自噬是一种依赖于溶酶体的大量降解过程，对于细胞的存活至关重要，但过度的自噬会导致一种名为自 噬性死亡（autosis）的独特细胞死亡形式。三阴性乳腺癌（TNBC）是一种高度侵袭性的乳腺癌亚型，其自噬过程存在明显缺陷。在之前的研究中，我们开发了能够特异性靶向关键的自噬蛋白Beclin 1的稳定 肽，并诱导自噬以及促进内溶-溶酶体运输。我们在这里显示一种主导肽Tat-SP4在TNBC细胞中引起轻度增加的自噬，但表现出有效的抗增殖效果，这种抗增殖效果不能被编程细胞死亡途径的抑制剂挽救。由Tat-SP4引起 的细胞死亡表现出自噬性死亡的典型特征，包括持续粘附在底物表面、质膜破裂以及被洋地黄类药物地高 辛有效挽救，地高辛可以阻断Na+/K+ ATP酶。Tat-SP4还引起明显的线粒体功能障碍，包括线粒体膜电位丧失、 线粒体产生活性氧增加以及氧化磷酸化减少。在TNBC异种移植模型中，Tat-SP4的抗增殖效果得到证实。我们的研究揭示了自噬性死亡的三个显著方面。首先，如果这种增加超过宿主细胞内源性能力，适度增加的自噬可以触发自噬性死 亡。其次，线粒体可能在自噬性死亡中起到关键作用，失调的自噬导致线粒体功能障碍进而触发自噬性死亡。 最后，内在的自噬缺陷和静止的线粒体生物能量特征可能使TNBC细胞极易受到自噬性死亡的影响。我们设计 的肽类如Tat-SP4可能成为针对TNBC的潜在治疗候选药物，通过针对这一易感性进行靶向治疗作用。©2023年.细胞死亡与分化协会（ADMC）。

Autophagy is a lysosome-dependent bulk degradation process essential for cell viability but excessive autophagy leads to a unique form of cell death termed autosis. Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer with notable defect in its autophagy process. In previous studies, we developed stapled peptides that specifically targeted the essential autophagy protein Beclin 1 to induce autophagy and promote endolysosomal trafficking. Here we show that one lead peptide Tat-SP4 induced mild increase of autophagy in TNBC cells but showed potent anti-proliferative effect that could not be rescued by inhibitors of programmed cell death pathways. The cell death induced by Tat-SP4 showed typical features of autosis including sustained adherence to the substrate surface, rupture of plasma membrane and effective rescue by digoxin, a cardioglycoside that blocks the Na+/K+ ATPase. Tat-SP4 also induced prominent mitochondria dysfunction including loss of mitochondria membrane potential, elevated mitochondria reactive oxygen species and reduced oxidative phosphorylation. The anti-proliferative effect of Tat-SP4 was confirmed in a TNBC xenograft model. Our study uncovers three notable aspects of autosis. Firstly, autosis can be triggered by moderate increase in autophagy if such increase exceeds the endogenous capacity of the host cells. Secondly, mitochondria may play an essential role in autosis with dysregulated autophagy leading to mitochondria dysfunction to trigger autosis. Lastly, intrinsic autophagy deficiency and quiescent mitochondria bioenergetic profile likely render TNBC cells particularly susceptible to autosis. Our designed peptides like Tat-SP4 may serve as potential therapeutic candidates against TNBC by targeting this vulnerability.© 2023. Cell Death Differentiation Association (ADMC).