Platelet-derived Growth Factor Receptor Pathway Research Articles

Computational evidence for multi-layer crosstalk between the cadherin-11 and PDGFR pathways

Various cell surface receptors play an important role in the differentiation and self-renewal of human mesenchymal stem cells (hMSCs). One example of such receptors are the cadherins, which maintain cell–cell adhesion and mechanically couple cells together. Recently, cadherin-11, which is a member of the type II classical cadherin family, has been shown to be involved in the fate commitment of hMSCs. Interestingly, cadherin-11 has no known intrinsic signaling activity and is thought to affect cell behavior via interactions with other cell surface receptors. Members of the platelet-derived growth factor receptor (PDGFR) family are hypothesized to be one of the interaction partners of cadherin-11. Experiments confirmed that PDGFR-α binding to extracellular cadherin-11 regions increases the PDGFR-α activity, whereas the interaction between PDGFR-β and cadherin-11 suppresses the activity of the growth factor receptor. Cadherin-11 knockdown experiments also decreased cell proliferation. These interactions between cadherin-11 and PDGFRs indicate a crosstalk between these receptors and their downstream signaling activities but the nature of this crosstalk is not entirely known. In this study, we used a computational model to represent the experimentally proven interactions between cadherin-11 and the two PDGFRs and we inspected whether the crosstalk also exists downstream of the signaling initiated by the two receptor families. The computational framework allowed us to monitor the relative activity levels of each protein in the network. We performed model simulations to mimic the conditions of previous cadherin-11 knockdown experiments and to predict the effect of crosstalk on cell proliferation. Overall, our predictions suggest the existence of another layer of crosstalk, namely between β-catenin (downstream to cadherin-11) and an ERK inhibitor protein (e.g. DUSP1), different than the crosstalk at the receptor level between cadherin-11 and PDGFR-α and -β. By investigating the multi-level crosstalk between cadherin and PDGFRs computationally, this study contributes to an improved understanding of the effect of cell surface receptors on hMSCs proliferation.

Transcriptome of Two Canine Prostate Cancer Cells Treated With Toceranib Phosphate Reveals Distinct Antitumor Profiles Associated With the PDGFR Pathway.

Canine prostate cancer (PC) presents a poor antitumor response, usually late diagnosis and prognosis. Toceranib phosphate (TP) is a nonspecific inhibitor of receptor tyrosine kinases (RTKs), including vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), and c-KIT. This study aimed to evaluate VEGFR2, PDGFR-β, and c-KIT protein expression in two established canine PC cell lines (PC1 and PC2) and the transcriptome profile of the cells after treatment with TP. Immunofluorescence (IF) analysis revealed VEGFR2 and PDGFR-β protein expression and the absence of c-KIT protein expression in both cell lines. After TP treatment, only the viability of PC1 cells decreased in a dose-dependent manner. Transcriptome and enrichment analyses of treated PC1 cells revealed 181 upregulated genes, which were related to decreased angiogenesis and cell proliferation. In addition, we found upregulated PDGFR-A, PDGFR-β, and PDGF-D expression in PC1 cells, and the upregulation of PDGFR-β was also observed in treated PC1 cells by qPCR. PC2 cells had fewer protein-protein interactions (PPIs), with 18 upregulated and 22 downregulated genes; the upregulated genes were involved in the regulation of parallel pathways and mechanisms related to proliferation, which could be associated with the resistance observed after treatment. The canine PC1 cell line but not the PC2 cell line showed decreased viability after treatment with TP, although both cell lines expressed PDGFR and VEGFR receptors. Further studies could explain the mechanism of resistance in PC2 cells and provide a basis for personalized treatment for dogs with PC.

