AIMS:

Most chemotherapeutic agents exploit apoptotic signaling to trigger cancer cell death, which frequently results in drug resistance. Necroptosis, a non-apoptotic form of regulated cell death, offers an alternative strategy to eradicate apoptosis-resistant cancer cells. We previously reported a natural necroptosis inducer 2-methoxy-6-acetyl-7-methyljuglone (MAM) in A549 lung cancer cells. The current study is designed to investigate the detailed necroptotic signaling and its cytotoxicity on drug-resistant cancer cells. Furthermore, in vivo anti-cancer effects were also evaluated in nude mice model.

RESULTS:

MAM directly targets receptor-interacting protein 1 (RIP1) kinase in A549 and H1299 cells, which is responsible for reactive oxygen species (ROS, mainly hydrogen peroxide) generation. A positive feedback loop between calcium (Ca2+) and c-Jun N-terminal protein kinase (JNK) occurred following ROS generation, leading to lysosomal membrane permeabilization and mitochondrial dysfunction. MAM showed similar cytotoxic potency towards A549/Cis cells by inducing necroptosis as confirmed by the protective effect of 7-Cl-O-Nec-1 (Nec-1s) and by the morphological characteristics obtained via transmission electron microscopy. Interestingly, TNFα was not involved in this process. Intraperitoneal injection of MAM significantly suppressed tumor growth in A549 tumor xenograft without significant body weight loss and multi-organ toxicities. Innovation and Conclusion: Our findings demonstrate that MAM induces necroptosis in A549 and H1299 lung cancer cells by targeting RIP1 kinase and ROS in a TNFα-independent manner. MAM kills A549/Cis cells with similar potency through induction of necroptosis. MAM shows anti-cancer effect in animal model. The present study raises the therapeutic possibility and strategy to combat cancer by induction of necroptosis.