探讨胶原凝集素-11（CL-11）在肿瘤生长过程中的作用及其可能机制

Tumor immune-microenvironment plays critical roles in cancer development, progression and control. Emerging research suggest that glycan-lectin interactions drives immune suppression in the tumor microenvironment. However, the mechanisms involved in glycan-lectin interaction-mediated immune suppression are poorly understood. Furthermore, previous research in this field was mainly focus on either C-type lectin receptors (e.g. siglecs, DC-SIGN, which are present on cell membrane) or galectins (which specific binds β-galactose). Little is known about the role of soluble C-type lectins in tumor growth. Collectin 11 (CL-11) is a newly described soluble C-type lectin of innate immunity, which mainly binds L-fucose and mannose. It plays important roles in host defense, development and regulation of cellular processes. Our preliminary studies have shown that tumor (melanoma) growth was suppressed in CL-11 deficient mice, suggesting a role of CL-11 in promoting tumor growth. Our preliminary results also indicate that CL-11 has a stimulatory effect on tumor cell proliferation and favours skewing macrophages toward to M2 type. We therefore hypothesized that CL-11 can promote tumor growth through regulating macrophage function to mediate immune suppression and directly acting on tumor cells to cause tumor cell dividing. In the proposed project, we will: i) further confirm the role of CL-11 in promoting tumor growth in murine subcutaneous models, using several types of tumor cells (e.g. melanoma, liver cancer, breast cancer), ii) investigate the mechanisms of CL-11 regulating macrophage function and stimulating tumor cell proliferation, iii) and explore the therapeutic potential of blocking CL-11 interaction with macrophages or tumor cells. The successful delivery of the project will, for the first time, demonstrate the role of CL-11 in promoting tumor growth, describe potential mechanisms by which CL-11 promotes tumor growth, and provide supporting information for further translational study.

肿瘤免疫微环境对肿瘤发生发展起着重要影响作用。近期研究表明多糖-凝集素交互作用可诱导肿瘤微环境免疫抑制，但其机制仍不清楚。学界普遍关注受体类C型凝集素，而对可溶性C型凝集素在肿瘤生长中的作用报道较少。胶原凝集素11（CL-11）是新发现的可溶性C型凝集素家族成员，在宿主防御、发育以及细胞功能调控方面发挥重要作用。预实验发现黑色素瘤在CL-11敲除小鼠体内生长受抑，CL-11促进瘤细胞增殖并有利于巨噬细胞（MΦ）M2型极化。我们提出：CL-11通过调控MΦ功能引起免疫抑制以及直接刺激瘤细胞增殖从而促进肿瘤生长。本课题我们将在CL-11敲除小鼠皮下移植瘤模型中证实CL-11促肿瘤生长作用；探讨CL-11调控MΦ功能以及刺激肿瘤增殖的作用机制；探索阻断CL-11与MΦ或肿瘤细胞作用是否能有效抑制肿瘤生长。本课题的成功实施将首次阐明CL-11促肿瘤生长作用及其可能机制，为后续转化医学研究提供依据。

肿瘤微环境免疫抑制是促进肿瘤发生发展的重要因素，尽管基于多糖-凝集素交互作用诱导的肿瘤免疫抑制研究已取得了阶段性突破，但其机制仍不清楚。胶原凝集素11（CL-11）是新发现的可溶性C型凝集素家族成员，在宿主防御、发育以及细胞功能调控方面发挥重要作用。本课题中，我们通过CL-11敲除小鼠B16黑色素瘤细胞皮下移植瘤模型证实了CL-11促肿瘤生长的作用；探讨了CL-11调控巨噬细胞功能以及刺激肿瘤细胞增殖的相关作用机制；最后探索了阻断CL-11与巨噬细胞或肿瘤细胞作用是否能有效抑制肿瘤生长。我们发现：CL-11缺失导致小鼠皮下移植瘤生长受限，生存期显著延长，而外源性rCL-11输入可有效诱导肿瘤生长；进一步机制研究发现，CL-11可以直接与肿瘤细胞表面甘露糖基（Mannosyl）位点结合，经信号转导激活肿瘤细胞内MAPK信号通路磷酸化，推动细胞周期G0/G1期向S期转化，进而促进肿瘤细胞增殖；同时，CL-11缺失可导致肿瘤微环境中巨噬细胞发生M1型极化反应，提升瘤内巨噬细胞中促炎细胞因子的释放水平，进而诱导肿瘤微环境形成抗肿瘤免疫反应；外源性rCL-11可结合巨噬细胞表面Mannosyl位点，促进巨噬细胞发生M2型极化反应；而CL-11缺失组与WT组荷瘤小鼠血清中C3a与C5a的表达并无显著差异，表明CL-11调控肿瘤生长并不依赖于补体系统的激活；随后我们通过检索GEO数据库及收集本院临床样本，证明了人黑色素瘤样本中CL-11表达显著性高于正常皮肤组织；通过Mannosidase阻断CL-11与肿瘤细胞、巨噬细胞表面Mannosyl位点结合，可有效抑制小鼠皮下移植瘤生长。本课题首次阐明了CL-11通过促进肿瘤细胞增殖与调控肿瘤微环境中巨噬细胞功能以促进肿瘤生长的双重作用机制，进一步发展了凝集素参与肿瘤免疫调控的理论，为后续转化医学研究提供依据。