Radiation-induced effects on TGF-β and PDGF receptor signaling in cancer-associated fibroblasts

BACKGROUND

Cancer-associated fibroblasts (CAFs) consist of heterogeneous connective tissue cells and are often constituting the most abundant cell type in the tumor stroma. Radiation effects on tumor stromal components like CAFs in the context of radiation treatment is not well-described.

AIM

This study explores potential changes induced by ionizing radiation (IR) on platelet-derived growth factor (PDGF)/PDGFRs and transforming growth factor-beta (TGF-β)/TGFβRs signaling systems in CAFs.

METHODS AND RESULTS

Experiments were carried out by employing primary cultures of human CAFs isolated from freshly resected non-small cell lung carcinoma tumor tissues. CAF cultures from nine donors were treated with one high (1 × 18 Gy) or three fractionated (3 × 6 Gy) radiation doses. Alterations in expression levels of TGFβRII and PDGFRα/β induced by IR were analyzed by western blots and flow cytometry. In the presence or absence of cognate ligands, receptor activation was studied in nonirradiated and irradiated CAFs. Radiation exposure did not exert changes in expression of PDGF or TGF-β receptors in CAFs. Additionally, IR alone was unable to trigger activation of either receptor. The radiation regimens tested did not affect PDGFRβ signaling in the presence of PDGF-BB. In contrast, signaling via pSmad2/3 and pSmad1/5/8 appeared to be down-regulated in irradiated CAFs after stimulation with TGF-β, as compared with controls.

CONCLUSION

Our data demonstrate that IR by itself is insufficient to induce measurable changes in PDGF or TGF-β receptor expression levels or to induce receptor activation in CAFs. However, in the presence of their respective ligands, exposure to radiation at certain doses appear to interfere with TGF-β receptor signaling.

GIPC1 promotes tumor growth and migration in gastric cancer via activating PDGFR/PI3K/AKT signaling

The high mortality rate associated with gastric cancer (GC) has resulted in an urgent need to identify novel therapeutic targets for GC. This study aimed to investigate whether GAIP interacting protein, C terminus 1 (GIPC1) represents a therapeutic target and its regulating mechanism in GC. GIPC1 expression was elevated in GC tissues, liver metastasis tissues, and lymph node metastases. GIPC1 knockdown or GIPC1 blocking peptide blocked the platelet-derived growth factor receptor (PDGFR)/PI3K/AKT signaling pathway, and inhibited the proliferation and migration of GC cells. Conversely, GIPC1 overexpression markedly activated the PDGFR/PI3K/AKT signaling pathway, and promoted GC cell proliferation and migration. Furthermore, platelet-derived growth factor subunit BB (PDGF-BB) cytokines and the AKT inhibitor attenuated the effect of differential GIPC1 expression. Moreover, GIPC1 silencing decreased tumor growth and migration in BALB/c nude mice, while GIPC1 overexpression had contrasting effects. Taken together, our findings suggest that GIPC1 functions as an oncogene in GC and plays a central role in regulating cell proliferation and migration via the PDGFR/PI3K/AKT signaling pathway.

Unveiling Novel Avenues in mTOR-Targeted Therapeutics: Advancements in Glioblastoma Treatment

The mTOR signaling pathway plays a pivotal and intricate role in the pathogenesis of glioblastoma, driving tumorigenesis and proliferation. Mutations or deletions in the PTEN gene constitutively activate the mTOR pathway by expressing growth factors EGF and PDGF, which activate their respective receptor pathways (e.g., EGFR and PDGFR). The convergence of signaling pathways, such as the PI3K-AKT pathway, intensifies the effect of mTOR activity. The inhibition of mTOR has the potential to disrupt diverse oncogenic processes and improve patient outcomes. However, the complexity of the mTOR signaling, off-target effects, cytotoxicity, suboptimal pharmacokinetics, and drug resistance of the mTOR inhibitors pose ongoing challenges in effectively targeting glioblastoma. Identifying innovative treatment strategies to address these challenges is vital for advancing the field of glioblastoma therapeutics. This review discusses the potential targets of mTOR signaling and the strategies of target-specific mTOR inhibitor development, optimized drug delivery system, and the implementation of personalized treatment approaches to mitigate the complications of mTOR inhibitors. The exploration of precise mTOR-targeted therapies ultimately offers elevated therapeutic outcomes and the development of more effective strategies to combat the deadliest form of adult brain cancer and transform the landscape of glioblastoma therapy.

Pharmacology and Rationale for Seralutinib in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex disorder characterized by vascular remodeling and a consequent increase in pulmonary vascular resistance. The histologic hallmarks of PAH include plexiform and neointimal lesions of the pulmonary arterioles, which are composed of dysregulated, apoptosis-resistant endothelial cells and myofibroblasts. Platelet-derived growth factor receptors (PDGFR) α and β, colony stimulating factor 1 receptor (CSF1R), and mast/stem cell growth factor receptor kit (c-KIT) are closely related kinases that have been implicated in PAH progression. In addition, emerging data indicate significant crosstalk between PDGF signaling and the bone morphogenetic protein receptor type 2 (BMPR2)/transforming growth factor β (TGFβ) receptor axis. This review will discuss the importance of the PDGFR-CSF1R-c-KIT signaling network in PAH pathogenesis, present evidence that the inhibition of all three nodes in this kinase network is a potential therapeutic approach for PAH, and highlight the therapeutic potential of seralutinib, currently in development for PAH, which targets these pathways.

