Platelet-derived Growth Factor Receptor Tyrosine Kinase Inhibitor Research Articles

In vivo Pharmacokinetics and in vitro Release of Imatinib Mesylate-Loaded Liposomes for Pulmonary Delivery.

BackgroundPulmonary arterial hypertension (PAH) is characterized by abnormal proliferation of vascular endothelial and smooth muscle cells and causes occlusion of pulmonary arterioles that eventually results in right heart failure and death. The platelet-derived growth factor (PDGF) plays a prominent role in abnormal remodeling of pulmonary resistance vessels. Imatinib mesylate (IM), a PDGF-receptor tyrosine kinase inhibitor, was able to ameliorate PAH by reversing pulmonary vascular remodeling.MethodsIn the present study, IM-loaded liposomes (IM-LPs) were developed and administered via the pulmonary route to delay the drug release and improve patient compliance for the treatment of PAH. The IM-LPs were prepared by the transmembrane gradient method with the spherical vesicles. The compatibility of the IM-LPs was studied by determining the viability of pulmonary arterial smooth muscle cells (PASMCs). Particle uptake by rat PASMCs was evaluated by incubating the particles with rat PASMCs. Pharmacokinetic studies were performed in male SD rats.ResultsThe IM-LPs showed an average size of 101.6 ± 50.80 nm with a zeta potential value of 19.66 ± 0.55 mV, a PDI of 0.250 and 81.96% ± 0.98% drug entrapment efficiency, meanwhile displayed a sustained release profile. Liposomes obviously increased intracellular accumulation of Rhodamine B by PASMCs using the fluorescence microscopic. Following intratracheal administration to rats, IM-LPs not only extended the half-life of IM, but also prolonged retention of IM compared with plain IM solution after intratracheal and intravenous administration.ConclusionThe study show potential applications of the LPs for pulmonary delivery of IM and the method for the development of LPs in sustained release of IM for better therapeutic outcomes. Conclusively, the prepared IM-LPs were well designed in nanosized ranges and may be a promising formulation for pulmonary delivery of IM.

Imatinib improves insulin resistance and inhibits injury-induced neointimal hyperplasia in high fat diet-fed mice

Imatinib, a PDGF receptor tyrosine kinase inhibitor, has been shown to suppress intimal hyperplasia in different animal models under normal metabolic milieu, diabetic, and/or hypercholesterolemic conditions. However, the impact of imatinib treatment on injury-induced neointimal hyperplasia has not yet been investigated in the setting of insulin resistance without frank diabetes. Using a mouse model of high fat diet (HFD)-induced insulin resistance and guidewire-induced arterial injury, the present study demonstrates that intraperitoneal administration of imatinib (25 mg/kg/day) for ~3 weeks resulted in a marked attenuation of neointimal hyperplasia (intima/media ratio) by ~78% (n = 6–9 per group; P < 0.05). Imatinib treatment also led to significant improvements in key metabolic parameters. In particular, imatinib improved insulin resistance and glucose tolerance, as revealed by complete inhibition of HFD-induced increase in HOMA-IR index and AUCIPGTT, respectively. In addition, imatinib treatment led to diminutions in HFD-induced increases in plasma total cholesterol and triglycerides by ~73% and ~59%, respectively. Furthermore, imatinib decreased HFD-induced increase in visceral fat accumulation by ~51% (as determined by epididymal white adipose tissue weight). Importantly, imatinib treatment in HFD-fed mice enhanced plasma levels of high-molecular-weight adiponectin by ~2-fold without affecting total adiponectin. However, there were no significant changes in mean arterial pressure in insulin-resistant state or after imatinib exposure, as measured by tail-cuff method. Together, the present findings suggest that targeting PDGF receptor tyrosine kinase using imatinib may provide a realistic treatment option to prevent injury-induced neointimal hyperplasia and diet-induced insulin resistance in obesity.

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.

