BMP signaling suppresses Gemc1 expression and ependymal differentiation of mouse telencephalic progenitors

The lateral ventricles of the adult mammalian brain are lined by a single layer of multiciliated ependymal cells, which generate a flow of cerebrospinal fluid through directional beating of their cilia as well as regulate neurogenesis through interaction with adult neural stem cells. Ependymal cells are derived from a subset of embryonic neural stem-progenitor cells (NPCs, also known as radial glial cells) that becomes postmitotic during the late embryonic stage of development. Members of the Geminin family of transcriptional regulators including GemC1 and Mcidas play key roles in the differentiation of ependymal cells, but it remains largely unclear what extracellular signals regulate these factors and ependymal differentiation during embryonic and early-postnatal development. We now show that the levels of Smad1/5/8 phosphorylation and Id1/4 protein expression—both of which are downstream events of bone morphogenetic protein (BMP) signaling—decline in cells of the ventricular-subventricular zone in the mouse lateral ganglionic eminence in association with ependymal differentiation. Exposure of postnatal NPC cultures to BMP ligands or to a BMP receptor inhibitor suppressed and promoted the emergence of multiciliated ependymal cells, respectively. Moreover, treatment of embryonic NPC cultures with BMP ligands reduced the expression level of the ependymal marker Foxj1 and suppressed the emergence of ependymal-like cells. Finally, BMP ligands reduced the expression levels of Gemc1 and Mcidas in postnatal NPC cultures, whereas the BMP receptor inhibitor increased them. Our results thus implicate BMP signaling in suppression of ependymal differentiation from NPCs through regulation of Gemc1 and Mcidas expression during embryonic and early-postnatal stages of mouse telencephalic development.

BMP signaling is a therapeutic target in ovarian cancer

BMP signaling has been found to have tumor-promoting as well as tumor-suppressing effects in different types of tumors. In this study, we investigated the effects of BMP signaling and of BMP inhibitors on ovarian cancer (OC) cells in vitro and in vivo. High expression of BMP receptor 2 (BMPR2) correlated with poor overall survival of OC patients in the TCGA dataset. Both BMP2 and BMPR2 enhanced OC cell proliferation, whereas BMP receptor kinase inhibitors inhibited OC cell growth in cell culture as well as in a mouse model. BMP2 also augmented sphere formation, migration, and invasion of OC cells, and induced EMT. High BMP2 expression was observed after chemotherapy of OC patients in the GSE109934 dataset. In accordance, carboplatin, used for the treatment of OC patients, increased BMP2 secretion from OC cells, and induced EMT partially via activation of BMP signaling. Our data suggest that BMP signaling has tumor-promoting effects in OC, and that BMP inhibitors might be useful therapeutic agents for OC patients. Considering that carboplatin treatment augmented BMP2 secretion, the possibility to use a combination of BMP inhibitors and carboplatin in the treatment of OC patients, would be worth exploring.

R-spondins are BMP receptor antagonists in Xenopus early embryonic development

BMP signaling plays key roles in development, stem cells, adult tissue homeostasis, and disease. How BMP receptors are extracellularly modulated and in which physiological context, is therefore of prime importance. R-spondins (RSPOs) are a small family of secreted proteins that co-activate WNT signaling and function as potent stem cell effectors and oncogenes. Evidence is mounting that RSPOs act WNT-independently but how and in which physiological processes remains enigmatic. Here we show that RSPO2 and RSPO3 also act as BMP antagonists. RSPO2 is a high affinity ligand for the type I BMP receptor BMPR1A/ALK3, and it engages ZNRF3 to trigger internalization and degradation of BMPR1A. In early Xenopus embryos, Rspo2 is a negative feedback inhibitor in the BMP4 synexpression group and regulates dorsoventral axis formation. We conclude that R-spondins are bifunctional ligands, which activate WNT- and inhibit BMP signaling via ZNRF3, with implications for development and cancer.

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

Background: Bone morphogenetic protein (BMP) is an evolutionarily 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 receptor 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 carcinoma (NSCLC) cell lines. Validation experiments were performed on five passage 0 primary NSCLC cell lines.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. 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. This causes DNA double stranded breaks independent of caspase activation, which occur 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 evolutionarily conserved cell death pathway that has never been targeted to induce cell death in cancer cells. These studies provide mechanistic insight of how to target AIF caspase-independent cell death using BMP inhibitors.

R-spondins are BMP receptor antagonists in early embryonic development

ABSTRACTBMP signalling plays key roles in development, stem cells, adult tissue homeostasis, and disease. How BMP receptors are extracellularly modulated and in which physiological context, is therefore of prime importance. R-spondins (RSPOs) are a small family of secreted proteins that co-activate WNT signalling and function as potent stem cell effectors and oncogenes. Evidence is mounting that RSPOs act WNT-independently but how and in which physiological processes remains enigmatic. Here we show that RSPO2 and RSPO3 also act as BMP antagonists. RSPO2 is a high affinity ligand for the type I BMP receptor BMPR1A/ALK3, and it engages ZNRF3 to trigger internalization and degradation of BMPR1A. In early Xenopus embryos, Rspo2 is a negative feedback inhibitor in the BMP4 synexpression group and regulates dorsoventral axis formation. We conclude that R-Spondins are bifunctional ligands, which activate WNT- and inhibit BMP signalling via ZNRF3, with implications for development and cancer.

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

Background: Bone morphogenetic protein (BMP) is an evolutionarily 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 receptor 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 carcinoma (NSCLC) cell lines. Validation experiments were performed on five passage 0 primary NSCLC cell lines. 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. 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. This causes DNA double stranded breaks independent of caspase activation, which occur 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 evolutionarily conserved cell death pathway that has never been targeted to induce cell death in cancer cells. These studies provide mechanistic insight of how to target AIF caspase-independent cell death using BMP inhibitors.