Allele loss on short arm of chromosome 17 in breast cancers

Prognostic factors in human primary breast cancer: comparison of c-myc and HER2/neu amplification

Amplification of oncogenes in primary tumours may have prognostic and/or therapeutic significance for patients with breast cancer. We have studied HER2/neu and c-myc amplification together with steroid receptors in human primary breast tumours and related the outcome with (relapse-free) survival. A strong inverse correlation was found between HER2/neu amplification and the presence of oestrogen and progesterone receptors. Actuarial 5-years survival showed that breast cancer patients with c-myc amplification in their primary tumours experience a shorter relapse-free survival, especially in node-negative and in receptor-positive tumours, whereas HER2/neu amplification may be of prognostic value for overall survival in receptor-negative tumours. Overall, in our hands, c-myc amplification appeared to be a more potent prognosticator than HER2/neu amplification in human primary breast cancer.

Hepatitis B virus infection and primary hepatocellular carcinoma

For many years, epidemiological studies have demonstrated a strong link between chronic hepatitis B virus (HBV) infection and the development of primary hepatocellular carcinoma (PHC). Other hepatocarcinogens such as hepatitis C virus and aflatoxin also contribute to hepatocarcinogenesis either in conjunction with HBV infection or alone. Cellular and molecular biological studies are providing explanations for the HBV-PHC relationship, and models are now being formulated to further test the relative importance of various factors such as viral DNA integration, activation of oncogenes, genetic instability, loss of tumor suppressor genes, and trans-activating properties of HBV to the pathogenesis of PHC. Further research will probably define more than a single mechanism whereby chronic HBV infection results in PHC.

Abnormal p53 immunoreactivity and prognosis in node-negative breast carcinomas with long-term follow-up

The expression of the p53 gene product was investigated immunocytochemically in a retrospective series of 164 formalin-fixed paraffin-embedded invasive breast carcinomas with pathologically proven negative lymph nodes. Overall, 78 tumors (48%) showed a variable degree of p53 immunoreactivity. Among these, 38 cases were low expressors (1-10% p53 immunoreactive tumor cells), 21 moderate expressors (10-50% immunoreactive cells) and 19 high expressors (> 50% immunoreactive cells). Abnormal p53 expression correlated significantly with tumor size, histological and nuclear grade, DNA ploidy, mitotic rate and proliferation index, and with the lack of estrogen receptors. Disease-free and adjusted survival analysis of the 124 node-negative patients with long term (more than 10 years) follow-up, however, did not reveal an independent prognostic role for p53 expression. These data suggest that the evaluation of p53 immunoreactivity may only play a role in a multiparametric prognostic assessment of node-negative breast carcinoma.

Rearrangement of chromosome 1p in breast cancer correlates with poor prognostic features

In a cytogenetic study of breast cancer biopsies, clonal abnormalities of chromosome 1p were identified in 56% (14) of 25 informative patients. Translocations predominated, involving 1p22 (n = 1), 1p35 (n = 1) or 1p36 (n = 10) breakpoints. Chromosome 1p abnormalities were associated with estrogen receptor (ER) negativity (P = 0.03, 2-tailed Fisher Exact Probability test), high histological grade (P = 0.02, 2-tailed Mann-Whitney U-test) and an unfavourable Melbourne Prognostic Score (NEPA P = 0.02, SEPA P = 0.04, 2-tailed Mann-Whitney U-tests). These findings are consistent with the possibility that a gene located on chromosome 1p is implicated in tumour progression.

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.

Rat p53 gene mutations in primary Zymbal gland tumors induced by 2-amino-3-methylimidazo[4,5-f]quinoline, a food mutagen

There are reports of p53 gene mutations in various human cancers but not in rat tumor cell lines or rat primary tumor tissue. We found a p53 gene mutation in a cell line of a spontaneous squamous cell carcinoma of the rat Zymbal gland, SCC131, at codon 171 by direct sequencing of cDNA fragments amplified by PCR. We tested for p53 gene mutations in 15 primary Zymbal gland tumors induced by 2-amino-3-methylimidazo[4,5-f]quinoline by single-strand conformation polymorphism analysis of the PCR-amplified cDNA products. Samples of four tumors showed mobility shifts. Direct sequencing revealed that all these tumors had mutations in conserved regions or in scattered conserved residues. Single-strand conformation polymorphism analysis of cDNA suggested that mRNA from the wild-type allele of the p53 gene was not present in tumor cells of three of four positive cases, although genomic DNA analysis indicated that the wild-type allele was retained in all the cases. All mutations were found at a guanine base: three mutations were guanine----pyrimidine transversions and one was a deletion of a guanine base within a G+C-rich sequence. These findings indicate that 2-amino-3-methylimidazo[4,5-f]quinoline may be directly involved in induction of these mutations by forming DNA adducts at various sites in the p53 gene.

P53 and Ki-67 immunoreactivity in human prostate cancer and benign hyperplasia

Mutation of the p53 gene is one of the commonest genetic abnormalities found in solid human tumours. This gene is probably concerned with the control of cellular proliferation and in view of this we carried out a study of human prostate cancer and benign prostatic hyperplasia, comparing the expression of mutated p53 with measurement of growth fractions as assessed by staining with Ki-67. A series of 29 patients with prostate cancer (CaP) were compared with 34 men with benign hyperplasia (BPH); 22 of 29 prostate cancers (76%) contained Ki-67 immunoreactivity compared with 10 of 34 (29%) BPH. With respect to p53 staining, significantly more prostate cancers (17%) were stained than BPH (0%). The mean Ki-67 score in cancers positive for p53 (4.3%) was greater than that found in cancers negative for p53 (1.2%), but no statistically significant relationship was found between tumour grade and Ki-67 staining. The use of Ki-67 and p53 staining may allow identification of tumours with a higher rate of cell growth and may permit development of prognostic factors.

