Contribution of microRNA-200b-3p to radiation therapy resistance in 22RV1 prostate cancer cells.

Abstract

89 Background: Radiation therapy (RT) is a standard treatment option for men with localized prostate cancer. Despite having well-established treatment regimens, such men still fail RT at a rate of up to 30-50%. RT resistant phenotype is a key component leading to treatment failure. MicroRNAs (miRNAs) can influence the response to RT, and the abundance or lack of certain miRNAs can induce a RT resistant phenotype through alteration of survival pathways. We show that altered expression of miR-200b-3p plays an important role in contributing to RT resistance. Methods: RT resistant subline from the parental 22RV1 prostate cancer cell line was generated by exposure to fractionated RT – 22RV1-RT. The global expression level of miRNAs and mRNA was determined, using the Affymetrix GeneChip®: miRNA 4.0 and Human Gene 2.0 ST Arrays. Parental and 22RV1-RT cells were transfected with miR-200b-3p mimics or negative control. The influence of miR-200b-3p on cellular proliferation, morphology, migration, clonogenic survival and response to RT was determined by standard assays. Results: MiR-200b-3p was the only miRNA that was statistically differentially expressed between the two cell lines. There were 39 differentially expressed genes. Of the 65 genes predicted to be regulated by miR-200b-3p as identified from miRTarBase, only Fibronectin 1 (FN1) was in common. FN1 was up-regulated in 22RV1- RT cells. MiR-200b-3p mimics; in comparison to negative control mimics, suppressed cell proliferation in both cell lines. Both cell lines with negative control mimics have fibroblastic-type morphology and display a stretched shape following RT. While, cells transfected with miR-200b-3p mimics demonstrated a round morphology and formed clusters following RT. Over-expression of miR-200b-3p mimics inhibited cell migration synergically with RT and demonstrated a lower degree of clonogenic survival following RT in 22RV1-RT cells compared to negative control mimics. Surprisingly, miR-200b-3p mimics reversed the observed RT resistance and the sensitivity to RT was to the same degree as the parental 22RV1 cells. Conclusions: Together, these data suggest that miR-200b-3p independently contributes to RT resistance in 22RV1 prostate cancer cells.