SHIP1 Is Present but Strongly Downregulated in T-ALL, and after Restoration Suppresses Leukemia Growth in a T-ALL Xenotransplantation Mouse Model

Acute lymphoblastic leukemia (ALL) is the most common cause of cancer-related death in children. Despite significantly increased chances of cure, especially for high-risk ALL patients, it still represents a poor prognosis for a substantial fraction of patients. Misregulated proteins in central switching points of the cellular signaling pathways represent potentially important therapeutic targets. Recently, the inositol phosphatase SHIP1 (SH2-containing inositol 5-phosphatase) has been considered as a tumor suppressor in leukemia. SHIP1 serves as an important negative regulator of the PI3K/AKT signaling pathway, which is frequently constitutively activated in primary T-ALL. In contrast to other reports, we show for the first time that SHIP1 has not been lost in T-ALL cells, but is strongly downregulated. Reduced expression of SHIP1 leads to an increased activation of the PI3K/AKT signaling pathway. SHIP1-mRNA expression is frequently reduced in primary T-ALL samples, which is recapitulated by the decrease in SHIP1 expression at the protein level in seven out of eight available T-ALL patient samples. In addition, we investigated the change in the activity profile of tyrosine and serine/threonine kinases after the restoration of SHIP1 expression in Jurkat T-ALL cells. The tyrosine kinase receptor subfamilies of NTRK and PDGFR, which are upregulated in T-ALL subgroups with low SHIP1 expression, are significantly disabled after SHIP1 reconstitution. Lentiviral-mediated reconstitution of SHIP1 expression in Jurkat cells points to a decreased cellular proliferation upon transplantation into NSG mice in comparison to the control cohort. Together, our findings will help to elucidate the complex network of cell signaling proteins, further support a functional role for SHIP1 as tumor suppressor in T-ALL and, much more importantly, show that full-length SHIP1 is expressed in T-ALL samples.

Patent landscape of platelet growth factor receptor and c-KIT targets

Type III receptor tyrosine kinase, e.g., PDGFR, are associated with various autoimmune diseases. To show the status of PDGFR and c-KIT targets, we performed the US patent analysis. The present study showed that the R&D of c-KIT target was much earlier than the R&D of PDGFR targets. Currently, the PDGFR-based target demonstrates more applications in the development of biological therapy. Our findings indicated that some inhibitors of c-KIT target contained sulfur elements or 1,3-diazine rings. The c-KIT target has more competitive edges for chemical drug discovery than the PDGFR target. c-KIT and PDGFR targets are currently preferable for drug discovery in autoimmune diseases. This study was the first to show R&D differentiation between PDGFR and c-KIT targets in drug development.

Research progress on the role of PDGF/PDGFR in type 2 diabetes

Platelet-derived growth factors (PDGFs) are basic proteins stored in the α granules of platelets. PDGFs and their receptors (PDGFRs) are widely expressed in platelets, fibroblasts, vascular endothelial cells, platelets, pericytes, smooth muscle cells and tumor cells. The activation of PDGFR plays a number of critical roles in physiological functions and diseases, including normal embryonic development, cellular differentiation, and responses to tissue damage. In recent years, emerging experimental evidence has shown that activation of the PDGF/PDGFR pathway is involved in the development of diabetes and its complications, such as atherosclerosis, diabetic foot ulcers, diabetic nephropathy, and retinopathy. Research on targeting PDGF/PDGFR as a treatment has also made great progress. In this mini-review, we summarized the role of PDGF in diabetes, as well as the research progress on targeted diabetes therapy, which provides a new strategy for the treatment of type 2 diabetes.

Activated EGFR and PDGFR internalize in separate vesicles and downstream AKT and ERK1/2 signaling are differentially impacted by cholesterol depletion

The interplay between membrane subregions and receptor tyrosine kinases (RTK) will influence signaling in both normal and pathological RTK conditions. In this study, epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor β (PDGFR-β) internalizations were investigated by immunofluorescent microscopy following simultaneous treatment with EGF and PDGF-BB. We found that the two receptors utilize separate routes of internalization, which merges in a common perinuclear endosomal compartment after 45 min of stimulation. This is further strengthened when contrasting the recruitment of either EGFR or PDGFR-β to either clathrin or caveolin-1: PDGFR-β dissociates from caveolin-1 upon stimulation, and engages clathrin, whilst an increased recruitment of EGFR, to both clathrin and caveolin-1, was observed upon EGF stimulation. The association between EGFR and caveolin-1 is supported by the observation that EGFR was localized in lipid raft associated fractions, whereas PDGFR-β was not. We also found that disruption of lipid rafts using MβCD led to an increased EGFR dimerization and phosphorylation in response to ligand, as well as a dramatic decrease in AKT- and a smaller but robust decrease in ERK1/2 phosphorylation. This suggest that lipid rafts may be important to effectively connect the EGFR with downstream proteins to facilitate signaling. Our data implies that cholesterol depletion of the plasma membrane affect the signaling of EGFR and PDGFRβ differently.

Precision Oncology in Gastrointestinal Stromal Tumors

GIST (gastrointestinal stromal tumors) represent 20% of sarcomatous tumors and 1-2% of primary gastrointestinal cancers. They have an excellent prognosis when localized and resectable, though their prognosis is poor in the metastatic setting, with limited options after the second line until recently. Four lines are now standard in KIT-mutated GIST and one in PDGFRA-mutated GIST. An exponential growth of new treatments is expected in this era of molecular diagnostic techniques and systematic sequencing. Currently, the main challenge remains the emergence of resistance linked to secondary mutations caused by selective pressure induced by TKIs. Repeating biopsies to tailor treatments might be a step in the right direction, and liquid biopsies at progression may offer a non-invasive alternative. New molecules with wider KIT inhibition are under investigation and could change the catalog and the sequence of existing treatments. Combination therapies may also be an approach to overcome current resistance mechanisms. Here, we review the current epidemiology and biology of GIST and discuss future management options, with an emphasis on genome-oriented therapies.

