MAGE1 Is Expressed by a Subset of Pancreatic Endocrine Neoplasms and Associated Lymph Node and Liver Metastases

Background. MAGE1 was originally isolated from human melanoma cells as a target antigen for autologous cytotoxic T lymphocytes. Expression of MAGE1 has subsequently been identified in a number of neoplastic cell types, including testicular germ cell and breast cancer cells, which has led to the development of antitumor MAGE1 vaccines. Aim of the Study. To determine if Mage-1 is expressed in pancreatic endocrine neoplasms (PENs) and PEN metastases. Methods. We utilized immunolabeling analysis for Mage-1 on 49 primary PENs, 11 liver metastases, and 6 lymph node metastases. A semiquantitative labeling index (LI) of 0 (no expression), 1 (minimally detectable expression), 2 (moderate expression), and 3 (intense expression, correlating with internal control markers) was used to determine relative amounts of MAGE1 expression in these lesions. Results. We have identified MAGE1 expression in a subset (42 of 49; 86%) of PENs. Normal pancreatic ducts, present in tissue adjacent to PENs, were utilized as a positive control for Mage-1 immunolabeling (index score 3); no other detectable labeling for Mage-1 was evident in normal pancreatic tissue. Primary PENs, with or without metastases (mean LI score 1.2 vs 1.0, respectively), did not demonstrate a significant difference in Mage-1 LI, although intratumoral heterogeneity was apparent in some, but not all, of these lesions. Lymph node metastases (mean score 2.0) demonstrated a significant increase in Mage-1 LI as compared to primary, non-metastatic lesions (p = 0.04984) and primary metastatic lesions (p = 0.02351). In contrast, six patients with a survival of less than one year demonstrated a low Mage-1 LI (mean score, 0.58). Conclusions. MAGE1 expression is present in a subset of primary PENs and in lymph node metastases, and may therefore serve as a useful marker and potential therapeutic target in PENs. Furthermore, the absence of Mage-1 expression in a subset of primary PENs may indicate a worsened prognosis.