Single Centre, Retrospective Study to Evaluate Treatment Outcomes Following Tyrosine Kinase Inhibitor for Chronic Gvhd Treatment Including Ruxolitinib, Ibrutinib and Imatinib

Background Chronic graft-versus-host-disease (cGVHD) is one of the main causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HCT). Tyrosine kinase inhibitor such as Ruxolitinib, Ibrutinib and Imatinib showed a promising efficacy in cGVHD treatment. Ruxolitinib is a JAK-STAT inhibitor, reducing inflammation and immune pathway. Ibrutinib is a BTK inhibitor, blocking B cell-activating factor (BAFF), while Imatinib inhibits the platelet-derived growth factor receptor pathway activated by cGvHD-induced antibodies. The present retrospective study evaluated the efficacy of 3 TKIs for cGVHD at a single-centre in terms of 1) overall response rate (ORR), 2) clinical benefit (CB), 3) dose reduction of steroid, 4) failure-free survival (FFS) and 5) overall survival (OS). Patients and Methods A total of 43 patients who developed cGVHD after HCT and treated with TKI therapy for cGVHD at Princess Margaret Cancer Centre, Canada from August 2014 to April 2020 were evaluated in this retrospective study. 16 patients were treated with more than one TKI drug. A total of 62 lines of TKI therapy was evaluated, including Ruxolinitib (n=18), Ibrutinib (n=13) and Imatinib (n=31). The ORRs and CBs were assessed at months 3, 6 and 12, retrospectively. Responses were evaluated according to NIH scoring/staging/response assessment as part of standard clinical practice. CB was assessed considering clinical response as well as steroid dose reduction. For systemic steroid dose reduction, prednisone dose per kg per day was captured prior to Ruxolitinib start, at months 3, 6 and 12. Treatment failure was defined as 1) resistance requiring treatment switch, 2) non-relapse mortality (NRM), 3) relapse, 4) intolerance requiring treatment discontinuation. FFS and OS were calculated from the day of starting TKI therapy for cGVHD treatment. Results The patients and disease characteristics are summarized as follow: median age was 54 years (range 16 -70); 33 patients (53%) presented with classical cGVHD, while 29 patients (47%) with overlap syndrome; 14 (23%) presented with moderate and 48 (77%) with severe grade cGVHD. There was no difference in cGVHD subtype among 3 TKI subgroups (p= 0.478). The median number of organ involvement was 3 (range 1-5), and number of previous lines of therapy was 5 (range 3-9), implying that most of the patients were heavily pretreated for cGVHD. The mean (±S.E.) dosage of TKI treatment was as follows: Ruxolitinib was started at 15±1.1mg as initial dose and 20±0.7, 19±1.5, 22±4.4 mg per day in two divided doses on months 3, 6 and 12, respectively. Ibrutinib dose was 226±37, 256±37, 308±40 and 370±33 mg per day, while Imatinib dose was 106±6, 189±18, 196±16 and 190±19 mg per day prior to TKI starts, at months 3, 6 and 12, respectively. With a median follow up duration of 12 months, 19 (31%), 20 (32%), and 17 patients (27%) responded to TKI therapy at 3, 6, and 12 months without any difference of ORR among the TKIs (p=0.126, 0.554, 0.721 at 3/6/12 months; Figure A). The CBs were achieved in 47 (76%), 34 (55%), and 23 patients (37%) at 3, 6 and 12 months without any difference of CBs among the TKIs (p=0.187, 0.499, 0.750 at 3/6/12 months; Figure B). Prednisone dose (mg/kg/day) was 0.238±0.03 prior to TKI initiation, 0.177±0.03, 0.173 ± 0.03 and 0.110 ± 0.02 at 3, 6, and 12 months, respectively. No difference was noted in steroid dose among the 3 TKIs at each time point. However, the Ibrutinib group tends to require higher prednisone dose over time than other 2 groups. The FFS at 12 months was higher in Imatinib (71%) or Ruxolitinib groups (67%) than Ibrutinib group (46%; Figure C). The OS rate at 12 months was similar: 100 % in Ruxolitinib and Ibrutinib, and 96% in Imatinib group (Figure D). With regard to those patients treated with TKI for sclerotic GVHD (n= 39), the ORR were 11 (28%), 15 (38%) and 13 (33%) for 3, 6 and 12 months, while CB was noted in 32 (82%), 25 (64%) and 16 patients (41%) at 3, 6 and 12 months respectively. Of interest, Ruxolitinib was as effective as Imatinib in improving PROM score of sclerotic GVHD, while no significant improvement of PROM score was observed in the patients treated with Ibrutinib. Conclusion This retrospective study evaluated the efficacy of TKI drugs for cGVHD treatment in heavily pretreated patients. Ruxolitinib seems as effective as Imatinib to treat sclerotic GVHD. No difference was observed in OS at 12 months; while FFS appears better with Ruxolitinib and Imatinib over Ibrutinib. Figure Disclosures Lipton: Ariad: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding.

