Downregulation of EGFR in hypoxic, diffusion-limited areas of squamous cell carcinomas of the head and neck

BACKGROUND: The receptor for the epidermal growth factor (EGFR) is widely considered to be one of the central drivers of oncogenesis in squamous cell carcinomas of the head and neck region (HNSCC). Inhibition of EGFR using monoclonal antibodies is established both in the curative and the palliative setting in this disease. HNSCCs are known to contain abundant hypoxic tissue areas and hypoxia has been shown to be involved in the (down)regulation of EGFR membrane expression. METHODS: A novel method for multiplex immunofluorescence and single-cell segmentation (via DAPI-stained nuclei) was established, to study the expression of EGFR, the endogenous hypoxia marker CA IX, and intratumoural diffusion distances from microvessels (using CD34 staining) in 58 human HNSCCs and 9 normal/cancer adjacent tissues. RESULTS: EGFR was found to be significantly downregulated with increasing distance from tumour microvessels, whereas the opposite was true for CA IX. Larger diffusion-limited areas were correlated with higher expression of CA IX. CONCLUSIONS: The hypoxic tumour microenvironment may have a major role in mediating resistance against anti-EGFR strategies by downregulating EGFR molecules on tumour cells.