Expression of TGF-alpha in neuroendocrine tumours of the distal colon and rectum

Aim. Transforming growth factor alpha (TGF-alpha) has been localized in neuroendocrine L-cells of the colon and rectum in previous studies. We examined whether neuroendocrine tumours with L-cell differentiation express TGF-alpha. Experimental design. Immunohistochemistry was performed for proglucagon- and pro-pancreatic polypeptide derivatives, as well as for TGF-alpha, and epidermal growth factor receptor (EGFR) using paraffin sections from 16 neuroendocrine tumours of the colon and rectum. Also, in situ hybridization for TGF-alpha and proglucagon was carried out. Main results. A strong expression of TGF-alpha at the protein level can be shown for neuroendocrine tumours of the hindgut. In one third of our cases we found a strong hybridization signal and in two thirds a moderate signal for TGF-alpha. The immunohistological phenotype concerning gut hormones is highly heterogeneous. Glucagon-like peptide 2 (GLP2) in our series was the most sensitive immunohistological hormone marker. Major conclusions. The immunophenotype of colorectal neuroendocrine tumours regarding hormone markers is heterogeneous. The expression of TGF-alpha corresponds to the immunohistological profile of normal L-cells. TGF-alpha, especially in the neuroendocrine L-cells, most probably acts as a multifunctional trophic factor responsible for cellular integrity and survival, and not as an oncogenic growth factor.