乳腺恶性叶状肿瘤易复发、转移率高，且复发后组织特性更加恶化，但其恶性进展机制不明确。目前尚无有效的化疗及靶向治疗药物。我们前期的研究已经证实作为叶状肿瘤细胞主要成分之一的肌成纤维细胞的分化促进了肿瘤的恶性进展和转移；肿瘤相关巨噬细胞（TAMs）通过分泌CCL18，促进了肌成纤维细胞分化；反之，肌成纤维细胞是否能够激活TAMs呢？我们通过细胞因子芯片分析了良、恶性叶状肿瘤细胞因子的差异，发现恶性叶状肿瘤细胞分泌的CCL5可以促进巨噬细胞向TAMs表型分化，敲低CCL5的肌成纤维细胞与TAMs共培养体系中，CCL18的分泌显著下降，提示肌成纤维细胞可能通过分泌CCL5促进巨噬细胞向TAMs分化。本课题拟进一步研究肌成纤维细胞对TAMs激活的机制，在体外及人源化小鼠模型中探寻二者的相互作用环路在肿瘤进展及转移中的作用，完善叶状肿瘤恶性进展及转移的机制，为恶性叶状肿瘤治疗提供新的靶点。

Malignant phyllodes tumors (PT) of breast are characterized by a high risk of local recurrence and distant metastasis. Furthermore, recurrent phyllodes tumors showed a progression toward a more malignant phenotype. However, the underlying mechanism of malignant progression remains unknown and current adjuvant chemotherapy or targeted therapy is deemed ineffective against phyllodes tumors. Our previous study showed tumor-associated macrophages (TAMs) induced myofibroblast differentiation by secreting CCL18 and in turn myofibroblast differentiation promoted the malignant progression and metastasis of PT. However, whether myofibroblast can activate macrophages to a TAM-like phenotype remains unknown. We analyzed the cytokine level differences between benign and malignant PT cells and found that CCL5 secreted by malignant PT cells can induce macrophage activation to a TAM-like phenotype. When co-cultured with myofibroblast with prior CCL5 knocked down by siRNA, the protein levels of CCL18 from the primary TAMs were significantly decreased. All these studies suggest that myofibroblast may induce the differentiation of macrophages to TAMs by secreting CCL5. Therefore, we will further explore the molecular mechanism of CCL5 regulating the activation of TAMs and the importance of the positive feedback loop between myofibroblast and TAMs in PT progression and metastasis in both the co-culture systems and humanized mice. Finally, we will demonstrate the clinical significance of CCL5 in PT progression. Taken together, our study will provide a new insight and possibly aid the discovery of new targets in inhibiting the recurrence and metastasis of breast PT.