HER receptor expression and signalling pathways in formalin-fixed breast cancer tissues

Current concepts for cancer treatments are summarized as „personalized medicine“ and are most often directed against growth factor regulators. Typically, these factors are organized in complex networks with multiple regulations at many nodes. Identification of patients who will most likely benefit from these targeted treatments is the current challenge of medical research. Comprehensive molecular characterization of the diseased tissue plays a key role.
Pathologists look into the microscope and come up with the diagnosis that cancer is either present or absent. For this histopathological diagnosis the tissue has to be conserved (“fixed”) and embedded in a paraffin wax block for further processing. Molecular analysis of these fixed tissue samples is more difficult compared to studies with fresh or frozen material, particularly if proteins are to be analysed.
The Innovation Alliance (IA) “Markers for breast cancer” succeeded in the isolation of intact proteins from fixed clinical tissues using a special technique. Furthermore, reverse phase protein arrays (RPPA) were applied for functional signaling profiling of tumor tissues. Thus, this IA significantly contributed to technical improvements for personalized medicine. The commercialization of the technology was put forward by the industrial partner of the project.
In subproject 2 the focus of the research was on growth factor signaling in breast cancer. Proteins that are clinically important for treatment decisions, e.g. HER2, estrogen receptor, and progesterone receptor, were reliably quantitated in very tiny biopsies derived from breast cancer patients. Using the quantitative, highly sensitive RPPA technology, the most important result of this IA was the identification of a subgroup of immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) HER2-negative breast cancers with levels of activated/phosphorylated HER2 (Y1248) comparable with IHC and FISH HER2-positive tumors that was accompanied by coactivation of HER2-binding partners as well as downstream pathway targets. This group of patients was not identified by current clinically approved tests for HER2 and is currently excluded from anti-HER2 treatment.
Currently, locally HER2-positive but centrally HER2-negative breast cancers in Germany are screened for the presence of activated/phosphorylated HER2 in order to establish HER2 (Y1248) as a novel treatment decision marker for breast cancer patients.

A technical assistant working in the lab of Experimental Pathology at the Technische Universität München, Germany (© Institut für Pathologie, TU München).