Salivary Exosomal miRNA-1307-5p Predicts Disease Aggressiveness and Poor Prognosis in Oral Squamous Cell Carcinoma Patients

Background: Salivary exosomal miRNAs as biomarkers facilitate repeated sampling, real-time disease monitoring and assessment of therapeutic response. This study identifies a single salivary exosomal miRNA prognosticator that will aid in improved patient outcome using a liquid biopsy approach. Method: Small RNA and transcriptome sequencing profiles of tumour tissues (n = 12) and salivary exosomes (n = 8) from oral cancer patients were compared to their non-cancerous counterparts. We validated these results using The Cancer Genome Atlas database and performing Real-time PCR on a large patient cohort (n = 19 tissue samples; n = 12 salivary exosomes). Potential target genes and the miRNA-mRNA networks and enriched biological pathways regulated by this microRNA were identified using computational tools. Results: Salivary exosomes (size: 30-50 nm) demonstrated a strong expression of CD47 and detectable expression of tetraspanins CD63, CD81 and CD9 by flow cytometry. miR-1307-5p was exclusively overexpressed in tissues and salivary exosomes of oral cancer patients compared to their non-cancerous counterparts. Enhanced expression of miR-1307-5p clinically correlated with poor patient survival, disease progression, aggressiveness and chemo-resistance. Transcriptome analysis suggested that miRNA-1307-5p could promote oral cancer progression by suppressing THOP1, EHF, RNF4, GET4 and RNF114. Conclusions: Salivary exosomal miRNA-1307-5p is a potential prognosticator for predicting poor survival and poor patient outcome in oral cancers.