Genetic alterations of the tumour suppressor gene regions 3p, 11p, 13q, 17p, and 17q in human breast carcinomas

Fifty-nine primary breast carcinomas and 11 metastases were examined to identify genetic alterations in the tumour suppressor gene regions 3p, 11p, 13q, 17p, and 17q. Loss of heterozygosity (LOH) was frequently observed on chromosome arms 17p (p144D6 lost in 75%, pYNZ22.1 in 55%, and TP53 in 48% of the primary tumours), 13q (RBI lost in 40% of the primary tumours), and 17q (pRMU3 lost in 35%, pTHH59 in 29%, and NM23HI in 26% of the primary tumours). Loss of all the markers except p144D6 was observed even more frequently in the metastases. Pairwise comparisons for concordance of allele losses on 17p indicated that there might be two genes on 17p implicated in breast cancer development; the TP53 gene and a gene located close to the p144D6 and pYNZ22.1 markers. LOH of the RBI gene was associated with LOH of pYNZ22.1 and p144D6, but not with LOH of TP53. LOH of RBI and TP53 was associated with occurrence of ductal carcinomas, RBI and p144D6 losses with tumour size, and p144D6 losses with positive node status as well. LOH of TP53 and the three 17q markers NM23HI, pTHH59, and pRMU3 was most frequently observed in tumours from postmenopausal women. p144D6 losses occurred most frequently in progesterone receptor-negative tumours, whereas pTHH59 losses occurred most frequently in oestrogen receptor-negative tumours. LOH of the investigated loci was not associated with ERBB2 protooncogene amplification, with positive family history of breast cancer, or with survival.

Characterization of four in vitro established canine mammary carcinoma and one atypical benign mixed tumor cell lines

Five spontaneous canine mammary tumors were cultured in vitro and cell lines were established. The tumors included three frozen carcinomas, fine-needle aspirate from one fresh carcinoma, and one fresh atypical benign mixed tumor. The cell lines have so far been cultured for about 2 yr and passaged between 45 and 200 times. The cell lines expressed different types of intermediate filaments, including a heterogenous pattern. In some cases no intermediate filaments were expressed. Ultrastructure studies showed epithelial cells and cells intermediate between epithelial and myoepithelial types. Retrovirus associated A-particles were found in two carcinomas. The mixed mammary tumor cell line formed ductlike structures in collagen substrate. The cell lines grew when inoculated s.c. into male nude mice. Two carcinomas caused lymph node metastases in two mice and another carcinoma single lung metastases in one tested mouse. DNA hypodiploidy, studied by flow cytometry, in one of the primary carcinoma was retained in vitro, and this cell line showed polyploidy during later passages. The other cell lines had a more unstable DNA profile, although a tendency for polyploidy was found. These findings were also illustrated in chromosome studies.

Absence of p53 germ-line mutations in bilateral breast cancer patients

The cause of Li-Fraumeni syndrome, a rare group syndrome of familial cancers, has recently been identified. Patients with this inherited condition are highly susceptible to specific neoplasms, including early-onset breast cancers. The available evidence links Li-Fraumeni syndrome to inherited mutations of the tumor suppressor gene p53. Moreover, somatically acquired p53 mutations and gene deletions are common feature in breast cancer of sporadic origin. These findings suggest that germline p53 mutations are important in familial and, possibly sporadic, breast tumors. We have therefore screened lymphocyte DNA from 19 unrelated bilateral cancer patients for germline p53 mutations in exons 5, 6, 7 and 8. We have however detected no germline mutations by means of the single-strand confirmation polymorphism technique in any of the lymphocyte DNAs examined and conclude that p53 mutations are not generally involved in bilateral breast cancer.

Chromosomal deletions and K-ras gene mutations in human endometrial carcinomas

Forty-two endometrial carcinomas of various stages of progression were analyzed to search for loss of chromosomal regions and for point mutations of ras genes and amplification of Int-2 gene. This approach is particularly favorable for observation of genetic events and their significance in the process of neoplastic conversion by considering the clinico-pathological characteristics of each tumor. At least 3 genetic events, including 18q, 17p deletions, and point mutations at codon 12 of the K-ras gene, are implicated in the development of endometrial carcinomas. Likely targets for allelic losses on chromosomes 18q and 17p are the DCC gene and the p53 gene sequences, respectively. Overall numbers of allelic losses in individual tumors appeared to increase in case of advanced stage tumors, thereby indicating the association of allelic loss accumulation with tumor progression. The genetic features seen in 2 juvenile-type adenocarcinomas and 2 clear-cell carcinomas suggested the possibility that etiological factors providing selective pressure for particular mutation sub-sets during carcinogenesis are probably heterogeneous.

Distinct hypermethylation patterns occur at altered chromosome loci in human lung and colon cancer

Regional increases in DNA methylation occur in normally unmethylated cytosine-rich areas in neoplastic cells. These changes could potentially alter chromatin structure to inactivate gene transcription or generate DNA instability. We now show that, in human lung and colon cancer DNA, hypermethylation of such a region consistently occurs on chromosome 17p in an area that is frequently reduced to homozygosity in both tumor types. Over the progression stages of colon neoplasia, this methylation change increases in extent and precedes the allelic losses on 17p that are characteristic of colon carcinomas. We also show on chromosome 3p that regional hypermethylation may nonrandomly accompany chromosome changes in human neoplasia. Increased methylation is consistent in small-cell lung carcinoma DNA at two 3p loci that are constantly reduced to homozygosity in this tumor, but it is not seen in colon cancer DNA, in which these loci are infrequently structurally altered.

