Objectives: Calprotectin (S100A8/A9) appears to function as a tumor suppressor in head and neck squamous cell carcinoma (HNSCC) and expression in the carcinoma cells and patient survival rates are directly related. We seek to characterize the suppressive role of calprotectin in HNSCC. Aims: (1) Investigate changes in S100A8/A9 expression as oral carcinogenesis progresses and (2) determine whether intracellular calprotectin can regulate epidermal growth factor receptor (EGFR), a negative prognostic factor, in HNSCC. Materials and methods: Using immunohistochemistry (IHC), S100A8/A9 was analyzed in HNSCC specimens (N = 46), including well-differentiated (WD, N = 19), moderately-differentiated (MD, N = 14), poorly-differentiated (PD, N = 5) and non-keratinizing/basaloid (NK/BAS, N = 8), and premalignant epithelial dysplasias (PED, N = 16). Similarly, EGFR was analyzed in HNSCCs (N = 21). To determine whether calprotectin and EGFR expression are mechanistically linked, TR146 HNSCC cells that are S100A8/A9-expressing or silenced (shRNA) were compared for EGFR levels and caspase-3/7 activity using western blotting and immunofluorescence microscopy. Results: In normal oral mucosal epithelium, S100A8/A9 stained strongly in the cytoplasm and nucleus of suprabasal cells; basal cells were consistently S100A8/A9 negative. In PED and HNSCC, S100A8/A9 expression was lower than in adjacent normal epithelial tissues (NAT) and declined progressively in WD, MD, PD and NK/BAS HNSCCs. S100A8/A9 and EGFR levels appeared inversely related, which was simulated in vitro when S100A8/A9 was silenced in TR146 cells. Silencing S100A8/A9 significantly reduced caspase-3/7 activity, whereas EGFR levels increased. Conclusions: In HNSCC, S100A8/A9 is directly associated with cellular differentiation and appears to promote caspase-3/7-mediated cleavage of EGFR, which could explain why patients with S100A8/A9-high tumors survive longer.
|Original language||English (US)|
|Number of pages||10|
|State||Published - Aug 2019|
Bibliographical noteFunding Information:
The project was supported by NIH/NIDCR R01DE021206 to MCH and R90DE023058 to PPA. We thank Rachel Isaksson Vogel, PhD for assistance with our statistical analyses. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIDCR or the NIH.
- Epithelial differentiation
- Head and neck squamous cell carcinoma
- P16+ squamous cell carcinoma
- Premalignant epithelial dysplasia