The poor prognosis and lack of effective treatments for pancreatic cancer arise from several causes. There are currently no effective biomarkers useful for early detection of pancreatic cancer that tends to rapidly invade surrounding structures and undergo early metastatic spreading. Moreover, pancreatic cancer is highly resistant to both chemotherapy and radiation therapy. Currently, the molecular basis for these characteristics is unknown. Gene expression profiles provide important information about the molecular characteristics of the cancers and can be used to distinguish closely related cancer subtypes. Gene profiling can also be used to develop candidate biomarkers and to identify groups of genes involved in specific functional aspects of tumor biology. Gene expression profiles that could distinguish between pancreatic tumors, chronic pancreatitis and normal pancreatic tissue have been studied extensively using different microarrays and microarray platforms. The differentially expressed genes in pancreatic tumor tissues were found to be quite specific and highly reproducible among platforms and studies (Crnogorac-Jurcevic T, Efthimiou E, Nielsen T, Loader J, Terris B, Stamp G, Baron A, Scarpa A and Lemoine NR. Expression profiling of microdissected pancreatic adenocarcinomas. Oncogene 2002; 21: 4587-4594. Han H, Bearss DJ, Browne LW, Calaluce R, Naagle RB, Von Hoff DD. Identification of differentially expressed genes in pancreatic cancer cells using cDNA microarray. Cancer Res 2002; 62: 2890-96. Iacobuzio-Donahue CA, Ashfaq R, Maitra A, Adsay NV, Shen-Ong GL, Berg K, Hollingsworth MA, Cameron JL, Yeo CJ, Kern SE, Goggins M, Hruban RH. Cancer Res 2003; 63: 8614-22. Logsdon CD, Simeone DM, Binkley C, Arumugam T, Greenson JK, Giordano TJ, Misek DE, Hanash S. Molecular profiling of pancreatic adenocarcinoma and chronic pancreatitis identifies multiple genes differentially regulated in pancreatic cancer. Cancer Res 2003; 63: 2649-57).