Triple-negative breast cancers (TNBCs) are characterized by poor survival, prognosis, and gradual resistance to cytotoxic chemotherapeutics, like doxorubicin (DOX). The clinical utility of DOX is limited by its cardiotoxic and chemoresistant effects that manifest over time. To induce chemoresistance, TNBC rewires oncogenic gene expression and cell signaling pathways. Recent studies have demonstrated that reprogramming of branched-chain amino acids (BCAAs) metabolism facilitates tumor growth and survival. Branched-chain ketoacid dehydrogenase kinase (BCKDK), a regulatory kinase of the rate-limiting enzyme of the BCAA catabolic pathway, is reported to activate RAS/RAF/MEK/ERK signaling to promote tumor cell proliferation. However, it remains unexplored if BCKDK action remodels TNBC proliferation and survival per se and influences susceptibility to DOX-induced genotoxic stress. TNBC cells treated with DOX exhibited reduced BCKDK expression and intracellular BCKAs. Genetic and pharmacological inhibition of BCKDK in TNBC cell lines also showed a similar reduction in intracellular and secreted BCKAs. BCKDK silencing in TNBC cells downregulated mitochondrial metabolism genes, reduced electron complex protein expression, oxygen consumption, and ATP production. Transcriptome analysis of BCKDK silenced cells confirmed dysregulation of mitochondrial metabolic networks and upregulation of the apoptotic signaling pathway. Furthermore, BCKDK inhibition with concurrent DOX treatment exacerbated apoptosis, caspase activity, and loss of TNBC proliferation. Inhibition of BCKDK in TNBC also upregulated sestrin 2 and concurrently decreased mTORC1 signaling and protein synthesis. Overall, loss of BCKDK action in TNBC remodels BCAA flux, reduces protein translation triggering cell death, ATP insufficiency, and susceptibility to genotoxic stress.

三阴性乳腺癌 (TNBC) 的特点是存活率、预后差，以及对阿霉素 (DOX) 等细胞毒性化疗药物逐渐产生耐药性。DOX 的临床效用受到其随时间显现的心脏毒性和化学抗性作用的限制。为了诱导化学抗性，TNBC 重新连接致癌基因表达和细胞信号通路。最近的研究表明，支链氨基酸 (BCAA) 代谢的重编程促进了肿瘤的生长和存活。据报道，支链酮酸脱氢酶激酶 (BCKDK) 是一种 BCAA 分解代谢途径限速酶的调节激酶，可激活 RAS/RAF/MEK/ERK 信号传导以促进肿瘤细胞增殖。然而，如果 BCKDK 作用重塑 TNBC 增殖和存活本身并影响对 DOX 诱导的基因毒性应激的易感性，则仍未探索。用 DOX 处理的 TNBC 细胞表现出降低的 BCKDK 表达和细胞内 BCKA。TNBC 细胞系中 BCKDK 的遗传和药理学抑制也显示出细胞内和分泌 BCKA 的类似减少。TNBC 细胞中的 BCKDK 沉默下调线粒体代谢基因，减少电子复合蛋白表达、氧消耗和 ATP 产生。BCKDK 沉默细胞的转录组分析证实了线粒体代谢网络的失调和凋亡信号通路的上调。此外，BCKDK 抑制与同步 DOX 治疗加剧了细胞凋亡、半胱天冬酶活性和 TNBC 增殖的丧失。TNBC 中 BCKDK 的抑制也上调了 sestrin 2，同时降低了 mTORC1 信号传导和蛋白质合成。总体而言，TNBC 中 BCKDK 作用的丧失会重塑 BCAA 通量，减少触发细胞死亡的蛋白质翻译、ATP 不足和对基因毒性应激的易感性。