Informing the Oral Squamous Cell Carcinoma Biomarker Search by Exudate Proteomics

Abstract

Oral cancer is the sixth most common cancer worldwide ahead of Hodgkin's lymphoma, leukemia, brain, stomach, or ovarian cancers, with about 41,000 Americans being diagnosed annually. More than 90% of oral cancers are oral Squamous cell carcinomas (OSCC). While the overall 5-year survival rate is about 60%, the survival rate when diagnosed early is higher than 80%. Currently the standard for diagnosis of OSCC is early visual detection of a suspicious oral lesion followed by scalpel biopsy with histology. However, the invasiveness, expense, and required expertise involved prevents consistent application on at risk individuals. Chapter 1 discusses the methods that are being investigated for sampling and discovering biomarkers of OSCC that address some of these limitations. Protein biomarkers contained in samples collected non-invasively and directly from at-risk oral premalignant lesions (OPML) would address current needs in a uniquely targeted fashion. Chapter 2 of this thesis describes work evaluating the potential of a novel method using commercial PerioPaper absorbent strips for the collection of oral lesion exudate fluid coupled with mass spectrometry based proteomics for OSCC biomarker discovery. This research focuses on demonstrating the feasibility of using oral lesion exudates in proteomic research, exploring the proteome of exudate samples, discriminating between exudates collected from clinically different sources, with supplemental table 1 showing which proteins distinguish healthy and OPML sources. Furthermore, to ensure that the best possible marker candidates are selected given clinical sample availability, multiple methods were explored enable and improve quantitative proteomic analysis of exudates in chapter 3 (Identified proteins in supplemental files 2 and 3). Our label-free quantitative proteomics strategy analyzed paired control and OPML exudates (figure 8), identifying differentially abundant proteins between sample types. Next, we selected several [exudate] differentially abundant proteins for testing in while saliva, comparing their relative abundance levels in healthy, OPML and oral Squamous cell carcinoma (OSCC) subjects. Two proteins, CK10 and A1AT, showed differences in saliva. Our results provide a demonstration of the value of tissue exudate analysis for guiding salivary biomarker discovery in oral cancer, as well as providing promising biomarker candidates for future evaluation.