Loss of tuberin in both subependymal giant cell astrocytomas and angiomyolipomas supports a two-hit model for the pathogenesis of tuberous sclerosis tumors

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by seizures, mental retardation, and tumors of skin, brain, heart, and kidney. In this study, we focused on two of the most frequent tumors in TSC patients, renal angiomyolipomas and subependymal giant cell astrocytomas (SEGAs). Two questions were addressed. First, is loss of tuberin, the product of the TSC2 gene, seen in both renal and central nervous system tumors from TSC patients? Second, when loss of tuberin occurs, does it affect each of the cell types seen in these tumors? We used a loss of heterozygosity approach to identify tumors from TSC2 patients. We found loss of tuberin immunostaining in the spindle and epithelioid cells but not in the giant cells of six TSC2 SEGAs. We also found loss of tuberin immunostaining in all three cell types (smooth muscle, fat, and vessels) of six TSC2 angiomyolipomas. Chromosome 16p13 loss of heterozygosity occurred in both spindle and epithelioid cells of a SEGA and in smooth muscle and fat but not the vessels of two angiomyolipomas. These results support a two-hit tumor suppressor model for the pathogenesis of SEGAs and angiomyolipomas. The vascular elements of angiomyolipomas and the giant cells of SEGAs may be reactive rather than neoplastic.

Identification of MEN1 gene mutations in sporadic carcinoid tumors of the lung

Lung carcinoids occur sporadically and rarely in association with multiple endocrine neoplasia type 1 (MEN1). There are no well defined genetic abnormalities known to occur in these tumors. We studied 11 sporadic lung carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene were inactivated. All four tumors showed the presence of a MEN1 gene mutation and loss of the other allele. Observed mutations included a 1 bp insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide substitution affecting a donor splice site. Each mutation predicts truncation or potentially complete loss of menin. The remaining seven tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH. The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a complex germline MEN1 gene mutation. The data implicate the MEN1 gene in the pathogenesis of sporadic lung carcinoids, representing the first defined genetic alteration in these tumors.

[Cytotoxicity and genotoxicity of methyl tert-butyl ether and its metabolite to human leukemia cells]

DNA damage of human leukemia (HL-60) cells caused by methyl tert-butyl ether (MTBE), a new gasoline additive, and its metabolites tert-butyl alcohol (TBA), a-hydroxyisobutyric acid (HIBA) and formaldehyde was determined by single cell gel electrophoresis (SCGE), with release of lactate dehydrogenase as an indicator for evaluating its cytotoxicity. Results showed that MTBE, TBA and HUBA at levels of 1 to 30 mmol/L could cause DNA damage in a dose-dependent pattern. Formaldehyde at level of 5 mumol/L could cause DNA damage, but at a higher level could decrease DNA migration. It suggested that MTBE and its metabolites could have genotoxicity, however, with doses causing genotoxic effects, no cytotoxic effect by MTBE, TBA and HIBA was observed, but formaldehyde presented obvious cytotoxic effect.

Somatic mutations of the MEN1 tumor suppressor gene in sporadic gastrinomas and insulinomas

Gastrinomas and insulinomas are frequent in multiple endocrine neoplasia type 1 (MEN1). The MEN1 tumor suppressor gene was recently identified. To elucidate the etiological role of the MEN1 gene in sporadic enteropancreatic endocrine tumorigenesis, we analyzed tumors (28 gastrinomas and 12 insulinomas) from 40 patients for MEN1 gene mutations and allelic deletions. One copy of the MEN1 gene was found to be deleted in 25 of 27 (93%) sporadic gastrinomas and in 6 of 12 (50%) sporadic insulinomas. MEN1 gene mutations were identified in 9 of 27 (33%) sporadic gastrinomas and 2 of 12 (17%) insulinomas and were not seen in corresponding germ-line DNA sequence. A specific MEN1 mutation was detected in one gastrinoma and in the corresponding germ-line DNA of a patient who had no family history of MEN1. Somatic MEN1 gene mutations and deletions play a critical role in the tumorigenesis of sporadic gastrinomas and may also contribute to the development of a subgroup of insulinomas.

