miR-223 potentially targets SWI/SNF complex protein SMARCD1 in atypical proliferative serous tumor and high-grade ovarian serous carcinoma

Summary Ovarian cancer is the fifth most common cancer in women worldwide and has the highest mortality amongst gynecological cancers. miRNAs are a class of non-coding RNAs, approximately 22 nt long, that negatively regulate gene expression and have roles in cell growth, differentiation, metabolism, apoptosis and tumorigenesis. Dysregulated miRNA-223 expression has been implicated in a wide range of cancer subtypes. SMARCD1 is an integral protein component of the SWI/SNF complex, which remodels chromatin, and which has important roles in transcriptional control, DNA replication, recombination and repair. In this study, we examined whether the expression levels of miR-223 and SMARCD1 are altered in ovarian serous neoplasia and whether miR-223 functionally regulates the gene and protein expression of SMARCD1 in vivo, as has been predicted by in silico methods. Benign, atypical proliferative serous tumors (borderline) and malignant serous tumors (n = 144) were laser-capture microdissected, and relative expression levels of miR-223 and SMARCD1 were quantified by RT-PCR. Ovarian cancer cell line OC316 was reverse transfected with a miR-223 mimic, and relative expression levels of miR-223 and SMARCD1 were quantified by reverse-transcription polymerase chain reaction; protein expression of SMARCD1 was evaluated by Western blot. miR-223 expression was up-regulated in high-grade ovarian serous carcinoma samples (median RQ=4.8881, P = .0045), whilst SMARCD1 was down-regulated (median RQ=0.5107, P = .0492). In OC316 cells transfected with a miR-223 mimic, SMARCD1 gene expression was down-regulated 3-fold ( P = .001), and SMARCD1 protein expression was down-regulated 2-fold ( P = .002). These results suggest a regulatory role for miR-223 in ovarian serous neoplasia, linking it with SMARCD1.