Potential imaging targets in primary head and neck squamous cell carcinoma and lymph node metastases☆

Purpose: To investigate glycoprotein nonmetastatic melanoma protein B (GPNMB) and vascular endothelial growth factor (VEGF) as potential fluorescent imaging markers by comparing their protein expression to epidermal growth factor receptor (EGFR). Materials and methods: Thirty-eight paired samples of untreated head and neck squamous cell carcinoma (HNSCC) primary tumours (PT) and corresponding synchronous lymph node metastases (LNM) were selected. After immunohistochemical staining, expression was assessed and compared by the percentage of positive tumour cells. Data were analysed using the Mann-Whitney test, effect sizes (ESr) and Spearman's correlation coefficient (r). Results: GPNMB expression was observed in 100 % of PT, and median 80 % (range 5-100 %) of tumour cells, VEGF in 92 % and 60 % (0-100 %), EGFR in 87 % and 60 % (0-100 %) respectively. In corresponding LNM, GPNMB expression was observed in 100 % of LNM and median 90 % (20-100 %) of tumour cells, VEGF in 87 % and 65 % (0-100 %), and EGFR in 84 % and 35 % (0-100 %). A positive correlation was found between expression in PT and LNM for GPNMB (r = 0.548) and EGFR (r = 0.618) (p < 0.001), but not for VEGF (r = -0.020; p = 0.905). GPNMB expression was present in a higher percentage of tumour cells compared to EGFR in PT (p = 0.015, ESr = -0.320) and in LNM (p <0.001, ESr = -0.478), while VEGF was not (p = 1.00, ESr = -0.109 and - 0.152, respectively). Conclusion: GPNMB expression is higher than EGFR in untreated HNSCC PT and corresponding LNM, while VEGF expression is comparable to EGFR. GPNMB is a promising target for fluorescent imaging in HNSCC.