Platelet-rich plasma enhances the proliferation of human adipose stem cells through multiple signaling pathways

BackgroundPlatelet-rich plasma (PRP) is an autologous blood product that contains a high concentration of several growth factors. Platelet-derived growth factor (PDGF)-BB is a potential mitogen for human adipose-derived stem cells (hASCs). PRP stimulates proliferation of hASCs; however, the signaling pathways activated by PRP remain unclear.MethodshASCs were cultured with or without PRP or PDGF-BB, and proliferation was assessed. hASCs were also treated with PRP or PDGF-BB with or without imatinib, which is a PDGF receptor tyrosine kinase inhibitor, or sorafenib, which is a multikinase inhibitor. Inhibition of cell proliferation was examined using anti-PDGF antibody (Abcam, Cambridge, UK), by cell counting. We assessed the effects of inhibitors of various protein kinases such as ERK1/2, JNK, p38, and Akt on the proliferation of hASCs.ResultsThe proliferation was remarkably promoted in cells treated with either 1% PRP or 10 ng/ml PDGF-BB, and both imatinib and sorafenib inhibited this proliferation. Anti-PDGF antibody (0.5 and 2 μg/ml) significantly decreased the proliferation of hASCs compared with control. PRP-mediated hASC proliferation was blocked by inhibitors of ERK1/2, Akt, and JNK, but not by an inhibitor of p38.ConclusionsPRP promotes hASC proliferation, and PDGF-BB in PRP plays a major role in inducing the proliferation of hASCs. PRP promotes hASC proliferation via ERK1/2, PI3K/Akt, and JNK signaling pathways.

Nanoparticle-Mediated Drug Delivery System for Pulmonary Arterial Hypertension.

Nanoparticles have been used as a novel drug delivery system. Drug-incorporated nanoparticles for local delivery might optimize the efficacy and minimize the side effects of drugs. The efficacy and safety of intratracheal administration of prostacyclin analog (beraprost) -incorporated nanoparticles and imatinib (a PDGF-receptor tyrosine kinase inhibitor) -incorporated nanoparticles in Sugen-hypoxia-normoxia or monocrotaline rat models of pulmonary arterial hypertension (PAH) and in human PAH-pulmonary arterial smooth muscle cells have been reported. The use of inhaled drug-incorporated nanoparticles might be a novel approach for the treatment of PAH.

PDGF-BB/KLF4/VEGF Signaling Axis in Pulmonary Artery Endothelial Cell Angiogenesis

Accumulating evidence suggests that platelet-derived growth factor-BB (PDGF-BB) and vascular endothelial growth factor(VEGF) play a role in the progression of pulmonary arterial hypertension (PAH).Since chronic hypoxia is responsible for intimal hyperplasia and disordered angiogenesis of pulmonary arteries, which are histological hallmarks of PAH, we explored the role of the PDGF-BB/KLF4/VEGF signaling axis in the angiogenesis of pulmonary artery endothelial cells (PAECs). Adult male Wistar rats were used to study hypoxia-induced or monocrotaline (MCT)-induced right ventricular (RV) remodeling as well as systolic function and hemodynamics using echocardiography and a pressure-volume admittance catheter. Morphometric analyses of lung vasculature and RV vessels were performed. The results revealed that both the PDGF receptor-tyrosine kinase inhibitor imatinib and the multi-targeted VEGF and PDGF receptor inhibit or sunitinib malate reversed hypoxia-induced increases in right ventricular systolic pressure (RVSP), right ventricular function and thickening of the medial walls. Mechanistically VEGF/VEGFR and PDGF/PDGFR formed a biological complex. We also showed that PDGF-BBincreasedKLF4 promoter activity transcriptionally activating VEGF expression, which regulates PAEC proliferation; migration; and the cell-cycle transition from G0/G1phase to S phase and G2/M-phase and eventually leads to PAEC angiogenesis Conclusion: Our study indicates that hypoxia-induced angiogenesis of PAECs is associated with increased levels of PDGF-BB/KLF4/VEGF, which contribute to pulmonary vascular remodeling. Overall, our study contributes to a better understanding of PAH pathogenesis.

A novel PDGF receptor inhibitor-eluting stent attenuates in-stent neointima formation in a rabbit carotid model.