Growth factor receptor signaling induces mitophagy through epitranscriptomic regulation

Aberrant growth factor receptor signaling is among the most common oncogenic drivers in cancer biology. Receptor signaling classically induces cancer growth through signaling cascades that mediate effects largely through transcriptional control. Recently, post-transcriptional RNA modifications, collectively designated as epitranscriptomics, have emerged as a critical layer of dysregulation in cancer biology. We recently reported that PDGFR (platelet-derived growth factor receptor) activity in cancer stem cells (CSCs) derived from glioblastoma patients displays increased post-transcriptional mRNA methylation (N6-methyladenosine [m6A]), which promotes CSC maintenance through regulation of mitophagy. Specifically, PDGF-PDGFRB signaling upregulates the expression of the m6A methyltransferase METTL3, which then decorates the mitophagy regulator OPTN (optineurin) mRNA with m6A, thereby promoting OPTN mRNA degradation. Glioblastomas express lower levels of OPTN than normal brain, and forced expression of OPTN reduces tumor growth, supporting a tumor suppressive role for OPTN. Pharmacological targeting of METTL3 with PDGFR or activation of mitophagy demonstrates a combinatorial benefit. Collectively, our results suggest that upstream regulation of mitophagy in lethal cancers is mediated through growth factor receptor control of post-transcriptional RNA regulation, offering novel therapeutic paradigms.

Prognostic Value of WNT1, NOTCH1, PDGFRβ, and CXCR4 in Oral Squamous Cell Carcinoma

BACKGROUND/AIM

The biological behaviour of oral squamous cell carcinoma (OSCC) might be an effect of aberrant activation of several signalling pathways, like WNT and NOTCH pathways. The purpose of this study was to investigate the prognostic significance of WNT1 and NOTCH1 in patients with OSCC in relation to pro-angiogenic factors (PDGFRβ, CXCR4).

MATERIALS AND METHODS

Immunohistochemistry was performed in 60 OSCC tissue samples to compare WNT1, NOTCH1, PDGFRβ, and CXCR4 expression and correlate it with clinicopathological parameters.

RESULTS

Immunoreactivity of WNT1, NOTCH1, PDGFRβ, and CXCR4 was found in 51.7%, 25.0%, 63.3%, and 70.0% of the patients, respectively. WNT1 expression was positively correlated with NOTCH1 (r=0.269, p=0.037) and CXCR4 (r=0.268, p=0.038). Positive correlation was observed also between NOTCH1 and CXCR4 (r=0.493, p<0.001). WNT1 and PDGFRβ expression was significantly associated with shorter overall survival (p=0.042, p=0.033, respectively). Multivariate Cox regression model revealed that WNT1 and CXCR4 were independent prognostic factors (p=0.009, p=0.021, respectively).

CONCLUSION

WNT1 and NOTCH1 expression is associated with CXCR4 expression in OSCC, suggesting that WNT and NOTCH pathways are important in oral tumour angiogenesis. Moreover, WNT1 and CXCR4 could serve as independent prognostic factors for patients with OSCC.

Repurposing Antipsychotic Agents Against Targets of Angiogenesis Pathways for Cancer Therapy: An in-silico Approach

BACKGROUND

Antipsychotics interfere with virtually all hallmarks of cancer, including angiogenesis. Vascular endothelial growth factor receptors (VEGFRs) and platelet-derived growth receptors (PDGFRs) play crucial roles in angiogenesis and represent targets of many anti-cancer agents. We assessed and compared the binding effects of antipsychotics and receptor tyrosine kinase inhibitors (RTKIs) on VEGFR2 and PDGFRα.

METHODS

FDA-approved antipsychotics and RTKIs were retrieved from DrugBank. VEGFR2 and PDGFRα structures were obtained from Protein Data Bank and loaded on Biovia Discovery Studio software to remove nonstandard molecules. Molecular docking was carried out using PyRx and CBDock to determine the binding affinities of protein-ligand complexes.

RESULTS

Risperidone exerted the highest binding effect on PDGFRα (-11.0 Kcal/mol) as compared to other antipsychotic drugs and RTKIs. Risperidone also demonstrated a stronger binding effect on VEGFR2 (-9.6 Kcal/mol) than the RTKIs, pazopanib (-8.7 Kcal/mol), axitinib (-9.3 Kcal/mol), vandetanib (-8.3 Kcal/mol), lenvatinib ( -7.6 Kcal/mol) and sunitinib (-8.3 Kcal/mol). Sorafenib (an RTKI), however, exhibited the highest VEGFR2 binding affinity of -11.7 Kcal/mol.

CONCLUSION

Risperidone's superior binding affinity with PDGFRα when compared to all reference RTKIs and antipsychotic drugs, as well as its stronger binding effect on VEGFR2 over the RTKIs, sunitinib, pazopanib, axitinib, vandetanib, and lenvatinib, imply that it could be repurposed to inhibit angiogenic pathways and subjected to pre-clinical and clinical trials for cancer therapy.

To Investigate Growth Factor Receptor Targets and Generate Cancer Targeting Inhibitors

Receptor tyrosine kinase (RTK) regulates multiple pathways, including Mitogenactivated protein kinases (MAPKs), PI3/AKT, JAK/STAT pathway, etc. which has a significant role in the progression and metastasis of tumor. As RTK activation regulates numerous essential bodily processes, including cell proliferation and division, RTK dysregulation has been identified in many types of cancers. Targeting RTK is a significant challenge in cancer due to the abnormal upregulation and downregulation of RTK receptors subfamily EGFR, FGFR, PDGFR, VEGFR, and HGFR in the progression of cancer, which is governed by multiple RTK receptor signalling pathways and impacts treatment response and disease progression. In this review, an extensive focus has been carried out on the normal and abnormal signalling pathways of EGFR, FGFR, PDGFR, VEGFR, and HGFR and their association with cancer initiation and progression. These are explored as potential therapeutic cancer targets and therefore, the inhibitors were evaluated alone and merged with additional therapies in clinical trials aimed at combating global cancer.

