Insulin-like growth factor and epidermal growth factor independence in human mammary carcinoma cells with c-erbB-2 gene amplification and progressively elevated levels of tyrosine-phosphorylated p185erbB-2

Growth factor-independent proliferation is an essential aspect of the transformation process. To study the influence of c-erbB-2 overexpression on the autonomous growth of human mammary cancer cells, we used a series of non-neoplastic and neoplastic human mammary epithelial cell lines isolated from a patient with intraductal and invasive ductal carcinoma of the breast. The non-neoplastic cell line, H16N-2, which expresses a normal level (single gene copy) of c-erbB-2, was used for comparison with the neoplastic cell lines. Both the metastatic tumor cell lines, 21MT-1 and 21MT-2, showed equivalent amplification of the c-erbB-2 gene; however, 21MT-1 cells showed a higher level of c-erbB-2 overexpression. Therefore, the H16N-2, 21MT-2, and 21MT-1 cell series forms a distinct gradient of progressively increasing c-erbB-2 gene expression. Furthermore, the overexpression of c-erbB-2 in the 21MT cell lines was concordant with increases in the constitutive tyrosine kinase activity of p185^erbB-2 measured in the absence of exogenous growth factors in culture. Normal mammary epithelial cells require both insulin-like growth factor (IGF)-1 (or supraphysiological concentrations of insulin) and epidermal growth factor (EGF) to proliferate under serum-free conditions in culture. By contrast, 21MT-2 cells showed a reduced requirement for IGF but still required EGF to proliferate. 21MT-1 cells did not require either insulin or EGF to proliferate. Therefore, the progressive increases in constitutive p185^erbB-2 tyrosine kinase activity in the 21MT-2 and 21MT-1 cell lines was directly correlated with IGF independence and combined IGF and EGF independence under defined conditions in culture. Experiments using conditioned media and anti-IGF-1 receptor and anti-EGF receptor neutralizing antibodies showed that the growth-factor independence of the tumor cells did not involve detectable IGF- or EGF-like autocrine activity expressed by the 21MT cells. Furthermore, neu differentiation factor/heregulin, a ligand that indirectly activates p185^erbB-2 by direct binding to erbB-3 receptors, potently stimulated the proliferation of the growth factor-dependent H16N-2 cells (which expressed cerbB-2 and c-erbB-3 but not c-erbB-4) in the absence of both IGF and EGF. Thus, HRG-induced mitogenesis mimicked the autonomous growth seen in the 21MT cells that have the highest level of constitutive p185^erbB-2 activation. These data support the hypothesis that the constitutive activation of p185^erbB-2 in human mammary carcinoma cells causes growth-factor independence by directly activating multiple signal-transduction pathways that substitute for both IGF and EGF during proliferation. © 1996 Wiley-Liss, Inc.     

Expression of c-erbb-2 protein and epidermal growth factor receptor in endometrial carcinomas correlation with clinicopathologic and sex steroid receptor status

Background. The c-erbB-2 (HER-2/neu) protein is a membrane glycoprotein growth factor receptor showing molecular homology with the epidermal growth factor receptor (EGFR). In endometrial carcinomas, little is known about the relationship between the expression of c-erbB-2 protein and that of EGFR. Methods. The immunohistochemical reactivity of monoclonal antibodies against both of these proteins was examined in 34 endometrial carcinomas, and the presence or absence of correlation with the clinicopathologic features or with the immunohistochemical expression of sex steroid receptors (estrogen receptor [ER] and progesterone receptor [PR]) was analyzed. Results. Of the 34 patients, 22(64.7%) had c-erbB-2 protein-positive and EGFR-negative tumor, and 8 (23.5%) had tumor positivity for both proteins. Four patients had tumors negative for both proteins. ER or PR positivity was found in 24 (70.6%) of the 34 patients. Intense immunostaining for c-erbB-2 protein was found in 5 (14.7%) of the 34 patients but was not correlated with the stage or grade of differentiation in endometrial carcinoma. However, expression of EGFR in addition to c-erbB-2 protein was more frequently observed with advancing stage of disease and was inversely correlated with the grade of differentiation and with the expression of ER or PR of the tumor. Conclusion. The expression of EGFR, in addition to that of c-erbB-2 protein, is an important event that presumably is linked with progression or with a poorly differentiated state of endometrial carcinomas.     

