Determination of c-erbB-2 protein in primary breast cancer tissue extract using an enzyme immunoassay

C-erbB-2 Expression in Primary Breast Cancer

c-erbB-2 is an oncoprotein which is overexpressed in up to 40% of primary breast cancers. c-erbB-2 overexpression is a bad prognostic factor in patients with lymph node-positive disease. Unfortunately, there has been no agreement to date on whether c-erbB-2 overexpression is of prognostic significance in patients with lymph node-negative disease. c-erbB-2 overexpression is correlated with the absence of estrogen receptor expression in a number of publications. Correlation between c-erbB-2 overexpression and hormone sensitivity in the clinical setting is less well established and is the focus of ongoing studies. Both preclinical and clinical studies support an association between c-erbB-2 receptor overexpression and resistance to alkylating agents. In contrast, the data for c-erbB-2 and anthracyclines should be viewed in a slightly different manner. Anthracyclines appear to have a greater therapeutic effect in c-erbB-2-positive disease which may be dose sensitive. In c-erbB-2-negative disease not only is the therapeutic effect reduced but there does not appear to be any improved response to higher doses of anthracyclines. The data for c-erbB-2 and the taxanes is still not clear enough to provide any definite conclusions. If there is a correlation it would at present appear to be between paclitaxel and response rates, but this needs to be confirmed in larger studies. Few studies have looked at changes in c-erbB-2 on therapy. Those that have seem to show no significant change on either tamoxifen or chemotherapy.

HER2/HER3 heterodimers and p21 expression are capable of predicting adjuvant trastuzumab response in HER2+ breast cancer

Human epidermal growth factor receptor 2 (HER2) plays an important role in breast cancer progression and provides predictive information for response to targeted therapy including trastuzumab although this is limited. Downstream pathways, such as PI3K/Akt, are associated with HER2/HER3 heterodimerization promoting survival and proliferation amongst cancer cells. Thus, patient outcome and trastuzumab therapy effectiveness might be further characterised by HER2/HER3 dimerisation and its signalling pathways. HER2/HER3 dimerisation status was assessed, using chromogenic in situ Proximity Ligation Assay, in two breast cancer series: early stage primary breast cancer, including 224 HER2+ patients that were not submitted to trastuzumab, and HER2+ breast cancer where patients were treated with adjuvant trastuzumab (n = 143). Levels of biomarkers including PI3K, pAKT, ER, PgR, HER3, BCL2, p53, PTEN and p21 were measured using immunohistochemistry. Levels of HER2/HER3 heterodimers were compared with biomarker expression and patient outcome. An association between high levels of HER2/HER3 dimerisation and absence of hormone receptors, ER and PgR, was observed. We further show for the first time the presence of HER2/HER3 heterodimers and the loss of p21 expression in HER2+ breast cancer predicts a significantly poorer outcome when submitted to adjuvant trastuzumab. Breast cancer patients that reveal high levels of HER2/HER3 dimerisation and loss of p21 are associated with poor survival prognosis in patients with HER2+ breast cancer treated with adjuvant trastuzumab. Further quantification analysis of HER dimer/ligand complexes and downstream signalling pathways will begin to unravel the complex associations with patient outcome and its relationship with sensitivity to targeted treatment.

A mechanism of drug resistance to tamoxifen in breast cancer

Drug resistance to tamoxifen (Tam) is a significant clinical problem but the mechanism through which this occurs remains elusive. We have developed a number of xenograft models of Tam-stimulated growth that model breast cancer progression using estrogen receptor positive MCF-7 or T47D breast cancer cells. When estrogen-stimulated T47D:E2 tumors are treated long term with Tam, Tam-stimulated tumors develop (T47D:Tam) that are stimulated by both estrogen and Tam. When HER-2/neu status is determined, it is clear that the T47D:Tam tumors express significantly higher levels of HER-2/neu protein by immunohistochemistry and mRNA as measured by real-time RT-PCR. The T47D:Tam tumors also express higher levels of estrogen receptor and progesterone receptor protein than their estrogen-stimulated T47D:E2 counterparts. We compared out results to the MCF-7 model of Tam-stimulated growth. The MCF-7:Tam ST (estrogen- and Tam-stimulated) and MCF-7:Tam LT (estrogen-inhibited, Tam-stimulated) were bilaterally transplanted to account for any mouse to mouse variation and characteristic growth patterns were observed. TUNEL staining was performed on MCF-7:Tam LT treated with either estrogen or Tam and it was concluded that estrogen-inhibited tumor growth was a result of increased apoptosis. Three phases of tumor progression are described that involve increases in HER-2/neu expression, de-regulation of estrogen receptor expression and increases in apoptosis which in concert determine the phenotype of drug resistance to Tam.