Ripretinib in advanced gastrointestinal stromal tumors: an overview of current evidence and drug approval

Over the past 20 years, the management of gastrointestinal stromal tumors has acted as an important model in the advancement of molecularly targeted therapies for solid tumors. The success of imatinib has established it as a lasting therapy in the management of early-stage and advanced disease in the first-line setting. Imatinib resistance inevitably develops, resulting in the need for further lines of therapy. Ripretinib is an orally administered switch-control tyrosine kinase inhibitor, specifically developed to target both primary and secondary KIT and PDGFRα resistance mutations. Herein, the authors discuss the molecular rationale, the preclinical evidence and the clinical use of ripretinib in the treatment of gastrointestinal stromal tumors in the advanced stages of disease.

Acetabular Reaming Is a Reliable Model to Produce and Characterize Periarticular Heterotopic Ossification of the Hip

Heterotopic ossification (HO) is a pathologic process characterized by the formation of bone tissue in extraskeletal locations. The hip is a common location of HO, especially as a complication of arthroplasty. Here, we devise a first-of-its-kind mouse model of post-surgical hip HO and validate expected cell sources of HO using several HO progenitor cell reporter lines. To induce HO, an anterolateral surgical approach to the hip was used, followed by disclocation and acetabular reaming. Animals were analyzed with high-resolution roentgenograms and micro-computed tomography, conventional histology, immunohistochemistry, and assessments of fluorescent reporter activity. All the treated animals' developed periarticular HO with an anatomical distribution similar to human patients after arthroplasty. Heterotopic bone was found in periosteal, inter/intramuscular, and intracapsular locations. Further, the use of either PDGFRα or scleraxis (Scx) reporter mice demonstrated that both cell types gave rise to periarticular HO in this model. In summary, acetabular reaming reproducibly induces periarticular HO in the mouse reproducing human disease, and with defined mesenchymal cellular contributors similar to other experimental HO models. This protocol may be used in the future for further detailing of the cellular and molecular mediators of post-surgical HO, as well as the screening of new therapies.

Diverse roles of tumor-stromal PDGFB-to-PDGFRβ signaling in breast cancer growth and metastasis

Over the last couple of decades, it has become increasingly apparent that the tumor microenvironment (TME) mediates every step of cancer progression and solid tumors are only able to metastasize with a permissive TME. This intricate interaction of cancer cells with their surrounding TME, or stroma, is becoming more understood with an ever greater knowledge of tumor-stromal signaling pairs such as platelet-derived growth factors (PDGF) and their cognate receptors. We and others have focused our research efforts on understanding how tumor-derived PDGFB activates platelet-derived growth factor receptor beta (PDGFRβ) signaling specifically in the breast cancer TME. In this chapter, we broadly discuss PDGF and PDGFR expression patterns and signaling in normal physiology and breast cancer. We then detail the expansive roles played by the PDGFB-to-PDGFRβ signaling pathway in modulating breast tumor growth and metastasis with a focus on specific cellular populations within the TME, which are responsive to tumor-derived PDGFB. Given the increasingly appreciated importance of PDGFB-to-PDGFRβ signaling in breast cancer progression, specifically in promoting metastasis, we end by discussing how therapeutic targeting of PDGFB-to-PDGFRβ signaling holds great promise for improving current breast cancer treatment strategies.

Germline Variants in Angiogenesis-Related Genes Contribute to Clinical Outcome in Head and Neck Squamous Cell Carcinoma

Simple Summary

A high risk of relapse and treatment resistance are among the major challenges in locally advanced head and neck squamous cell carcinoma (HNSCC). Data show that common germline alterations in genes regulating angiogenesis may modulate treatment sensitivity, cancer progression, and prognosis, but relatively little is known about their role in HNSCC. Thus, our goal was to examine the effect of variation in these genes on survival outcomes in HNSCC patients receiving radiotherapy and cisplatin-based chemoradiotherapy. We identified genetic variants significantly affecting therapy results, constituting independent prognostic factors in these patients. Our results suggest that some polymorphisms in angiogenesis genes may be determinants of treatment efficacy and tumor aggressiveness in HNSCC, which may be of importance in standard therapy. These findings emphasize the potential value of the host genetic profile related to angiogenesis in assessing the risk of treatment failure.

Abstract

Fibroblast growth factor (FGF)/FGF receptor (FGFR), and platelet-derived growth factor (PDGF)/PDGF receptor (PDGFR) systems, as well as some matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), are involved in various steps of angiogenesis. Data indicate that common germline variations in angiogenesis-regulating genes may modulate therapy results and cancer progression. However, whether these variants affect clinical outcome in head and neck squamous cell carcinoma (HNSCC) is unclear. Hence, we assessed the relationship between FGF/FGFR, PDGF/PDGFR, MMP, and TIMP genetic variants and treatment outcomes in HNSCC patients receiving radiotherapy (RT) alone or combined with cisplatin-based chemotherapy. In multivariate analysis, FGF2 rs1048201 CC homozygotes showed a higher risk of death (p = 0.039), while PDGFRA rs2228230 T was strongly associated with an increased risk of locoregional relapse (HR 2.49, p = 0.001) in the combination treatment subgroup. In the RT alone subset, MMP2 rs243865 TT carriers had a higher risk of locoregional recurrence (HR 2.92, p = 0.019), whereas PDGFRB rs246395 CC homozygotes were at increased risk of metastasis (HR 3.06, p = 0.041). The MMP2 rs7201 C and TIMP2 rs7501477 T were associated with a risk of locoregional failure in the entire cohort (p = 0.032 and 0.045, respectively). Furthermore, rs1048201, rs2228230, rs246395, rs243865, rs7201, and rs7201/rs7501477 were independent indicators of an unfavorable outcome. This study demonstrates that the FGF2, PDGFRA, PDGFRB, MMP2, and TIMP2 variants may contribute to treatment failure and poor prognosis in HNSCC.

