Platelet-derived Growth Factor Receptor Kinase Research Articles

Selective inhibition of hepatic stellate cell and fibroblast-derived LOXL1 attenuates BDL- and Mdr2-/--induced cholestatic liver fibrosis.

Lysyl oxidase-like 1 (LOXL1) proteins are amine oxidases that play a crucial role in extracellular matrix remodeling due to their collagen cross-linking and intracellular functions. The role of LOXL1 in cholestatic liver fibrosis remains unexplored. We measured LOXL1 expression in two murine models of cholestasis [Mdr2 knockout (Mdr2-/-) and bile duct ligation (BDL)]. We used adeno-associated virus (AAV) serotype 6-mediated hepatic delivery against LOXL1 (AAV2/6-shLoxl1) to investigate the therapeutic efficacy of targeting LOXL1 in cholestatic liver fibrosis. NIH-3T3 murine fibroblasts were used to investigate the function and regulatory mechanisms of LOXL1 in vitro. LOXL1 expression was significantly upregulated in Mdr2-/- and BDL mice compared with their corresponding controls, predominantly in collagen-rich fibrous septa and portal areas. AAV2/6-shLoxl1 significantly reduced LOXL1 levels in Mdr2-/- and BDL mice, mainly in desmin-positive hepatic stellate cells (HSCs) and fibroblasts. Concomitant with reduced LOXL1 expression, there was reduced ductular reaction, inflammation, and fibrosis in both Mdr2-/- and BDL mice. In addition, Loxl1 intervention decreased Ki-67-positive cells in the desmin-positive areas in both Mdr2-/- and BDL mice. Overexpression of LOXL1 significantly promoted fibroblast proliferation by activating the platelet-derived growth factor receptor and extracellular signal-regulated kinase signaling pathways in vitro. Our findings demonstrated that selective inhibition of LOXL1 derived from HSCs/fibroblasts attenuated cholestatic liver/biliary fibrosis, inflammation, ductal reaction, and HSC/fibroblast proliferation. Based on our findings, LOXL1 could be a potential therapeutic target for cholestatic fibrosis.NEW & NOTEWORTHY Selectively, inhibition of HSC/fibroblasts-derived LOXL1 by AAV2/6-shLoxl1 could reduce collagen deposition, HSC/fibroblasts proliferation, and cholestatic liver fibrosis progression. In addition, overexpression of LOXL1 significantly promoted HSC/fibroblast proliferation by activating the PDGFRß/PI3K and ERK signaling pathways in vitro.

Comparison of the effects of peficitinib and tofacitinib in the adjuvant-induced arthritis rat model

We investigated and compared the pharmacologic properties of two Janus kinase (JAK) inhibitors, peficitinib and tofacitinib, in an adjuvant-induced arthritis rat model. Repeated administration of peficitinib (3 − 30 mg/kg) or tofacitinib (1 − 10 mg/kg) exhibited a dose-related and significant attenuation of arthritis score, paw swelling, pain threshold, grip strength and histopathologic injuries in the model; peficitinib 10 mg/kg and tofacitinib 3 mg/kg demonstrated comparable efficacy. Equivalent Cmax and AUC0–12h values were observed with peficitinib 10 mg/kg and tofacitinib 3 mg/kg, suggesting that the two drugs may demonstrate comparable efficacy on arthritis-associated symptoms at comparable plasma concentration levels. However, peficitinib 10 mg/kg had greater efficacy than tofacitinib 3 mg/kg on some inflammation- and bone destruction-associated parameters in the paw fluid, including the production of vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), receptor activator of nuclear factor kappa-B ligand, and matrix metalloproteinase-3, which are associated with arthritis exacerbation. Peficitinib 10 mg/kg also showed significantly greater inhibitory effects than tofacitinib 3 mg/kg on loss of bone mineral density and synovial thickening score, which might be a result of the VEGF and PDGF receptor kinase inhibitory effects of peficitinib, in addition to JAK inhibition. In conclusion, both tofacitinib and peficitinib potently improved arthritis and associated symptoms in adjuvant-induced arthritis rats; moreover, owing to possible differences in the mechanism of action of the two drugs, peficitinib may have exerted its effects through JAK inhibition and additional unique off-target properties.