A novel drug-eluting stent (DES) is required to target vascular smooth muscle cells (SMCs) without harming endothelial cells (ECs). Platelet-derived growth factor (PDGF) is critical for the proliferation and migration of SMCs. Sunitinib [a PDGF receptor (PDGFR) tyrosine kinase inhibitor]-eluting stents may therefore inhibit neointimal formation. The aim of the present study was to examine the stent-based delivery of sunitinib in a rabbit carotid model; in addition, the effects of sunitinib were evaluated in vitro. Local administration of sunitinib markedly reduced neointimal formation without delaying re-endothelialization in the carotid artery model. In vitro, sunitinib inhibited SMC proliferation; however, no effects were observed on ECs. Sunitinib caused necrosis of SMCs. In addition, sunitinib attenuated PDGF-stimulated SMC migration in a scratch wound assay and inhibited α-SMA cytoskeleton polymerization. Furthermore, sunitinib inhibited PDGF-induced phosphorylation of extracellular signal-regulated kinase in vitro and in vivo. Therefore, this novel DES may be a potential strategy for the treatment of vascular disorders.

Combination screening in vitro identifies synergistically acting KP372-1 and cytarabine against acute myeloid leukemia

Cytogenetic lesions often alter kinase signaling in acute myeloid leukemia (AML) and the addition of kinase inhibitors to the treatment arsenal is of interest. We have screened a kinase inhibitor library and performed combination testing to find promising drug-combinations for synergistic killing of AML cells. Cytotoxicity of 160 compounds in the library InhibitorSelect™ 384-Well Protein Kinase Inhibitor I was measured using the fluorometric microculture cytotoxicity assay (FMCA) in three AML cell lines. The 15 most potent substances were evaluated for dose-response. The 6 most cytotoxic compounds underwent combination synergy analysis based on the FMCA readouts after either simultaneous or sequential drug addition in AML cell lines. The 4 combinations showing the highest level of synergy were evaluated in 5 primary AML samples. Synergistic calculations were performed using the combination interaction analysis package COMBIA, written in R, using the Bliss independence model. Based on obtained results, an iterative combination search was performed using the therapeutic algorithmic combinatorial screen (TACS) algorithm. Of 160 substances, cell survival was ⩽50% at <0.5μM for Cdk/Crk inhibitor, KP372-1, synthetic fascaplysin, herbimycin A, PDGF receptor tyrosine kinase inhibitor IV and reference-drug cytarabine. KP372-1, synthetic fascaplysin or herbimycin A obtained synergy when combined with cytarabine in AML cell lines MV4-11 and HL-60. KP372-1 added 24h before cytarabine gave similar results in patient cells. The iterative search gave further improved synergy between cytarabine and KP372-1. In conclusion, our in vitro studies suggest that combining KP372-1 and cytarabine is a potent and synergistic drug combination in AML.

Delivery of imatinib-incorporated nanoparticles into lungs suppresses the development of monocrotaline-induced pulmonary arterial hypertension.

Platelet-derived growth factor (PDGF) is implicated in the pathogenesis of pulmonary arterial hypertension (PAH). Imatinib, a PDGF-receptor tyrosine kinase inhibitor, improved hemodynamics, but serious side effects and drug discontinuation are common when treating PAH. A drug delivery system using nanoparticles (NPs) enables the reduction of side effects while maintaining the effects of the drug. We examined the efficacy of imatinib-incorporated NPs (Ima-NPs) in a rat model and in human PAH-pulmonary arterial smooth muscle cells (PASMCs). Rats received a single intratracheal administration of PBS, FITC-NPs, or Ima-NPs immediately after monocrotaline injection. Three weeks after monocrotaline injection, intratracheal administration of Ima-NPs suppressed the development of pulmonary hypertension, small pulmonary artery remodeling, and right ventricular hypertrophy in the rat model of monocrotaline-induced PAH. We also examined the effects of imatinib and Ima-NPs on PDGF-induced proliferation of human PAH-PASMCs by (3)H-thymidine incorporation. Imatinib and Ima-NPs significantly inhibited proliferation after 24 hours of treatment. Ima-NPs significantly inhibited proliferation compared with imatinib at 24 hours after removal of these drugs. Delivery of Ima-NPs into lungs suppressed the development of MCT-induced PAH by sustained antiproliferative effects on PAS-MCs.

