Liquid Biopsies for Precision Medicine in Colorectal and Head and Neck Cancers: Saliva and Blood Biomarkers

Abstract

Liquid biopsies have emerged as an innovative tool in precision oncology representing a valuable complement to traditional tumor biopsy for detecting, characterizing, and monitoring cancer. Liquid biopsies comprise the non-invasive analysis of tumor-derived material including circulating tumor cells, cellfree nucleic acids, extracellular vesicles, and tumor-derived platelets in different body fluids, such as blood and saliva. Scientific evidence has highlighted the potential value of saliva analyses in the oncology field. Advances in saliva-omics demonstrated the feasibility to detect different tumor biomarkers in saliva providing a non-invasive strategy to assess cancer diagnosis, progression, and therapeutic efficacy. The objective of this doctoral thesis was to identify biomarkers with clinical utility in liquid biopsies of saliva and plasma from colorectal and head and neck cancer patients. In colorectal cancer, we performed a pioneer characterization of salivary microRNAs and identified potential diagnostic biomarkers. In head and neck cancer, different molecular approaches were carried out to improve its non-invasive characterization, including characterization of salivary cell-free DNA, assessment of somatic mutations in plasma and saliva, and profiling of salivary DNA methylation.