Programming of Schwann Cells by Lats1/2-TAZ/YAP Signaling Drives Malignant Peripheral Nerve Sheath Tumorigenesis

Malignant peripheral nerve sheath tumors (MPNSTs) are highly aggressive Schwann cell (SC)-lineage-derived sarcomas. Molecular events driving SC-to-MPNST transformation are incompletely understood. Here, we show that human MPNSTs exhibit elevated HIPPO-TAZ/YAP expression, and that TAZ/YAP hyperactivity in SCs caused by Lats1/2 loss potently induces high-grade nerve-associated tumors with full penetrance. Lats1/2 deficiency reprograms SCs to a cancerous, progenitor-like phenotype and promotes hyperproliferation. Conversely, disruption of TAZ/YAP activity alleviates tumor burden in Lats1/2-deficient mice and inhibits human MPNST cell proliferation. Moreover, genome-wide profiling reveals that TAZ/YAP-TEAD1 directly activates oncogenic programs, including platelet-derived growth factor receptor (PDGFR) signaling. Co-targeting TAZ/YAP and PDGFR pathways inhibits tumor growth. Thus, our findings establish a previously unrecognized convergence between Lats1/2-TAZ/YAP signaling and MPNST pathogenesis, revealing potential therapeutic targets in these untreatable tumors.

Synectin promotes fibrogenesis by regulating PDGFR isoforms through distinct mechanisms.

The scaffold protein synectin plays a critical role in the trafficking and regulation of membrane receptor pathways. As platelet-derived growth factor receptor (PDGFR) is essential for hepatic stellate cell (HSC) activation and liver fibrosis, we sought to determine the role of synectin on the PDGFR pathway and development of liver fibrosis. Mice with deletion of synectin from HSC were found to be protected from liver fibrosis. mRNA sequencing revealed that knockdown of synectin in HSC demonstrated reductions in the fibrosis pathway of genes, including PDGFR-β. Chromatin IP assay of the PDGFR-β promoter upon synectin knockdown revealed a pattern of histone marks associated with decreased transcription, dependent on p300 histone acetyltransferase. Synectin knockdown was found to downregulate PDGFR-α protein levels, as well, but through an alternative mechanism: protection from autophagic degradation. Site-directed mutagenesis revealed that ubiquitination of specific PDGFR-α lysine residues was responsible for its autophagic degradation. Furthermore, functional studies showed decreased PDGF-dependent migration and proliferation of HSC after synectin knockdown. Finally, human cirrhotic livers demonstrated increased synectin protein levels. This work provides insight into differential transcriptional and posttranslational mechanisms of synectin regulation of PDGFRs, which are critical to fibrogenesis.

