MicroRNAs (miRNAs) have been linked to virtually all known biological processes, including cancer. Worldwide, hepatocellular carcinoma (HCC) is the sixth most frequent cancer, and the fourth leading cause of cancer-related death. Liver progenitor cells (LPCs) offer great potential as a cell-based therapy to treat chronic liver disease including HCC. However, LPCs are prone to transformation in culture, and there is increasing evidence to suggest that HCC arises from LPCs in vivo.The aim of this study was to determine the changes in miRNA expression, and to evaluate their role, in LPC transformation
Microarray analysis of miRNA abundance in transformed LPCs relative to non-transformed LPCs disclosed many dysregulated miRNAs. Out of the 1412 miRNAs arrayed 422 were significantly altered (p-value < 0.05). Of these, 42 miRNAs were altered by greater than 25-fold, and 20 miRNAs by more than 100-fold. qPCR-based TaqMan miRNA assays were used to validate these findings.
Closer data analysis revealed many dysregulated miRNAs that were clustered within the genome. This suggested that changes in mature miRNA expression could be due to genomic deletions or amplifications. The inability to PCR amplify three separate regions of genomic DNA from transformed cells harboring down-regulated miRNA clusters indicated that genomic deletion likely accounts for the large decreases in miRNA expression, consistent with gross chromosomal changes that had been observed by karyotyping.
Searching the literature for potential targets of dysregulated miRNAs disclosed several candidates that have been implicated in HCC. Western blot analyses revealed a potential link between miR-20a, which was decreased ~280-fold in transformed LPCs, and its respective published target LRF. Furthermore, this was accompanied by decreases in LRF repressed proteins, p19ARF and p53. MiRNA inhibitors and mimics were used to alter the expression of miR-20a in non-transformed LPCs to confirm their effect on LRF expression.