Inhibition of AP-1 Reduces CD46-mediated Invasion of Bladder and Colon Cancer Cells

CD46 is a membrane cofactor protein (MCP) essential for several physiological and pathological processes, including tumorigenesis and metastasis. In our previous studies, CD46 increased the production of matrix metalloproteinase 9 (MMP9) in bladder cancer cells by activating the p38 MAPK and PI3K/AKT signaling pathways. CD46 ultimately activated the phosphorylation of the AP-1 complex to stimulate the expression of MMP9. In this study, we assessed whether the inhibition of AP-1 suppresses cancer cell migration and invasion via the inactivation of MMP9.

Both bladder and colon cancer cells were used for western blot analysis and reporter transcription assays. AP-1 inhibitors used are AP-1 decoy oligonucleotide (AP1-ODN) and AP-1 specific inhibitor (SR11302). To test AP-1-mediated inhibition of cell migration and invasion, both wound healing scratch assay and transwell chamber assays with or without gelatin coating were utilized.

Both inhibitors significantly reduced the expression levels of MMP9, especially in CD46-overexpressing UM-UC-3 and 5637 bladder cancer cells. A reporter transcription assay also revealed the suppression of MMP9 promoter activity by AP-1 inhibitors. As expected, AP-1 inhibitors significantly reduced the migration and invasion of bladder cancer cells. CD46 overexpression also promoted the expression of MMP9 through regulation of p38 and AKT in some colon cancer cells (CRCs), including HCT116, CT26, MC38, and DLD-1. Moreover, SR11302 reduced the metastatic potential of colon cancer in vitro and in vivo.

Targeting AP-1 can effectively suppress CD46-mediated invasion and metastasis in bladder and colon cancers, in which CD46 is generally overexpressed.