Loss of heterozygosity at 7q31 is a frequent and early event in prostate cancer

It is widely accepted that an accumulation of genetic alterations plays an important role in the genesis of human cancers, but little is known about prostate cancer in this respect. Recent studies have identified regions on chromosome arms 8p, 10q, 16q, and 18q that are frequently deleted in human prostate cancer. We have previously described a loss of heterozygosity (LOH) at the Met locus on chromosome band 7q31 in a study of 20 localized prostate tumors. To determine whether a region on the 7q arm is important in the initiation and/or progression of prostate cancer, prostate tissue from 13 patients with confined prostate tumors, 17 with local extracapsular extension, and 13 with metastatic forms were analyzed for LOH, using a DNA probe for RFLP (pMetH) and 8 CA microsatellite repeats (7 on 7q21-q33 and 1 on 7p). Twenty (47%) of the 43 cases studied showed LOH at one or more 7q loci. The most frequently deleted region was chromosome 7q31.1-7q31.2, whereas the centromeric locus on 7q21 was generally conserved. The percentage of LOH was normally distributed around the D7S480 locus. Moreover, the rate of LOH in the 7q31 region was lower in metastatic tumors than in localized tumors. These results strongly suggest the presence of a tumor suppressor gene on the chromosome band 7q31 with an important role in the early stages of prostate cancer.     

Comprehensive allelotyping of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers in many parts of the world, however the molecular mechanisms underlying liver cell transformation remain obscure. A genome-wide scan of loss of heterozygosity (LOH) in tumors provides a powerful tool to search for genes involved in neoplastic processes. To identify recurrent genetic alterations in liver tumors, we examined DNAs isolated from 120 HCCs and their adjacent non tumorous parts for LOH using a collection of 195 microsatellite markers located roughly every 20 cM throughout 39 autosomal arms. The mean heterozygosity was 73%. Our findings provide additional support that LOH for loci on chromosomal arms 1p, 4q, 6q, 8p, 13q and 16p is significantly elevated in HCC. The highest percentage of LOH is found for a locus in 8p23 (42% of informative csaes). This corresponds to one of the most common genetic abnormalities reported to date in these tumors. In addition, high ratio of LOH (> or = 35%) is observed on chromosome arms which had not been implicated in previous studies, notably on 1q, 2q and 9q. No correlation was found between LOH of specific chromosomal regions and etiologic factors such as chronic infections with hepatitis B or C viruses. This first report of an extensive allelotypic analysis of HCC should help in identifying new genes whose loss of function contributes to the development of liver cancer.     

Genetic alteration mapping on chromosome 7 in primary breast cancer

Alterations of chromosome 7 are among the most frequent cytogenetic abnormalities found in human breast carcinoma. We examined genetic changes on chromosome 7 in 113 primary human breast tumors, using both microsatellite and restriction fragment length polymorphism/variable number of tandem repeats polymorphism markers mapping to the long arm (15 markers) and the short arm (8 markers). Allelic imbalance at 1 or more loci was observed in 50 (44%) of 113 tumors on the long arm of chromosome 7 and in 41 (36%) tumors on the short arm. Genetic changes of one arm were significantly associated with alterations of the other arm. The 50 7q-altered tumor DNAs exclusively showed a loss of heterozygosity (LOH), 23 (46%) at all informative loci tested on 7q and 27 (54%) at some loci (interstitial and/or telomeric deletions on 7q). The pattern of LOH of these 27 tumors enabled us to identify 3 distinct consensus regions of deletions on 7q, only 1 of which (7q31 region) has already been described in breast cancer. Among the 41 7p-altered tumor DNAs, 32 had a gain and/or loss of the entire short arm of chromosome 7. Fourteen tumor DNAs showed an allelic gain, and 18 tumor DNAs showed a LOH at each locus on the short arm. The other 9 7p-altered tumors showing partial random alterations of chromosome 7p revealed no common altered regions. This is the first report of an association between alterations of DNA sequences on chromosome 7p and breast cancer. The results suggest that tumor suppressor genes are present on the long arm of chromosome 7 and are associated with breast tumorigenesis. Moreover, the frequent loss or gain of a whole copy of chromosome 7p suggests the involvement of a gene dosage effect of this chromosomal arm in the pathogenesis of breast cancer.     