Growth inhibition by anchorage-deficiency is associated with increased level but reduced phosphorylation of mutant p53

Human breast carcinoma MCF-7 cells seeded on type I collagen-coated dishes were provided with an anchor via the collagen receptor, integrin, and grew as actively as those in plastic tissue culture dishes. In contrast, cells seeded on a layer of soft agar became anchorage-deficient and their growth was significantly inhibited, although the cell viability and the cell cycle distribution were unaffected. Immunoprecipitation analysis revealed that mutant p53 was phosphorylated at tyrosine in the anchorage-provided cells. In contrast, the p53 in the anchorage-deficient cells was present in 2-fold greater amount, but was phosphorylated to a lesser extent. Addition of a potent protein-tyrosine kinase inhibitor, herbimycin A, to the anchorage-provided cells caused an elevated level of p53, and inhibitions of cell proliferation and p53 phosphorylation, without interfering with the cell adhesion to the substratum. These results demonstrated that the growth inhibition by anchorage-deficiency or by herbimycin A is associated with an elevated p53 level and reduced p53 phosphorylation at tyrosine.

Fractional allelic imbalance in human breast cancer increases with tetraploidization and chromosome loss

We have previously reported a complete allelotype study of 86 primary breast carcinomas, in which each non-acrocentric chromosome arm was studied with at least one polymorphic DNA-marker for the presence of allelic imbalance (AI, allelic loss or allelic gain) in the tumor. Here we report the statistical analysis of this data set, investigating the relationships between AI, DNA aneuploidy and several clinico-pathological parameters of tumor progression. AI on 13 different chromosome arms, including 3p, 11p, and 17p, correlated significantly with the total number of AI events at other sites, suggesting that they are progression-related events. AI at 1q and 16q did not show such a correlation and may thus represent earlier events. Mean fractional allelic imbalance (FAI) was significantly higher in flow cytometrically aneuploid tumors than in diploid tumors (0.27 vs. 0.17, p = 0.007), and was highest in hypotetraploid tumors (0.37). This suggests that tetraploidization followed by chromosome segregation may underlie the development of AI at multiple sites. No correlation was found between mean FAI and clinico-pathological variables such as lymph-node involvement, stage, age, estrogen-receptor content and development of distant metastases, although there was a noticeable trend towards impaired survival for those patients with a higher-than-median FAI value.

Loss of heterozygosity on chromosome 7q and aggressive primary breast cancer

Genetic alterations are believed to be important in the origin and dissemination of breast cancer. Cytogenetic rearrangements on chromosome 7 are common in breast tumours. We used the c-met proto-oncogene probe, which detects sequences on chromosome 7q31, to analyse tumour and blood leucocyte DNA samples from 245 patients with primary breast cancers. The pmetH polymorphic probe detected a high frequency of allele loss (40.5%) among the 121 informative (heterozygous) patients. This genetic alteration was not significantly associated with standard prognostic features including tumour size, histopathological grade, and lymph-node or steroid receptor status. However, patients with loss of heterozygosity on chromosome 7q31 in primary tumour DNA had significantly shorter metastasis-free survival (p = 0.00022) and overall survival (p = 0.0036) after surgery than patients without this alteration. These findings indicate that this region of chromosome 7 might be the site of a breast tumour or metastasis suppressor gene.

Molecular biology in the diagnosis and prognosis of solid and lymphoid tumors

The application of molecular biology to the study of human malignancies has led to tremendous gains in our understanding of their pathogenesis. Although their practical applications are still somewhat limited at this point, the use of molecular diagnostic tools is likely to grow at a very rapid rate as newer and more accurate prognostic markers are identified. The availability of reliable prognostic markers should allow earlier intervention in patients with aggressive disease but exhibiting only limited extent of disease at the time of initial diagnosis. Early intervention in such cases could realistically increase the probability of cure, since highly aggressive tumor cells are more likely to be eliminated by early institution of cytotoxic chemotherapy (4). The p53 tumor suppressor gene clearly represents the most promising potential prognostic marker at present, because of both the multiple phenotypic alterations caused by different p53 mutations and the high frequency of p53 mutations which have been observed in a variety of human cancers. Other prognostic markers related to oncogenes and tumor suppressor genes are almost certain to follow. Validation of new prognostic markers requires a knowledge of both histopathologic diagnostic criteria as well as the consequences for the patient of each diagnosis. There is bound to be some "shake-out" in the field of molecular diagnostics just as there was with other recently introduced techniques such as immunohistochemistry and flow cytometry which were found to provide additional useful information for some tumors and not for others. Since the clinical-pathologic studies needed for verification of putative prognostic markers require relatively long periods of follow up, progress in this area will almost certainly lag behind the ability of molecular biologists to identify new and potentially useful prognostic markers. Our collective ability to reap tangible gains in the clinical arena from our heavy investments in molecular biology and biotechnology depends to a large extent on open channels of communication between clinical and basic scientists. As our ever-increasing insights into oncogenic processes spawn new diagnostic and prognostic markers, our priorities should remain focused on those areas which are inadequately addressed by current methods, and we should avoid the technological trap of devising redundant solutions which increase the expense, but not the efficiency of patient care.

The role of the retinoblastoma gene in breast cancer development

The observation that the human retinoblastoma gene is inactivated in about 20% of breast carcinomas indicates that it may be important in the development of these tumors. The fact that the loss of RB1 expression correlates with the progression of the disease, and especially with the inability of the cells to differentiate, is consistent with the clinical observation that retinoblastoma does not occur in children in whom the target cells have already fully differentiated. This suggests that the normal function of RB1 is to promote differentiation. It is possible that the loss of the ability of a cell to differentiate contributes to its ability to grow in a foreign environment (metastasis), but this hypothesis remains to be tested. Our observation that the overexpression of RB1 suppresses the growth of these tumor cells in vitro is consistent with this hypotheses.

