Targeting tyrosine kinases: a novel therapeutic strategy for systemic sclerosis

Future Treatment Options in Systemic Sclerosis-Potential Targets and Ongoing Clinical Trials

Systemic sclerosis is an autoimmune connective tissue disease characterized by vasculopathy and fibrosis of the skin and internal organs. The pathogenesis of systemic sclerosis is very complex. Mediators produced by immune cells are involved in the inflammatory processes occurring in the tissues. The currently available therapeutic options are often insufficient to halt disease progress. This article presents an overview of potential therapeutic targets and the pipeline of possible future therapeutic options. It is based on research of clinical trials involving novel, unestablished methods of treatment. Increasing knowledge of the processes and mediators involved in systemic scleroderma has led to the initiation of drug trials with therapeutic targets of CD28-CD80/86, CD19, CCL24, CD20, CD30, tumor necrosis factor (TNF), transforming growth factor β (TGF-β), B-cell activating factor (BAFF), lysophosphatidic acid receptor 1 (LPA1 receptor), soluble guanylate cyclase (sGC), Janus kinases (JAK), interleukin 6 (IL-6), endothelin receptor, and autotaxin. Data from clinical trials on these drugs indicate a significant potential for several new therapeutic options for systemic sclerosis in the upcoming future.

Tyrosine kinases in the pathogenesis of tissue fibrosis in systemic sclerosis and potential therapeutic role of their inhibition

Systemic sclerosis (SSc) is an idiopathic autoimmune disease with a heterogeneous clinical phenotype ranging from limited cutaneous involvement to rapidly progressive diffuse SSc. The most severe SSc clinical and pathologic manifestations result from an uncontrolled fibrotic process involving the skin and various internal organs. The molecular mechanisms responsible for the initiation and progression of the SSc fibrotic process have not been fully elucidated. Recently it has been suggested that tyrosine protein kinases play a role. The implicated kinases include receptor-activated tyrosine kinases and nonreceptor tyrosine kinases. The receptor kinases are activated following specific binding of growth factors (platelet-derived growth factor, fibroblast growth factor, or vascular endothelial growth factor). Other receptor kinases are the discoidin domain receptors activated by binding of various collagens, the ephrin receptors that are activated by ephrins and the angiopoetin-Tie-2s receptors. The nonreceptor tyrosine kinases c-Abl, Src, Janus, and STATs have also been shown to participate in SSc-associated tissue fibrosis. Currently, there are no effective disease-modifying therapies for SSc-associated tissue fibrosis. Therefore, extensive investigation has been conducted to examine whether tyrosine kinase inhibitors (TKIs) may exert antifibrotic effects. Here, we review the role of receptor and nonreceptor tyrosine kinases in the pathogenesis of the frequently progressive cutaneous and systemic fibrotic alterations in SSc, and the potential of TKIs as SSc disease-modifying antifibrotic therapeutic agents.

Clinical Treatment Options in Scleroderma: Recommendations and Comprehensive Review

There are two major clinical subsets of scleroderma: (i) systemic sclerosis (SSc) is a complex systemic autoimmune disorder characterized by inflammation, vasculopathy, and excessive fibrosis of the skin and multiple internal organs and (ii) localized scleroderma (LoS), also known as morphea, is confined to the skin and/or subcutaneous tissues resulting in collagen deposition and subsequent fibrosis. SSc is rare but is associated with significant morbidity and mortality compared with other rheumatic diseases. Fatal outcomes in SSc often originate from organ complications of the disease, such as lung fibrosis, pulmonary artery hypertension (PAH), and scleroderma renal crisis (SRC). Current treatment modalities in SSc have focused on targeting vascular damage, fibrosis, and regulation of inflammation as well as autoimmune responses. Some drugs previously used in an attempt to suppress fibrosis, like D-penicillamine (D-Pen) or colchicine, have been disappointing in clinical practice despite anecdotal evidence of their advantages. Some canonical medications, including glucocorticoids, immunosuppressants, and vasodilators, have had some success in treating various manifestations in SSc patients. Increasing evidence suggests that some biologic agents targeting collagen, cytokines, and cell surface molecules might have promising therapeutic effects in SSc. In recent years, hematopoietic stem cell transplantation (HSCT), mostly autologous, has made great progress as a promising treatment option in severe and refractory SSc. Due to the complexity and heterogeneity of SSc, there are currently no optimal treatments for all aspects of the disease. As for LoS, local skin-targeted therapy is generally used, including topical application of glucocorticoids or other immunomodulatory ointments and ultraviolet (UV) irradiation. In addition, systemic immunosuppressants are also utilized in several forms of LoS. Here, we comprehensively discuss current treatment options for scleroderma, encompassing old, new, and future potential treatment options. In addition, we summarize data from new clinical trials that have the potential to modify the disease process and improve long-term outcomes in SSc.

