TGF-β Signaling in Breast Cancer Cell Invasion and Bone Metastasis

The contribution of transforming growth factor β (TGF-β) signaling to breast cancer has been studied for more than two decades. In an early phase TGF-β may act as a tumour suppressor, while later, when cells have become resistant to its anti-mitogenic effects, the role of TGF-β switches towards malignant conversion and progression. TGF-β stimulates cell invasion and modifies the microenvironment to the advantage of cancer cells. Studies have shown that TGF-β promotes bone and lung metastasis via different mechanisms. The therapeutic strategies to target the TGF-β pathway in breast cancer are becoming increasingly clear. This review will focus on the role TGF-β in breast cancer invasion and metastasis

TGFβ Signaling and Cardiovascular Diseases

Transforming growth factor β (TGFβ) family members are involved in a wide range of diverse functions and play key roles in embryogenesis, development and tissue homeostasis. Perturbation of TGFβ signaling may lead to vascular and other diseases. In vitro studies have provided evidence that TGFβ family members have a wide range of diverse effects on vascular cells, which are highly dependent on cellular context. Consistent with these observations genetic studies in mice and humans showed that TGFβ family members have ambiguous effects on the function of the cardiovascular system. In this review we discuss the recent advances on TGFβ signaling in (cardio)vascular diseases, and describe the value of TGFβ signaling as both a disease marker and therapeutic target for (cardio)vascular diseases

Elevated transforming growth factor β and mitogen-activated protein kinase pathways mediate fibrotic traits of Dupuytren's disease fibroblasts

ABSTRACT: Dupuytren's disease is a fibroproliferative disorder of the palmar fascia. The treatment used to date has mostly been surgery, but there is a high recurrence rate. Transforming growth factor β (TGF-β) has been implicated as a key stimulator of myofibroblast activity and fascial contraction in Dupuytren's disease. We studied Dupuytren's fibroblasts in tissues ex vivo and in cells cultured in vitro and found increased TGF-β expression compared to control fibroblasts. This correlated not only with elevated expression and activation of downstream Smad effectors but also with overactive extracellular signal-regulated kinase 1/2 (ERK1/2)/mitogen-activated protein (MAP) kinase signalling. Treatment with the TGF-β type I receptor kinase inhibitor SB-431542 and bone morphogenetic protein 6 (BMP6) led to inhibition of elevated Smad and ERK1/2/MAP kinase signalling as well as to inhibition of the increased contractility of Dupuytren's fibroblasts. BMP6 attenuated TGF-β expression in Dupuytren's fibroblasts, but not in control fibroblasts. Platelet-derived growth factor (PDGF) expression was strongly promoted by TGF-β in Dupuytren's fibroblasts and was curbed by SB-431542 or BMP6 treatment. High basal expression of phosphorylated ERK1/2 MAP kinase and fibroproliferative markers was attenuated in Dupuytren's fibroblasts by a selective PDGF receptor kinase inhibitor. Cotreatment of Dupuytren's fibroblasts with SB-431542 and the mitogen-activated protein kinase kinase 1 inhibitor PD98059 was sufficient to abrogate proliferation and contraction of Dupuytren's fibroblasts. Both TGF-β and ERK1/2 MAP kinase pathways cooperated in mediating the enhanced proliferation and high spontaneous contraction of Dupuytren's fibroblasts. Our data indicate that both signalling pathways are prime targets for the development of nonsurgical intervention strategies to treat Dupuytren's diseas

Regulatory RNAs controlling vascular (dys)function by affecting TGF-ß family signalling

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality worldwide. Over the last few years, microRNAs (miRNAs) have emerged as master regulators of gene expression in cardiovascular biology and di¬sease. miRNAs are small endogenous non-coding RNAs that usually bind to 3′ untranslated region (UTR) of their target mRNAs and inhibit mRNA stability or translation of their target genes. miRNAs play a dynamic role in the pathophysiology of many CVDs through their effects on target mRNAs in vascular cells. Recently, numerous miRNAs have been implicated in the regulation of the transforming growth factor-β (TGF-β)/bone morphogenetic protein (BMP) signalling pathway which plays crucial roles in diverse biological processes, and is involved in pathogenesis of many diseases including CVD. This review gives an overview of current literature on the role of miRNAs targeting TGF-β/BMP signalling in vascular cells, including endothelial cells and smooth muscle cells. We also provide insight into how this miRNA-mediated regulation of TGF-β/BMP signalling might be used to harness CVD

