肿瘤相关巨噬细胞为周围肿瘤细胞提供铁源及其调控机制的研究

Iron is an essential trace element to maintain the survival and growth of cells. Though it is known for a long time that the solid tumor is under the specific conditions with hypoxia and very limited competitive nutrients, it is unknown how and where the tumor cells obtain enough iron for their rapid growth. Tumor-associated macrophages (TAMs, M2-like) express a very high level of iron exporter ferroportin (FPN1) in the tumor microenvironment. Our previous studies found that some iron accumulated around the cancer cells in the clinical tumor samples, revealed by DAB enhanced Perl′s iron stain; conditioned media from M2-like macrophages, induced by IL-4, promoted tumor cell proliferation, an effect that was inhibited by FPN1 knockout or by direct iron chelation in the conditional media, suggesting that macrophages may foster tumor growth, at least partly, by providing tumor cells with iron. In this study, we will use FPN1 knockout mice as a tool along with human clinical samples of hepatocellular carcinoma and cultured cells to perform a set of in vivo and in vitro experiments to investigate whether TAMs-released iron is the main source for tumor growth and what regulates TAMs to release the iron. This work will reveal what makes TAMs release iron, how important the released iron is, and what effects the iron makes on cancer cells and tumor growth. This project will provide a theoretical basis and shed light on revealing the molecular mechanism and regulation of iron metabolism of tumor tissues and on designing iron chelators targeting TAMs in the treatment of cancers.

铁是维持细胞正常生长的必需微量元素。癌细胞怎样从血供受限营养竞争激烈的微环境中获得充足的铁是困扰肿瘤铁代谢研究的难点。肿瘤微环境中肿瘤相关巨噬细胞（TAMs）高表达铁输出蛋白FPN1。我们的前期研究发现临床肿瘤样本中，癌细胞周围有明显铁的聚集；用IL-4诱导巨噬细胞的条件培养基培养肿瘤细胞，发现和野生型相比，FPN1敲除后不能有效支持肿瘤细胞的生长，和野生型巨噬细胞条件培养基螯合铁后的表型一致；体内阻断巨噬细胞的铁排出影响肿瘤的生长, 提示TAMs可能为肿瘤细胞提供赖以生存的主要铁源。本研究以肝癌为研究对象，以巨噬细胞特异性敲除FPN1小鼠为工具，从体内和体外实验以及肝癌患者样本多个层面研究TAMs释放铁的来源，释放的铁是否供应给肿瘤细胞，及对肿瘤生长的影响。本项目的开展为揭示肿瘤铁代谢分子机制与调控规律及靶向设计铁螯合剂治疗肿瘤提供理论依据和新的设计思路。

铁是维持细胞正常生长的必需微量元素。癌细胞怎样从血供受限营养竞争激烈的微环境中获得充足的铁是困扰肿瘤铁代谢研究的难点。肿瘤微环境中肿瘤相关巨噬细胞（TAMs）高表达铁输出蛋白FPN1。我们的前期研究发现临床肿瘤样本中，癌细胞周围有明显铁的聚集；用IL-4诱导巨噬细胞的条件培养基培养肿瘤细胞，发现和野生型相比，FPN1敲除后不能有效支持肿瘤细胞的生长，和野生型巨噬细胞条件培养基螯合铁后的表型一致；体内阻断巨噬细胞的铁排出影响肿瘤的生长, 提示TAMs可能为肿瘤细胞提供赖以生存的主要铁源。本研究以巨噬细胞特异性敲除FPN1小鼠为工具，从体内和体外实验以及肝癌患者样本多个层面研究TAMs释放铁的来源，释放的铁是否供应给肿瘤细胞，及对肿瘤生长的影响。重要结果：1. 巨噬细胞FPN1能有效支持肿瘤细胞的生长，在肝癌和乳腺癌动物模型中得到验证；2. 铁影响巨噬细胞的分化，高铁的蓄积促巨噬细胞向M1分化，以排铁特征为导向的巨噬细胞向M2分化； 3. 桧木醇与铁形成复合物通过诱导铁死亡促进三阴性乳腺癌的治疗。 本项目的开展为揭示肿瘤铁代谢分子机制与调控规律及靶向设计铁螯合剂治疗肿瘤提供理论依据和新的设计思路。