Investigating the requirements of pro-inflammatory signaling in skin and head and neck SCC

Abstract

Head and neck squamous cell carcinoma (HNSCC) is a genetically heterogeneous cancer with poor prognosis. Current treatments for HNSCC are ineffective, and the resistance to therapies is often associated with a prominent inflammatory response highlighting the importance of devising ways to overcome it. Our laboratory has identified the Grainyhead-like 3 (GRHL3) gene as a potent tumor suppressor against HNSCC of both mice and humans. Loss of Grhl3 in mice induced HNSCC that appeared to be promoted by inflammation. In humans, we have introduced a paradigm shift in HNSCC pathogenesis through the identification of a miRNA-21-oncogenic network in patients, stratifying them into three subsets with distinct molecular signatures. This raised the hypotheses that inflammation may cooperate with the miR-21 oncogenic network to trigger human HNSCC and that different pro-inflammatory signaling might occur specifically in each HNSCC subset. In this study, we profiled pro-inflammatory cytokines/chemokines and their associated signaling pathways in 12 cell lines and xenografts by qPCR, Western Blot and immunohistochemistry, and correlated findings in cell lines with those in HNSCC mouse models as well as HNSCC patients. Our data determined that the expression of multiple cytokines and inflammatory proteins is dysregulated leading to the involvement of pivotal signaling such as the IL-1/NF-κB, the IL-6R/STAT3 and the TGF-β/SMAD pathways. We then modulated the pro-inflammatory signaling through different inhibitors, gene silencing and overexpression. The cell lines showed various sensitivities to the inhibitors of these inflammatory signaling, confirming the presence of distinct inflammatory profile in subsets of HNSCC. Interestingly, the antimicrobial peptides S100A8 and S100A9, which are involved in inflammation, were lost in all HNSCC cell lines in consistence with clinical data implicating them in the suppression of HNSCC. Thus, S100A8/A9 may function as tumor suppressors in HNSCC, and are currently being investigated to uncover the mechanisms that lead to their loss and to assess the downstream signaling of their epithelial RANGE and TRL4 receptors. Moreover, hotspot mutations were identified in common genes among the HNSCC cell lines, which showed different expression profiles of these mutant genes. Based on the pro-inflammatory signatures we have identified in human HNSCC lines, we are now able to stratify them into subsets with specific inflammatory pathways. Components of these pathways could serve as potential targets to overcome resistance in heterogeneous HNSCC. Inhibition of the miR-21 oncogenic network in combination with inhibitors of the inflammatory signaling while considering the mutational profiles may provide a better strategy to design new therapeutic applications in subtypes of HNSCC.