Detection of signal transduction molecular targets in gastrointestinal tumours

Detection of molecular genetic alterations is a crucial requirement for personalized treatment approaches.

Aims: Establishment of parallel morphological methods to detect expression of signal transduction (ST) molecular targets of the EGF receptor family for personalized therapy.

Materials and methods: 50 rectum or sigma adenocarcinomas were stained by immuno-histochemistry (IHC) to evaluate the relationship between expression of EGFR molecule members and 5 year survival. Erb family was taken as possible therapeutic target. We examined the expression of EGFR and HER-2 molecules in gastrointestinal and breast carcinomas in formalin fixed, paraffin embedded and in frozen sections. We used IHC with peroxidase-DAB or fluorescent labeling and fluorescent in situ hybridization (FISH) methods.

Results: In formalin fixed samples, neither EGFR nor HER-2 staining was detected. On the other hand, in frozen specimen both molecules were found in 86% of the cases. The intact tissues showed equal or increased EGFR and HER-2 expression in comparison to the whole tumor except one specimen. In that case, EGFR expression was extremely high – similar to that in xenografted A431 cells – suggesting EGFR gene-amplification. Parallel evaluation of HER-2 protein expression by IHC and gene amplification by FISH on formalin sections, negative and strong positive IHC staining gave precise prediction of the presence or absence of HER-2 gene amplification as confirmed by FISH (100% correlation). However, in borderline cases, performance of IHC was poor.

Conclusion: In our hands, frozen sections are required to determine tissue expression of the erb-family. FISH is required to detect HER2 gene amplification in borderline cases.