Abstract 5341: Mechanisms driving resistance in Group 3 and recurrent/disseminated medulloblastoma

Abstract Background: Medulloblastoma (MB) is the most common malignant brain tumor in children and accounts for 20% of childhood brain tumors. Among the 4 molecular MB subtypes, Group 3 and 4 MBs have the worst prognosis. The biology of recurrence and dissemination in MB is less understood. Overexpression of platelet-derived growth factor receptor (PDGFR) has been associated with metastatic MB, and PDGFR activity promotes MB migration. PDGFR-induced migration is regulated by Src kinase. Src kinase activity is high in MB and Src kinase inhibition restricts tumor growth. Group 3 MB demonstrates high PDGFRA expression. Aim: Our objective was to evaluate if molecular inhibition of PDGFR or Src kinase will control metastatic progression/dissemination in Group 3 MB. Methods: We treated a panel of 4 patient-derived MB cell lines with dasatinib, which can inhibit BCRABL, c-KIT, PDGFR and Src kinase. Dasatinib dose required to inhibit c-KIT and PDGFR is higher (50-100 nM) than that needed for Src inhibition (1-10 nM). Results: Proliferation assay with dasatinib (1-10000nM) performed on all 4 cell lines did not demonstrate any inhibition of proliferation except at 10000nM dose. We treated all 4 MB cell lines with higher dose range of dasatinib (625-10000nM). One cell line did not respond to dasatinib, remaining cell lines demonstrated proliferation inhibition over 13 days between 625-5000nM. There were 2 interesting observations. Firstly, cell line which required lowest dose (625nM) was a recurrent MB, while paradoxically, its paired parental cell line (non-recurrent/treatment-naïve) responded to proliferation inhibition only at higher 5000nM dose. IC50 of parental cell line was 38-times higher than recurrent cell line. We postulated that recurrent MB may be responsive to dasatinib. However, dasatinib-treated recurrent cells demonstrated minimal changes in cell cycle phases (IC50 day 4 dose 187.4nM) and apoptotic cell death (187.4nM and 293.2nM) compared to DMSO-treated control. Since Group 3 MB demonstrates high PDGFRA expression, we employed a patient-derived orthotopic xenograft (PDOX) model of Group 3 MB to investigate the in-vivo response to dasatinib. The 2nd interesting observation was that dasatinib-treated mice exhibited earlier neuro-symptoms, more rapid tumor growth and clinical deterioration compared to control mice. However, overall animal survival time was not statistically significant between treated versus untreated groups (p=0.24 Log-rank test). Conclusions: Recurrent cells were more sensitive to dasatinib in-vitro compared to paired parental cells. In-vivo, mice treated with dasatinib developed neuro-symptoms faster than controls. It is currently not known if recurrent MB cells demonstrating early dasatinib-sensitivity to proliferation inhibition, escaping cell death, can formulate an in-vivo mechanism to drive more rapid tumor progression/dissemination as observed in our Group 3 MB Model. Citation Format: Shiying Huang, Jie-Ling Pan, Qi Lin, YuChen Du, Jack Su, Angela Major, M. Tarek Elghetany, Kam-Man Hui, Xiaonan Li, Wan-Yee Teo. Mechanisms driving resistance in Group 3 and recurrent/disseminated medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5341.

Donafenib: First Approval.

Donafenib (Zepsun®, ®), a deuterium derivative of sorafenib, is an oral small molecule multikinase inhibitor of multiple receptor kinases, including vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and Raf kinases. Donafenib is being developed by Suzhou Zelgen Biopharmaceuticals Co., Ltd. (Zelgen) for the treatment of various cancers, including hepatocellular carcinoma, colorectal cancer and thyroid cancer. In June 2021, donafenib received its first approval in China for the treatment of patients with unresectable hepatocellular carcinoma who have not previously received systemic treatment. This article summarizes the milestones in the development of donafenib leading to this first approval for use in unresectable hepatocellular carcinoma.

Risk of Thrombocytopenia With Platelet-Derived Growth Factor Receptor Kinase Inhibitors in Cancer Patients: A Systematic Review and Meta-Analysis of Phase 2/3 Randomized, Controlled Trials.

We performed a systematic review and meta-analysis to fully investigate the thrombocytopenia of platelet-derived growth factor receptor kinase inhibitors (PDGFR-TKIs) in cancer patients. Databases were searched for randomized, controlled trials (RCTs) treated with PDGFR-TKIs until January 2021. The relevant RCTs in cancer patients treated with PDGFR-TKIs were retrieved, and the systematic evaluation was conducted. Nineteen RCTs and 3962 patients were included. Our study suggests that PDGFR-TKIs significantly increased the risks of all-grade (risk ratio [RR], 5.72; 95%CI, 4.32-7.59; P < .00001; I2 = 32%) and high-grade (RR, 5.65; 95%CI, 3.28-9.75; P < .00001; I2 = 0%) thrombocytopenia in cancer patients. Sunitinib is associated with the highest risk of thrombocytopenia among the included PDGFR-TKIs. The RR of high-grade thrombocytopenia varies significantly according to treatment line and median age. The available data suggested that the use of PDGFR-TKIs was associated with a significantly increased risk of thrombocytopenia.

