Frequent loss of heterozygosity on chromosomes Xp and 13q in human ovarian cancer.

Loss of heterozygosity (LOH) was examined at 27 loci on chromosomes 3p, 6q, 11p, 13q, 17 and X in 42 human ovarian tumors. LOH was detected in 12 of 26 (46%) and 5 of 12 (42%) informative cases at 2 chromosome 13q loci, D13S32 and D13S34 respectively. On chromosome Xp, tumor-specific allele loss was observed in 9 out of 15 informative cases (60%) at the ornithine transcarbamylase (OTC) gene locus. Examination of 12 additional Xp and 13q loci has mapped the common deletion regions to Xp21.1-->p11.4 and 13q33-->q34. The observation of significant LOH on Xp represents a strong indication of genetic changes in the X chromosome in a human malignancy. The allele losses on 13q which have been reported for other cancers suggest that chromosome 13, in addition to the retinoblastoma gene, may contain other growth-regulating gene(s) important in the development of several tumor types, including ovarian malignancies.     

Limiting the location of putative human prostate cancer tumor suppressor genes on chromosome 18q

We studied loss of heterozygosity (LOH) on the long arm of human chromosome 18 in prostate cancer to determine the location of a putative tumor suppressor gene (TSG) and to correlate these losses with the pathological grade and stage of the cancer. Of 48 specimens analysed 17 (35.4%) lost at least one allele on chromosome 18q. All the specimens with allelic losses lost at least one allele within chromosomal region 18q21. Allelic losses picked at D18S51 (19%) and D18S858 (17%). A 0.58 cM DNA segment that includes the D18S858 locus and is flanked by the microsatellite loci D18S41 and D18S381, was lost in eight (47%) of 17 specimens with allelic losses. This segment was designated as a LOH cluster region 1 (LCR 1). Although Smad2 resides within LCR 1, it was not mutated in any of the six prostate cell lines (five prostate cancer cell lines and one immortalized prostate epithelial cell line) analysed, suggesting that it is not a candidate TSG in prostate cancer. A second LCR at 18q21, LCR 2, includes the D18S51 locus and is flanked by the D18S1109 and D18S68 loci, which are separated by 7.64 cM. LCR 2 was lost in six (35%) of the 17 specimens with chromosome 18q losses. These results suggest that chromosome 18q21 may harbor two candidate prostate cancer TSGs. The candidate TSGs DCC and Smad4 are located centromeric to the LCRs. No alleles were lost within or in close proximity to these genes, suggesting that they are not targets for inactivation by allelic losses in prostate cancer. Although there was no obvious correlation between chromosome 18q LOH and the pathological grade or stage, three (37.5%) of eight low-grade cancers and nine (32.1%) of 28 organ-confined cancers lost alleles at 18q21, suggesting that allelic losses are relatively early events in the development of invasive prostate cancer.     

A statistical analysis of chromosome 11 and 17 loss of heterozygosity in epithelial ovarian cancer

Many regions of the genome exhibit loss of heterozygosity (LOH) in epithelial ovarian cancer (EOC) suggesting sites of recessive genetic elements such as tumor suppressor genes. We performed detailed LOH studies of chromosomes 17 and 11 using 24 microsatellite repeat markers in a population of 47 patients with EOC. Univariate statistical analysis revealed that significant co-losses of chromosomal loci occurred between 17p and 17q whole arms (p=0.0003), NME1 (17q21) with D11S922 (11p15.5) (p=0.0067) and D11S912 (11q24) with D11S935 (11p13) (p=0.0073). Statistical analysis of the relationship between LOH on particular chromosomal arms and clinicopathological factors revealed a significant association between serous histological subtype of ovarian adenocarcinoma and chromosome 17p (p=0.0052) and telomeric 17q (p=0.0007) LOH. An analysis of specific polymorphic chromosomal loci demonstrated that adverse survival was significantly associated with LOH at 11q24 (p=0.0067) and 17q21 (p=0.0076). There were nonsignificant trends suggesting a relationship between chromosome 17p LOH and poorly differentiated (p=0.025) and advanced FIGO stage (p=0.031) tumours. Considering these statistical associations, a preliminary multistep model for involvement of chromosomes 11 and 17 in ovarian neoplasia can be constructed.     

Allelotype of human ovarian cancer.

