IRAK2, an IL1R/TLR Immune Mediator, Enhances Radiosensitivity Modulating Caspase 8/3-Mediated Apoptosis in Oral Squamous Cell Carcinoma.

Predicting and overcoming radioresistance are crucial in radiation oncology, including in managing oral squamous cell carcinoma (OSCC). First, we used RNA-sequence to compare expression profiles of parent OML1 and radioresistant OML1-R OSCC cells in order to select candidate genes responsible for radiation sensitivity. We identified IRAK2, a key immune mediator of the IL-1R/TLR signaling, as a potential target in investigating radiosensitivity. In four OSCC cell lines, we observed that intrinsically low IRAK2 expression demonstrated a radioresistant phenotype (i.e., OML1-R and SCC4), and vice versa (i.e., OML1 and SCC25). Next, we overexpressed IRAK2 in low IRAK2-expression OSCC cells and knocked it down in high IRAK2-expression cells to examine changes of irradiation response. After ionizing radiation (IR) exposure, IRAK2 overexpression enhanced the radiosensitivity of radioresistant cells and synergistically suppressed OSCC cell growth both and , and vice versa. We found that IRAK2 overexpression restored and enhanced radiosensitivity by enhancing IR-induced cell killing caspase-8/3-dependent apoptosis. OSCC patients with high IRAK2 expression had better post-irradiation local control than those with low expression (i.e., 87.4% 60.0% at five years, P = 0.055), showing that IRAK2 expression was associated with post-radiation recurrence. Multivariate analysis confirmed high IRAK2 expression as an independent predictor for local control (HR, 0.11; 95% CI, 0.016 - 0.760; P = 0.025). In conclusion, IRAK2 enhances radiosensitivity, modulating caspase 8/3-medicated apoptosis, potentially playing double roles as a predictive biomarker and a novel therapeutic target in OSCC.