Screening of a Panel of Low Molecular Weight Compounds That Inhibit Synovial Fibroblast Invasion in Rheumatoid Arthritis.

Increased invasion of synovial fibroblasts and their involvement in cartilage damage are characteristic phenotypes of rheumatoid arthritis (RA). To identify low molecular weight compounds that suppress synovial fibroblast invasion, a panel of inhibitors (n = 330) was initially screened using a real-time cell analysis system for human synovial fibroblasts that were enzymatically isolated from surgical samples of RA patients. To evaluate the effects of the inhibitors identified in the screen, synovial fibroblast migration was measured using a wound-healing assay, and phosphorylation of intracellular signaling molecules was determined by immunoblots. Several candidate inhibitors were identified in the screen, including inhibitors against platelet-derived growth factor receptor (PDGFR), Akt, PI3K, and glycogen kinase synthetase 3 (GSK-3). These inhibitors strongly suppressed synovial fibroblast migration after 72 h and downregulated phosphorylation of Akt (Ser473) at 48 h. When the inhibitors were removed from the culture conditions, both migration and phosphorylated Akt (Ser473) levels were restored. Furthermore, all the categories of inhibitors except for PDGFR inhibitor IV decreased cell proliferation as well as IL-6 production in synovial fibroblasts. Interestingly, GSK-3 inhibitors increased anti-inflammatory cytokine IL-10 production but suppressed IL-23 production from LPS-primed macrophages obtained from healthy donors. In conclusion, blocking PDGFR, PI3K, or GSK-3 could have therapeutic value as an RA treatment that targets the invasion/migration of synovial fibroblasts.

Improved differentiation of human adipose stem cells to insulin-producing β-like cells using PDFGR kinase inhibitor Tyrphostin9

Diabetes mellitus (DM) is a metabolic syndrome where insulin secretion or the response to insulin produced by the body is compromised. The only available long-term treatment is the transplantation of pancreas or islet for procuring β-cells. However, due to the shortage of β-cell sources from the tissues, differentiation of pluripotent stem cells or terminally differentiated cells into β-cell is proposed as an alternative strategy. Previously, human adipose-derived stem cells (ADSCs) were reported to be converted into β-like cells by a stepwise treatment of chemicals and growth factors. However, due to the low conversion efficiency, the clinical application was not feasible. In this study, we developed a modified conversion protocol with improved yield and functionality, which is achieved by changing the culture method and addition of Tyrphostin9, a platelet-derived growth factor receptor (PDGFR) kinase inhibitor. Tyrphostin9 was identified from a cell-based chemical screening using the mCherry reporter under the control of the Pdx1 promoter. The β-like cells differentiated under the new protocol showed a 3.6-fold increase in the expression of Pdx1, a marker for pancreatic differentiation, as compared to the previous protocol. We propose that Tyrphostin9 contributes to the β-like cell differentiation by playing a dual role; enhancing the definitive endoderm generation by inhibiting the PI3K signaling and suppressing the taurine-mediated proliferation of definitive endoderm. Importantly, these differentiated cells responded well to low and high glucose stimulations compared to cells differentiated by the previous protocol, as confirmed by the 2.0-fold increase in the C-peptide release. As ADSCs are abundant, easily isolated, and autologous in nature, improved differentiation approaches to generate β-like cells from ADSCs would provide a better opportunity for treating diabetes.

Imatinib attenuates neotissue formation during vascular remodeling in an arterial bioresorbable vascular graft

