Multiple Mechanisms for Anti-Fibrotic Functions of Statins on Radiotherapy Induced Fibrosis
Keywords:CTGF, Statins, Fibrosis, TGF-β, Radiation, Rho/ROCK pathway.
Radiotherapy-induced fibrosis (RTIF) presents a challenge in radiotherapy for cancer patients. Although numerous studies have attempted to elucidate the mechanisms leading to RTIF, the pathogenesis of RTIF at the cellular and molecular level is still incompletely described. One key component involved in the post-radiation injury is the pleuripotent cytokine transforming growth factor (TGF)-β. TGF-β signaling pathway has been under intensive investigation about its critical role in radiation-induced fibroproliferative disease. Connective tissue growth factor (CTGF), also known as insulin-like growth factor binding protein-related protein 2 (IGFBP-rP2) is a potent regulator of fibroblast proliferation, cell adhesion, and stimulation of extracellular matrix production. CTGF is known as a major downstream mediator of the chronic fibrotic effects of TGF-β. Here we have demonstrated that irradiation and TGF-β induced CTGF, subsequently upregulates fibrotic factors such as fibronectin and type IV collagen. Furthermore, as HMG-CoA reductase inhibitors, statins inhibit expressions of CTGF and downstream fibrotic proteins in both normal human fetal fibroblasts (HFL-1) and human dermal fibroblasts (HDF) on TGF-β treatment or irradiation. Our study also demonstrates that simvastatin not only suppressed TGF-β-induced fibrosis through inhibition of CTGF production but also CTGF-induced fibrosis. We further show that simvastatin may act in a TGF-β-independent manner by inhibiting Rho kinase pathway. Taken together, these data suggest that radiotherapy may upregulate CTGF expression in a TGF-β-dependent and -independent manner, thereby enhancing expression of profibrotic factors and inducing lung fibrosis.
Tsoutsou PG, Koukourakis MI. Radiation pneumonitis and fibrosis: mechanisms underlying its pathogenesis and implications for future research. Int J Radiat Oncol Biol Phys 2006; 66: 1281-93. http://dx.doi.org/10.1016/j.ijrobp.2006.08.058
Anscher MS, Chen L, Rabbani Z, et al. Recent progress in defining mechanisms and potential targets for prevention of normal tissue injury after radiation therapy. Int J Radiat Oncol Biol Phys 2005; 62: 255-9. http://dx.doi.org/10.1016/j.ijrobp.2005.01.040
Zhao L, Sheldon K, Chen M, et al. The predictive role of plasma TGF-beta1 during radiation therapy for radiation-induced lung toxicity deserves further study in patients with non-small cell lung cancer. Lung Cancer 2008; 59: 232-9. http://dx.doi.org/10.1016/j.lungcan.2007.08.010
Cicha I, Goppelt-Struebe M. Connective tissue growth factor: context-dependent functions and mechanisms of regulation. Biofactors 2009; 35: 200-8. http://dx.doi.org/10.1002/biof.30
Leask A, Abraham DJ. The role of connective tissue growth factor, a multifunctional matricellular protein, in fibroblast biology. Biochemistry and Cell Biology = Biochimie et Biologie Cellulaire 2003; 81: 355-63. http://dx.doi.org/10.1139/o03-069
Anscher MS, Thrasher B, Rabbani Z, et al. Antitransforming growth factor-beta antibody 1D11 ameliorates normal tissue damage caused by high-dose radiation. Int J Radiat Oncol Biol Phys 2006; 65: 876-81. http://dx.doi.org/10.1016/j.ijrobp.2006.02.051
Brigstock DR. The connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed (CCN) family. Endocr Rev 1999; 20: 189-206.
Haydont V, Mathe D, Bourgier C, et al. Induction of CTGF by TGF-beta1 in normal and radiation enteritis human smooth muscle cells: Smad/Rho balance and therapeutic perspectives. Radiother Oncol: J Eur Soc Therapeut Radiol Oncol 2005; 76: 219-25. http://dx.doi.org/10.1016/j.radonc.2005.06.029
Li G, Xie Q, Shi Y, et al. Inhibition of connective tissue growth factor by siRNA prevents liver fibrosis in rats. J Gene Med 2006; 8: 889-900. http://dx.doi.org/10.1002/jgm.894
Brigstock DR. Strategies for blocking the fibrogenic actions of connective tissue growth factor (CCN2): From pharmacological inhibition in vitro to targeted siRNA therapy in vivo. J Cell Commun Signal 2009; 3: 5-18. http://dx.doi.org/10.1007/s12079-009-0043-9
Watts KL, Sampson EM, Schultz GS, Spiteri MA. Simvastatin inhibits growth factor expression and modulates profibrogenic markers in lung fibroblasts. Am J Respirat Cell Mol Biol 2005; 32: 290-300. http://dx.doi.org/10.1165/rcmb.2004-0127OC
Haydont V, Bourgier C, Pocard M, et al. Pravastatin Inhibits the Rho/CCN2/extracellular matrix cascade in human fibrosis explants and improves radiation-induced intestinal fibrosis in rats. Clin Cancer Res: Official J Am Assoc Cancer Res 2007; 13: 5331-40. http://dx.doi.org/10.1158/1078-0432.CCR-07-0625
Riento K, Ridley AJ. Rocks: multifunctional kinases in cell behaviour. Nat Rev Mol Cell Biol 2003; 4: 446-56. http://dx.doi.org/10.1038/nrm1128
Hahn A, Heusinger-Ribeiro J, Lanz T, et al. Induction of connective tissue growth factor by activation of heptahelical receptors. Modulation by Rho proteins and the actin cytoskeleton. J Biol Chem 2000; 275: 37429-35. http://dx.doi.org/10.1074/jbc.M000976200
Prise KM, O'Sullivan JM. Radiation-induced bystander signalling in cancer therapy. Nat Rev Cancer 2009; 9: 351-60. http://dx.doi.org/10.1038/nrc2603
Goppelt-Struebe M, Hahn A, Iwanciw D, et al. Regulation of connective tissue growth factor (ccn2; ctgf) gene expression in human mesangial cells: modulation by HMG CoA reductase inhibitors (statins). Mol Pathol: MP 2001; 54: 176-9. http://dx.doi.org/10.1136/mp.54.3.176
Sato S, Nagaoka T, Hasegawa M, et al. Serum levels of connective tissue growth factor are elevated in patients with systemic sclerosis: association with extent of skin sclerosis and severity of pulmonary fibrosis. J Rheumatol 2000; 27: 149-54.
Lopes LB, Furnish EJ, Komalavilas P, et al. Cell permeant peptide analogues of the small heat shock protein, HSP20, reduce TGF-beta1-induced CTGF expression in keloid fibroblasts. J Investig Dermatol 2009; 129: 590-8. http://dx.doi.org/10.1038/jid.2008.264
Abou-Raya A, Abou-Raya S, Helmii M. Statins: potentially useful in therapy of systemic sclerosis-related Raynaud's phenomenon and digital ulcers. J Rheumatol 2008; 35: 1801-8.
Haberberger TC, Kupfer K, Murphy JE. Profiling of genes which are differentially expressed in mouse liver in response to adenoviral vectors and delivered genes. Gene Therapy 2000; 7: 903-9. http://dx.doi.org/10.1038/sj.gt.3301181