Resistance to apoptosis is a hallmark of
cancer and deregulation of apoptosis often leads to chemoresistance. Therefore, new approaches to target apoptosis-resistant
cancer cells are crucial for the development of directed
cancer therapies. In the present study, we investigated the effect of cell cycle regulators on
interferon (IFN)-induced necroptosis as an alternative cell death mechanism to overcome apoptosis resistance. Here, we report a novel combination treatment of IFNs with cell cycle arrest-inducing compounds that induce necroptosis in apoptosis-resistant
cancer cells and elucidate the underlying molecular mechanisms. Combination treatment of IFNs (i.e. IFNβ) with inhibitors of the cell cycle (e.g.
vinorelbine (VNR),
nocodazole (Noc),
polo-like kinase-1 (Plk-1) inhibitor
BI 6727) co-operate to induce necroptotic cell death upon
caspase inactivation. The mode of cell death was confirmed by pharmacological inhibition and
siRNA-mediated downregulation of the key necroptotic factors
receptor-interacting protein (RIP)
kinase 3 (RIP3) and mixed-lineage
kinase-like (MLKL) in various cell lines. Mechanistically, we show that necroptosis upon VNR/IFNβ/
zVAD.fmk treatment is RIP1-independent but relies on IFNβ-induced gene expression of
Z-DNA-
binding protein 1 (ZBP1) as shown by quantitative RT-PCR and genetic knockdown experiments. Interestingly, we find that RIP3 is phosphorylated in response to compounds that trigger mitotic arrest, even in the absence of IFNβ signaling and necroptosis induction. Together, the identification of a novel combination treatment that triggers necroptosis has implications for the development of
molecular-targeted therapies to circumvent apoptosis resistance and point to an underestimated role of cell cycle regulation in cell death signaling.