Exosomal biomarkers for the early detection of hepatocellular carcinoma

Liver cancer is estimated to afflict 42,230 individuals and result in approximately 30,230 deaths in the US in 2021. The incidence rates for liver cancer have more than tripled since 1980, making it the 5th leading cause of cancerrelated deaths in the US. Approximately three-fourths of liver cancer cases are hepatocellular carcinoma (HCC). As for all cancers, detection of HCC at an earlier stage is critical to elicit the best chance of a cure. Early detection of HCC has significant potential to reduce mortality rates, due to the significant efficacy of local treatments for early-stage disease vs. systemic therapy for advanced-stage cancers. Although surveillance of patients at highrisk for HCC (e.g., those with chronic hepatitis or liver cirrhosis [LC]) is widely performed, the population of patients with HCC without viral etiologies is increasing because of insufficient screening for HCC. At present, alpha-fetoprotein (AFP) is the most widely used blood tumor marker; and hepatic ultrasound is a low-cost imaging method for surveillance of HCCs. However, both approaches have limited sensitivity and specificity for detecting early-stage HCC, highlighting the imperative need to develop robust biomarkers for the early detection of HCC. Accumulating evidence indicates that dysregulation of microRNAs (miRNAs) occurs in all human cancers, including HCC. As biomarkers, miRNAs are more resilient than mRNAs, and are frequently deregulated even in the earliest stages of neoplasia. Furthermore, the recent discovery that cancers actively excrete small extracellular vesicles, called exosomes, has brought additional enthusiasm to this burgeoning translational research topic. While exosomes are considered to reflect their respective cells-of-origin, their use in biomarker research has been hampered due to lack of standardized protocols for their isolation and purification, use of cell line-derived, but not patient-derived specimens for biomarker discovery; and lack of biomarker discovery in cancer-derived exosomes from matched tissues and plasma specimens. Furthermore, despite the perception that exosomal-miRNAs (exo-miRNAs) may be superior to circulating cell-free miRNAs (cf-miRNAs), no studies have undertaken an effort to directly compare these two types, to support or negate their superiority as disease biomarkers. In this proposal, we will address these concerns by undertaking the following Specific Aims. Aim 1: Discover candidate cf-miRNA and exo-miRNA biomarkers using small RNA-Seq in matched tissue and plasma from patients with early-stage HCC vs. controls. Aim 2: Develop a biomarker panel composed of cf-miRNAs and exo-miRNAs for the identification of patients with HCC in an independent cohort. Aim 3: Clinically validate the optimized panel of non-invasive plasma miRNA biomarkers in a large prospective cohort of patients with HCC. If successful, this proposal will provide molecular characterization of cell-free and exosomal miRNAs as liquid biopsy biomarkers, which may allow early-detection of HCC using a non-invasive, and inexpensive assay.