Connective Tissue Disease-Associated Interstitial Lung Disease: Evaluation and Management

Interstitial lung disease is common among patients with connective tissue disease and is an important contributor to morbidity and mortality. Infection and drug toxicity must always be excluded as the cause of radiographic findings. Immunosuppression remains a mainstay of therapy despite few controlled trials supporting its use. When a decision regarding therapy initiation is made, considerations include an assessment of disease severity as well as a determination of the rate of progression. Because patients may have extrathoracic disease activity, a multidisciplinary approach is crucial and should include supportive and nonpharmacologic management strategies.

Abrogation of transforming growth factor-β-induced tissue fibrosis in TBRIcaCol1a2Cre transgenic mice by the second generation tyrosine kinase inhibitor SKI-606 (Bosutinib)

Transforming growth factor-β (TGF-β) plays a crucial role in the pathogenesis of Systemic Sclerosis (SSc) and other fibrotic disorders. TGF-β-mediated c-Abl and Src kinase activation induces strong profibrotic cascade signaling. The purpose of this study was to test in vivo the antifibrotic activity of Bosutinib (SKI-606), a second generation c-Abl and Src kinase inhibitor, on TGF-β induced cutaneous and pulmonary fibrosis. For this purpose, we employed the TBRIcaCol1a2Cre transgenic mice expressing an inducible constitutively active TGF-β receptor 1 constitutively activated by Col1a promoter-mediated Cre recombinase. The mice were treated parenterally with 2.5, 5.0 or 10.0 mg/kg/day of Bosutinib for 42 days. Skin and lungs from control and Bosutinib-treated mice (n = 6 per group) were assessed by histopathology, measurement of tissue hydroxyproline content, PCR analysis of tissue fibrosis associated gene expression, and evidence of myofibroblast activation. Mice with constitutive TGF-β-1 signaling displayed severe cutaneous and pulmonary fibrosis. Bosutinib administration decreased collagen deposition and hydroxyproline content in the dermis and lungs in a dose-dependent manner. Bosutinib also reversed the marked increase in profibrotic and myofibroblast activation-associated gene expression. These results demonstrate that constitutive TGF-β-1-signaling-induced cutaneous and pulmonary fibrosis were abrogated in a dose-related manner following parenteral administration of the c-Abl and Src tyrosine kinase inhibitor, Bosutinib. These results indicate that Bosutinib may be a potential therapeutic agent for tissue fibrosis in SSc and other fibroproliferative disorders.

Involvement of platelet-derived growth factor ligands and receptors in tumorigenesis

Platelet-derived growth factor (PDGF) isoforms and their receptors have important roles during embryogenesis, particularly in the development of various mesenchymal cell types in different organs. In the adult, PDGF stimulates wound healing and regulates tissue homeostasis. However, overactivity of PDGF signalling is associated with malignancies and other diseases characterized by excessive cell proliferation, such as fibrotic conditions and atherosclerosis. In certain tumours, genetic or epigenetic alterations of the genes for PDGF ligands and receptors drive tumour cell proliferation and survival. Examples include the rare skin tumour dermatofibrosarcoma protuberance, which is driven by autocrine PDGF stimulation due to translocation of a PDGF gene, and certain gastrointestinal stromal tumours and leukaemias, which are driven by constitute activation of PDGF receptors due to point mutations and formation of fusion proteins of the receptors, respectively. Moreover, PDGF stimulates cells in tumour stroma and promotes angiogenesis as well as the development of cancer-associated fibroblasts, both of which promote tumour progression. Inhibitors of PDGF signalling may thus be of clinical usefulness in the treatment of certain tumours.