Phase I/Ib study of crenolanib with ramucirumab and paclitaxel as second-line therapy for advanced esophagogastric adenocarcinoma

PURPOSE

Paclitaxel plus ramucirumab is a standard second-line regimen for patients with advanced gastric adenocarcinoma, but clinical benefit remains modest. One potential resistance mechanism to VEGFR2 inhibition is activation of the PDGF/PDGFR pathway, which can be blocked by the selective inhibitor crenolanib. Therefore, we performed a phase I/Ib study of crenolanib in combination with paclitaxel/ramucirumab.

METHODS

Patients with metastatic esophagogastric adenocarcinoma refractory to first-line therapy received escalating doses of crenolanib [60 mg twice daily (BID) to 100 mg three times daily (TID)] in combination with paclitaxel 80 mg/m2 intravenously on days 1, 8 and 15 and ramucirumab 8 mg/kg intravenously on days 1 and 15 of a 28-day cycle. The primary objective was to determine the maximally tolerated dose (MTD) of crenolanib. Additional patients were enrolled in the dose expansion cohort to assess 6-month progression-free survival (PFS) at the MTD.

RESULTS

We enrolled 19 patients in the dose escalation phase and 8 patients in the dose expansion phase at the MTD of crenolanib 100 mg BID. Common grade 3/4 treatment-emergent adverse events included leukopenia (19%), anemia (11%) and neutropenia (11%). In the 14 patients treated at the MTD, 6-month PFS was 43% [95% confidence interval (CI) 23-78%] and the objective response rate (ORR) was 42% (95% CI 15-72%). The trial was terminated early due to withdrawal of crenolanib by the sponsor.

CONCLUSIONS

The addition of crenolanib to paclitaxel/ramucirumab is safe and well-tolerated at a dose level up to 100 mg BID.

CLINICAL TRIAL REGISTRATION

NCT03193918. June 19, 2017.

Imatinib mesylate inhibits androgen-independent PC-3 cell viability, proliferation, migration, and tumor growth by targeting platelet-derived growth factor receptor-α

AIM

The abnormal expression of oncogenic tyrosine kinase receptors such as platelet-derived growth factor receptors (PDGFRs) has been reported in cancer progression. However, the role of PDGFRs in the human androgen-independent prostate cancer PC-3 cell line is not well understood. Thus, this study examined the role of PDGFRs in androgen-independent PC-3 cells.

MAIN METHODS

PDGFR mRNA and protein expression was determined by quantitative real-time PCR and western blotting, respectively. The effects of the tyrosine kinase inhibitor imatinib (imatinib mesylate) and small interfering RNAs (siRNAs) were determined by a Cell Counting Kit-8 assay, bromodeoxyuridine assay, and Transwell migration assay. The in vivo effect of imatinib was analyzed using a tumor formation assay in nude mice.

KEY FINDINGS

PDGFRα was upregulated in androgen-independent PC-3 cells compared with normal prostate epithelial cells. PDGF-BB induced the phosphorylation of PDGFRα and downstream signaling molecules, including Akt, in a dose-dependent manner. Imatinib reduced the phosphorylation of the PDGFRα/Akt axis. Imatinib also suppressed the viability, proliferation, migration, and tumor growth of PC-3 cells. PDGFRα knockdown by siRNA decreased the viability and migration of PC-3 cells.

SIGNIFICANCE

These results demonstrated the distinct contribution of PDGFRα signaling to the proliferation and migration of PC-3 cells and suggested the potential for PDGFRα as a therapeutic target for metastatic and androgen-independent prostate cancer.

How the structural properties of the indole derivatives are important in kinase targeted drug design?: A case study on tyrosine kinase inhibitors

Kinases are considered as important signalling enzymes that illustrate 20% of the druggable genome. Human kinase family comprises >500 protein kinases and about 20 lipid kinases. Protein kinases are responsible for the mechanism of protein phosphorylation. These are necessary for regulation of various cellular activities including proliferation, cell cycle, apoptosis, motility, growth, differentiation, etc. Their deregulation leads to disruption of many cellular processes leading to different diseases most importantly cancer. Thus, kinases are considered as valuable targets in different types of cancer as well as other diseases. Researchers around the world are actively engaged in developing inhibitors based on distinct chemical scaffolds. Indole represents as a versatile scaffold in the naturally occurring and bioactive molecules. It is also used as a privileged scaffold for the target-based drug design against different diseases. This present article aim to review the applications of indole scaffold in the design of inhibitors against different tyrosine kinases such as epidermal growth factor receptors (EGFRs), vascular endothelial growth factor receptors (VEGFRs), platelet-derived growth factor receptors (PDGFRs), etc. Important structure activity relationships (SARs) of indole derivatives were discussed. The present work is an attempt to summarize all the crucial structural information which is essential for the development of indole based tyrosine kinase inhibitors with improved potency.

Label-Free Electrochemical Detection of the Cancer Biomarker Platelet-Derived Growth Factor Receptor in Human Serum and Cancer Cells

Overexpression of the platelet-derived growth factor receptor (PDGFR) was already associated with the loss of p53 function as cancer progresses in lung, breast, and cervical cancers. Cancer biomarker detection has faced challenges and barriers due to various limitations, including a high limit of detection, low sensitivity, time-consuming techniques, and expensive equipment. Hence, the present investigation is designed to develop a cost-effective novel biosensor based on a charge-based affinity bait molecule to detect the PDGFR, thus overcoming the limitations and challenges with an immune technique based on antigen-antibody interactions. We employed EDC-NHS coupling between poly (diallyl dimethylammonium chloride) and poly(acrylic acid) to attach the multiwall carbon nanotube surface. As a result, we performed electrochemical PDGFR conversion sensing with a dynamic range of 1-10,000 ng/mL and a detection limit of 1.5 pg/mL, which is comparable to the best current results. The biosensor also displayed good selectivity, 2.51% repeatability (RSD, n = 5), and 30 days of stability. Our study provides a pathway for the design of diagnostic interfaces in biosystems, as well as the emergence of new sensor types based on ligand-receptor interactions.