Biochemical Effects of Some Tyrosine Kinase Inhibitors on Pro-B Cells-Induced Apoptosis

The present studies aimed the effects of tyrphostin AG 494 and tyrphostin AG 1295 on apoptosis of mouse pro-B lymphocytes. The actual scientific literature lacks such data. Tyrphostin AG 494 is an inhibitor of epidermal growth factor receptor pathways and tyrphostin AG 1295 is an inhibitor of platelet-derived growth factor receptor pathways. Our obtained data demonstrated that tyrphostin AG 1295 was less effective in preventing the apoptosis of murine pro-B cells, triggered by the combination of Cytoporone B (NR4A1 agonist) and Cyclosporine A. In contrast, tyrphostin AG 494 had a stronger inhibitory effect on the apoptosis of the same cells, when administered for 24 hours. Thus, when blocking the activation of epidermal growth factor receptor pathways, the inductive apoptotic effects of Cytoporone B and Cyclosporine A are reduced. Thus, we could conclude that such inhibition will increase the resistance to apoptosis of pro-B cells. Thus, such a resistance to apoptosis could be experimentally acquired by hematopoietic cells.

Nintedanib: evidence for its therapeutic potential in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with poor prognosis. The molecular mechanisms involved in the progression of IPF are not fully understood; however, the platelet-derived growth factor (PDGF)/PDGF receptor pathway is thought to play a critical role in fibrogenesis of the lungs. Other growth factors, including fibroblast growth factor and vascular endothelial growth factor, are also thought to contribute to the pathogenesis of pulmonary fibrosis. Nintedanib is an inhibitor of multiple tyrosine kinases, including receptors for PDGF, fibroblast growth factor, and vascular endothelial growth factor. In the Phase II TOMORROW trial, treatment with 150 mg of nintedanib twice daily showed a trend to slow the decline in lung function and significantly decrease acute exacerbations in patients with IPF, while showing an acceptable safety profile. The Phase III INPULSIS trials demonstrated a significant decrease in the annual rate of decline in forced vital capacity in IPF patients treated with 150 mg nintedanib twice daily. In the INPULSIS-2 trial, the time to the first acute exacerbation significantly increased in IPF patients who were treated with 150 mg of nintedanib twice daily. Pirfenidone, another antifibrotic drug, was shown to limit the decline in pulmonary function in patients with IPF in the ASCEND trial. Combination therapy with nintedanib and pirfenidone is anticipated, although further evaluation of its long-term safety is needed. There is limited evidence for the safety of the combination therapy although a Phase II trial conducted in Japan demonstrated that combination therapy with nintedanib and pirfenidone was tolerable for 1 month. Available antifibrotic agents (ie, pirfenidone and N-acetylcysteine) have limited efficacy as single therapies for IPF; therefore, further study of combination therapy with antifibrotic agents is needed.

Toxicity evaluation of convection-enhanced delivery of small-molecule kinase inhibitors in naïve mouse brainstem.

Diffuse intrinsic pontine gliomas (DIPGs) are inoperable and lethal high-grade gliomas lacking definitive therapy. Platelet-derived growth factor receptor (PDGFR) and its downstream signaling molecules are the most commonly overexpressed oncogenes in DIPG. This study tested the effective concentration of PDGFR pathway inhibitors in cell culture and then toxicity of these small-molecule kinase inhibitors delivered to the mouse brainstem via convection-enhanced delivery (CED) for potential clinical application. Effective concentrations of small-molecule kinase inhibitors were first established in cell culture from a mouse brainstem glioma model. Sixteen mice underwent CED, a local drug delivery technique, of saline or of single and multidrug combinations of dasatinib (2 M), everolimus (20 M), and perifosine (0.63 mM) in the pons. Animals were kept alive for 3 days following the completion of infusion. No animals displayed any immediate or delayed neurological deficits postoperatively. Histological analysis revealed edema, microgliosis, acute inflammation, and/or axonal injury in the experimental animals consistent with mild acute drug toxicity. Brainstem CED of small-molecule kinase inhibitors in the mouse did not cause serious acute toxicities. Future studies will be necessary to evaluate longer-term safety to prepare for potential clinical application.

