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

HER-2/Neu Gene in Primary and Local Metastatic Axillary Lymph Nodes in Human Breast Tumors

In order to verify whether the HER-2/neu gene is involved in the initial phases of neoplastic disease or in its progression, we evaluated the amplification and overexpression of this gene in the primary tumor and in synchronous metastatic axillary lymph nodes of 26 women with operable breast cancer.

HER-2/neu was amplified in 35% and overexpressed in 33% of the primary sites; similar percentages were found in lymph nodes. The clear correlation between the two disease sites regarding gene, mRNA and protein levels, supports the hypothesis that this gene is involved in the initial and invasive phases of neoplasia. Its actual role with respect to other biological tumor characteristics during the metastatic process should be investigated further.

HER2 status in operable breast cancers from Vietnamese women: Analysis by immunohistochemistry (IHC) and automated silver enhanced in situ hybridization (SISH)

BACKGROUND

HER2 amplification has been reported to occur in 19-30% of breast cancers in women from Western countries. Little is known about the HER2 status in breast cancers from Vietnamese women. The aim of this study was to assess the HER2 status in Vietnamese women with operable breast cancer using immunohistochemistry and silver in situ hybridization techniques.

MATERIAL AND METHOD

Tissue blocks from 242 Vietnamese women with invasive primary breast carcinoma were stained by immunohistochemistry (IHC) and a dual silver in situ hybridization (SISH) for assessing HER2 status. The analysis followed international recommendations with a semi-quantitative grading of the reaction in four levels, "0", "1+", "2+" and "3+". The HER2 gene amplification was assessed by calculating the ratio of HER2/chromosome 17 in 20 tumor cell nuclei. A ratio of <1.8 was classified as non-amplification and a ratio >2.2 indicated tumors with gene amplification. A ratio between 1.8 and 2.2 was equivocal.

RESULTS

Using IHC, 39% of the tumors strongly expressed "3+" the HER2 protein. An intermediate level "2+" of the protein was found in 11% while 50% showed no or low "0/1+" levels of protein expression. Gene amplification was found in 95% and 46% of the tumors with high "3+" and intermediate "2+" levels of protein expression, respectively. Thus, 41% of the patients had tumors with HER2 amplification. The concordance between IHC and SISH was 87%. Gene amplification was more frequent in ER negative than in ER positive tumors, 57% versus 33%, respectively. Additionally, tumors from postmenopausal women were amplified in 55% as compared to 36% in premenopausal women.

CONCLUSIONS

HER2 gene amplification was found in 41% of Vietnamese breast cancers; this level is considerably higher than that previously found in a series of Swedish breast cancer women. The HER2-positive tumors were more often found in post-menopausal women than in ER negative tumors.

Enhancement of the p27Kip1-mediated antiproliferative effect of trastuzumab (Herceptin) on HER2-overexpressing tumor cells

The oncogenic activity of the overexpressed HER2 tyrosine kinase receptor requires its localization in the plasma membrane. The antitumor effect of anti-HER2 antibodies (Abs) is mainly dependent on receptor downregulation and comprises p27Kip1-mediated G1 cell cycle arrest. However, one major limitation of anti-HER2 therapy is the reversibility of tumor growth inhibition after discontinuation of treatment caused by the mitogenic signaling associated with cell surface receptor re-expression. We found that the level of p27Kip1 upregulation, inhibition of Cdk2 activity and magnitude of G1 arrest induced by the humanized Ab trastuzumab (Herceptin, HCT) on BT474 and SKBr3 HER2-overexpressing breast cancer cells correlates with the level of cell surface receptor. Thus, continuous exposure of cells to HCT for 72 hr results in downregulation of the cell surface receptor and a concurrent increase in the level of p27Kip1 protein. Discontinuation of Ab exposure after the first 8 hr results in failure to upregulate p27Kip1 and arrest of cell cycle progression. We show that the lysosomotropic amine chloroquine (CQ) augments receptor internalization in HER2-overexpressing cells either pretreated or continuously treated with HCT and leads to an increased and sustained inhibitory effect. The enhanced CQ-dependent loss of functional HER2 from the cell surface resulted in sustained inactivation of the serine/threonine kinase Akt, upregulation of p27Kip1 protein and inhibition of cyclin E/Cdk2 activity. Potentiation of the inhibitory effect of HCT by CQ was directly related to loss of HER2 from the plasma membrane since prevention of Ab-mediated receptor endocytosis by engagement of the receptor with immobilized HCT abrogated the effect of CQ.

Quantitation of erbB2 positivity for evaluation of high-risk patients

BACKGROUND

Because trastuzumab therapy is expected to be effective in a large fraction of erbB2 (HER-2/neu) overexpressing breast cancers, it is important to find the optimal method for evaluation of erbB2 positivity, and the patient group at greatest risk of dying without this therapy.

AIM

We evaluated erbB2 immunopositivity in breast cancer with the aim of finding a high-risk group for primary trastuzumab therapy.

METHODS

Three hundred and seventeen samples were evaluated with an immunostaining index. Optimal cut point was systematically tested, and the effect of bcl-2 status on survival in the high-risk group was studied.

RESULTS

Among N+ patients the index value 1.5 reflected the biggest difference in survival. There was a significant correlation between erbB2 positivity and bcl-2 negativity. ErbB2 was a prognosticator among postmenopausal, N+, and postmenopausal N+ patients. In multivariate analysis, erbB2 was the best prognosticator among postmenopausal N+ patients. Six out of seven N+ patients with erbB2 index 1.5 or above died including all postmenopausal patients. Bcl-2 positivity was associated with longer survival in the erbB2 positive patient group.

CONCLUSIONS

The most obvious patients for primary trastuzumab therapy in breast cancer are N+ patients with high erbB2 immunostaining index (> 1.5) and bcl-2 negative immunostaining. In our material 2% of all breast cancer patients fell in this category. This patient group should be selected for testing trastuzumab in the primary treatment.