Reversal of vasohibin-driven negative feedback loop of vascular endothelial growth factor/angiogenesis axis promises a novel antifibrotic therapeutic strategy for liver diseases

Reversal of vasohibin-driven negative feedback loop of vascular endothelial growth factor/angiogenesis axis promises a novel antifibrotic therapeutic strategy for liver diseases

Thrombin Induces Epithelial-Mesenchymal Transition and Collagen Production by Retinal Pigment Epithelial Cells via Autocrine PDGF-Receptor Signaling

De-differentiation of RPE cells into mesenchymal cells (epithelial-mesenchymal transition; EMT) and associated collagen production contributes to development of proliferative vitreoretinopathy (PVR). In patients with PVR, intraocular coagulation cascade activation occurs and may play an important initiating role. Therefore, we examined the effect of the coagulation proteins factor Xa and thrombin on EMT and collagen production by RPE cells. Retinal pigment epithelial cells were stimulated with factor Xa or thrombin and the effect on zonula occludens (ZO)-1, α-smooth muscle actin (α-SMA), collagen, and platelet-derived growth factor (PDGF)-B were determined by real-time quantitative-polymerase chain reaction (RQ-PCR), immunofluorescence microscopy, and HPLC and ELISA for collagen and PDGF-BB in culture supernatants, respectively. PDGF-receptor activation was determined by phosphorylation analysis and inhibition studies using the PDGF-receptor tyrosine kinase inhibitor AG1296. Thrombin reduced ZO-1 gene expression (P < 0.05) and enhanced expression of the genes encoding α-SMA and the pro-alpha1 chain of collagen type-1 (P < 0.05), indicating EMT. Also, ZO-1 protein expression declined on thrombin stimulation, whereas production of α-SMA and collagen increased. In contrast to thrombin, factor Xa hardly stimulated EMT by RPE. Thrombin clearly induced PDGF-BB production and PDGF-Rβ chain phosphorylation in RPE. Moreover, AG1296 significantly blocked the effect of thrombin on EMT and collagen production. Our findings demonstrate that thrombin is a potent inducer of EMT by RPE via autocrine activation of PDGF-receptor signaling. Coagulation cascade-induced EMT of RPE may thus contribute to the formation of fibrotic retinal membranes in PVR and should be considered as treatment target in PVR.

Combining Molecular Targeted Drugs to Inhibit Both Cancer Cells and Activated Stromal Cells in Gastric Cancer

Recent studies have revealed that PDGF plays a role in promoting progressive tumor growth in several cancers, including gastric cancer. Cancer-associated fibroblasts, pericytes, and lymphatic endothelial cells in stroma express high levels of PDGF receptor (PDGF-R); cancer cells and vascular endothelial cells do not. Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that increases the production of proteins that stimulate key cellular processes such as cell growth and proliferation, cell metabolism, and angiogenesis. In the present study, we examined the effects of PDGF-R tyrosine kinase inhibitor (nilotinib) and mTOR inhibitor (everolimus) on tumor stroma in an orthotopic nude mice model of human gastric cancer. Expression of PDGF-B and PDGF-Rβ mRNAs was associated with stromal volume. Treatment with nilotinib did not suppress tumor growth but significantly decreased stromal reactivity, lymphatic invasion, lymphatic vessel area, and pericyte coverage of tumor microvessels. In contrast, treatment with everolimus decreased tumor growth and microvessel density but not stromal reactivity. Nilotinib and everolimus in combination reduced both the growth rate and stromal reaction. Target molecule-based inhibition of cancer-stromal cell interaction appears promising as an effective antitumor therapy.

ASCO 2013: new developments in lung cancer

At American Society of Clinical Oncology meeting 2013, some new data were presented, which might have a practice-changing potential. Epidermal growth factor receptor mutational testing was successfully performed in plasma samples, giving hope that tumor biopsies might be replaced by a more comfortable blood analysis. Some studies focused on new second-generation anaplastic lymphoma kinase inhibitors, which showed an impressive efficacy even in crizotinib refractory patients in phase I/II studies and support a sequence of tyrosine kinase inhibitors (TKIs) in this sub-entity of non-small-cell lung cancer (NSCLC). Immunological strategies are worth being tested also in lung cancer, as different strategies have proven first signs of efficacy (MUC1 antigen-specific cancer immunotherapy, programmed cell death ligand 1). Finally, a large phase III trial found that a new oral vascular endothelial growth factor receptor, fibroblast growth factor receptor, and platelet-derived growth factor receptor TKI (nintedanib) combined with docetaxel improved outcome in second-line NSCLC patients when compared with docetaxel monotherapy.