Quantitative Analysis of c-erbB-2 Protein in Breast Cancer Tissue by Enzyme Immunoassay

The introduction of c-erbB-2 protein to clinical medicine asa prognostic indicator and tumor marker is desired. The authorsdetermined the concentration of c-erbB-2 protein in 81 breastcancer tissues by enzyme immunoassay. The concentration of c-erbB-2protein in breast cancer tissues showed a broad spectrum. Asignificant correlation was observed between tissue c-erbB-2protein concentration and estrogen receptor status or immunohistochemicaldetermination. In patients with distant metastases, there wasa close association between c-erbB-2 protein concentration inthe primary tumor and serum c-erbB-2 protein level. Cases witha high tumor concentration of c-erbB-2 protein (>1000U/mgtotal protein; 18.5% of cases) had a poor prognosis. From theabove, we concluded the measurement of tissue c-erbB-2 proteinby enzyme immunoassay to be clinically useful in breast cancer.     

Epidermal growth factor receptor and c-erbB-2 expression in normal breast tissue during the menstrual cycle

Summary EGF receptor (EGF-R) and c-erbB-2 are homologous tyrosine kinase transmembrane receptors. They are involved in controlling proliferation, and probably differentiation, of normal breast epithelial cells, and their expression has been linked to the prognosis of breast cancer. Their physiological roles in normal breast tissue remain to be elucidated, as most studies to date have involved breast cancer cell lines. We studied the location of EGF-R and c-erbB-2 in 100 samples of normal breast with standard immunohistochemical methods and double-labelling techniques. EGF-R was mainly expressed on the stroma and myoepithelial cells, whereas c-erbB-2 expression was exclusively epithelial. An image analyser was used to quantitate variations in their expression during the mentrual cycle. EGF-R and c-erbB-2 expression on epithelial cells was stronger during the luteal phase than the follicular phase (p < 0.01 for EGF-R). The pattern of expression was also compared with that in 28 breast cancers and 7 fibroadenomas.     

c-erbb growth-factor-receptor proteins in ovarian tumours

Immunohistochemical expression of EGF-R, c-erbB-2 and c-erbB-3, members of the type-l family of receptor tyrosine kinases, were investigated in 67 primary ovarian-tumour samples (46 malignant, 8 borderline and 13 benign), and related to tumour clinicopathological features. The incidence of all 3 receptor proteins was highest in overtly malignant tumours. No significant correlations were observed between either EGF-R or c-erbB-3 and clinical parameters such as tumour stage, differentiation or extent of debulking surgery, but c-erbB-2 was significantly associated with several indicators of prognosis, including early stage and good/moderate differentiation in optimally debulked tumours. Multiple expression of c-erbB receptor proteins was also significantly higher in malignant tumours compared with borderline and benign tumours. Early-stage tumours were also more likely to express multiple c-erbB-receptor proteins than were late-stage tumours. Co-expression of EGF-R with c-erbB-2, and c-erbB-2 with c-erbB-3 was significantly greater in malignant tumours than in borderline or benign tumours, and within the malignant tumour group, positive associations were observed between EGF-R and c-erbB-3, also between c-erbB-2 and c-erbB-3. Because of the evidence of increased expression of individual c-erbB proteins as well as multiple expression of this family of growth-factor receptors in malignant ovarian tumours, we hypothesize that stimulation by the appropriate ligands may confer a selective advantage to cells expressing more than one receptor. Increased expression of c-erbB growth-factor receptors in malignancy may mediate increased propensity for tumour development. © 1995 Wiley-Liss, Inc.     

