结直肠癌细胞分泌组织蛋白酶K诱导肿瘤相关巨噬细胞极化促进肿瘤转移的分子机制

Tumor metastasis is a complex process involved in the interaction between tumor cells and tumor microenvironment. As an important component of tumor microenvironment, the interaction between tumor-associated macrophages (TAMs) and tumor cells in colorectal cancer metastasis is unclear. Our preliminary study successful screened colorectal cancer metastasis-associated candidate gene cathepsin K (CTSK) and initially confirmed its high expression in tumor cells. CTSK could act on stroma cells in the tumor microenvironment by the form of exocrine and participate in the macrophage differentiation process. Based on those, we hypothesized that upregulated CTSK in colorectal cancer cells effect on macrophages in tumor microenvironment through the form of exocrine, activate intracellular signaling pathways, to promote M2-type transformation into TAMs, which secrete a variety of pro-metastasis factors, leading to the invasion and metastasis of colorectal carcinoma. Using molecular pathology and molecular biology methods, from the tumor microenvironment perspective, combined with in vivo and in vitro study, the aim of the project is to systematically illustrate the role of CTSK in CRC metastasis, provide reliable evidences of CTSK mediated by the interaction between tumor cells and tumor microenvironment, and established the scientific basis for establishing CTSK as a novel target for clinical therapy of patients with advanced CRC.

肿瘤转移是肿瘤细胞和肿瘤微环境相互作用的复杂过程。作为肿瘤微环境中的重要组成成分，肿瘤相关巨噬细胞(TAMs)与肿瘤细胞的交互影响在结直肠癌转移中的作用尚不清楚。我们课题组前期研究成功筛选结直肠癌转移候选基因组织蛋白酶K(CTSK)，初步证实其在肿瘤细胞中高表达，可以通过外分泌的形式作用于肿瘤微环境中间质细胞，并参与巨噬细胞分化过程。据此我们提出假设：结直肠癌细胞高表达CTSK，通过外分泌形式作用于肿瘤微环境中巨噬细胞，激活细胞内信号通路，促进其向M2型转化成为TAMs，后者分泌多种促肿瘤转移因子，导致结直肠癌的侵袭和转移。本项目期望通过分子病理及分子生物学方法，从肿瘤微环境的角度，结合体内外研究，全方位阐明CTSK促进结直肠癌转移发生的分子机制，提供CTSK通过与肿瘤微环境中TAMs相互作用从而发挥生物学功能的直接证据，为确立CTSK作为晚期结直肠癌患者临床治疗靶点提供充分的科学依据。

目前研究筛选得到了结直肠癌转移相关分泌蛋白组织蛋白酶K（CTSK）是肠道菌群和肿瘤转移间的关键调节因子。抗菌素处理后的小鼠给予大肠杆菌灌注能通过LPS脂多糖刺激肿瘤细胞分泌CTSK，从而诱导肿瘤肝转移。沉默CTSK表达或者给予CTSK抑制剂Odanacatib处理能消除CTSK诱导的肿瘤细胞侵袭和迁移。而且CTSK可以结合巨噬细胞表面的Toll样受体4（TLR4）刺激其发生M2极化。在TLR4敲除鼠中则观察不到该现象。极化的巨噬细胞能分泌IL10和IL17，反馈作用于肿瘤细胞激活NFkB信号通路，从而形成反馈环路。该研究证实了CTSK介导的肿瘤细胞与肿瘤相关巨噬细胞反馈环路，将为结直肠癌提供新的预测和治疗靶点。本研究共发表SCI论文14篇（中科院小类1区2篇，中科院小类2区11篇），授权国家实用新型专利2件，受理发明专利1件。11名研究生获得硕士或博士学位。项目组1人获得广东省珠江学者特聘教授，1人晋升副教授，3名博士毕业后入站进行博士后研究工作。