A recombinant fragment of human κ-Casein, termed RL2, induces cell death of breast cancer cells; however, molecular mechanisms of RL2-mediated cell death have remained largely unknown. In the current study, we have decoded the molecular mechanism of the RL2-mediated cell death and found that RL2 acts via the induction of mitophagy. This was monitored by the loss of adenosine triphosphate production, LC3B-II generation, and upregulation of BNIP3 and BNIP3L/NIX, as well as phosphatase and tensin homolog-induced kinase 1. Moreover, we have analyzed the cross talk of this pathway with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis upon combinatorial treatment with RL2 and TRAIL. Strikingly, we found two opposite effects of this co-treatment. RL2 had inhibitory effects on TRAIL-induced cell death upon short-term co-stimulation. In particular, RL2 treatment blocked TRAIL-mediated caspase activation, cell viability loss, and apoptosis, which was mediated via the downregulation of the core proapoptotic regulators. Contrary to short-term co-treatment, upon long-term co-stimulation, RL2 sensitized the cells toward TRAIL-induced cell death; the latter observation provides the basis for the development of therapeutic approaches in breast cancer cells. Collectively, our findings have important implications for cancer therapy and reveal the molecular switches of the cross talk between RL2-induced mitophagy and TRAIL-mediated apoptosis.

人κ-酪蛋白的重组片段称为RL2，可诱导乳腺癌细胞死亡。然而，RL2介导的细胞死亡的分子机制仍是未知之数。在当前的研究中，我们已经解码了RL2介导的细胞死亡的分子机制，并发现RL2是通过诱导细胞吞噬而起作用的。这可以通过三磷酸腺苷生成的损失，LC3B-II的产生以及BNIP3和BNIP3L / NIX以及磷酸酶和张力蛋白同源物诱导的激酶1的上调来监测。此外，我们还分析了该途径与肿瘤的相声RL2和TRAIL联合治疗后，坏死因子相关的凋亡诱导配体（TRAIL）诱导的凋亡。令人惊讶的是，我们发现这种共同处理有两个相反的作用。短期共刺激时，RL2对TRAIL诱导的细胞死亡具有抑制作用。特别是，RL2处理可阻断TRAIL介导的caspase活化，细胞活力丧失和凋亡，这是通过核心凋亡调节因子的下调介导的。与短期共同治疗相反，在长期共同刺激下，RL2使细胞对TRAIL诱导的细胞死亡敏感。后一观察为乳腺癌细胞治疗方法的发展提供了基础。总的来说，我们的发现对癌症治疗具有重要意义，并揭示了RL2诱导的线粒体吞噬和TRAIL介导的细胞凋亡之间的相互影响的分子转换。这是通过核心凋亡调节因子的下调介导的。与短期共同治疗相反，在长期共同刺激下，RL2使细胞对TRAIL诱导的细胞死亡敏感。后一观察为乳腺癌细胞治疗方法的发展提供了基础。总的来说，我们的发现对癌症治疗具有重要意义，并揭示了RL2诱导的细胞吞噬作用与TRAIL介导的细胞凋亡之间的串扰的分子转换。这是通过核心凋亡调节因子的下调介导的。与短期共同治疗相反，在长期共同刺激下，RL2使细胞对TRAIL诱导的细胞死亡敏感。后一观察为乳腺癌细胞治疗方法的发展提供了基础。总的来说，我们的发现对癌症治疗具有重要意义，并揭示了RL2诱导的线粒体吞噬和TRAIL介导的细胞凋亡之间的相互影响的分子转换。