The significance of histological determination of HER-2 status in breast cancer

Since the identification of the novel transforming gene neu in rat neuroblastomas in 1981, and the subsequent cloning of the human equivalent HER-2, there have been considerable developments concerning the role and value of HER-2 in human breast cancer. Early studies found gene amplification in 20-30% of breast carcinomas, with most studies linking this to poorer survival. Numerous antibodies have been generated against the oncoprotein and in many instances overexpression, as defined by membrane staining of breast cancer cells, correlated with gene amplification. Many studies, but not all, have found an association between HER-2 reactivity and poor prognosis. HER-2 can also be detected in high-grade ductal carcinoma in situ. HER-2 status can also aid prediction of response to hormonal and chemotherapy, but the present interest lies in the humanized monoclonal antibody against HER-2 (Herceptin) that has been developed. This is only of value if there is over-expression of HER-2 by a breast cancer, and so a reliable, accurate method of determination of HER-2 status is required. Immunohistochemistry is widely used and is relatively simple, with no major equipment requirements. However, there are variations in results with different antibodies and standardized methods, with controls for evaluating extent of reactivity required. Fluorescent in situ hybridization, which detects gene amplification, is an alternative approach that can be used with fixed embedded tissue but the technique is less widely available. HER-2 is the first oncoprotein involved in breast cancer in which there has been direct translation from the laboratory to the patient.

Type 1 protein tyrosine kinases in benign and malignant breast lesions

AIMS

To determine their significance, we examined the expression pattern of the four epidermal growth factor receptor (EGFR) family members as well as the phosphotyrosine kinase activity in breast tumour tissues.

METHODS AND RESULTS

Fifty-three malignant breast tumours, four breast cancer cell lines, and 10 benign breast tumours were investigated. Fifty-three per cent (28/53) of the malignant tumours expressed EGFR protein, and the majority of these positive tumours were strongly positive. Eighty per cent (8/10) of the benign tumours also expressed EGFR protein, but all in a lower or moderate level. An association between EGFR expression and increasing malignancy grade was found in the group of infiltrating ductal carcinomas. Of the malignant tumours, 35.8% (19/53) expressed c-erbB-2 protein and 17% (9/53) c-erbB-3 protein, while no expression of c-erbB-2 and c-erbB-3 proteins was found in the benign tumours. Contrary to previous reports, we observed c-erbB-4 receptor protein to be less expressed in the malignant breast tumours. The 'normal' breast epithelial cells adjacent to the malignant tumours and the benign tumours demonstrated intensified membrane staining for c-erbB-4, while a number of the malignant tumours demonstrated a weak cytoplasmic staining or were negative. However, several malignant tumours with strong membrane staining for the c-erbB-4 protein were also found. No simple association between the expression of the four receptors and phosphotyrosine kinase activity was found.

CONCLUSION

Our study has revealed a complex expression pattern of the EGFR family members in breast tumour cells. While the data about EGFR, c-erbB-2, c-erbB-3 and phosphotyrosine are largely in line with what has been reported, we found the c-erbB-4 protein expression to be decreased in the malignant tumours.

Variability in loss of constitutional heterozygosity across loci and among individuals: association with candidate genes in ductal breast carcinoma

Genes involved in the metabolic activation or detoxification of environmental carcinogens may contribute to breast cancer susceptibility by influencing rates of somatic mutation. To examine this hypothesis, we studied the association between loss of constitutional heterozygosity (LOH) in ductal breast tumors and allelic variability in genes that regulate the metabolism of environmental carcinogens. LOH was measured by typing the tumor and normal tissue of 28 breast cancer cases at 33 chromosomal loci by using highly polymorphic tetranucleotide repeat markers. Genotypes in non-tumor tissue were also measured at the cytochrome P450 1A1 (CYP1A1), cytochrome P450 2D6 (CYP2D6), glutathione-s-transferase mu (GSTM), epoxide hydrolase (EH), and NAD(P)H:quinone oxidoreductase (NQO1) loci. The observed proportion of LOH was 11% overall and ranged from 0% to 37% across loci. LOH greater than 20% was observed on chromosomes 1p, 2p, 10q, 11q, 17p, and 18q. The observed proportion of LOH ranged from 0% to 67% among individuals. An elevated proportion of LOH was observed for genotypes at CYP2D6 (17% for the 1/1 and 1/2 genotypes vs 8% for the 2/ 2 genotype), NQO1 (13% for the 1/2 and 2/2 genotypes vs 8% for the 1/1 genotype), and GSTM (15% for the null genotype vs 7% for the wild-type genotype). No elevated proportion of LOH was observed for genotypes at CYP1A1 (12% for the 1/2 genotype vs 10% for the 1/1 genotype) or EH (11% for the 1/1 genotype vs 10% for the 1/2 genotype). There was no correlation of LOH with any other tumor characteristic such as estrogen- or progesterone-receptor status or number of positive lymph nodes. These results suggest that the proportion of LOH varies substantially across loci and among individuals. Interindividual variability in LOH may thus be explained in part by genes that regulate the metabolism of environmental carcinogens.

