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.

Monoclonal origin of multicentric Kaposi's sarcoma lesions

BACKGROUND

Kaposi's sarcoma has features of both hyperplastic proliferation and neoplastic growth. Multiple lesions, in which spindle cells are prominent, often arise synchronously over widely dispersed areas. We tested the hypothesis that the spindle cells in these multicentric lesions originate from a single clone of precursor cells.

METHODS

To determine whether Kaposi's sarcoma is a monoclonal disorder, we assessed the methylation patterns of the androgen-receptor gene (HUMARA) in multiple lesions from women with the acquired immunodeficiency syndrome. In polyclonal tissues, about half the copies of each HUMARA allele are methylated, whereas in cells derived from a single clone all the copies of only one allele are methylated. To minimize contamination by normal DNA, we used microdissection to isolate areas composed primarily of spindle cells, the putative tumor cells.

RESULTS

Eight patients with a total of 32 tumors were studied. Of these tumors, 28 had highly unbalanced methylation patterns (i.e., predominant methylation of one HUMARA allele). In all the tumors that had unbalanced methylation from a given patient, the same allele predominated.

CONCLUSIONS

These data indicate that Kaposi's sarcoma is a disseminated monoclonal cancer and that the changes that permit the clonal outgrowth of spindle cells occur before the disease spreads.

Loss of heterozygosity on the short arm of chromosomes 1 and 3 in sporadic pheochromocytoma and extra-adrenal paraganglioma

Pheochromocytomas and extra-adrenal paragangliomas are tumors of the paraganglia with similar histological characteristics. We examined 12 sporadic pheochromocytomas and 5 extra-adrenal paragangliomas for loss of heterozygosity (LOH) in chromosomes 1p and 3p using a microdissection technique. Chromosomes 1p34-36, 3p21 and the von Hippel-Lindau (VHL) gene locus (3p25) were analyzed. LOH of a selected region on chromosome 1p was detected in 5 of 11 (45%) informative pheochromocytoma cases and in 0 of 5 (0%) informative extra-adrenal paraganglioma cases. LOH of the chromosome 3p25 VHL gene locus was detected in 5 of 9 (45%) informative pheochromocytoma cases and in 0 of 3 (0%) informative extra-adrenal paraganglioma cases. LOH of 3p21 was detected in 2 of 4 (50%) informative extra-adrenal paraganglioma cases. The allelic deletions in chromosomes 1p and 3p appear to be separate events. In conclusion, significant deletions were found at 1p34-36 and 3p25 in sporadic pheochromocytomas but not in extra-adrenal paragangliomas. These findings suggest (1) that multiple genetic factors may be involved in pheochromocytoma tumorigenesis, and (2) extra-adrenal paragangliomas may have a different genetic mechanism of tumorigenesis compared with pheochromocytomas.

Identical clonality of both components of mammary carcinosarcoma with differential loss of heterozygosity

The histogenesis of carcinosarcomas is controversial, specifically with respect to clonality and cell of origin. To answer these questions, tumor cells from both epithelial and spindle-cell components were microdissected from three cases each of mammary carcinosarcoma and its postulated precursor, carcinoma with spindle-cell metaplasia. Clonality was assessed using the principle of X chromosome inactivation. Loss of heterozygosity (LOH) was evaluated at seven chromosomal loci to assess shared and distinctive genetic alterations for the two components in each tumor. All of the six cases demonstrated identical clonality of the carcinomatous and spindle-cell components, identical to a focus of ductal carcinoma in situ present in one case. LOH for NM23 was detected in both components in one carcinosarcoma, whereas LOH for INT-2 was detected in both components in one metaplastic carcinoma. Differential LOH for D11S904 was present in only the mesenchymal components of these two cases. We conclude that the two components of carcinosarcoma and its precursor are clonal and that the sarcomatous and spindle-cell components arise from mutation of the carcinoma. Presence of differential LOH at D11S904 in only the spindle-cell components suggests that this mutation might be critical to the development of this second phenotype.

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.

