LGR4参与发育、细胞干性维持及癌症发生发展等生命过程,且主要以增强Wnt信号通路来发挥其生物功能。前期的工作中，我们发现LGR4在侵袭性乳腺癌组织中高表达、造成预后差，而且参与Wnt信号以外的信号通路的调控，但其中具体的分子机制并不明确。本项目将在此基础上，构建特异性敲除LGR4的基底样乳腺癌细胞系，通过多维度蛋白质组学技术，探索以LGR4为中心的膜蛋白复合物的动态组装过程以及LGR4下游参与调控的转录因子，初步结果发现LGR4通过与Notch家族受体和配体作用, 介导 Notch 信号通路的转导,进而调控下游转录因子 FOXJ2、E2F4 等的转录活性。后期以Notch信号通路入手进行生物验证，探讨LGR4介导Notch促进乳腺癌恶性发展的分子机制，为今后进一步在动物模型和临床应用打下理论基础。

LGR4 plays an important role in development, stem cell maintenance, and cancer development. Previous studies suggest that biological function of LGR4 is mainly mediated through its role in potentiating Wnt signaling. In a previous work, we found that LGR4 is highly expressed in invasive breast cancer tissues, which is correlated with poor prognosis. Moreover, LGR4 may regulates other signaling pathways in addition to Wnt signaling in triple-negative breast cancer cell lines, but the specific molecular mechanism is not clear. In this project, we will employ a multidimensional proteomics technique to explore the dynamic regulation of LGR4 membrane protein complexes and the downstream transcription factors in the LGR4 knock-out basal-like breast cancer cell lines. Preliminary results showed that LGR4 mediates the signaling transduction of the Notch pathway through the interaction with Notch receptors and ligands, and regulates the transcriptional activities of downstream transcription factors including FOXJ2, and E2F4. We will follow up with biochemical validation of the Notch signaling pathway. In summary, this project will focus on investigating the temporal dynamic process of LGR4 membrane protein complexes and the activity of downstream transcription factor, which helps to advance our understanding on how LGR4-mediate Notch pathway promote the malignant development of basal-like breast cancer and provides a solid foundation for testing in animal models and clinical applications.