Inhibition of tumorigenicity in lung adenocarcinoma cells by c-erbB-2 antisense expression

The lung carcinoma cell line Calu3, which overexpresses the c-erbB-2 oncogene, was stably transfected with antisense (AS) cDNA constructs encompassing different regions of the c-erbB-2 gene. Transfected cells were analyzed for their tumorigenic properties in vitro and in nude mice. Two independent clones, AS F1 (low erbB-2 expressor) and AS B12 (high erbB-2 expressor), as well as the polyclonal Calu3/AS 5′, were selected for these analyses. In Calu3/AS 5′ transfected cells and in the AS F1 clone, c-erbB-2 RNA and protein levels were lower than those detected in the parental cell line and the AS B12 clone. Anchorage-independent growth and tumor take were also significantly reduced. Furthermore, cells derived from primary tumors of Calu3/AS 5′, AS F1 and AS B12 lost the AS c-erbB-2 DNA insert but retained the gene for G418 resistance. Our results suggest that a correlation between c-erbB-2 overexpression and tumorigenicity may exist in the Calu3 lung carcinoma cell line. Int. J. Cancer 72:631–636, 1997. © 1997 Wiley-Liss, Inc.     

Immunohistochemical detection of p53 and c-erbB-2 proteins: Prognostic significance in operable breast cancer

We examined the associations of p53 expression and/or c-erbB-2 expression with Ag-NOR counts and clinicopathologic variables in 111 breast cancer patients, and assessed whether expression of either p53 or c-erbB-2 would be useful prognostic indicators. There was no significant association between p⁵³ expression and c-erbB-2 expression, but p53 expression and c-erbB-2 expression, especially in combination, were shown to be significantly associated with Ag-NOR counts and axillary lymph node metastasis. Although p⁵³ expression and c-erbB-2 expression were significant prognostic factors by univariate analysis, they did not appear to be independent prognostic factors by multivariate analysis, in which nodal status was introduced using the Cox model. When nodal status was excluded from the model, however, concurrent p⁵³ and c-erbB-2 expression did have a significant prognostic value. Therefore, it was suggested that concurrent p⁵³ and c-erbB-2 expression provides valuable prognostic information for breast cancer patients in whom axillary lymph node dissection has not been performed.     

Down-regulation of riα subunit of camp-dependent protein kinase induces growth inhibition of human mammary epithelial cells transformed by c-ha-ras and c-erbb-2 proto-oncogenes

MCF- 10A is a spontaneously immortalized, non-transformed human mammary epithelial cell line. We have recently obtained MCF- 10A clones (MCF- 1OA HE cells) that are transformed following over-expression of both a human point-mutated c-Ha-ras and the c-erbB-2 proto-oncogenes. Two isoforms of the cAMP-dependent protein kinase (cAK) have been described in mammalian cells. Enhanced levels of type-I cAK (cAKI) are generally found in tumor cells. To determine whether inhibition of cAKl expression may interfere with ras and erbB-2 oncogene-induced transformation of human mammary epithelial cells, we have tested the effects of 2 agents that specifically down-regulate cAKI, such as 8-chloro-cAMP and an anti-sense oligodeoxynucleotide targeted against the R1α regulatory subunit of cAKl on MCF-10A HE cells. Treatment of MCF-10A HE cells with 8-chloro-cAMP induces a dose-dependent growth inhibition under both monolayer and soft-agar growth conditions, that is correlated with an accumulation of MCF-10A HE cells in G₀/G, phases of the cell cycle and a reduction of the number of cells in S phase. In contrast, 8-chloro-cAMP has no effect on MCF-10A cell growth. Furthermore, 8-chloro-cAMP treatment of MCF-10A HE cells induces a 4- to 6-fold reduction in p185erbB-2 expression and brings p21 ras expression to levels comparable to those found in MCF-10A cells. Treatment of MCF-10A HE cells with an Rlα anti-sense oligodeoxynucleotide determines a comparable inhibition of both anchorage-dependent and anchorage-independent cell growth. Our results suggest that cAKl may act as a mediator of ras and erbB-2 oncogene action in human breast cells and that interference with cAKl action provides a potential tool for inhibiting the growth-promoting effects of these oncogenes.     