Loss of heterozygosity on chromosome 11q13 in lobular lesions of the breast using tissue microdissection and polymerase chain reaction

Demonstration of identical allelic loss on chromosome 11q13 in synchronous in situ (DCIS) and invasive ductal (IDC) breast carcinoma has provided molecular evidence of the progression of DCIS to IDC. We investigated loss of heterozygosity (LOH) at chromosome 11q13 in the spectrum of "marker/premalignant" and "malignant" lobular lesions of the breast, including atypical lobular hyperplasia (ALH), lobular carcinoma in situ (LCIS), and infiltrating lobular carcinoma (ILC). Thirty-eight cases with various combinations of ALH, LCIS, and ILC were studied. Synchronous ductal lesions were present in 9 of 38 cases. Areas of interest were specifically isolated by tissue microdissection. The extracted DNA was amplified by polymerase chain reaction (PCR) and analyzed with two polymorphic markers for chromosome 11q13 (INT2 and PYGM). LOH at 11q13 was identified in ILC and LCIS in approximately one third of informative cases. LCIS in association with ILC showed a loss in 50% of cases, whereas pure LCIS in the absence of ILC had a much lower frequency of LOH, which was comparable to that of pure ALH. These results suggest that LOH on chromosome 11q13 may play an important role in development of ILC, similar to that of IDC from DCIS/ADH. Additionally, frequent LOH in ILC and LCIS associated with ILC and a significantly lower and comparable frequency of LOH in LCIS without ILC and ALH implies that genetic alteration(s) on chromosome 11q13 may be important in the transition of LCIS to ILC. LOH was detected in three of nine synchronous ductal lesions (one IDC and two DCIS), confirming our earlier findings and indicating that lobular and ductal neoplasia in the breast show some similar genetic changes. We hypothesize that LOH may help in separating morphologically similar yet genetically different subgroups of ALH and LCIS into one group with genetic changes and an increased potential to progress to invasive cancer and another group, the "marker" lesions of LCIS/ALH, that remain stable or possibly regress.

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.

Allelic deletions of the VHL gene detected in multiple microscopic clear cell renal lesions in von Hippel-Lindau disease patients

Patients with von Hippel-Lindau (VHL) disease develop a spectrum of bilateral clear-cell renal lesions including cysts and renal cell carcinomas (RCCs). VHL gene deletions have been previously reported in VHL-associated macroscopic RCC. Although histological analysis suggests that microscopic cystic lesions in the VHL patients may represent precursors of the RCC, there is at present no direct molecular evidence of their relationship. To investigate the relationship between cystic lesions and RCC, 26 microdissected archival renal lesions from two VHL disease patients were studied for loss of heterozygosity at the VHL gene locus using polymerase chain reaction single-strand conformation polymorphism analysis. The renal lesions included 2 benign cysts, 5 atypical cysts, 5 microscopic RCCs in situ, 5 cysts lined by a single layer of cells, in which RCCs in situ were developing, and 2 microscopic and 7 macroscopic RCCs. Except for a single benign cyst, 25 of 26 renal lesions showed nonrandom allelic loss of the VHL gene. In either of the 2 patients, the same VHL allele was deleted in all of the lesions tested, indicating loss of the wild-type allele and retention of the inherited, mutated VHL allele. The results suggest that all clear-cell lesions in the VHL kidney represent neoplasms and that the loss of the VHL gene occurs early in their development. Atypical and benign cysts most likely represent the initial phenotype in malignant transformation to the RCC.

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.

Laser capture microdissection

Laser capture microdissection (LCM) under direct microscopic visualization permits rapid one-step procurement of selected human cell populations from a section of complex, heterogeneous tissue. In this technique, a transparent thermoplastic film (ethylene vinyl acetate polymer) is applied to the surface of the tissue section on a standard glass histopathology slide; a carbon dioxide laser pulse then specifically activates the film above the cells of interest. Strong focal adhesion allows selective procurement of the targeted cells. Multiple examples of LCM transfer and tissue analysis, including polymerase chain reaction amplification of DNA and RNA, and enzyme recovery from transferred tissue are demonstrated.

