Gene amplification and expression of the neu (c-erbB-2) sequence in human mammary carcinoma

Different Assays for Her-2/neu Evaluation in Breast Cancer

To evaluate different methodologic approaches for HER-2/neu analysis, we performed Southern, Northern, Western blot and histochemical assay on 112 samples from 86 primary tumors and 26 synchronous axillary metastatic lymph nodes of patients affected by operable breast cancer. Simultaneous statistical analysis of data obtained with the four methods (31 samples) showed that Western blot detected a higher percentage of alterations than the other assays (Cochran and Victor tests, 0.01 < p < 0.05). The same result was emphasized by pair analysis (McNemar, p < 0.05), which evaluated the assay data two by two. Immunohistochemical evaluations were more in accord with immunoprecipitation data when performed on frozen or Bouin-fixed, paraffin-embedded tissues than on formalin-fixed, paraffin-embedded tissues.

erbB-2 overexpression in human mammary epithelial cells confers growth factor independence

Previously, we demonstrated that human breast cancer cells with progressively elevated levels of constitutively tyrosine phosphorylated erbB-2 are independent of growth factors required by normal human mammary epithelial (HME) cells for proliferation in serum-free medium. To determine whether erbB-2 overexpression alone is sufficient to confer the growth factor-independence phenotype in HME cells, the spontaneously immortalized MCF-10A cell line and the HPV-16-immortalized H16N2 cell line were infected with the bicistronic retroviral vector pTPerbB-2 and tested for their ability to grow in the absence of specific factors. Selection of infected cells in G418-containing medium resulted in moderate levels of erbB-2 overexpression in approximately 40% of cells. The subpopulation of erbB-2 overexpressing cells could be selected for by culturing the cells in medium devoid of insulin. When MCF-10A or H16N2 cells were infected with pTPerbB-2 and directly selected in growth factor-deficient medium over long periods of time, populations of both cell lines emerged that expressed levels of erbB-2 protein equivalent to levels expressed by breast cancer cells with an erbB-2 gene amplification. Furthermore, overexpressed p185(erbB-2) was constitutively tyrosine phosphorylated in these cells. The levels of tyrosine phosphorylated p185(erbB-2) differed in the two recipient lines, with H16N2-erbB-2 cells having higher levels of activated receptor than MCF-10AerbB-2 cells. Furthermore, only the H16N2-erbB-2 cells were independent of both insulin and epidermal growth factor for growth in serum-free medium. Overexpression of erbB-2 also resulted in progressively increasing levels of tyrosine-phorphorylated erbB-3, without any significant changes in p180(erbB-3) levels. These studies demonstrate a direct relationship between the level of expression and activation of p185(erbB-2) and the requirements of HME cells for insulin-like and epidermal growth factor-like growth factors. The results also suggest that genetic alterations present in breast cancer cells, or mediated by HPV-16-induced alterations in pRb and p53, can influence the expression level and activation status of erbB-2 as well as erbB-3 and, in turn, their degree of growth factor independence.

ERBB2 oncogene in human breast cancer and its clinical significance

We reveiwed the relationships between ERBB2 amplification and/or overexpression in human breast cancer and the clinicopathological parameters described in the literature (97 studies involving 22,616 patients) in order to draw conclusions regarding its clinical interest. The mean of ERBB2 positivity (26%, ranging from 5 to 55%) is not dependent on the method used to evaluate ERBB2 amplification or overexpression. Despite the discrepancies observed between the different studies, several associations between ERBB2 positivity and the classical clinicopathological parameters were noted. There are clear relationships between ERBB2 positivity and the lack of steroid receptors, the histological subtypes of mammary tumours (ductal invasive and in situ), worse histological and nuclear grades, aneuploidy and high rate of proliferation. In univariate analyses, ERBB2 is strongly associated with poor prognosis. All these data indicate that ERBB2 is a marker of aggressiveness of the tumour. However, ERBB2 does not retain a clinical prognostic significance in multivariate analyses, since it is associated with several strong prognostic parameters. When considering the prognostic value of ERBB2 in relation to treatment, a significantly worse survival of the treated patients is noted in ERBB2 positive patients. This suggest that ERBB2 could be a marker of reduced response to chemotherapy and hormonal treatment. With respect to the tumour response to treatment, the results, provided as yet by pilot studies, remain controversial and further investigations are necessary to evaluate the predictive value of ERBB2. Finally, new therapeutic approaches targeting the cells overexpressing ERBB2 have been developed.

