[620] Esophageal Adenocarcinomas Overexpress MicroRNA-21: A Tissue Microarray Study of 64 Cases Using In-Situ Hybridization

JJ Liu, M Bloomston, M Dilhoff, MM Yearsley, WL Frankel. Ohio State University, Columbus, OH

Background: MicroRNAs (miR) are short naturally occurring single-stranded RNA molecules that regulate expression of target genes post-transcriptionally. They have been implicated as key regulatory molecules in tumors where they can function as both tumor suppressors and oncogenes. MiR-21 is one of the most commonly deregulated miR in many malignancies. We compared expression of miR-21 in esophageal adenocarcinoma (Ad) and Barrett's esophagus without (B) and with dysplasia (BD) to investigate miR-21 in progression of Barrett's esophagus to adenocarcinoma.
Design: Archival files from our institution were searched for esophageal Ad resection specimens, and cases were reviewed for Ad, B, BD, and normal glands (NG). These areas were cored from formalin-fixed, paraffin embedded blocks (2 cores per block) and were arrayed to create a tissue microarray of cores 2.0 mm each. Sections were pre-hybridized with Exiqon hybridization buffer. Exiqon DIG-labeled miRCURY LNA probes of miR-21, U6, and Scramble were then added to the slides at a 50nM and hybridized for 20 hours and detected using alkaline phosphatase conjugated anti-DIG Fab fragment (probes provided by Exiqon). Controls stained appropriately and slides were interpreted by 2 pathologists. MiR-21 was graded as negative, weakly positive (1+) or strongly positive (2+).
Results: 64 Ad (5 well, 35 moderate, 24 poorly differentiated) were identified with sufficient tissue for evaluation of B in 20 and BD in 14.

MiR-21 Expression

	Number	Negative	1+	2+
Normal Glands	43	40 (93%)	3 (7%)	0
Barrett	20	16 (80%)	4 (20%)	0
Barrett Dysplasia	14	2 (14%)	12 (86%)	0
Adenocarcinoma	64	7 (11%)	36 (56%)	21 (33%)

MiR-21 was overexpressed in Ad (89%, 57/64) and BD (86%, 12/14) with strong staining in Ad (33%, 21/64) and not in BD. Weak expression of miR-21 was seen in NG and B in 7% (3/43) and 20% (4/20), respectively. MiR-21 expression was significantly increased in Ad and BD as compared to B and NG (p<0.005). There was no significant difference in miR-21 expression among the grades of Ad.
Conclusions: MiR-21 is overexpressed in Ad and BD as compared to B or NG suggesting that miR-21 has a role in the progression of Barrett's esophagus to Ad. Although the percent of areas with overexpression of miR-21 was similar in Ad and BD, strong staining was only seen in Ad further supporting the role of miR-21 in carcinogenesis. Additional studies are necessary to evaluate the association of miR-21 with outcome.
Category: Gastrointestinal

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 112, Tuesday Afternoon