IGFBP-2 acts as a tumour suppressor and plays a role in determining chemosensitivity in bladder cancer cells

There are mixed reports on the role that IGFBP-2 plays in cancer progression, with some indicating a tumour suppressive role and others showing that IGFBP-2 may act as an oncogene. These apparent contradictions may be context and tissue specific. In this study we determined the role that IGFBP-2 played on the phenotype and chemosensitivity of a selection of bladder cancer cell lines and investigated how the abundance of IGFBP-2 was regulated. We found that IGFBP-2 was more abundant in the epithelial bladder cancer cells, RT4 and UMUC3 and absent in the more mesenchymal T24 and TCCSUP cells. Silencing IGFBP-2 using siRNA in epithelial RT4 cells promoted cell proliferation, invasion, colony formation, resulted in a reduction in epithelial (E-cadherin) and an increase in mesenchymal (N-cadherin) markers and increased sensitivity to cisplatin-induced cell death. Conversely, we observed the opposite effects when adding exogenous IGFBP-2 to the mesenchymal T24 cells. We determined that IGFBP-2 was epigenetically silenced via DNA methylation as the cells adopted a mesenchymal phenotype. Collectively these data suggest that IGFBP-2 acts as a tumour suppressor and marker of chemosensitivity in epithelial bladder cancer cells and that IGFBP-2 is epigenetically silenced by methylation to promote bladder cancer progression.