Despite extensive research, strategies to effectively combat breast cancer stemness and achieve a definitive cure remains elusive. CD44, a well-defined cancer stem cell (CSC) marker is reported to promote breast cancer tumorigenesis, metastasis, and chemoresistance. However, mechanisms leading to its enhanced expression and function is poorly understood. Here, we demonstrate that USP10 positively regulates CD44 protein levels and its downstream actions. While USP10 depletion prominently down-regulates CD44 protein levels and functions, its overexpression significantly enhances CD44 protein levels, leading to enhanced cluster tumor cell formation, stemness, and metastasis in breast cancer cells both in vitro and ex vivo in primary human breast tumor cells. USP10 interacts with CD44 and stabilizes it through deubiquitination both in breast cancer cell lines and human breast cancer-derived primary tumor cells. Stabilized CD44 shows enhanced interaction with cytoskeleton proteins Ezrin/Radixin/Moesin and potently activates PDGFRβ/STAT3 signaling which are involved in promoting CSC traits. Using USP10 stably expressing 4T1 cells, we further demonstrate that the USP10-CD44 axis potently promotes tumorigenicity in vivo in mice, while simultaneous depletion of CD44 in these cells renders them ineffective. In line with these findings, we further showed that inhibition of USP10 either through RNAi or the pharmacological inhibitor Spautin-1 significantly mitigated CD44 levels and its downstream function ex vivo in primary breast tumor cells. Finally, we demonstrated that primary breast tumor cells are more susceptible to chemotherapy when co-treated with USP10 inhibitor indicating that the USP10-CD44 axis could be an attractive therapeutic target in combination with chemotherapy in CD44 expressing breast cancers.

中文翻译：

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USP10 去泛素化和稳定 CD44，导致乳腺癌细胞增殖、干性和转移增强。


尽管进行了广泛的研究，但有效对抗乳腺癌干性并实现明确治愈的策略仍然难以捉摸。据报道，CD44 是一种定义明确的癌症干细胞 （CSC） 标志物，可促进乳腺癌肿瘤发生、转移和化疗耐药。然而，导致其表达和功能增强的机制知之甚少。在这里，我们证明 USP10 正向调节 CD44 蛋白水平及其下游作用。虽然 USP10 耗竭显著下调 CD44 蛋白水平和功能，但其过表达显着增强 CD44 蛋白水平，导致原代人乳腺肿瘤细胞体外和离体乳腺癌细胞的簇状肿瘤细胞形成、干性和转移增强。USP10 与 CD44 相互作用，并通过去泛素化稳定乳腺癌细胞系和人乳腺癌衍生的原发性肿瘤细胞。稳定的 CD44 与细胞骨架蛋白 Ezrin/Radixin/Moesin 的相互作用增强，并有效激活参与促进 CSC 性状的 PDGFRβ/STAT3 信号传导。使用稳定表达 USP10 的 4T1 细胞，我们进一步证明 USP10-CD44 轴在小鼠体内有效促进致瘤性，而这些细胞中 CD44 的同时耗竭使它们无效。与这些发现一致，我们进一步表明，通过 RNAi 或药理学抑制剂 Spautin-1 抑制 USP10 显着减轻了原发性乳腺肿瘤细胞中 CD44 水平及其离体下游功能。 最后，我们证明，当与 USP10 抑制剂共同治疗时，原发性乳腺肿瘤细胞更容易受到化疗的影响，这表明 USP10-CD44 轴与化疗联合治疗可能是一个有吸引力的治疗靶点 CD44 表达乳腺癌。