Prognostic value of HER-2/neu and p53 expression in node-positive breast cancer. HER-2/neu effect on adjuvant tamoxifen treatment

HER-2/neu and p53 expression, conventional clinical and pathologic prognostic factors, were evaluated in a retrospective series of 283 node-positive breast cancer patients. Overexpression was determined by immunohistochemistry in formalin-fixed paraffin-embedded tissue blocks. Twenty one percent were HER-2/neu positive and 40% p53 positive. HER-2/neu expression was related to axillary lymph node metastasis (P=0.014), inflammatory infiltrates (P=0.004), and the absence of oestrogen (ER) (P=0.0026) and progesterone (P=0.01) receptors (PR). p53 expression was related to lymph node involvement (P=0.03), necrosis (P=0.036), absence of ER (P=0.028) and PR (P=0.065). p53 was not associated with outcome. HER-2/neu was an unfavourable prognostic factor for disease-free (DFS) (P=0.05) and overall survival (OS) (P=0.02) in univariate analysis. Multivariate analysis showed that the number of involved axillary nodes (P<0.00001), age (P=0.004), grade (P=0.04), and PR (P=0.04) were independent predictors for OS. ER-positive patients treated with adjuvant tamoxifen had shorter DFS and OS when they were HER-2/neu positive.

Role of HER2 gene overexpression in breast carcinoma

The HER2 proto-oncogene encodes a transmembrane glycoprotein of 185 kDa (p185(HER2)) with intrinsic tyrosine kinase activity. Amplification of the HER2 gene and overexpression of its product induce cell transformation. Numerous studies have demonstrated the prognostic relevance of p185(HER2), which is overexpressed in 10% to 40% of human breast tumors. Recent data suggest that p185(HER2) is a ligand orphan receptor that amplifies the signal provided by other receptors of the HER family by heterodimerizing with them. Ligand-dependent activation of HER1, HER3, and HER4 by EGF or heregulin results in heterodimerization and, thereby, HER2 activation. HER2 overexpression is associated with breast cancer patient responsiveness to doxorubicin, to cyclophosphamide, methotrexate, and fluorouracil (CMF), and to paclitaxel, whereas tamoxifen was found to be ineffective and even detrimental in patients with HER2-positive tumors. In vitro analyses have shown that the role of HER2 overexpression in determining the sensitivity of cancer cells to drugs is complex, and molecules involved in its signaling pathway are probably the actual protagonists of the sensitivity to drugs. The association of HER2 overexpression with human tumors, its extracellular accessibility, as well as its involvement in tumor aggressiveness are all factors that make this receptor an appropriate target for tumor-specific therapies. A number of approaches are being investigated as possible therapeutic strategies that target HER2: (1) growth inhibitory antibodies, which can be used alone or in combination with standard chemotherapeutics; (2) tyrosine kinase inhibitors (TKI), which have been developed in an effort to block receptor activity because phosphorylation is the key event leading to activation and initiation of the signaling pathway; and (3) active immunotherapy, because the HER2 oncoprotein is immunogenic in some breast carcinoma patients.

c-erbB-2 protein overexpression and p53 immunoreaction in primary and recurrent breast cancer tissues

BACKGROUND AND OBJECTIVES

We investigated whether expression levels of c-erbB-2 and p53 proteins in breast cancer tissues differ in primary and metastatic lesions.

METHODS

Immunohistochemical staining or sandwich enzyme immunoassay was used to determine expression levels of c-erbB-2 and p53 proteins in 42 breast cancer samples from 21 patients. Estrogen (ER) and progesterone receptors (PgR) were also measured by enzyme immunoassay in each case. All patients had undergone radical surgery for primary tumors and surgical resection of asynchronous metastatic lesions. Thirteen patients (62%) were premenopausal and 14 (67%) received postoperative adjuvant therapies. Median disease-free survival time was 26 months (range, 5-104). The resected metastatic lesions included 1 in the liver, 3 in the lung, and 3 in the supraclavicular lymph nodes. The remaining 14 were local skin lesions.

RESULTS

There was no difference in the positivity rate of c-erbB-2 (38%: 8/21) and p53 (39%: 7/18) expression between the primary tumors and the recurrent lesions. In addition, no discordant c-erbB-2 or p53 expression was observed between the primary tumors and their respective metastatic lesions. Positivity rates for ER and PgR were 50% (10/20) and 60% (12/20) for the primary tumors, but only 25% (5/20) and 30% (6/20) for the recurrent lesions, respectively (P = 0. 19 for ER and P = 0.11 for PgR).