Effect of nilotinib on airway remodeling in a murine model of chronic asthma

ABSTRACTObjective: The tyrosine kinase inhibitor nilotinib has potent inhibitory activity against the stem cell growth factor receptor c-Kit and platelet-derived growth factor receptor (PDGFR). The present study aimed to determine whether nilotinib suppresses airway remodeling and whether its effect is associated with the c-Kit and PDGFR pathways. We also aimed to compare the effect of nilotinib and imatinib on remodeling. Methods: We developed a mouse model of airway remodeling, which includes smooth muscle thickening, in which ovalbumin (OVA)-sensitized mice were repeatedly exposed to intranasal OVA administration twice a week for 3 months. Mice were treated with nilotinib or imatinib during the OVA challenge. Results: Compared with control mice, the mice chronically exposed to OVA developed sustained eosinophilic airway inflammation, airway hyperresponsiveness (AHR), and exhibited features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Administration of nilotinib significantly inhibited eosinophilic inflammation, AHR, and remodeling in mice chronically exposed to OVA. Nilotinib showed a trend of more potent effect than imatinib on attenuating remodeling in hydroxyproline assay and smooth muscle staining. Nilotinib treatment significantly reduced the expression of phosphorylated (p)-c-Kit, p-PDGFRβ, and p-extracellular signal-regulated kinase 1/2. The expression levels of the genes encoding c-Kit and PDGFRβ were also reduced by nilotinib treatment. Treatment with nilotinib did not affect significantly the level of OVA-specific IgE and IgG1 in serum. In vitro, nilotinib significantly inhibited cell proliferation of fibroblast. Conclusions: These results suggest that nilotinib administration can prevent airway inflammation, AHR, and airway remodeling associated with chronic allergen challenge.

Role of platelet derived growth factor receptor (PDGFR) over-expression and angiogenesis in ependymoma

New molecularly targeted therapies are needed for childhood ependymoma. Angiogenesis and the PDGFR pathway could be potential therapeutic targets. This study aimed to screen ependymomas for the expression and clinicopathological correlates of angiogenic factors and potential therapeutic targets including VEGFR, endoglin (CD105), CD34, CD31, c-Kit, PDGFR-α and PDGFR-β. Immunohistochemistry for angiogenesis factors and PDGFR-α and β was performed in 24 archival tumor samples from children and adults treated for ependymoma at our institution. CD31 density, CD105 density and pericyte coverage index (PCI) were calculated. These findings were correlated with clinical outcome. VEGFR2 was overexpressed in tumor cells in only one out of 24 cases, but was found overexpressed in the vessels in 6 cases. PDGFR-α and β were found to be over-expressed in the ependymoma tumor cells in seven out of 24 cases (29.2 %). CD31 density, CD105 density and PCI did not correlate with expression of PDGFRs. Overexpression of PDGFR-α and β in tumor cells and overexpression of PDGFR-α in tumor endothelium had prognostic significance and this was maintained in multivariate analysis for overexpression of PDGFR-α in tumor cells (2 year progression free survival was 16.7 ± 15.2 for cases with overexpression of PDGFR-α in the tumor vs. 74.5 ± 15.2 for those with low/no expression, hazard ratio = 5.78, p = 0.04). A number of angiogenic factors are expressed in ependymoma tumor cells and tumor endothelium. Preliminary evidence suggests that the expression of PDGFRs could have a prognostic significance in ependymoma. This data suggests that PDGFRs should be further evaluated as targets using novel PDGFR inhibitors.

A Phase II study of pulse dose imatinib mesylate and weekly paclitaxel in patients aged 70 and over with advanced non-small cell lung cancer