A humanized Anti-c-erbB-2 monoclonal antibody for the treatment of breast cancer

The c-erbB-2 product is thought to be a unique and useful target for antibody therapy of cancers that overexpress the c-erbB-2 gene. Its overexpression is also speculated to be correlated with chemoresistance to doxorubicin. The in vitro and in vivo anti-tumor effects of a humanized antibody directed against the extracellular domain of the c-erbB-2 gene product, rhu4D5, were examined. Rhu4D5 had direct antiproliferative activity against the SK-BR-3 cell line which overexpresses c-erbB-2. The in vivo treatment, using rhu4D5, of SCID mice carrying xenografts of 4-1ST human gastric carcinoma, which overexpresses c-erbB-2, revealed that the recombinant protein had potent anti-tumor activity. Furthermore, the cytotoxic action of human peripheral blood mononuclear cells against the SK-BR-3 cell line was significantly augmented with the administration of rhu4D5, but not with mu4D5. These results indicate that rhu4D5 might be a more efficacious treatment than previously predicted by preclinical studies.     

No significant predictive value of c- erbB-2 or p53 expression regarding sensitivity to primary chemotherapy or radiotherapy in breast cancer

To document whether c-erbB-2 over-expression or p53 accumulation in tumour cells was predictive of response to chemo- or radiotherapy, we analyzed a population of patients with breast cancer assigned to neo-adjuvant therapy (median follow-up: 54 months). T2/T3-N0N1b-M0 tumours (329 cases) were treated either by FAC chemotherapy or by radiotherapy before surgery, and the clinical response was classified as complete or incomplete. Expression of c-erbB-2 and p53 was retrospectively evaluated by immunohistochemistry. Proliferation rate was assessed by means of MIB-1 antibody and by S-phase fraction. A complete response to chemotherapy was observed in 38/167 patients (23%). Complete response rate was 20% in c-erbB-2-negative tumours, and rose to 31% in tumours with c-erbB-2 over-expression, but this trend was not statistically significant. There was no correlation between p53 staining and response to treatment, whereas chemosensitivity was found correlated with histological grade and S-phase. A complete response to radiotherapy was observed in 64 of the 156 evaluable patients (41%). Complete response rate was 41% in c-erbB-2- or p53-negative tumours, 54% in tumours with c-erb-B-2 over-expression, and 44% in tumours with p53 accumulation. There was no correlation between response to radiotherapy and histological grade or proliferative rate. No prognostic value was found for c-erbB-2 or p53 expression, whereas the 5-year survival rate was 85% for patients presenting a tumour with a low proliferating index (MIB-1 < 10%), and 68% for patients presenting a tumour with a high proliferative index. In multivariate analysis, node status (RR = 2), MIB-1 immunostaining (RR = 2), and tumour size (RR = 1.8) were found to be associated with survival. These results indicate that c-erbB-2 or p53 expression is not significantly associated with tumour response to neo-adjuvant chemo/radiotherapy in our series of breast cancers. Int. J. Cancer (Pred. Oncol.) 79:27–33, 1998. © 1998 Wiley-Liss, Inc.     

Prognostic Significance of c-erbB-2 Expression in Invasive Ductal Carcinoma of the Breast

The expression of c-erbB-2 oncoprotein was studied in relationto the histological type of invasive ductal carcinoma. The expressionof c-erbB-2 was found in 26 (17.6%) of 148 cases, and was asignificant prognostic indicator in patients with lymph nodemetastasis, but not in those without. The patients were dividedinto a scirrhous group and a non-scirrhous group on the basisof histological type. There was no significant difference betweenthe two groups in age, clinical stage, lymph node status, estrogenreceptor status, operation method or c-erbB-2 expression. Theexpression of c-erbB-2 was a significant prognostic indicatorin the scirrhous group, irrespective of lymph node metastasis,but not in the non-scirrhous group. We conclude that the prognosticsignificance of c-erbB-2 expression differs among histologicaltypes of invasive ductal carcinoma, and that c-erbB-2 expressionis a prognostic indicator in patients with scirrhous carcinoma.     

