| Summary |
Chronic inflammation plays a significant role in tumor promotion, migration and invasion. Using microarray analysis, we observed a profound increase in genes involved in pro-inflammatory pathways in epidermal growth factor receptor inhibitor (EGFRI)-treated head and neck squamous cell carcinoma (HNSCC) cell lines compared to their respective vehicle-treated cell lines. We hypothesized that the efficacy of EGFRIs may be offset by the pro-inflammatory response that these drugs produce in HNSCC tumor cells. We found that clinical EGFRIs such as erlotinib, cetuximab, lapatinib and panitumumab induced the secretion of pro-inflammatory cytokines such as IL-2, IL-4, IL-6, IL-8, GM-CSF, TNFα and IFNγ. Focusing on IL-6, we found that erlotinib induced a time-dependent increase in IL-6 mRNA and protein expression and exogenous IL-6 was able to protect HNSCC cells from erlotinib-induced cytotoxicity. Conversely, an IL-6 receptor antagonist tocilizumab, sensitized HNSCC cells to erlotinib in vitro and in vivo. Inhibitors of NFκB, p38 and JNK suppressed erlotinib-induced IL-6 expression, suggesting an important role of NFκB and MAPK pathways in IL-6 expression. Furthermore, knockdown of NADPH oxidase 4 (NOX4) suppressed erlotinib-induced pro-inflammatory cytokines expression. Taken together, these results suggest that clinical EGFRIs induce the expression of pro-inflammatory cytokines via NOX4. Therefore, the anti-tumor activity of EGFRIs may be partially reduced by activation of NOX4-mediated pro-inflammatory pathways in HNSCC. |
