Tissue microarray based identification of molecular cancer therapy targets in clinical routine

Abstract

For this dissertation we collected all cancerous tissue samples which were sent to the Institute of Pathology of the Universitätsklinikum Hamburg-Eppendorf between April and July 2010. All samples of every month were brought to TMA format, resulting in 1217 cases in four separate DTMAs. Those four TMAs were immunostained for Her2/neu and cKIT overexpression, using HercepTest and the Dako Kit for cKIT. They were also fished for Her2/neu and EGFR-gene amplification, using the PathVysion- and Vysis-kits.

We substracted all the positive cases which are routinely tested for the according markers and were left with 11 Her2/neu positive cases. We validated eight cases in whole sections and found out, that all eight showed homogeneous Her2/neu overexpression. We found 22 cases with EGFR amplification, of which eight were subjected to the whole section validation. Five of those showed homogeneous amplification in all tested slides.

In case of cKIT we found 33 cases with strong positivity. We chose seven examples and performed a mutational analysis via PCR. All cases did not show an activating mutations in one of the tested exons.

We reviewed the literature and compared how often the amplification was found in studies conducted in the past. We could not find another study with a similar setting, continuously testing all incoming tissue samples. Therefore, the results of our comparisons with studies focussing on one tumor-type produced some matching figures and sometimes major differences.

Testing all incoming cancerous tissue samples in a TMA format costs 22,73 Euro per case and results in the discovery of 1\\\\% of positive cases for Her2/neu and EGFR, which would otherwise not have been found. These cases might be eligible for the targeted treatment.

We postulate that the DTMA-method is cost-effective and will gain even more importance when there have been more studies widening the indications for those therapies. Furthermore this method can easily be expanded to include more staining-kits as soon as they are established and a suitable drug has been introduced.