Prognostic value of c-erbB-2 protein expression in human lung adenocarcinoma and squamous cell carcinoma

203 primary human lung tumours, of which 119 were adenocarcinoma and 84 were squamous cell carcinoma, were investigated immunohistochemically for the expression of c-erbB-2 protein. Positive staining was evident in 33 (28%) of adenocarcinomas and 2 (2%) of squamous cell carcinomas. In cases of adenocarcinoma, c-erbB-2 was present in 18% of those with stage I disease. In stage IIIA, stage IIIB and stage IV cases, c-erbB-2 was present in 39%, 50% and 60%, respectively (I vs. IIIA and I vs. IIIB: P < 0.05, I vs. IV: P < 0.01). The 5-year survival rates of c-erbB-2 positive patients and those who were negative were 30% and 52%, respectively, with a statistically significant difference (P < 0.01). These observations suggest that when the expression of c-erbB-2 correlates with invasiveness of the tumour, this correlation may serve as a prognostic indicator, particularly in cases of adenocarcinoma of the lung.     

The tyrosine kinase activity of the C-erbB-2 gene product (p185) is required for growth inhibition by anti-p185 antibodies but not for the cytotoxicity of an anti-p185-ricin-a chain immunotoxin

Our previous studies have demonstrated that 7 of 10 lgG antibodies against distinct epitopes on the extracellular domain of the c-erbB-2 gene product (p185) inhibit the anchorage-independent growth of SKBr3 human breast-cancer cells that overexpress this transmembrane tyrosine kinase growth-factor receptor. Two of 7 growth-inhibitory antibodies also block the binding and function of the gp30 and p75 c-erbB-2 ligands. In this report we have studied phosphorylation of p185 and different intracellular substrates after binding of antibodies that do or do not inhibit tumor-cell growth. A correlation has been found between antibodies that inhibit growth and the intensity of tyrosine phosphorylation of p185. At late intervals, serine phosphorylation of at least 3 intracellular substrates is increased preferentially by growth-inhibitory antibodies. To test the importance of p185 kinase activity more critically, NIH3T3 cells were transfected with an expression vector containing the full-length human c-erbB-2 gene (cell line 17313), c-erbB-2 with deletion of the kinase region from codons 751–979 (cell line 9309) or c-erbB-2 with deletion of most of the intracellular domain from codons 684–1255 (cell line 9310). Unconjugated antibodies inhibited anchorage-independent growth of 17313 cells as well as SKBr3 cells, but did not inhibit growth of either 9309 or 9310 cells. In contrast, the cytotoxic effect of anti-p185-ricin A chain (RTA) conjugates was comparable for 17313, 9309 and 9310. The tyrosine-kinase activity of p185 is required for growth inhibition mediated by unconjugated anti-p185 antibodies, but not for the cytotoxic activity of anti-p185-RTA immunotoxins.     

Inhibition of growth-factor-activated proliferation by anti-estrogens and effects on early gene expression of mcf-7 cells

Recently, it was reported that the anti-estrogen tamoxifen not only inhibits estradiol-stimulated growth of MCF-7 cells but also significantly reduces the proliferation rate of cells stimulated by growth factors. We have confirmed this finding and also shown that the new anti-estrogen droloxifene inhibits the proliferation of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I)-stimulated MCF-7 cells. The growth-factor-induced proliferation was inhibited in a dose-dependent manner by the anti-estrogens in the complete absence of estrogen and FCS. Of the anti-estrogens, droloxifene was considerably more potent than tamoxifen. Because the exprersion of the proto-oncogenes c-fos and c-myc has been considered a key event in development of the mitogenic response, we examined the effects of anti-estrogens on c-myc and c-fos gene expression. We included in these investigations the steroidal anti-estrogen ICI 164,384 because this compound has no or very little estrogenic activity. The studies revealed that all 3 antiestrogens transiently induced c-myc mRNA expression. However, the anti-estrogens inhibited estradiol-induced c-myc mRNA expression, although with different potencies. Pre-incubation of MCF-7 cells with droloxifene and tamoxifen resulted in elevated levels of growth-factor-induced c-myc mRNA expression. In contrast, the anti-estrogens did not induce c-fos mRNA or affect the expression of c-fos mRNA induced by growth factors. In conclusion, non-steroidal anti-estrogens inhibit growth-factor-stimulated proliferation of MCF-7 cells without inhibitinggrowth-factor-induced c-myc or c-fos mRNA expression.     

