Abstract B09: Identification of salivary exosomes derived miRNAs as potential early diagnostic markers in oral cancer patients: A liquid biopsy approach
Authors: Patel Shanaya , Patel Aditi , Mathur Dhanvi , Tanavde Vivek 
Published: June 2020

Abstract
Oral squamous cell carcinoma (OSCC) is one of the most prevalent forms of cancer globally. Late-stage diagnosis is one of the major confounders for poor prognosis, as there are no disease-specific biomarkers available for early risk prediction. Some of the major limitations of invasive tissue biopsies are inadequacy of tissue, difficulty in accessing deep sites, pain, and potential risk for the patient. Therefore, it is important to identify sensitive and specific circulatory biomarkers using noninvasive biopsy techniques. Some studies have investigated microRNA (miRNAs) expression in saliva as potential biomarkers; however, these studies suffer from extensive RNA degradation due to the presence of RNA-degrading enzymes in saliva. Since miRNAs associated with exosomes are known to be protected from enzymatic degradation, we evaluated whether salivary exosomes from OSCC patients were enriched with specific subsets of miRNAs that would be useful in the early diagnosis of OSCC. In this study, we performed miRNA and mRNA sequencing (Illumina) in leukoplakia and OSCC patient-derived salivary exosomes and matched tumors (n=20) compared to controls. The combination of miRNA and mRNA expression profiles from the same sample allowed us to significantly reduce the false positives in predicted miRNA targets. Potential target prediction, Gene Ontology (GO) annotation, and pathway enrichment analysis were conducted to explore the functional and biologic significance of the identified miRNA and gene networks. Subset of miRNAs and genes that were enriched in both tumor and exosomes were further evaluated using real-time quantitative PCR (qPCR) analysis. Our results demonstrated that exosomes from patients’ saliva have a distinct pattern of miRNA expression compared to healthy controls. miRNA profiles of salivary exosomes were similar to tumor profiles of both leukoplakia and oral cancer tumor samples. 26 miRNAs were expressed exclusively in leukoplakia (16 miRs) and OSCC patient population (10 miRs), but not in controls. We also identified miRNA regulated gene networks that were differentially expressed in various stages of oral cancer compared to controls with good discrimination power and were involved in signaling pathways such as PI3K/Akt, MAPK, and WNT. One of the noteworthy findings from this study was identification of 5 tumor-suppressor miRNAs that were exclusively expressed in healthy controls and were absent in both leukoplakia and oral cancer patients. Thus, this study shows that miRNAs exclusively enriched in exosomes of leukoplakia and OSCC patients could be exploited as potential noninvasive biomarkers for OSCC diagnosis. This study will also aid in gaining further insights on miRNA-mediated gene networks responsible for transforming epithelial phenotype to oral carcinoma.
Citation Format: Shanaya Patel, Aditi Patel, Dhanvi Mathur, Vivek Tanavde. Identification of salivary exosomes derived miRNAs as potential early diagnostic markers in oral cancer patients: A liquid biopsy approach [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B09.