Independent origin of multiple foci of prostatic intraepithelial neoplasia: comparison with matched foci of prostate carcinoma

BACKGROUND: Prostate carcinoma usually is heterogeneous and multifocal, with diverse clinical and morphologic manifestations. Understanding of the molecular basis for this heterogeneity is limited, particularly for the putative precursor, high grade prostatic intraepithelial neoplasia (PIN). In this study, the authors attempted to determine the genetic relation between multiple foci of PIN and matched foci of carcinoma, and whether they are independent in origin. METHODS: The distribution and prevalence of allelic imbalance at 6 microsatellite polymorphic markers on chromosomes 7q, 8p, 8q, and 18q were examined in 84 microscopically excised PIN foci (mean, 1.6 foci/case) and 95 foci of prostate carcinoma (mean, 1.8 foci/case) from 52 completely embedded, mapped whole mount prostates. RESULTS: PIN contained a lower overall proportion of allelic imbalance than matched prostate carcinoma foci for the 6 polymorphic microsatellite markers (65% vs. 82%), but this difference was not significant. The rate of allelic imbalance in PIN was similar to that in prostate carcinoma at 5 of 6 loci studied; the exception, D18S34 (18q12.2-12.3), had a significantly lower rate of allelic imbalance in PIN than in prostate carcinoma (19% vs. 52%), suggesting that genetic alterations in this chromosomal region may be important in carcinogenesis. Of 22 cases with allelic imbalance in at least 1 focus of PIN and 1 focus of prostate carcinoma, 21 informative cases (95%) showed a similar pattern of allelic imbalance at > or = 1 markers in the matched PIN and prostate carcinoma foci. Significant genetic heterogeneity was observed in both PIN and prostate carcinoma. Allelic imbalance was observed in at least 1 focus in 11 of 25 cases with multiple foci of PIN (44%) and 20 of 25 cases with multiple foci of prostate carcinoma (80%). There was no significant correlation between allelic imbalance and pathologic stage or tumor grade. CONCLUSIONS: Our findings indicate that multiple foci of PIN arise independently within the same prostate. This observation suggests that a field effect underlies prostatic neoplasia. Multiple foci of prostate carcinoma also often arise independently, lending additional support for this hypothesis. The strong genetic similarities between PIN and prostate carcinoma strongly suggest that evolution and clonal expansion of PIN may account for the multifocal etiology of carcinomas.     

Allelic imbalance at NME1 in microdissected primary and metastatic human colorectal carcinomas is frequent but not associated with metastasis to lymph nodes or liver

Allelic imbalance at the NME locus on chromosome 17q21 was analyzed in colorectal cancer patients using a highly polymorphic microsatellite repeat sequence within NME1 itself. Duplicate samples of carcinoma and adjacent normal tissue was obtained by microdissection from 6 to 7-microns paraffin sections of 94 primary carcinomas (treatment years 1979-1993) and available lymph node and liver secondaries. In 55 patients informative (heterozygous) at this locus, allelic imbalance was examined in primary and secondary carcinomas. Microsatellite instability prevented assessment of allelic balance in two cases, and there was no evidence of homozygous loss at NME1 in any case analyzed. Allelic imbalance at the NME locus in carcinomas was frequent (27/53; 51%), and concordant results were obtained between primary carcinoma and secondary deposits in 30 of 33 (91%) cases. Three discordant cases showed allelic imbalance in secondary deposits but not the primary lesion. Although frequent, allelic imbalance at NME1 had no relationship to Dukes' stage at presentation or with subsequent hepatic metastasis, nor with the primary carcinoma site (proximal versus distal), tumor size, or mitotic or apoptotic index. Moreover, neither disease-free nor overall survival differed between patients with carcinomas showing NME1 allelic imbalance and patients with carcinomas that did not. Our results show that although allelic imbalance is frequent at the NME locus in primary and secondary colorectal carcinomas, there is no evidence to link this with clinical or pathological features or with metastatic potential. Microsatellite PCR and microdissection of enriched populations of carcinoma cells allowed uniformly successful analysis of samples from archival formalin-fixed paraffin-embedded tissue up to 15 years old and clear assessment of allelic imbalance in tumor specimens. Target sequences (e.g., microsatellites and minisatellites) up to approximately 200-250 bp may be reliably analyzed for allelic balance, suggesting that this method is of general utility in the genetic analysis of primary and metastatic neoplasia.     