Overexpression of the p53 protein and allele loss at 17p13 in ovarian carcinoma

Mouse monoclonal antibodies PAb 240 and PAb 1801 which specifically immunoprecipitate p53 protein, were used to examine 27 fresh ovarian tumours (16 serous adenocarcinomas, six endometrioid carcinomas, one mucinous adenocarcinoma, one mucinous borderline tumour and three benign adenomas). Eleven out of 16 (69%) serous adenocarcinomas and one endometrioid tumour showed positive staining with one or both antibodies and none of the mucinous or benign tumours stained with either antibody. DNA from tumour and peripheral blood leukocytes was used to identify allelic deletions on chromosome 17p in tumours. 11/12 positively staining tumours showed less of heterozygosity (LOH) on 17p at the nearest informative locus to the p53 gene. In this series of ovarian tumours, LOH on 17p correlates closely with the aberrant expression of the p53 protein in a high proportion of advanced stage serous adenocarcinomas. This observation suggests that the p53 tumour suppressor gene is involved in the evolution of epithelial ovarian cancer (EOC) and may have prognostic significance.

Genetic alterations in glioma and medulloblastoma

Multiple genetic changes take place during tumor development and progression. These genetic changes result in inactivation of tumor suppressor genes and activation of proto-oncogenes. Frequent genetic changes observed in gliomas are losses of chromosomal regions on 9p, 10q, 13q, 17p and on 22. Loss of 10q is seen in more than 80% of the glioblastoma multiforme (GBM) tumors suggesting the presence of a gene critical for GBM formation on this chromosome. Amplification of epidermal growth factor receptor gene and expression of platelet derived growth factor and fibroblast growth factor genes are also common among gliomas. The most common genetic abnormality found in medulloblastomas is loss of 17p. The C-myc gene is amplified in a few primary tumors, but the incidence of amplification is higher in medulloblastoma derived cell lines. These findings suggest that the same two genetic processes, gene amplification and regional chromosomal loss, which characterize other primitive childhood neuroectodermal tumors such as retinoblastoma and neuroblastoma are also important in medulloblastomas.

Loss of constitutional heterozygosity on chromosome 5q in hepatocellular carcinoma without cirrhosis

Suppressor gene loci involved in the development of hepatocellular carcinoma (HCC) have not been fully identified. The aim of this study was to look for consistent allele loss, or loss of heterozygosity (LOH), in HCC which might represent such gene loci. We have prepared DNA from tumour and non-tumour material from 16 patients with HCC (nine with and seven without liver cirrhosis). Tumour DNA was compared with non-tumour DNA by Southern analysis performed with a panel of 22 probes recognising restriction fragment length polymorphisms assigned to chromosomes 1, 4, 5, 7, 9, 11, 12, 13, 14, 16, 17, 18 and 20. Non-tumour DNA from five of the seven patients with HCC without cirrhosis was heterozygous with the probe Lambda MS8 (5q35-qter), and in all five there was LOH in tumour DNA. Probes for other regions of chromosome 5 have as yet shown no LOH in this group of patients. Cirrhotic HCC patients exhibited LOH on chromosomes 1q and 5p but not in the region 5q35-qter. Both groups of HCC showed LOH on chromosome 17p13. Screening with other probes has not shown any consistent LOH in either group as yet. A comparison of LOH on chromosome 5 in seven patients with colorectal metastasis in the liver showed a different pattern, which suggests that the proposed tumour suppressor gene locus for HCC without cirrhosis on chromosome 5 appears to be distinct from the familial adenomatous polyposis coli gene.

The ability of simian virus 40 large T antigen to immortalize primary mouse embryo fibroblasts cosegregates with its ability to bind to p53

The large T antigen encoded by simian virus 40 (SV40) plays essential roles in the infection of permissive cells, leading to production of progeny virions, and in the infection of nonpermissive cells, leading to malignant transformation. Primary mouse embryo fibroblasts (MEFs) are nonpermissive for SV40, and infection by wild-type SV40 leads to immortalization and transformation of a small percentage of infected cells. We examined the ability of an extensive set of mutants whose lesions affect SV40 large T antigen to immortalize MEFs. We found that immortalization activity was retained by all mutants whose lesions are located upstream of codon 346. This includes a mutant lacking amino acids 168 to 346. We previously showed (M. J. Tevethia, J. M. Pipas, T. Kierstead, and C. Cole, Virology 162:76-89, 1988) that sequences downstream of amino acid 626 are not required for immortalization of primary MEFs. Studies by Thompson et al. (D. L. Thompson, D. Kalderon, A. Smith, and M. Tevethia, Virology 178:15-34, 1990) indicate that all sequences upstream of residue 250, including the domain for binding of tumor suppressor protein Rb, are not required for transformation of MEFs. Together, these studies demonstrate that the immortalization activity of large T antigen for MEFs maps to sequences between 347 and 626. Several mutants with lesions between 347 and 626 retained the ability to immortalize at nearly the wild-type frequency, while others, with small insertions at amino acid 409 or 424 or a deletion of residues 587 to 589, failed to immortalize. The abilities of mutant T antigens to form a complex with tumor suppressor protein p53 were examined. We found that all mutants able to immortalize retained the ability to complex with p53, while all mutants which lost the ability to immortalize were no longer able to bind p53. This suggests that inactivation of the growth-suppressive properties of p53 is essential for immortalization of MEFs.

