The Mechanism Of KIAA1199 Promoting Metastasis Of Colon Cancer Cells

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 the current research,we established the orthotopic transplantation tumor and metastasis model of human colon cancer in NOD/SCID mice,and found that down-regulation of KIAA1199 could inhibit metastasis of colon cancer cells.Moreover,we identified the interaction between KIAA1199 and PP2A by co-immunoprecipitation and mass spectrometry.Protein Phosphatase 2A(PP2A),a major serine/threonine phosphatase in cells,functions in many of the major cell signaling pathways,including those that regulate the cell cycle,cell metabolism,cell migration and cell survival.After pull-down and phosphatase activity assay,KIAA1199 was identified to bind to PP2A through its C-terminus,leading to up-regulated PP2A phosphatase activity.Besides,we demonstrated that PP2A inhibitor could inhibit the ability of KIAA1199 in promoting the invasion and migration of colon cancer cells.Furthermore,Stathmin was indicated to be a downstream substrate for the KIAA1199/PP2A complex by immunoprecipitation(IP:PP2A Ca).Stathmin is a microtubule-destabilizing phosphoprotein,and its overexpression correlated with tumor metastasis and poor prognosis in a variety of tumors.In the current research,we found that overexpression of KIAA1199 reduced the expression of phosphorylated Stathmin and regulated its subcellular redistribution.Moreover,KIAA1199 expression was indicated to be negatively correlated with phosphorylated Stathmin protein(Ser-16)in colon cancer.Down-regulation of Stathmin by siRNA could inhibit the ability of KIAA1199 in promoting the invasion and migration of colon cancer cells.Therefore,we concluded that the PP2A/Stathmin pathway was essential for KIAA1199 to promote metastasis of colon cancer.In addition,microtubules are composed of α/α-tubulin heterodimers,while unphosphorylated stathmin binds and sequesters tubulin dimers,forming a T2S complex and thereby reducing the substrate for growing microtubule polymers,thus indirectly leading to microtubule destabilization.In the current research,we observed that overexpression of KIAA1199 reduced the expression of acetylated tubulin,and led to microtubule instability.We also demonstrated that paclitaxel(a chemotherapy drug contributing microtubule stability)could inhibit the function of KIAA1199 in promoting metastasis of colon cancer cells in vitro and in vivo.In conclusion,our research elucidated that KIAA1199 promoted the metastasis of colon cancer cells through microtubule destabilization regulated by PP2A/Stathmin pathway,which has not been reported,and revealed the inhibiting effect of paclitaxel on the function of KIAA1199.These findings highlight KIAA1199 as a possible biomarker of colon cancer metastasis,and as a potential target for novel antitumoral therapies.