These results may have important implications for patient education and followup evaluation, and they should prompt mechanistic investigations.

Characterization of quantitative chromosomal abnormalities in renal cell carcinomas by interphase four-color fluorescence in situ hybridization

Renal cell carcinomas (RCC) in adults are histologically heterogeneous solid tumors with specific chromosomal abnormality patterns included in the World Health Organization (WHO) classification. To overcome some of the drawbacks of cytogenetic and comparative genomic hybridization (CGH) analyses, we designed a first-generation cytogenetic diagnostic test using four-color fluorescence in situ hybridization (FISH) on interphase nuclei. We selected 51 bacterial artificial chromosome and P1-derived artificial chromosome clones covering 17 chromosomal regions involved in the abnormalities of the adult RCC histologic subtypes. An initial set of probes allowed the identification of clear-cell RCC, papillary RCC, and other RCC on a single slide. A second test allowed the detection of additional chromosomal abnormalities or aberrations specific to chromophobic RCC and oncocytomas. We tested 25 cases of RCC, and the results were in agreement with those of cytogenetic techniques and/or CGH methods. The techniques appeared to be very sensitive, because small tumoral cell clones that were undetected by other cytogenetic methods were identified with this method. It was concluded that the multicolor FISH test was specific and sensitive, easy to perform, and could be part of the investigation process in RCC.

Intragenic PTEN/MMAC1 loss of heterozygosity in conventional (clear-cell) renal cell carcinoma is associated with poor patient prognosis

Inactivation of the PTEN/MMAC1 tumor suppressor gene has been linked to tumor progression in several human malignancies. However, the role of PTEN/MMAC1 in the development and progression of the major renal cell carcinoma morphotypes remains controversial. We examined microdissected specimens from 80 conventional (clear cell) renal cell carcinomas (cRCC), 27 papillary renal cell carcinomas (pRCC), and 16 chromophobe renal cell carcinomas (chRCC) for loss of heterozygosity (LOH) at and around the PTEN/MMAC1 locus and for mutations in the PTEN/MMAC1 gene. The results of the molecular studies were correlated with tumor stage, grade, and patient survival. LOH at one or more of the examined loci occurred in 37.5% of cRCC, 29.6% of pRCC and 87.5% of chRCC specimens. The chRCC specimens showed increasing rates of LOH the further that a marker was located toward the q telomer of chromosome 10, consistent with nonspecific genetic disarray in genomically highly unstable tumors. No such pattern was discernible in the cRCC and pRCC. In the cRCC, LOH at intragenic PTEN/MMAC1 microsatellite markers (indicating deletional events involving the actual PTEN/MMAC1 gene) was significantly associated with tumor death, with 85.7% of such patients dying, whereas only 45.3% of patients without intragenic LOH died (P =.018). There were no PTEN/MMAC1 mutations in our specimens. We conclude that PTEN/MMAC1 inactivation may play a role in the progression of cRCC. Biallelic inactivation may preferentially occur by nonmutational mechanisms, or, alternatively, haploinsufficiency of PTEN/MMAC1 may be sufficient to affect tumor progression in cRCC.

Papillary renal cell carcinoma: analysis of germline mutations in the MET proto-oncogene in a clinic-based population