BackgroundIn non-small cell lung cancer (NSCLC), interstitial hypertension is a barrier to chemotherapy delivery, and is mediated by platelet derived growth factor receptor (PDGFR). Antagonizing PDGFR with imatinib may improve intra-tumoral delivery of paclitaxel, increasing response rate (RR).MethodsThis single-stage, open-label phase II study evaluated pulse dose imatinib and weekly paclitaxel in elderly patients with advanced NSCLC. Eligible patients were aged ≥ 70 with untreated, stage IIIB-IV NSCLC and ECOG performance status 0-2. Primary endpoint was RR. Secondary endpoints included median progression free and overall survival (PFS, OS) and correlatives of PDGFR pathway activation. Baseline Charlson Comorbidity Index (CCI) and Vulnerable Elder Survey-13 (VES-13) were correlated with outcomes.ResultsThirty-four patients with median age 75 enrolled. Eleven of 29 (38%) were frail by VES-13 score. Overall RR was 11/34 (32%; 95% CI 17%-51%), meeting the primary endpoint. Median PFS and OS were 3.6 and 7.3 months, respectively. High tumoral PDGF-B expression predicted inferior PFS. Frail patients by VES-13 had significantly worse median PFS (3.2 vs. 4.5 months; p=0.02) and OS (4.8 vs. 12 months; p=0.02) than non-frail.ConclusionsThe combination of imatinib and paclitaxel had encouraging activity as measured by the primary endpoint of RR. However, PFS and OS were typical for elderly patients treated with single agent chemotherapy and the regimen is not recommended for further study. Adjunct imatinib did not overcome the established association of tumoral PDGF-B expression with inferior PFS. VES-13 was a powerful predictor of poor survival outcomes. Frailty should be further studied as a predictor of non-benefit from chemotherapy.Trial RegistrationClinicalTrials.gov NCT01011075

Adding to the Mix: Fibroblast Growth Factor and Platelet-Derived Growth Factor Receptor Pathways as Targets in Non – small Cell Lung Cancer

The treatment of advanced non � small cell lung cancer (NSCLC) increasingly involves the use of molecularly targeted therapy with activity against either the tumor directly, or indirectly, through activity against host-derived mechanisms of tumor support such as angiogenesis. The most well studied signaling pathway associated with angiogenesis is the vascular endothelial growth factor (VEGF) pathway, and the only antiangiogenic agent currently approved for the treatment of NSCLC is bevacizumab, an antibody targeted against VEGF. More recently, preclinical data supporting the role of fibroblast growth factor receptor (FGFR) and platelet-derived growth factor receptor (PDGFR) signaling in angiogenesis have been reported. The platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) pathways may also stimulate tumor growth directly through activation of downstream mitogenic signaling cascades. In addition, 1 or both of these pathways have been associated with resistance to agents targeting the epidermal growth factor receptor (EGFR) and VEGF. A number of agents that target FGF and/or PDGF signaling are now in development for the treatment of NSCLC. This review will summarize the potential molecular roles of PDGFR and FGFR in tumor growth and angiogenesis, as well as discuss the current clinical status of PDGFR and FGFR inhibitors in clinical development.

Potential Role of Platelet-Derived Growth Factor Receptor Inhibition Using Imatinib in Combination with Docetaxel in the Treatment of Recurrent Non-small Cell Lung Cancer

Platelet-derived growth factor receptor (PDGFR) is expressed in lung cancer and is involved in angiogenesis. Preclinical models demonstrated that imatinib (Im) regulates angiogenesis through PDGFR inhibition and enhances efficacy of chemotherapy. We hypothesized that Im plus docetaxel (D) would have a synergistic effect detectable by an increase in response rate in patients with recurrent non-small cell lung cancer (NSCLC). A phase II trial to evaluate Im in combination with D in patients with recurrent NSCLC was conducted. The primary end point was response rate, using a Simon two-stage design. Eligible patients had measurable disease and no more than two chemotherapy regimens. D was given at 30 mg/m/wk intravenously × 3 every 4 weeks and oral Im at 600 mg daily for four cycles. Patients required two cycles to be evaluable for response. Nonprogressors after four cycles continued with Im maintenance until progression or for a total of 12 months. Twenty-three patients were enrolled in the first stage. Toxicity was mainly nonhematologic. We observed one partial response (5.5%), four stable disease (22.2%), and 13 progressed (72.2%). Median time to progression was 1.9 months, and median overall survival was 6.1 months. Two patients who went on Im maintenance had time to progression of 7.78 months and 15.8 months. Im in combination with D did not achieve its primary objective of improving response rate in patients with recurrent NSCLC. An increased understanding of the complex PDGFR pathway in lung cancer and alternative strategies to inhibit it are needed.

