Evidence of independent origin of multiple tumors from patients with prostate cancer

BACKGROUND

In men with prostate cancer, the gland usually contains two or more widely separate tumors. A critical issue of prostatic carcinogenesis is whether these multiple tumors are independent in origin. Molecular analysis of microsatellite (i.e., highly repeated, short nucleotide sequences) alterations in the DNA from separate tumors in the same prostate can be used to determine whether or not these separate tumors arise independently.

METHODS

Four microsatellite polymorphic markers (D8S133, D8S136, and D8S137, for a putative tumor suppressor gene on chromosome 8p, and D17S855, for the BRCA1 gene on chromosome 17q) were used to examine the pattern of allelic loss in prostate cancer from 19 patients who had two or more distantly separate tumors (i.e., located on contralateral sides or separated by at least half the anterior-posterior diameter of the prostate). Forty distantly separate tumors were microdissected, DNA samples were prepared from formalin-fixed, paraffin-embedded wholemount prostate tissue section, and the overall frequencies of loss of heterozygosity at the four loci were determined.

RESULTS

The pattern of allelic loss was compatible with independent tumor origin in 15 of 18 informative cases. A random discordant pattern of allelic deletion was observed in distantly separate tumors, whereas the same allele was consistently lost in cells from different regions of the same tumor. For three patients, the results were compatible with either intraglandular dissemination or independent origin of prostate cancer.

CONCLUSIONS

Our data suggest that multiple tumors in some patients with prostate cancer have independent origin.

Allelic deletion at chromosome 9p21(p16) and 17p13(p53) in microdissected sporadic dysplastic nevus

A critical area of chromosomal loss at region p16(9p21-22) and p53(17p13) has been implicated in the genesis of malignant melanoma. It is still unclear whether the genetic alterations can be detected in dysplastic nevus, a premalignant lesion of malignant melanoma. We have searched the frequency of p16 and p53 deletion in nine dysplastic nevi and 13 benign intradermal nevi with five microsatellite markers. Hemizygous deletion was detected in seven of nine (78%) dysplastic nevi at one or more loci for p16 and three of seven (43%) for p53, respectively. No loss of heterozygosity (LOH) was detected in any of the benign intradermal nevi. All three dysplastic nevi with LOH for p53 also showed LOH at p16. However, not all dysplastic nevi showing p16 deletion showed p53 gene deletion. Therefore, these data suggest that deletion of p16 may play an important role in the development of dysplastic nevus as an early event and that the changes may represent an early event in the development of malignant melanoma.

11q13 allelotype analysis in 27 northern American MEN1 kindreds identifies two distinct founder chromosomes

We analyzed constitutional and tumor DNA from 27 MEN1 kindreds not known to be related to each other. Disease allele haplotypes were constructed for each pedigree based on shared alleles from two or more affected members and from determination of allelic loss patterns in their tumors. Analysis of disease allele haplotypes showed unexpected linkage disequilibrium at marker PYGM. Further haplotype analysis indicated this could be explained by the presence of two founder chromosomes, one in four families, the other in three. A shared disease haplotype was not observed among two MEN1 kindreds with the prolactinoma phenotype of MEN1.

