透明质酸介导CD44寡聚化诱发TAM细胞M2样激活对乳腺肿瘤耐药性的作用研究

Recent evidence has unveiled the critical role of tumor-associated macrophage(TAM) in tumor drug resistance.However, the molecular mechanisms whereby TAMs regulate drug resistant remain largely unknown.It has been previously described that hyaluronan(HA) in the malignant tumors matrix is overexpressed, and the secreted hyaluronan induced transient classical or M1 activation of monocytes and subsequently drove them to develop into immunosuppressive or M2 macrophages,to form "tumor-associated macrophage(TAM)".Previous work from our laboratory has shown that ① hyaluronan(HA) is overexpressed in breast cancer cells and is positively correlated with chemoresistance② CD44 clustering induced by HA triggered distinct functions. For the first time, we propose that CD44 clustering induced by HA is closely correlated with the switch from the M1 to the M2 phenotype, which may promote tumour chemoresistance. This project includs: ① To observe if HA could exert their function by inducing CD44 clustering and the mechanisms invovled; ②oligosaccharides of HA will be utilized to reduced the clustering of CD44, the consequent activation of M2 macrophages will be determined. The effect in reversing chemotherapy resistance targeting to CD44-overexpressing tumors will be studied . The project may provide a theoretical basis for cancer therapy.

肿瘤相关巨噬细胞( tumor-associated macrophage，TAM )是近年研究的热点。新近研究表明TAM 与肿瘤化疗耐药呈正相关，其机理至今不明确。据报道恶性肿瘤异常分泌的透明质酸（Hyaluronan，HA），参与诱导循环单核细胞瞬间M1样激活及随后向M2样激活的转变，形成TAM。本课题前期示①乳腺肿瘤细胞高表达HA，并与其耐药性呈正相关②HA能诱导其受体CD44寡聚化而致细胞功能改变。基于此，本研究首次探讨HA诱导TAM细胞表面CD44寡聚化对调控单核细胞M1型向TAM-M2样激活转变的影响，进一步研究其对诱导乳腺肿瘤耐药的作用。内容①通过实验阐明HA介导的CD44寡聚化在TAM-M2样激活中的作用及机制②采用HA的彻底降解小片段oHA解除由HA介导的CD44寡聚化，诱导TAM-M2表型改变，观察乳腺肿瘤化疗耐药性的变化，为寻找肿瘤治疗新策略提供实验依据。

乳腺癌化疗失败的主要原因是肿瘤的局部浸润和药物耐受性。乳腺癌基质中存在大量肿瘤相关巨噬细胞(Tumor associated macrophages，TAMs)，TAM可促进肿瘤进展。研究发现TAM与肿瘤化疗耐药性密切相关，但机理尚不明确。TAM具有M2样巨噬细胞的表型和功能，但其形成机制尚不明确。目前认为肿瘤微环境在诱导M2样TAM形成中发挥关键作用。透明质酸（hyaluronan, HA）是细胞外基质的主要成分，可参与免疫调控作用。CD44是HA的主要受体，HA-CD44 相互作用可参与多种生物学作用。本研究推测提出乳腺肿瘤来源HA可通过诱导单核细胞表面CD44寡聚化介导M2样巨噬细胞的形成，进而参与乳腺癌耐药。主要研究内容包括：①检测乳腺癌患者肿瘤组织中HA含量与M2样TAM数量，分析二者是否具有相关性；②探索乳腺肿瘤来源HA是否可诱导单核细胞分化为M2样TAM；③探明乳腺肿瘤来源HA是否可诱导单核细胞表面CD44寡聚化，并探索HA-CD44相互作用参与M2样TAM形成的具体分子机制；④体外建立TAM模型，证实TAM参与乳腺肿瘤细胞耐药；⑤探索TAM参与乳腺肿瘤耐药的具体机制。所取得的重要结果：①证实乳腺肿瘤微环境中HA表达与M2样TAM数量呈正相关，二者均与肿瘤恶性进展相关；②在细胞和动物实验水平均证实乳腺肿瘤来源HA可诱导单核细胞分化为M2样TAM；③乳腺肿瘤来源HA可诱导单核细胞表面CD44寡聚化，HA-CD44相互作用可通过激活下游ERK1/2-STAT3信号通路诱导M2样TAM形成；④证实M2样TAM可通过IL-10/STAT3/bcl-2信号通路参与乳腺肿瘤耐药。本研究从新的角度阐明巨噬细胞、肿瘤细胞与HA的相互作用，为完整阐明肿瘤微环境在M2样TAM形成及乳腺化疗耐药中的作用提供新的理论依据，可望为靶向TAM的乳腺癌治疗提供新的药物靶点，开辟乳腺癌治疗新途径，具有重要的临床意义。