Molecular characterization of transforming growth factor-beta3

Normal tissue homeostasis is controlled by a critical balance of positive and negative modulators. Chapter 2 gives an overview of the molecular aspects of growth control, in particular the role of growth factors and oncogene and anti-oncogene products. Uncontrolled growth of cancer cells may result from either an abrogation of growth stimulatory or a deficiency of growth inhibitory pathways. Mediators of growth inhibition include secretory polypeptide growth inhibitors, like transforming growth factor β(TGF-β) and nuclear proteins, like the retinoblastoma gene product. Early studies on organogenesis suggested the presence of growth inhibitors (challones) to regulate the growth of organs. Postulating that growth inhibitory proteins might have potential in cancer therapy, we began to analyze human tissues for the presence of novel tumor inhibitory factors. Purification of these activities and physico-chemical characterization suggested a relatedness to TGF-β. The biochemistry and cell biology of (TGF-β) will be reviewed in Chapter 3.At the start of the investigation, only one (TGF-β) had been identified. Our subsequent results indicated that a family of TGF-βproteins exists. Conventional purification of these TGF-βlike activities provided only limited quantities of material for analysis. We therefore adopted an alternative strategy which included the isolation of the cDNAs for TGF-β-like factors using TGF-β1 as a probe, assuming that related molecules might possess sufficient sequence similarity to cross-hybridize to a TGF-β1 probe. Differential hybridization of a Southern blot with human genomic DNA probed with TGF-β1 cDNA suggested the presence of a related gene, which we termed TGF-β3. The research described in this thesis includes the molecular cloning and expression of TGF-β3. Furthermore, experiments were carried out to gain insight into the effects of TGF-β3 on cell growth and differentiation and its mechanism of action, including initial studies to gauge the potential therapeutic uses of this factor.In Chapter 4, we report the cloning of the human TGF-β3 cDNA and the encoded TGF-β3 protein is compared with other members of the TGF-βfamily. In Chapter 5 the interspecies conservation of TGF-B3 is examined and the chromosomal location of the human TGF-β3 gone is determined. In Chapter 6, the recombinant expression and purification of TGF-β3 is described. The purified TGF-β3 protein has potent growth modulating effects on a number of normal as well as tumor cells. The studies in Chapter 7 were performed to assess the effect of TGF-β3 on osteoblasts and to characterize the specific binding of TGF-β3 to bone cells. TGF-β3 appears to be a potent regulator of functions associated with bone formation. Crosslinking studies showed that TGF-β3 and TGF-β1 associate in a similar fashion with three cell surface binding proteins, which have been characterized as putative receptor types I and II and a membrane-bound proteoglycan, termed betaglycan. The different (TGF-β) isoforms appear to have different potencies on Mv1Lu mink lung epithelia] and fetal bovine heart endothelial cells. In Chapter 8, we investigate the role of TGF-β. receptors and serum factors as determinants of the cell-specific responsiveness to the three homodimeric isoforms. The induction of mesoderm in Xenopus laevis animal cap explants by TGF-β3 is discussed in Chapter 9. Finally, in Chapter 10 we review the therapeutic applications of growth factors for wound healing

Towards targeting overactive BMP signaling in Fibrodysplasia Ossificans Progressiva

Fibrodysplasia Ossificans Progressiva (FOP) is a rare monogenetic disorder in which patients develop heterotopic ossification (HO). A heterozygous mutation in BMP type I receptor ALK2 results in hyper-sensitized BMP signaling. The aim of this study is to identify small molecules which can selectively inhibit this overactive BMP pathway. Thirteen FDA-approved small molecules were tested on their effect on BMP6-induced target gene expression, alkaline phosphatase activity and mineralization in KS483 cells. We identified cryptotanshinone as a small molecule able to inhibit BMP signaling. In conclusion, cryptotanshinone could be a novel small molecule inhibitor of the overactive BMP signaling pathway in FOP

Promiscuous signaling of ligands via mutant ALK2 in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare hereditary disorder characterized by successive heterotopic bone formation, for which at present there is no therapy. Mutations in the bone morphogenetic protein (BMP) type I receptor Activin receptor-like kinase 2 (ACVR1/ALK2) are the main trigger for FOP and inflammation is thought to be the secondary hit. The single nucleotide mutation at position 617 in the cDNA ALK2 sequence, which is found in 98% of FOP patients, results in a R206H change in the intracellular juxtamembrane region of ALK2. Previous studies had revealed that this mutation perturbs the interaction with the negative regulator FKBP12, thereby sensitising cells expressing this mutant receptor to BMPs, which are potent inducers of cartilage and bone formation. Recently, however, a twist in the underlying mechanism of FOP was revealed. Mutant ALK2 was found to respond to Activin-A, whereas wild type ALK2 function is inhibited by Activin-A. The latter cytokine is induced locally upon tissue damage and inflammation. Moreover, therapeutic targeting of Activin-A was found to inhibit heterotopic ossification in a mutant ALK2 knock-in mouse model that is highly reminiscent to human FOP. This review will focus on these latest surprising findings and discuss the implication for treatment of FOP patients

Targeting tumour vasculature by inhibiting activin receptor-like kinase (ALK)1 function

Angiogenesis is a hallmark of cancer and is now a validated therapeutic target in the clinical setting. Despite the initial success, anti-angiogenic compounds impinging on the vascular endothelial growth factor (VEGF) pathway display limited survival benefits in patients and resistance often develops due to activation of alternative pathways. Thus, finding and validating new targets is highly warranted. Activin receptor-like kinase (ALK)1 is a transforming growth factor beta (TGF-β) type I receptor predominantly expressed in actively proliferating endothelial cells (ECs). ALK1 has been shown to play a pivotal role in regulating angiogenesis by binding to bone morphogenetic protein (BMP)9 and 10. Two main pharmacological inhibitors, an ALK1-Fc fusion protein (Dalantercept/ACE-041) and a fully human antibody against the extracellular domain of ALK1 (PF-03446962) are currently under clinical development. Herein, we briefly recapitulate the role of ALK1 in blood vessel formation and the current status of the preclinical and clinical studies on inhibition of ALK1 signalling as an anti-angiogenic strategy. Future directions in terms of new combination regimens will also be presented