BackgroundBioresorbable vascular grafts (BVGs) can transform biologically into active blood vessels and represent an alternative to traditional synthetic conduits, which are prone to complications such as infection and thrombosis. Although platelet-derived growth factors and c-Kit positive cells play an important role in smooth muscle cell (SMC) migration and proliferation in vascular injury, atherosclerosis, or allograft, their roles in the vascular remodeling process of an arterial BVG remains unknown. Thus, we assessed the neottisue formation on arterial BVG remodeling by administrating imatinib, which is both a platelet-derived growth factor receptor kinase inhibitor and c-Kit receptor kinase inhibitor, in a murine model. MethodsBVGs were composed of an inner poly(L-lactic-co-ε-caprolactone) copolymer sponge layer and an outer electrospun poly(L-lactic acid) nanofiber layer, which were implanted into the infrarenal abdominal aortas of C57BL/6 mice. After graft implantation, saline or 100 mg/kg of imatinib was administrated intraperitoneally daily for 2 weeks (n = 20 per group). Five mice in each group were scheduled to be humanely killed at 3 weeks and 15 at 8 weeks, and BVGs were explanted for histologic assessments. ResultsGraft patency during the 8-week observational period was not significantly different between groups (control, 86.7% vs imatinib, 80.0%; P > .999). Neotissue formation consisting of endothelialization, smooth muscle proliferation, and deposition of collagen and elastin was not observed in either group at 3 weeks. Similar endothelialization was achieved in both groups at 8 weeks, but thickness and percent area of neotissue formation were significantly higher in the control group than in the imatinib group, (thickness, 30.1 ± 7.2 μm vs 19.6 ± 4.5 μm [P = .001]; percent area, 9.8 ± 2.7% vs 6.8 ± 1.8% [P = .005]). Furthermore, SMC layer and deposition of collagen and elastin were better organized at 8 weeks in the control group compared with the imatinib group. The thickness of SMC layer and collagen fiber area were significantly greater at 8 weeks in the control group than in the imatinib group (P < .001 and P = .026, respectively). Because there was no difference in the inner diameter of explanted BVGs (831.7 ± 63.4 μm vs 841.8 ± 41.9 μm; P = .689), neotissue formation was thought to advance toward the outer portion of the BVG with degradation of the polymer scaffold. ConclusionsImatinib attenuates neotissue formation during vascular remodeling in arterial bioresorbable vascular grafts (BVGs) by inhibiting SMC layer formation and extracellular matrix deposition.

Pyk2-dependent phosphorylation of LSR enhances localization of LSR and tricellulin at tricellular tight junctions.

Tight junctions (TJs) are cellular junctions within the mammalian epithelial cell sheet that function as a physical barrier to molecular transport within the intercellular space. Dysregulation of TJs leads to various diseases. Tricellular TJs (tTJs), specialized structural variants of TJs, are formed by multiple transmembrane proteins (e.g., lipolysis-stimulated lipoprotein receptor [LSR] and tricellulin) within tricellular contacts in the mammalian epithelial cell sheet. However, the mechanism for recruiting LSR and tricellulin to tTJs is largely unknown. Previous studies have identified that tyrphostin 9, the dual inhibitor of Pyk2 (a nonreceptor tyrosine kinase) and receptor tyrosine kinase platelet-derived growth factor receptor (PDGFR), suppresses LSR and tricellulin recruitment to tTJs in EpH4 (a mouse mammary epithelial cell line) cells. In this study, we investigated the effect of Pyk2 inhibition on LSR and tricellulin localization to tTJs. Pyk2 inactivation by its specific inhibitor or repression by RNAi inhibited the localization of LSR and downstream tricellulin to tTJs without changing their expression level in EpH4 cells. Pyk2-dependent changes in subcellular LSR and tricellulin localization were independent of c-Jun N-terminal kinase (JNK) activation and expression. Additionally, Pyk2-dependent LSR phosphorylation at Tyr-237 was required for LSR and tricellulin localization to tTJs and decreased epithelial barrier function. Our findings indicated a novel mechanism by which Pyk2 regulates tTJ assembly and epithelial barrier function in the mammalian epithelial cell sheet.

Genetic Polymorphism on the Pharmacokinetics and Pharmacodynamics of Platelet-derived Growth Factor Receptor (PDGFR) Kinase Inhibitors.

