Exosomal and non-exosomal miRNA expression levels in patients with HCV-related cirrhosis and liver cancer

Patients with HCV-related cirrhosis are at risk for liver cancer development. For these patients miRNAs may serve as preclinical markers, which expression levels are deregulated in cancer and which are stable to the damaging factors partly through complex formation with proteins or packaging into exosomes. In this research we have tried to identify what miRNA fraction in plasma – exosomal or not packed into exosomes (non-exosomal) – is stronger associated with primary liver cancer. The second question was whether saliva miRNA expression levels – both exosomal and non-exosomal – are associated with primary liver cancer. We evaluated exosomal and non-exosomal miRNAs – let-7a-5p, -16-5p, -18a-5p, -21-5p, -22-3p, -34a-5p, -103a-3p, -122-5p, -221-3p, -222-3p – in plasma and saliva of patients with HCV-related liver cirrhosis (n = 24), primary liver cancer (n = 24) and healthy volunteers (n = 21). Relative expression level was calculated with normalization of exosomal miRNA to exosomal miRNA-16-5p, non-exosomal miRNA to non-exosomal miRNA-16-5p and as a ratio of exosomal miRNA to non-exosomal miRNA. In this study, non-exosomal miRNAs (let-7a, miRNA-21-5p, -22-3p, -103a, -122-5p, -221-3p and 222-3p) normalized to non-exosomal miRNA-16-5p showed strong association with liver cancer in plasma. Three miRNAs, those with the mostly pronounced change of expression levels in plasma, – miRNA-21-5p, 122-5p, 221-3p – were detected in saliva. In contrast, exosomal miRNAs show stronger association with primary liver over non-exosomal miRNAs when working with saliva. Thus, depending on the examined biological material both miRNA fractions may serve as a valuable source for diagnostic and prognostic data.