Transforming growth factor ␤ (TGF-␤) is a potent multifunctional regulator of cell growth and differentiation. Although nearly all cells synthesize and respond to TGF-␤, bone and cartilage are particularly rich in this growth factor (6, 46). TGF-␤1, the prototypic member of the TGF-␤ superfamily, elicits diverse cellular responses, including (i) inhibition of adipogenesis and myogenesis and (ii) stimulation of chondrogenesis and osteogenesis (31). TGF-␤1 stimulates the synthesis of matrix proteins and their receptors (for example, fibronectin, fibronectin receptor, collagen, osteonectin, osteopontin, and integrins) and inhibits matrix degradation by increasing the production of protease inhibitors and decreasing the production of proteases (42). Members of the TGF-␤ superfamily with important effects on bone cell differentiation are bone morphogenetic proteins (BMPs) (17, 41), which were first identified as factors that induce bone formation in vivo when implanted into muscular tissues (54). Unlike TGF-␤, which induces new bone formation only when injected near bone, BMPs produce bone formation even when injected into ectopic sites. TGF-␤ and BMPs bind to distinct receptors, TGF-␤ type I and II receptors for TGF-␤ and BMP type I and II receptors for BMPs. Following ligand binding, the receptor-associated kinase is activated and phosphorylates Smads, which move into the nucleus to stimulate the transcription of a set of target genes. Smad2 and -3 are activated by TGF-␤ receptors and mediate TGF-␤ responses, whereas Smad1, -5, and -8 are activated by BMP receptors and transduce BMP signals (15,32,57).The pluripotent mesenchymal precursor cell line C2C12 provides a model system to study the early stage of osteoblast differentiation during bone formation in muscular tissues. In this model, TGF-␤1 inhibits the differentiation of C2C12 cells into multinucleated myotubes without inducing osteoblast phenotypes. BMP-2 not only inhibits the terminal differentiation of C2C12 cells but also induces osteoblast phenotypes (20). Therefore, the C2C12 model is useful for analyzing both the common and specific signaling mechanisms of TGF-␤ and BMPs. In C2C12 cells, overexpression of Smad1 and Smad5 induced alkaline phosphatase (ALP) activity, a typical osteoblast-specific marker, and inhibited muscle-specific gene expression (11,36,56). These results suggested that BMP functions via either Smad1 or Smad5 and that the induction of the osteoblast phenotype and the inhibition of myogenic differentiation are regulated at the transcriptional level. However, the molecular mechanisms through which Smads block myogenic differentiation and induce osteogenic differentiation are not known.Runx/PEBP2/Cbf (hereafter referred to as Runx) is a sequence-specific DNA binding protein that recognizes a specific DNA sequence originally identified as the binding site for

RUNX proteins belong to a family of metazoan transcription factors that serve as master regulators of development. They are frequently deregulated in human cancers, indicating a prominent and, at times, paradoxical role in cancer pathogenesis. The contextual cues that direct RUNX function represent a fast-growing field in cancer research and could provide insights that are applicable to early cancer detection and treatment. This Review describes how RUNX proteins communicate with key signalling pathways during the multistep progression to malignancy; in particular, we highlight the emerging partnership of RUNX with p53 in cancer suppression.

BackgroundWhile several molecular markers of bladder cancer prognosis have been identified, the limited value of current prognostic markers has created the need for new molecular indicators of bladder cancer outcomes. The aim of this study was to identify genetic signatures associated with disease prognosis in bladder cancer.ResultsWe used 272 primary bladder cancer specimens for microarray analysis and real-time reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Microarray gene expression analysis of randomly selected 165 primary bladder cancer specimens as an original cohort was carried out. Risk scores were applied to stratify prognosis-related gene classifiers. Prognosis-related gene classifiers were individually analyzed with tumor invasiveness (non-muscle invasive bladder cancer [NMIBC] and muscle invasive bladder cancer [MIBC]) and prognosis. We validated selected gene classifiers using RT-PCR in the original (165) and independent (107) cohorts. Ninety-seven genes related to disease progression among NMIBC patients were identified by microarray data analysis. Eight genes, a progression-related gene classifier in NMIBC, were selected for RT-PCR. The progression-related gene classifier in patients with NMIBC was closely correlated with progression in both original and independent cohorts. Furthermore, no patient with NMIBC in the good-prognosis signature group experienced cancer progression.ConclusionsWe identified progression-related gene classifier that has strong predictive value for determining disease outcome in NMIBC. This gene classifier could assist in selecting NMIBC patients who might benefit from more aggressive therapeutic intervention or surveillance.

Runx2/Cbfa1/Pebp2aA is a global regulator of osteogenesis and is crucial for regulating the expression of bone-specific genes. Runx2 is a major target of the bone morphogenetic protein (BMP) pathway. Genetic analysis has revealed that Runx2 is degraded through a Smurf-mediated ubiquitination pathway, and its activity is inhibited by HDAC4. Here, we demonstrate the molecular link between Smurf, HDACs and Runx2, in BMP signaling. BMP-2 signaling stimulates p300-mediated Runx2 acetylation, increasing transactivation activity and inhibiting Smurf1-mediated degradation of Runx2. HDAC4 and HDAC5 dea-cetylate Runx2, allowing the protein to undergo Smurf-mediated degradation. Inhibition of HDAC increases Runx2 acetylation, and potentiates BMP-2-stimulated osteoblast differentiation and increases bone formation. These results demonstrate that the level of Runx2 is controlled by a dynamic equilibrium of acetylation, deacetylation, and ubiquitination. These findings have important medical implications because BMPs and Runx2 are of tremendous interest with regard to the development of therapeutic agents against bone diseases.

Dorsal root ganglion (DRG) neurons specifically project axons to central and peripheral targets according to their sensory modality. The Runt-related genes Runx1 and Runx3 are expressed in DRG neuronal subpopulations, suggesting that they may regulate the trajectories of specific axons. Here we report that Runx3-deficient (Runx3(-/-)) mice displayed severe motor uncoordination and that few DRG neurons synthesized the proprioceptive neuronal marker parvalbumin. Proprioceptive afferent axons failed to project to their targets in the spinal cord as well as those in the muscle. NT-3-responsive Runx3(-/-) DRG neurons showed less neurite outgrowth in vitro. However, we found no changes in the fate specification of Runx3(-/-) DRG neurons or in the number of DRG neurons that expressed trkC. Our data demonstrate that Runx3 is critical in regulating the axonal projections of a specific subpopulation of DRG neurons.