Phase II study of the multikinase inhibitor dovitinib (TKI258) or placebo in combination with fulvestrant in postmenopausal, endocrine resistant HER2-/HR+ breast cancer.

TPS1148 Background: Overcoming endocrine resistance is a critical goal in the treatment of hormone receptor−positive (HR+) breast cancer. Molecular mechanisms associated with endocrine resistance include adaptive “cross-talk” between the estrogen receptor and the fibroblast growth factor receptor (FGFR). Up to 8% of HR+/HER2- breast cancer patients (pts) have amplification of the FGFR1 gene, which is associated with resistance to endocrine therapy but can be overcome via FGFR1 inhibition in preclinical models. Dovitinib is a potent FGF, VEGF, and PDGF receptor tyrosine kinase inhibitor that demonstrated antitumor activity in heavily pretreated breast cancer pts with FGF pathway amplification (FGFR1, FGFR2, or ligand FGF3; Andre et al, ASCO 2011). Dovitinib may reverse resistance to endocrine therapy related to FGF-pathway amplification and is studied here to determine if it can improve outcomes when combined with fulvestrant. Methods: Postmenopausal HER2-/HR+ locally advanced or metastatic breast cancer pts (N»150) progressing within 12 months of completion of adjuvant endocrine therapy or after ≤ 1 prior endocrine therapy in the advanced setting will be enrolled in this multicenter, randomized, double blind, placebo controlled, phase II trial. Pts will prospectively undergo molecular screening to enrich for FGF-amplification (FGFR1, FGFR2, or FGF3 amplification by qPCR; 45 amplified and 30 non-amplified pts per arm). Pts will be randomized 1:1 to receive fulvestrant (500 mg q4w [with an additional dose 2 wks after the initial dose]) in combination with oral dovitinib (500 mg, 5 days on/2 days off) or placebo until disease progression, unacceptable toxicity, or death. The primary endpoint is progression-free survival, with tumor assessments performed q8w. Secondary endpoints include overall response rate per RECIST v1.1, duration of response, overall survival, ECOG performance status and patient reported outcome scores over time, and safety. The pharmacodynamic effect of dovitinib on FGFR-associated angiogenic pathways in tumor specimens and potential predictive biomarkers of response to dovitinib will be explored.

Stroma-Directed Molecular Targeted Therapy in Gastric Cancer

Recent studies in molecular and cellular biology have shown that tumor growth and metastasis are not determined by cancer cells alone, but also by a variety of stromal cells. Tumor stroma contains abundant extracellular matrix and several types of cells, including carcinoma-associated fibroblasts (CAFs), endothelial cells, pericytes and inflammatory cells including macrophages. In gastric cancer tissues, tumor cells express platelet-derived growth factor (PDGF)-B. Stromal cells, including CAFs, pericytes and lymphatic endothelial cells, express PDGF receptor (PDGFR)-β. Administration of PDGFR tyrosine kinase inhibitor significantly decreases stromal reaction, lymphatic vessel area and pericyte coverage of tumor microvessels. Administration of PDGFR tyrosine kinase inhibitor in combination with cytotoxic chemotherapeutic drug(s) impairs the progressive growth and metastasis of gastric cancer. Activated stroma might serve as a novel therapeutic target in cases of gastric cancer.

