Clinical significance of miR-140-5p and miR-193b expression in patients with breast cancer and relationship to IGFBP5

The functional role of IGFBP5 in breast cancer is complicated. Experimental andbioinformatics studies have shown that IGFBP5 is targeted by miR-140-5p and miR-193b,although this has not yet been proven in clinical samples. The aim of this study wasto evaluate the expression of miR-140-5p and miR-193b in breast cancer and adjacentnormal tissue and assess its correlation with IGFBP5 and the clinicopathologicalcharacteristics of the tumors. IGFBP5 protein expression was analyzedimmunohistochemically and IGFBP5, miR-140 and miR-193b mRNA expression levels wereanalyzed with real-time RT-PCR. Tumor tissue had higher miR-140-5p expression thanadjacent normal tissue (p = 0.015). Samples with no immunohistochemical staining forIGFBP5 showed increased miR-140-5p expression (p = 0.009). miR-140-5p expression waselevated in invasive ductal carcinomas (p = 0.002), whereas basal-like tumors haddecreased expression of miR-140-5p compared to other tumors (p = 0.008). Lymphnode-positive samples showed an approximately 13-fold increase in miR-140-5pexpression compared to lymph node-negative tissue (p = 0.049). These findings suggestthat miR-140-5p, but not miR-193b, could be an important determinant of IGFBP5expression and clinical phenotype in breast cancer patients. Further studies areneeded to clarify the expressional regulation of IGFBP5 by miR-140-5p.