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.     

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.     

Allelic imbalance in familial and sporadic prostate cancer at the putative human prostate cancer susceptibility locus, HPC1. CRC/BPG UK Familial Prostate Cancer Study Collaborators. Cancer Research Campaign/British Prostate Group

A recent report has provided strong evidence for a major prostate cancer susceptibility locus (HPC1) on chromosome 1q24-25 (Smith et al, 1996). Most inherited cancer susceptibility genes function as tumour-suppressor genes (TSGs). Allelic loss or imbalance in tumour tissue is often the hallmark of a TSG. Studies of allelic loss have not previously implicated the chromosomal region 1q24-25 in prostate cancer. However, analysis of tumour DNA from cases in prostate cancer families has not been reported. In this study, we have evaluated DNA from tissue obtained from small families [3-5 affected members (n = 17)], sibling pairs (n = 15) and sporadic (n = 40) prostate tumours using the three markers from Smith et al (1996) that defined the maximum multipoint linkage lod score. Although widely spaced (12-50 cM), each marker showed evidence of allelic imbalance in only approximately 7.5% of informative tumours. There was no difference between the familial and sporadic cases. We conclude that the incidence of allelic imbalance at HPC1 is low in both sporadic tumours and small prostate cancer families. In this group of patients, HPC1 is unlikely to be acting as a TSG in the development of prostate cancer.     

Sequential molecular abnormalities are involved in the multistage development of squamous cell lung carcinoma

To understand the molecular pathways involved in the pathogenesis of squamous cell lung carcinoma, we obtained DNA from 94 microdissected foci from 12 archival surgically resected tumors including histologically normal epithelium (n=13), preneoplastic lesions (n=54), carcinoma is situ (CIS) (n=15) and invasive tumors (n=12). We determined loss of heterozygosity (LOH) at 10 chromosomal regions (3p12, 3p14.2, 3p14.1-21.3, 3p21, 3p22-24, 3p25, 5q22, 9p21, 13q14 RB, and 17p13 TP53) frequently deleted in lung cancer, using 31 polymorphic microsatellite markers, including 24 that spanned the entire 3p arm. Our major findings are as follows: (1) Thirty one percent of histologically normal epithelium and 42% of mildly abnormal (hyperplasia/metaplasia) specimens had clones of cells with allelic loss at one or more regions; (2) There was a progressive increase of the overall LOH frequency within clones with increasing severity of histopathological changes; (3) The earliest and most frequent regions of allelic loss occurred at 3p21, 3p22-24, 3p25 and 9p21; (4) The size of the 3p deletions increased with progressive histologic changes; (5) TP53 allelic loss was present in many histologically advanced lesions (dysplasia and CIS); (6) Analyses of 58 normal and non-invasive foci having any molecular abnormality, indicated that 30 probably arose as independent clonal events, while 28 were potentially of the same clonal origin as the corresponding tumor; (7) Nevertheless, when the allelic losses in the 30 clonally independent lesions and their clonally unrelated tumors were compared the same parental allele was lost in 113 of 125 (90%) of comparisons. The mechanism by which this phenomenon (known as allele specific mutations) occurs is unknown; (8) Four patterns of allelic loss in clones were found. Histologically normal or mildly abnormal foci had a negative pattern (no allelic loss) or early pattern of loss while all foci of CIS and invasive tumor had an advanced pattern. However dysplasias demonstrated the entire spectrum of allelic loss patterns, and were the only histologic category having the intermediate pattern. Our findings indicate that multiple, sequentially occurring allele specific molecular changes commence in widely dispersed, apparently clonally independent foci, early in the multistage pathogenesis of squamous cell carcinomas of the lung.     