Eighteen new polymorphic markers in the multiple endocrine neoplasia type 1 (MEN1) region

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder in which affected individuals develop tumors primarily in the parathyroids, anterior pituitary, endocrine pancreas, and duodenum. The locus for MEN1 is tightly linked to the marker PYGM on chromosome 11q13, and linkage analysis has previously placed the MEN1 gene within a 2-Mb interval flanked by markers D11S1883 and D11S449. Loss of heterozygosity (LOH) studies in MEN1 and sporadic tumors have helped narrow the location of the gene to a 600-kb interval between PYGM and D11S449. Eighteen new polymerase chain reaction (PCR)-based polymorphic markers were generated for the MEN1 region, with ten mapping to the PYGM-D11S449 interval. These new markers, along with 14 previously known polymorphic markers, were precisely mapped on a 2.8-Mb (D11S480-D11S913) high-density clone contig-based, physical map generated for the MEN1 region.

[Extraction, purification and ascertainment of anti-hepatoma active principles for targeted preparation of radix Aconiti Kusnezoffii]

The extraction, purification, pharmacological experiments and chemical analysis of anti-hepatoma active principles of Radix Aconiti Kusnezoffii have been studied. The results show that the medicinal material Radix Aconiti Kusnezoffii is efficacious in inhibiting hepatoma, and the active principles are mainly made up of poisonous ester alkaloids. The liver targeting delivery system will be the first choice for its anti-hepatoma preparation, and the effective component AY3a is fit for the preparation of targeted microspheres.

[Cloning and expression of promoter and signal peptide function fragments from Lactococcus lactis in Escherichia coli]

Promoter and signal peptide function fragments from Lactococcus lactis were cloned in E. coli using a promoter-signal sequence probe vector pGPB14. Forty-two clones were obtained, whose level of resistance to ampicillin ranged from 100 to 8000 micrograms/ml. Eight clones were selected for beta-lactamase distribution assay. The beta-lactamase activity was found mainly in the periplasm, which indicated successful secretion of the enzyme. Southern hybridization test demonstrated that the inserted fragments were indeed from L. lactis. Restriction enzyme analysis revealed that the size of inserted fragments ranged from 80bp to 400 bp, four of which were sequenced on the vector pGEM-3Zf. It was found that the inserted fragments of pSEQ8 and pSEQ12 turned out to be part of the inserted fragments of pSEQ4 and pSEQ17 respectively. Promoter and translation initiation codon were found among all four fragments signal sequenced. One typical S. D. sequence and one atypical signal sequence were found in pHSB4 and pHSB8, while the other two contained no typical S. D. sequence and signal peptide sequence. In addition, it was found that the upstream regions of the promoter contributed to the efficiency of transcription initiation.

Concordance of genetic alterations in poorly differentiated colorectal neuroendocrine carcinomas and associated adenocarcinomas

BACKGROUND

The histopathologic spectrum of colorectal neuroendocrine tumors ranges from benign to highly malignant. In this spectrum, poorly differentiated neuroendocrine carcinoma (PDNC) is the most aggressive type, characterized by early dissemination and a rapidly fatal course. Since it is unclear whether PDNC originates from neoplastic transformation of preexisting neuroectodermal cells, pluripotent epithelial stem cells, or adenocarcinoma precursor cells, we investigated the histogenesis of this type of cancer by performing genetic analyses on a series of colorectal tumors.

METHODS

Archived histologic sections of colorectal PDNC from nine patients were analyzed; gastrointestinal carcinoid tumor specimens from four patients were used as controls. The specimens were deparaffinized, microdissected, and analyzed genetically. After DNA extraction, polymerase chain reaction amplification was performed to investigate alteration (i.e., loss of heterozygosity [LOH]) of the APC (adenomatous polyposis coli), DCC (deleted in colorectal carcinoma), and p53 (also known as TP53) genes.

