肿瘤微环境HA-TLRs通路在调控巨噬细胞向淋巴内皮祖细胞转分化中的作用及机制研究

Lymphangiogenesis is closely related to lymphatic metastasis in breast cancer and has been a research focus for years. Recent reports have shown that tumor associated macrophages can promote lymphangiogenesis in an alternative way of transdifferentiation into lymphatic endothelial cell progenitors (LECPs). However, the underlying mechanism has not yet been elucidated. Macrophages are usually in a resting state under physiological conditions, but can be transformed to LECPs when stimulated by inflammatory factors in microenvironment. Hyaluronan (HA) is one of the main components of tumor microenvironment. Our previous studies showed that HA in breast cancer tissues was mainly low molecular weight (LMW) fragments that serve as inflammatory stimulator, playing a critical role in tumor lymphangiogenesis and lymphatic metastasis. We also found that macrophages stimulated by LMW-HA could express lymphatic endothelial markers in vitro. These results suggest that tumor-derived HA regulates the transdifferentiation of macrophages into LECPs and participates in lymphangiogenesis. TLRs are the main HA receptors on macrophages, and TLR4 has been reported to be involved in activating myeloid cells transdifferentiation towards LECPs. Whether TLRs contribute to HA-regulated transdifferentiation of macrophages into LECPs has not yet been reported. For the first time, this project aim to investigate the effect of HA-TLRs pathway on modulating the transdifferentiation of macrophages to LECPs in tumor microenvironment and explore its underlying mechanism.

乳腺肿瘤淋巴管新生与肿瘤淋巴转移密切相关，是近年热点。研究显示肿瘤相关巨噬细胞能够以转分化为淋巴内皮祖细胞（LECPs）的新模式促进淋巴管新生，但具体机制不明。生理巨噬细胞（Mφ）是静息态，可受微环境炎性因子影响转分化为LECPs。透明质酸(HA)是肿瘤微环境主要成分。本课题前期研究提示，乳腺癌组织HA多以低分子量炎性刺激分子状态存在，尤其在肿瘤淋巴管新生及癌细胞淋巴转移中有重要作用。我们还发现体外培养Mφ经小分子HA刺激后可表达淋巴管内皮标志物。这些结果提示肿瘤来源HA可能通过调控Mφ向LECPs转分化并参与调控淋巴管新生。TLRs是Mφ上HA主要受体，有报道发现TLR4参与激活髓系细胞向LECPs转分化，但TLRs是否在HA调控Mφ向LECPs转分化过程中发挥作用，尚无报道。本课题拟首次聚焦HA-TLRs调节通路，研究其在肿瘤微环境下调控Mφ向LECPs转分化中的作用及机制。

乳腺肿瘤淋巴管新生与肿瘤淋巴转移密切相关，是近年热点。研究显示肿瘤相关巨噬细胞能够以转分化为淋巴内皮祖细胞（LECPs）的新模式促进淋巴管新生，但具体机制不明。肿瘤微环境细胞外基质（ECM）常被重构。透明质酸（HA）是ECM主要成分。本项目前期研究基础发现:①乳腺癌组织HA多以低分子量HA炎性刺激分子状态，尤其在肿瘤淋巴管新生及癌细胞淋巴转移中有重要作用; ②小鼠腹腔提取Mφ本身并不表达淋巴内皮标志物，经小分子HA刺激后，可表达淋巴内皮分子标志物。推测肿瘤微环境异常改变的HA可激活Mφ、启动其向LECPs转分化，进而在肿瘤淋巴新生中发挥作用。研究发现低分子量HA可通过toll样受体（TLRs)在树突状细胞中发挥促炎症反应。Mφ的TLRs表达丰富，且其亚型TLR4参与激活髓系细胞向LECPs转分化。推测肿瘤微环境异常改变的HA可能通过Mφ表面的TLRs，激活Mφ向LECPs转化。..本项目拟首次聚焦乳腺肿瘤微环境中异常改变的HA在调控巨噬细胞向淋巴内皮祖细胞转分化中的作用，以期从新的视角阐明肿瘤淋巴管新生的途径及相关机制。..研究内容包括：①明确肿瘤微环境中代谢异常的HA与Mφ向LECPs转分化比率的相关性，探明以上两者与肿瘤淋巴管新生、肿瘤淋巴结转移的关系；②阐明肿瘤微环境中代谢异常的HA在诱导Mφ向LECPs转化中的作用；③探索肿瘤微环境中HA-TLRs通路在调控Mφ向LECPs转化中的机制，拟寻找新的阻断肿瘤淋巴转移的靶点。..本课题证实①初步探明了肿瘤微环境异常代谢的活跃小片段（LMW-HA）能够诱导巨噬细胞转分化为淋巴内皮祖细胞；②阐明了肿瘤淋巴管新生的相关机理，HA-TLRs通路相关分子等有望作为治疗及预防肿瘤淋巴管新生的潜在靶点。