Extending Her-2/neu assessment using a larger spectrum of cytogenetic probes and monoclonal antibodies

Breast carcinoma is a major cause of cancer mortality in women. In an estimated 25 to 30 % of breast tumors there are amplifications/overexpression of the Her-2/neu (c-erbB-2) gene and these changes are markers of poor prognosis. For these patients selective and genetically targeted treatments are currently being designed using the humanized monoclonal antibody, transtuzumab (Herceptin). To date, immunohistochemistry (IHC) is the most used method for Her-2/neu assessment and IHC positive cases are verified by fluorescence in situ hybridization (FISH). It is necessary to optimise the quality of treatment for Herceptin to be effective. To compare the results using different agents, we carried out sample treatment using several polyclonal antibodies designed by the company Exbio in conjunction with our laboratory. The results were compared with the immunohis-tochemical findings for antibodies commonly used in Her-2/ neu diagnostics (HercepTect; DakoCytomation). In the same way we proceeded with the FISH assay using the probe, made by labeling plasmid vs. commercial probe (PathVysion Vysis). The three newly designed monoclonal antibodies produced by the Exbio company showed the same results as the HercepTest, immunohistochemistry detection system of Dako Cytomation. The sample of 524 patients was assessed by both plasmid and commercial probes. A high correspondence was found in the assessment of amplification of the Her-2/neu gene (divergence in 2.6 % of samples; p<0.001). Based on comparison of different probes and antibodies it is concluded that for Her-2/neu treatment, it is possible to use diverse detection systems but it is necessary to confirm their reliability with commercially verified systems.

Acknowledgement: The project was supported by grants MSM6198959216, LC07017 and grants of International Grant Agency of Ministry of Health care in CR NR/9076 and Ministry of industry and Commerce Department MPO 56110041. Special thanks go to all cooperating departments, and health insurance companies.