Protein Tyrosine Phosphatases in Systemic Sclerosis: Potential Pathogenic Players and Therapeutic Targets

PURPOSE OF REVIEW

The pathogenesis of systemic sclerosis depends on a complex interplay between autoimmunity, vasculopathy, and fibrosis. Reversible phosphorylation on tyrosine residues, in response to growth factors and other stimuli, critically regulates each one of these three key pathogenic processes. Protein tyrosine kinases, the enzymes that catalyze addition of phosphate to tyrosine residues, are known players in systemic sclerosis, and tyrosine kinase inhibitors are undergoing clinical trials for treatment of this disease. Until recently, the role of tyrosine phosphatases-the enzymes that counteract the action of tyrosine kinases by removing phosphate from tyrosine residues-in systemic sclerosis has remained largely unknown. Here, we review the function of tyrosine phosphatases in pathways relevant to the pathogenesis of systemic sclerosis and their potential promise as therapeutic targets to halt progression of this debilitating rheumatic disease.

RECENT FINDINGS

Protein tyrosine phosphatases are emerging as important regulators of a multitude of signaling pathways and undergoing validation as molecular targets for cancer and other common diseases. Recent advances in drug discovery are paving the ways to develop new classes of tyrosine phosphatase modulators to treat human diseases. Although so far only few reports have focused on tyrosine phosphatases in systemic sclerosis, these enzymes play a role in multiple pathways relevant to disease pathogenesis. Further studies in this field are warranted to explore the potential of tyrosine phosphatases as drug targets for systemic sclerosis.

Proteomic Analysis of Sera from Individuals with Diffuse Cutaneous Systemic Sclerosis Reveals a Multianalyte Signature Associated with Clinical Improvement during Imatinib Mesylate Treatment

OBJECTIVE

Imatinib has been investigated for the treatment of systemic sclerosis (SSc) because of its ability to inhibit the platelet-derived growth factor receptor and transforming growth factor-β signaling pathways, which have been implicated in SSc pathogenesis. In a 12-month open-label clinical trial assessing the safety and efficacy of imatinib in the treatment of diffuse cutaneous SSc (dcSSc), significant improvements in skin thickening were observed. Here, we report our analysis of sera collected during the clinical trial.

METHODS

We measured the levels of 46 cytokines, chemokines, and growth factors in the sera of individuals with dcSSc using Luminex and ELISA. Autoantigen microarrays were used to measure immunoglobulin G reactivity to 28 autoantigens. Elastic net regularization was used to identify a signature that was predictive of clinical improvement (reduction in the modified Rodnan skin score ≥ 5) during treatment with imatinib. The signature was also tested using sera from a clinical trial of nilotinib, a tyrosine kinase inhibitor that is structurally related to imatinib, in dcSSc.

RESULTS

The elastic net algorithm identified a signature, based on levels of CD40 ligand, chemokine (C-X-C motif) ligand 4 (CXCL4), and anti-PM/Scl-100, that was significantly higher in individuals who experienced clinical improvement than in those who did not (p = 0.0011). The signature was validated using samples from a clinical trial of nilotinib.

CONCLUSION

Identification of patients with SSc with the greatest probability of benefit from treatment with imatinib has the potential to guide individualized treatment. Validation of the signature will require testing in randomized, placebo-controlled studies. Clinicaltrials.gov NCT00555581 and NCT01166139.