Allelotype analysis of oesophageal adenocarcinoma: loss of heterozygosity occurs at multiple sites

Deletions of tumour-suppressor genes can be detected by loss of heterozygosity (LOH) studies, which were performed on 23 cases of adenocarcinoma of the oesophagus, using 120 microsatellite primers covering all non-acrocentric autosomal chromosome arms. The chromosomal arms most frequently demonstrating LOH were 3p (64% of tumours), 5q (45%), 9p (52%), 11p (61%), 13q (50%), 17p (96%), 17q (55%) and 18q (70%). LOH on 3p, 9p, 13q, 17p and 18q occurred mainly within the loci of the VHL, CDKN2, Rb, TP53 and DCC tumour-suppressor genes respectively. LOH on 5q occurred at the sites of the MSH3 mismatch repair gene and the APC tumour-suppressor gene. 11p15.5 and 17q25-qter represented areas of greatest LOH on chromosomes 11p and 17q, and are putative sites of novel tumour-suppressor genes. LOH on 9p was significantly associated with LOH on 5q, and tumours demonstrating LOH at both the CDKN2 (9p21) and MSH3 (5q11-q12) genes had a significantly higher fractional allele loss than those retaining heterozygosity at these sites. Six of nine carcinomas displaying microsatellite alterations also demonstrated LOH at CDKN2, which may be associated with widespread genomic instability. Overall, there are nine sites of LOH associated with oesophageal adenocarcinoma.     

Human bladder cancers and normal bladder mucosa present the same hot spot of heterozygous chromosome-9 deletion

Loss of heterozygosity (LOH) on chromosome 9 is the most frequent genetic alteration in bladder cancer identified to date, suggesting the presence of key gene(s) for this pathology. In this study, we examined 44 bladder tumors and 21 normal bladder samples for LOH on both arms of chromosome 9. Sixteen microsatellite markers, 12 on the short arm (encompassing 9p21-22) and 4 on the long arm (encompassing 9q33-34), were chosen for their highly frequent alterations in bladder cancer. LOH for at least one marker was identified in 42 tumor samples (95.5%), and 14 tumors (32%) displayed LOH for all informative tested markers. Detailed analysis showed that 2 markers on chromosome 9p (D9S157 and D9S156) had the highest frequencies of allelic loss (about 70%), independent of tumor grade and stage. The same study was performed on the 21 normal bladder mucosa samples: 50% of informative cases presented a single specific LOH at the D9S156 locus. Normal samples showing LOH at this locus were therefore screened with 3 novel microsatellite markers in the 810-kb region incorporating D9S156. Using this marker, we found no further heterozygous loss in this region. This result allows different interpretations of the D9S156 loss in normal bladder mucosa, and suggests that D9S156 may be more an indicator of bladder epithelium impairment than a tumor-initiation marker. Similarly, this unexpected result calls in question the interpretation of LOH studies.     

Loss of heterozygosity on the long arm of human chromosome 7 in sporadic renal cell carcinomas

Cytogenetic and molecular analysis of DNA sequences with highly polymorphic microsatellite markers have implicated allele loss in several chromosomal regions including 3p, 6p, 6q, 8p, 9p, 9q, 11p and 14q in the pathogenesis of sporadic renal cell carcinomas (RCCs). Deletions involving the long arm of chromosome 7 have not been described in RCCs although they have been seen in several other tumor types. However, there have been no detailed analysis of loss of heterozygosity (LOH) of 7q sequences in sporadic RCCs. We therefore studied LOH for DNA sequences on 7q with 10 highly polymorphic markers in 92 matched normal/tumor samples representing sporadic RCCs including papillary, nonpapillary, and oncocytomas in order to determine whether allelic loss could be detected in a tumor type with no visible 7q rearrangements at the cytogenetic level. We found chromosome 7q allele loss in 59 of 92 cases (64%) involving one, two, or more microsatellite markers. The most common allele loss included loci D7S522 (24%) and D7S649 (30%) at 7q31.1-31.2, a region that contains one of the common fragile sites, FRA7G. By comparative multiplex PCR analysis, we detected a homozygous deletion of one marker in the 7q 31.1-31.2 region in one tumor, RC21. These results support the idea that a tumor suppressor gene in 7q31 is involved in the pathogenesis of sporadic renal cell carcinomas.     

Evidence for loss of heterozygosity in human psoriatic lesions

Psoriasis, a disease of human skin, is characterized by abnormal differentiation and hyperproliferation of keratinocytes; it has a genetic background. Using 11 highly polymorphic microsatellite markers on eight chromosome arms, we performed an allelotype analysis in 14 psoriatic plaques, in order to reveal any chromosome deletions involved in the development of the disease. We detected loss of heterozygosity (LOH) on at least one microsatellite marker in nine of 14 (64%) cases. We also observed particular genetic loci altered with LOH, on chromosomes 3p, 7p/q and 8p. Our results suggest that LOH is an important phenomenon in the development of psoriatic plaques, providing evidence for deletion of regulatory genes.     