Serial serum c-erbB-2 levels in patients with breast carcinoma

BACKGROUND

Recently, the extracellular domain of the c-erbB-2 oncogene product (HER-2/neu) has been reported to be elevated in the serum of one-fourth of patients with metastatic breast carcinoma. The role of serum c-erbB-2 as a tumor marker, however, is still poorly defined. The purpose of this study was to evaluate the utility of serial serum c-erbB-2 levels as a tumor marker in patients with metastatic breast carcinoma.

METHODS

c-erbB-2 levels in the sera of patients with breast carcinoma were determined by an enzyme immunoassay that detects the extracellular domain of c-erbB-2. Serum c-erbB-2 levels were evaluated prior to treatment as well as throughout the course of treatment with second-line hormonal therapy employing either megestrol acetate or fadrozole, an experimental aromatase inhibitor.

RESULTS

Fifty-eight of 300 patients (19.3%) had elevated pretreatment serum c-erbB-2 levels. Of these 58 patients with elevated pretreatment c-erbB-2, 48 had more than 1 visit which enabled us to quantitate serial c-erbB-2 levels throughout the course of treatment. Of these 48 patients, 28 (58.3%) had serial c-erbB-2 values that correlated with the clinical course.

CONCLUSIONS

Serial serum c-erbB-2 levels did not show a high overall correlation with the clinical course in this group of patients with metastatic breast carcinoma treated with second-line hormonal therapy.

Transfected neu oncogene induces human prostate cancer metastasis

c-erb B2/neu has been demonstrated to be a transforming oncogene in both rodent and human prostatic epithelial cells. To understand the potential role of neu in human prostatic cancer progression, we used a transfer procedure to determine whether neu amplification/overexpression leads to increased tumor growth and metastasis. We chose an androgen-independent human prostatic epithelial cell line, PC-3, as the target for gene transfer. PC-3 cells were cotransfected with pSVneu-T (a point-mutated rat neu oncogene construct) and pSV2neo, and single-cell cloned. Fifty cell clones were isolated and characterized, of which two neu-transfected clones (N17 and N35) and a neo control clone (C32) were studied extensively with respect to neu gene integration, levels of neu mRNA and protein expression, anchorage-independent growth, and tumorigenic and metastatic potential. Results showed that: 1) Clone N35 contained 70 copies of the neu oncogene and a high level of neu mRNA transcripts. It acquired increased anchorage-independent growth potential in vitro and increased tumorigenicity in vivo. 2) Clone N17 contained 10 copies of the neu oncogene and a low level of neu mRNA transcripts. It did not acquire additional capability for anchorage-independent growth and tumorigenic potential as compared to the controls. 3) Despite an increased level of neu mRNA transcripts present in clone N35, there was no corresponding increase of the steady-state levels of neu protein in this particular clone. 4) When administered subcutaneously, none of the cell clones tested, including the control neomycin-resistant clone, acquired metastatic potential. However, clone N35 exhibited marked metastatic potential when administered orthotopically; this cell clone was found to disseminate widely to the lymph nodes, kidney, skeletal muscle, lung, liver, and bone. 5) When neu-transfected cell subclones from N35-induced primary and metastatic lymph node, kidney, and bone tumors were analyzed for cytoskeletal, extracellular matrix, and cell adhesion protein expression, the bone metastatic subclone exhibited increased levels of vimentin and collagen IV and decreased levels of cytokeratin and ICAM-1. These results, taken together, suggest that neu transfection induces secondary changes, which, rather than neu protein per se, are responsible for the acquisition of tumorigenic and metastatic potential of prostate cancer cells when an appropriate host microenvironment is present.