In order to determine which chromosome(s) carries a tumor suppressor gene(s) for human ovarian cancer, we examined loss of heterozygosity in 37 tumors with a set of polymorphic DNA markers which cover each autosomal chromosome arm partially. Frequent losses were observed in chromosomes 4p (42%), 6p (50%), 7p (43%), 8q (31%), 12p (38%), 12q (33%), 16p (33%), 16q (38%), 17p (46%), 17q (39%), and 19p (34%). In addition to these chromosomes, frequent losses of alleles on chromosomes 6q, 13q, and 19q were observed uniquely in serous and serous papillary cystadenocarcinomas; loss of heterozygosity was detected only rarely on these chromosomal arms in nonserous types of tumors. The average (0.12) of fractional allelic loss seen in mucinous cystadenocarcinoma, which usually has a better prognosis than other types, was much lower than that of other tumor phenotypes including serous cystadenocarcinoma (0.31) and clear cell carcinoma (0.20). These results suggested that (a) a large number of tumor suppressor genes might play a role in ovarian cancer, (b) losses of alleles in different chromosomal regions could account for differences in histopathological features and/or prognoses among patients, and (c) this kind of analysis can contribute to an improved understanding of tumor development and/or progression in human ovarian cancer.     

Comparative analysis of loss of heterozygosity of specific chromosome 3, 13, 17, and X loci and TP53 mutations in human epithelial ovarian cancer

We previously reported the identification of three minimal regions of deletion on the short arm of chromosome 3 (3p) in epithelial ovarian tumor specimens, suggesting that the inactivation of tumor-suppressor genes in these regions may be important in terms of ovarian tumorigenesis. Another previous study of ovarian cancer observed that allele loss of chromosome 179 was frequently found in ovarian tumors that also showed loss of heterozygosity (LOH) of chromosomes 3p, 13q, 17p, and Xp. In an independent study, we also reported a high frequency of LOH for selected chromosome 17 loci in high-grade and late-stage ovarian tumors. We have extended our LOH analysis of chromosome 3p to include 102 ovarian tumor specimens (29 and 73 samples were previously examined for LOH of chromosome 3p and 17 markers, respectively), using additional polymorphic markers, to assess the coordinate LOH of loci representing the three chromosome 3p minimal regions of deletions [von Hippel-Lindau syndrome (VHL), thyroid hormone receptor beta, and fragile histidine triad (FHIT)] and LOH of other important loci [tumor protein 53 (TP53), breast cancer 1 early onset (BRCA1), breast cancer 2 early onset, retinoblastoma 1, ornithine carbamoyltransferase, and androgen receptor] or somatic mutations in TP53. There was a significant association between LOH of any chromosome 3p marker and LOH of any chromosome 17 marker (P = 0.026). The frequency of LOH at the TP53 locus was higher in the group of samples that displayed LOH of a 3p marker (P = 0.019), as was the frequency of LOH at the BRCA1 locus (P = 0.014). LOH of chromosome 3p was noted in four specimens that did not display LOH of either the BRCA1 or the TP53 locus, indicating that LOH of these loci need not precede LOH of the chromosome 3p loci. We found a significant association between LOH of the VHL (3p25) locus and LOH of any chromosome 17 marker (P = 0.005), suggesting that there may be an important relationship, in the tumorigenesis of epithelial ovarian cancer, between a gene at 3p25 and a gene located on chromosome 17. Our results indicate that inactivation of p53 by somatic mutation is unlikely to be a prerequisite to chromosome 3p LOH, because we found no significant association between mutations in TP53 and LOH of the three chromosome 3p loci. The frequency of LOH at the FHIT locus at 3p14 increased significantly with advancing age at diagnosis (P = 0.018), as did the frequency of somatic TP53 mutations (P = 0.008).     

