Impact of TIMP-1 in the host microenvironment on modification of the new prognostic marker L1CAM during liver metastasis

本项目旨在建立细胞粘附分子L1CAM、天然金属蛋白酶抑制剂TIMP-1和脱落酶ADAM-10之间的功能关系。肿瘤细胞上L1CAM的高表达和宿主体内TIMP-1的高表达与癌症患者预后不良和促进肿瘤细胞转移有关。ADAM-10是已知的L1CAM的脱落酶，被发现被TIMP-1抑制。在此基础上，我们假设TIMP-1的系统水平升高，然后也存在于肿瘤细胞的微环境中，通过抑制ADAM-10的脱落酶功能来稳定肿瘤细胞表面上L1CAM的存在，从而有助于肿瘤细胞转移潜力的增加。首先，我们的目的是在体外研究肿瘤细胞暴露于外源性重组TIMP-1是否通过抑制肿瘤细胞表面的ADAM-10来诱导L1CAM蛋白。下一步，我们的目标是在宿主体内系统地提高TIMP-1水平，并研究之前观察到的实验性转移的促进是否与肿瘤细胞上的L1CAM表达有关。此外，我们的目的是研究TIMP-1对ADAM-10的抑制是否会通过增加未被TIMP-1抑制的替代L1CAM脱落酶ADAM-17和Plasmin的表达和功能活性而导致补偿，以及这种复杂蛋白水解网络中的补偿是否会在体内产生影响。由于转移似乎总是依赖于HGF/Met信号通路活性的增加，并且我们发现该通路介导了生物体中外源TIMP-1水平升高的转移促进作用，因此我们旨在阐明L1CAM对基因表达水平的可能调节。我们之前发现的timp -1诱导的细胞表面Met的稳定可能会触发L1CAM的基因表达。阐明TIMP-1与L1CAM在肿瘤转移过程中的相互作用，将为开发新的恶性肿瘤治疗方法提供重要线索。

In this project we aim for establishing a functional relationship between the cell adhesion molecule L1CAM, the natural metalloprotease inhibitor TIMP-1 and the Sheddase ADAM-10. High expression levels of L1CAM on tumor cells and high systemic levels of TIMP-1 in the host are associated with bad prognosis of cancer patients and promotion of tumor cell metastasis. ADAM-10 is a known sheddase of L1CAM and was found to be inhibited by TIMP-1. On this basis we hypothesize that elevated systemic levels of TIMP-1, which then are present also in the microenvironment of the tumor cell, contribute to increase of the metastatic potential of tumor cells by stabilizing the cell surface presence of L1CAM on the tumor cell surface by inhibiting the sheddase function of ADAM-10. First, we aim to investigate in vitro whether exposure of tumor cells to exogenous recombinant TIMP-1 induces L1CAM protein, via inhibition of ADAM-10, at the tumor cell surface. In the next step, we aim to elevate TIMP-1 levels systemically in the host and investigate, whether the previously observed promotion of experimental metastasis correlates with L1CAM expression on the tumor cells. Further, we aim to investigate whether inhibition of ADAM-10 by TIMP-1 leads to compensation by increasing the expression and functional activity of the alternative L1CAM sheddases, ADAM-17 and Plasmin, which are not inhibited by TIMP-1 and whether this compensation within the complex proteolytic network has consequences in vivo. Since metastasis seems to almost always rely on the increased activity of the HGF/Met signalling pathway and we found that this pathway mediates the metastasis-promoting effect of elevated exogenous TIMP-1 levels in the organism, we aim to elucidate a possible regulation of L1CAM on the gene expression level. The TIMP-1-induced stabilization of Met at the cell surface that we had previously found may trigger gene expression of L1CAM. Elucidation of the interplay between TIMP-1 and L1CAM during metastasis will provide important hints for the development of new therapies of malignant tumors.