CONCLUSIONS

c-erbB-2 and p53 expression levels in breast cancer cells were almost unchanged as the disease progressed and/or in response to adjuvant therapies, regardless of the hormone receptor status.

Axillary node metastasis from T1N0M0 breast cancer: possible avoidance of dissection in a subgroup

BACKGROUND

Axillary lymph node dissection is now no longer considered to be the standard treatment in all patients with invasive breast cancer. We have attempted to identify a sub-group of patients with invasive breast carcinoma who may not need to undergo axillary lymph node dissection.

METHODS

Patients (n = 823) with T1 N0M0 invasive breast cancer treated at our hospital between 1970 and 1994 were studied. We investigated the relationship between positive axillary lymph nodes and the following clinico-pathological factors: patient age, menopausal status, contralateral breast cancer (synchronous or asynchronous), tumor location, tumor size (T:cm), histopathology, histological grade, presence or absence of malignant microcalcification or spiculation on mammography and estrogen receptor status.

RESULTS

The incidence of axillary lymph node metastases in patients with T1N0M0 invasive breast cancer was 25% (208/823). The node-negative group was significantly older than the node-positive group. Premenopausal patients had a higher rate of lymph node metastases although this was not significant. The frequency of nodal metastases when related to the tumor size was as follows: T< or =1.0 cm, 17%; T< or =1.5 cm, 25%; T< or =2.0 cm, 29%. Mammography revealed that patients with malignant calcification or spiculation had a significantly higher rate of nodal metastases than those without these findings. Certain tumor types (medullary, mucinous and tubular carcinomas) had lower positive rates for lymph node involvement. With regard to the histological grade, lymph node positivity increased significantly with high-grade tumors. No correlation was observed between any other factors and the presence or absence of lymph node metastases.

CONCLUSIONS

It may be possible to avoid axillary lymph node dissection in postmenopausal patients (50 years or older) where the histological type is favorable when the tumor diameter is < or =1.0 cm and when microcalcification or spiculation is absent on mammography.

Quantitative determination of c-erbB-2 in human breast tumours: potential prognostic significance of low values

The purpose of this prospective multicentric study was to quantify the c-erbB-2 protein and investigate its relationship with DNA amplification and with various prognostic parameters of breast cancer. A total of 1062 primary operable human breast tumours were collected from six French anticancer centres. The c-erbB-2 protein was measured using an enzymoimmunoassay using two monoclonal antibodies directed against the extracellular domain of the protein. The results were expressed in arbitrary units/mg membrane protein (AU) after adjustment for the anticancer centre. A significant association was found between the dosage of the protein and DNA amplification (P = 0.0001). A value of 200 AU was found to maximise sensibility and specificity and was chosen as a cut-off for over-expression. Significant associations were found between c-erbB-2 values and oestrogen receptor (ER) (P = 0.01), progesterone receptor (PgR) (P = 0.0001) and histological grading (P = 0.01). The extreme high values (above the mean plus one standard deviation, S.D.) were significantly more numerous in ER- (P = 10(-16)), PgR- (P = 10(-14)) and grade III (P = 10(-8)) tumours. The extreme low values (below the mean minus one S.D.) were significantly more numerous in ER- (P = 10(-9)) and PgR- (P = 0.02) tumours. This prospective study confirms that high c-erbB-2 protein values are linked to poor prognostic factors and shows for the first time that low values are also linked to hormone receptor negative tumours, suggesting that these low values might also have a negative prognostic significance.

Determination of cytosol c-erbB-2 protein in breast cancer by sandwich enzyme immunoassay

We determined cytosol c-erbB-2 protein levels using a sandwich enzyme immunoassay in benign breast disease and primary and recurrent breast cancer and analyzed the relationship between c-erbB-2 protein levels and clinicopathological factors. Overexpression of c-erbB-2 protein, the cut-off value being set at 18 ng/mg protein, was observed in 26 of the 139 cases of stages I-IIIB breast cancer (18.7%), four of the 12 cases of stage IV breast cancer (33.3%) and seven of the 13 recurrent breast cancer cases (53.8%). The levels of c-erbB-2 protein were significantly different between the stages. Overexpression of c-erbB-2 protein in stages I-IIIB breast cancer was associated with histological grade and serum CEA level, but not with other clinicopathological factors. In addition, there was an inverse correlation in the group of stages I-III plus IV breast cancer between c-erbB-2 protein expression and estrogen receptor status. Overexpression of c-erbB-2 protein can be easily determined in the cytosol fraction together with hormonal receptor by this method. The prognostic importance will be evaluated in ongoing adjuvant trials for operable breast cancer patients.