Different anti-remodeling effect of nilotinib and fluticasone in a chronic asthma model

BACKGROUND/AIMS

Inhaled corticosteroids are the most effective treatment currently available for asthma, but their beneficial effect against airway remodeling is limited. The tyrosine kinase inhibitor nilotinib has inhibitory activity against c-kit and the platelet-derived growth factor receptor. We compared the effects of fluticasone and nilotinib on airway remodeling in a chronic asthma model. We also examined whether co-treatment with nilotinib and fluticasone had any synergistic effect in preventing airway remodeling.

METHODS

We developed a mouse model of airway remodeling, including smooth muscle thickening, in which ovalbumin (OVA)-sensitized female BALB/c-mice were repeatedly exposed to intranasal OVA administration twice per week for 3 months. Mice were treated with fluticasone and/or nilotinib intranasally during the OVA challenge.

RESULTS

Mice chronically exposed to OVA developed eosinophilic airway inflammation and showed features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Both fluticasone and nilotinib attenuated airway smooth muscle thickening. However, only nilotinib suppressed fibrotic changes, demonstrating inhibition of collagen deposition. Fluticasone reduced pro-inflammatory cells, such as eosinophils, and several cytokines, such as interleukin 4 (IL-4), IL-5, and IL-13, induced by repeated OVA challenges. On the other hand, nilotinib reduced transforming growth factor β1 levels in bronchoalveolar lavage fluid and inhibited fibroblast proliferation significantly.

CONCLUSIONS

These results suggest that fluticasone and nilotinib suppressed airway remodeling in this chronic asthma model through anti-inflammatory and anti-fibrotic pathways, respectively.

A method for predicting target drug efficiency in cancer based on the analysis of signaling pathway activation

A new generation of anticancer therapeutics called target drugs has quickly developed in the 21st century. These drugs are tailored to inhibit cancer cell growth, proliferation, and viability by specific interactions with one or a few target proteins. However, despite formally known molecular targets for every "target" drug, patient response to treatment remains largely individual and unpredictable. Choosing the most effective personalized treatment remains a major challenge in oncology and is still largely trial and error. Here we present a novel approach for predicting target drug efficacy based on the gene expression signature of the individual tumor sample(s). The enclosed bioinformatic algorithm detects activation of intracellular regulatory pathways in the tumor in comparison to the corresponding normal tissues. According to the nature of the molecular targets of a drug, it predicts whether the drug can prevent cancer growth and survival in each individual case by blocking the abnormally activated tumor-promoting pathways or by reinforcing internal tumor suppressor cascades. To validate the method, we compared the distribution of predicted drug efficacy scores for five drugs (Sorafenib, Bevacizumab, Cetuximab, Sorafenib, Imatinib, Sunitinib) and seven cancer types (Clear Cell Renal Cell Carcinoma, Colon cancer, Lung adenocarcinoma, non-Hodgkin Lymphoma, Thyroid cancer and Sarcoma) with the available clinical trials data for the respective cancer types and drugs. The percent of responders to a drug treatment correlated significantly (Pearson's correlation 0.77 p = 0.023) with the percent of tumors showing high drug scores calculated with the current algorithm.

Dasatinib blocks transcriptional and promigratory responses to transforming growth factor-beta in pancreatic adenocarcinoma cells through inhibition of Smad signalling: implications for in vivo mode of action

Background

We have previously shown in pancreatic ductal adenocarcinoma (PDAC) cells that the SRC inhibitors PP2 and PP1 effectively inhibited TGF-β1-mediated cellular responses by blocking the kinase function of the TGF-β type I receptor ALK5 rather than SRC. Here, we investigated the ability of the clinically utilised SRC/ABL inhibitor dasatinib to mimic the PP2/PP1 effect.

Methods

The effect of dasatinib on TGF-β1-dependent Smad2/3 phosphorylation, general transcriptional activity, gene expression, cell motility, and the generation of tumour stem cells was measured in Panc-1 and Colo-357 cells using immunoblotting, reporter gene assays, RT-PCR, impedance-based real-time measurement of cell migration, and colony formation assays, respectively.