Detection of von Hippel-Lindau disease gene mutations in paraffin-embedded sporadic renal cell carcinoma specimens

The von Hippel-Lindau (VHL) disease gene on chromosome 3p25.5 has been cloned and shown to be mutated in the germline DNA of patients with VHL disease. In addition, approximately 60% of sporadic renal cell carcinomas (RCCs) have been shown to have a VHL gene mutation in fresh frozen tumor tissue and tumor-derived cell lines. The objective of this study was to test whether VHL gene mutations could be detected in archival sporadic RCC cases. We studied three sporadic RCCs, two oncocytomas, and the corresponding adjacent normal renal parenchyma by polymerase chain reaction and single-strand conformation polymorphism analysis using paraffin-embedded, formalin-fixed material. Tumor and normal tissue were microdissected from eosin-stained 5-microns-thick histologic sections. Mutations in exon 2 of the VHL gene were detected in all three of the sporadic RCCs but were not observed in the matched normal renal tissues or in the two oncocytomas tested. The mutations were identical to those detected in tumor cell lines from the same patients. This report represents the first detection of VHL gene mutations in sporadic RCCs in archival, paraffin-embedded tissue. A high percentage of sporadic RCCs show VHL gene mutations in fresh frozen tissue but the availability of frozen material is limited, so the evaluation of archival tumors for similar mutations should prove useful in future RCC studies. Furthermore, the results suggest that the genetic events leading to the development of clinically benign renal oncocytoma may differ from those leading to malignant RCC.

Detection of heterozygosity loss in microdissected fine needle aspiration specimens of breast carcinoma

OBJECTIVE

To use the polymerase chain reaction (PCR) to detect loss of heterozygosity (LOH) in microdissected cells form cytologic smears obtained by fine needle aspiration (FNA) from 20 cases of invasive breast carcinoma.

STUDY DESIGN

In each case, histologic sections of the primary tumor were also available. Tumor and nontumor cells were dissected from both the cytologic smear and tissue section in all cases except in three smears that showed only tumor cells.

RESULTS

LOH was identified in 10 of 19 informative cases using two polymorphic DNA markers at chromosome 11q13 (INT-2, PYGM). The same results were obtained in both the cytologic and histologic specimens, including three cases that had hypocellular cytologic smears.

CONCLUSION

FNA of breast lesions provides adequate samples for direct microdissection of the cytologic smear to detect LOH using PCR amplification.

Preconcentration of trace elements from natural water with palladium precipitation

Palladium salts can be used as a coprecipitation carrier for the preconcentration of trace elements from natural water prior to their measurement by atomic spectrometry (AAS). The palladium is subsequently reduced by the introduction of hydrogen gas into the sample solution. The procedure is applied to the determination of Cu, Pb and Cd in seawater (enrichment factor 50) and synthetic water samples. Operating conditions have been optimized for the analysis of real samples. With the technique established an enrichment factor (500 fold) is feasible in synthetic samples. The recoveries of Cu, Cd and Pb from seawater are 95, 103 and 100%, respectively. This simple and rapid method can be applied in a wide pH-range and with complex matrices.

Barrett's esophagus: metaplastic cells with loss of heterozygosity at the APC gene locus are clonal precursors to invasive adenocarcinoma

