Upregulation of the Oct3/4 Network in Basal Breast Cancer Is Associated with Its Metastatic Potential and Shows Tissue Dependent Variability.

Adaptive plasticity of Breast Cancer stem cells (BCSCs) is strongly correlated with cancer progression and resistance, leading to a poor prognosis. In this study, we report the expression profile of several pioneer transcription factors of the network associated with tumor initiation and metastasis. In the triple negative breast cancer cell line (MDA-MB-231) stably transfected with human Oct3/4-GFP, differentially expressed genes (DEGs) were identified using qPCR and microarray, and the resistance to paclitaxel was assessed using an MTS assay.

Gliomagenesis is orchestrated by the Oct3/4 regulatory network.

Background: Glioblastoma multiforme (GBM) is a lethal brain tumor characterized by developmental hierarchical phenotypic heterogeneity, therapy resistance and recurrent growth. Neural stem cells (NSCs) from human central nervous system (CNS), and glioblastoma stem cells from patient-derived GBM (pdGSC) samples were cultured in both 2D well-plate and 3D monoclonal neurosphere culture system (pdMNCS). The pdMNCS model shows promise to establish a relevant 3D-tumor environment that maintains GBM cells in the stem cell phase within suspended neurospheres.

Sh3rf2/POSHER protein promotes cell survival by ring-mediated proteasomal degradation of the c-Jun N-terminal kinase scaffold POSH (Plenty of SH3s) protein.

We report that Sh3rf2, a homologue of the pro-apoptotic scaffold POSH (Plenty of SH3s), acts as an anti-apoptotic regulator for the c-Jun N-terminal kinase (JNK) pathway. siRNA-mediated knockdown of Sh3rf2 promotes apoptosis of neuronal PC12 cells, cultured cortical neurons, and C6 glioma cells. This death appears to result from activation of JNK signaling.

Identification of POSH2, a novel homologue of the c-Jun N-terminal kinase scaffold protein POSH.

The c-Jun N-terminal kinase (JNK) pathway plays an important role in neuronal apoptosis both during normal CNS development and following stroke in adult animals. As with other MAP kinase pathways, scaffold proteins regulate JNK signaling. The scaffold protein POSH (Plenty of SH3s) enhances JNK activation and apoptosis.

Proapoptotic Nix activates the JNK pathway by interacting with POSH and mediates death in a Parkinson disease model.

Nix, a pro-apoptotic BH3-only protein, promotes apoptosis of non-neuronal cells, although the mechanisms involved remain incompletely understood. Using a yeast two-hybrid screen with POSH (plenty of SH3 domains, a scaffold involved in activation of the apoptotic JNK/c-Jun pathway) as the bait, we identified an interaction between POSH and Nix. Co-immunoprecipitation and in vitro binding studies confirmed a direct interaction between POSH and Nix in mammalian cells.

Direct interaction of the molecular scaffolds POSH and JIP is required for apoptotic activation of JNKs.

A sequential pathway (the JNK pathway) that includes activation of Rac1/Cdc42, mixed lineage kinases, MAP kinase kinases 4 and 7, and JNKs plays a required role in many paradigms of apoptotic cell death. However, the means by which this pathway is assembled and directed toward apoptotic death has been unclear. Here, we report that propagation of the apoptotic JNK pathway requires the cooperative interaction of two molecular scaffolds, POSH and JIPs.

Regulation of apoptotic c-Jun N-terminal kinase signaling by a stabilization-based feed-forward loop.

A sequential kinase cascade culminating in activation of c-Jun N-terminal kinases (JNKs) plays a fundamental role in promoting apoptotic death in many cellular contexts. The mechanisms by which this pathway is engaged in response to apoptotic stimuli and suppressed in viable cells are largely unknown. Here, we show that apoptotic stimuli increase endogenous cellular levels of pathway components, including POSH, mixed lineage kinases (MLKs), and JNK interacting protein 1, and that this effect occurs through protein stabilization and requires the presence of POSH as well as activation of MLKs and JNKs.

Siah1 interacts with the scaffold protein POSH to promote JNK activation and apoptosis.

Siah proteins are ubiquitin-protein isopeptide ligases (E3) that have been implicated in a variety of cellular actions, including promotion of apoptotic death. Here, we show that Siah1 is a binding partner for POSH (plenty of SH3s), a scaffold component of the apoptotic JNK pathway, and that Siah contributes to death of neurons and other cell types by activating the JNK pathway. Such proapoptotic activity requires the E3 ligase activity of Siah1.

POSH acts as a scaffold for a multiprotein complex that mediates JNK activation in apoptosis.

We report that the multidomain protein POSH (plenty of SH3s) acts as a scaffold for the JNK pathway of neuronal death. This pathway consists of a sequential cascade involving activated Rac1/Cdc42, mixed-lineage kinases (MLKs), MAP kinase kinases (MKKs) 4 and 7, c-Jun N-terminal kinases (JNKs) and c-Jun, and is required for neuronal death induced by various means including nerve growth factor (NGF) deprivation. In addition to binding GTP-Rac1 as described previously, we find that POSH binds MLKs both in vivo and in vitro, and complexes with MKKs 4 and 7 and with JNKs.

The MLK family mediates c-Jun N-terminal kinase activation in neuronal apoptosis.

Neuronal apoptotic death induced by nerve growth factor (NGF) deprivation is reported to be in part mediated through a pathway that includes Rac1 and Cdc42, mitogen-activated protein kinase kinases 4 and 7 (MKK4 and -7), c-Jun N-terminal kinases (JNKs), and c-Jun. However, additional components of the pathway remain to be defined. We show here that members of the mixed-lineage kinase (MLK) family (including MLK1, MLK2, MLK3, and dual leucine zipper kinase [DLK]) are expressed in neuronal cells and are likely to act between Rac1/Cdc42 and MKK4 and -7 in death signaling.