PURPOSE: We investigated the global microRNA expression patterns in normal 
pancreas, pancreatic endocrine tumors and acinar carcinomas to evaluate their 
involvement in transformation and malignant progression of these tumor types. 
MicroRNAs are small noncoding RNAs that regulate gene expression by targeting 
specific mRNAs for degradation or translation inhibition. Recent evidence 
indicates that microRNAs can contribute to tumor development and progression and 
may have diagnostic and prognostic value in several human malignancies.
MATERIALS AND METHODS: Using a custom microarray, we studied the global microRNA 
expression in 12 nontumor pancreas and 44 pancreatic primary tumors, including 
12 insulinomas, 28 nonfunctioning endocrine tumors, and four acinar carcinomas.
RESULTS: Our data showed that a common pattern of microRNA expression 
distinguishes any tumor type from normal pancreas, suggesting that this set of 
microRNAs might be involved in pancreatic tumorigenesis; the expression of 
miR-103 and miR-107, associated with lack of expression of miR-155, 
discriminates tumors from normal; a set of 10 microRNAs distinguishes endocrine 
from acinar tumors and is possibly associated with either normal endocrine 
differentiation or endocrine tumorigenesis; miR-204 is primarily expressed in 
insulinomas and correlates with immunohistochemical expression of insulin; and 
the overexpression of miR-21 is strongly associated with both a high Ki67 
proliferation index and presence of liver metastasis.
CONCLUSION: These results suggest that alteration in microRNA expression is 
related to endocrine and acinar neoplastic transformation and progression of 
malignancy, and might prove useful in distinguishing tumors with different 
clinical behavior.