Platelet-derived growth factor receptor signaling activates pericyte–myofibroblast transition in obstructive and post-ischemic kidney fibrosis

Pericytes are the major source of scar-producing myofibroblasts following kidney injury; however, the mechanisms of this transition are unclear. To clarify this, we examined Collagen 1 (α1)-green fluorescent protein (GFP) reporter mice (pericytes and myofibroblasts express GFP) following ureteral obstruction or ischemia-reperfusion injury and focused on the role of platelet-derived growth factor (PDGF)-receptor (PDGFR) signaling in these two different injury models. Pericyte proliferation was noted after injury with reactivation of α-smooth muscle actin expression, a marker of the myofibroblast phenotype. PDGF expression increased in injured tubules, endothelium, and macrophages after injury, whereas PDGFR subunits α and β were expressed exclusively in interstitial GFP-labeled pericytes and myofibroblasts. When PDGFRα or PDGFRβ activation was inhibited by receptor-specific antibody following injury, proliferation and differentiation of pericytes decreased. The antibodies also blunted the injury-induced transcription of PDGF, transforming growth factor β1, and chemokine CCL2. They also reduced macrophage infiltration and fibrosis. Imatinib, a PDGFR tyrosine kinase inhibitor, attenuated pericyte proliferation and kidney fibrosis in both fibrogenic models. Thus, PDGFR signaling is involved in pericyte activation, proliferation, and differentiation into myofibroblasts during progressive kidney injury. Hence, pericytes may be a novel target to prevent kidney fibrosis by means of PDGFR signaling blockade.

Abstract 2710: KSHV-induced PDGF signaling dyregulation drives a Rac1 and ROS-mediated paracrine tumorigenic mechanism necessary for Kaposi's sarcoma

Abstract Kaposi's sarcoma (KS), caused by the Kaposi's sarcoma-associated herpesvirus (KSHV), is a major AIDS-associated malignancy characterized by angiogenesis and proliferation of spindle cells. KSHV-infected KS lesions are composed of latently-infected cells and a minority of cells expressing lytic genes such as vGPCR, which are implicated the development of KS angioproliferative phenotype via a paracrine mechanism. A key unsolved question is how this minor population of lytically-infected cells expressing vGPCR transduce an angio-proliferative phenotype to latently-infected cells. Here, we describe a Rac1 and ROS driven mechanism of paracrine amplification of viral oncogenesis in the KSHV-induced tumor model mECK36. It is triggered by vGPCR-induced PDGF secretion, which in the presence of high expression of PDGF receptors and NADPH oxidase family members caused by latent KSHV infection, leads to STAT3-mediated transcriptional activation of c-Myc, VEGF and KSHV latent genes. This paracrine loop, driven by PDGF signaling and regulated by Rac1 and ROS, amplifies vGPCR oncogenesis by driving proliferation and angiogenesis in latently-infected cells. Inhibtion of this molecular pathway by either the antioxidant N-acetylcysteine (NAC) or PDGF receptor tyrosine kinase inhibitors impair KSHV-induced tumorigenesis, angiogenesis and lymphangiogenesis, further validating this paracrine oncogenesis mechanism and its components as anti-KS tumor targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2710. doi:10.1158/1538-7445.AM2011-2710

Anti‐stromal therapy with imatinib inhibits growth and metastasis of gastric carcinoma in an orthotopic nude mouse model

Recent studies have revealed that platelet-derived growth factor (PDGF) plays a role in promoting progressive tumor growth in several organs; however, whether PDGF plays such a role in gastric carcinoma is undetermined. We examined whether inhibition of PDGF receptor (PDGF-R) tyrosine kinase signaling by imatinib affects tumor growth and metastasis in an orthotopic nude mouse model of human gastric carcinoma. TMK-1 human gastric carcinoma cells were injected into the gastric wall of nude mice. Groups of mice (n = 10 each) received sterile water (control), low-dose imatinib (50 mg/kg/day), high-dose imatinib (200 mg/kg/day), cancer chemotherapeutic agent irinotecan (5 mg/kg/week), or imatinib (50 mg/kg/day or 200 mg/kg/day) and irinotecan (5 mg/kg/week) in combination for 28 days. Tumor growth and metastasis were assessed. Resected tumors were analyzed immunohistochemically. Carcinoma-associated fibroblasts, pericytes and lymphatic endothelial cells in stroma expressed high levels of PDGF-R; carcinoma cells did not. Treatment with imatinib alone did not inhibit tumor growth and metastasis; however, treatment with irinotecan alone or combined with imatinib significantly inhibited tumor growth. Only treatment with high-dose imatinib and irinotecan in combination inhibited lymph node and peritoneal metastases. Immunohistochemically, only imatinib alone or in combination with irinotecan was shown to significantly decrease the stromal reaction, microvessel area and pericyte coverage of tumor microvessels. These effects were marked with high-dose imatinib. In conclusion, administration of PDGF-R tyrosine kinase inhibitor in combination with irinotecan appears to impair the progressive growth of gastric carcinoma by blockade of PDGF-R signaling pathways in stromal cells.

