SB 525334

1 . Laping NJ, Everitt JI, Frazier KS, Burgert M, Portis MJ, Cadacio C, Gold LI, Walker CL.Tumor-specific efficacy of transforming growth factor-beta RI inhibition in Eker rats.Clin Cancer Res. 2007 May 15;13(10):3087-99.
Abstract
PURPOSE: Transforming growth factor beta (TGF-beta), which generally stimulates the growth of mesenchymally derived cells but inhibits the growth of epithelial cells, has been proposed as a possible target for cancer therapy. However, concerns have been raised that whereas inhibition of TGF-beta signaling could be efficacious for lesions in which TGF-beta promotes tumor development and/or progression, systemic pharmacologic blockade of this signaling pathway could also promote the growth of epithelial lesions. EXPERIMENTAL DESIGN: We examined the effect of a TGF-beta inhibitor on mesenchymal (leiomyoma) and epithelial (renal cell carcinoma) tumors in Eker rats, which are genetically predisposed to develop these tumors with a high frequency. RESULTS: Blockade of TGF-beta signaling with the ALK5/type I TGF-beta R kinase inhibitor, SB-525334, was efficacious for uterine leiomyoma; significantly decreasing tumor incidence and multiplicity, and reducing the size of these mesenchymal tumors. However, SB-525334 was also mitogenic and antiapoptotic for epithelial cells in the kidney and exacerbated the growth of epithelial lesions present in the kidneys of these animals. CONCLUSION: Although pharmacologic inhibition of TGF-beta signaling with SB-525334 may be efficacious for mesenchymal tumors, inhibition of this signaling pathway seems to promote the development of epithelial tumors.

2 . Thomas M, Docx C, Holmes AM, Beach S, Duggan N, England K, Leblanc C, Lebret C, Schindler F, Raza F, Walker C, Crosby A, Davies RJ, Morrell NW, Budd DC.Activin-like kinase 5 (ALK5) mediates abnormal proliferation of vascular smooth muscle cells from patients with familial pulmonary arterial hypertension and is involved in the progression of experimental pulmonary arterial hypertension induced by monocrotaline.Am J Pathol. 2009 Feb;174(2):380-9. Epub 2008 Dec 30.
Abstract
Mutations in the gene for the transforming growth factor (TGF)-beta superfamily receptor, bone morphogenetic protein receptor II, underlie heritable forms of pulmonary arterial hypertension (PAH). Aberrant signaling via TGF-beta receptor I/activin receptor-like kinase 5 may be important for both the development and progression of PAH. We investigated the therapeutic potential of a well-characterized and potent activin receptor-like kinase 5 inhibitor, SB525334 [6-(2-tert-butyl-5-{6-methyl-pyridin-2-yl}-1H-imidazol-4-yl)-quinoxaline] for the treatment of PAH. In this study, we demonstrate that pulmonary artery smooth muscle cells from patients with familial forms of idiopathic PAH exhibit heightened sensitivity to TGF-beta1 in vitro, which can be attenuated after the administration of SB525334. We further demonstrate that SB525334 significantly reverses pulmonary arterial pressure and inhibits right ventricular hypertrophy in a rat model of PAH. Immunohistochemical studies confirmed a significant reduction in pulmonary arteriole muscularization induced by monocrotaline (used experimentally to induce PAH) after treatment of rats with SB525334. Collectively, these data are consistent with a role for the activin receptor-like kinase 5 in the progression of idiopathic PAH and imply that strategies to inhibit activin receptor-like kinase 5 signaling may have therapeutic benefit.

3 . Boyd NL, Nunes SS, Jokinen JD, Krishnan L, Chen Y, Smith KH, Stice SL, Hoying JB.Microvascular mural cell functionality of human embryonic stem cell-derived mesenchymal cells.Tissue Eng Part A. 2011 Jun;17(11-12):1537-48. Epub 2011 Mar 4.
Abstract
Microvascular mural or perivascular cells are required for the stabilization and maturation of the remodeling vasculature. However, much less is known about their biology and function compared to large vessel smooth muscle cells. We have developed lines of multipotent mesenchymal cells from human embryonic stem cells (hES-MC); we hypothesize that these can function as perivascular mural cells. Here we show that the derived cells do not form teratomas in SCID mice and independently derived lines show similar patterns of gene expression by microarray analysis. When exposed to platelet-derived growth factor-BB, the platelet-derived growth factor receptor β is activated and hES-MC migrate in response to a gradient. We also show that in a serum-free medium, transforming growth factor β1 (TGFβ1) induces robust expression of multiple contractile proteins (α smooth muscle actin, smooth muscle myosin heavy chain, smooth muscle 22α, and calponin). TGFβ1 signaling is mediated through the TGFβR1/Alk5 pathway as demonstrated by inhibition of α smooth muscle actin expression by treatment of the Alk5-specific inhibitor SB525334 and stable retroviral expression of the Alk5 dominant negative (K232R). Coculture of human umbilical vein endothelial cell (HUVEC) with hES-MC maintains network integrity compared to HUVEC alone in three-dimensional collagen I-fibronectin by paracrine signaling. Using high-resolution laser confocal microscopy, we show that hES-MC also make direct contact with HUVEC. This demonstrates that hESC-derived mesenchymal cells possess the molecular machinery expected in a perivascular progenitor cells and can play a functional role in stabilizing EC networks in in vitro three-dimensional culture.

4 . Kim YJ, Hwang JS, Hong YB, Bae I, Seong YS.Transforming growth factor beta receptor I inhibitor sensitizes drug-resistant pancreatic cancer cells to gemcitabine.Anticancer Res. 2012 Mar;32(3):799-806.
Abstract
BACKGROUND: Resistance to gemcitabine is a major obstacle in the treatment of advanced pancreatic cancer. Previous exploration of protein kinase inhibitors demonstrated that blocking transforming growth factor-β (TGFβ) signal enhances the efficacy of gemcitabine in pancreatic cancer cells. MATERIALS AND METHODS: We analyzed the cell viability after combinational treatment of TGFβ receptor I (TβRI) inhibitors, SB431542 and SB525334 with gemcitabine in pancreatic cancer cells. In addition, apoptotic cell death and cell migration were measured. RESULTS: Combination with TβRI inhibitors significantly augmented the cytotoxicity of gemcitabine in both parental and gemcitabine resistant pancreatic cancer cells. SB525334 significantly increased apoptotic cell death in gemcitabine-resistant cells. Treatment of SB525334 also affected the AKT signalling pathway, which plays a crucial role in gemcitabine resistance. Migration assay also revealed that blocking TβRI reduces cell migration. CONCLUSION: Chemotherapeutic approaches using SB525334 might enhance the treatment benefit of the gemcitabine-containing regimens in the treatment of pancreatic cancer patients.

5 . Laping et al (2007) Tumor-specific efficacy of transforming growth factor-bRI inhibition in eker rats. Clin.Cancer Res. 13 3087.
Abstract
Purpose: Transforming growth factor h (TGF-h), which generally stimulates the growth ofmesenchymally derived cells but inhibits the growth of epithelial cells, has been proposed as apossible target for cancer therapy. However, concerns have been raised that whereas inhibitionof TGF-h signaling could be efficacious for lesions in whichTGF-h promotes tumor developmentand/or progression, systemic pharmacologic blockade of this signaling pathway could alsopromote the growth of epithelial lesions."