Determination of ErbB2 protein in breast cancer tissues by different methods. Relationships with other biological parameters

Four different methods to measure in parallel the erbB2 protein expression (p185neu) were evaluated in order to: a) compare two enzyme immunoassays with the immunohistochemical assays (IHC) and western blotting (WB) and b) extrapolate eventual relationships between erbB2 and biological parameters. Tissue samples from 248 patients with primary breast cancer were consecutively assayed. We used two different cut-off levels for WB, ELISA, and EIA, defined as follows: 1) the highest level of expression of non malignant tissue was chosen as the discriminant threshold between 'low' and 'elevated' samples: 2) the elevated group was further subdivided into two subgroups: 'intermediate' and 'high', according to their median value. According to the first cut-off, the results were considered 'elevated' in about 52% of cases with the three biochemical methods, while using the second cut-off the percentage lowered to about 26%. Considering this cut-off, the concordance rates between the paired biochemical methods ranged between: 78.4% (WB vs EIA), 93% (ELISA vs EIA), and 82.6% (ELISA vs WB). The comparison between biochemical and immunohistochemical methods gave these concordance rates: 82% (WB vs IHC), 90.5% (ELISA vs IHC), and 85.5% (EIA vs. IHC). According to the first cut off level, 27.5% of tumor samples showed IHC detectable p185 levels, in agreement with other immunohistochemical studies. The relationship between high erbB2 and estrogen and progesterone receptors showed an inverse association. No relationship was found between erbB2 and axillary lymph node positivity or tumor size. In short, the results of the four methods seem generally well correlated; nevertheless, it appears that different methodological approaches of measuring p185neu are not completely equivalent, and there is a need for an authoritative standardization and quality control for clinical applications.

Variations in c-erbB-2 proto-oncogene status in breast cancer tumors as detected by two different cDNA probes

We examined 232 breast carcinomas for c-erbB-2 amplification by Southern analysis using two different cDNA probes. Using these same probes, 95 of these tumors were also examined for mRNA expression by Northern analysis. Amplification was detected in 20 and 17% of the tumors with the probes pHER 2 and pCER 204, respectively, but only 10% showed amplification with both probes. A significantly higher incidence (p < 0.01) of mRNA overexpression was detected with the pHER 2 probe (34%) compared with the pCER 204 probe (16%), with only 11% of tumors demonstrating overexpression with both probes. A total of 10 tumors (11%) exhibited amplification as well as overexpression with pHER 2, whereas significantly fewer (3%) manifested both abnormalities with the larger pCER 204 probe (p < 0.05). Amplification of c-erbB-2, as detected with the pHER 2 probe but not with the pCER 204 probe, was significantly associated with the absence of both estrogen and progesterone receptors (p < 0.05 and p < 0.01, respectively). No relationship was found with other clinical prognostic indicators, such as nodal involvement and metastases. As determined by either probe, overexpression was not associated with prognostic indicators. There was no significant difference in the c-erbB-2 status of tumors from different racial groups.

The prognostic value of c-erbB2 in primary breast carcinomas: a study on 942 cases

To assess the practical prognostic value of c-erbB2, we performed a study on 942 invasive ductal carcinomas treated with primary surgery between 1980 and 1986 in our center. We evaluated its expression by immunohistochemistry in paraffin-embedded tissue using a polyclonal antipeptide antibody. Of 942 tumors, 229 (24%) showed a positive membrane staining. We observed a significant association between c-erbB2 and Scarff-Bloom-Richardson grading (p < 0.0001) and a negative correlation between c-erbB2 and both estrogen and progesterone receptors (p < 0.0001). In our analysis, with respect to overall survival (OS), relapse-free survival (RFS), and metastasis-free survival (MFS), c-erbB2 was statistically significant (p < or = 0.0001) for the whole group and the node-positive subgroup. In multivariate analysis, c-erbB2 appeared to be an independent variable for RFS and MFS in the node-negative group. However, in our hands, c-erbB2 had a poor prognostic value in comparison with the classical prognostic variables such as histological grade, nodal status (N), hormonal receptor status (estrogen and progesterone receptors), and tumor size, and it did not supersede the classical parameters.

p53 gene alterations in special types of breast carcinoma: a molecular and immunohistochemical study in archival material

The p53 locus on the short arm of chromosome 17 at 17p13.1 was examined for small genomic deletions and mutations in 23 formalin-fixed, paraffin-embedded cases of special types of breast carcinoma (six medullary, seven apocrine, five differentiated tubular, and five papillary). p53 mutations in the evolutionarily conserved exons 5-9 were detected in 11 cases (four apocrine, two papillary, two medullary, and three differentiated tubular), using the novel non-radioactive PCR-based Hydrolink mutation detection enhancement (MDE) method, and confirmed by direct sequencing of the PCR products. Missense mutations causing amino acid substitutions were evenly distributed among exons. One case of apocrine carcinoma showed a polymorphism at codon 213 (CGA-->CGG). Twelve out of 23 cases were found to express a strong nuclear signal against CM-1 and DO-7, two anti-p53-specific antibodies. Small genomic deletions in the vicinity of the p53 locus were detected in 11 tumours (three papillary, three differentiated tubular, two medullary, and three apocrine carcinomas), using the multiplex PCR method. No statistical correlation was found between deletions at 17p13.1 and p53 mutations (P < 0.5). In addition, p53 mutations and immunoexpression correlated with the c-erbB-2 gene product, an oncogenic protein that has been implicated in cell cycle control (P < 0.001). Our findings suggest that genomic alterations of the p53 gene are quite common events associated with special types of breast carcinoma, particularly of the apocrine subtype, but the prognostic value is unlikely to be of clinical importance.

Familial breast cancer and genes involved in breast carcinogenesis

Breast cancer has often been reported to run in families, and the most important risk factor for the disease is a family history of breast cancer. Numerous pedigrees and segregation analyses have suggested an autosomal dominant transmitted susceptibility to breast cancer. Familial breast cancer occurs alone or associated with other cancers in clinically distinguishable syndromes. Such cases may be characterized by early onset, bilateral disease, prolonged survival, and anticipation, mainly seen as a higher penetrance or earlier onset in subsequent generations. Studies of patients and tumors from these families as well as sporadic cases have led to localization and/or identification of a number of genes implicated in breast carcinogenesis of familial and sporadic breast cancer.