Loss of heterozygosity on chromosome arms 3p and 6q in microdissected adenocarcinomas of the uterine cervix and adenocarcinoma in situ

BACKGROUND: Despite the increasing frequency of adenocarcinomas of the uterine cervix, little is known regarding inactivation of tumor suppressor genes (TSGs) in this tumor type. The authors analyzed loss of heterozygosity (LOH) in 36 carcinomas of the cervix with glandular differentiation, and 5 adenocarcinoma in situ in 40 patients. METHODS: The authors analyzed samples using laser capture microdissection from archival material and DNA amplified with microsatellite markers on the following loci: 3p14.2 (D3S1234, D3S1300), 3p21.3 (D3S1029, D3S1447), 3p22-24 (D3S1537, D3S1351), 6q21-23.3 (D6S250), 6q25.1 (ESR), 6q25.2 (D6S255), 8p21 (D8S136, D8S1820), 13q12.3 (D13S220, D13S267), 17q21 (D17S579, D17S855). Eight additional markers spanning the short arm of chromosome 3 (3p12-p25) and six spanning the long arm of chromosome 6 (6q11-q27) were studied in the cases showing LOH to further define the deletion intervals. RESULTS: The frequency of allelic loss in cancers was chromosome 3p: 49% (p14.2: 35%, p21.3: 23%, p22-24: 41%), 6q: 48% (q21-23.1: 39%, q25.1: 45%, q25.2: 7%), 13q: 22%, 17q: 6%, and 8p: 18%. On chromosome arm 3p, the authors' data suggest at least two discrete areas of deletion: a proximal area between markers D3S1234 (p12) and D3S1766 (p14.2-14.3), and a second distal interval, telomeric from marker D3S4623 (p21.3). On chromosome 6q, the deletion area is between marker D6S300 (q22) and D6S255 (q25.2). Two of five preneoplastic lesions showed LOH on chromosome arm 3p, and two five showed allelic loss on chromosome arm on 6q, suggesting the genes might be inactivated early in cervical tumorigenesis. CONCLUSIONS: The authors have identified three chromosomal regions that may harbor TSGs involved in the development/progression of adenocarcinomas of the uterine cervix, 3p12-14.2, 3p21.3-pter, and 6q22-25.2. Deletions also were detected in adenocarcinoma in situ, suggesting the genes may be inactivated early in cervical tumorigenesis.     

Loss of heterozygosity for defined regions on chromosomes 3, 11 and 17 in carcinomas of the uterine cervix.

Loss of heterozygosity (LOH) frequently occurs in squamous cell carcinomas of the uterine cervix and indicates the probable sites of tumour-suppressor genes that play a role in the development of this tumour. To define the localization of these tumour-suppressor genes, we studied loss of heterozygosity in 64 invasive cervical carcinomas (stage IB and IIA) using the polymerase chain reaction with 24 primers for polymorphic repeats of known chromosomal localization. Chromosomes 3, 11, 13, 16 and 17, in particular, were studied. LOH was frequently found on chromosome 11, in particular at 11q22 (46%) and 11q23.3 (43%). LOH on chromosome 11p was not frequent. On chromosome 17p13.3, a marker (D17S513) distal to p53 showed 38% LOH, whereas p53 itself showed only 20% LOH. On the short arm of chromosome 3, LOH was frequently found (41%) at 3p21.1. The beta-catenin gene is located in this chromosomal region. Therefore, expression of beta-catenin protein was studied in 39 cases using immunohistochemistry. Staining of beta-catenin at the plasma membrane of tumour cells was present in 38 cases and completely absent in only one case. The tumour-suppressor gene on chromosome 3p21.1 may be beta-catenin in this one case, but (an)other tumour-suppressor gene(s) must also be present in this region. For the other chromosomes studied, 13q (BRCA-2) and 16q (E-cadherin), only sporadic losses (< 15% of cases) were found. Expression of E-cadherin was found in all of 37 cases but in six cases the staining was very weak. No correlation was found between clinical and histological parameters and losses on chromosome 3p, 11q and 17p. In addition to LOH, microsatellite instability was found in one tumour for almost all loci and in eight tumours for one to three loci. In conclusion, we have identified three loci with frequent LOH, which may harbour new tumour-suppressor genes, and found microsatellite instability in 14% of cervical carcinomas.     

An attempt to define sets of cooperating genetic alterations in human breast cancer.

