C-terminal binding protein-2 promotes cell proliferation and migration in breast cancer via suppression of p16(INK4A)

C-terminal binding protein-2 (CtBP2) enhances cancer proliferation and metastasis. The role and mechanism of CtBP2 in breast cancer remains to be elucidated. Western blot and immunochemistry were employed to evaluate the level of CtBP2 and p16(INK4A) in breast cancer. Genetic manipulation was used to study the expression of p16(INK4A) and its downstream genes regulated by CtBP2. Functional assays, including colony formation, wound healing, transwell invasion, anchorage-independent growth assay and a xenograft tumor model were used to determine the oncogenic role of CtBP2 in breast cancer progression. The expression of CtBP2 was increased in breast cancer tissues and cell lines. The expression of p16(INK4A) were inversely correlated CtBP2 (r(2) = 0.43, P < 0.01). The expression of both CtBP2 and p16(INK4A) were significantly related to histological differentiation (P < 0.01 and P = 0.004, respectively) and metastasis (P = 0.046 and 0.047, respectively). The overall survival rate was lower in patients with increased CtBP2 expression and lower p16(INK4A) expression. Knockdown of CtBP2 resulted in the activation of p16(INK4A) and down–regulation of cell cycle regulators cyclin D, cyclin E and cyclin-dependent kinase 2 and 4. This down-regulation also led to a decreased transition of the G1-S phase in breast cancer cells. Moreover, gain-of-function experiments showed that CtBP2 suppressed p16(INK4A) and matrix metalloproteinase-2, subsequently enhancing the migration in breast cancer. However, the silence of CtBP2 abrogated this effect. Collectively, these findings provide insight into the role CtBP2 plays in promoting proliferation and migration in breast cancer by the inhibition of p16(INK4A).