Supplementary Material for: Serum Exosomal Dicer Is a Useful Biomarker for Early Detection of Differentiated Gastric Adenocarcinoma

<b><i>Background and Aim:</i></b> A recent basic study identified that Dicer is contained in exosomes derived from cancer cells and plays crucial roles in microRNA maturation and cancer development. Based on this novel basic concept, we analyzed the usefulness of serum exosomal Dicer as a diagnostic biomarker for gastrointestinal cancers. <b><i>Methods:</i></b> Enrolled participants (691) were categorized into 3 groups: gastric cancer (GC) cohort, 183 patients (90 healthy controls (HCs) and 93 GC patients); esophageal cancer (EC) cohort, 115 patients (90 HCs and 25 EC patients); and colorectal cancer (CRC) cohort, 188 patients (92 HCs and 96 CRC patients) after age- and sex matching using the propensity score. The quality of isolated serum exosomes was validated with an electron microscope, particle size analyzer, and exosome marker, CD63. <b><i>Results:</i></b> Serum exosomal Dicer was significantly higher in the GC group than in the HC group (<i>p</i> = 0.004), whereas no significant differences were found in both EC and CRC cohorts. Serum exosomal Dicer was significantly higher in only differentiated gastric adenocarcinoma and not in the undifferentiated type. Moreover, serum exosomal Dicer showed no significant differences regardless of <i>Helicobacter pylori</i> (<i>H. pylori</i>) status. The biomarker panel combining serum exosomal Dicer with <i>H. pylori</i> status distinguished between HC and differentiated GC patients with an area under the curve (AUC) of 0.762. As for early-stage diagnosis, this combination distinguished between HC and stage I differentiated GC with an AUC = 0.758. <b><i>Conclusions:</i></b> Serum exosomal Dicer is a potential noninvasive diagnostic biomarker for early detection of differentiated gastric adenocarcinoma.