Adenocarcinoma in Barrett's esophagus is the second most rapidly increasing cancer in western society. The cause and pathogenesis are unknown. Although histological studies suggest that there is successive progression from metaplasia and dysplasia, with a high risk of subsequent invasive carcinoma, at present there is no direct evidence that metaplastic and dysplastic epithelia are clonal precursors of adenocarcinoma. We selected 12 esophagectomy specimens of Barrett's esophagus patients, which showed a spectrum of normal tissue, metaplasia, dysplasia, and invasive carcinoma in each individual biopsy. We applied the microdissection technique to selectively procure microscopic tissue samples from H&E-stained slides for genetic evaluation using polymorphic markers flanking the APC gene locus. Identical APC gene alterations were found in the dysplastic and adenocarcinoma foci of all informative cases. The same changes were observed even in some metaplastic foci adjacent to dysplasia. Furthermore, clonality analysis of X-chromosome inactivation in female cases verified the same X-chromosome inactivation pattern in carcinoma, dysplasia, and metaplasia adjacent to dysplasia. No APC gene alterations were found in the normal epithelium and metaplasia distant from dysplasia. These data show for the first time that a tissue field of genotypic changes precedes the histopathological phenotypic changes of carcinoma in Barrett's esophagus syndrome. Our findings, in conjunction with the applied tissue microdissection technique, may help identify genotypic changes in patients with Barrett's esophagus before phenotypic changes occur. Therefore, genotyping of Barrett's metaplastic epithelium may supplement the histopathological evaluation of Barrett's esophagus.

Ca2+ transport processes of lobster hepatopancreatic brush-border membrane vesicles

45Ca2+ uptake by hepatopancreatic brush-border membrane vesicles of Atlantic lobster (Homarus americanus) occurred by a combination of three independent processes: (1) an amiloride-sensitive carrier-mediated transport system; (2) an amiloride-insensitive carrier-mediated transport system; and (3) a verapamil-inhibited channel process responsive to transmembrane potential. Both carrier-mediated processes were antiporters and capable of exchanging external Ca2+ with intravesicular Na+ or H+. The kinetic parameters of both carrier-mediated processes have been reported previously. External amiloride and Zn2+ were both competitive inhibitors of 45Ca2+ influx, reducing entry of the divalent cation at a single binding site with Ki values of 370 µmol l-1 for amiloride and 940 µmol l-1 for Zn2+. It is concluded that the mechanisms controlling Ca2+ entry into hepatopancreatic epithelial cells include a previously reported electrogenic 2Na+/1H+ antiporter, an electroneutral 2Na+/1Ca2+ antiporter and a verapamil-sensitive Ca2+ channel, which might also be used for the entry of Zn2+ and possibly other heavy metals. Evidence from an equilibrium-shift experiment, based on the thermodynamics of a coupled transport process, suggested that both monovalent (Na+) and divalent (Ca2+ and Zn2+) cations may enter hepatopancreatic epithelial cells through a common carrier-mediated transport protein. This suite of hepatopancreatic brush-border Ca2+ transport processes qualitatively resembles that previously reported for the luminal membrane of lobster antennal glands and suggests that crustacean epithelial cells from different organs may handle this divalent cation by similar means.

von Hippel-Lindau disease gene deletion detected in microdissected sporadic human colon carcinoma specimens

The progression of human malignancies is thought to involve the inactivation or loss of tumor suppressor genes. Previous studies have suggested that inactivation of tumor suppressor genes on chromosomes 5q, 17p, 18q, and 8p play a role in the development of colorectal carcinoma. However, chromosome 3p at the von Hippel-Lindau disease (VHL) gene locus (3p25-26) has not been previously implicated in the development or progression of sporadic colorectal carcinoma. The authors have analyzed VHL gene alterations on chromosome 3p in sporadic human colon carcinomas and adenomas using modified microdissection techniques. These techniques allow for procurement and analysis of selected subpopulations of cells from both paraffin-embedded and frozen human tumor specimens. VHL disease gene deletion was detected by polymerase chain reaction (PCR) and single-strand conformation polymorphism (SSCP) analysis in microdissected colon carcinoma specimens. Allelic loss of VHL gene was detected in 7 of 11 (64%) informative patients who underwent colectomy for primary sporadic colon carcinoma. However, no allelic loss of VHL gene was shown in colonic adenomas of eight informative patients. These results indicate that VHL disease gene deletion frequently occurs in sporadic colon carcinoma. Because this deletion was not present in adenomas, VHL gene may play a role in colonic carcinogenesis and represent a relatively late event in colonic neoplasia progression. Additionally, microdissection of tissue sections may be especially useful in detecting allelic loss in PCR-based studies of infiltrating tumors, particularly when the tumor cells represent a relatively small percentage of the total cell population.