TORREY, a Phase 2 study to evaluate the efficacy and safety of inhaled seralutinib for the treatment of pulmonary arterial hypertension

Aberrant kinase signaling that involves platelet-derived growth factor receptor (PDGFR) α/β, colony stimulating factor 1 receptor (CSF1R), and stem cell factor receptor (c-KIT) pathways may be responsible for vascular remodeling in pulmonary arterial hypertension. Targeting these specific pathways may potentially reverse the pathological inflammation, cellular proliferation, and fibrosis associated with pulmonary arterial hypertension progression. Seralutinib (formerly known as GB002) is a novel, potent, clinical stage inhibitor of PDGFRα/β, CSF1R, and c-KIT delivered via inhalation that is being developed for patients with pulmonary arterial hypertension. Here, we report on an ongoing Phase 2 randomized, double-blind, placebo-controlled trial (NCT04456998) evaluating the efficacy and safety of seralutinib in subjects with World Health Organization Group 1 Pulmonary Hypertension who are classified as Functional Class II or III. A total of 80 subjects will be enrolled and randomized to receive either study drug or placebo for 24 weeks followed by an optional 72-week open-label extension study. The primary endpoint is the change from baseline to Week 24 in pulmonary vascular resistance by right heart catheterization. The secondary endpoint is the change in distance from baseline to Week 24 achieved in the 6-min walk test. A computerized tomography sub-study will examine the effect of seralutinib on pulmonary vascular remodelling. A separate heart rate monitoring sub-study will examine the effect of seralutinib on cardiac effort during the 6-min walk test.

Increased abundance of Cbl E3 ligases alters PDGFR signaling in recessive dystrophic epidermolysis bullosa

In recessive dystrophic epidermolysis bullosa (RDEB), loss of collagen VII, the main component of anchoring fibrils critical for epidermal-dermal cohesion, affects several intracellular signaling pathways and leads to impaired wound healing and fibrosis. In skin fibroblasts, wound healing is also affected by platelet-derived growth factor receptor (PDGFR) signaling. To study a potential effect of loss of collagen VII on PDGFR signaling we performed unbiased disease phosphoproteomics. Whereas RDEB fibroblasts exhibited an overall weaker response to PDGF, Cbl E3 ubiquitin ligases, negative regulators of growth factor signaling, were stronger phosphorylated. This increase in phosphorylation was linked to higher Cbl mRNA and protein levels due to increased TGFβ signaling in RDEB. In turn, increased Cbl levels led to increased PDGFR ubiquitination, internalization, and degradation negatively affecting MAPK and AKT downstream signaling pathways. Thus, our results indicate that elevated TGFβ signaling leads to an attenuated response to growth factors, which contributes to impaired dermal wound healing in RDEB.

Prognostic implications of epidermal and platelet-derived growth factor receptor alterations in 2 cohorts of IDHwt glioblastoma

Background

Glioblastoma remains a deadly brain cancer with dismal prognosis. Genetic alterations, including IDH mutations, 1p19q co-deletion status and MGMT promoter methylation have been proven to be prognostic and predictive to response to treatment in gliomas. In this manuscript, we aimed to correlate other mutations and genetic alterations with various clinical endpoints in patients with IDH-wild-type (IDHwt) glioblastoma.

Methods

We compiled a comprehensive clinically annotated database of IDHwt GBM patients treated at the Ohio State University Wexner Medical Center for whom we had mutational data through a CLIA-certified genomic laboratory. We then added data that is publicly available from Memorial Sloan Kettering Cancer Center through cBioPortal. Each of the genetic alterations (mutations, deletions, and amplifications) served as a variable in univariate and multivariate Cox proportional hazard models.

Results

A total of 175 IDHwt GBM patients with available MGMT promoter methylation data from both cohorts were included in the analysis. As expected, MGMT promoter methylation was significantly associated with improved overall survival (OS). Median OS for MGMT promoter methylated and unmethylated GBM was 26.5 and 18 months, respectively (HR 0.45; P = .003). Moreover, EGFR/ERBB alterations were associated with favorable outcome (HR of 0.37 (P = .003), but only in MGMT promoter unmethylated GBM. We further found that patients with EGFR/ERBB alterations who also harbored PDGFRA amplification had a significantly worse outcome (HR 7.89; P = .025).

Conclusions

Our data provide further insight into the impact of genetic alterations on various clinical outcomes in IDHwt GBM in 2 cohorts of patients with detailed clinical information and inspire new therapeutic strategies for IDHwt GBM.

Synthesis, biological evaluation and molecular docking of new sulfonamide-based indolinone derivatives as multitargeted kinase inhibitors against leukemia

Series of novel sulfonamide-based 3-indolinones 3a-m and 4a-f were designed, synthesized and then their cytotoxic activity was evaluated against a panel of sixty cancer cell lines. This screening indicated that 4-(2-(5-fluoro-2-oxoindolin-3-ylidene)acetyl)phenyl benzenesulfonate (4f) possessed promising cytotoxicity against CCRF-CEM and SR leukemia cell lines with IC₅₀ values 6.84 and 2.97 µM, respectively. Further investigation of the leukemic cytotoxicity of compound 4f was carried out by performing PDGFRα, VEGFR2, Aurora A/B and FLT3 enzyme assays and CCRF-CEM and SR cell cycle analysis. These investigations showed that compound 4f exhibited pronounced dual inhibition of both kinases PDGFRα and Aurora A with potency of 24.15 and 11.83 nM, respectively. The in vitro results were supported by molecular docking studies in order to explore its binding affinity and its key amino acids interactions. This work represents compound 4f as a promising anticancer agent against leukemia.

