Abstract 6260: Identification of molecular imaging targets specific for head and neck squamous cell carcinoma by transcriptional adaptation to copy number alterations profiling: Digital data translated to protein expression
Authors: van Schaik Jeroen E. , van der Vegt Bert , van der Laan Bernard F.A.M. , Witjes Max J.H. , Oosting Sjoukje F. , Fehrmann Rudolf S. , Plaat Boudewijn E. 
Published: June 2022

Abstract
Objective: Head and neck squamous cell carcinoma (HNSCC) can intraoperatively be visualized by fluorescence molecular imaging (FMI) using fluorophores conjugated to HNSCC specific antibodies. Currently, the epidermal growth factor receptor (EGFR) is used as a target. Targets more specific for HNSCC would reduce background signal, resulting in a higher tumor to background ratio. We aimed to identify new potential targets for FMI in HNSCC.
Methods: Publicly available transcriptomic data were collected. A biostatistical method known as Transcriptional Adaptation to Copy Number Alterations (TACNA) profiling was applied, which captures the downstream effects of copy number alterations (CNAs) on mRNA levels, which we used to predict the overexpression on the protein level. By comparing gene expression profiles of HNSCC and normal oral mucosa, genes overexpressed explicitly in HNSCC were identified. Potential targets were selected based on the degree of overexpression, plasma membrane expression, and cross expression in other tissues in the head and neck region. Next, the expression of potential targets of TACNA results on mRNA level were validated on the protein level and compared to EGFR expression using immunohistochemistry (IHC). Subsequently, paired biopsies of HNSCC, adjacent suspicious mucosa, and healthy mucosa of the same patients were stained. Receptor expression was evaluated using H-scores (i.e., percentage of positive cells combined with staining intensity).
Results: TACNA profiling was applied on 111 samples of healthy oral mucosa and 410 HNSCC comparing expression levels of 19,635 genes. The newly identified membrane-bound targets were glucose transporter 1 (GLUT-1), placental cadherin (P-cadherin), and monocarboxylate transporter 1 (MCT-1). The three targets were evaluated by IHC in a total of 31 patients, of which 8 had oropharyngeal, 7 hypopharyngeal, and 16 laryngeal carcinomas. GLUT-1 had a median H-score of 175, P-cadherin 140, and MCT-1 40. GLUT-1 and P-cadherin were significantly higher compared to EGFR, with a median H-score of 90 (p &lt; .001). GLUT-1 receptor expression was also seen on erythrocytes, while P-cadherin expression was seen in the basal layer of normal epithelium. This can complicate its use in FMI.
Conclusion: TACNA profiling results were successfully validated in immunohistochemistry as a first step in the search for new specific FMI targets in HNSCC. GLUT-1 and P-cadherin show promising results with significantly higher receptor expression than EGFR.
Citation Format: Jeroen E. van Schaik, Bert van der Vegt, Bernard F.A.M. van der Laan, Max J.H. Witjes, Sjoukje F. Oosting, Rudolf S. Fehrmann, Boudewijn E. Plaat. Identification of molecular imaging targets specific for head and neck squamous cell carcinoma by transcriptional adaptation to copy number alterations profiling: Digital data translated to protein expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6260.