Expression of p53 protein in infiltrating and in-situ breast carcinomas

Five antibodies directed against the whole or part of p53 protein have been used to detect the protein immunohistochemically in 70 infiltrating breast carcinomas and 10 ductal carcinomas in situ. Mutations are known to occur in different conserved domains, and the antibodies employed spanned the expected sites. p53 protein was identified in 53 per cent of infiltrating carcinomas using the antibodies PAb 240, PAb 1801, C19, and JG8. The antibody PAb 421 detected the protein in 31.5 per cent; all positive with the other antibodies. Well-differentiated oestrogen receptor-positive tumours had a low incidence of p53 detection. Variation in the percentage of reactivity was seen between carcinomas and in some cases between different antibodies in the same cancer. Those carcinomas with a high percentage of positive cells with all antibodies were more likely to have metastasized to nodes, be at an advanced stage, and be oestrogen receptor-negative/epidermal growth factor receptor-positive. There was no significant correlation with c-erbB-2 protein expression or retinoblastoma protein loss. p53 protein was detected in a high proportion of cells in three of the six comedo ductal carcinomas in situ studied but either not at all or at a lower level in tumours of the cribriform type. p53 mutations are common in breast carcinomas, but heterogeneity within individual tumours is frequent. Marked expression of p53 appears to relate to tumour progression.

Constant denaturant gel electrophoresis as a rapid screening technique for p53 mutations

At present, mutation of the p53 gene appears to be the most common genetic alteration found in human cancers. These mutations can occur within many different regions of the gene. We have developed a modification of denaturing gradient gel electrophoresis termed "constant denaturant gel electrophoresis" (CDGE), which provides a rapid and sensitive method to screen the four conserved regions within the p53 gene where the majority of p53 mutations have been reported. The sensitivity of CDGE was first tested with known p53 mutations in all four conserved regions. The CDGE technique was then used to screen 32 breast carcinomas that had been analyzed by immunohistochemical methods for altered p53 protein levels and whose DNA had already been shown to have loss of heterozygosity for a chromosome 17p marker. By immunostaining techniques, only 6 of the 32 tumors had elevated p53 expression. However, CDGE detected p53 mutations in 11 of the 32 tumors. DNA sequence analysis was performed to determine the nucleotide positions of these mutations in all 11 samples. Loss of heterozygosity for the pYNZ22 or p144D6 markers did not associate with either the loss of heterozygosity at the p53 locus or the mutations detected by CDGE. We conclude that CDGE is a rapid and effective technique to screen for p53 mutations.

The p53 tumour suppressor gene

The cell cycle is composed of a series of steps which can be negatively or positively regulated by various factors. Chief among the negative regulators is the p53 protein. Alteration or inactivation of p53 by mutation, or by its interactions with oncogene products of DNA tumour viruses, can lead to cancer. These mutations seem to be the most common genetic change in human cancers.

Genetic basis for p53 overexpression in human breast cancer

Overexpression of an activated form of the p53 protein may be involved in neoplastic transformation. We found widespread overexpression of p53 by immunohistochemical staining in 11 (22%) of 49 primary invasive human breast cancers. Northern blot analysis showed that this overexpression was not due to an increase in the steady-state level of p53 mRNA. The p53 gene was directly sequenced in 7 of these tumors with elevated levels of the protein and, in each case, a mutation that altered the coding sequence for p53 was found in a highly conserved region of the gene. Whereas 4 of these tumors contained only a mutant p53 allele, the other 3 tumors exhibited coding sequences from both a mutant and a wild-type allele. p53 mutations have previously been correlated with allelic loss of part of chromosome 17p that contains the p53 locus. Examination of all 49 breast tumors revealed a 61% frequency of deletion at or near the p53 locus. However, the presence of allelic deletion did not correlate with overexpression of the protein. Six tumors that were deleted but did not express high levels of the protein were sequenced and all retained a wild-type p53 allele. In this series of human breast cancers, overexpression of the p53 protein, not allelic loss on chromosome 17p, was always associated with mutation of the p53 gene.

Expression of mutant p53, c-erbB-2 and the epidermal growth factor receptor in transitional cell carcinoma of the human urinary bladder

Expression of the p53, the epidermal growth factor receptor (EGFr; c-erbB-1) and c-erbB-2 proteins was studied in 82 patients with primary transitional cell carcinoma of the bladder using an immuno-histochemical method. Strong or moderate staining was found in 18% of tumours for p53 with weaker staining in a further 36% giving a total of 54% of tumours stained for p53. Strong staining was found in 15% of tumours for c-erbB-2 and in 31% for the EGFr. Tumours invading the bladder muscle were significantly more likely to be strongly stained positively for p53 and/or EGFr compared with superficial tumours: only 15% of invasive tumours were stained negatively for both p53 and EGFr. No statistical association was found between p53 and EGFr expression. Weakly positive associations were found between the expression of c-erbB-2 and p53 and between muscle invasive tumours and increased expression of c-erbB-2. Alterations in the expression of p53, c-erbB-1 and c-erbB-2 were found frequently in human transitional cell carcinoma of the urinary bladder and may be of clinical use in defining patient sub-groups of differing prognosis.

Cytogenetic features of twenty-six primary breast cancers

Tumor preparations from 26 primary breast cancers were studied cytogenetically with G-banding, using a direct technique, synchronized short-term culture, or both. Two tumors had normal karyotypes, and 24 (92%) had chromosomal abnormalities. Nineteen tumors had chromosome 1 rearrangements, with 10 cases (40%) displaying distal short arm translocations (1p36). Other frequent breakpoints occurred at 3p21, 6q22-27, 11q21-25, 16q22-24, 17p, and 19q13. To seek primary rather than secondary cytogenetic changes, attention was directed toward tumors with diploid-range karyotypes (32-57 chromosomes per cell). Of four such tumors, three exhibited nonrandom involvement of chromosome 16q22. This, together with previously reported data, suggests that deletion or rearrangement of chromosome 16q21-24 may be a primary or specific event in a subset of breast cancers.