CD155: A Key Receptor Playing Diversified Roles

Cluster of differentiation (CD155), formerly identified as poliovirus receptor (PVR) and later as immunoglobulin molecule involved in cell adhesion, proliferation, invasion and migration. It is a surface protein expressed mostly on normal and transformed malignant cells. The expression of the receptor varies based on the origin of tissue. The expression of the protein is determined by factors involved in sonic hedgehog pathway, Ras-MEK-ERK pathway and during stress conditions like DNA damage response. The protein uses alternate splicing mechanism, producing four isoforms - two being soluble (CD155β and CD155γ) and two being transmembrane protein (CD155α and CD155δ). Apart from being a viral receptor, researchers have identified CD155 having important roles in cancer research and cell signaling field. The receptor is recognized as biomarker for identifying cancerous tissue. The receptor interacts with molecules involved in cells defense mechanism. The immune-surveillance role of CD155 is being deciphered to understand the mechanistic approach it utilizes as onco-immunologic molecule. CD155 is a non-MHC-I ligand which helps in identifying non-self to NK cells via an inhibitory TIGIT ligand. The TIGIT-CD155 pathway is a novel MHC-I-independent education mechanism for cell tolerance and activation of NK cell. The receptor also has a role in metastasis of cancer and trans endothelial mechanism. In this review, authors discuss the virus-host interaction that occurs via single transmembrane receptor, the poliovirus infection pathway, which is being exploited as therapeutic pathway. The oncolytic virotherapy is now promising way for curing cancer.

Syndecan Transmembrane Domain Specifically Regulates Downstream Signaling Events of the Transmembrane Receptor Cytoplasmic Domain

Despite the known importance of the transmembrane domain (TMD) of syndecan receptors in cell adhesion and signaling, the molecular basis for syndecan TMD function remains unknown. Using in vivo invertebrate models, we found that mammalian syndecan-2 rescued both the guidance defects in C. elegans hermaphrodite-specific neurons and the impaired development of the midline axons of Drosophila caused by the loss of endogenous syndecan. These compensatory effects, however, were reduced significantly when syndecan-2 dimerization-defective TMD mutants were introduced. To further investigate the role of the TMD, we generated a chimera, 2eTPC, comprising the TMD of syndecan-2 linked to the cytoplasmic domain of platelet-derived growth factor receptor (PDGFR). This chimera exhibited SDS-resistant dimer formation that was lost in the corresponding dimerization-defective syndecan-2 TMD mutant, 2eT(GL)PC. Moreover, 2eTPC specifically enhanced Tyr 579 and Tyr 857 phosphorylation in the PDGFR cytoplasmic domain, while the TMD mutant failed to support such phosphorylation. Finally, 2eTPC, but not 2eT(GL)PC, induced phosphorylation of Src and PI3 kinase (known downstream effectors of Tyr 579 phosphorylation) and promoted Src-mediated migration of NIH3T3 cells. Taken together, these data suggest that the TMD of a syndecan-2 specifically regulates receptor cytoplasmic domain function and subsequent downstream signaling events controlling cell behavior.

Insight on a new indolinone derivative as an orally bioavailable lead compound against renal cell carcinoma

A series of novel 3-indolinone-thiazolidinones and oxazolidinones 4a-k was synthesized via molecular hybridization approach and sequentially evaluated to explore its cytotoxic activity. The cytotoxicity screening pointed toward the N-cyclohexyl thiazolidinone derivative 4f that revealed promising renal cytotoxicity against CAKI-1 and UO-31 renal cancer cell lines with IC₅₀ values 4.74 and 3.99 µM, respectively, which were comparable to those of sunitinib along with good safety threshold against normal renal cells. Further emphasis on compound 4f renal cytotoxicity was achieved via different enzyme assays and CAKI-1 and UO-31 cell cycle analysis. The results were supported by in silico studies to explore its physicochemical, pharmacokinetic and drug-likeness properties. Finally, compound 4f was subjected to an in vivo pharmacokinetic study through two different routes of administration showing excellent oral bioavailability. This research represents compound 4f as a promising candidate against renal cell carcinoma.

Gastrointestinal stromal tumor: a review of current and emerging therapies

Gastrointestinal stromal tumors (GIST) are rare neoplasms arising from the interstitial cell of Cajal in the gastrointestinal tract. Two thirds of GIST in adult patients have c-Kit mutation and smaller fractions have platelet derived growth factor receptor alpha (PDGFRA) mutation. Surgery is the only curative treatment for localized disease. Imatinib improves survival when used adjuvantly and in advanced disease. Several targeted therapies have also improved survival in GIST patients after progression on imatinib including sunitinib and regorafenib. Recently, United States Federal and Drug Administration (FDA) approved two new tyrosine kinase inhibitors for the treatment of heavily pretreated advanced/unresectable GIST including avapritinib (a selective inhibitor for PDGFRA exon 18 mutation including D842V mutations) and ripretinib (a broad-spectrum kinase inhibitor of c-Kit and PDGFRA). In this article, we will provide a comprehensive review of GIST including the current standard of care treatment and exploring future paradigm shifts in therapy.

Prognostic and predictive impact of stroma cells defined by PDGFRb expression in early breast cancer: results from the randomized SweBCG91RT trial

Purpose

Predictive biomarkers are needed to aid the individualization of radiotherapy (RT) in breast cancer. Cancer-associated fibroblasts have been implicated in tumor radioresistance and can be identified by platelet-derived growth factor receptor-beta (PDGFRb). This study aims to analyze how PDGFRb expression affects RT benefit in a large randomized RT trial.

Methods

PDGFRb was assessed by immunohistochemistry on tissue microarrays from 989 tumors of the SweBCG91RT trial, which enrolled lymph node-negative, stage I/IIA breast cancer patients randomized to RT after breast-conserving surgery. Outcomes were analyzed at 10 years for ipsilateral breast tumor recurrence (IBTR) and any recurrence and 15 years for breast cancer specific death (BCSD).