RESULTS

LOH of the APC, DCC, or p53 genes was observed in six of eight informative PDNC tumors; no LOH was detected in the carcinoid control specimens. Four of five informative PDNC tumors had associated adenocarcinoma; LOH of the APC and p53 genes in these tumors involved the same allele in both tissue components. Four of the five tumors with associated adenocarcinoma showed LOH of the DCC gene; in three of these four tumors, the PDNC and adenomatous components showed LOH of the same allele.

CONCLUSIONS

PDNC and associated adenocarcinoma appear to be derived from the same cell of origin, which is most likely either a pluripotent epithelial stem cell or an adenocarcinoma precursor cell.

Allelic deletion and mutation of the von Hippel-Lindau (VHL) tumor suppressor gene in pancreatic microcystic adenomas

An association between pancreatic microcystic (serous) adenomas (MCAs) and von Hippel-Lindau (VHL) disease has been suggested. However, genetic alterations of the VHL gene in MCAs of the pancreas have never been reported. In this study, we performed genetic analysis of 12 pancreatic MCAs. In 2 cases, VHL disease was documented clinically, and 10 cases were sporadic. For LOH analysis, tumor and normal pancreatic cells were procured from formalin-fixed, paraffin-embedded material using tissue microdissection. After DNA extraction, the samples were amplified by polymerase chain reaction using the polymorphic markers D3S2452, D3S1110, D3S192, and D3S656. In addition, the sporadic tumors were analyzed for VHL gene mutations using probes 3b/10b and K55/K56. Both MCAs associated with VHL disease showed LOH with at least one of the microsatellite markers tested. Among the 10 sporadic cases, 7 tumors showed LOH at the VHL gene locus. A somatic VHL gene mutation on exon 2 was documented in one sporadic case. The study provides the first direct genetic evidence for the role of the VHL gene in MCA tumorigenesis. Furthermore, VHL gene alterations may be detected in both VHL-associated and sporadic pancreatic MCAs.

The multiple endocrine neoplasia type I gene locus is involved in the pathogenesis of type II gastric carcinoids

BACKGROUND & AIMS

Both gastrin and genetic factors were suggested to underlie the pathogenesis of multiple gastric enterochromaffin-like (ECL) cell carcinoids. To assess the role of genetic alterations in carcinoid tumorigenesis, loss of heterozygosity (LOH) at the locus of the multiple endocrine neoplasia type 1 (MEN-1) gene was studied in gastric carcinoids of patients with MEN-1 and chronic atrophic type A gastritis (A-CAG), as well as in sporadically arising intestinal carcinoids.

METHODS

DNA extracted from archival tissue sections of 35 carcinoid tumors was assessed for LOH with eight polymorphic markers on chromosome 11q13. A combined tumor and family study was performed in 1 patient with MEN-1-Zollinger-Ellison syndrome (ZES).

RESULTS

LOH at 11q13 loci was detected in 15 of 20 (75%) MEN-1-ZES carcinoids, and each ECL-cell carcinoid with LOH showed deletion of the wild-type allele. Only 1 of 6 A-CAG carcinoids displayed LOH at the MEN-1 gene locus, and none of the 9 intestinal and rectal carcinoids showed 11q13 LOH.

CONCLUSIONS

Gastric ECL-cell carcinoid is an independent tumor type of MEN-1 that shares a common developmental mechanism (via inactivation of the MEN-1 gene) with enteropancreatic and parathyroid MEN-1 tumors. Further analysis of sporadic and A-CAG carcinoids is needed to elucidate genetic factors involved in their tumorigenesis.

Identical genetic changes in different histologic components of Wilms' tumors

BACKGROUND

In young children and infants, Wilms' tumor is the most common cancer of the kidney. Wilms' tumor exhibits heterogeneous histopathologic features, consisting of rapidly proliferating blastemal and epithelial cells and a stromal component that has heterologous elements (e.g., cartilage, bone, and striated muscle). It is unclear whether the stromal and heterologous components of sporadic Wilms' tumor are neoplastic or should be considered non-neoplastic.