Mutations of the MEN1 tumor suppressor gene in pituitary tumors

Although pituitary adenomas are monoclonal proliferations, somatic mutations involving genes that govern cell proliferation or hormone production have been difficult to identify. The genetic etiology of most pituitary tumors, therefore, remains unknown. Pituitary adenomas can develop sporadically or as a part of multiple endocrine neoplasia type 1 (MEN1). Recently, the gene responsible for MEN1 was cloned. To elucidate the potential etiological role of the MEN1 gene in pituitary tumorigenesis, 39 sporadic pituitary adenomas from 38 patients and 1 pituitary adenoma from a familial MEN1 patient were examined for MEN1 gene mutations and allelic deletions. Four of 39 sporadic pituitary adenomas showed a deletion of one copy of the MEN1 gene, and a specific MEN1 gene mutation in the remaining gene copy was detected in 2 of these tumors. The corresponding germ-line sequence was normal in all sporadic cases. A specific MEN1 mutation was detected in a pituitary adenoma and corresponding germ-line DNA in a patient with familial MEN1. An allelic deletion of the remaining copy of the MEN1 gene was also found in the patient's tumor. Genetic alterations of the MEN1 gene represent a candidate pathogenetic mechanism of pituitary tumorigenesis. The data suggest that somatic MEN1 gene mutations and deletions play a causative role in the development of a subgroup of sporadic pituitary adenomas.

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.

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.

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.

Defective placental vasculogenesis causes embryonic lethality in VHL-deficient mice

Inheritance of an inactivated form of the VHL tumor suppressor gene predisposes patients to develop von Hippel-Lindau disease, and somatic VHL inactivation is an early genetic event leading to the development of sporadic renal cell carcinoma. The VHL gene was disrupted by targeted homologous recombination in murine embryonic stem cells, and a mouse line containing an inactivated VHL allele was generated. While heterozygous VHL (+/-) mice appeared phenotypically normal, VHL -/- mice died in utero at 10.5 to 12.5 days of gestation (E10.5 to E12.5). Homozygous VHL -/- embryos appeared to develop normally until E9.5 to E10.5, when placental dysgenesis developed. Embryonic vasculogenesis of the placenta failed to occur in VHL -/- mice, and hemorrhagic lesions developed in the placenta. Subsequent hemorrhage in VHL -/- embryos caused necrosis and death. These results indicate that VHL expression is critical for normal extraembryonic vascular development.

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.

A transcript map for the 2.8-Mb region containing the multiple endocrine neoplasia type 1 locus

Multiple endocrine neoplasia type 1 (MEN 1) is an inherited cancer syndrome in which affected individuals develop multiple parathyroid, enteropancreatic, and pituitary tumors. The locus for MEN1 is tightly linked to the marker PYGM on chromosome 11q13, and linkage analysis places the MEN1 gene within a 2-Mb interval flanked by the markers D11S1883 and D11S449. Loss of heterozygosity studies in MEN 1 and sporadic tumors suggest that the MEN1 gene encodes a tumor suppressor and have helped to narrow the location of the gene to a 600-kb interval between PYGM and D11S449. Focusing on this smaller MEN1 interval, we have identified and mapped 12 transcripts to this 600-kb region. A precise ordered map of 33 transcripts, including 12 genes known to map to this region, was generated for the 2.8-Mb D11S480-D11S913 interval. Fifteen candidate genes (of which 10 were examined exhaustively) were evaluated by Southern blot and/or dideoxy fingerprinting analysis to identify the gene harboring disease-causing mutations.

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.

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.

Positional cloning of the gene for multiple endocrine neoplasia-type 1

Multiple endocrine neoplasia-type 1 (MEN1) is an autosomal dominant familial cancer syndrome characterized by tumors in parathyroids, enteropancreatic endocrine tissues, and the anterior pituitary. DNA sequencing from a previously identified minimal interval on chromosome 11q13 identified several candidate genes, one of which contained 12 different frameshift, nonsense, missense, and in-frame deletion mutations in 14 probands from 15 families. The MEN1 gene contains 10 exons and encodes a ubiquitously expressed 2.8-kilobase transcript. The predicted 610-amino acid protein product, termed menin, exhibits no apparent similarities to any previously known proteins. The identification of MEN1 will enable improved understanding of the mechanism of endocrine tumorigenesis and should facilitate early diagnosis.