Platelet-derived Growth Factor Receptor (PDGFR) is a kind of Receptor Tyrosine Kinases (RTKs). PDGFR Tyrosine Kinase Inhibitors (TKIs) which are small molecule inhibitors targeting PDGFR prevent and block cell proliferation signal transduction pathways. Recently, there have been 11 TKIs (including imatinib, sunitinib, regorafenib, sorafenib, pazopanib, axitinib, dasatinib, nilotinib, lenvatinib, cabozantinib and ponatinib) targeting PDGFR approved by FDA for the treatment of chronic myelogenous leukemia, gastrointestinal stromal tumors, renal cell carcinoma et al. Pharmacokinetics (PK) reflects the processes of drugs in body, while pharmacodynamics (PD) reflects the efficacy. Genetic polymorphisms of metabolizers and transporters contribute to highly inter-individual variability in PK and PD. This review aims to introduce the clinical applications, instruction and usage, PK, PD and pharmacogenetics of these PDGFR TKIs. In vivo and in vitro studies about PDGFR TKIs were searched from PubMed. Data and information were analyzed and summarized. The overview of (1) general information on PDGFR kinase inhibitors; (2) PK parameters of PDGFR kinase inhibitors; (3) metabolic enzymes and transporters of PDGFR kinase inhibitors; (4) main drug interactions of PDGFR kinase inhibitors; (5) adverse events of PDGFR kinase inhibitors; and (6) genetic polymorphism on PK and PD of PDGFR kinase inhibitors, was exhibited and discussed in this review. This review summarized the general information, PK, metabolic enzymes and transporters, main drug interactions, adverse events and pharmacogenetics of FDA approved PDGFR TKIs. Studies showed that Single nucleotide polymorphisms of metabolic enzymes and transporters had influence on the PK and PD of PDGFR TKIs.

A small molecule fibrokinase inhibitor in a model of fibropolycystic hepatorenal disease.

AIMTo evaluate the novel platelet-derived growth factor receptor and vascular endothelial growth factor receptor dual kinase inhibitor ANG3070 in a polycystic kidney disease-congenital hepatic fibrosis model.METHODSAt 6 wk of age, PCK rats were randomized to vehicle or ANG3070 for 4 wk. At 10 wk, 24 h urine and left kidneys were collected and rats were continued on treatment for 4 wk. At 14 wk, 24 h urine was collected, rats were sacrificed, and liver and right kidneys were collected for histological evaluation. For Western blot studies, PCK rats were treated with vehicle or ANG3070 for 7 d and sacrificed approximately 30 min after the last treatments.RESULTSCompared to the wild-type cohort, the PCK kidney (Vehicle cohort) exhibited a marked increase in kidney and liver mass, hepato-renal cystic volume, hepato-renal fibrosis and hepato-renal injury biomarkers. Intervention with ANG3070 in PCK rats decreased kidney weight, reduced renal cystic volume and reduced total kidney hydroxyproline, indicating significantly reduced rental interstitial fibrosis compared to the PCK-Vehicle cohort. ANG3070 treatment also mitigated several markers of kidney injury, including urinary neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, cystatin C and interleukin-18 levels. In addition, this treatment attenuated key indices of renal dysfunction, including proteinuria, albuminuria and serum blood urea nitrogen and creatinine, and significantly improved renal function compared to the PCK-Vehicle cohort. ANG3070 treatment also significantly decreased liver enlargement, hepatic lesions, and liver fibrosis, and mitigated liver dysfunction compared to the PCK-Vehicle cohort.CONCLUSIONThese results suggest that ANG3070 has the potential to slow disease, and may serve as a bridge toward hepato-renal transplantation in patients with fibropolycystic disease.

ПОРІВНЯЛЬНИЙ АНАЛІЗ РЕЗУЛЬТАТІВ IN VIVO СКРИНІНГУ ТА IN SILICO ПРОГНОЗУВАННЯ ПСИХО- ТА НЕЙРОТРОПНИХ ВЛАСТИВОСТЕЙ 3-(N-R,R′-АМІНОМЕТИЛ)-2-МЕТИЛ-1Н-ХІНОЛІН-4-ОНІВ