Approximately 10% of all renal cell carcinomas (RCCs) present a distinctive papillary histology. Familial papillary RCC (PRCC) has been described, but the majority of cases appear to be sporadic. Recently, germline mutations in the MET proto-oncogene on chromosome 7 have been identified in families with hereditary PRCC. We evaluated 59 patients with PRCC for the frequency of MET germline mutations to determine the value of genetic screening of this patient population. Between 1976 and 1997, 165 patients were identified with PRCC by retrospective chart review. Fifty-nine of 133 surviving patients agreed to provide a family history, a blood specimen, and informed consent for genetic research. DNA was isolated from peripheral blood leukocytes. Denaturing high-performance liquid chromatography (DHPLC) followed by genomic sequencing was performed on eight exons of the MET proto-oncogene, including exons 5-7 of the extracellular domain, exon 14, and exons 16-19 of the tyrosine kinase domain. The 59 patients in this study included 49 men and 10 women with a mean age at diagnosis of 61 years. Bilateral and/or multifocal disease was present in 13 cases (22%). No germline mutations were detected in the studied exons of the MET proto-oncogene (exons previously reported to contain deleterious mutations in familial PRCC). No pathological MET proto-oncogene germline mutations were identified in 59 patients with PRCC. The germline mutation rate in this clinic-based population of individuals with PRCC approaches 0% (CI = 0-6.18). MET proto-oncogene germline mutation screening does not appear to be clinically indicated in patients with PRCC without additional evidence for a genetic predisposition (positive family history, unusual age at onset, bilateral disease).

Inter-observer variation between general and specialist gastrointestinal pathologists when grading dysplasia in ulcerative colitis

Histological dysplasia is the cornerstone of colorectal cancer surveillance in ulcerative colitis (UC). Recently, pathologists have received unfavourable media attention concerning other cancer screening programmes. The aim of this study was to determine whether colonic biopsy specimens should be examined by gastrointestinal pathologists as opposed to generalists, by examining inter-observer variation between the two groups. Fifty-one coded slides showing varying degrees of dysplasia were mailed to seven gastrointestinal and six general histopathologists. Pathologists allocated each biopsy into one of four categories without the benefit of a clinical history or an opportunity to use the 'indefinite' category that is included in the Riddell classification. The responses were analysed using kappa statistics. The overall kappa statistic for gastrointestinal pathologists was 0.30 [95% confidence interval (CI)=0.26-0.34] and for general pathologists 0.28 (95% CI=0.23-0.32). Agreement was best for high-grade dysplasia (kappa of 0.54 and 0.61 for GI and general pathologists, respectively). There was total concordance of the 13 pathologists in only four of the 51 slides (7.8%) (95% CI=0.4-15.2%). It is concluded from these results that gastrointestinal pathologists are no better than generalists when grading dysplasia in UC and that agreement is poor in both groups. There is therefore no evidence that there would be any benefit in having specialist histopathology centres concentrating specifically on the interpretation of all surveillance colonoscopy biopsies from around the UK. It must be made clear to the public that surveillance and screening programmes carry a significant rate of histological error and that perfection cannot be expected or achieved with present methods.

Specific cytogenetic aberrations in two novel human prostatic cell lines immortalized by human papillomavirus type 18 DNA

Using chromosome banding and fluorescence in situ hybridization (FISH) with painting probes, sequential cytogenetic analysis was performed of two novel prostate cell lines, PZ-HPV-7 and CA-HPV-10, established by human papillomavirus (HPV) 18 DNA transformation. PZ-HPV-7 originates from a normal diploid prostate epithelial cell strain. PZ-HPV-7 progressed from an initial diploid to a hypertetraploid chromosome number with a relative gain of chromosomes 5 and 20 (7 to 8 copies each). Structural changes were limited; 3p- (2 copies), 3q- (1 copy), and possibly a der(16p;12q). CA-HPV-10 originates from an epithelial cell strain derived from a high-grade human prostate cancer specimen, which showed several karyotypic abnormalities including an extra Y chromosome and double minutes (dmin). In early passage the karyotype of CA-HPV-10 appeared unstable with a decreasing number of cells exhibiting dmin. In late passage the dmin were replaced by a large homogeneously staining region (hsr) on 9p+ marker. The hsr was shown by FISH to be of chromosome 1 origin. The modal number was mainly hypertriploid (72, range 69 to 75). Loss of Y was remarkable (0 to 1 copy). Consistent markers included two copies each of del(1)(q12q31) and der(9)t(1;9)(?;p22), and one der(11)t(4;11) (?;q21). HPV type 18 genomic integration sites were identified on 1p for PZ-HPV-7 and on the 9p+ marker for CA-HPV-10. In conclusion, both PZ-HPV-7 and CA-HPV-10 showed clonal cytogenetic changes. These two cell lines constitute a novel in vitro model to study the mechanisms involved in human prostate carcino-genesis.

