Increased concentrations of growth factors and activation of the EGFR system in breast cancer.

Background: In this study the total and phosphorylated amount of epidermal growth factor receptor 1 (EGFR) and 2 (HER2) were measured together with EGFR ligands in tissue samples of breast cancer patients in order to investigate interrelations and possible prognostic values.

Methods: Samples of malignant and non-cancer autologous reference tissue were collected from 415 breast cancer patients. The tissue samples were cut and either paraffin-embedded or homogenized in a lysis buffer to extract the proteins. HER2 was measured using both immunohistochemistry (IHC)/fluorescence in situ hybridization (FISH) and ADVIA Centaur. Phosphorylated HER2 and EGFR (pHER2, pEGFR), total EGFR and the ligands: epidermal growth factor (EGF), transforming growth factor-α (TGFα), amphiregulin (AREG), heparin-binding EGF-like growth factor (HB-EGF), betacellulin (BTC) and epiregulin (EREG) were measured using the Luminex.

Results: The HER2 positivity rate was determined to be 25.2% by the Centaur method vs. 15.8% by IHC and FISH. HER2, HB-EGF, TGFα and AREG were upregulated in cancer tissue as compared with autologous reference tissue while EGFR, pEGFR and EGF were downregulated (p<10-6). pEGFR in autologous reference tissue was negatively correlated to the number of positive lymph nodes and to the tumor size (p=0.0007 and p=0.001, respectively) and furthermore, decreased in the group of mastectomy operated patients as compared with the lumpectomy group (p<10-6). HB-EGF in cancer tissue was positively associated with high grade tumors (p<10-6) and pHER2, HB-EGF and BTC were associated with poor disease free survival (p=0.017, p=0.012 and p=0.0026, respectively).

Conclusions: Our study demonstrated a profound activation of the EGFR system. HB-EGF was increased by factor 10 in cancer tissue and related to the biological aggressiveness of the tumors, and pHER2, HB-EGF and BTC were associated with poor clinical outcome.