Background: Malignant Mesothelioma (MM) is an aggressive cancer associated with asbestos exposure. MM has a poor prognosis, therefore novel therapeutic targets are required. Recent studies have demonstrated the role of the small regulatory RNAs (microRNAs) in cancer pathogenesis including MM. Preliminary studies identified microRNA-223 (miR-223) as aberrantly expressed in MM. MiR-223 has been implicated in the biology of other cancers and is known to target the microtubule regulator stathmin.
Aim: To test the hypothesis that miR-223 is functionally significant in MM.
Methods: The microRNA profiles of cells isolated from the pleural effusions of patients with MM, Adenocarcinoma and Benign Pleural Disease were determined using the Taqman® OpenArray® platform. The expression of miR-223 and stathmin mRNA was determined using real- time PCR in human and mouse MM cell lines and mesothelial cells. Stathmin protein levels were measured by western blot. MiR-223 levels were also measured in MM FFPE tumour samples and pericardium using real-time PCR. Cells were transfected with the miR-223 precursor to modulate the levels of miR-223 and the impact on stathmin expression, cell proliferation and migration were examined. The cells were also transfected with siRNA to inhibit stathmin before analysing cell migration.
Results: miR-223 was expressed significantly lower (p<0.01) in the cells isolated from MM and adenocarcinoma pleural effusions compared to patients with benign pleural disease. Mir-223 was also expressed significantly lower (p<0.01) in MM cells and in MM tumour samples compared to controls. In the same cell lines, stathmin mRNA and protein were significantly higher (p<0.05). Over-expressing miR-223 reduced stathmin mRNA and protein, confirming that miR-223 targets and regulates stathmin in MM. Over-expressing miR-223 did not affect cell proliferation but inhibited cell migration. Inhibiting stathmin also reduced cell migration.
Conclusions: miR-223 targets stathmin and is important in regulating MM cell migration in vitro.