Novel smac mimetic ASTX660 (Tolinapant) and TNF-alpha synergistically induce necroptosis in bladder cancer cells in vitro upon apoptosis inhibition

Apoptosis inhibition often leads to resistance to chemotherapeutics in bladder cancer (BC), resulting in poor prognosis of patients. Accumulating evidence suggests that induction of necroptosis, another type of programmed cell death, can be applied as an alternative strategy to kill apoptosis-insensitive BC cells. In this study, we showed that a novel Smac mimetic, ASTX660, also known as Tolinapant, can induce necroptosis in BC cells when apoptosis is inhibited. This is achieved by turning tumour necrosis factor (TNF)-alpha into a cytotoxic signal; ASTX660 then acts synergistically with TNF-alpha to induce necroptosis in BC cells. Mechanistic investigation showed that ASTX660 promoted the formation of the necrosome complex. Genetic or pharmacological inhibition of RIP1, RIP3, or MLKL, which are components of necrosome complex, provided protection against cell death induced by ASTX660 alone or ASTX660/TNF-alpha upon caspase inhibition. In addition, TNF-alpha/TNFR1 signalling and IRF1 are essential for the necroptosis induced by ASTX660 after the caspases are blocked. Our study highlights that ASTX660 can overcome the limitation of apoptosis induction via triggering necroptosis in BC cells. Therefore, our findings may provide some important clues for the design of a novel treatment strategy for BC. (C) 2022 Published by Elsevier Inc.