KIAA1199通过PP2A/Stathmin途径介导微管失稳促进结肠癌细胞转移的机制研究

肿瘤转移是晚期结肠癌患者死亡的主要原因之一，其具体机制尚不明确。我们前期通过基因芯片筛选发现，KIAA1199在结肠癌转移灶中的表达明显高于原发灶；临床分析显示其高表达是影响结肠癌转移和预后不良的因素之一；体内外研究表明该蛋白可促进结肠癌细胞转移，但其机制尚不清楚。我们预实验发现KIAA1199与蛋白磷酸酶PP2A结合，PP2A同时也与微管相关蛋白Stathmin结合，且敲低KIAA1199可增加磷酸化Stathmin蛋白表达。据报道非磷酸化Stathmin导致微管解聚，与肿瘤细胞转移密切相关。因此，我们推测KIAA1199通过PP2A/Stathmin途径介导微管失稳从而促进结肠癌细胞转移。本研究拟通过体外实验、小鼠原位瘤转移模型、蛋白相互作用及分子机制等研究，阐明KIAA1199促进结肠癌细胞转移的作用机制，并揭示紫杉醇对KIAA1199功能的抑制作用，为治疗结肠癌转移提供研究基础。

Metastasis is one of the leading causes of death from advanced colon cancer. However, the mechanism of metastasis has not been elucidated. Identifying the involved metastatic biomarkers and clarifying the regulation mechanisms are of great importance for targeting tumor metastasis. In our previous research, we discovered that KIAA1199, a cell-migration inducing protein, showed higher expression in metastatic tissues compared with the paired primary tissues, was upregulated in colon cancer and positively correlated with tumor metastasis, and predicted poorer outcomes. Moreover, we indicated that down-regulation of KIAA1199 suppressed migration and invasion of colon cancer cells in vitro, and inhibited metastasis of colon cancer cells in vivo. However, the mechanisms by which KIAA1199 promotes metastasis in colon cancer need to be further explored. In our previous research, we identified the interaction between KIAA1199 and PP2A by co-immunoprecipitation and mass spectrometry. Meanwhile, we found that PP2A also bound to stathmin, a microtubule-associated protein. Moreover, our results indicated that the expression of phosphorylated stathmin increased while KIAA1199 expression was down-regulated. PP2A was reported to induce microtubule depolymerization by regulating dephosphorylation of stathmin, which was closely associated with metastasis of tumor cells. Therefore, we deduce that KIAA1199 might promote metastasis of colon cancer cells through microtubule destabilization regulated by PP2A/Stathmin pathway, which has not been reported. In the current research, we will (i) perform in vitro experiments, (ii) establish the orthotopic transplantation tumor and metastasis model of human colon cancer in NOD/SCID mice, and (iii) identify protein interaction and the molecular mechanism, to elucidate the mechanism by which KIAA1199 promotes metastasis of colon cancer cells, and to reveal the inhibiting effect of paclitaxel on the function of KIAA1199. This project will provide a new theoretical foundation for the treatment of colon cancer metastasis.