Cotranslation of activated mutant p53 with wild type drives the wild-type p53 protein into the mutant conformation

Activating mutations of p53 promote tumor progression. The mutant protein adopts a characteristic conformation, which lacks the growth suppressor function of wild-type p53. We show that mutant p53 can drive cotranslated wild-type p53 into the mutant conformation: a similar effect in vivo would block wild-type suppressor function with dominant negative effect. The cotranslational effect of mutant p53 on wild-type conformation depends upon interaction between nascent polypeptides and oligomerization of the full-length proteins. We also show that oligomers of p53 proteins can be induced to change conformation in a cooperative manner. Cell growth stimulation induces a similar conformational change in p53, and our present results indicate that this may involve allosteric regulation.

Molecular and cellular lesions associated with breast cancer progression

Breast cancer may be more than one disease with differing etiologies. At the molecular level, breast cancer may be the result of a complex, dynamic, and stochastic process where there is more than one way to accomplish each of the steps necessary for malignant growth. The well documented biologic heterogeneity of breast cancers may arise from the many possible molecular changes that can accomplish a given step with variable efficiency. Alternatively, this heterogeneity may also reflect various possible orders of acquiring the sum of steps necessary for malignant growth. We have attempted to describe some of the molecular changes associated with breast cancer in the context of this broad conceptual framework. We have found that the capacity for infinite growth in culture usually occurs at a late stage of malignant progression and is frequently associated with activating ras mutations. Loss of heterozygosity at chromosome 11p can occur either early or late in progression, while losses at chromosome loci 1q and 17p, although independent of each other, are found in primary breast cancers. Whether the same molecular and cellular changes are to be found in Japanese patients remains to be determined.

p53 expression in human breast cancer related to survival and prognostic factors: an immunohistochemical study

In a study of 90 breast cancer patients, tumour p53 protein expression was determined by immunohistochemistry using the monoclonal antibody PAb1801. Patient lymph node status and Bloom's grade were determined, and both oestrogen and progesterone status assessed, also by immunohistochemistry. Lymph node status, tumour grade, and progesterone receptor status all had a significant influence on survival. Patients with p53-positive tumours showed poorer survival but this did not achieve significance. p53 protein expression showed a significant relationship to high tumour grade and a weak correlation with negative oestrogen receptor status. The data suggest that p53 protein expression may be a marker of more aggressive carcinomas but that the prognostic power of expression is likely to be weak and unlikely, therefore, to be of clinical value. The results do not resolve whether detectable p53 protein expression represents a random product of dedifferentiation, or an important feature of the malignant phenotype, playing a key role in tumour behaviour. The number of patients in our study is small, however, and investigation of a larger series is clearly indicated.

Loss of heterozygosity on the short arm of chromosome 17 is associated with high proliferative capacity and DNA aneuploidy in primary human breast cancer

Loss of heterozygosity (LOH) on the short arm of chromosome 17 (17p) was found in 27 of 52 (52%) previously untreated primary breast cancers. There was a significant correlation between this 17p allelic loss and two parameters associated with aggressive tumor behavior: high cellular proliferative fraction and DNA aneuploidy. These correlations with high cellular proliferative fraction and DNA aneuploidy were not found in tumors with LOH at nine other chromosome locations. The p53 gene, a putative tumor suppressor gene located at 17p13, was examined for aberrations to determine whether it is the target for the 17p LOH in breast cancer. Unlike other types of human cancer, there were no homozygous deletions or rearrangements of the p53 gene, and only 2 of 13 (15%) were mutated in the conserved region where mutational "hot spots" have been previously located. Therefore, we hypothesize that, in breast cancer, either loss or inactivation of gene(s) on chromosome 17p other than the p53 gene or a different mechanism of p53 gene inactivation may be responsible for the observed high labeling index and DNA aneuploidy associated with LOH at 17p.

Chromosome aberrations and oncogene alterations in two new breast tumor cell lines

Two new breast tumor cell lines (UISO-BC-1 and UISO-BC-2) have been established from pleural effusions obtained from patients with confirmed diagnosis of breast cancer. Cytogenetic investigation shows several numerical and structural aberrations in both cell lines. Each cell line appears to have distinctive karyotypic aberrations. Although a common marker chromosome was not found in both cell lines, several breakpoints (i.e., 1q11, 3q11, 7p11, 9q11, and 13q11) were commonly involved in the marker chromosomes of both lines. Double minute (dmin) chromosomes were also observed in these two cell lines. Sixteen oncogene probes were used to study the oncogene amplification and overexpression; among these, only neu and c-myc probes detected multiple gene copies. A 10-fold amplification and a 20-fold overexpression of the neu were observed in the UISO-BC-1 line, whereas a threefold and a fivefold amplification of c-myc were found in UISO-BC-1 and UISO-BC-2, respectively. Moderately enhanced expression (sixfold) of c-myc was also observed in the UISO-BS-2 line. No gross rearrangement of these genes or aberrant RNAs was detected in these tumor cell lines.

Mutations in p53 do not account for heritable breast cancer: a study in five affected families

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Detection of loss of heterozygosity in the p53 gene in renal cell carcinoma and bladder cancer using the polymerase chain reaction

The human p53 gene, a putative tumor suppressor gene, has a polymorphism in amino acid residue 72. We recently developed a method of detecting codon 72 polymorphism in this gene by digestion of polymerase chain reaction-amplified DNA using an allele-specific restriction endonuclease. This polymorphism allows the identification of loss of heterozygosity for the coding region of the p53 gene in limited tissue samples in a short time without using radioactive materials. We examined 33 patients with renal cell carcinoma and 29 with bladder cancer; heterozygosity in the p53 gene was lost in 60% (6 of 10 cases) and 73% (8 of 11 cases) of the renal and bladder tumors, respectively. Additionally, the assay's sensitivity could be improved by using DNA extracted from frozen sections of the tumors. Because the proportions of tumor cells and nontumor cells could be assessed by microscopic evaluation of the frozen sections, we were able to minimize contamination from nontumor cells, which occasionally causes false readings of retained heterozygosity. This simple and sensitive method for detecting loss of heterozygosity in the p53 gene makes it possible to rapidly screen a large number of tissue samples and has the potential to be a useful diagnostic tool for a wide variety of human neoplasms.

