The novel tumor angiogenic factor, adrenomedullin-2, predicts survival in pancreatic adenocarcinoma

Background: Tumor angiogenesis has been demonstrated to have an important role in the development, progression, and metastasis of pancreas cancer. Adrenomedullin-2 (ADM2) is a calcitonin gene-related peptide that has recently been shown to be a novel tumor angiogenesis factor, acting via mitogen-activated protein kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinase/Akt, and vascular endothelial growth factor/vascular endothelial growth factor-2 signaling pathways. Through the use of tissue microarray (TMA) technology, we hypothesize that ADM2 is an important tumor angiogenesis factor in pancreatic cancer.

Methods: Multiple TMAs were created using tissue from pancreatic cancer patients resected between January 1996 and December 2006. Core tissue samples of formalin-fixed, paraffin-embedded blocks of pancreatic cancer tissue were collected through an institutional review board-approved protocol and linked to available clinicopathologic data. Two TMAs consisting of 112 and 60 patients with pancreatic adenocarcinoma were studied for ADM2 protein expression using a quantitative, automated immunofluorescent microscopy system, a technology that removes potential observer bias in TMA analysis. The results were analyzed using independent Student t-test, chi-square, log-rank regression, and Kaplan-Meier methods.

Results: One hundred sixteen patients were identified for complete analysis, and 56 patients had complete survival data. Median follow-up for survivors was 14.5 mo. Total cellular levels of ADM2 were found to be a predictor of survival in pancreatic cancer. Low ADM2 levels were associated with a higher 5-y survival compared with high ADM2 levels (18% versus 6%, P = 0.05). Median survival was also worse in high ADM2 expressers (18.7 versus 8.6 mo). In accordance with prior-published pancreatic cancer data, a worse histologic grade (P = 0.001), tumor (T) stage (P = 0.009), and overall disease stage (P = 0.004), all portended a worse survival.

Conclusions: For the first time, we have demonstrated that high levels of ADM2 expression predict a poorer survival in patients with pancreatic adenocarcinoma. This suggests a possible role of ADM2 in pancreas cancer and as a novel biomarker that predicts poorer survival. Additional study of ADM2 in pancreatic cancer will help reveal its true angiogenic role in pancreas cancer and its potential role as a novel therapeutic target.