Improved Discrimination of Patients with Breast Cancer from Healthy Controls Using Paper-Based microRNA Expression Profiling of Plasma, Following Precipitation

To the Editor: Breast cancer is a frequently diagnosed solid tumor in women worldwide (1). MicroRNAs (miRNAs), small noncoding RNAs that regulate protein expression, are potential biomarkers in the diagnosis, prognosis, and prediction of response to treatment in breast cancer (2). We recently reported a paper-based method to extract miRNAs from plasma and circulating tumor cells (3). Here, we applied this method to plasma of patients with breast cancer and age- and gender-matched healthy controls, after treating the plasma with a commercial exosome isolation kit employing a nonspecific precipitation step; we compared the miRNA expression profiles from the plasma with and without the use of the precipitation method. After informed consent and institutional approval, we obtained peripheral blood samples from 9 patients with breast cancer and 9 healthy controls. Plasma was isolated by centrifugation at 3000 g for 10 min and stored at −80 °C. All plasma samples were visually inspected to exclude any discernible hemolysis. Then, 60 μL of Total Exosome Isolation reagent …