Patterns of expression of the p53 tumour suppressor in human breast tissues and tumours in situ and in vitro

An extensive series of histological sections reflecting the various states of normal breast tissue, and a range of benign and malignant lesions, were examined for the expression of the p53 protein using a panel of anti-p53 antibodies. In 2 separate series the results of using frozen or methacarn-fixed, paraffin-embedded sections were compared. Strong positive staining for p53 was detected in over 50% of the malignant lesions when frozen sections were used. This number fell to just over 20% when methacarn-fixed sections were examined. In neither series was any p53 staining seen in normal breast or in the benign lesions. Studies by Western blotting on breast cell lines confirmed that this histological signal is due to a pronounced over-expression of the p53 protein. Earlier studies show that this over-expression is associated with mutation of the p53 gene. Mutation of the p53 gene with over-expression of the mutant protein is therefore one of the most frequent specific genetic changes in malignant breast cancer.

Cancer in the families of children with soft tissue sarcoma

The cancer experience among 754 first-degree relatives (mothers, fathers, and siblings) of a population-based series of 177 children with soft tissue sarcoma is reported. The current study represents an extension of our earlier work in which the authors found an excess of breast cancer in the mothers of 143 of these children. There were 40 cancers among all first-degree relatives, compared with 24.82 expected (relative risk [RR] 1.61, P = 0.006). There was no excess in fathers, but an excess of borderline significance was seen in mothers (RR 1.67, P = 0.0545), and a significant excess in siblings (RR 4.55, P = 0.0002), mainly due to carcinoma of the breast and pediatric tumors. Results of a step forward Cox multivariate analysis identified three variables in the index child which were independently associated with high cancer risk in relatives, as follows: age younger than 24 months at diagnosis; histologic type, embryonal rhabdomyosarcoma or other and unspecified soft tissue sarcoma; and male sex. It was possible, therefore, to identify a subgroup of children whose relatives are at high risk of early onset cancer (RR in this group 10.14). The pattern of cancers is consistent with the Li-Fraumeni syndrome. The authors conclude that a marked proportion of childhood soft tissue sarcoma has a genetic basis.

1p13 is the most frequently involved band in structural chromosomal rearrangements in human breast cancer

Cytogenetic data on 14 breast carcinomas were examined to determine which chromosome arms and bands are preferentially involved in structural chromosome changes. Chromosome arms 17p, 16q, and 1p and band 1p13 were found to be significantly involved. A review of the world literature confirmed 1p as being the most frequently involved arm in structural chromosome changes in breast cancer and 1p13 as being the band most frequently involved in such changes. The two sets of results were pooled, and the analysis of 113 tumours revealed 229 of 304 bands to be involved, with 1p13 affected in 20% of the tumours.

Frequent mutations in the p53 tumor suppressor gene in human leukemia T-cell lines

Human T-cell leukemia and T-cell acute lymphoblastic leukemia cell lines were studied for alterations in the p53 tumor suppressor gene. Southern blot analysis of 10 leukemic T-cell lines revealed no gross genomic deletions or rearrangements. Reverse transcription-polymerase chain reaction analysis of p53 mRNA indicated that all 10 lines produced p53 mRNA of normal size. By direct sequencing of polymerase chain reaction-amplified cDNA, we detected 11 missense and nonsense point mutations in 5 of the 10 leukemic T-cell lines studied. The mutations are primarily located in the evolutionarily highly conserved regions of the p53 gene. One of the five cell lines in which a mutation was detected possesses a homozygous point mutation in both p53 alleles, while the other four cell lines harbor from two to four different point mutations. An allelic study of two of the lines (CEM, A3/Kawa) shows that the two missense mutations found in each line are located on separate alleles, thus both alleles of the p53 gene may have been functionally inactivated by two different point mutations. Since cultured leukemic T-cell lines represent a late, fully tumorigenic stage of leukemic T cells, mutation of both (or more) alleles of the p53 gene may reflect the selection of cells possessing an increasingly tumorigenic phenotype, whether the selection took place in vivo or in vitro. Previously, we have shown that the HSB-2 T-cell acute lymphoblastic leukemia cell line had lost both alleles of the retinoblastoma tumor suppressor gene. Taken together, our data show that at least 6 of 10 leukemic T-cell lines examined may have lost the normal function of a known tumor suppressor gene, suggesting that this class of genes serves a critical role in the generation of fully tumorigenic leukemic T cells.

Characterization of chromosomal anomalies in human breast cancer. A comparison of 30 paradiploid cases with few chromosome changes

A comparison of chromosomal anomalies detected in 30 cases of breast cancer in females with near-diploid karyotypes is reported. The tumors, of which 20 were previously unpublished, were selected for the relatively low complexity of their karyotypes, among a sample of 118 cases. Almost all of the 151 structural rearrangements detected were unbalanced, and 67% of breakpoints were located in or had contact with heterochromatin. In cases with few anomalies, rearrangements of chromosomes 1 and/or 16 were very frequent, leading principally to a gain of 1q and loss of 16q. In cases with more anomalies (5-16), deletions involving 17p, 4p, 13, 6q, 8p, 9p, 11p, and 11q and gains of 1q and 8q were the most frequent. Homogeneously staining regions (HSR) were detected in 14 tumors, mostly on 8p (6/22) and chromosome 19 (3/22). No double minutes (dmin) were observed. We conclude that trisomy 1q and monosomy 16q are early chromosomal changes in breast cancer, whereas other deletions and gain of 8q are clearly secondary events.