Imatinib Mesylate-Incorporated Nanoparticle-Eluting Stent Attenuates In-Stent Neointimal Formation in Porcine Coronary Arteries

The use of currently marketed drug-eluting stents (DES) presents safety concerns, including an increased risk for late thrombosis in the range of 0.6% per year in patients, including acute coronary syndrome, which is thought to result from delayed endothelial healing effects. A new DES system targeting vascular smooth muscle cells without adverse effects on endothelial cells is therefore needed. Platelet-derived growth factor (PDGF) plays a central role in the pathogenesis of restenosis; therefore, we hypothesized that imatinib mesylate (PDGF receptor tyrosine kinase inhibitor) encapsulated bioabsorbable polymeric nanoparticle (NP)-eluting stent attenuates in-stent neointima formation. Effects of imatinib-incorporated NP-eluting stent on neointima formation and endothelial healing were examined in a pig coronary artery stent model. Effects of imatinib-NP were also examined in cultured cells. In a cultured cell study, imatinib-NP attenuated the proliferation of vascular smooth muscle cells associated with inhibition of the target molecule (phosphorylation of PDGF receptor-β), but showed no effect on endothelial proliferation. In a pig coronary artery stent model, imatinib-NP-eluting stent markedly attenuated in-stent neointima formation and stenosis by approximately 50% as assessed by angiographic, histopathological, and intravascular ultrasound imaging analyses. Imatinib-NP-eluting stent also attenuated MAP kinase activity, but did not affect inflammation and re-endothelialization. These data suggest that suppression of neointima formation by a imatinib-NP-eluting stent holds promise as a molecular-targeting NP delivery system for preventing in-stent restenosis.

Expression of platelet‐derived growth factor (PDGF)‐B and PDGF‐receptor β is associated with lymphatic metastasis in human gastric carcinoma

Recent study of murine fibrosarcoma has revealed that platelet-derived growth factor (PDGF) plays a direct role in promoting lymphangiogenesis and metastatic spread to lymph nodes. Thus, we investigated the relation between PDGF and PDGF receptor (PDGF-R) expression and lymphatic metastasis in human gastric carcinoma. We examined PDGF-B and PDGF-Rβ expression in four human gastric carcinoma cell lines (TMK-1, MKN-1, MKN-45, and KKLS) and in 38 surgical specimens of gastric carcinoma. PDGF-B and PDGF-Rβ expression was examined by immunofluorescence in surgical specimens and in human gastric carcinoma cells (TMK-1) implanted orthotopically in nude mice. Groups of mice (n = 10, each) received saline (control) or PDGF-R tyrosine kinase inhibitor imatinib. PDGF-B and PDGF-Rβ mRNA expression was significantly higher in patients with lymph node metastasis than in those without and was also significantly higher in diffuse-type carcinoma than in intestinal-type carcinoma. In surgical specimens, tumor cells expressed PDGF-B, but PDGF-Rβ was expressed predominantly by stromal cells. Under culture conditions, expression of PDGF-B mRNA was found in all of the gastric cell lines, albeit at different levels. In orthotopic TMK-1 tumors, cancer cells expressed PDGF-B but not PDGF-Rβ. PDGF-Rβ was expressed by stromal cells, including lymphatic endothelial cells. Four weeks of treatment with imatinib significantly decreased the area of lymphatic vessels. Our data indicate that secretion of PDGF-B by gastric carcinoma cells and expression of PDGF-Rβ by tumor-associated stromal cells are associated with lymphatic metastasis. Blockade of PDGF-R signaling pathways may inhibit lymph node metastasis of gastric carcinoma.