Expression of transforming growth factor-alpha and epidermal growth factorreceptor in gastrointestinal stromal tumours

Activation of epidermal growth factor receptor (EGFR) is associated with ce ll growth and transformation. Both transforming growth factor-alpha (TGF-al pha) and epidermal growth factor bind to and activate EGFR. We studied the expression of TGF-alpha and two EGFRs (HER-1 and HER-2) in gastrointestinal stromal tumours (GISTs) of the stomach (n=9) and small intestine (n=6) usi ng standard immunostaining techniques in paraffin-embedded sections. Most G ISTs expressed TGF-alpha, and a few expressed HER-1. All HER-1-positive tum ours expressed TGF-alpha. These results suggest that a TGF-alpha/EGFR autoc rine loop is present in GIST and that TGF-alpha promotes proliferation of G IST tumour cells through its interaction with HER-1 in at least some GISTs. This is the first description of an autocrine loop in GIST. In contrast, H ER-2 is not expressed in any GIST.