Four regions of allelic imbalance on 17q12-qter associated with high-grade breast tumors

Rearrangements or loss of chromosome 17 are frequent events in breast tumors. Chromosome 17 contains at least four genes implicated in breast cancer (TP53, ERBB2 (Her2/neu), BRCA1, and NM23), as well as other putative tumor suppressor genes and oncogenes implicated in loss of heterozygosity or allelic imbalance studies. Allelic imbalance represents the addition or loss of genetic material in tumor samples, providing circumstantial evidence for the location of cancer related genes. We have analyzed a panel of 85 breast tumor/normal tissue pairs with 21 PCR-based short tandem repeat (STR) markers located at 17q12-qter to more precisely define regions of allelic imbalance and to determine their relation to clinical parameters. Our analysis revealed at least four common regions of allelic imbalance: proximal to BRCA1, including D17S800 (17q12); distal to NM23 around D17S787 (17q22); near the growth hormone (GH) locus, at D17S948 (17q23-24); and between markers D17S937 and D17S802 (17q25). These data also reveal that loss (or gain) of 17q genetic material correlates with poorly differentiated (grade III) tumors (P = < 0.001), high S phase fraction (P = 0.034), and positive TP53 immunohistochemical staining (P = 0.011). However steroid receptor status, ERBB2 (Her2/neu) staining, and aneuploidy do not correlate with allelic imbalance at 17q.     

Chromosome 7 rearrangements in glioblastomas; loci adjacent to EGFR are independently amplified

The first gene found to be amplified in human glioblastomas was EGFR at 7p12. More recently the MET gene at 7q31 was also reported amplified. We have studied chromosome 7 in a series of 47 glioblastomas by FISH, RFLP and microsatellite analysis. Four per cent (2/47) had 1 centromere, 26% (12/47) 2, 32% (15/47) 3, 4% (2/47) 4, and 34% (16/47) had subpopulations with variable numbers of chromosome 7 centromeres. In 25 of the 47 tumors (53%) the pattern of allelic imbalance observed at each informative locus was similar and in accord with the FISH data, indicating loss or gain of complete chromosome copies. In 32% of tumors (15/47) varying allelic imbalance was seen at different loci along the chromosome indicative of loss or gain of parts of chromosome 7 on a background of disomy, trisomy, tetrasomy, or polysomy. Amplification was studied in an extended series of 121 glioblastomas, and was seen at the 7p12 region in 47 tumors (39%). Forty-two tumors showed amplification of EGFR and 12 of these had extensive amplicons including a number of adjacent loci, always involving only 1 allele. The amplicons of 5 tumors (11%) did not include EGFR, indicating that other unidentified genes in the region are targeted for amplification. Amplification of MET was not found. The findings show that copy number changes of chromosome 7 are common and that a number of genes may be targeted for amplification at 7p12 in glioblastomas.     

Comparative genomic hybridization analysis of lobular carcinoma in situ and atypical lobular hyperplasia and potential roles for gains and losses of genetic material in breast neoplasia

Lobular carcinoma in situ (LCIS) and atypical lobular hyperplasia (ALH) of the breast are cytologically similar breast lesions that reportedly carry different relative risks of subsequent development of invasive carcinoma. They are frequently multifocal and bilateral. We have identified the chromosomal copy number changes in 31 LCIS and 14 ALH lesions from 28 cases and also the 7 invasive carcinomas that subsequently developed in 6 of these cases. This was achieved by comparative genomic hybridization analysis of microdissected formalin-fixed, paraffin-embedded material. There was no significant difference between the aberrations found in the unilateral versus the bilateral cases of LCIS. Loss of material from 16p, 16q, 17p, and 22q and also gain of material from 6q were found at a similar high frequency in LCIS and ALH. Loss of these genomic regions may indicate the locations of genes that predispose to the development of the lesions, and the results are consistent with LCIS and ALH representing the same genetic stage of development. Comparison of the comparative genomic hybridization results from LCIS/ALH with those from ductal carcinoma in situ and invasive cancer showed some similarities at the chromosomal level, but it also showed significant differences, including gain of 1q and 8q and evidence for genomic amplification, which were not found in LCIS/ALH. A genetic model is postulated for the possible relationships between noninvasive lobular lesions and invasive breast carcinoma, delineating potential roles for specific chromosome copy number changes.     

