Bone morphogenetic protein (BMP) receptor inhibitor JL5 synergizes with Ym155 to induce AIF-caspase independent cell death.

Abstract Background: BMP is an evolutionary conserved morphogen that is reactivated in lung carcinomas. BMP receptor inhibitors promote cell death of lung carcinomas by mechanisms not fully elucidated. The studies here reveal novel mechanisms by which the “survivin” inhibitor Ym155 in combination with the BMP inhibitor JL5 synergistically induces death of lung cancer cells.Methods: This study examines the mechanism by which Ym155 in combination with JL5 downregulates BMP signaling and induces cell death of non-small cell lung carcinomas (NSCLC) cell lines. Validation experiments were performed on five passage 0 primary NSCLC.Results: We found that Ym155, which is reported to be a survivin inhibitor, potently inhibits BMP signaling by causing BMPR2 mislocalization into the cytoplasm and its decreased expression. Ym155 mediated cell death is not caused by the inhibition of survivin but involves Ym155 binding to mitochondrial DNA leading to depletion of ATP. The combination of Ym155 and the BMP receptor inhibitor JL5 synergistically causes the downregulation of BMP Smad-1/5 dependent and independent signaling and the induction of cell death of lung cancer cell lines and primary lung tumors. Cell death involves the nuclear translocation of apoptosis inducing factor (AIF) from the mitochondria to the nucleus causing DNA double stranded breaks independent of caspase activation, which occurs only when JL5 and Ym155 are used in combination. Knockdown of BMPR2 together with Ym155 also induced AIF localization to the nucleus.Conclusions: These studies suggest that inhibition of BMPR2 together with Ym155 can induce AIF caspase-independent cell death. AIF caspase-independent cell is an evolutionary conserved cell death pathway that has never been targeted to induce cell death in cancer cells. These studies provide mechanistic insight how to target AIF caspase-independent cell death using BMP inhibitors.