The extent and the variation of losses of genetic material were examined in a series of 191 human breast cancers by means of a set of 18 polymorphic DNA probes, specific of 7 chromosomal arms (1p, 1q, 3p, 11p, 13q, 17p and 18q) known to be frequently affected by allele losses. Frequencies of losses of heterozygosity ranged from a low of 3.5% (chromosome 13q) to a high of 27% (chromosome 3p). The number of sites involved in breast cancer added to the frequent occurrence of concomitant losses at several chromosomal arms within the same tumor suggest cooperative effects of these LOHs. We were therefore interested in assessing the existence of preferential associations between sets of LOHs in our panel of tumors. Statistically significant associations were found between LOHs at chromosomes 1p and 17p, and between LOHs at chromosomes 11p and 17p. Furthermore, since all the tumors presently studied had previously been analyzed for proto-oncogene amplification at 5 distinct chromosomal sites, we tested for associations between LOH and DNA amplification. Such associations were indeed observed as exemplified by the correlations observed between the LOH at 11p and amplification of the erbB2 gene and LOH at 17p and the amplification of the flg gene. The only correlation with clinico-pathological parameters that could be observed linked the occurrence of LOHs on 11p with recurrent breast cancer (p = 0.015). Sets of several LOHs or LOHs and gene amplifications could not be significantly related to any marker of tumor aggressiveness.     

Allelic loss on chromosome 17 in human ovarian cancer

In order to identify a common region of deletion on chromosome 17 potentially containing a tumor-suppressor gene, 27 ovarian carcinomas and 3 ovarian tumors of low malignant potential (LMP) were examined for loss of heterozygosity (LOH) at 6 p arm and 10 q arm loci. Ninety percent of all tumors had deletions at one or more loci. On the p arm, there was a single near-common region of deletion on 17p 13.3 (D/7S30/ pYNZ22.1; 86% LOH), an intervening locus with a low LOH rate, and a more proximal locus on 17p11.2 (D/7S58/pEW301; 82% LOH) with a high LOH rate. In less aggressive tumors, LOH at Df 7S30 was not accompanied by LOH at p53. The q arm had a common region of deletion for high-stage carcinoma at D/7S579 (Mfd 188; 74% LOH) on q21, a locus tightly linked to the familial breast-ovarian-cancer syndrome (BRCAI) locus. D/7S579 was lost in all informative high-stage carcinomas and retained in all low-stage carcinomas and tumors of LMP. There may be at least 2 tumor-suppressor genes, an early-acting gene on the p arm and a gene on the q arm involved in tumor progression and metastasis.     

Limiting the location of a putative human prostate cancer tumor suppressor gene at chromosome 13q14.3

We studied loss of heterozygosity (LOH) on human chromosome 13q in prostate cancer specimens to determine the location of a putative tumor suppressor gene (TSG) and to correlate these losses with the clinicopathological stage of the disease. Overall 13 (21%) of 61 specimens analysed had an allele loss on the long arm of chromosome 13. The most frequent (37%) LOH among the informative cases with allele losses was detected at the D13S284 locus on chromosome 13q14. 3. A portion of the DNA segment that spans this locus and is flanked by the microsatellite loci D13S153 and D13S163 was lost in 85% of the specimens with allele losses and was designated as a LOH cluster region (LCR). The LCR spans more than 6 Mbp of DNA. The results suggest that a TSG relevant for the development of prostate cancer is located telomeric to the RB locus. There was a significant correlation (P=0.0024) between chromosome 13q LOH and advanced metastatic disease, suggesting that loss of 13q14.3 region is associated with prostate cancer progression. However, further research must be conducted to establish the identity and function of this putative TSG.     

Polymerase chain reaction allelotyping of human ovarian cancer.

We have used a set of microsatellite polymorphisms (MSPs) to examine the location and frequency of allele loss throughout the genome in a panel of 25 human epithelial ovarian tumours. When more than one MSP was employed per arm, mean informativity was 85.2% (range 64-100%). The average fractional allelic loss was 0.28 (range 0-0.65). A high frequency of allele loss was seen at 5q (40%), 9q (48%), 11p (43%), 14q (46%), 15q (40%), 17p (61%), 17q (64%), 19p (45%) and Xp (40%), confirming previous findings at some sites, but also suggesting the existence of new tumour-suppressor genes in regions (9q, 14q, 15q) which have not previously been studied in ovarian cancer. For 9q and 14q, partial loss of the arm was more common than loss of heterozygosity for all loci. There was a significant relationship between allele loss affecting the short arm of chromosome 17 and allele loss affecting 17q (P < 0.001). No other relationship was detected between allele losses at different sites. Polymerase chain reaction allelotyping is suitable for the examination of very small tumour samples and tumours in which classical karyotyping is problematic.     