Amplification and protein over-expression of the neu/HER-2/c-erbB-2 protooncogene in human breast carcinomas: relationship to loss of gene sequences on chromosome 17, family history and prognosis

c-erbB-2 gene amplification and protein over-expression were investigated in 89 primary tumours and 24 metastases from Norwegian breast cancer patients. Amplification occurred in 22.5% of the primary tumours and 50% of the metastases. The amplification was negatively correlated to the oestrogen receptor (ER) content in both the primary tumours and the metastases. No significant differences between amplified and non-amplified tumours were observed with regard to node status, clinical stage, tumour size or menopausal status, although correlations of borderline significance were found between node status, clinical stage and high degree of gene amplification. All the amplified tumours were of the invasive ductal type. Follow-up data of patients observed for more than 1 year showed a significantly higher recurrence rate in the c-erbB-2 amplified group. Allele loss of chromosome 17p and of 7q was seen in 55% and 48% of the tumours respectively. No significant correlation was found between these losses and clinico-histological parameters. More than 50% of the tumours with a loss of 17q sequences had an amplification of c-erbB-2 which is located on 17q12-21, indicating that only one of the chromosomes may be involved in the amplification of the c-erbB-2. A trend towards a correlation between loss of 17q and high degree of amplification were found. No correlation was found between positive family history of breast cancer and c-erbB-2 gene amplification, nor loss of 17p or 17q sequences. Our data support the hypothesis that amplification correlates with aggressive tumour behaviour, and thus may be used as a prognostic factor in breast carcinomas. The allele losses on 17p and 17q points to tumour suppressor gene or genes on this chromosome, although not as predisposing genes in families.

Frequent mutations in the p53 tumor suppressor gene in human leukemia T-cell lines

Human T-cell leukemia and T-cell acute lymphoblastic leukemia cell lines were studied for alterations in the p53 tumor suppressor gene. Southern blot analysis of 10 leukemic T-cell lines revealed no gross genomic deletions or rearrangements. Reverse transcription-polymerase chain reaction analysis of p53 mRNA indicated that all 10 lines produced p53 mRNA of normal size. By direct sequencing of polymerase chain reaction-amplified cDNA, we detected 11 missense and nonsense point mutations in 5 of the 10 leukemic T-cell lines studied. The mutations are primarily located in the evolutionarily highly conserved regions of the p53 gene. One of the five cell lines in which a mutation was detected possesses a homozygous point mutation in both p53 alleles, while the other four cell lines harbor from two to four different point mutations. An allelic study of two of the lines (CEM, A3/Kawa) shows that the two missense mutations found in each line are located on separate alleles, thus both alleles of the p53 gene may have been functionally inactivated by two different point mutations. Since cultured leukemic T-cell lines represent a late, fully tumorigenic stage of leukemic T cells, mutation of both (or more) alleles of the p53 gene may reflect the selection of cells possessing an increasingly tumorigenic phenotype, whether the selection took place in vivo or in vitro. Previously, we have shown that the HSB-2 T-cell acute lymphoblastic leukemia cell line had lost both alleles of the retinoblastoma tumor suppressor gene. Taken together, our data show that at least 6 of 10 leukemic T-cell lines examined may have lost the normal function of a known tumor suppressor gene, suggesting that this class of genes serves a critical role in the generation of fully tumorigenic leukemic T cells.

Adjuvant antiestrogen therapy for breast cancer. Past, present, and future

Laboratory investigations using animal models of breast cancer growth have indicated that the antiestrogenic compound tamoxifen is a tumoristatic agent. It is therefore effective in suppressing, rather than destroying, the breast tumor. Its use as an adjuvant in breast cancer management has been successful, with a proportion of women benefiting from long periods of tamoxifen treatment. All the initial studies recruited postmenopausal women, but tamoxifen is now proposed for the treatment of premenopausal women for an extended time. Naturally, there are many aspects of the toxicology of tamoxifen to consider; however, careful monitoring of clinical trials will determine the safety of the drug for the general patient population.

Loss of heterozygosity on chromosomes 17 and 18 in breast carcinoma: two additional regions identified

The loss of heterozygosity (LOH) at specific regions of the human genome in tumor DNA is recognized as evidence for a tumor-suppressor gene located within the corresponding region of the homologous chromosome. Restriction fragment length polymorphism analysis of a panel of primary human breast tumor DNAs has led to the identification of two additional regions on chromosomes 17q and 18q that frequently are affected by LOH. Deletions of each of these regions have a significant correlation with clinical parameters that are associated with aggressive breast carcinomas. Previous restriction fragment length polymorphism analysis of this panel of tumors has uncovered several other frequently occurring mutations. LOH on chromosome 18q frequently occurs in tumors with concomitant LOH of loci on chromosomes 17p and 11p. Similarly, tumors having LOH on 17q also have LOH on chromosomes 1p and 3p. This suggests that certain combinations of mutations may collaborate in the development and malignant progression of breast carcinomas.

Evidence implicating at least two genes on chromosome 17p in breast carcinogenesis

The DNA of paired tumour and blood leucocyte samples from a large series of breast cancer patients was analysed to map regions of loss of heterozygosity on chromosome 17. The high frequency of loss of heterozygosity on 17p was confirmed, and a third of informative tumours had also lost an allele at the long arm locus THH59. On the short arm two distinct regions of loss of heterozygosity were identified, in bands p13-3 and p13-1. The latter probably involves the structural gene p53, which has been implicated as an oncogene or as a tumour suppressor in various human cancers. 17p 13-3, however, showed a significantly higher frequency of loss of heterozygosity, and there was no correlation between allele losses at the two sites. Nevertheless, loss of heterozygosity at 17p 13-3 is associated with overexpression of p53 mRNA, suggesting the existence of a gene some 20 megabases telomeric of p53 that regulates its expression. Lesions of this regulatory gene seem to be involved in the majority of breast cancers.