Molecular analysis of synchronous uterine and ovarian endometrioid tumors

The presence of simultaneous carcinomas involving both the ovary and uterine corpus presents a diagnostic challenge, particularly if the tumors have a similar histology. The classification of these lesions as either two separate primary tumors, or as a single primary tumor with a metastasis has significant implications with respect to patient prognosis and recommendations for therapy. Although several morphologic criteria have been proposed as guidelines for the classification of these lesions, certain cases remain difficult to confidently classify. The application of current molecular biology techniques to pathological specimens can provide genetic information than can be helpful in establishing the relationship between synchronous neoplasms. Specifically, the use of tissue microdissection and polymerase chain reaction (PCR) amplification of DNA can be helpful. In this study we used polymorphic DNA markers on chromosomes 17q21.3-22 and 11q13 to study loss of heterozygosity (LOH) in 13 patients who presented with endometrioid tumors in both the uterus and ovary. Ten of the 13 cases showed LOH in one or both tumors. In eight of the 13 cases the detected LOH either chromosome 17q21.3-22 or 11q13 occurred selectively in only one of the two tumor sites. The results of this study suggest that the eight cases with LOH selective for one tumor site represent patients with two separate primary tumors. Molecular analysis may be useful in determining the relationship of synchronous uterine and ovarian endometrioid neoplasms.

Haplotype analysis defines a minimal interval for the multiple endocrine neoplasia type 1 (MEN1) gene

Multiple endocrine neoplasia type 1 (MEN1) is an inherited syndrome characterized by development of multiple endocrine tumors in affected individuals. The gene responsible for the disease has been mapped to chromosome 11q13 by linkage analysis, but the gene itself has not yet been identified. We allelotyped 33 affected individuals from an extensive MEN1 kindred using eight polymorphic markers located on chromosome 11q13, including two new markers (D11S4907 and D11S4908) that we derived and mapped to the SEA-D11S913 region. Analysis of affected individuals revealed two separate recombination events, providing new centromeric and telomeric boundaries for the MEN1 gene. The present data indicate the MEN1 gene is located between markers D11S1883 and D11S4907, an approximate 2 Mb region on chromosome 11q13.

Generation and genetic characterization of immortal human prostate epithelial cell lines derived from primary cancer specimens

Difficulty in establishing long-term human prostate epithelial cell lines has impeded efforts to understand prostate tumorigenesis and to develop alternative therapies for prostate cancer. In the current study, we describe a method that was successful in generating 14 immortal benign or malignant prostate epithelial cell cultures from primary adenocarcinomas of the prostate resected from six successive patients. Immortalization with the E6 and E7 transforming proteins of human papilloma virus serotype 16 was necessary to establish long-term cultures. Microscopic examination of fresh tumor specimens exhibited a variable mixture of benign and malignant epithelium. Thus, single-cell cloning of tumor-derived cell cultures was essential for defining tumor cell lines. Efforts to characterize these cultures using traditional criteria such as karyotype, growth in nude mice, and prostate-specific antigen expression were noninformative. However, allelic loss of heterozygosity (LOH) represents a powerful alternative method for characterizing tumor cell lines originating from primary adenocarcinomas of the prostate. Microdissected fresh tumors from four of six patients revealed LOH at multiple loci on chromosome 8p, as assessed by PCR. LOH on chromosome 8p matching the patterns found in microdissected tumors was also observed in a tumor-derived cell line and its clones, as well as in one clone from a tumor-derived cell line from a second patient. LOH was not observed in immortal lines generated from autologous benign prostatic epithelium, seminal vesicle epithelium, or fibroblasts. The multifocal nature of prostate cancer, as well as the presence of an entire spectrum of malignant transformation within individual prostate glands, necessitates this type of careful analysis of derivative cell cultures for their validation as in vitro models that accurately reflect the primary cancers from which they are derived.