Somatic mutations of the PPP2R1B candidate tumor suppressor gene at chromosome 11q23 are infrequent in ovarian carcinomas

Previous studies have demonstrated frequent allelic losses of distal chromosome 11q in ovarian carcinomas. The tumor suppressor gene(s) presumably targeted by these losses have not yet been identified. PPP2R1B is a candidate tumor suppressor gene at 11q23 that has recently been shown to be mutated in a subset of colorectal and lung cancers. We evaluated 5 ovarian carcinoma cell lines and 27 primary ovarian carcinomas for allelic losses of 11q23 and for mutations in the open reading frame of PPP2R1B. We also evaluated the primary tumors for allelic losses at 17p13, another chromosomal region frequently affected by losses of heterozygosity (LOH) in ovarian cancers. 11q23 and 17p13 allelic losses were identified in 25% and 74% of the carcinomas, respectively. No mutations within PPP2R1B coding sequences were found. These findings indicate that mutations of the PPP2R1B gene are infrequent in ovarian cancer and that deletions affecting the distal portion of chromosome 11q in ovarian cancer likely target inactivation of other genes.     

Loss of heterozygosity at chromosome 9q22-31 is a frequent and early event in ovarian tumors

Loss of heterozygosity (LOH) studies in ovarian tumors, have highlighted the chromosomal regions at 9q22-31 and 9q32-34 as being potentially important in tumor development. We have investigated LOH at 9q22-31 in 85 patients with epithelial ovarian cancer, 15 with non-epithelial tumors and 16 with benign disease. Varying patterns of LOH were observed across the markers used between different tumors, the most common (71%) being interstitial discontinuous losses. LOH was frequent, and was detected at equally high levels in malignant (71%) and benign tumors (70%). LOH occurred in epithelial invasive tumors, borderline tumors, fibromas and dermoid tumors. In malignant epithelial tumors LOH at 9q22-31 was not significantly associated with patient clinical and pathological parameters; however, survival was 29 months at the 50th centile survival, in those women whose tumors displayed LOH compared with 60 months in women whose tumors retained heterozygosity. LOH at 9q22-31 was significantly associated with LOH at the p53 locus (p=0.02) and the ovarian suppressor locus at 3p21 (p=0.05). We conclude that the chromosome region at 9q22-31, flanked by the microsatellite markers D9S1796 and D9S53, is a frequent and early event in ovarian tumorigenesis. With the of extent of discontinuous LOH, high density deletion mapping of this region using LOH as a strategy to identify candidate genes may be problematic. However with the completion of the human genome sequencing project several candidate genes are identified.     

Frequent loss of heterozygosity on chromosomes 1q, 5q, and 17p in human gastric carcinomas

Recently, loss or inactivation of genes at specific chromosomal loci has been considered to be one of the important mechanisms during the development of human tumors. In order to identify tumor suppressor genes for gastric carcinoma, we performed restriction fragment length polymorphism analysis on 48 human gastric carcinomas. Allele losses were investigated for 14 specific loci on chromosomes 1, 5, 6, 7, 10, 11, 12, and 17. Loss of heterozygosity on chromosome 17p13.1 (p53 locus) was detected in 13 (68%) of 19 informative cases. Well-differentiated adenocarcinoma showed high frequencies of allele losses on chromosomes 5q (60%) and 17p (67%) in early cancers and on chromosomes 1q (67%), 5q (36%), 7p (33%), 7q (39%), and 17p (73%) in advanced cancers. In poorly differentiated adenocarcinomas, loss of heterozygosity was detected on chromosomes 1p (38%), 12q (31%), and 17p (60%). Allele losses on chromosomes 1q, 5q, and 7p were not detected in poorly differentiated adenocarcinoma, their frequencies being significantly different between the two histological types. These results suggest that allele loss on chromosome 17p is a common event in gastric carcinoma, regardless of histological type, and that allele loss on chromosome 5q may play a role in the carcinogenesis of well-differentiated adenocarcinoma. Additionally, allele losses on chromosomes 1q and 7p may be involved in the progression of well-differentiated adenocarcinoma.     

Allelotype analysis of common epithelial ovarian cancers with special reference to comparison between clear cell adenocarcinoma with other histological types.

