MicroRNA expression patterns to differentiate pancreatic adenocarcinoma from normal pancreas and chronic pancreatitis.
BACKGROUND
While global microRNA (miRNA) expression patterns of many embryologic, physiologic, and oncogenic processes have been described, description of the role of miRNAs in ductal adenocarcinoma of the pancreas is lacking.


OBJECTIVE
To define the expression pattern of miRNAs in pancreatic cancer and compare it with those of normal pancreas and chronic pancreatitis.


METHODS
Specimens were obtained at a National Cancer Institute-designated comprehensive cancer center from patients with ductal adenocarcinoma of the pancreas (n = 65) or chronic pancreatitis (n = 42) (January 2000-December 2005). All patients underwent curative pancreatectomy; those with pancreatic cancer were chemotherapy-naive. RNA harvested from resected pancreatic cancers and matched benign adjacent pancreatic tissue as well as from chronic pancreatitis specimens was hybridized to miRNA microarrays.


METHODS
Identification of differentially expressed miRNAs that could differentiate pancreatic cancer from normal pancreas, chronic pancreatitis, or both, as well as a pattern of miRNA expression predictive of long-term (>24 months) survival. Significance of Analysis of Microarrays and Prediction of Analysis of Microarrays were undertaken to identify miRNAs predictive of tissue type and prognosis. P values were calculated by t test, adjusted for multiple testing. Kaplan-Meier survival curves were constructed using mean miRNA expression (high vs low) as threshold and compared by log-rank analysis.


RESULTS
Twenty-one miRNAs with increased expression and 4 with decreased expression were identified that correctly differentiated pancreatic cancer from benign pancreatic tissue in 90% of samples by cross validation. Fifteen overexpressed and 8 underexpressed miRNAs differentiated pancreatic cancer from chronic pancreatitis with 93% accuracy. A subgroup of 6 miRNAs was able to distinguish long-term survivors with node-positive disease from those dying within 24 months. Finally, high expression of miR-196a-2 was found to predict poor survival (median, 14.3 months [95% confidence interval, 12.4-16.2] vs 26.5 months [95% confidence interval, 23.4-29.6]; P = .009).


CONCLUSIONS
Pancreatic cancer may have a distinct miRNA expression pattern that may differentiate it from normal pancreas and chronic pancreatitis. miRNA expression patterns may be able to distinguish between long- and short-term survivors, but these findings need to be validated in other study populations.
Bloomston
Mark
M
Division of Surgical Oncology, James Cancer Hospital and Solove Research Institute, Ohio State University, Columbus, USA. mark.bloomston@osumc.edu
Frankel
Wendy L
WL
Petrocca
Fabio
F
Volinia
Stefano
S
Alder
Hansjuerg
H
Hagan
John P
JP
Liu
Chang-Gong
CG
Bhatt
Darshna
D
Taccioli
Cristian
C
Croce
Carlo M
CM
D015152:Blotting, Northern; D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics*; D005819:Genetic Markers; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D035683:MicroRNAs / Q000032:analysis*; D020411:Oligonucleotide Array Sequence Analysis; D010179:Pancreas / Q000033:anatomy & histology / Q000737:chemistry*; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D050500:Pancreatitis, Chronic / Q000235:genetics* / Q000473:pathology; D016133:Polymerase Chain Reaction; D011379:Prognosis; D012334:RNA, Neoplasm / Q000032:analysis; D046888:Tissue Array Analysis
D005819:Genetic Markers; D035683:MicroRNAs; D012334:RNA, Neoplasm