Purpose: Pancreatic endocrine neoplasms (PENs) are rare, mostly well-differentiated endocrine neoplasms, whose biology has been poorly characterized. Global expression microarrays can document abnormal pathways that impact on tumorigenesis and disease progression.
Experimental design: RNA was extracted from eight well-differentiated PENs and three highly enriched pancreatic islet cell samples (80-90% purity), and examined using the Affymetrix U133A oligonucleotide microarray. Microarray data were normalized using dCHIP for identification of differentially expressed genes. PEN tissue microarrays were constructed from 53 archival PENs for immunohistochemical validation of microarray data.
Results: Sixty-six transcripts were overexpressed > or =3-fold in PENs compared with normal islet cells, including putative oncogenes (MLLT10/AF10), growth factors [insulin-like growth factor-binding protein 3 (IGFBP3)], cell adhesion and migration molecules (fibronectin), and endothelial elements (MUC18/MelCAM and CD31). A total of 119 transcripts were underexpressed < or =3-fold in PENs compared with normal islet cells, including cell cycle checkpoint proteins (p21/Cip1), the MIC2 (CD99) cell surface glycoprotein, putative metastasis suppressor genes (NME3), and junD, a MEN1-regulated transcription factor. Using PEN tissue microarrays, we confirmed the differential up-regulation of IGFBP3 (70%) and fibronectin (22%) and differential down-regulation of p21 (46%) and MIC2 (CD99; 91%) in PENs versus normal pancreatic islets. IGFBP3 overexpression was significantly more common in metastatic (93%) versus primary PEN lesions (60%), P=0.022. Fibronectin overexpression demonstrated a trend toward significance in lymphatic PEN metastases (55%) compared with primary PEN lesions (24%; P=0.14).
Conclusions: Global expression analysis provides insight into tumorigenic pathways in PENs and may identify potential prognostic and therapeutic markers for these uncommon neoplasms.