Comment: ''devining'' the role of the consultant psychiatrist in a public mental health service

Radiographically occult bronchogenic squamous cell carcinomas are early lung cancers that localize mainly in the bronchial wall, and are thought to be a good model for investigating genetic alterations through lung cancer progression. In order to elucidate sequential genetic changes in lung cancers, we analysed the incidence of allelic losses on chromosome regions 2q33, 3p21, 5q21, 7q31, 9p21 and 17p13 for 40 cases of radiographically occult bronchogenic squamous-cell carcinomas and 40 cases of advanced lung cancers microdissected. In this study we used eight microsatellite dinucleotide polymorphic markers. Frequent loss of heterozygosity (LOH) was observed on 3p21 (53%), 5q21 (44%) and 17p13 (61%) in roentgenographically occult bronchogenic squamous cell carcinomas. 2q, 7q and 9p were lost less frequently in both roentgenographically occult bronchogenic squamous cell carcinomas and advanced lung cancers. These results suggest that several tumour-suppressor genes are associated with lung cancer progression and that genetic changes on 3p21, 5q21 and 17p13 are early events.     

Multifocal renal cell carcinoma: evidence for a common clonal origin

The reported incidence of satellite tumor lesions in kidneys resected by radical nephrectomy for renal cell carcinoma (RCC) is 7-25%; however, genetic analyses of satellite tumors in comparison with those of main tumor lesions have not been performed well. In the present study, we investigated the incidence of loss of heterozygosity (LOH) at chromosome arms 3p, 6q, 8p, 9p, 9q, and 14q using 18 microsatellite markers in 10 nonpapillary RCCs of 50 mm or less in diameter and the accompanying satellite tumor lesions to evaluate the genetic alterations in main and satellite tumors. LOH was detected in 10, 3, 5, 3, 2, and 3 cases at chromosome arms 3p, 6q, 8p, 9p, 9q, and 14q, respectively. In addition, primary and satellite tumor lesions in 8 of 10 cases exhibited identical patterns of LOH on the 18 loci examined. In the remaining two cases, both main and satellite tumors demonstrated LOH on the common seven and three loci, respectively, whereas for another locus, LOH was observed only in the satellite tumor lesions. The similarity of LOH patterns detected in main and satellite tumor lesions indicates that the presence of satellite tumors might be the result of intrarenal metastasis from the main tumor lesion. These findings strongly suggest that even in case of small nonpapillary RCC, nephron-sparing surgery might carry the risk of failing to prevent postoperative local recurrence due to the incomplete resection of unrecognized satellite tumors with genetic alterations similar to those of the main tumor.     

Allelic loss at chromosomes 3p, 8p, 13q, and 17p associated with poor prognosis in head and neck cancer