PURPOSE

Our purpose was twofold: 1) to selectively analyze the different histologic tissue components of sporadic Wilms' tumors, including blastemal, epithelial, stromal, and heterologous elements, for loss of heterozygosity (LOH) of the WT1 gene and for expression of the WT1 gene and 2) to determine the role of WT1 gene expression in the development of these tissues.

METHODS

By use of tissue microdissection techniques, various histologic elements (blastema, stroma, epithelium, and striated muscle) of sporadic Wilms' tumor were obtained from specimens taken from 18 patients. DNA was extracted from the dissected tissue fragments, and DNA solutions were amplified by use of the polymerase chain reaction and the polymorphic genomic markers D11S1392 and D11S904 to detect LOH at the WT1 gene locus (11p13). Three selected specimens with heterologous elements and LOH at 11p13 were analyzed for expression of the WT1 gene by means of the in situ reverse transcription-polymerase chain reaction.

RESULTS

Nine (50%) of the 18 specimens showed LOH at the WT1 locus. Although identical WT1 gene deletion was consistently observed in all of the various histologic components of these nine specimens, WT1 gene expression was high in the blastemal and epithelial elements and low in the stromal and heterologous elements.

CONCLUSIONS AND IMPLICATIONS

Identical allelic deletion at 11p13 in all components of the sporadic Wilms' tumors examined suggests that the stromal tissue components are neoplastic rather than non-neoplastic. In conjunction with variable WT1 gene expression in the different histologic components, the results raise the possibility that undifferentiated blastemal cells are the precursors of the stromal and heterologous elements. Morphologically benign stromal and heterologous elements may therefore be derived from neoplastic cells. The developmental state of the various tissue components of Wilms' tumor may be attributed to an altered residual WT1 gene that is required for the maturation of blastemal and epithelial cells but that is not required for the maturation of stromal and heterologous elements.

Somatic mutation of the MEN1 gene in parathyroid tumours

Primary hyperparathyroidism is a common disorder with an annual incidence of approximately 0.5 in 1,000 (ref. 1). In more than 95% of cases, the disease is caused by sporadic parathyroid adenoma or sporadic hyperplasia. Some cases are caused by inherited syndromes, such as multiple endocrine neoplasia type 1 (MEN1; ref. 2). In most cases, the molecular basis of parathyroid neoplasia is unknown. Parathyroid adenomas are usually monoclonal, suggesting that one important step in tumour development is a mutation in a progenitor cell. Approximately 30% of sporadic parathyroid tumours show loss of heterozygosity (LOH) for polymorphic markers on 11q13, the site of the MEN1 tumour suppressor gene. This raises the question of whether such sporadic parathyroid tumours are caused by sequential inactivation of both alleles of the MEN1 gene. We recently cloned the MEN1 gene and identified MEN1 germline mutations in fourteen of fifteen kindreds with familial MEN1 (ref. 10). We have studied parathyroid tumours not associated with MEN1 to determine whether somatic mutations in the MEN1 gene are present. Among 33 tumours we found somatic MEN1 gene mutation in 7, while the corresponding MEN1 germline sequence was normal in each patient. All tumours with MEN1 gene mutation showed LOH on 11q13, making the tumour cells hemi- or homozygous for the mutant allele. Thus, somatic MEN1 gene mutation for the mutant allele. Thus, somatic MEN1 gene mutation contributes to tumorigenesis in a substantial number of parathyroid tumours not associated with the MEN1 syndrome.

Identification of a novel transcript up-regulated in a clinically aggressive prostate carcinoma

OBJECTIVES

To identify differentially expressed genes in tumor cells of patients with prostate cancer by means of tissue microdissection and targeted differential display.

METHODS

RNA was recovered from pure populations of microdissected normal epithelium and invasive tumor from frozen tissue sections of a radical prostatectomy specimen. Reverse transcription-polymerase chain reaction (PCR) using arbitrary and zinc finger PCR primers was performed.

