HER-2/neu immunoreactivity in invasive mammary carcinomas: a comparative study using monoclonal and polyclonal antibodies including the HercepTestTM

Abstract

Introduction: HER-2/neu overexpression has been tested using immunohistochemistry as a reliable and cost-effective method to select patients with invasive mammary carcinomas (IMC) for trastuzumab treatment, but there is no consensus regarding the best antibody to be used. The aim of the present study was to test five different antibodies for determining the status of HER-2/neu overexpression in IMC. Material and methods: Sixty-six formalin-fixed, paraffin-embedded IMC were investigated by immunohistochemistry, using two polyclonal antibodies, HercepTest TM (Dako) and A0485 (Dako), and three monoclonal antibodies, the clone CB11, from both Novocastra Laboratories and from Biogenex, and the clone 4D5 (Genentech). All immunostainings were scored according to the guidelines for the HercepTest TM. Results: The A0485 was positive in 25 cases (37.9%). The HercepTest TM was positive in 14/66 cases (21.2%). Both CB11 antibodies yielded a positive reaction in the same nine patients (13.6%). The 4D5 was positive in only 4/66 cases (6.1%). All positive cases for CB11 or 4D5 were HercepTest TM positive. All cases positive for HercepTest TM were positive for A0485. Most of the HercepTest TM and A0485 2+ cases were negative when using the other antibodies. Discussion: There was a higher number of cases presenting HER-2/neu positivity with the

Predictive factors of breast cancer evaluated by immunohistochemistry

“…The SP3, HercepTest and A0485 identified all cases with HER2 amplification using the current guidelines for Her2 assessment. However, the SP3 and the polyclonal antibodies, including the HercepTest, detected more false-positive cases than mouse monoclonal antibodies CB11 and 4D5 (20,38,39) .…”

“…However the HercepTest, CB11 and 4D5 show higher "specificity" than SP3 for the identification of HER2 gene amplification (20,38) . Ricardo et al (43) also compared SP3 with CB11, having CISH as the gold standard in breast cancer tissue microarrays, however they showed a high specificity and a moderate sensitivity of SP3 (43) .…”

“…The 10% level for positivity, independent on the staining intensity, has been accepted and has been the most used cut off for ER and PR (15,17,48) . However, further studies showed that patients whose tumors expressing ER in more than 1% of neoplastic cells with moderate or strong intensity presented response to anti-estrogen therapy (1,20) . The 2005 Saint Gallen Consensus Conference recommended the cut off proposed by Allred (Table) in which a total score of more than 3 is considered positive (18) .…”

“…We also compared the immunohistochemical protein overexpression of protein with the gene amplification using CISH (20,38,39) . The antibody SP3 displayed an optimal "sensitivity", similar to that obtained with anti-Her2 polyclonal antibodies (i.e.…”

A comparison between the novel rabbit monoclonal antibodies (SP1 and B644) and mouse antibodies for evaluating estrogen receptor in breast tumors

“…As a result, there is not yet a universally accepted standard (16,23) . As with any laboratory method, technical details have a great effect on the final result (11,20,21) .…”