Results

In both PDAC cell lines, dasatinib effectively blocked TGF-β1-induced Smad phosphorylation, activity of 3TPlux and pCAGA₍₁₂₎-luc reporter genes, cell migration, and expression of individual TGF-β1 target genes associated with epithelial-mesenchymal transition and invasion. Moreover, dasatinib strongly interfered with the TGF-β1-induced generation of tumour stem cells as demonstrated by gene expression analysis and single cell colony formation. Dasatinib also inhibited the high constitutive migratory activity conferred on Panc-1 cells by ectopic expression of kinase-active ALK5.

Conclusions

Our data suggest that the clinical efficiency of dasatinib may in part be due to cross-inhibition of tumour-promoting TGF-β signalling. Dasatinib may be useful as a dual TGF-β/SRC inhibitor in experimental and clinical therapeutics to prevent metastatic spread in late-stage PDAC and other tumours.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0468-0) contains supplementary material, which is available to authorized users.

Update on etiopathogenesis of systemic sclerosis

Systemic Sclerosis (SSc) is an autoimmune disease of multifactorial etiology, triggered by a combination of genetic and environmental factors. Its varied clinical expression results from the complex physiopathogenic interaction of three main elements: proliferative vasculopathy, immune dysregulation and abnormal deposition and remodeling of the extracellular matrix (ECM), of which the characteristic disease fibrosis is the result. Early physiopathogenic events appear to be endothelial injury and imbalance in vascular repair with the activation of endothelial cells, the immune system and platelets, with the release of multiple mediators such as TH2 proinflammatory cytokines and growth factors, triggering a sequence of simultaneous or cascading events that involve several intracellular signaling pathways. The most important result of these events is the hyperactivation of fibroblasts, the main effector cells of fibrosis, which will then produce large amounts of ECM constituents and secrete multiple growth factors and cytokines that perpetuate the process. In this article we review the main factors potentially involved in the etiology of SSc and reexamine the current knowledge about the most important mechanisms involved in the development of lesions that are characteristic of the disease. A better understanding of these physiopathogenic mechanisms will help identify potential therapeutic targets, which may result in advances in the management of this complex and debilitating disease.

Targeting the TGF-β receptor with kinase inhibitors for scleroderma therapy

Scleroderma (systemic sclerosis) is a connective tissue disease that affects various organ systems; the treatment of scleroderma is still difficult and remains a challenge to the clinician. Recently, kinase inhibitors have shown great potential against fibrotic diseases and, specifically, the transforming growth factor-β receptor (TGF-βR) was found as a new and promising target for scleroderma therapy. In the current study, we propose that the large pool of existing kinase inhibitors could be exploited for inhibiting the TGF-βR to suppress scleroderma. In this respect, we developed a modeling protocol to systematically profile the inhibitory activities of 169 commercially available kinase inhibitors against the TGF-βR, from which five promising candidates were selected and tested using a standard kinase assay protocol. Consequently, two molecular entities, namely the PKB inhibitor MK-2206 and the mTOR C1/C2 inhibitor AZD8055, showed high potency when bound to the TGF-βR, with IC50 values of 97 and 86 nM, respectively, which are close to those of the recently developed TGF-βR selective inhibitors SB525334 and LY2157299 (IC50 = 14.3 and 56 nM, respectively). We also performed atomistic molecular dynamics simulations and post-molecular mechanics/Poisson-Boltzmann surface area analyses to dissect the structural basis and energetic properties of intermolecular interactions between the TGF-βR kinase domain and these potent compounds, highlighting intensive nonbonded networks across the tightly packed interface of non-cognate TGF-βR-inhibitor complexes.

