Inhibitors specifically targeting the 1-phosphatidylinositol 3-phosphate 5-kinase (PIKFYVE) disrupt lysosome homeostasis, thereby selectively terminating autophagy-dependent human cancer cells in vivo as well as in vitro without harming the viability of nonmalignant cells. To elucidate the mechanism by which PIKFYVE inhibition induces cell death, autophagy-dependent melanoma cells were compared with normal foreskin fibroblasts. RNA sequence profiling suggested that PIKFYVE inhibitors upregulated an endoplasmic reticulum (ER) stress response involving interleukin-24 (IL24; also known as MDA7) selectively in melanoma cells. Subsequent biochemical and genetic analyses confirmed these results and extended them to tumor xenografts in which tumor formation and expansion were inhibited. IL24 expression was upregulated by the DDIT3/CHOP/CEBPz transcription factor, a component of the PERK-dependent ER-stress response. Ectopic expression of IL24-induced cell death in melanoma cells, but not in foreskin fibroblasts, whereas ablation of the IL24 gene in melanoma cells prevented death. IL24 upregulation was triggered specifically by PIKFYVE inhibition. Thus, unlike thapsigargin and tunicamycin, which induce ER-stress indiscriminately, PIKFYVE inhibitors selectively terminated PIKFYVE-sensitive melanoma by inducing IL24-dependent ER-stress. Moreover, induction of cell death by a PIKFYVE inhibitor together with ectopic expression of IL24 protein was cumulative, thereby confirming the therapeutic potential of PIKFYVE inhibitors in the treatment of melanoma.

中文翻译：

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PIKFYVE 抑制剂触发自噬依赖性黑色素瘤的白细胞介素 24 依赖性细胞死亡

专门针对 1-磷脂酰肌醇 3-磷酸 5-激酶 (PIKFYVE) 的抑制剂会破坏溶酶体稳态，从而在体内和体外选择性地终止自噬依赖性人类癌细胞，而不损害非恶性细胞的活力。为了阐明 PIKFYVE 抑制诱导细胞死亡的机制，将自噬依赖性黑色素瘤细胞与正常包皮成纤维细胞进行了比较。 RNA 序列分析表明，PIKFYVE 抑制剂选择性上调黑色素瘤细胞中涉及白细胞介素 24（IL24；也称为 MDA7）的内质网 (ER) 应激反应。随后的生化和遗传分析证实了这些结果，并将其扩展到肿瘤异种移植物中，其中肿瘤的形成和扩张受到抑制。IL24表达被 DDIT3/CHOP/CEBPz 转录因子上调，DDIT3/CHOP/CEBPz 转录因子是 PERK 依赖性内质网应激反应的一个组成部分。 IL24 的异位表达在黑色素瘤细胞中诱导细胞死亡，但在包皮成纤维细胞中则不然，而黑色素瘤细胞中IL24基因的消除则可防止细胞死亡。IL24上调是由 PIKFYVE 抑制特异性触发的。因此，与不加区别地诱导 ER 应激的毒胡萝卜素和衣霉素不同，PIKFYVE 抑制剂通过诱导 IL24 依赖性 ER 应激来选择性终止 PIKFYVE 敏感的黑色素瘤。此外，PIKFYVE抑制剂诱导的细胞死亡以及IL24蛋白的异位表达是累积的，从而证实了PIKFYVE抑制剂在黑色素瘤治疗中的治疗潜力。