RESULTS

A 130-base pair product was identified that appeared selectively in the tumor sample. DNA sequence analysis revealed it to be a clone from the expressed sequence tag database (GenBank accession R00504). Microdissection of normal epithelium and the corresponding invasive tumor was subsequently performed on a test panel of 10 prostate carcinoma specimens. Comparison of R00504 levels in normal epithelium and invasive carcinoma, using beta-actin as an internal control, showed the transcript to be substantially overexpressed in 5 of 10 carcinomas. Northern blotting revealed R00504 to be a 2.6-kilobase gene.

CONCLUSIONS

A novel transcript up-regulated in an aggressive prostate carcinoma was identified using degenerate zinc finger primers in microdissected tissue samples. The approach used in this study may be helpful in quantitative comparison of known genes and identification of novel genes in microdissected human tissue samples.

Germline mutations of the MEN1 gene in familial multiple endocrine neoplasia type 1 and related states

Familial multiple endocrine neoplasia type 1 (FMEN1) is an autosomal dominant trait characterized by tumors of the parathyroids, gastro-intestinal endocrine tissue, anterior pituitary and other tissues. We recently cloned the MEN1 gene and confirmed its identity by finding mutations in FMEN1. We have now extended our mutation analysis to 34 more unrelated FMEN1 probands and to two related states, sporadic MEN1 and familial hyperparathyroidism. There was a high prevalence of heterozygous germline MEN1 mutations in sporadic MEN1 (8/11 cases) and in FMEN1 (47/50 probands). One case of sporadic MEN1 was proven to be a new MEN1 mutation. Eight different mutations were observed more than once in FMEN1. Forty different mutations (32 FMEN1 and eight sporadic MEN1) were distributed across the MEN1 gene. Most predicted loss of function of the encoded menin protein, supporting the prediction that MEN1 is a tumor suppressor gene. No MEN1 germline mutation was found in five probands with familial hyperparathyroidism, suggesting that familial hyperparathyroidism often is caused by mutation in another gene or gene(s).

Fine-needle aspiration of metastatic clear cell carcinoma of the kidney: employment of microdissection and the polymerase chain reaction as a potential diagnostic tool

BACKGROUND

The differential diagnosis of metastatic clear cell carcinoma is broad. To date, there are no specific immunohistochemical markers for renal cell carcinoma (RCC) in general use. Loss of heterozygosity (LOH) at 3p25.5, the von Hippel-Lindau (VHL) gene locus, is frequent in sporadic clear cell RCC. The authors compared LOH in primary and metastatic RCC through microdissection and the polymerase chain reaction (PCR) to evaluate these techniques as potential diagnostic tools.

METHODS

The authors identified 14 patients with known clear cell RCC who underwent fine-needle aspiration (FNA) evaluation of presumed metastatic lesion. Direct-visualization microdissection was performed from archival histologic glass slides of the primary neoplasm and the adjacent normal kidney parenchyma. Malignant cell clusters were microdissected from archival FNA slides of metastatic lesions. The cytology slides were previously stained with either Diff-Quik or Papanicolaou stain. This was followed by a single-step DNA extraction and PCR amplification for evaluation of LOH using polymorphic markers, D3S1038 and D3S1110, flanking the VHL gene.

RESULTS

Thirteen of the 14 cases contained DNA suitable for PCR in both the paraffin embedded and the FNA material. Eight of the 13 cases were heterozygous (informative) for the above markers, and 6 of these showed identical allelic loss in the primary and metastatic tumor for either one or both of the markers used. The remaining two cases did not show LOH at the VHL locus with the two polymorphic markers used.

CONCLUSIONS

DNA from archival cytologic material stained with Papanicolaou stain or Diff-Quik is reliable for PCR amplification. Visually directed microdissection in combination with PCR has the potential to be a useful technique for confirmatory identification and diagnosis of metastatic clear cell RCC in cytologic material, because a specific genetic abnormality is present in the primary tumor. As characteristic genetic abnormalities are identified in various neoplasms, the use of this technique has the potential for conclusive evaluation of metastatic disease with FNA material, when used in comparison with surgical or cytologic material from the primary tumor. The utility of this combination of techniques has the potential for the molecular diagnosis of morphologically ambiguous cell populations.