Acrolein increases 5-lipoxygenase expression in murine macrophages through activation of ERK pathway

Episodic exposure to acrolein-rich pollutants has been linked to acute myocardial infarction, and 5-lipoxygenase (5-LO) is involved in the production of matrix metalloproteinase-9 (MMP-9), which destabilizes atherosclerotic plaques. Thus, the present study determined the effect of acrolein on 5-LO/leukotriene B 4 (LTB 4) production in murine macrophages. Stimulation of J774A.1 cells with acrolein led to increased LTB 4 production in association with increased 5-LO expression. Acrolein-evoked 5-LO expression was blocked by pharmacological inhibition of the ERK pathway, but not by inhibitors for JNK and p38 MAPK pathways. In line with these results, acrolein exclusively increased the phosphorylation of ERK among these MAPK, suggesting a role for the ERK pathway in acrolein-induced 5-LO expression with subsequent production of LTB 4. Among the receptor tyrosine kinases including epidermal growth factor receptor (EGFR) and platelet derived growth factor receptor (PDGFR), acrolein-evoked ERK phosphorylation was attenuated by AG1478, an EGFR inhibitor, but not by AG1295, a PDGFR inhibitor. In addition, acrolein-evoked 5-LO expression was also inhibited by inhibition of EGFR pathway, but not by inhibition of PDGFR pathway. These observations suggest that acrolein has a profound effect on the 5-LO pathway via an EGFR-mediated activation of ERK pathway, leading to acute ischemic syndromes through the generation of LTB 4, subsequent MMP-9 production and plaque rupture.

Kinome Profiling of Chondrosarcoma Reveals Src-Pathway Activity and Dasatinib as Option for Treatment

Chondrosarcomas are notorious for their resistance to conventional chemotherapy and radiotherapy, indicating there are no curative treatment possibilities for patients with inoperable or metastatic disease. We therefore explored the existence of molecular targets for systemic treatment of chondrosarcoma using kinome profiling. Peptide array was performed for four chondrosarcoma cell lines and nine primary chondrosarcoma cultures with GIST882, MSCs, and colorectal cancer cell lines as controls. Activity of kinases was verified using immunoblot, and active Src- and platelet-derived growth factor receptor (PDGFR) signaling were further explored using imatinib and dasatinib on chondrosarcoma in vitro. The AKT1/GSK3B pathway was clearly active in chondrosarcoma. In addition, the PDGFR pathway and the Src kinase family were active. PDGFR and Src kinases can be inhibited by imatinib and dasatinib, respectively. Although imatinib did not show any effect on chondrosarcoma cell cultures, dasatinib showed a decrease in cell viability at nanomolar concentrations in seven of nine chondrosarcoma cultures. However, inhibition of phosphorylated Src (Y419) was found both in responsive and nonresponsive cells. In conclusion, using kinome profiling, we found the Src pathway to be active in chondrosarcoma. Moreover, we showed in vitro that the inhibitor of the Src pathway, dasatinib, may provide a potential therapeutic benefit for chondrosarcoma patients who are not eligible for surgery.

