Inhibiting WEE1 and IKK-RELA Crosstalk Overcomes TNF alpha Resistance in Head and Neck Cancers

TNF alpha is a key mediator of immune and radiotherapy-induced cytotoxicity, but many cancers, including head and neck squamous cell carcinomas (HNSCC), display TNF resistance due to activation of the canonical IKK-NF-kappa B/RELA pro-survival pathway. However, toxicities associated with direct targeting of the canonical pathway point to the need to identify mechanism(s) contributing to TNF alpha resistance and synthetic lethal targets to overcome such resistance in cancer cells. Here, RNAi screening for modulators of TNF alpha-NF-kappa B reporter activity and cell survival unexpectedly implicated the WEE1 and CDC2 G(2)-M checkpoint kinases. The IKK alpha/beta-RELA and WEE1-CDC2 signaling pathways are activated by TNF alpha and form a complex in cell lines derived from both human papillomavirus (-) and (+) subtypes of HNSCC. WEE1 inhibitor AZD1775 reduced IKK/RELA phosphorylation and the expression of NF-kappa B-dependent pro survival proteins Cyclin D1 and BCL2. Combination of TNF alpha and AZD1775 enhanced caspase-mediated apoptosis in vitro, and combination treatment with radiotherapy and AZD1775 potentiated inhibition of HNSCC tumor xenograft growth in vivo, which could be significantly attenuated by TNF alpha depletion. These data offer new insight into the interplay between NF-kappa B signaling and WEE1mediated regulation of the G2-M cell-cycle checkpoint in HNSCC.