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

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 < .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.

Abstract 6261: Comparison of glycoprotein nonmetastatic melanoma protein b, epidermal growth factor receptor and vascular endothelial growth factor expression in head and neck squamous cell carcinoma, and untreated and residual lymph node metastases

Objective: To evaluate expression of the potential molecular imaging targets glycoprotein nonmetastatic melanoma protein B (GPNMB) and vascular endothelial growth factor (VEGF) in comparison to classical epidermal growth factor receptor (EGFR) in previously untreated head and neck cancer primary tumors and corresponding lymph node metastases, and in lymph node metastases after initial (chemo)radiotherapy. Methods: Primary tumors and lymph node metastases of 38 patients who underwent primary resection of head and neck squamous cell carcinoma (HNSCC) were selected. In addition, lymph node metastases from salvage surgery after (chemo)radiotherapy from 22 patients with HNSCC were selected. Immunohistochemical staining for EGFR, VEGF and GPNMB was performed, after which protein expression was scored using H-scores (percentage of positive tumor cells multiplied by staining intensity ranging from 0 to 2). Primary tumors and lymph node metastases with an H-score ≥5 were considered positive, after which sensitivity rates were calculated. Groups were compared using the Mann-Whitney U test for non-parametric data with post-hoc Bonferroni corrections. Results: In untreated primary HNSCC the sensitivity was 86.8% for EGFR (median H-score 60), 92.1% for VEGF (median 60), and 100% for GPNMB (median 100). In previously untreated lymph node metastases the sensitivity was 81.6% for EGFR (median 30), 86.8% for VEGF (median 65), and 100% for GPNMB (median 118). In lymph node metastases after initial (chemo)radiotherapy, sensitivity was 86.4% for EGFR (median 95) and 100% for GPMB (median 100). VEGF sensitivity could not reliably be evaluated in these lymph nodes due to nonspecific staining in all tissue slides. GPNMB expression was significantly higher compared to EGFR in untreated primary HNSCC (p = .009 and p < .001, respectively) and lymph node metastases (p < .001 for both). Conclusion: GPNMB shows better tumor-specific receptor expression in both sensitivity and H-scores compared to EGFR and VEGF in immunohistochemistry. VEGF performed comparable to EGFR in untreated HNSCC and lymph node metastases. GPNMB could therefore be a new potential imaging target based on these immunohistochemical results.

Citation Format: Jeroen E. van Schaik, Bert van der Vegt, Saskia H. Hanemaaijer, Gyorgy B. Halmos, Max J. Witjes, Bernard F.A.M. van der Laan, Rudolf S. Fehrmann, Sjoukje F. Oosting, Boudewijn E. Plaat. Comparison of glycoprotein nonmetastatic melanoma protein b, epidermal growth factor receptor and vascular endothelial growth factor expression in head and neck squamous cell carcinoma, and untreated and residual lymph node metastases [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 6261.