Microglia-derived PDGFB promotes neuronal potassium currents to suppress basal sympathetic tonicity and limit hypertension.

Although many studies have addressed the regulatory circuits affecting neuronal activities, local non-synaptic mechanisms that determine neuronal excitability remain unclear. Here, we found that microglia prevented overactivation of pre-sympathetic neurons in the hypothalamic paraventricular nucleus (PVN) at steady state. Microglia constitutively released platelet-derived growth factor (PDGF) B, which signaled via PDGFRα on neuronal cells and promoted their expression of Kv4.3, a key subunit that conducts potassium currents. Ablation of microglia, conditional deletion of microglial PDGFB, or suppression of neuronal PDGFRα expression in the PVN elevated the excitability of pre-sympathetic neurons and sympathetic outflow, resulting in a profound autonomic dysfunction. Disruption of the PDGFBMG-Kv4.3Neuron pathway predisposed mice to develop hypertension, whereas central supplementation of exogenous PDGFB suppressed pressor response when mice were under hypertensive insult. Our results point to a non-immune action of resident microglia in maintaining the balance of sympathetic outflow, which is important in preventing cardiovascular diseases.

Improved differentiation of human adipose stem cells to insulin-producing ß-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 ß-cells. However, due to the shortage of ß-cell sources from the tissues, differentiation of pluripotent stem cells or terminally differentiated cells into ß-cell is proposed as an alternative strategy. Previously, human adipose-derived stem cells (ADSCs) were reported to be converted into ß-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 ß-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 ß-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 ß-like cells from ADSCs would provide a better opportunity for treating diabetes.

CP-673451, a Selective Platelet-Derived Growth Factor Receptor Tyrosine Kinase Inhibitor, Induces Apoptosis in Opisthorchis viverrini-Associated Cholangiocarcinoma via Nrf2 Suppression and Enhanced ROS.

Platelet-derived growth factors (PDGFs) and PDGF receptors (PDGFRs) play essential roles in promoting cholangiocarcinoma (CCA) cell survival by mediating paracrine crosstalk between tumor and cancer-associated fibroblasts (CAFs), indicating the potential of PDGFR as a target for CCA treatment. Clinical trials evaluating PDGFR inhibitors for CCA treatment have shown limited efficacy. Furthermore, little is known about the role of PDGF/PDGFR expression and the mechanism underlying PDGFR inhibitors in CCA related to Opisthorchis viverrini (OV). Therefore, we examined the effect of PDGFR inhibitors in OV-related CCA cells and investigated the molecular mechanism involved. We found that the PDGF and PDGFR mRNAs were overexpressed in CCA tissues compared to resection margins. Notably, PDGFR-α showed high expression in CCA cells, while PDGFR-ß was predominantly expressed in CAFs. The selective inhibitor CP-673451 induced CCA cell death by suppressing the PI3K/Akt/Nrf2 pathway, leading to a decreased expression of Nrf2-targeted antioxidant genes. Consequently, this led to an increase in ROS levels and the promotion of CCA apoptosis. CP-673451 is a promising PDGFR-targeted drug for CCA and supports the further clinical investigation of CP-673451 for CCA treatment, particularly in the context of OV-related cases.

GZD856, a novel potent PDGFRα/ß inhibitor, suppresses the growth and migration of lung cancer cells in vitro and in vivo.

Platelet-derived growth factor receptors (PDGFRα/ß) play critical roles in the autocrine-stimulated growth and recruitment of cancer-associated fibroblasts (CAFs) of human lung cancer cells. We have identified GZD856 as a new PDGFR inhibitor that potently inhibits PDGFRα/ß kinase activity and blocks this signaling pathway in lung cancer cells both in vitro and in vivo. GZD856 strongly suppresses the proliferation of PDGFRα-amplified H1703 (PDGFRß(-)) human lung cancer cells and demonstrates significant in vivo antitumor efficacy in a xenograft mouse model. Although GZD856 displays only limited in vitro antiproliferative efficiency against PDGFRα(-)/PDGFRß(+) A549 lung cancer cells, it efficiently inhibits the in vivo growth and metastasis of A549 cancer cells in xenograft and orthotopic models, respectively. The promising in vivo antitumor activity of GZD856 in A549 models may result from its suppression of PDGFR-related microenvironment factors, such as recruitment of CAFs and collagen content in stromal cells. GZD856 may be considered as a promising new candidate for anti-lung cancer drug development.

Additive effect by combination of Akt inhibitor, MK-2206, and PDGFR inhibitor, tyrphostin AG 1296, in suppressing anaplastic thyroid carcinoma cell viability and motility.

The phosphatidylinositol-3-kinase/Akt pathway and receptor tyrosine kinases regulate many tumorigenesis related cellular processes including cell metabolism, cell survival, cell motility, and angiogenesis. Anaplastic thyroid carcinoma (ATC) is a rare type of thyroid cancer with no effective systemic therapy. It has been shown that Akt activation is associated with tumor progression in ATC. Here we observed the additive effect between an Akt inhibitor (MK-2206) and a novel platelet-derived growth factor receptor inhibitor (tyrphostin AG 1296) in ATC therapy. We found an additive effect between MK-2206 and tyrphostin AG 1296 in suppressing ATC cell viability. The combination of MK-2206 and tyrphostin AG 1296 induces additive apoptosis, additive suppression of the Akt signaling pathway, as well as additive inhibition of cell migration and invasion of ATC cells. Furthermore, the combination of MK-2206 and tyrphostin AG 1296 induced additive suppression of ATC tumor growth in vivo. In summary, our studies suggest that the combination of Akt and receptor tyrosine kinase inhibitors may be an efficient therapeutic strategy for ATC treatment, which might shed new light on ATC therapy.

Combination antiangiogenic therapy and radiation in head and neck cancers.

Tumor angiogenesis is a hallmark of advanced cancers and promotes invasion and metastasis. Over 90% of head and neck squamous cell carcinomas (HNSCC) express angiogenic factors such as vascular endothelial growth factor (VEGF). Several preclinical studies support the prognostic implications of angiogenic markers for HNSCC and currently this is an attractive treatment target in solid tumors. Since radiotherapy is one of the most commonly used treatments for HNSCC, it is imperative to identify the interactions between antiangiogenic therapy and radiotherapy, and to develop combination therapy to improve clinical outcome. The mechanisms between antiangiogenic agents and ionizing radiation are complicated and involve many interactions between the vasculature, tumor stroma and tumor cells. The proliferation and metastasis of tumor cells rely on angiogenesis/blood vessel formation. Rapid growing tumors will cause hypoxia, which up-regulates tumor cell survival factors, such as hypoxia-inducing factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF), giving rise to more tumor proliferation, angiogenesis and increased radioresistance. Thus, agents that target tumor vasculature and new tumor vessel formation can modulate the tumor microenvironment to improve tumor blood flow and oxygenation, leading to enhanced radiosensitivity. In this review, we discuss the mechanisms of how antiangiogenic therapies improve tumor response to radiation and data that support this combination strategy as a promising method for the treatment of HNSCC in the future.