Imatinib for refractory chronic graft-versus-host disease with fibrotic features

AbstractWe previously reported that patients with fibrotic, chronic graft-versus-host disease (cGVHD) have antibodies activating the platelet-derived growth factor receptor pathway. Because this pathway can be inhibited by imatinib, we performed a pilot study including 19 patients with refractory cGVHD, given imatinib at a starting dose of 100 mg per day. All patients had active cGVHD with measurable involvement of skin or other districts and had previously failed at least 2 treatment lines. Patient median age was 29 years (range, 10-62 years), and median duration of cGvHD was 37 months (range, 4-107 months). The organs involved were skin (n = 17), lung (n = 11), and bowel (n = 5); 15 patients had sicca syndrome. Imatinib-related, grade 3 to 4 toxicity included fluid retention, infections, and anemia. Imatinib was discontinued in 8 patients: in 3 because of toxicity and in 5 because of lack of response (n = 3) or relapse of malignancy (n = 2). Overall response rate at 6 months was 79%, with 7 complete remissions (CRs) and 8 partial remissions (PRs). With a median follow-up of 17 months, 16 patients are alive, 14 still in CR or PR. The 18-month probability of overall survival is 84%. This study suggests that imatinib is a promising treatment for patients with refractory fibrotic cGVHD.

Platelet-Derived Growth Factor Receptor Regulates Myeloid and Monocytic Differentiation of HL-60 Cells

Here, we show that the platelet-derived growth factor receptor (PDGFR) regulates myeloid and monocytic differentiation of HL-60 myeloblastic leukemia cells in response to retinoic acid (RA) and vitamin D3 (D3), respectively. Both RA and D3 decreased the expression of PDGFR-alpha and PDGFR-beta throughout differentiation. When cells were treated with the PDGFR inhibitor AG1296 in addition to RA or D3, signs of terminal differentiation such as inducible oxidative metabolism and cell substrate adhesion were enhanced. These changes were accompanied by an increased extracellular signal-regulated kinase 1/2 activation. AG1296 also resulted in elevated expression of differentiation markers CD11b and CD66c when administered with RA or D3. Interestingly, other markers did not follow the same pattern. Cells receiving AG1296 in addition to RA or D3 showed decreased G1-G0 arrest and CD14, CD38, and CD89 expression. We thus provide evidence that certain sets of differentiation markers can be enhanced, whereas others can be inhibited by the PDGFR pathway. In addition, we found calcium levels to be decreased by RA and D3 but increased when AG1296 was given in addition to RA or D3, suggesting that calcium levels decrease during myeloid or monocytic differentiation, and elevated calcium levels can disturb the expression of certain differentiation markers.

Stem cell-derived Sca-1+ progenitors differentiate into smooth muscle cells, which is mediated by collagen IV-integrin α1/β1/αv and PDGF receptor pathways

Embryonic stem (ES) cells can differentiate into smooth muscle cells (SMCs) that can be used for tissue engineering and repair of damaged organs. However, little is known about the molecular mechanisms of differentiation in these cells. In the present study, we found collagen IV can promote ES cells to differentiate into stem cell antigen-1-positive (Sca-1(+)) progenitor cells and SMCs. Pretreatment of ES cells with antibodies against collagen IV significantly inhibited SMC marker expression. To further elucidate the effect of collagen IV on the induction and maintenance of SMC differentiation, Sca-1(+) progenitor cells were isolated with magnetic beads, placed in collagen-IV-coated flasks, and cultured in differentiation medium with or without platelet-derived growth factor (PDGF)-BB for 6-90 days. Both immunostaining and fluorescence-activated cell sorter analyses revealed that the majority of these cells were positive for SMC-specific markers. Pretreatment of Sca-1(+) progenitors with antibodies against integrin alpha(1), alpha(v), and beta(1), but not beta(3), inhibited focal adhesion kinase (FAK) and paxillin phosphorylation and resulted in a marked inhibition of SMC differentiation. Various tyrosine kinase inhibitors, and specific siRNA for phosphatidylinositol 3-kinase (PI 3-kinase) and PDGF receptor-beta significantly inhibited SMC marker expression. Taken together, we demonstrate for the first time that collagen IV plays a crucial role in the early stage of SMC differentiation and that integrin (alpha(1), beta(1), and alpha(v))-FAK-PI 3-kinase-mitogen-activated protein kinase and PDGF receptor-beta signaling pathways are involved in SMC differentiation.