Allelic deletions on chromosome 11q13 in multiple endocrine neoplasia type 1-associated and sporadic gastrinomas and pancreatic endocrine tumors

Endocrine tumors (ETs) of pancreas and duodenum occur sporadically and as a part of multiple endocrine neoplasia type 1 (MEN1). The MEN1 tumor suppressor gene has been localized to chromosome 11q13 by linkage analysis but has not yet isolated. Previous allelic deletion studies in enteropancreatic ETs suggested MEN1 gene involvement in tumorigenesis of familial pancreatic ETs (nongastrinomas) and sporadic gastrinomas. However, only a few MEN1-associated duodenal gastrinomas and sporadic pancreatic nongastrinomas have been investigated. We used tissue microdissection to analyze 95 archival pancreatic and duodenal ETs and metastases from 50 patients for loss of heterozygosity (LOH) on 11q13 with 10 polymorphic markers spanning the area of the putative MEN1 gene. Chromosome 11q13 LOH was detected in 23 of 27 (85%) MEN1-associated pancreatic ETs (nongastrinomas), 14 of 34 (41%) MEN1-associated gastrinomas, 3 of 16 (19%) sporadic insulinomas, and 8 of 18 (44%) sporadic gastrinomas. Analysis of LOH on 11q13 showed different deletion patterns in ETs from different MEN1 patients and in multiple tumors from individual MEN1 patients. The present results suggest that the MEN1 gene plays a role in all four tumor types. The lower rate of 11q13 LOH in MEN1-associated and sporadic gastrinomas and sporadic insulinomas as compared to MEN1 nongastrinomas may reflect alternative genetic pathways for the development of these tumors or mechanisms of the MEN1 gene inactivation that do not involve large deletions. The isolation of the MEN1 gene is necessary to further define its role in pathogenesis of pancreatic and duodenal ETs.

Localization of the multiple endocrine neoplasia type I (MEN1) gene based on tumor loss of heterozygosity analysis

Multiple endocrine neoplasia type I (MEN1) is an inherited syndrome that results in parathyroid, anterior pituitary, and pancreatic and duodenal endocrine tumors as well as foregut carcinoids in affected patients. The gene responsible for the disease has been linked to chromosome 11q13. We analyzed loss of heterozygosity (LOH) in 188 tumors from 81 patients in an attempt to further define the location of the MEN1 gene. Both tumors from MEN1 patients and corresponding sporadic tumors were analyzed. Tumor types included parathyroid, gastrinoma, pancreatic endocrine, pituitary, and lung carcinoid. Six tumors (three MEN1 and three sporadic tumors) were identified that provided important LOH boundaries. Four tumors (two parathyroid tumors, one gastrinoma, and one lung carcinoid tumor) showed allelic loss that placed the MEN1 gene distal to marker PYGM. Two tumors (one gastrinoma and one parathyroid tumor) showed an LOH boundary that placed the gene proximal to D11S449, one of which further moved the telomeric boundary to D11S4936. Taken together, the present data suggest that the MEN1 gene lies between PYGM and D11S4936, a region of approximately 300 kb on chromosome 11q13.

Loss of heterozygosity at 11q13: analysis of pituitary tumors, lung carcinoids, lipomas, and other uncommon tumors in subjects with familial multiple endocrine neoplasia type 1