Immunohistochemical detection of HER2/neu in patients with axillary lymph node negative breast carcinoma. A study of epidemiologic risk factors, histologic features, and prognosis

BACKGROUND

Numerous studies have examined the prognostic significance of HER2/neu (HER) expression in patients with axillary lymph node negative breast carcinoma. Although some investigations suggest that the presence of the altered expression of HER is prognostically unfavorable, the subject remains controversial. This study explores the interaction of HER with three aspects of axillary lymph node negative breast carcinoma: epidemiologic risk factors, tumor histopathology, and prognosis.

METHODS

Immunohistochemical staining for HER was performed on 10% formalin fixed paraffin embedded primary carcinomas from 440 patients with negative axillary lymph nodes with a median follow-up of 119 months.

RESULTS

The immunohistochemical expression, or lack thereof, of HER did not prove to be prognostically significant in this group of patients with axillary lymph node negative breast carcinoma. There was also no consistent association with epidemiologic risk factors. The most striking results concerned the relationship of HER to histopathologic features of the carcinomas. Medullary carcinoma differed from other tumor types because it was HER(+) substantially less often (10%) than were other ductal (49%) or lobular (43%) carcinomas.

CONCLUSION

The results obtained in this study suggest that the immunohistochemical demonstration of HER is not a reliable prognostic indicator for patients with axillary lymph node negative breast carcinoma. This marker was not associated with major epidemiologic risk factors; however, there was a significant correlation between HER and the phenotypic features of breast carcinoma because medullary carcinoma is rarely HER(+). Although the associations may not be a strong enough basis for refining the classification of breast carcinoma, they could be useful for diagnosing individual patients. The changes in HER that are detectable by the immunohistochemical methods used in this study probably do not occur in the earliest stages of mammary carcinogenesis.

Detection of c-erbB-2 related protein in sera from breast cancer patients. Relationship to ERBB2 gene amplification and c-erbB-2 protein overexpression in tumour

The level of a c-erbB-2 related protein was determined in sera from 168 breast carcinoma patients, 12 females with benign breast disease, and 66 female controls using an ELISA (enzyme linked immunosorbent assay) kit. Elevated c-erbB-2 related protein level was detected in one of 13 preoperative sera (8%), two of 62 postoperative sera from patients without recurrent disease (3%), and 55 of 93 sera collected at recurrent disease (59%). Elevated serum levels were detected significantly more often in patients with distant metastases than in patients with recurrent disease restricted to loco-regional areas (68% versus 19%). Presence of elevated serum level was associated with ERBB2 gene amplification and c-erbB-2 protein overexpression in tumour. None of the patients who had normal ERBB2 gene copy number in tumour had elevated serum levels. Although the usefulness in postoperative prediction of the presence of micrometastases is somewhat questionable, the results suggest c-erbB-2 related protein to represent a novel tumour marker in serum and other body fluids from breast cancer patients at the time of diagnosis and during treatment monitoring.

Induction of multidrug resistance (MDR) by transfection of MCF-10A cell line with c-Ha-ras and c-erbB-2 oncogenes

To investigate the relationship between oncogene activation and appearance of multidrug resistance (MDR) we transfected the human breast epithelial cell line MCF-10A, negative for the expression of the P-glycoprotein, with c-Ha-ras and/or c-erbB-2 oncogenes. The appearance of the MDR phenotype was then studied by evaluating mdr-1 mRNA expression, the presence of P-glycoprotein on the cell membrane and the onset of doxorubicin resistance, together with the effect of the reversing agent verapamil. We found that only MCF-10A transfected with both c-Ha-ras and c-erbB-2 oncogenes acquired the MDR phenotype.

Genetic alterations of chromosome 17 in human breast carcinoma studied by fluorescence in situ hybridization and molecular DNA techniques

Fluorescence in situ hybridization (FISH) with a chromosome 17 centromere-specific probe was used together with Southern blot analyses and PCR amplification of a polymorphic segment to characterize 13 breast carcinomas. Cells with an abnormal number of chromosome 17 centromeres were found mixed with disomic cells in nine of the 13 tumors studied. Three of the four cases found to have a normal number of chromosome 17 centromeres had DNA alterations restricted to allelic imbalance of the two most distal markers on 17p; the fourth had no detectable alterations. In contrast, of the seven tumors found to have genetic alterations elsewhere on chromosome 17, all had more than one cell population when examined for numerical chromosome 17 alterations. The present data support the hypothesis that alterations at the distal short arm of chromosome 17 represent earlier events in the tumorigenic process than do the other chromosome 17 abnormalities observed. The results of molecular DNA studies interpreted as allelic imbalance of distal 17p markers in most cases probably reflect chromosomal rearrangements like loss of specific loci, rather than monosomies and large deletions. The report illustrates the usefulness of FISH when added to current molecular DNA techniques.

Reduction of telomeric length and c-erbB-2 gene amplification in human breast cancer, fibroadenoma, and gynecomastia. Relationship to histologic grade and clinical parameters

BACKGROUND

Telomeric deletions contribute to genetic instability and may represent an important mechanism of carcinogenesis. Amplification of the c-erbB-2 gene has been demonstrated in breast carcinoma. The clinical significance of telomeric deletions and c-erbB-2 gene amplification therefore was studied in patients with breast disorders.

METHODS

The Southern blot analysis was used to measure telomeric length as well as the c-erbB-2 gene amplification of breast carcinomas, adjacent normal breast tissues, fibroadenomas, and cases of gynecomastia.

RESULTS

Significant reductions in telomeric length and concentration were observed in all breast tissues when compared to placental DNA. Mean telomeric lengths were lowest in carcinomas and fibroadenomas. There were no significant differences, however, in the telomeric lengths among tissues from patients with breast carcinomas, fibroadenomas, or gynecomastia. The degree of telomeric deletion correlated significantly with histologic grade and was most notable in Grade 3 (scirrhous) breast carcinoma. The extent of telomeric deletion reflects the histologic aggressiveness of breast carcinoma, and telomeric reduction already can be seen in the adjacent normal breast tissues from patients with breast cancer. c-erbB-2 gene amplification was observed in 26.8% of the patients with breast carcinoma. c-erbB-2 gene amplification was not observed, however, in patients with fibroadenomas or gynecomastia. The degree of telomeric deletion did not correlate with c-erbB-2 gene amplification, tumor size, clinical stage, steroid receptors, or prognosis. Telomeric length was shorter in lymph node-negative tumors than in lymph node-positive tumors.