BACKGROUND: Little is known about the molecular genetic events that contribute to the pathogenesis of squamous cell carcinoma of the upper aerodigestive tract. Previous molecular genetic studies have been limited to the identification of mutations of the p53 (also known as TP53) tumor suppressor gene, activation of a limited set of oncogenes, allelic loss at 3p and other locations, and occasional association with human papillomavirus infection. PURPOSE: Our purpose was to screen tumor tissue and blood from patients with squamous cell carcinoma of the upper aerodigestive tract for loss of heterozygosity at polymorphic loci corresponding to each of the autosomal chromosomes and to identify the locations of additional putative tumor suppressor genes, other than RB (also known as RB1) and p53, that may contribute to the pathogenesis of this disease. METHODS: Tumor tissue and blood were obtained from 68 consecutive patients with squamous cell carcinoma of the upper aerodigestive tract. In all cases, tumor tissue was obtained from the center of the surgical specimen. The relative absence of non-neoplastic tissue was confirmed by frozen-section histologic examination of immediately adjacent tissue. Initially, 30 paired tissue and blood samples were tested for loss of heterozygosity by polymerase chain reaction (PCR) to amplify 43 different highly polymorphic sequences containing small oligonucleotide repeats. After PCR amplification, with unique oligonucleotides flanking the repeat, visualization and sizing of the alleles on DNA sequencing gels were performed. Specific loss of heterozygosity was distinguished from random genetic loss due to generalized chromosomal instability if it occurred in more than 20% of specimens tested for a particular marker. RESULTS: Significant loss of heterozygosity (> 20%) occurred at alleles at chromosome bands 3p21 (32%), 3p25-26 (56%), 8pter-21.1 (31%), 13q14 (27%), and 17p12 (45%). Loss of heterozygosity at more than two loci was significant with a poor prognosis (P = .039). CONCLUSIONS: These findings demonstrate that squamous cell carcinoma of the upper aerodigestive tract exhibits genetic alterations at multiple loci and that allelic loss at more than two locations is indicative of a poor prognosis (the likelihood of the patient dying of disease). IMPLICATIONS: While tumor suppressor genes at 3p (VHL), 13q (RB), and 17p (p53) have been identified, altered genes at other loci on 3p and on 8p have not yet been characterized. Furthermore, the genotype at these loci for squamous cell carcinoma of the upper aerodigestive tract has prognostic importance and may identify the patients who should receive the most aggressive treatment.     

Frequent allelic losses on chromosome 13q in human male breast carcinomas

Loss of genetic material on chromosomes 13q and 17 has been suggested to be of importance in the initiation and progression of female breast cancer, but their involvement is less well illustrated in male breast carcinomas. The present study was designed to investigate the incidence of allelic loss and microsatellite instability for chromosomes 13q, 17p and 17q in 13 sporadic male breast carcinomas using matched normal-tumour DNA samples and seven polymorphic microsatellite markers. Genetic imbalance was found in one or more informative markers in 85% of the patients, with more frequent loss of heterozygosity and microsatellite instability at loci on chromosome 13q. Thus, a high incidence of allelic losses was observed at the retinoblastoma gene (4/6) and likewise at the D13S263 locus (7/12), which also exhibited the highest frequency of microsatellite instability. The intragenic microsatellite in intron 1 of the TP53 gene on chromosome 17p revealed loss of heterozygosity in 3 of 8 informative patients. The investigated proximal region of chromosome 13q is postulated to harbour several potential tumour suppressor genes associated with female breast cancer. The high incidence of allelic losses at the D13S263 microsatellite, located distal to both the BRCA2 and the Brush-1 loci but proximal to the retinoblastoma gene, possibly indicates the presence of an additional tumour suppressor gene which may be involved in male breast carcinomas. However, this hypothesis needs verification in an extended study of male breast carcinomas.     

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.     

Allelic imbalance and instability of microsatellite loci on chromosome 1p in human non-small-cell lung cancer

The mapping of allelic loss on the short arm of chromosome 1 has been performed in non-small-cell lung cancer. We used a set of 11 microsatellite loci spanning 1p to examine the frequency of allelic imbalance in a panel of 58 tumours. Fifty-one of 58 (87.9%) cases have shown somatic allelic loss at one or more loci tested. The two shortest regions of the overlap (SRO) of the deletions have been identified: SRO 1 at 1p13.1 and SRO 2 at 1p32-pter. Allelic losses at these regions have been compared among adenocarcinoma and squamous cell carcinoma and no difference has been found. In contrast to SRO 1, deletions at SRO 2 significantly correlated with advanced stage of the disease as well as post-operative metastasizing and relapse. These data may suggest that SRO 1 and SRO 2 can harbour tumour-supressor genes (TSGs) involved in different stages of NSCLC development. SRO 2 is still quite large and its refined mapping should help attempts to clone and identify the putative TSG(s). Microsatellite instability (replication errors) affecting only 6 (10.3%) of 58 tumour samples is an infrequent genetic alteration at the loci tested.     

