B-383 Exosomal PRPSAP1 in Plasma Predicts Microvascular Invasion in Hepatocellular Carcinoma

Abstract Background Microvascular invasion (MVI), a critical predictor of postoperative tumor recurrence in hepatocellular carcinoma (HCC), is only detectable by histopathological examination of the surgical specimen. Prediction of MVI before surgery is of great significance to prognosis, especially by non-invasive means. Here, we report that exosome-derived mRNA in plasma can be promising biomarkers for MVI preoperatively. Methods Patients with initially suspected HCC who were undergoing hepatectomy were prospectively recruited with preoperative peripheral blood collection and followed up. Exosomal mRNA profiling was performed using RNA sequencing in the discovery cohort, and the edgeR package in R software was used to screen out significantly differential expression exosomal mRNAs between MVI and non-MVI groups. Multiplex droplet digital PCR (ddPCR) technology was utilized to verify filtered exosomal mRNAs in the validation cohort. Results A total of 131 HCC patients were enrolled with 37 in the discovery cohort and 94 in the validation cohort. RNA-sequencing data identified six candidate exosomal mRNAs (ZC3H3, RSAD2, PRPSAP1, HOXA2, CHPM4A and KCTD10) as potential predictors for MVI. In the validation cohort, expression levels of PRPSAP1 and HOXA2 were slightly higher and the expression level of CHMP4A was slightly lower in the MVI group than the non-MVI one, which were consistent with the discovery cohort though without statistically significant difference (P > 0.05). Further analysis between MVI number>5 and non-MVI patients validated that the expression level of exosomal PRPSAP1 was significantly higher in MVI number>5 patients (0.147 vs 0.070, P = 0.035). Altogether, exosomal PRPSAP1 in plasma was a promising biomarker predicting MVI for HCC patients. Conclusion We validated for the first time that high level expression of exosome-derived PRPSAP1 can preoperatively predict MVI, especially with the number >5, to improve prognosis.