CONCLUSIONS

These findings indicate that a shorter telomere length reflects growth advantage in breast cancer tissue, and telomeric reduction may promote cancer progression.

Allelic loss on distal chromosome 17p is associated with poor prognosis in a group of Brazilian breast cancer patients

We examined loss of heterozygosity (LOH) for two loci on chromosome 17p (D17S5 and TP53), and erbB-2 gene amplification, in primary breast cancers from 67 Brazilian patients. We identified two distinct regions of LOH on chromosome 17p, one spanning TP53 and the other a more telomeric region (D17S5). Based on a short-term follow-up, Kaplan-Meier analyses of patients' disease-free survival showed that patients with LOH for D17S5, but retaining heterozygosity for TP53, were at higher risk of recurrence (P = 0.007) than those who retained heterozygosity for D17S5. Bivariate analyses indicated that patients with LOH for D17S5 alone had an increased risk of recurrence (hazard ratio = 7.2) over patients with erbB-2 amplification (hazard ratio = 3.7), when compared with patients with neither alteration (hazard ratio = 1.0). Further, lymph node-positive patients whose tumours had both LOH for D17S5 and erbB-2 gene amplification had a higher risk of recurrence than patients whose tumours had neither of these genetic alterations. Our data confirm previous reports of a putative tumour-suppressor gene, distinct from TP53, on distal chromosome 17p which is associated with breast cancer. They further suggest that LOH for loci in this region may provide an independent indicator to identify patients with poor prognosis.

Genetic alterations on chromosome 17 in human breast cancer: relationships to clinical features and DNA ploidy

We analyzed DNA from 105 primary breast cancers to assess amplification of the ERBB2 gene and loss of heterozygosity (LOH) on chromosome 17 using 4 polymorphic markers, and investigated the relationships of these genetic alterations to clinicopathological characteristics including DNA ploidy. Amplification of the ERBB2 gene was observed in 28% of the tumors. ERBB2 was amplified in tumors of all clinical stages and amplification was significantly linked to lymph node metastasis. LOH at D17S5 was observed in 28 of 57 informative tumors, while 17 of 62 informative tumors showed allelic loss at TP53. Among the 37 tumors informative for both loci, 32% showed LOH at these loci and 49% retained both alleles, indicating that there was a significant relationship between LOH at D17S5 and at TP53. We also examined LOH at the D17S74 and NME1 loci on chromosome 17q. LOH at D17S74 and NME1 was observed in 20% and 22% of the informative tumors, respectively, but there was no significant association between LOH at these loci. Of the 4 loci tested, LOH at TP53, D17S74, and NME1 was associated with clinical stage. Lymph node metastasis was correlated with LOH at NME1. Moreover, allelic loss was more frequent in aneuploid tumors than in diploid tumors. These results suggest that certain combinations of genetic alterations on chromosome 17 may cooperate in the development and/or progression of breast cancer. Furthermore, it seems likely that analysis of these alterations in breast cancer patients may provide useful prognostic information.

What's new in breast cancer? Molecular perspectives of cancer development and the role of the oncogene c-erbB-2 in prognosis and disease

The oncogene c-erbB-2 is frequently amplified in human breast carcinoma. The c-erbB-2 gene is present as a single copy in normal cells, and has been mapped to chromosome 17 in the region 17q 12-21.32. c-erbB-2 encodes a transmembrane glycoprotein known as p185. The intracellular component of p185 has tyrosine kinase activity; the extracellular domain has a structure resembling a growth factor receptor. c-erbB-2 amplification, p185 overexpression and levels of transcribed c-erbB-2 specific messenger RNA have been studied in a large number of breast carcinomas using a variety of techniques. In general, overexpression of p185 oncoprotein reflects various levels of DNA amplification, though in some cases amplification can be detected in the absence of overexpression of p185 and similarly overexpression of p185 can be present without detectable levels of c-erbB-2 amplification. This findings suggests that multiple mechanisms may be responsible for overexpression. c-erbB-2 amplification and/or overexpression occurs in almost all cases of high grade duct carcinoma in-situ, but has been reported in only 10%-40% of infiltrating duct carcinoma. c-erbB-2 amplification or overexpression occurs rarely in invasive lobular carcinoma, and has not been detected in ductal or lobular epithelial hyperplasia, or in atypical ductal or atypical lobular hyperplasia. It is generally believed that c-erbB-2 amplification/overexpression is an important independent prognostic indicator in breast carcinoma, identifying a subset of patients with poor prognosis tumours, particularly if axillary node metasases are present. However, many unanswered questions remain regarding c-erbB-2 and its role in breast cancer development and progression. The causes of c-erbB-2 amplification are unknown. There is no evidence of mutations in the human gene which might cause amplification or overexpression. The significance of the differences in levels of c-erbB-2 amplification/overexpression in in-situ duct carcinoma and associated invasive duct carcinoma has not been established. Amplification or overexpression have not been reported in atypical duct hyperplasia, a proposed precursor of duct carcinoma in-situ, yet overexpression occurs almost always in high grade duct carcinoma in-situ. c-erbB-2 may play a critical role in the development of a clonal in-situ, proliferation of high histological grade, yet does not obviously influence the acquisition of an invasive phenotype. We would postulated that this instability in amplification/overexpression is of biological significance, and if better understood may aid in the study of progression of human breast carcinoma.