Analysis of loss of heterozygosity on chromosome 11q13 in atypical ductal hyperplasia and in situ carcinoma of the breast

Identical allelic loss in invasive and adjacent in situ ductal breast carcinoma (DCIS) on chromosome 11q13 has been previously reported, providing molecular evidence for the progression of DCIS to invasive tumor. In this study we analyzed loss of heterozygosity (LOH) on 11q13 (PYGM, INT-2) in atypical ductal hyperplasia (ADH) and various histological types of in situ carcinomas of the breast in patients without invasive cancer. Twenty-four cases of in situ carcinoma and twelve cases of ADH were studied. Tissue microdissection of normal, hyperplastic, and tumor cells from fixed, paraffin-embedded sections was performed, and DNA was extracted for polymerase chain reaction. In situ tumors included both high- and low-grade DCIS. LOH was identified in six of twenty-two (27.3%) in situ tumors and in one of eleven (9%) ADH cases. Within in situ carcinomas, LOH was identified in six of seventeen (35%) high-grade DCIS but in none of six low-grade DCIS. The present results show that LOH at 11q13 occurs in an appreciable proportion of high-grade DCIS, although the rate is substantially less than in patients with concomitant DCIS and invasive tumor. LOH was identified less frequently in low-grade in situ tumors and ADH, suggesting that a putative tumor suppressor gene(s) located on chromosome 11q13 may be involved in the transition from early preneoplastic lesions to invasive breast cancer.

Construction of a representative cDNA library from prostatic intraepithelial neoplasia

We report the construction of a plasmid-based cDNA library made from microdissected cells derived from prostatic intraepithelial neoplasia. Total RNA was extracted and converted to blunt-ended, double-stranded cDNA by oligo(dT)-mediated reverse transcription followed by linker addition. A linker-specific primer with UDG-compatible ends was used to amplify the cDNA and the resulting PCR product was subcloned. A total of 154 clones were sequenced and results indicated that 81.5% of the clones derived from either known genes, anonymous expressed sequence tags, or novel transcripts with very little redundancy of screened clones. These results demonstrate the feasibility of constructing complex representative cDNA libraries from specific microdissected cell populations that represent microscopic precursor stages of cancer progression. This method should facilitate identification of transcripts specifically expressed in cells of a distinct histological origin and tumorigenic stage.

Allelic deletions on chromosome 11q13 in multiple tumors from individual MEN1 patients

Familial multiple endocrine neoplasia type 1 is an autosomal dominant hereditary disorder characterized by multiple parathyroid, pancreatic, duodenal, and pituitary tumors. The parathyroid tumors may arise as diffuse areas of hyperplasia, whereas the pancreatic and duodenal tumors usually form as discrete nodules. Except for a single report, tumor loss of heterozygosity (LOH) mapping of the putative MEN1 suppressor gene on chromosome 11q13 in the past has been restricted by analysis of a single tumor from individual patients and somatic cellular contamination. For this reason, it has not been possible to analyze the clonality of the emerging MEN1 neoplasms. Furthermore, it has been previously unknown whether the LOH pattern varies between individual MEN1 tumors in a given patient or among tumors of different histological origins within unrelated patients. To address these previous limitations, the present study introduces a refinement in microdissection in which endothelial cells are stained and selectively excluded. Tissue microdissection was applied to study LOH patterns on chromosome 11q13 using 8 polymorphic DNA markers in 44 different MEN1 tumors from parathyroid, pancreas, and duodenum in nine unrelated patients. In addition, X-chromosome inactivation clonal analysis was applied to 16 individual microdissected regions from seven parathyroid glands in three female patients. The LOH rates of parathyroid lesions (100%) and endocrine tumors of the pancreas (83%) were strikingly different from the LOH rate of gastrinomas (21%), suggesting that the mechanism that drives LOH may be influenced by the tissue context. Moreover, combined LOH and X-chromosome inactivation scoring of the same microdissected region revealed that parathyroid MEN1 neoplasms can consist of more than one clone. In this study, the centromeric boundary of the putative MEN1 gene was PYGM. Analysis of differential LOH patterns in multiple microdissected tumors in the same patient constitutes a novel approach to suppressor gene mapping.