P1-07-14: Quantum Dot-Labelled Antibodies To Assess HER2 Expression in Breast Cancer.

Abstract

Abstract Background: The Human Epidermal Growth Factor Receptor 2 (HER2) is overexpressed in 18–20% of breast cancers. Herceptin is an effective drug for the treatment of breast cancers expressing high levels of HER2. It is well known that there is a correlation between levels of HER2 expression and response to Herceptin. However a proportion of patients selected for Herceptin treatment do not respond to the drug. The accuracy of the assessment of HER2 levels in breast cancer is therefore important to predict patients’ response to Herceptin therapy. The current techniques in clinical use for the assessment of HER2 are immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH); however both IHC and FISH have several limitations which may result in patient misclassification. A more accurate technique, which can quantify HER2 levels more precisely, could help to improve clinical diagnosis, prediction of prognosis and allow more accurate select individual patients for particular drug therapies. Materials and Methods: We employed QDs labelled antibodies, laser scanning confocal microscopy and image segmentation techniques to quantify HER2 expression in cases of formalin fixed paraffin embedded breast cancers. Quantum dots (QDs) are a new class of fluorochromes made of semiconductor nanocrystal which have several useful properties for quantitative image analysis. In order to validate the system we used a breast cancer HER2−IHC control tissue array with negative, low, moderate and strong expressing cases, and a tissue microarray containing 60 samples of formalin fixed paraffin embedded breast cancer sections, previously examined by IHC and scored semiquantitatively (0-3+). We then applied this system to quantify HER2 expression a tissue microarray containing 150 primary breast cancers scored as 3+ by IHC from patients treated with Herceptin. Results: We first demonstrated that the QD system could reliably detect HER2 expression in IHC 3+ cases. A comparison of immunofluorescent staining with conventional immunohistochemistry showed that QDs give more linear and scalable measurements of receptor levels. We also quantified HER2 within a set of 150 breast cancers scored as 3+ by IHC, and we found that HER2 is expressed at very different levels, ranging over fifty fold between individual (IHC3+) cases. We currently are evaluating the correlation between HER2 receptor levels, measured by QDs, and patient's response to Herceptin. Conclusion: QDs and image analysis can produce a more precise measurement of HER2 levels of expression than IHC. This should help to improve clinical diagnosis, prognosis, identify specific treatments for individual patients and reduce costs associated with Herceptin treatment. This technology may be applied to study other members of the EGF family in breast cancers or more widely as a quantitative measurement of biomarkers in tumours. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-07-14.