Comparison of p53 immunoexpression with allelic loss of p53 in ulcerative colitis-associated dysplasia and carcinoma

We correlated p53 overexpression with allelic deletion of p53 in ulcerative colitis (UC) with high grade dysplasia (HGD, n=12) and carcinoma (CA, n=8). Sections were immunostained against p53 and epithelium was microdissected on consecutive sections with subsequent amplification for LOH of p53 (17p). Staining with anti-p53 was positive in HGD (9 of 12) and CA (7 of 8). Percent positive cells were less in HGD than in CA. LOH of p53 was present in HGD (5 of 12) and CA (5 of 7). Of cases with <10% of positive cells, including negative cases, 50% also showed LOH. These results suggest that most cases with prominent p53 overexpression but also significant numbers of cases with weak or negative expression have associated allelic p53 deletion. We conclude that i) immunohistochemical stains but not LOH for p53 correlate with progression of dysplasia to carcinoma, ii) p53 immunohistochemistry appears to more accurately predict biologic behavior of dysplasia and carcinoma in UC compared to allelic deletion studies alone. Further microdissection studies are necessary to evaluate the possibility of different carcinoma risk in patients with low percentage of p53 overexpression and associated LOH.     

Genetic changes and histopathological grades in human hepatocellular carcinomas

Loss of heterozygosity (LOH) on chromosomes 1p, 4q, 5q, 8p, 13q, 16q, 17p, and 22q, and mutation of the p53 gene were simultaneously analyzed in 63 hepatocellular carcinomas (HCCs) with distinct histopathological grades, 80% of the tumors being from patients who had been exposed to hepatitis B virus (HBV) or hepatitis C virus (HCV). The frequencies of LOH on 8 chromosomes were 0-25% in 10 well differentiated HCCs, LOH being observed on 4q, 5q and 17p, 21-53% in 26 moderately differentiated HCCs, LOH on 8p and 17p being high, and 29-75% in 27 poorly differentiated HCCs, LOH on 17p, 4q and 8p being the most frequent. p53 gene mutation was detected in moderately and poorly differentiated HCCs at 15% and 52%, respectively, but not at all in well differentiated HCCs. Of the mutations detected, 42% were transition mutation and only 5% were CpG transition, in contrast to the high frequencies of these types of mutations in colon tumors (78% and 54%, respectively). LOH on every chromosome and p53 mutation were more frequent in more advanced tumors, and accumulation of genetic changes increased with increase of the histopathological grade. Frequency of genetic changes in HCCs from HBV-positive patients was comparable to that from HCV-positive patients. The present results suggest that accumulation of genetic changes in multiple tumor suppressor genes, especially LOH on 17p, 4q and 8p, and mutation in p53 gene, are involved in the progression of liver cancer, and LOH on 17p and 4q precedes other genetic changes. Differences in the direction of p53 mutation between HCC and colon carcinoma suggest that liver carcinogens are distinct from colon carcinogens. Furthermore, mechanisms affecting the frequency of LOH in HCCs in HBV-infected patients may be similar to those in HCV-infected patients.     

Genomic alterations in fallopian tube carcinoma: comparison to serous uterine and ovarian carcinomas reveals similarity suggesting likeness in molecular pathogenesis

Serous carcinomas of the fallopian tube, uterus, and ovary resemble each other both histologically and in clinical behavior. Comparative genomic hybridization was performed on 20 primary fallopian tube carcinoma specimens to find regions of the genome involved in tubal carcinogenesis and to compare the genomic alterations with those previously detected in serous ovarian and uterine carcinomas. The most frequent changes detected in fallopian tube carcinoma were gains at 3q (70%) and 8q (75%), with high-level amplifications in several cases. Other common gains occurred at 1q, 5p, 7q, 12p, and 20q. The most frequent losses were found at 18q, 8p, 4q, and 5q. The frequency and the pattern of chromosomal changes detected in tubal carcinoma were strikingly similar to those observed in serous ovarian and uterine carcinomas, suggesting common molecular pathogenesis.     