Concurrent abnormal expression of ERBB-2, EGFR, and p53 genes and clinical disease progression of breast carcinoma

Metastatic phenotype in human solid tumors is believed to follow stochastic acquisition of structural genetic aberrations-so-called multistep tumor progression. We tested this hypothesis in breast carcinoma by immunostaining 89 stage-heterogeneous cases for the products of three genes (p53, ERBB-2, and EGFR) which are frequently altered in this tumor system. Variable relationships were observed between advanced disease stage and immunostaining for individual gene products (ERBB-2 - p = 0.05, EGFR - p = 0.02, p53 - p = 0.12, Chi Square test). Regional or distant metastases at presentation correlated with multiple oncogene/tumor suppressor gene expression abnormalities: node negative -59% none positive, 29% one positive, 12% two or more positive, vs. node positive -37% none positive, 23% one positive, 39% two or more positive (p = 0.01). Only 2/12 (17%) of tumors with distant metastases at presentation were negative for abnormal expression of any of these gene products, and 7/12 (58%) were positive for two or three. Among axillary node negative patients who developed recurrences, 67% exhibited staining for at least one gene product, compared to only 27% of those without recurrences (p = 0.02). All 5 cases with abnormal staining for each gene product had regional or distant metastases at presentation and recurred. In multivariate analysis, individual expression of p53 outweighed expression of ERBB-2 and EGFR in correlation with outcome. These data suggest clinical neoplastic progression of breast carcinomas correlates with cumulative genetic events detectable by protein expression. Short term recurrence, however, may correlate more closely with abnormal expression of p53 than with EGFR or ERBB-2.

Prognostic significance of TP53 alterations in breast carcinoma

Constant denaturant gel electrophoresis (CDGE) was used to screen 179 breast carcinomas for mutations in the conserved regions of the TP53 gene (exons 5 through 8). Mutations were found in 35 of 163 primary tumours (21%) and in 5 of 16 metastases (31%) and resided predominantly in exon 7. The majority of the mutations were G:C-->A:T transitions. Immunohistochemistry demonstrated nuclear accumulation of p53 protein in 35 of 162 primary tumours (22%) and in four of 15 metastases (27%). TP53 mutation was strongly associated with nuclear accumulation of p53 protein. In total 42 of 163 primary tumours (26%) and 5 of 16 metastases (31%) were demonstrated to contain TP53 alterations (mutation and/or nuclear protein accumulation). TP53 alteration in primary tumour was significantly associated with the following parameters: positive node status, T status > 1, negative oestrogen receptor status, negative progesterone receptor status, presence of ERBB2 gene amplification, and invasive ductal histology. Furthermore, there were statistically significant associations, independent of other prognostic factors, between TP53 alterations in primary tumour and disease-free and overall survival.

C-erbB-2 oncoprotein immunostaining in serous effusions

The product of c-erbB-2 gene is detected in a proportion of carcinomas from various sites and is generally associated with a high degree of malignancy. A series of 58 effusions containing malignant cells and 16 cytologically negative serous effusions was assessed by immunocytochemical methods for c-erbB-2 expression using the monoclonal antibody NCL-B11, which recognizes the internal domain of the c-erbB-2 oncoprotein. Both alcohol-fixed smears and cell blocks from formalin-fixed specimens were used. A crisp, clear cut membrane-associated positive staining was evident in 51% (30/58) malignant effusions and was restricted to metastatic adenocarcinomas. Breast and ovarian cancers showed the highest incidence of positivity. Mesotheliomas as well as non-neoplastic effusions were consistently negative. Paraffin blocks from formalin-fixed cells displayed a weak immunoreactivity when compared with their alcohol-fixed counterparts. The study shows that the c-erbB-2 oncoprotein can be easily identified in standard cytological smears: it can be of assistance in differentiating adenocarcinomas from mesotheliomas, and in selected cases it can provide a further prognostic indicator, replacing tissue immunohistochemistry.

Gene amplification and tumor progression

Proto-oncogenes are the genes which are most frequently found amplified in human tumor cells. Acquisition of a drug-resistant phenotype by gene amplification is frequent for in-vitro cultured cells but is very rare in human tumors. Proto-oncogenes amplified in human tumors belong essentially to one of three families (erbB, ras, myc) or to the 11q13 locus. Amplification is always specific for the tumor cells and is not found in constitutional DNA of the patient, indicating that amplification of the gene is selected for during tumor growth. For genes of the first three families, amplification results in overexpression in most of the cases. These are strong arguments in favor of a role of this amplification in tumor progression. The gene whose overexpression is the driving force for the selection of the amplification of the 11q13 locus is not known. The prad1 gene is presently a good candidate. Amplification of one type of proto-oncogene is generally not restricted to one tumor type. However, the N-myc gene is amplified mainly in tumors of neuronal or neuroendocrine origin and L-myc amplification is restricted to lung carcinomas. To understand the role of proto-oncogene amplification and overexpression in tumor progression it is necessary to know the function of the corresponding protein in the cell. erbB proteins are transmembrane receptors for growth factors. ras genes encode small GTP-binding proteins which are possibly involved in signal transduction. The myc proteins are transcription factors. The expression of the c-myc gene is induced a few hours after cells of various types have been induced to proliferate. The genes of these three families therefore encode proteins which appear to be involved in signal transduction. It is possible that overexpression of one of them, as a result of gene amplification, makes the cell a better responder to low levels of growth stimuli. For several genes which are found amplified in human tumors, it was shown that overexpression of the normal protein could confer a transformed or tumorigenic phenotype to in-vitro cultured cells. In addition, several studies on animal and human tumor-derived cell lines with an amplified proto-oncogene have established a relationship between proto-oncogene amplification and the tumorigenic phenotype. In neuroblastomas, it was proposed that down-modulation of MHC Class I antigens is a consequence of N-myc amplification and that this could be important in the progression toward a metastatic phenotype.(ABSTRACT TRUNCATED AT 400 WORDS)

C-erbB-2 oncogene product expression depends on tumour type and is related to oestrogen receptor and lymph node status in human breast carcinoma