Analysis of cerbB2 expression using a panel of 6 commercially available antibodies

Results are presented of a study comparing cerbB2 (neu or Her2) expression as assessed immunohistochemically in breast neoplasia using a panel of 6 commercially available antibodies. The antibodies were examined utilizing conventional formalin fixed paraffin embedded tissue, and compared with molecular analysis of gene amplification. The aim was to determine the practical utility of each antibody, assessing ease of use, specific and non-specific staining characteristics, and expense, thus allowing a specific recommendation as to antibody of choice for immunohistochemical assessment of cerbB2 expression. Reassuringly, amongst the 38 breast lesions (36 carcinomas, 2 fibroadenomas) subjected to immunohistochemically (IHC) with the panel of 6 antibodies (Ab), no gross discrepancy of staining pattern was seen. Of the 38 cases, 10 were positive (26%), where at least one Ab demonstrated clear cytoplasmic membrane staining. Of a total of 45 breast lesions (43 carcinomas, 2 fibroadenomas), including all those examined by IHC, the total number of cases showing cerbB2 amplification by DNA analysis was 14 (31%). Using the DNA amplification as a base line for comparison, one Ab (No. 4) was found to stain 6 of the 14 cases of breast carcinoma that were assessed as showing amplification at the DNA level. Four Abs (1,3,5,6) stained 5 of these cases. However, Abs 3,4 and 6 displayed artefactual cytoplasmic staining (in the absence of membrane staining) that precluded the practical use of these reagents. Therefore, based on additional considerations of cost and ease of use, Ab No. 1 was finally chosen for recommendation from the 6 Ab panel.

Clinical therapy and HER-2 oncogene amplification in breast cancer: chemo- vs radiotherapy

One hundred and five breast cancer patients with stage T3/4, N+/-, Mo were treated at random either with a pre- and postoperative chemotherapy (A) (5-drug-combination + tamoxifen) or with a pre- and postoperative radiotherapy (B). Paraffin embedded tissue samples were prepared from tumor material taken by biopsy prior to therapy as well as at surgery from patients of both groups to estimate the HER-2 oncogene copy numbers before and after treatment. In 53 and 50% of the pretherapeutic samples the HER-2 gene was amplified in groups A and B, respectively. In the post-therapeutic group 60% of the chemotherapy and 48% of the radiotherapy patients, respectively, had low or high HER-2 oncogene copy numbers. In addition, HER-2 amplification before and after therapy was estimated in 28 patients. An increase of oncogene copy numbers could be detected in 21% of the chemotherapy patients, and a decrease was noted in 11%. No radiotherapy patient showed a rise, but 11% a loss of copy numbers. Although amplification of HER-2 oncogene was not found to be associated with overall survival as it was in many studies before, it could still be a predictor of clinical outcome and the cause of mammary carcinomas developing into stage T3/4.

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.

HER-2 and INT-2 amplification estimated by quantitative PCR in paraffin-embedded ovarian cancer tissue samples

Competitive polymerase chain reaction (PCR) systems were developed for rapid and quantitative estimation of HER-2 (c-erbB-2) and INT-2 oncogene amplification in paraffin-embedded ovarian cancer tissue samples. The beta-globin gene was used as reference and DNA from paraffin-embedded placenta tissue as single copy control. Reliability of the PCR method could be demonstrated by comparing dot blot data with PCR data of identical tumour samples. The PCR method was used to determine HER-2 and INT-2 copy numbers in 196 ovarian cancer samples. HER-2 and INT-2 were found to be amplified in 40 and 19%, respectively. In 8% HER-2 copy numbers were greater than five, but no high INT-2 copies were noted. Kaplan-Meier estimates did not reveal significant association with overall survival. Indirect correlation between HER-2 and INT-2 amplification was observed. The present PCR system is a valuable method for prospective and retrospective studies.

C-erbB-2-oncogene expression in breast carcinoma: Analysis by S1 nuclease protection assay and immunohistochemistry in relation to clinical parameters

The c-erbB-2 mRNA was detected by the S1 nuclease protection assay and Northern blotting in breast cancer tissues. In contrast to the Northern blot analysis which has been used in all recent publications concerning c-erbB-2 expression on the level of RNA, the S1-nuclease protection assay has distinct advantages with respect to sensitivity, reproducibility, and handling of radioactive probes. We compared the expression of c-erbB-2 in 120 breast carcinomas which were operated in the years 1989-1990 on the level of the mRNA (S1 nuclease protection assay) and the protein (immunohistochemistry), respectively. In general, results obtained with both methods were in good agreement. Only minor differences in classification were observed with 18 samples, all of them belonging to either the moderate or the weak c-erbB-2 expression phenotype. In addition, the level of c-erbB-2-protein was investigated by immunohistochemistry in 271 breast carcinomas which were operated in the years 1984-1987. Comparison of the level of c-erbB-2 expression with the patient history indicates that patients whose tumors had already metastasized to the axillary nodes showed a reduced overall and disease-free survival in the group with pronounced expression of the c-erbB-2 protein. Thus the strong expression of c-erbB-2 oncogene in primary breast cancers appears to be an additional and particular prognostic factor in lymph node positive patients.

