Expression of Inflammasome-Associated Proteins in Human Oropharyngeal Squamous Cell Carcinoma

Inflammasomes, large protein complexes typically consisting of a Nod-like receptor (NLR), adapter protein apoptosis-associated speck-like protein containing CARD (ASC) and caspase-1, are postulated to be activated in response to danger signals arising from tumors. Inflammasomes are thought to have critical but contrasting roles through facilitating antitumor immunity and inducing oncogenic factors. However, the role and function of inflammasomes in oropharyngeal carcinoma remain unclear. We analyzed nine specimens of oropharyngeal squamous cell carcinoma (SCC) and determined the expression of NLRP3, ASC, interleukin (IL)-1β, IL-18 and caspase-1 in the specimens with and without human papilloma virus (HPV) infection using immunohistochemistry, and analyzed the correlations between the altered expression of these proteins and clinicopathological factors of oropharyngeal SCC. We found strong expression of NLRP3, ASC, IL-1β, IL-18 and caspase-1 in human oropharyngeal SCC and weak or no expression of these proteins in normal tonsils. Furthermore, the distribution of mindbomb E3 ubiquitin protein ligase 1 and inflammasome-associated proteins in oropharyngeal SCC was not significantly different; there was no correlation between the expression of inflammasome-associated proteins and HPV infection. These findings suggest that inflammasomes in oropharyngeal SCC play a key role through facilitating antitumor immunity and the possibility of new roles for inflammasomes in the oropharynx.