Quantification of ERBB2 protein expression in breast cancer: three levels of expression defined by their clinico-pathological correlations.
ABSTRACT Activation of the ERBB2 oncogene seems to be an early event in breast cancer progression and prevalent in in situ carcinomas. However, its prognosis value, albeit recognized for node-positive patients, remains controversial for those without apparent nodal involvement. One possible reason for this problem is likely to be the difficulty of defining threshold levels for ERBB2 protein overexpression. ERBB2 protein expression was therefore analyzed in primary invasive breast tumors. Quantification of the gene product by a commercial ELISA test was compared to results obtained by immunohistochemistry and western blotting, as well as to gene amplification status determined by Southern blotting. Correlations between results obtained by the different techniques were highly significant (P value < 10(-6)). Nevertheless, ELISA permitted us to determine three levels of protein expression corresponding to distinct tumor subsets. 1) Tumors with p185/ERBB2 expression levels exceeding 10 U/microgram exhibited in most cases amplification of the gene (83% of cases), DNA aneuploidy (81%) and absence of estrogen receptor (ER) (44%). Such high levels of protein expression were exclusively observed in invasive ductal carcinomas and were prevalent in those showing a significant in situ component. 2) "Intermediate" levels of expression (3-10 U/micrograms) were rarely observed in tumors exhibiting gene amplification (9%), but were preferentially found in cancers of more favorable prognosis (only 49% were aneuploid and 9% estrogen receptor negative). 3) Levels of p185/ERBB2 below 3 U/micrograms were detected in benign mastopathies and, thus, carcinomas presenting such levels were scored ERBB2 negative. Interestingly, invasive lobular carcinomas were rarely ERBB2 positive, and if so, only at intermediate levels. Moreover, our data show a complex interrelationship between p185/ERBB2 expression and ER levels. Indeed, tumors with more than 10 U/micrograms of p185 were prevalently ER, whereas those with p185 ranging from 3 to 10 U presented elevated levels of ER.
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ABSTRACT: Members of the c-erbB family have been implicated in poor prognosis in breast cancer. Given the propensity for heterodimerisation within the erbB family, the pattern of co-expression of these receptors is likely to be as functionally important as aberrant expression of any given receptor alone. Therefore, the patterns of expression of the receptors, epidermal growth factor receptor (EGF-R), c-erbB-2, c-erbB-3, c-erbB-4, and one of the erbB ligands, heregulin (HRG), were examined in normal and malignant breast cell lines and compared with expression of oestrogen receptor (ER), a classical indicator of good prognosis. There was an inverse correlation between ER and EGF-R mRNA levels, as previously described, but no correlation between either of these receptors and c-erbB-2. c-erbB-3 expression was positively correlated with ER. In contrast, HRG expression was inversely related to ER. Expression of antisense-ER resulted in increased EGF-R mRNA, demonstrating a functional link between the expression of these 2 genes, however, there was no significant change in c-erbB-2 or c-erbB-3 mRNA, suggesting that ER is not directly involved in control of expression of these genes. A comparison of individual erbB receptors and HRG revealed that the majority of lines expressing increased levels of c-erbB-2 also expressed elevated levels of c-erbB-3 mRNA, and none of the cell lines that expressed both c-erbB-2 and either c-erbB-3 or c-erbB-4 expressed the ligand HRG. In summary, the levels of expression of c-erbB-1, -2, -3, and -4 varied in this series of breast cell lines, and the pattern of expression and the relationship of each growth factor receptor to the expression of ER was quite distinct. The lack of expression of HRG in cell lines that express receptors may be indicative of paracrine interactions between erbB ligands and their cognate receptors and may suggest that the ligand and receptors are expressed in different subtypes of breast epithelial cells from which the cell lines are derived.International Journal of Cancer 09/2000; 87(4):487-98. · 6.20 Impact Factor
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ABSTRACT: The c-erbB-2 proto-oncogene encodes a transmembrane protein tyrosine kinase receptor of 185 kDa (p185) and has been associated with several types of human cancers. In human breast cancer, overexpression of p185 occurs in 15-30% of cases, correlates with poor prognostic factors and characterizes breast cancers with a more aggressive behavior. Overexpression of p185 is usually associated with c-erbB-2 amplification, though it may occur independently and thus define subpopulations of breast cancers which might be of clinical interest. p185 expression is usually detected by immunohistochemistry (IHC) and few studies have been carried out to evaluate the p185 content of breast cancers with an ELISA technique. In this context, we showed, in 106 breast cancer samples, that p185 was expressed at high levels in 13.2%, intermediate levels in 55.7% and negative ones in 31.1% of cases. All p185 positive samples showed a c-erbB-2 oncogene amplification while none of the p185 negative samples and only 4% of p185 imtermediate samples had an amplification of c-erbB-2. p185 expression is significantly correlated with the negativity of estrogen and progestrone receptors, with high levels of cathepsin D and in some conditions with axillary nodal involvement. Thus, using the p185 ELISA assay, the c-erbB-2 status of breast cancers can be defined and moreover a subset can be discriminated which is characterized by intermediate levels of p185 and absence of c-erbB-2 amplification. The quantitative approach towards p185 in breast cancers affords the possibility of identifying more appropriately patients with high or low risk and thus permits adaptation of therapeutic regimens.Breast Cancer Research and Treatment 10/2000; 63(2):163-9. · 4.47 Impact Factor
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ABSTRACT: The concentration of c-erbB-2 oncogene-encoded protein (p185neu) in fresh tumour samples obtained at the time of surgery from 94 non-small-cell lung cancer patients (NSCLC) was determined by an enzyme immunoassay. The relative prognostic importance was estimated, and the influence of other predictors was assessed by means of a Cox's proportional regression model. Median concentration of p185 in tumour tissues was 206 U mg(-1) (range 21-1050 U mg(-1)). p185 level did not differ significantly among subgroups defined by TNM classification, histological type, sex and age. Categorization of patients by p185 level, with 206 U mg(-1) and 343 U mg(-1) taken as cut-off values (corresponding to the 50th and 80th percentiles of the frequency distribution), showed that the recurrence rate, cumulative disease-free likelihood at the 36-month follow-up and median time from surgery to the diagnosis of recurrence worsened progressively as the level of p185 increased. Multivariate analysis confirmed the independent prognostic value of p185 level. Risk of recurrence increased by 1.304 for every increase of 100 units in p185 concentration (95% CI 1.141-1.490) (P<0.001). These findings encourage the inclusion of p185 concentration assay in a future predictive multifactorial prognostic index in NSCLC.British Journal of Cancer 01/1997; 75(5):684-9. · 5.08 Impact Factor