Determination of the histological type of epithelial ovarian cancer is clinically important to predict patient prognosis. To estimate accurately the chromosomal regions that frequently show loss of heterozygosity (LOH) in each histological type, LOH at 55 loci on 38 chromosomal arms was examined by means of laser capture microdissection and PCR-LOH analysis in 45 epithelial ovarian cancers composed of clear cell adenocarcinoma (CCA), serous adenocarcinoma (SEA), endometrioid adenocarcinoma (EMA) and mucinous adenocarcinoma (MUA). In addition, p53 (exons 5 - 8) gene mutations and the nuclear immunoreactivity of p53 proteins in these tumors were examined by PCR-SSCP and immunohistochemistry. In CCA, LOH was detected primarily on 1p (69%) followed by 19p (45%) and 11q (43%). On the other hand, in SEA, LOH was detected in at least 50% of cases on 1p, 4p, 5q, 6p, 8p, 9q, 12q, 13q, 15q, 16p, 17p, 17q, 18p, 18q, 19p, 20p and Xp. The incidences of LOH on 5q, 12q, 13q and 17p were significantly lower in CCA than in SEA (P = 0.019, 0.031, 0.0035 and 0.012). EMA showed a tendency for frequent LOH on 7p, whereas MUA showed significantly high occurrence of LOH at 17p13.1. The incidences of p53 mutation and p53 nuclear immunoreactivity also differed between CCA and SEA: 0% and 7% in the former and 64% and 45% in the latter (P = 0.0006 and 0.039). These findings clarify that there are differences in LOH distribution patterns among different histological subtypes of epithelial ovarian cancer. In CCA, p53 tumor-suppressor gene (TSG) is not involved in carcinogenesis and tumor-suppressor genes located on 1p are considered to play an important role in tumor development.     

Allelotype Analysis of Common Epithelial Ovarian Cancers with Special Reference to Comparison between Clear Cell Adenocarcinoma with Other Histological Types

Determination of the histological type of epithelial ovarian cancer is clinically important to predict patient prognosis. To estimate accurately the chromosomal regions that frequently show loss of heterozygosity (LOH) in each histological type, LOH at 55 loci on 38 chromosomal arms was examined by means of laser capture microdissection and PCR-LOH analysis in 45 epithelial ovarian cancers composed of clear cell adenocarcinoma (CCA), serous adenocarcinoma (SEA), endometrioid adenocarcinoma (EMA) and mucinous adenocarcinoma (MUA). In addition, p53 (exons 5–8) gene mutations and the nuclear immunoreactivity of p53 proteins in these tumors were examined by PCR-SSCP and immunohistochemistry. In CCA, LOH was detected primarily on 1p (69%) followed by 19p (45%) and 11q (43%). On the other hand, in SEA, LOH was detected in at least 50% of cases on 1p, 4p, 5q, 6p, 8p, 9q, 12q, 13q, 15q, 16p, 17p, 17q, 18p, 18q, 19p, 20p and Xp. The incidences of LOH on 5q, 12q, 13q and 17p were significantly lower in CCA than in SEA ( P =0.019, 0.031, 0.0035 and 0.012). EMA showed a tendency for frequent LOH on 7p, whereas MUA showed significantly high occurrence of LOH at 17p13.1. The incidences of p53 mutation and p53 nuclear immunoreactivity also differed between CCA and SEA: 0% and 7% in the former and 64% and 45% in the latter ( P =0.0006 and 0.039). These findings clarify that there are differences in LOH distribution patterns among different histological subtypes of epithelial ovarian cancer. In CCA, p53 tumor-suppressor gene (TSG) is not involved in carcinogenesis and tumor-suppressor genes located on 1p are considered to play an important role in tumor development.     

Molecular genetic investigation of sporadic renal cell carcinoma: analysis of allele loss on chromosomes 3p, 5q, 11p, 17 and 22.

To investigate the role of tumour-suppressor genes on the short arm of chromosome 3 in the mechanism of tumorigenesis in non-familial renal cell carcinoma, we analysed 55 paired blood-tumour DNA samples for allele loss on chromosome 3p and in the region of known or putative tumour-suppressor genes on chromosomes 5, 11, 17 and 22. Sixty-four per cent (35/55) of informative tumours showed loss of heterozygosity (LOH) of at least one locus on the short arm of chromosome 3, compared with only 13% at the p53 tumour-suppressor gene and 6% at 17q21. LOH at chromosome 5q21 and 22q was uncommon (2-3%). Detailed analysis of the regions of LOH on chromosome 3p suggested that, in addition to the VHL gene in chromosome 3p25-p26, mutations in one or more tumour-suppressor genes in chromosome 3p13-p24 may be involved in the pathogenesis of sporadic renal cell carcinoma (RCC). We also confirmed previous suggestions that chromosome 3p allele loss is not a feature of papillary RCC (P < 0.05).     

