Identification by Real-time PCR of 13 mature microRNAs differentially expressed in colorectal cancer and non-tumoral tissues

Abstract

MicroRNAs (miRNAs) are short non-coding RNA molecules playing regulatory roles by repressing translation or cleaving RNA transcripts. Although the number of verified human miRNA is still expanding, only few have been functionally described. However, emerging evidences suggest the potential involvement of altered regulation of miRNA in pathogenesis of cancers and these genes are thought to function as both tumours suppressor and oncogenes. In our study, we examined by Real-Time PCR the expression of 156 mature miRNA in colorectal cancer. The analysis by several bioinformatics algorithms of colorectal tumours and adjacent non-neoplastic tissues from patients and colorectal cancer cell lines allowed identifying a group of 13 miRNA whose expression is significantly altered in this tumor. The most significantly deregulated miRNA being miR-31, miR-96, miR-133b, miR-135b, miR-145, and miR-183. In addition, the expression level of miR-31 was correlated with the stage of CRC tumor. Our results suggest that miRNA expression profile could have relevance to the biological and clinical behavior of colorectal neoplasia.

Figure 1

Hierarchical clustering of miRNA in CRC cell lines. 15 CRC cell lines were clustered according to the expression profile of 44 miRNAs differentially expressed and commonly detected with the three different normalization approach used between CRC and normal cell line (average linkage and Euclidean distance as similarity measure). Data from each miRNA were median centered and RQ was determined as described in material and methods. Dendrograms indicate the correlation between groups of samples and genes. Samples are in columns and miRNAs in rows. The expression values ranged from + 5 log₁₀ to - 5 log₁₀.

Figure 2

miRNA expression data from 12 CRC tumor samples. Each miRNA listed was detected as significantly differentially expressed between tumoral and paired-non-tumoral tissues with SAM and Class Comparison tests. Samples are in columns and miRNAs in rows. The expression values ranged from + 1.5 log₁₀ to - 1.5 log₁₀.

Figure 3

Hierachical clustering of CRC cell lines and tumor samples by using expression of 13 miRNAs that have found differentially expressed between neoplastic conditions (CRC cell lines and tumor samples) and non-tumoral colon tissues. Samples are in columns and miRNAs in rows.

Figure 4

Real-time PCR analysis of miR-31 expression between stage II and stage IV tumor samples. Differences was significant after Mann Whitney U test (p = 0.028).