三阴性乳腺癌（TNBC）由于缺乏或不显着表达靶向雌激素受体（ER）和人表皮生长因子受体2（HER2）而难以治疗乳腺癌亚型。因此，在 TNBC 中找到可靶向的蛋白质或信号通路将影响患者的护理。在此，我们报道混合谱系激酶 (MLK​​) 家族的成员 MLK3 是 G 蛋白偶联蛋白酶激活受体 1 (PAR1) 的效应子，通过小分子抑制剂靶向 MLK3 可预防 PAR1 介导的 TNBC肿瘤发生。人类乳腺肿瘤的计算机模拟和免疫组织化学分析显示，TNBC 肿瘤中 PAR1 和 MLK3 过度表达。治疗 α-凝血酶和 PAR1 激动剂可增加 TNBC 细胞中 MLK3 和 JNK 的活性并诱导细胞迁移。 PAR1 阳性/高 (PAR1 /hi) 的 TNBC 细胞群体表现出侵袭性肿瘤表型，且 MLK3 信号传导增强。此外，联合抑制 PAR1 和 MLK3 可减轻临床前 TNBC 模型中的 TNBC 肿瘤负荷。我们的数据表明 PAR1-MLK3 轴的激活促进 TNBC 肿瘤发生。因此，针对 MLK3 和 PAR1 的联合治疗可以有效减少 TNBC 肿瘤负担。版权所有 © 2024。由 Elsevier B.V. 出版。

Triple-negative breast cancer (TNBC) is difficult to treat breast cancer subtype due to lack or insignificant expressions of targetable estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2). Therefore, finding a targetable protein or signaling pathway in TNBC would impact patient care. Here, we report that a member of the Mixed Lineage Kinase (MLK) family, MLK3, is an effector of G-protein-coupled proteinase-activated receptors 1 (PAR1) and targeting MLK3 by a small-molecule inhibitor prevented PAR1-mediated TNBC tumorigenesis. In silico and immunohistochemistry analysis of human breast tumors showed overexpression of PAR1 and MLK3 in TNBC tumors. Treating α-thrombin and PAR1 agonist increased MLK3 and JNK activities and induced cell migration in TNBC cells. The PAR1 positive/high (PAR1+/hi) population of TNBC cells showed aggressive tumor phenotype with increased MLK3 signaling. Moreover, combined inhibition of the PAR1 and MLK3 mitigated the TNBC tumor burden in preclinical TNBC models. Our data suggests that activation of the PAR1-MLK3 axis promotes TNBC tumorigenesis. Therefore, combinatorial therapy targeting MLK3 and PAR1 could effectively reduce TNBC tumor burden.Copyright © 2024. Published by Elsevier B.V.