Abstract PO-039: Discovery and validation of methylated DNA markers of human papillomavirus associated oropharyngeal squamous cell carcinoma
Authors: Gochanour Benjamin R. , Routman David M. , Bartemes Kathleen R. , Taylor William R. , Mahoney Douglas W. , Graham Rondell P. , Cao Xiaoming , Berger Calise K. , Then Sara S. , Doering Karen A. , Burger Kelli N. , Foote Patrick H. , Kisiel John B. , Van Abel Kathryn M. 
Published: September 2023

Abstract
Background: Reliable non-invasive biomarkers for human papillomavirus (HPV) associated oropharyngeal squamous cell carcinoma (OPX) are lacking. We performed a discovery and validation study of methylated DNA markers (MDMs) for detection of OPX. In addition, we sought to evaluate the MDM profiles in saliva gargle samples from normal controls (nSAL). Methods: Formalin fixed paraffin embedded OPX and gender-balanced normal oropharyngeal tissue (NOP) were pathologically reviewed and punched for DNA extraction and sequenced using reduced representation bisulfite sequencing (RRBS). A tiling algorithm was used to define candidate MDMs. Highest ranked (e.g., area under the receiver operating characteristic curve (AUC), fold-change, p-value) candidate MDMs were validated by qMSP in independent OPX and NOP samples. nSAL DNA was used to assess MDM background signal. Discrimination between OPX tissue, NOP, and nSAL was assessed using AUC with corresponding 95% confidence intervals. HPV was confirmed with p16 staining or DNA in situ hybridization. Results: RRBS discovery assessed 18 OPX, 18 NOP, and 18 normal WBC samples. 234 MDM candidates from approximately 3 × 106 CpGs at &gt;10X coverage were identified. 36 MDMs were selected for validation in independent patient samples which included 32 OPX, 36 NOP, and 35 nSAL specimens. OPX patients were older (median 51; IQR 45-54 years) than NOP patients (median 29; IQR 24-42). 69 and 61% of OPX and NOP patients were female, respectively. The majority of OPX patients were Stage I (n=27, 84%). We observed excellent discrimination between OPX and NOP in the validation set; the median AUC across 36 MDMs was 0.90 (IQR 0.87-0.95). The 10 highest performing markers (PARP15, EPDR1, SHROOM1, EMBP1.rs, IFFO1, MAX.chr19.118, ZNF763, ITGB4, FAM19A2, and MT1IP) exhibited AUCs ranging from 0.95-0.99. Strong discrimination was also observed between OPX and nSAL (Median AUC=0.97; IQR=0.93-0.99). All 10 of the highest-performing markers in tissue exhibited AUCs of at least 0.97 for discriminating OPX versus nSAL. Median fold change between NOP and nSAL across all MDMs was 1.9 (IQR 1.4-3.8), demonstrating low background signal in nSAL. Conclusions: We found strong discrimination in a panel of 36 MDMs between OPX case and control tissue as well as between OPX case tissue and normal saliva. The low background signal observed in normal saliva makes this media a strong candidate for non-invasive detection of OPX. Further studies are in development to assess the utility of measuring these MDMs in both case and control saliva and blood for detecting OPX non-invasively.
Citation Format: Benjamin R. Gochanour, David M. Routman, Kathleen R. Bartemes, William R. Taylor, Douglas W. Mahoney, Rondell P. Graham, Xiaoming Cao, Calise K. Berger, Sara S. Then, Karen A. Doering, Kelli N. Burger, Patrick H. Foote, John B. Kisiel, Kathryn M. Van Abel. Discovery and validation of methylated DNA markers of human papillomavirus associated oropharyngeal squamous cell carcinoma [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-039.