肝激酶B1（LKB1）跨物种控制细胞代谢和细胞极性。我们先前确定了一种由LKB1对转化生长因子β（TGFβ）信号的负调节机制。这种机制对于上皮极性和形态发生的影响仍未知。在证明人乳房组织表达强烈的LKB1蛋白水平，而侵袭性乳腺癌表现为显著降低LKB1水平后，我们将重点放在三维泡状器官的乳腺形态发生研究上。CRISPR / Cas9引入的STK11（LKB1）失去功能突变导致3D泡状体形成显著缺陷，导致在Matrigel中嵌入的年轻泡状器官的无定形生长和旋转丧失。这种缺陷与TGFβ信号的增强相关，包括TGFβ自我诱导和介导上皮-间质转化（EMT）的转录因子的诱导。蛋白标记分析确认LKB1敲除细胞对TGFβ信号的EMT反应更为有效。因此，TGFβ类I受体激酶的化学抑制在很大程度上恢复了LKB1敲除细胞的形态发生缺陷。同样，骨形态发生蛋白通路或TANK结合激酶1的化学抑制，或EMT因子SNAI1的基因沉默部分恢复了LKB1敲除缺陷。因此，LKB1通过限制促进EMT的通路来维持乳腺上皮形态发生。乳腺癌中LKB1表达的下调因此预测将与由SNAI1和TGFβ家族成员诱导的增强EMT有关。©2023年作者。由Wiley Periodicals LLC出版的细胞生理学期刊发布。

The liver kinase B1 (LKB1) controls cellular metabolism and cell polarity across species. We previously established a mechanism for negative regulation of transforming growth factor β (TGFβ) signaling by LKB1. The impact of this mechanism in the context of epithelial polarity and morphogenesis remains unknown. After demonstrating that human mammary tissue expresses robust LKB1 protein levels, whereas invasive breast cancer exhibits significantly reduced LKB1 levels, we focused on mammary morphogenesis studies in three dimensional (3D) acinar organoids. CRISPR/Cas9-introduced loss-of-function mutations of STK11 (LKB1) led to profound defects in the formation of 3D organoids, resulting in amorphous outgrowth and loss of rotation of young organoids embedded in matrigel. This defect was associated with an enhanced signaling by TGFβ, including TGFβ auto-induction and induction of transcription factors that mediate epithelial-mesenchymal transition (EMT). Protein marker analysis confirmed a more efficient EMT response to TGFβ signaling in LKB1 knockout cells. Accordingly, chemical inhibition of the TGFβ type I receptor kinase largely restored the morphogenetic defect of LKB1 knockout cells. Similarly, chemical inhibition of the bone morphogenetic protein pathway or the TANK-binding kinase 1, or genetic silencing of the EMT factor SNAI1, partially restored the LKB1 knockout defect. Thus, LKB1 sustains mammary epithelial morphogenesis by limiting pathways that promote EMT. The observed downregulation of LKB1 expression in breast cancer is therefore predicted to associate with enhanced EMT induced by SNAI1 and TGFβ family members.© 2023 The Authors. Journal of Cellular Physiology published by Wiley Periodicals LLC.