Field performance measurements of half-facepiece respirators--foundry operations

A series of field studies was conducted to measure workplace protection factors (WPF) provided by elastomeric and disposable half-facepiece respirators against different particulate contaminants. The research protocol developed for the study has been described in a previous article. This article presents results from dust and fume exposures at three foundries. The major components of the airborne exposures in these foundries were zinc, lead, and silicon. The major components of the in-facepiece samples were zinc, chlorine, and lead. Significant differences were observed in ambient zinc and lead concentration levels among foundries; however, no significant difference was observed in the in-facepiece concentrations of these elements among foundries. Respirator performance varied within each foundry, but there was no difference in performance when pooling all foundry data. The 5th, 10th and 50th percentile estimates for the pooled foundry and respirator WPF data were about 9, 16, and 114 respectively. The infacepiece concentration data clearly indicate that dust-fume-mist (DFM) class half-facepiece respirators, when conscientiously used, worn, and maintained, in conjunction with other existing controls in these foundries, provided effective worker protection.

Genetic analysis of synchronous mucinous tumors of the ovary and appendix

The coexistence of mucinous ovarian and appendiceal tumors in association with pseudomyxoma peritonei (PP) is well established. However, it has not been determined whether they represent independent or metastatic neoplasms. The authors analyzed microsatellites on chromosome 17q 21.3-22 (nm23), 3p 25-26 (von Hippel Lindau disease [VHL] gene), and 5q 21-22 (D5S346 locus) in 12 synchronous ovarian and appendiceal mucinous lesions. Loss of heterozygosity (LOH) at the nm23 locus has been shown previously in ovarian carcinomas, and genetic alterations at both the 3p and 5q loci have been reported in colorectal carcinomas. The ovarian lesions consisted of nine mucinous tumors of low malignant potential and three invasive adenocarcinomas, and the appendiceal lesions consisted of eight carcinomas without invasion, two invasive carcinomas, and two mucosal hyperplasias. DNA was extracted from microdissected cells obtained from formalin-fixed, paraffin-embedded tissue sections and amplified by polymerase chain reaction. In three specimens, genetic alterations occurred at 17q 21.3-22 in only the ovarian tumors. One of these cases showed LOH on chromosome 5q 21-22 in only the appendiceal tumor. In three other specimens, LOH at the same locus was found in both tumors. Six specimens did not show LOH at any locus. These results suggest that a subset of synchronous mucinos ovarian and appendiceal lesions showing different LOH patterns in both sites most likely represent patients with two separate primary lesions. Another group of specimens with the same allelic loss in both tumors most likely represent patients with a single primary and metastatic spread. Thus, genetic analysis of these lesions may be useful in investigating the origin of histologically similar synchronous tumors.

Loss of heterozygosity on the short arm of chromosome 8 in male breast carcinomas

Identification of loss of heterozygosity (LOH) at specific genetic loci in neoplastic cells suggests the presence of a tumor suppressor gene within the deleted region. LOH on chromosome 8p has been identified in colorectal, bladder, hepatocellular, and prostatic carcinomas. Little is currently known about the molecular events occurring during the development of male breast cancer. We studied LOH on chromosome 8p in 23 male breast carcinomas. Five polymorphic DNA markers were used: D8S136 and D8S137 on 8p12-21.3; and D8S254, D8S258, and D8S349 on 8p22. DNA was extracted from microdissected normal and tumor cells obtained from formalin-fixed, paraffin-embedded tissue sections and amplified by the PCR. LOH was identified in 19 of 23 cases (83%) with at least one marker. Seven cases showed LOH only at 8p22, six cases showed LOH only at 8p12-21.3, and six cases showed LOH at both 8p22 and 8p12-21.3. In five of these last six cases, at least one locus was retained between the two deleted regions; thus, the whole short arm of chromosome 8 was not lost in these tumors. Our results show that there are two discrete areas of deletion on chromosome 8p in male breast cancer, suggesting the presence of one or more tumor suppressor genes that may play a role in the development or progression of the disease.