Although over-expression of the C-erbB-2 oncogene product can be detected on formalin-fixed, paraffin-embedded sections from tumours of the human breast, fixation results in a considerable loss of immunostaining for this protein. In this study, C-erbB-2 expression was studied immunohistochemically on frozen sections in 63 infiltrating carcinomas, 3 phyllodes tumours, 15 fibroadenomas and 16 cases of fibrocystic disease. The value of C-erbB-2 expression as a prognostic indicator in ductal carcinomas was examined by seeking an association with known prognostic indicators. C-erbB-2 over-expression was confined to ductal carcinomas of the breast and was positively correlated with tumour size, grade, oestrogen receptor status and the presence of metastatic deposits in axillary lymph nodes. Only the association with lymph node and oestrogen receptor status were statistically significant. No evidence of a correlation between C-erbB-2 expression and growth fraction (as assessed with the Ki-67 antibody) was demonstrated in the cases studied. Formalin fixation was associated with the loss of immunoreactivity in all cases studied. 75% of cases which were positive on frozen sections were negative in paraffin sections. These results highlight the significance of the method of fixation used in studying C-erbB-2 expression. They confirm the association between C-erbB-2 expression and known prognostic indicators.

Expression of c-erbB-2 protein, neuron-specific enolase and DNA flow cytometry in locally advanced transitional cell carcinoma of the urinary bladder

Expression of c-erbB-2 protein, neuron-specific enolase (NSE) and DNA ploidy was studied by immunohistochemistry and flow cytometry in formalin-fixed and paraffin-embedded specimens from 104 patients with locally advanced transitional cell carcinoma of the bladder. Positive membrane bound c-erbB-2 staining was found in 15% of the tumours, and 38% of the tumours were positive for NSE. Only one tumour stained positively for both NSE and c-erbB-2. Expression of c-erbB-2 protein and NSE was neither correlated to tumour stage nor to histopathological grade. The frequency of non-diploid tumours was 78% in 49 c-erbB-2/NSE negative tumours, 98% in 40 NSE positive tumours, and 100% in 16 c-erbB-2 positive tumours (P = 0.004). Whether the c-erbB-2 expression is a useful prognostic marker in addition to other conventional parameters, remains to be shown.

Four separate regions on chromosome 17 show loss of heterozygosity in familial breast carcinomas

Two genes predisposing females to autosomal dominant breast cancer are located on chromosome 17. Mutations in the p53-gene on the short arm have been shown to predispose females to early onset breast cancer in families with the rare Li-Fraumeni syndrome. Another locus on 17q (BRCA1), was found to be linked to the disease in a subset of families with breast cancer. In order to determine the involvement of tumour suppressor genes at these loci in tumour development, we studied allele losses for markers on chromosome 17 in 78 familial breast carcinomas. The analysis used six polymorphic DNA markers, three on each arm. We found support for at least four separate regions displaying allele losses on chromosome 17: the p53-region, the distal part of 17p, the BRCA1 region and the distal part of 17q. The frequency of allele losses on distal 17p (16%) is low in these familial tumours compared with the previously reported incidence in sporadic tumours (> 50%), whereas the frequency of losses at the p53 locus and on 17q was similar to sporadic tumours (5%-40%). These data suggest that several regions on chromosomal 17 can harbour tumour suppressor genes involved in tumour development of familial breast cancer.

Loss of heterozygosity at chromosome 17p is associated with HER-2 amplification and lack of nodal involvement in breast cancer

Sixty DNA samples from breast carcinoma (BC) patients were analyzed by Southern blot to examine certain oncogene and anti-oncogene alterations. Amplification of the HER-2 oncogene was detected in 15 tumours (25%), c-myc in 2 (3%) only and HER-1 in none. Distribution of Hras-1 oncogene alleles in BC did not significantly differ from that seen in healthy donors. Not a single case of RB-1 anti-oncogene alteration and only one of p53 suppressor gene abnormality was found when appropriate cDNA copies were used as probes. With the use of DNA polymorphic markers, loss of heterozygosity (LOH) was revealed at chromosome 17p (probe YNZ-22) in 18 of 39 (46%) informative cases, at 17q (probe THH-59) in 10 of 34 (29%) and at 11p (probe Hras-1) in 8 of 30 (27%). The only significant correlation between these genetic alterations and the clinical characteristics of the tumours studied was the association of LOH at 17p with node-negative BC (p < 0.02). Also, the tendency for correlation (p < 0.2) between HER-2 amplification and loss of 17p sequences was revealed: 7 of 10 amplification-positive, but only 11 of 29 amplification-negative BC possessed LOH of YNZ-22 locus.

Amplification of c-erbB-2, int-2 and c-myc genes in node-negative breast carcinomas. Relationship to prognosis

Primary tumours from 100 Norwegian node-negative breast carcinoma patients were examined for c-erbB-2, int-2, and c-myc proto-oncogene amplification. c-erbB-2, int-2, and c-myc amplification was found in 12.1% (12 of 99), 8.6% (8 of 93), and 1.1% (1 of 89) of the samples respectively. All the c-erbB-2 amplified tumours were of the ductal type, and all the int-2 amplified tumours were oestrogen receptor positive. No other significant or borderline significant associations between gene amplification and clinical or histopathological parameters were found. Relapse occurred more frequently in patients with c-erbB-2 gene amplification (relapse in 33.3% of the patients with c-erbB-2 amplification compared to 20.7% in the non-amplified group), but the difference was not statistically significant, int-2 amplification was not associated with increased risk of relapse, whereas the prognostic value of the c-myc amplification could not be evaluated.

