Increased EpCAM expression in malignant insulinoma: potential clinical implications.

OBJECTIVE: EpCAM (CD326) is overexpressed in progenitor cells of endocrine pancreatic islands of Langerhans during fetal development and was suggested to act as a morphoregulatory molecule in pancreatic island ontogeny. We tested whether EpCAM overexpression is reactivated in insulinomas, endocrine tumors arising in the pancreas. DESIGN/
METHOD: We used monoclonal anti-EpCAM antibody Ber-Ep4 for immunohistochemistry on formalin-fixed and paraffin-embedded tumor material. We analyzed 53 insulinomas: 40 benign (disease stage<IIa) and 13 malignant tumors (disease stage IIIb/IV). Disease stage disposition followed new TNM classification of the European Neuroendocrine Tumor Society (ENETS) for foregut neuroendocrine tumors (2006). Additionally, ten insulinoma metastases were analyzed. Clinical follow-up was available for overall survival analysis from 49 patients. The EpCAM expression of the islands of Langerhans was classified as 2+ in healthy pancreatic tissue.
RESULTS: In 38% of the benign insulinomas (disease stage<IIa), we found strong (3+) EpCAM expression. In contrast, malignant insulinomas (disease stage IIIb/IV) and their metastases exhibited a strong (3+) EpCAM expression with 78 and 80% respectively, significantly more frequent (P<0.01). The malignant tissue was characterized by a significantly lower number of unstained cells and significantly higher number of 3+ stained cells. Quantitative PCR for EpCAM mRNA validated strong EpCAM expression in malignant insulinoma. Kaplan-Meier curves indicated survival disadvantage for EpCAM 3+ insulinomas, but this was not statistically significant (log-rank test).
CONCLUSION: This first EpCAM expression study in benign/malignant insulinomas indicates that strong EpCAM expression could help to identify patients at risk for malignant disease and might be used as a therapeutic target for antibody-based therapies in patients with metastatic insulinoma.