Мета роботи. Провести аналіз результатів скринінгових in vivo досліджень та ретроспективного in silico прогнозування психо- та нейротропних властивостей 3-(N-R,R′-амінометил)-2-метил-1Н-хінолін-4-онів за допомогою програми PASS.Матеріали і методи. Аналіз результатів попередніх скринінгових in vivo досліджень психо- та нейротропних властивостей 3-(N-R,R′-амінометил)-2-метил-1Н-хінолін-4-онів ґрунтувався на опублікованих нами даних. Комп’ютерне прогнозування спектра біологічних властивостей 3-(N-R,R′-амінометил)-2-метил-1Н-хінолін-4-онів проведено ретроспективно за допомогою системи PASS Online.Результати й обговорення. Систематизація та аналіз результатів проведених раніше експериментальних фармакологічних досліджень показали, що більшість 3-(N-R,R′-амінометил)-2-метил-1Н-хінолін-4-онів має виразні ноотропні властивості, які у деяких похідних поєднуються з високою антидепресивною активністю, протитривожним ефектом, седативними або, навпаки, стимулювальними властивостями. Аналіз результатів для окремих підгруп 3-(N-R,R′-амінометил)-2-метил-1Н-хінолін-4-онів дозволив виявити певні зв’язки між хімічною будовою та характером біологічної дії сполук.Результати PASS-прогнозу показали, що найбільш імовірними біологічними ефектами 3-(N-R,R′-амінометил)-2-метил-1Н-хінолін-4-онів є здатність виступати інгібіторами убіхінол-цитохром с редуктази, глюконат 2-дегідрогенази, пластохінол-пластоціанін редуктази, кінази рецепторів тромбоцитарного фактора росту та енхансерами експресії 3-гідрокси-3-метилглутарил-КоА синтази 2. Показники для ефектів, які хоча б опосередковано можуть впливати на функції ЦНС (активатори потенціалзалежних кальцієвих каналів та інгібітори вивільнення серотоніну), мають значно нижчі значення.Висновки. За умови використання комп’ютерного прогнозування спектра фармакологічної активності 3-(N-R,R′-амінометил)-2-метил-1Н-хінолін-4-онів за допомогою програми PASS як основного підґрунтя для подальших скринінгових досліджень цей клас сполук було б втрачено як перспективний в аспекті пошуку нових речовин, здатних впливати на функції ЦНС.

Chebulinic acid inhibits smooth muscle cell migration by suppressing PDGF-R\u03b2 phosphorylation and inhibiting matrix metalloproteinase-2 expression

Excessive migration of vascular smooth muscle cells (VSMCs) after vascular injury contributes to the development of occlusive vascular disease. Inhibition of VSMC migration is a validated therapeutic modality for occlusive vascular diseases, such as atherosclerosis and restenosis. We investigated the inhibitory effect of chebulinic acid (CBA) on cell migration and matrix metalloproteinase (MMP)-2 activation in platelet-derived growth factor (PDGF)-BB-induced mouse and human VSMCs. CBA significantly inhibited PDGF-BB-induced migration in mouse and human VSMCs, without inducing cell death. Additionally, CBA significantly blocked PDGF-BB-induced phosphorylation of the PDGF receptor (PDGF-R), Akt, and extracellular signal-regulated kinase (ERK)1/2 by inhibiting the activation of the PDGF-BB signalling pathway. In both mouse and human VSMCs, CBA inhibited PDGF-induced MMP-2 mRNA and protein expression as well as the proteolytic activity of MMP-2. Moreover, CBA suppressed sprout outgrowth formation of VSMCs from endothelium-removed aortic rings as well as neointima formation following rat carotid balloon injury. Taken together, our findings indicated that CBA inhibits VSMC migration by decreasing MMP-2 expression through PDGF-R and the ERK1/2 and Akt pathways. Our data may improve the understanding of the antiatherogenic effects of CBA in VSMCs.

Targeting the tyrosine kinase signalling pathways for treatment of immune-mediated glomerulonephritis: from bench to bedside and beyond.

Glomerulonephritis (GN) affects patients of all ages and is an important cause of morbidity and mortality. Non-selective immunosuppressive drugs have been used in immune-mediated GN but often result in systemic side effects and occasionally fatal infective complications. There is increasing evidence from both preclinical and clinical studies that abnormal activation of receptor and non-receptor tyrosine kinase signalling pathways are implicated in the pathogenesis of immune-mediated GN. Activation of spleen tyrosine kinase (SYK), Bruton's tyrosine kinase (BTK), platelet-derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR) and discoidin domain receptor 1 (DDR1) have been demonstrated in anti-GBM disease. SYK is implicated in the pathogenesis of ANCA-associated GN. SYK, BTK, PDGFR, EFGR, DDR1 and Janus kinase are implicated in the pathogenesis of lupus nephritis. A representative animal model of IgA nephropathy (IgAN) is lacking. Based on the results from in vitro and human renal biopsy study results, a phase II clinical trial is ongoing to evaluate the efficacy and safety of fostamatinib (an oral SYK inhibitor) in high-risk IgAN patient. Various tyrosine kinase inhibitors (TKIs) have been approved for cancer treatment. Clinical trials of TKIs in GN may be justified given their long-term safety data. In this review we will discuss the current unmet medical needs in GN treatment and research as well as the current stage of development of TKIs in GN treatment and propose an accelerated translational research approach to investigate whether selective inhibition of tyrosine kinase provides a safer and more efficacious option for GN treatment.

Optimization of Platelet-Derived Growth Factor Receptor (PDGFR) Inhibitors for Duration of Action, as an Inhaled Therapy for Lung Remodeling in Pulmonary Arterial Hypertension.