Detection of c-erbB-2 activation in paraffin-embedded tissue by immunohistochemistry

Commercially available monoclonal antibodies were tested for their ability to detect increased levels of c-erbB-2 protein in formalin-fixed, paraffin-embedded breast carcinomas. Of five antibodies studied, four (TAB-250, CB11, 3B5, and N3/D10) showed strong cytoplasmic membrane reactivity in 23% (11 of 47) of routinely processed tumors, although interpretation of the immunoreactivity with 3B5 and N3/D10 occasionally was difficult due to cytoplasmic granular staining. Since the c-erbB-2 oncogene is activated by DNA amplification and overexpression of mRNA and protein, the same tumors were analyzed for c-erbB-2 activation by other techniques. c-erbB-2 activation in these 11 tumors was confirmed by immunohistochemistry of frozen tissue (nine of nine tumors), in situ hybridization (nine of 11 tumors), and Southern blot analysis (five of eight tumors). In some of these tumors the failure to demonstrate c-erbB-2 DNA amplification may be due to the small percentage of malignant cells. One additional tumor showed probable c-erbB-2 protein overproduction based on strong immunoreactivity with two antibodies (TAB-250 and CB11), although no definite activation could be demonstrated by additional techniques. Three other tumors (6%) showed equivocal c-erbB-2 protein overproduction based on weak immunoreactivity only with TAB-250, although unequivocal activation could not be demonstrated by additional techniques. The 32 carcinomas (68%) that showed no significant immunoreactivity with any antibodies in routinely processed tissue also showed no detectable c-erbB-2 activation by additional techniques. We conclude that TAB-250 and CB11 are reliable antibodies for detecting c-erbB-2 protein overproduction in routinely processed tissue. TAB-250 also weakly stains a few tumors showing no definite c-erbB-2 activation by other techniques. Two additional antibodies (3B5 and N3/D10) detect c-erbB-2 protein overproduction in paraffin-embedded tissue, but are more difficult to interpret. A fifth antibody, TA-1, is an excellent reagent for use on frozen tissue, but prolonged formalin fixation may impair recognition of its antigenic epitope.

Expression of the ERBB2 protein in benign and malignant salivary gland tumors

Fifty-two primary human salivary gland tumors were analyzed for expression of the p185ERBB2 protein using immunohistochemical and immunoblotting techniques. About 63% (33/52) of the tumors expressed the ERBB2 protein. The highest expression levels were detected among the carcinomas, where 32% of the tumors showed intense membrane staining in 25-100% of the tumor cells. In benign pleomorphic adenomas, the corresponding figure was only 12%. Clinical follow-up data available for 18 of the 19 patients with carcinomas suggested an association between high ERBB2 protein levels and poor prognosis as measured by recurrence of disease and/or the appearance of metastases. These results indicate that ERBB2 activation and overexpression could be an important genetic event with possible prognostic implications in a subset of malignant salivary gland tumors.

Growth factors and oncogenes in human solid tumors: clinical aspects

Growth factors, growth factor receptors and oncogenes have been extensively studied in human tumors for some years. The purpose of this paper is to review the clinical results obtained in human cancers and their predisposing conditions or high risk groups as well as their relation with clinical, pathological characteristics and their prognosis.

Neu (C-erbB-2) oncogene in breast cancer and its possible association with the risk of distant metastases. A retrospective study and review of literature

By immunohistochemical staining C-erbB-2 (neu) oncogene was found on the cell membrane in 19 out of 44 primary breast cancers from a pathology archive. No obvious relation was found between neu oncogene, age, and lymph node status and tumor size. There was a tendency towards smaller primary tumors and more estrogen receptor-negative tumors in the oncogene-positive group. No case of distant metastasis during follow-up was found among the oncogene-negative patients, while 6 oncogene-positive patients developed such metastases. This suggests that the neu oncogene is an independent prognostic factor, which might predict the development of distant metastasis. Further studies including more patients and long-term survival analysis are, however, needed in order to evaluate the prognostic significance of the neu oncogene.