Colorectal tumour microRNAs – novel biomarkers of tumour progression and treatment response?


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Edward Amankwatia1, Francis Carey1, Robert Steele1, Alastair Munro1, Roland Wolf1, Gillian Smith1
1University of Dundee, Dundee, UK

Background

MicroRNAs (miRNAs), small non-coding RNAs, are important regulators of gene expression (1). MiRNA regulation of the expression of tumour suppressor genes and oncogenes including KRAS may influence cancer development and progression. Analysis of individuality in miRNA expression in colorectal tumours may therefore lead to the identification of novel biomarkers of disease progression and/or treatment response.

Method

We have used qRT-PCR analysis (Taqman Low Density Arrays) to profile miRNA expression in matched colorectal tumours and adjacent mucosa (n=12), in pre-cancerous colorectal polyps (n=6) and in HCT-116 colorectal cells lines engineered to express WT and mutant KRAS. We then used DIANA lab DNA Intelligent Analysis software (http://diana.cslab.ece.ntua.gr/) to identify candidate target genes for each differentially expressed miRNA.

Results

We identified several differentially expressed miRNAs, which may have utility as diagnostic or therapeutic biomarkers in colorectal cancer patients. MicroRNA-224 (miR-224) is significantly increased in WT HCT-116 cells compared to isogenic mutant KRAS cells, and is also significantly higher in WT KRAS and BRAF colorectal tumours relative to tumours with either KRAS or BRAF mutations. Using in silico predictive tools, we have identified multiple target genes for miR-224, including genes e.g. MMP9, SMAD4 and API5, involved in key signalling pathways promoting cancer progression. We used antagomirs to knockdown miR-224 expression in WT HCT-116 cells to investigate the effect of miR-224 expression on cell phenotype, and showed that miR-224 knockdown influenced sensitivity (>2-fold differences in IC50 values) to both 5-flourouracil and oxaliplatin, drugs commonly used in the treatment of colorectal cancer. Quantitative cell growth, invasion and migration assays are in progress to further examine the phenotypic consequences of miR-224 knockdown.

Conclusion

Our data identifies a role for miR-224 as a candidate biomarker of KRAS and BRAF mutation status in colorectal tumours. Individuality in miR-224 expression may influence both tumour progression and chemosensitivity.