Genome-wide analysis of differentially expressed miRNA in PLX4720-resistant and parental human thyroid cancer cell lines

BackgroundInvestigating BRAF(V600E) inhibitors (BRAFi) as a strategy to treat patients with aggressive thyroid tumors harboring the BRAF(V600E) mutant currently is in progress, and drug resistance is expected to pose a challenge. MicroRNAs (miRNAs) are involved in development of resistance to a variety of drugs in different malignancies.MethodsmiRNA expression profiles in the human anaplastic thyroid cancer cell line (8505c) were compared with its PLX4720-resistant counterpart (8505c-R) by the use of Illumina deep sequencing. We conducted a functional annotation and pathway analysis of the putative and experimentally validated target genes of the significantly altered miRNAs.ResultsWe identified 61 known and 2 novel miRNAs whose expression was altered greatly in 8505c-R. Quantitative reverse-transcription polymerase chain reaction validated altered expression of 7 selected miRNAs in 8505c-R and BCPAP-R (PLX4720-resistant papillary thyroid cancer cell line). We found 14 and 25 miRNAs whose expression levels changed substantially in 8505c and 8505c-R, respectively, after treatment with BRAFi. The mitogen-activated protein kinase and phosphatidylinositol 3-kinase-AKT pathways were among the prominent targets of many of the deregulated miRNAs.ConclusionWe have identified a number of miRNAs that could be used as biomarkers of resistance to BRAFi in patients with thyroid cancer. In addition, these miRNAs can be explored as potential therapeutic targets in combination with BRAFi to overcome resistance.