Amplification and differential expression of members of theerbB-gene family in human glioblastoma

Summary The objective of the present study was to determine the frequency of amplifications of three different members of theerbB gene family in human glioblastoma multiforme (GBM). We investigated 47 glial tumors (37 GBM WHO grade IV, 5 anaplastic astrocytomas WHO III and 5 astrocytomas WHO II) by Southern and Western analysis, and immunocytochemistry. Gene amplification oferbB genes in human malignant gliomas was restricted to the EGF receptor (EGFR) gene,erbB-1. We found amplification of the EGFR gene in 49% (18/37) of GBM but not in the astrocytomas WHO II/III. TheerbB-2 anderbB-3 genes showed no amplification in the tumor specimens investigated in this study. At the protein level we found overexpression of the EGF receptor in 86% (32/37) by Western analysis and in 92% (34/37) by immunocytochemistry. Expression of the ERBB2 protein was present in 54% (20/37) but immunoreactivity was much weaker than for EGF receptor and in most cases barely detectable by Western analysis and immunocytochemistry. The ERBB3 protein was not expressed in the glial tumors investigated in this study. Of the threeerbB genes only gene amplification and overexpression of the EGF receptor seems to have an impact on tumor progression of human gliomas. Our data from immunohistochemistry indicate that ERBB2 expression in GBM is closely correlated with EGF receptor levels and is therefore not useful as an independent prognostic parameter.     

The role of amphiregulin in breast cancer

Summary Amphiregulin (AR) is an epidermal growth factor (EGF)-related peptide that operates exclusively through the EGF receptor and that can bind to heparin. AR also possesses nuclear localization sequences in the extended NH₂-terminal region suggesting an additional intracellular site of action. AR mRNA and protein expression have been detected in primary human mammary epithelial cell strains, nontransformed human mammary epithelial cell lines, several human breast cancer cell lines, and primary human breast carcinomas. The frequency and levels of AR protein expression are generally higher in invasive breast carcinomas than in ductal carcinomasin situ or in normal, noninvolved mammary epithelium. In addition, AR can function as an autocrine and/or juxtacrine growth factor in human mammary epithelial cells that have been transformed by an activated c-Ha-ras proto-oncogene or by overexpression of c-erb B-2. AR expression is also enhanced by mammotrophic hormones such as estrogens and other growth factors such as EGF.Presented by David S. Salomon at the 16th Annual San Antonio Breast Cancer Symposium, San Antonio TX, USA, November 4, 1993; Minisymposium on Molecular Genetics in Breast Cancer.     

Reduced expression of nm23-H1, but not of nm23-H2, is concordant with the frequency of lymph-node metastasis of human breast cancer

The nm23 gene is a potential metastasis-suppressor gene originally identified in a murine melanoma line. Several investigators have reported the probable inverse association of nm23 expression with disease prognosis and/or metastasis. Since there are now 2 known isotypes of human nm23, namely nm23-H1 and -H2, we immunohistochemically examined expression of these isotypes in human breast-cancer tissues using monoclonal antibodies (MAbs) specific for each isotype protein. We also analyzed expression of c-erbB-2 in the same collection of cancer tissues, in order to examine the significance of nm23 expression in comparison with c-erbB-2 expression. Of 130 tumors from breast-cancer patients, 73 (56%) and 69 (53%) positively expressed nm23-H1 and -H2 respectively. Expression of c-erbB-2 was positive in 36 (28%). Expression of nm23-H1, but not nm23-H2, was inversely associated with lymph-node metastasis (p < 0.01). Expression of c-erbB-2 was associated with Tnm stage, tumor size and lymph-node metastasis (p < 0.01, p < 0.05 and p < 0.05 respectively). Overall survival was better (p = 0.014) in patients in whom expression of nm23-H1 was positive than in those in whom it was negative. In multivariate analyses using a Cox's proportional-hazards regression model with 9 variables, nm23-H1 showed the fourth greatest contribution to patient survival following lymph-node metastasis, Tnm stage and menopausal status. No significant contribution was shown for c-erbB-2 expression. nm23-H1, but not nm23-H2, may perform a role in disease prognosis in addition to its participation in cancer metastasis. It may have value for predicting long-term survival of human breast-cancer patients. © 1993 Wiley-Liss, Inc.