Chromophilic renal cell carcinoma: cytomorphological and cytogenetic characterisation of four permanent cell lines

Chromophilic renal cell carcinoma is a distinct type of human renal cancer, only recently recognised and defined by its characteristic histomorphological aspect and cytogenetic aberrations. We are the first to report on the establishment and cytogenetic characterisation of a panel of four permanent cell lines, i.e. chromphi-1, -2, -3 and -4, derived from strictly defined renal cell carcinomas (RCCs) of the chromophilic type and kept in continuous culture for up to 5 years. Immunohistochemistry revealed coexpression of vimentin and cytokeratins in all cell lines the cytokeratin polypeptide patterns, however, varying between the different cell lines. By light and transmission electron microscopy, various amounts of cytoplasmatic glycogen deposition were observed, being most pronounced in chromphi-3 and -4. The mean population doubling time ranged from 24 h (chromphi-1) to 51 h (chromphi-4). Chromphi-1 tumour cells produced slowly growing tumours in nude mice using the subrenal capsule assay. In all cell lines, cytogenetic analysis revealed numerical chromosomal aberrations known to be characteristic for chromophilic RCCs, i.e. loss of the Y chromosome, tri- or tetrasomy of chromosomes 7 and 17 as well as various combinations of additional structural and numerical chromosomal aberrations. Karyological aberrations were least pronounced in chromphi-2 and most complex in chromphi-1. Chromosomal aberrations typically affecting the short arm of chromosome 3 in clear cell RCCs were not observed in any of our cell lines.

Chromosomal findings and p53-mutation analysis in chromophilic renal-cell carcinomas

The chromosomal pattern of 31 specimens of chromophilic renal-cell cancer (RCC), selected according to the criteria mentioned in the classification of Thoenes and Störkel, is presented. A high male preponderance was found (8.7:1). Cytogenetic analysis revealed a typical pattern of numeric alterations specific for this sub-type in the majority of cases (i.e., --Y,+7, +12, +16, +17, and/or +20), which is different from the chromosomal patterns found in other sub-types of RCC. Gain of chromosome 20, as well as loss of the extra copy of chromosome 17 or loss of 17p, was found to be related to the higher-grade chromophilic carcinomas. None of the 14 cases examined by SSCP analysis revealed mutations of the p53 gene, indicating that other genes at 17(p) might be important in the progression of this sub-type of RCC.

Polyclonal origin of colonic adenomas in an XO/XY patient with FAP

It is widely accepted that tumors are monoclonal in origin, arising from a mutation or series of mutations in a single cell and its descendants. The clonal origin of colonic adenomas and uninvolved intestinal mucosa from an XO/XY mosaic individual with familial adenomatous polyposis (FAP) was examined directly by in situ hybridization with Y chromosome probes. In this patient, the crypts of the small and large intestine were clonal, but at least 76 percent of the microadenomas were polyclonal in origin.

Distinct Xp11.2 breakpoints in two renal cell carcinomas exhibiting X;autosome translocations

Several human renal cell carcinomas with X;autosome translocations have been reported in recent years. The t(X;1)(p11.2;q21) appears to be a specific primary anomaly, suggesting that tumors with this translocation form a distinct subgroup of RCC. Here we report two new cases, one with a t(X;10)(p11.2;q23), the other with a t(X;1)(p11.2;p34). The common breakpoint in Xp11.2 suggests that they belong to the above-mentioned subset of RCC. Using FISH in conjunction with X-specific YAC clones, we demonstrate that the two new cases exhibited distinct breakpoints within Xp11.2.