Activated oncogenes and putative tumor suppressor genes involved in human breast cancers

Cytogeneticists first proposed that the karyotypic abnormalities identified on chromosomes 1, 3, 6, 11, 13, 16, 17, and 18 supported a genetic basis for breast cancer. Such abnormal banding patterns, however, may represent either loss-of-function or gain-of-function molecular events. RFLP analyses have since confirmed that 20-60% of primary and spontaneous human breast tumors exhibit allelic losses on these same chromosomes, although the exact genes involved at these chromosomal sites remain largely unknown. Knowledge gained about the Rb-1 and p53 tumor suppressor genes at 13q14 and 17p13 in breast and other human tumors supports the paradigm that for any chromosomal locus, allelic loss associated with a mutation in the remaining tumor allele signifies an involved tumor suppressor gene. Given this paradigm, there are nearly a dozen putative breast tumor suppressor genes under active investigation, with most investigators now focusing on various chromosome 17 loci. Among the known proto-oncogenes found activated in breast cancer, amplification of c-erbB-2 at 17q21 is the most widely studied and clinically significant gain-of-function event uncovered to date, occurring in about 20% of all primary breast tumors. The involvement of this overexpressed membrane receptor has engendered interest in related tyrosine kinase receptors, such as EGFR, IR, and IGF-I-R, as well as their respective ligands, which may be overexpressed in a greater fraction of tumors, contributing to the autocrine and paracrine regulation of breast cancer growth and metastasis. New attention is being given to the potentially oncogenic function of structurally altered nuclear transactivating steroid hormone receptors, such as ER, whose overexpression has long been used to determine endocrine therapy and prognosis for individual breast cancer patients. While c-myc was one of the first known proto-oncogenes to be found amplified and overexpressed in human breast cancers, the actual incidence and clinical significance of its activation remain disputed and in need of further study. Lastly, we can expect greater clarification about the importance of various 11q13 genes found coamplified in nearly 20% of primary breast cancers, and pursuit into the intriguing possibility that a cyclin-encoding gene represents the overexpressed locus of real interest in this amplicon. Virtually all of these important genetic abnormalities identified thus far are associated with but not restricted to human breast cancers. The absence of identifiable molecular defects relating to the tissue specificity of this malignancy must be considered a substantial gap in our basic understanding of breast carcinogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Retinoblastoma and p53 gene expression related to relapse and survival in human breast cancer: an immunohistochemical study

Inactivation of tumour suppressor genes may be an important aetiological factor in many human cancers including breast. In a study of 197 breast cancer patients, tumour tissue was snap-frozen at the time of surgery and immunohistochemical labelling for p53 protein and retinoblastoma (Rb) gene product carried out using an indirect immunohistochemical technique. Tumours were scored by two independent observers for the intensity of nuclear staining for each antibody. Expression of p53 protein showed a significant association with a shorter time to relapse (P = 0.03) and death (P = 0.02) (log rank test). p53 expression did not correlate with nodal status but showed a significant association with high tumour grade (P = 0.001). Rb gene expression showed no relationship to relapse or survival but loss of expression showed a significant correlation with positive lymph node status. The manner by which these proteins might act to determine tumour behaviour remains to be established.

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.

p53 allele losses, mutations and expression in breast cancer and their relationship to clinico-pathological parameters

The p53 locus on the short arm of chromosome 17 at 17p 13.1 was examined for loss of heterozygosity, mutation, mRNA and protein expression in 60 primary breast cancers. Allele loss around the p53 locus was detected in 19/45 informative tumours (42%). p53 mutations in the evolutionarily conserved exons 5 to 9 were detected in 17/60 (28%) by amplification mismatch and confirmed by direct DNA sequencing. p53 mRNA expression was detected by Northern blot in 36/59 (61%) of tumours, and p53 protein expression using antibody 1801 on frozen-tissue sections in 13/44 of the tumours examined. p53 mutation was significantly associated with oestrogen-receptor-poor tumours (p less than 0.01) and hence with poor prognosis, but not with other clinical or pathological parameters. There was no statistical correlation between loss of heterozygosity around the p53 locus at 17p13.1 and p53 mutation. Furthermore, p53 mutation was not associated with p53 expression detected by immunohistochemical staining with antibody 1801 or as p53 mRNA. In addition, events on 17p (allele losses, p53 mutation, p53 expression) were independent of c-erbB-2 expression. In breast cancer, by contrast with colorectal, lung and ovarian cancer, there appears to be no clear association between p53 DNA abnormalities and p53 expression.

The c-erbB-2 protein in primary and metastatic breast carcinomas

Material from 41 patients with primary breast carcinoma and lymph node metastases at the time of primary surgical intervention was immunostained for c-erbB-2 protein, neuron-specific enolase (NSE), and estrogen receptors. Thirty of the primary breast carcinomas were of ductal type. Six were classified as infiltrating lobular carcinomas, 2 were apocrine, 1 was mucinous, and 1 was a tubular carcinoma. One tumor could not be classified as ductal or lobular by light microscopic examination alone. The number of lymph node metastases available varied from 1 to 14 per case (median, 3.9). Nine (22%) of the primary breast carcinomas (8 ductal and 1 apocrine) expressed c-erbB-2 protein and showed c-erbB-2 gene amplification; 12 expressed NSE immunoreactivity. None expressed both markers. Estrogen receptor immunoreactivity was present in 23 of the 41 cases, including 9 of the NSE-positive cases. C-erbB2- protein-positive metastases were present in 18 cases (44%), and in 13 cases all metastases were immunostained. In 5 cases the expression of c-erbB-2 protein varied from metastasis to metastasis. NSE immunoreactivity was expressed in 10 cases, and in 3 cases with minor NSE-positive cell populations the metastatic lesions expressed c-erbB-2 protein as well. All 9 primary breast carcinomas expressing c-erbB-2 protein had lymph node metastases with c-erbB-2-immunoreactive tumor cells. Eight of the 9 c-erbB-2 protein-negative primary tumors with metastases expressing c-erbB-2 protein showed no amplification of the c-erbB-2 gene.(ABSTRACT TRUNCATED AT 250 WORDS)