Location of several putative genes possibly involved in human breast cancer progression

Cancer is a genetic disease resulting from an accumulation of genetic abnormalities in various regulatory genes. Most studies on genetic alterations in human breast cancer have involved primary tumors. The possible involvement of specific tumor suppressor genes in the later stages of cancer progression is poorly documented. We investigated allelic losses associated with breast cancer progression by analyzing 55 polymorphic markers on 11 autosomal chromosomes in a series of 49 relapses (23 local recurrences and 26 distant metastases). All of the loss of heterozygosity (LOH) regions reported in primary breast tumors were frequent in both series of relapses. These results suggest that the allelic losses that are common to the different series of samples occur very early during tumor progression. This study points to candidate metastasis-related genes targeted by LOH on chromosome arms 3p21.3, 16q22.2-23.2, and, possibly, 7q31 but provides no clear evidence of LOH affecting previously described metastasis-related genes such as NME1, MTS1, and TSG101.     

Clonal and chronological genetic analysis of multifocal cancers of the bladder and upper urinary tract

Recent molecular genetic studies have suggested that multifocal urothelial cancers are derived from an identical progenitor cell. However, the clonal origin of multifocal urothelial cancers of a low-grade superficial type has not been fully defined. Using microsatellite markers, we examined genetic alterations at 20 loci on eight chromosomal arms (2q, 4p, 4q, 8p, 9p, 9q, 11p, and 17p) in 87 metachronous and/or synchronous multifocal urothelial cancers, which included 84 low-grade superficial papillary tumors from 29 patients. Judging from the patterns of loss of heterozygosity, microsatellite shifts, and the subchromosomal partial deletion, multifocal tumors in at least 20 (80%) of the 25 evaluable patients were considered to be derived from a single progenitor cell, although the possibility remained that multifocal tumors in a small subset of patients might develop from distinct progenitor cells due to field cancerization. In 13 of the 20 patients, a chronological genetic analysis was available: genetic heterogeneity was detected in 3 (23%) patients, and an apparent accumulated pattern of genetic alterations was detected in only 1 (8%) patient. In the 20 patients with multifocal tumors of an identical clonal origin, discordant microsatellite alterations were observed, with significantly lower frequencies on chromosome 9 compared to those on the other chromosomes tested. The results indicate that most multifocal low-grade superficial urothelial cancers are genetically stable despite their incidence of frequent recurrence, and genetic divergence occurs in a subset of patients. This heterotopic spread and genetic divergence may occur long before the clinical manifestation of multiplicity from a single transformed cell. These data support the previous view that heterotopic spread of transformed progenitor cells and genetic divergence occur after chromosome 9 alterations in most of low-grade superficial urothelial cancers.     

Poly(ADP-ribose) polymerase and aging

The activation of oncogenes and the inactivation of tumour suppressor genes play a critical role in laryngeal tumorigenesis. Recent investigations revealed that 8p, 9p and 17q arms of human chromosomes harbour tumour suppressor genes (TSGs) such as p16 and BRCA1 with an important role in the multistage carcinogenesis of the larynx. In order to investigate the implication of these novel TSGs in the development of laryngeal neoplasia we performed a loss of heterozygosity (LOH) analysis using a bank of 15 polymorphic microsatellite markers (4 at 8p21, 7 at 9p21 arm and 4 at 17q arm surrounding the BRCA1 region) in a series of 32 cytological specimens (19 squamous cell carcinoma, 13 benign lesions of the larynx). Both benign and malignant specimens exhibited genetic alterations with at least one microsatellite marker. Fifteen (47%) out of the 32 specimens exhibited LOH at 8p21, 25/32 (78%) showed LOH at 9p21 and 18/32 (56%) displayed LOH at 17q21. Genetic alterations were detected in both benign and malignant lesions for all the loci tested suggesting an important role of these regions in the development of laryngeal neoplasia. This is the first report of detection of microsatellite alterations not only in solid tumours of the larynx but in laryngeal cytological specimens, suggesting that microsatellite analysis may be a useful tool in the primary diagnosis of the disease.     

