Abstract C22: Identification of candidate microRNAs that correlate with sensitivity to the IGF-1R/IR inhibitor, OSI-906, in colorectal cancer (CRC) cell lines

Abstract

Abstract Background: MicroRNAs (miRNAs) are small ∼20–22 nucleotide noncoding RNAs, thatwhich function as antisense regulators of gene expression by targeting specific mRNAs, and thereby modulate a variety of cellular signaling pathways. Deregulation of miRNA expression contributes to specific oncogenic events in human cancers and therefore may contribute to have a role in resistance to targeted cancer therapies. This study was based upon the hypothesis Here, we hypothesized that miRNA expression profiles wouldcan predict sensitivity to the novel IGF-1R tyrosine kinase inhibitor, OSI-906, in colorectal cancer (CRC) cell lines. Materials and Methods: To evaluate the sensitivity of CRC cells to OSI-906, a panel of 27 lines was exposed to increasing concentrations of the drug and assessed for proliferation using the sulforhodamine B assay. Six cell lines were sensitive (S, IC50 < 1.5 mol/L) and 21 were resistant (R, IC50 > 1.5 mol/L) to OSI-906. Baseline total RNA was isolated from 4 S and 4 R cell lines for miRNA and mRNA profiling on Dharmacon miRNA microarray and Affymetrix HG-U133 Plus 2.0 microarray platforms, respectively. For miRNA microarray data pre-processing, 342 miRNA probes with relative intensity of p ≤ 0.01 in at least 2 of the 8 experiments were kept for further data analysis. For mRNA microarray analysis, probe sets representing the same gene were collapsed based on maximum values and the expression levels were converted to a rank-based matrix. Anti-sense and mimic-miRNAs were used to study the effects of loss- and gain-of-function for the identified candidate miRNAs. Results: Significance Analysis of Microarray was used to determine the differentially expressed miRNAs in cell lines S or R to OSI-906 S vs. R cell lines profiles. Thirteen13 miRNAs were identified which showed a positive correlation with OSI-906 sensitivity. Three and 10 miRNAs were under- orand over-expressed in OSI-906 S cell lines, while respectively. gGene expression analysis revealed 78 and 42 genes under- orand over-expressed in OSI-906 S cell lines (p < 0.005), respectively. By comparing the predicted miRNA targets and differentially expressed genes, we identified two candidate miRNAs (hsa-miR-181a and hsa-miR-224) where the expression of their potential target genes, metallothioneins 1E and 2A (MT1E and MT2A) showed an inverse correlation with OSI-906 sensitivity. This observation was confirmed by qRT-PCR on both miRNAs and their target genes. To assess the loss- and gain-of-function effects of the candidate miRNAs, we delivered mimic- and anti-sense miRNAs to the OSI-906 R and S cell lines, respectively. Interestingly, over-expression of the miR-181a and miR-224 mimics in the OSI-906 R cell lines resulted in increased sensitivity to the drug, whereas. However, silencing of these miRNAs in the S cell lines did not demonstrateshow the reverse effect. Conclusion: These results suggest that loss of the candidate miRNA expression can confer OSI-906 resistance. Restoring the expression of these candidate miRNAs may induce sensitivity to OSI-906 in resistant CRC cell lines and may have clinical significant application in the targeted therapy of patients with advanced CRC. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C22.