Frequent loss of heterozygosity on chromosomes 6q, 11, and 17 in human ovarian carcinomas

Recently, tumor-specific allele loss has been shown to be an important characteristic of some tumors. When such loss includes one or more growth-regulatory genes, it may allow the expression of tumorigenicity. Using Southern blots, we analyzed normal and tumor DNA samples from 19 ovarian cancer patients, using a series of polymorphic DNA probes that map to a variety of chromosomal loci. Of 14 informative cases, tumor-specific allelic loss was observed in nine (64%) at the estrogen receptor (ESR) gene locus on chromosome 6q. On chromosome 17p at the D17S28 and D17S30 loci, allelic losses were also detected in 6 of 8 (75%) and 9 of 14 (64%) cases, respectively. Allelic loss at the HRAS1 gene locus on chromosome 11p occurred in 5 of 11 (46%) informative cases. The relatively high incidence of these allelic losses observed on chromosome 6q represents the first implication by molecular genetic analysis of this chromosomal region in a human malignancy, and it thus appears to be a genetic change specific to ovarian carcinoma. DNA sequence losses on 11p and 17p, also reported for other cancers, may reflect the presence of tumor- or growth-suppressor genes on these chromosomes that are important in the genesis of many tumor types, including ovarian malignancies.     

Accumulation of allelic loss on arms of chromosomes 13q, 16q and 17p in the advanced stages of human hepatocellular carcinoma.

We examined loss of heterozygosity at 13 loci on 5 chromosomes in hepatocellular carcinomas (HCCs) from 56 patients. In 42 of these cases, regenerative nodules of liver cirrhosis were also analyzed. High frequencies of allelic losses were detected on chromosomes 13q (47%), 16q (40%) and 17p (64%), whereas losses on chromosome 4p and 11p were observed in less than 22% of cases in HCCs. In contrast, LOH was not detected on any loci in cirrhotic nodules. On chromosome 13q, the common region of allelic loss was mapped to the region including the retinoblastoma (RB) locus, by using 8 polymorphic probes. Furthermore, one case with 13q loss had an interstitial deletion of the RB gene, indicating the involvement of inactivation of the RB gene in hepatotumorigenesis. Losses were associated with portal-vein thrombosis or intrahepatic metastasis, increased tumor size, a poorly differentiated phenotype and clinical stage. Losses occurring together on 13q, 16q and 17p were significantly higher in patients in clinical stage IV or histologically poorly differentiated tumors, suggesting that the accumulation of allelic loss occurs in advanced tumors and that patients with multiple allelic losses may have a worse prognosis than those with a single loss.     

Correlation of loss of alleles on the short arms of chromosomes 11 and 17 with metastasis of primary breast cancer to lymph nodes.

To examine the role of loss of heterozygosity (LOH) during tumor development and/or progression, we looked for correlations between metastasis of breast cancer to a regional lymph node(s) and LOH of chromosomal arms 11p, 13q, 16q, 17p, and 17q, where frequent losses in primary tumors have been detected. No correlation between lymph node metastasis and LOH of chromosomes 13q, 16q, or 17q was observed. However, tumors showing LOH of chromosomes 11p (chi 2 = 10.82, P less than 0.01) and 17p (chi 2 = 6.78, P less than 0.01) revealed a significantly higher incidence of metastasis to a regional lymph node(s) than tumors without LOH on these chromosomal arms. Furthermore, only four of 30 (13%) patients with tumors that retained both 11p and 17p had metastasis to a regional lymph node(s), compared with 24 of 32 (75%) patients with tumors that had lost both 11p and 17p. Analysis of LOH with markers on chromosomes 11p and 17p in a large number of tumors indicated that the peritelomeric region of each of these chromosomal arms contains a tumor suppressor gene that may be associated with tumor progression, particularly metastasis to a regional lymph node(s).