Detection of loss of heterozygosityat microsatellite loci in esophageal squamous-cell carcinoma

Microsatellite alterations at 3 genetic loci (chromosomes 2p, 3p and 17p) were analyzed in 25 tumors (20 primary tumors and 5 metastatic lymph nodes) from 20 patients after surgical treatment for esophageal cancer. DNA samples from tumors were compared with control DNA from lymphocytes obtained from the peripheral blood of the individual patients. Microsatellite alterations [microsatellite instability (MSI) and loss of heterozygosity (LOH)] were detected in 15% of 20 primary tumors with marker D2S123 (chromosome 2p), 55% with marker D3S1067 (chromosome 3p) and 50% with marker TP53 (chromosome 17p). The 3-year disease-free survival rate of the 10 patients who had tumors without alterations or with an alteration at only 1 of 3 microsatellite loci was 75% and it was better than that of the 10 patients who had tumors with alterations at 2 or 3 microsatellite loci (48%, p = 0.049). This finding suggests that esophageal cancer with alterations at multiple microsatellite loci might have strong malignant potential. However, MSI was only detected in one of 20 patients, which suggests that MSI might not play an important role in the development of this cancer. Three of 5 metastatic lymph nodes showed no LOH even though primary tumors of these patients exhibited LOH with 1 or 2 markers, and 1 metastatic lymph node had LOH that was detected with D3S1067 even though the primary tumor of this patient had no LOH with all markers. Thus, clonal heterogeneity might exist in esophageal squamous-cell carcinomas.     

Leukocyte migration in acute colonic inflammatory bowel disease: comparison of histological assessment and Tc-99m-HMPAO labeled leukocyte scan

Loss of heterozygosity (LOH) on chromosome 11 is frequently altered in various epithelial cancers. The present study was designed to investigate LOH on chromosome 11 in microdissected samples of normal prostatic epithelium and invasive carcinoma from the same patients. For this purpose, DNA was extracted from the microdissected normal and tumor cells of 38 prostate cancers, amplified by polymerase chain reaction PCR and analyzed for LOH on chromosome 11 using 9 different polymorphic DNA markers (D11S1307, D11S989, D11S1313, D11S898, D11S940, D11S1818, D11S924, D11S1336 and D11S912). LOH on chromosome 11 was identified in 30 of 38 cases (78%) with at least one marker. Four distinct regions of loss detected were: 1) at 11p15, at loci between D11S1307 and D11S989; 2) at 11p12, on locus D11S131 (11p12); 3) at 11q22, on loci D11S898, D11S940 and D11S1818; and 4) at 11q23-24, on loci between D11S1336 and D11S912. We found 25% of the tumors with LOH at 11p15; 39% had LOH at 11p12; 66% had LOH at 11q22; and 47% had LOH at 11q23-24. These deletions at 11p15, 11p12, 11q22 and 11q23-24 loci were not related to the stage or grade of the tumor.     

A case of double primary adenocarcinoma of the lung with multiple atypical adenomatous hyperplasia

A case of double primary adenocarcinoma of the lung with multiple atypical adenomatous hyperplasia (AAH) in a 77-year-old woman is reported. Histopathologically, in the resected left upper lobe of the lung, both cancers were diagnosed as well-differentiated papillary adenocarcinoma, and 161 lesions of AAH were also found. Both the cancer lesions and six AAH (greater than 3 mm in diameter) were examined with regard to immunoreactivity of carcinoembryonic antigen (CEA) and p53 gene product, microsatellite instability (MI) and loss of heterozygosity (LOH) on chromosome 9q and 17q by polymerase chain reaction (PCR). Although both cancers expressed CEA, they did not show clonal immunoreactivity for the p53 gene product. Atypical adenomatous hyperplasia expressed CEA weakly and showed no immunoreactivity for p53 gene protein. Both carcinomas showed LOH on chromosome 17q, and one of them showed LOH on chromosome 9q. In six AAH, LOH on chromosome 17q was detected in two tumors, and one of them also showed LOH on chromosome 9q. One AAH, which was negative for LOH on chromosome 17q and 9q, showed MI at D17S791. These results indicated that AAH is a clonal neoplastic lesion with genetic abnormalities and should be called intraepithelial pneumocyte neoplasia, and that each of the numerous papillary lesions in this case was considered to be an independent lesion.     