Loss of heterozygosity (LOH) for polymorphic markers flanking the multiple endocrine neoplasia type 1 (MEN-1) gene in parathyroid and pancreatic islet tumors from subjects with familial MEN-1 (FMEN-1) has been well documented and has led to the hypothesis that the MEN-1 gene functions as a tumor suppressor. To assess the role of the MEN-1 gene in the pathogenesis of tumors less commonly associated with MEN-1, we employed a large number of highly informative polymorphic markers closely linked to the MEN-1 gene to study a series of 13 such tumors from subjects with FMEN-1 for LOH at 11q13. We were able to identify LOH for 1 or more 11q13 markers in 2 of 3 pituitary tumors, 3 lung carcinoids, and 1 of 2 lipomas. In every case studied, the allele lost represented the normal allele inherited from the unaffected parent. No LOH was detected in 3 skin angiofibromas, an esophageal leiomyoma, or a renal angiomyolipoma despite the presence of at least 2 informative markers for each tumor. Our results suggest that, like that for parathyroid and pancreatic islet tumors, the pathogenesis of pituitary tumors, lung carcinoids, and lipomas occurring in subjects with FMEN-1 probably involves loss of the normal tumor suppressor function of the MEN-1 gene. Our inability to detect 11q13 LOH in skin angiofibromas, leiomyoma, and angiomyolipoma from subjects with FMEN-1 is consistent with the possibility that these neoplasms arose independently by a mechanism unrelated to the MEN-1 gene, but a role for the MEN-1 gene in the pathogenesis of these tumors cannot be definitively excluded until the gene itself is identified and evaluated for small intragenic deletions or point mutations in such tumors.

Germline and somatic mutations in the tyrosine kinase domain of the MET proto-oncogene in papillary renal carcinomas

Hereditary papillary renal carcinoma (HPRC) is a recently recognized form of inherited kidney cancer characterized by a predisposition to develop multiple, bilateral papillary renal tumours. The pattern of inheritance of HPRC is consistent with autosomal dominant transmission with reduced penetrance. HPRC is histologically and genetically distinct from two other causes of inherited renal carcinoma, von Hippel-Lindau disease (VHL) and the chromosome translocation (3;8). Malignant papillary renal carcinomas are characterized by trisomy of chromosomes 7, 16 and 17, and in men, by loss of the Y chromosome. Inherited and sporadic clear cell renal carcinomas are characterized by inactivation of both copies of the VHL gene by mutation, and/or by hypermethylation. We found that the HPRC gene was located at chromosome 7q31.1-34 in a 27-centimorgan (cM) interval between D7S496 and D7S1837. We identified missense mutations located in the tyrosine kinase domain of the MET gene in the germline of affected members of HPRC families and in a subset of sporadic papillary renal carcinomas. Three mutations in the MET gene are located in codons that are homologous to those in c-kit and RET, proto-oncogenes that are targets of naturally-occurring mutations. The results suggest that missense mutations located in the MET proto-oncogene lead to constitutive activation of the MET protein and papillary renal carcinomas.

von Hippel-Lindau gene deletion detected in the stromal cell component of a cerebellar hemangioblastoma associated with von Hippel-Lindau disease

Central nervous system hemangioblastoma is a neoplasm with characteristic and well-described histopathological features, including proliferation of vascular and stromal cells. yet, the histogenesis of the stromal cell component and its neoplastic capacity as compared with the vascular component are still controversial. Stromal cells were selectively procured from formalin-fixed, paraffin-embedded archival tissue from a von Hippel-Lindau (VHL) disease patient with a cerebellar hemangioblastoma and studied for loss of heterozygosity (LOH) of the VHL gene locus and associated microsatellite regions. The stromal cells consistently showed LOH. Analysis of mixed stromal anti vascular areas of this tumor and four other hemangioblastomas of VHL patients showed that loss of heterozygosity was partially obscured. These preliminary results suggest that the stromal component of hemangioblastomas contains genetic alterations consistent with a neoplastic nature. Additional samples of pure stromal cells need to be analyzed to establish the prevalence of VHL gene deletion in stromal cells of capillary hemangioblastoma and, hence, its pathogenetic significance.

Molecular genetic events in the development and progression of ovarian cancer in humans

Ovarian tumor development is characterized by specific clinical and pathological features that provide an interesting model of carcinogenesis: first, the pre-invasive and even invasive lesions are difficult to detect; second, a group of cases with a known familial predilection constitute an important heredltary model of carcinogenesis; and third, the category of morphologically borderline ovarian tumors (tumors of low malignant potential) poses several unanswered questions such as: what histologic criteria should be used for their diagnosis; what is their natural history; and what is their molecular relationship to invasive tumors? Recently, molecular studies have contributed to a better understanding of the biology of these tumors, their behavior in vivo, and their response to therapy. This article summarizes the most recent molecular advances.