CD90+ mesothelial-like cells in peritoneal fluid promote peritoneal metastasis by forming a tumor permissive microenvironment

The peritoneal cavity is a common target of metastatic gastrointestinal and ovarian cancer cells, but the mechanisms leading to peritoneal metastasis have not been fully elucidated. In this study, we examined the roles of cells in peritoneal fluids on the development of peritoneal metastasis. We found that a minor subset of human intraperitoneal cells with CD90(+)/CD45(−) phenotype vigorously grew in culture with mesothelial-like appearance. The mesothelial-like cells (MLC) displayed the characteristics of mesenchymal stem cell, such as differentiating into adipocytes, osteocytes, and chondrocytes, and suppressing T cell proliferation. These cells highly expressed type I collagen, vimentin, α-smooth muscle actin and fibroblast activated protein-α by the stimulation with TGF-β, which is characteristic of activated myofibroblasts. Intraperitoneal co-injection of MLCs with the human gastric cancer cell line, MKN45, significantly enhanced the rate of metastatic formation in the peritoneum of nude mice. Histological examination revealed that many MLCs were engrafted in metastatic nodules and were mainly located at the fibrous area. Dasatinib, a potent tyrosine kinase inhibitor, strongly inhibited the proliferation of MLCs but not MKN45 in vitro. Nevertheless, oral administration of Dasatinib significantly inhibited the development of peritoneal metastasis of MKN45, and resulted in reduced fibrillar formation of metastatic nodules. These results suggest floating MLCs in the peritoneal fluids support the development of peritoneal metastasis possibly through the production of the permissive microenvironment, and thus the functional blockade of MLCs is a reasonable strategy to treat recurrent abdominal malignancies.

Targeting the PDGF signaling pathway in the treatment of non-malignant diseases

Platelet-derived growth factor (PDGF) is a family of mesenchymal mitogens with important functions during the embryonal development and in the control of tissue homeostasis in the adult. The PDGF isoforms exert their effects by binding to α-and β-tyrosine kinase receptors. Overactivity of PDGF signaling has been linked to the development of certain malignant and non-malignant diseases, including atherosclerosis and various fibrotic diseases. Different types of PDGF antagonists have been developed, including inhibitory monoclonal antibodies and DNA aptamers against PDGF isoforms and receptors, and receptor tyrosine kinase inhibitors. Beneficial effects have been recorded using such inhibitors in preclinical models and in patients with certain malignant as well as non-malignant diseases. The present communication summarizes the use of PDGF antagonists in the treatment of non-malignant diseases.

Therapeutic management of intestinal fibrosis induced by radiation therapy: from molecular profiling to new intervention strategies et vice et versa

Chronic toxicities of locoregional and systemic oncological treatments commonly develop in long-term cancer survivors. Amongst these toxicities, post-radiotherapeutic complications alter patient's quality of life. Reduction of exposure of normal tissues can be achieved by optimization of radiotherapy. Furthermore, understanding of the fibrogenic mechanisms has provided targets to prevent, mitigate, and reverse late radiation-induced damages. This mini-review shows how (i) global molecular studies using gene profiling can provide tools to develop new intervention strategies and (ii) how successful clinical trials, conducted in particular with combined pentoxifylline-vitamin E, can take benefice of biological and molecular evidences to improve our understanding of fibrogenic mechanisms, enhance the robustness of proposed treatments, and lead ultimately to better treatments for patient's benefice.

Systemic sclerosis refractory disease: from the skin to the heart

Systemic sclerosis or scleroderma (SSc) is an heterogeneous disease involving the connective tissue and the microvasculature with fibrosis and vascular occlusion. It is difficult to define refractory SSc once it is itself a paradigm of a refractory condition: there is no evidence of when to act to stop the progression to fibrosis and irreversible microvascular damage. There is no definition of refractory disease in SSc and to propose a definition we used mainly the Medsger severity index and the EULAR 2009 treatment recommendations from the skin to the heart through peripheral vascular, musculoskeletal, gastrointestinal, renal, pulmonary hypertension and interstitial lung disease. We used some clinical setting reflecting the different reasoning when there is probable refractory disease and finally we briefly pointed out some available treatment options to refractory disease. With this reflection, we would like to open paths to a broader discussion.