Allelotype and replication error phenotype of small cell lung carcinoma

Allelotype and replication error (RER) phenotype analyses were performed to clarify the pathogenetic significance of inactivation of tumor suppressor genes and genomic instability in the genesis and progression of small cell lung carcinoma (SCLC). We examined 37 cases of SCLC for loss of heterozygosity (LOH) and microsatellite instability at 49 loci on all 39 nonacrocentric chromosomal arms. LOH was frequently (>70%) detected on chromosomes 3p (29/32, 90.6%), 5q (15/21, 71.4%), 13q (25/26, 96.2%), 17p (22/25, 88.0%), and 22q (24/33, 72.7%). Frequent LOH (>70%) on these loci was observed even among seven cases of stage I tumors. The incidence of LOH on all 39 nonacrocentric chromosomal arms was not significantly different between primary tumors and metastases. These results suggest that inactivation of multiple tumor suppressor genes accumulates relatively early during progression of SCLC and it may be responsible for clinically and biologically aggressive phenotype of SCLC. RER was observed in 6/37 (16.2%) of SCLC, however, RER at multiple loci was observed only in two cases. Therefore, it was indicated that genomic instability is uncommon, but might play a role in the genesis of a small subset of SCLC.     

Identification of a consistent region of allelic loss on 1p32 in meningiomas: correlation with increased morbidity

Meningioma is a common tumor of the central nervous system. Deletions of the short arm of chromosome 1 (1p) are the second most commonly observed chromosomal abnormality in these tumors. Here, we analyzed tumor and normal DNAs from 157 meningioma patients using PCR-based polymorphic loci. Loss of heterozygosity (LOH) for at least one informative marker on 1p was observed in 54 cases (34%), whereas LOH on 1q occurred in only 9 cases (8%). High-resolution deletion mapping defined a consensus region of deletion flanked distally by D1S2713 and proximally by D1S2134, which spans 1.5 cM within 1p32. LOH in this region has also been observed in several other malignancies, suggesting the presence of a tumor suppressor gene or genes that are important for several types of cancer. Statistical analysis revealed that 1p LOH was associated with chromosome 22 deletions and with abnormalities of the NF2 gene in meningioma. In addition, unlike other clinical and molecular characteristics, only 1p LOH was shown to be significantly associated with recurrence-free survival.     

Localization of chromosome 8p regions involved in early tumorigenesis of oral and laryngeal squamous carcinoma

We analysed 30 primary invasive oral and laryngeal squamous carcinomas (SC), with concurrent dysplastic lesions, for genetic alterations at 15 microsatellite loci on the short arm of chromosome 8. Overall, loss of heterozygosity (LOH) was observed, in at least one informative locus, in 27% of the dysplastic lesions and in 67% of the invasive carcinomas. The highest frequency of allele losses in dysplasia (20% and 17%), and invasive carcinoma (40% and 48%) were detected in the same D8S298 and LPL-tet loci located on chromosomes 8p21 and 8p22 respectively. The minimal region with LOH was limited to 4.6 megaBases (mBs) at 8p22 and 7.1 mBs at 8p21. In addition, allelic losses in both dysplastic and corresponding invasive specimens were noted at the same loci in some tumors suggesting their emergence from a common preneoplastic clone. Allele losses correlated significantly with male gender, oral and laryngeal sites and high proliferative index. The data suggest that inactivation of tumor suppressor gene(s), within these loci, may constitute an early event in the evolution of oral and laryngeal SC.     

Waist to hip ratio and psychosocial factors in adults with insulin-dependent diabetes mellitus: the Pittsburgh Epidemiology of Diabetes Complications study

Loss of heterozygosity (LOH) at several chromosomal loci is a common feature of the malignant progression of human tumors. In the case of chromosome 11, LOH has been well documented in several types of solid neoplasms, including gastric carcinoma, suggesting the presence of suppressor gene(s) at 11p15 and 11q22-23. Little is currently known about the molecular events occurring during the development of gastric cancer. To define the regions of chromosome 11 involved in gastric cancer progression, we used high-density polymorphic markers to screen for LOH in matched normal and tumor tissue DNA from 60 primary gastric carcinomas. We found that 21% of the tumors showed LOH simultaneously at 11p15 and 11q22-23, 41% had LOH at 11p15, and 30% had LOH at 11q22-23. We confirm that the minimal critical area of LOH for 11p15.5 is the approximately 2-Mb region between loci D11S1318 and D11S988. However, when we analyzed the pattern of LOH according to the country of origin of the patient, LOH for 11q22-23 alone was found only in cases from Italy. The minimal critical region of LOH at 11q22-23 is identical to that identified for other solid tumors, suggesting that the same putative tumor suppressor gene(s) contained within this region is involved in the pathogenesis of several common human tumors.     