Cytogenetic studies of epithelial ovarian carcinoma

We performed cytogenetic studies of 36 human epithelial ovarian carcinomas using in situ culture and robotic harvest. We obtained analyzable metaphases of all 36 tumors (100%). One or more chromosomally abnormal clones were observed in 80% of tumors. Common clonal chromosome gains (each occurring in six or more cases) included +1, +2, +3, +6, +7, +9, and +12. Common clonal chromosome losses (occurring in 12 or more cases) included -X, -4, -8, -11, -13, -15, -17, and -22. Common clonal structural abnormalities (occurring in four or more cases) involved regions 1p36, 1q32, 1q42, 3p13-->p26, 3q26-->q29, 7p22, 9q34, 11p13-p15, 17q21-->q23, 19p13.3, and 19q13.3. Trisomy 12 was noted as the sole anomaly in three of five borderline and grade 1 tumors. Two grade 2 tumors contained i(1q), -14, -15 and -22. The results suggest that the pathogenesis of borderline and low-grade tumors may differ from that of higher grade tumors. Two high-grade tumors had an apparent translocation between 17q21 and 19p13.3, two chromosome regions believed to be critical to ovarian carcinogenesis.     

Cytogenetic analysis of pancreatic carcinomas: intratumor heterogeneity and nonrandom pattern of chromosome aberrations

Twenty-nine nonendocrine pancreatic carcinomas (20 primary tumors and nine metastases) were studied by chromosome banding after short-term culture. Acquired clonal aberrations were found in 25 tumors and a detailed analysis of these revealed extensive cytogenetic intratumor heterogeneity. Apart from six carcinomas with one clone only, 19 tumors displayed from two to 58 clones, bringing the total number of clones to 230. Karyotypically related clones, signifying evolutionary variation, were found in 16 tumors, whereas unrelated clones were present in nine, the latter finding probably reflecting a distinct pathogenetic mechanism. The cytogenetic profile of pancreatic carcinoma was characterized by multiple numerical and structural changes. In total, more than 500 abnormal chromosomes, including rings, markers, homogeneously stained regions, and double minutes, altogether displaying 608 breakpoints, were detected. This complexity and heterogeneity notwithstanding, a nonrandom karyotypic pattern can be discerned in pancreatic cancer. Chromosomes 1, 3, 6, 7, 8, 11, 12, 17, and 19 and bands 1q12, 1q21, 3q11, 6p21, 6q21, 7q11, 7q22, 7q32, 11q13, 13cen, 14cen, 17q11, 17q21, and 19q13 were most frequently involved in structural rearrangements. A total of 19 recurrent unbalanced structural changes were identified, 11 of which were not reported previously: del(1)(q11), del(3)(p11), i(3)(q10), del(4)(q25), del(11)(p13), dup(11)(q13q23), i(12)(p10), der(13;15)(q10;q10), del(18)(q12), del(18)(q21), and i(19)(q10). The main karyotypic imbalances were entire-copy losses of chromosomes 18, Y, and 21, gains of chromosomes 7, 2, and 20, partial or whole-arm losses of 1p, 3p, 6q, 8p, 9p, 15q, 17p, 18q, 19p, and 20p, and partial or whole-arm gains of 1q, 3q, 5p, 6p, 7q, 8q, 11q, 12p, 17q, 19q, and 20q. In general, the karyotypic pattern of pancreatic carcinoma fits the multistep carcinogenesis concept. The observed cytogenetic heterogeneity appears to reflect a multitude of interchangeable but oncogenetically equivalent events, and the nonrandomness of the chromosomal alterations underscores the preferential pathways involved in tumor initiation and progression.