The role of CX3CL1 in the targeted immunotherapy of HER2-positive breast cancer

单抗在癌症治疗中的一个主要作用机制是标记肿瘤细胞以抵抗自然杀伤(NK)细胞的攻击，这一过程被称为抗体依赖细胞介导的细胞毒(ADCC)。HER2特异性抗体曲妥珠单抗的这种作用模式已有文献记载。这种治疗成功的一个基本要求是免疫效应细胞充分渗透到肿瘤中，并与肿瘤细胞紧密结合。肿瘤细胞分泌的可溶性趋化因子CX3CL1能够将表达CX3CR1的NK细胞募集到实体瘤中，从而改善ADCC。然而，最初它是以膜结合形式合成的，其在癌症中的作用尚未阐明。可以想象，由于免疫细胞与肿瘤细胞更紧密地结合，这种膜结合形式进一步增强了免疫反应。可溶性形式的释放主要是由ADAM10和ADAM17两种酶通过裂解膜结合型介导的。目前还不清楚这两种形式的CX3CL1对肿瘤细胞上的CX3CR1受体有哪种影响。在本项目中，我们希望以HER2阳性乳腺癌为模型，阐明两种CX3CL1形式的功能。在第一步中，我们想要研究这两种CX3CL1形式的调节及其对曲妥珠单抗处理的HER2阳性乳腺癌细胞株体外NK细胞介导的ADCC的影响(子项目1)。此外，我们还研究了CX3CL1对HER2阳性乳腺癌人源化小鼠模型中曲妥珠单抗治疗的影响(子项目2)。在第三个子项目中，我们希望通过对HER2阳性乳腺癌样本的回顾分析来证实前两个子项目中所取得的结果。在此，我们研究了相关蛋白(CX3CL1、CX3CR1、ADAM10和ADAM17)的表达，并将它们与临床随访数据以及淋巴细胞浸润液(子项目3)相关联。研究结果旨在为CX3CL1的药理调节最终改善乳腺癌的免疫干预提供依据。

A major mechanism of action of monoclonal antibodies in cancer therapy is the labeling of tumor cells for the attack by natural killer (NK) cells, a process called antibody-dependent cell-mediated cytotoxicity (ADCC). Such a mode of action has been documented for the HER2-specific antibody trastuzumab. A fundamental requirement for the success of such therapies is a sufficient infiltration of immune effector cells into the tumor and a close binding of these cells to the tumor cells.The soluble chemokine CX3CL1 secreted by tumor cells is capable of recruiting CX3CR1-expressing NK cells into solid cancers thereby improving ADCC. However, initially it is synthesized as a membrane-bound form which function in cancer has not been elucidated yet. It is conceivable that this membrane-bound form further enhances immune responses due to a closer binding of immune cells to the tumor cells. Release of the soluble form is mediated mainly by the two proteases ADAM10 and ADAM17 through cleavage of the membrane-bound form. It is yet unclear which effect both forms of CX3CL1 have on the CX3CR1 receptor on tumor cells. In the present project we want to elucidate the function of both CX3CL1 forms using HER2-positive breast cancer as a model disease.In a first step we want to investigate the regulation of both forms of CX3CL1 and their impact on NK cell-mediated ADCC of trastuzumab-treated HER2-positive breast cancer cell lines in vitro (subproject 1). In addition, we study the effect of CX3CL1 on a trastuzumab therapy in a humanized tumor mouse model of HER2-positive breast cancer in vivo (subproject 2). In the third subproject we want to substantiate the results obtained in the first two subprojects through a retrospective analysis of HER2-positive breast cancer samples. Herein we investigate the expression of the proteins involved (CX3CL1, CX3CR1, ADAM10 and ADAM17) and correlate them with the clinical follow-up data as well as with the lymphocytic infiltrate (subproject 3).The results are intended to provide a basis for a pharmacological regulation of CX3CL1 eventually improving immune intervention in breast cancer.