A series of potent PDGFR inhibitors has been identified. The series was optimized for duration of action in the lung. A novel kinase occupancy assay was used to directly measure target occupancy after i.t. dosing. Compound 25 shows 24 h occupancy of the PDGFR kinase domain, after a single i.t. dose and has efficacy at 0.03 mg/kg, in the rat moncrotaline model of pulmonary arterial hypertension. Examination of PK/PD data from the optimization effort has revealed in vitro:in vivo correlations which link duration of action in vivo with low permeability and high basicity and demonstrate that nonspecific binding to lung tissue increases with lipophilicity.

Differentiation of Murine Bone Marrow-Derived Smooth Muscle Progenitor Cells Is Regulated by PDGF-BB and Collagen.

Smooth muscle cells (SMCs) are key regulators of vascular disease and circulating smooth muscle progenitor cells may play important roles in vascular repair or remodelling. We developed enhanced protocols to derive smooth muscle progenitors from murine bone marrow and tested whether factors that are increased in atherosclerotic plaques, namely platelet-derived growth factor—BB (PDGF-BB) and monomeric collagen, can influence the smooth muscle specific differentiation, proliferation, and survival of mouse bone marrow-derived progenitor cells. During a 21 day period of culture, bone marrow cells underwent a marked increase in expression of the SMC markers α-SMA (1.93 ± 0.15 vs. 0.0008 ± 0.0003 (ng/ng GAPDH) at 0 d), SM22-α (1.50 ± 0.27 vs. 0.005 ± 0.001 (ng/ng GAPDH) at 0 d) and SM-MHC (0.017 ± 0.004 vs. 0.001 ± 0.001 (ng/ng GAPDH) at 0 d). Bromodeoxyuridine (BrdU) incorporation experiments showed that in early culture, the smooth muscle progenitor subpopulation could be identified by high proliferative rates prior to the expression of smooth muscle specific markers. Culture of fresh bone marrow or smooth muscle progenitor cells with PDGF-BB suppressed the expression of α-SMA and SM22-α, in a rapidly reversible manner requiring PDGF receptor kinase activity. Progenitors cultured on polymerized collagen gels demonstrated expression of SMC markers, rates of proliferation and apoptosis similar to that of cells on tissue culture plastic; in contrast, cells grown on monomeric collagen gels displayed lower SMC marker expression, lower growth rates (319 ± 36 vs. 635 ± 97 cells/mm2), and increased apoptosis (5.3 ± 1.6% vs. 1.0 ± 0.5% (Annexin 5 staining)). Our data shows that the differentiation and survival of smooth muscle progenitors are critically affected by PDGF-BB and as well as the substrate collagen structure.

Orbital dermatofibrosarcoma protuberans with intracranial extension preceded by recurrent leiomyoma of the orbit: a case report

IntroductionDermatofibrosarcoma protuberans is a rare, locally aggressive cutaneous tumor of intermediate to low-grade malignancy. COL1A1-PDGFβ translocation is specific to dermatofibrosarcoma protuberans, where the abnormally fused COL1A1-PDGFβ gene directs formation of an abnormal combined (fusion) protein that researchers believe to ultimately function like the platelet-derived growth factor-beta protein.Case presentationIn this report, we present a case of a 63-year-old Asian man with dermatofibrosarcoma protuberans of the right orbit with intracranial extension. He had a prior history of recurrent leiomyomas at the identical site. He underwent near-total en bloc resection of the tumor through a wide craniectomy with a 6cm rim of the frontal scalp, allowing the tumor to be resected en bloc, leaving negative margins. Microscopically, the tumor comprised spindle cells with mild nuclear atypia and a low mitotic index embedded in a spiraling pattern of decussating fascicles consistent with dermatofibrosarcoma protuberans. The lesion was positive for CD34 and BCL2. Following resection, the patient was started on imatinib mesylate therapy (800mg/day).ConclusionsWe propose that platelet-derived growth factor, which has been implicated in the progression of leiomyomas by augmenting mitogenesis, may have acted in an autocrine manner to cause cell division, which may have led to the development of dermatofibrosarcoma protuberans in our patient. Further research is imperative to find certain molecular associations between the discussed soft tissue tumors. Also important is the effective utilization of platelet-derived growth factor receptor kinase inhibitors to prevent transformation to any platelet-derived growth factor–driven tumor, which in our patient was a dermatofibrosarcoma protuberans.

