Dysregulated MicroRNAs Contribute to Chemotherapy-Resistance of Pleural Mesothelioma

Abstract Background Dysregulated expression of microRNAs has been shown to contribute to response to chemotherapeutic agents in several cancers, including pleural mesothelioma (PM). In previous work, we found expression of several tissue-microRNAs to correlate with patient’s response to cisplatin-pemetrexed. Aims We want to understand how altering the expression of these microRNAs affects cell growth and chemo response. Methods PM cell lines MSTO-211H (biphasic), H28, Meso-1, Mero-82 (epithelioid) and non-malignant MeT-5A were reverse transfected with synthetic microRNA mimics for 15 candidates. Following transfection, cell growth, colony forming ability, and migratory potential were assessed using standard assays. Furthermore, transfected cells were exposed to increasing concentrations of cisplatin to evaluate sensitivity to these drugs. Results Overexpression of seven candidate microRNAs resulted in growth inhibition in all investigated PM cell lines five days post transfection. The strongest effects were observed for miR-380-5p, miR-221-3p, miR-210, miR-625-3p, and miR-19b, which reduced cell growth to 30-60%. Growth of non-malignant MeT-5A cells remained largely unaffected (Fig. A). Overexpression of those microRNAs also resulted in a strong reduction of colony forming ability (Fig. B), while an effect on wound healing capacity (migration) could not be observed. Finally, we found that especially overexpression of miR-221-3p, miR-625-3p and miR-19b was able to sensitise cells towards cisplatin, with the strongest effect observed in MSTO-211H for miR-221-3p (IC50 from 17.6µM to 2.7µM) and miR-19b (IC50 from 17.6µM to 0.7µM), and in Mero-82 for miR-625-3p (IC50 from 3.75µM to 0.8µM) (Fig. C). Conclusion We show that overexpression of several microRNAs has the potential to alter PM cell growth and colony forming ability. Furthermore, microRNA overexpression can sensitise cells towards cisplatin, although the degree of sensitisation varies between different cell lines. Current analyses focus on the response towards the cisplatin/pemetrexed doublet and on the effect on cell cycle and expression of associated genes.