MicroRNA Expression during the Colorectal Adenoma-Adenocarcinoma Sequence
AN Bartley, KA Patel, BA Barkoh, B Mishra, H Yao, A Rashid, R Luthra, SR Hamilton. The University of Texas MD Anderson Cancer Center, Houston, TX
Background: Micro-RNAs (miRNAs) are small (22 nucleotide) non-coding RNAs that regulate gene expression, and their expression is altered in most tumor types including colorectal adenocarcinomas (CAC). Although several studies have identified miRNAs differentially expressed in CAC compared to non-neoplastic colorectal mucosa (NNM), limited information is available on miRNAs associated with progression in the adenoma-CAC sequence. We therefore profiled CAC, high-grade and low-grade intra-epithelial neoplasia/dysplasia in adenomas where they arose, and adjoining NNM.
Design: RNA was isolated with RecoverAll (Applied Biosystems, CA) from 34 samples of manually microdissected formalin-fixed paraffin-embedded tissue from 10 patients with resected stage I, II, or III CAC. Expression levels of 416 miRNAs were determined with Agilent miRNA microarray. Statistical analyses were performed with analysis of variance, Fisher's exact test and Tukey honest significant difference test.
Results: Unsupervised cluster analysis segregated the samples into three groups based on disease progression in 88 differentially expressed miRNAs, (p<0.001). A class comparison analysis identified 87 of 88 miRNAs had differential expression between NNM and CAC, 77 between NNM and LGD, 42 between NNM and HGD, 3 between LGD and HGD, 20 between LGD and CAC, and 19 between HGD and CAC. Nine of 88 miRNAs were differentially expressed between NNM and LGD, LGD and CAC, and NNM and CAC (p < 0.05), four of which are upregulated (miR-34a, 34b, 99a, and 224) and five downregulated (miR-206, 516a-5p, 617, 1208, and 1285). miR-34b, -99a, -206, -224, and -516a-5p were differentially expressed between NNM and HGD (p < 0.01), and miR-99a, -516a-5p, -617 and -1285 were differentially expressed between HGD and CAC (p < 0.01). miR-1285 was also significantly different between LGD and HGD (p<0.05).
Conclusions: We identified nine miRNAs differentially expressed in the histopathologic lesions of colorectal carcinogenesis; six not described previously in neoplastic progression in the large bowel. A separate confirmation set from 10 additional patients is currently being profiled for validation, and RT-PCR confirmation in all samples is in progress. Our findings suggest that various miRNAs play specific roles in the sequences of events leading to colorectal adenocarcinoma, and their use as biomarkers or as therapeutic targets therefore may depend upon the timing of their use during progression.
Monday, March 22, 2010 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 87, Monday Morning