Role of retinoic acid and platelet-derived growth factor receptor cross talk in the regulation of neonatal gonocyte and embryonal carcinoma cell differentiation.

Neonatal gonocytes are direct precursors of spermatogonial stem cells, the cell pool that supports spermatogenesis. Although unipotent in vivo, gonocytes express pluripotency genes common with embryonic stem cells. Previously, we found that all-trans retinoic acid (RA) induced the expression of differentiation markers and a truncated form of platelet-derived growth factor receptor (PDGFR)β in rat gonocytes, as well as in F9 mouse embryonal carcinoma cells, an embryonic stem cell-surrogate that expresses somatic lineage markers in response to RA. The present study is focused on identifying the signaling pathways involved in RA-induced gonocyte and F9 cell differentiation. Mitogen-activated protein kinase kinase (MEK) 1/2 activation was required during F9 cell differentiation towards somatic lineage, whereas its inhibition potentiated RA-induced Stra8 expression, suggesting that MEK1/2 acts as a lineage specification switch in F9 cells. In both cell types, RA increased the expression of the spermatogonial/premeiotic marker Stra8, which is in line with F9 cells being at a stage before somatic-germline lineage specification. Inhibiting PDGFR kinase activity reduced RA-induced Stra8 expression. Interestingly, RA increased the expression of PDGFRα variant forms in both cell types. Together, these results suggest a potential cross talk between RA and PDGFR signaling pathways in cell differentiation. RA receptor-α inhibition partially reduced RA effects on Stra8 in gonocytes, indicating that RA acts in part via RA receptor-α. RA-induced gonocyte differentiation was significantly reduced by inhibiting SRC (v-src avian sarcoma [Schmidt-Ruppin A-2] viral oncogene) and JAK2/STAT5 (Janus kinase 2/signal transducer and activator of transcription 5) activities, implying that these signaling molecules play a role in gonocyte differentiation. These results suggest that gonocyte and F9 cell differentiation is regulated via cross talk between RA and PDGFRs using different downstream pathways.

The Telomeric Protein TRF2 Regulates Angiogenesis by Binding and Activating the PDGFRβ Promoter

Telomeric repeat binding factor 2 (TRF2), which plays a central role in telomere capping, is frequently increased in human tumors. We reveal here that TRF2 is expressed in the vasculature of most human cancer types, where it colocalizes with the Wilms' tumor suppressor WT1. We further show that TRF2 is a transcriptional target of WT1 and is required for proliferation, migration, and tube formation of endothelial cells. These angiogenic effects of TRF2 are uncoupled from its function in telomere capping. Instead, TRF2 binds and transactivates the promoter of the angiogenic tyrosine kinase platelet-derived growth factor receptor β (PDGFRβ). These findings reveal an unexpected role of TRF2 in neoangiogenesis and delineate a distinct function of TRF2 as a transcriptional regulator.

Indispensable functions of ABL and PDGF receptor kinases in epithelial adherence of attaching/effacing pathogens under physiological conditions.

Enteropathogenic Escherichia coli (EPEC) and Citrobacter rodentium are attaching-and-effacing (A/E) pathogens that cause intestinal inflammation and diarrhea. The bacteria adhere to the intestinal epithelium, destroy microvilli, and induce actin-filled membranous pedestals but do not invade the mucosa. Adherence leads to activation of several host cell kinases, including FYN, n-SRC, YES, ABL, and ARG, phosphorylation of the bacterial translocated intimin receptor, and actin polymerization and pedestal formation in cultured cells. However, marked functional redundancy appears to exist between kinases, and their physiological importance in A/E pathogen infections has remained unclear. To address this question, we employed a novel dynamic in vitro infection model that mimics transient and short-term interactions in the intestinal tract. Screening of a kinase inhibitor library and RNA interference experiments in vitro revealed that ABL and platelet-derived growth factor (PDGF) receptor (PDGFR) kinases, as well as p38 MAP kinase, have unique, indispensable roles in early attachment of EPEC to epithelial cells under dynamic infection conditions. Studies with mutant EPEC showed that the attachment functions of ABL and PDGFR were independent of the intimin receptor but required bacterial bundle-forming pili. Furthermore, inhibition of ABL and PDGFR with imatinib protected against infection of mice with modest loads of C. rodentium, whereas the kinases were dispensable for high inocula or late after infection. These results indicate that ABL and PDGFR have indispensable roles in early A/E pathogen attachment to intestinal epithelial cells and for in vivo infection with limiting inocula but are not required for late intimate bacterial attachment or high inoculum infections.