CTNNA3 and cancer: Therefore, we investigated expression of MMP-9 in CTNNA3 knockdown cells, CTNNA3 overexpression cells and control cells with and without 12-O-tetradecanoylphorbol- 13-Acetate (TPA) treatment, which is an activator of protein kinase C that can promote cancer cell invasion via MMP-9 induction [26].