Monitoring of proteinuria in phase I studies in healthy male subjects

An extended analysis for loss of heterozygosity (LOH) on eight chromosomes was conducted in a series of 82 Wilms tumors. Observed rates of allele loss were: 9.5% (1p), 5% (4q), 6% (6p), 3% (7p), 9.8% (11q), 28% (11p15), 13.4% (16q), 8.8% (18p), and 13.8% (22q). Known regions of frequent allele loss on chromosome arms 1p, 11p15, and 16q were analyzed with a series of markers, but their size could not be narrowed down to smaller intervals, making any positional cloning effort difficult. In contrast to most previous studies, several tumors exhibited allele loss for multiple chromosomes, suggesting an important role for genome instability in a subset of tumors. Comparison with clinical data revealed a possible prognostic significance, especially for LOH on chromosome arms 11q and 22q with high frequencies of anaplastic tumors, tumor recurrence, and fatal outcome. Similarly, LOH 16q was associated with anaplastic and recurrent tumors. These markers may be helpful in the future for selecting high-risk tumors for modified therapeutic regimens.     

Molecular support for field cancerization in the head and neck

BACKGROUND: Two competing concepts, field cancerization and micrometastatic lesions, have been postulated to account for the high frequency of second primary tumors and multicentric dysplasia in patients with head and neck carcinoma. METHODS: To provide insight into this process, the authors examined histologically normal mucosa and dysplastic tissue adjacent to invasive tumor for loss of heterozygosity (LOH) at three commonly deleted loci. Tissues from 21 patients with carcinoma of the oral cavity and oropharynx were identified and verified by a pathologist to contain histologically normal mucosa, dysplasia, and adjacent invasive squamous cell carcinoma. Each specimen was analyzed for LOH at D9S171 (9p21), D3S1007 (3p21.3-22), and D3S1228 (3p14). RESULTS: Of the 21 patients, 19 had adequate DNA for analysis. Seventeen patients were heterozygous at one or both of the 3p sites and LOH occurred in 6 of 17 invasive tumor specimens, 1 of 17 dysplasia specimens, and in none of the mucosal specimens. LOH at 9p21 occurred in 11 of 13 informative specimens of invasive tumor, 8 of 13 dysplasia specimens, and 6 of 13 normal mucosa specimens. However, one case that did not have 9p deletion in the tumor demonstrated LOH in the mucosa and two cases had LOH in both the tumor and mucosa but with deletion of the opposite allele. CONCLUSIONS: These data suggest that 9p21 but not 3p14 or 3p21 deletions occur in the absence of histologic changes. In two cases preinvasive and invasive lesions that apparently were an example of histologic progression contained disparate genetic events, calling into question the use of adjacent dysplasia as a model for premalignant lesions.     

Cysteine proteases of Trichomonas vaginalis degrade secretory leukocyte protease inhibitor

Loss of heterozygosity (LOH) of chromosomal arm 8p has been reported to occur at high frequency for a number of common forms of human cancer, including breast cancer. The objectives of this study were to define the regions on this chromosomal arm that are likely to contain breast cancer tumor suppressor genes and to determine when loss of chromosomal arm 8p occurs during breast cancer progression. For mapping the tumor suppressor gene loci, we evaluated 60 cases of infiltrating ductal cancer for allelic loss using 14 microsatellite markers mapped to this chromosomal arm and found LOH of 8p in 36 (60%) of the tumors. Whereas most of these tumors had allelic loss at all informative markers, five tumors had partial loss of 8p affecting two nonoverlapping regions. LOH for all but one of the tumors with 8p loss involved the region between markers D8S560 and D8S518 at 8p21.3-p23.3, suggesting that this is the locus of a breast cancer tumor suppressor gene. We then studied LOH of 8p in 38 cases of ductal carcinoma in situ (DCIS) with multiple individually microdissected tumor foci evaluated for each case. LOH of 8p was found in 14 of the DCIS cases (36%), including 6 of 16 cases of low histological grade and 8 of 22 cases of intermediate or high histological grade. In four of these DCIS cases, 8p LOH was seen in some but not all of the multiple tumor foci examined. These data suggest that during the evolution of these tumors, LOH of 8p occurred after loss of other chromosomal arms that were lost in all tumor foci. Thus, LOH of 8p, particularly 8p21.3-p23, is a common genetic alteration in infiltrating and in situ breast cancer. Although 8p LOH is common even in low histological grade DCIS, this allelic loss often appears to be preceded by loss of other alleles in the evolution of breast cancer.