Results

PDGFRb expression correlated with estrogen receptor negativity and younger age. An increased risk for any recurrence was noted in univariable analysis for the medium (HR 1.58, CI 95% 1.11–2.23, p = 0.011) or PDGFRb high group (1.49, 1.06–2.10, p = 0.021) compared to the low group. No differences in IBTR or BCSD risk were detected. RT benefit regarding IBTR risk was significant in the PDGFRb low (0.29, 0.12–0.67, p = 0.004) and medium (0.31, 0.16–0.59, p < 0.001) groups but not the PDGFRb high group (0.64, 0.36–1.11, p = 0.110) in multivariable analysis. Likewise, risk reduction for any recurrence was less pronounced in the PDGFRb high group. No significant interaction between RT and PDGFRb-score could be detected.

Conclusion

A higher PDGFRb-score conferred an increased risk of any recurrence, which partly can be explained by its association with estrogen receptor negativity and young age. Reduced RT benefit was noted among patients with high PDGFRb, however without significant interaction.

Natural sourced inhibitors of EGFR, PDGFR, FGFR and VEGFR-mediated signaling pathways as potential anticancer agents

The molecular mechanisms of mitotic cell cycle progression involve very tightly restricted types of machinery which are highly regulated by a fine balance between the positive and negative accelerators (or regulators). These regulators include several checkpoints that have proteins acting as enzymes and their activating partners. These checkpoints incessantly monitor the external as well as internal environments such as growth signals, favorable conditions for growth, cell size, DNA integrity of the cell and hence function to maintain the highly ordered cell cycle progression by sustaining cell homeostasis and promotes error-free DNA replication and cell cycle, division. To progress through the mitotic cell cycle, the cell has to successfully drive past the cell cycle checkpoints. Due to the abnormal behavior of some cell cycle proteins, the cells tend to divide continuously overcoming the tight regulation of cell cycle checkpoints. Such anomalies may lead to unwanted cell division and this deregulation of cell cycle events is considered as one of the main reasons behind tumor development and thus cancer progression. So the understanding of the molecular mechanisms in cancer progression might be insightful for designing several cancer treatment strategies. The deregulation in the checkpoints is caused due to the changes brought in the tyrosine residues of TPKs via PDGFR, EGFR, FGFR, and VEGFR-mediated signalling pathways. Therefore, the inhibitors of PDGFR, EGFR, FGFR, and VEGFR-mediated signalling pathways would be potential anticancer agents. The resistance and toxicity in the existing synthetic anticancer chemotherapeutics may decrease the life span of a patient. For a long, natural products have always played an essential alternative source of therapeutic agents due to having the least or no side effect and toxicity. The present study is an attempt to promote the natural anticancer drug development focusing on the updated structural information of PDGFR, EGFR, FGFR, and VEGFR inhibitors isolated from the plant sources. The data used in this review has been collected from internet resources viz. GOOGLE Web, GOOGLE SCHOLAR, and PubMed Central. The citation of each report was first checked after which the articles were selected as an authentic reference for the present study. Around 200 journal articles were selected of which around 142 were selected finally for presenting the study on the natural sourced inhibitors of EGFR, PDGFR, FGFR, and VEGFR-mediated signaling pathways which would help in the potential cancer treatment.

Vorolanib, an oral VEGFR/PDGFR dual tyrosine kinase inhibitor for treatment of patients with advanced solid tumors: An open-label, phase I dose escalation and dose expansion trial

Objective

This study evaluated the safety and preliminary efficacy of vorolanib, a novel tyrosine kinase inhibitor, for treatment of patients with advanced solid tumors.

Methods

During dose escalation, patients received increasing doses of oral vorolanib (50−250 mg once daily) in cycles of four weeks for up to one year. During dose expansion, patients received recommended doses (100 and 200 mg) in 4-week cycles. The primary endpoint was to determine the safety and maximum tolerated dose and/or the recommended phase II dose (RP2D). The severity and type of adverse drug reactions (ADRs) were assessed using the Common Terminology Criteria for Adverse Events version 4.0. The second endpoint was preliminary efficacy in terms of objective response and progression-free survival (PFS).

Results

No dose-limiting toxicity occurred during dose escalation (50−250 mg). Five (26.3%) patients in the escalation cohort (n=19) and 12 (48.0%) in the expansion cohort (n=25) experienced grade 3 ADRs. The most common ADRs were hair color changes, fatigue, portal hypertension, hypertriglyceridemia, and proteinuria. During dose expansion, the patients treated with 200 mg and 100 mg (once daily) showed an objective response rate of 22.2% and 5.9%, respectively; the disease control rate was 88.9% and 73.3%, respectively; the median PFS was 9.9 [95% confidence interval (95% CI): 7.4−not reached] months and 3.8 (95% CI: 1.9−not reached) months, respectively.

Conclusions

Oral vorolanib at a dose of 200 mg (once daily) exhibited an acceptable safety profile and favorable clinical benefit for patients with advanced solid tumors. The RP2D for vorolanib was determined to be 200 mg as a daily regimen.

The emerging complexity of PDGFRs: activation, internalization and signal attenuation

The platelet-derived growth factor receptor (PDGFR) family of receptor tyrosine kinases allows cells to communicate with the environment to regulate diverse cellular activities. Here, we highlight recent data investigating the structural makeup of individual PDGFRs upon activation, revealing the importance of the whole receptor in the propagation of extracellular ligand binding and dimerization. Furthermore, we review ongoing research demonstrating the significance of receptor internalization and signal attenuation in the regulation of PDGFR activity. Interactions with internalization machinery, signaling from endosomes, receptor degradation and receptor recycling are physiological means by which cells fine-tune PDGFR responses to growth factor stimulation. In this review, we discuss the biophysical, structural, in silico and biochemical data that have provided evidence for these mechanisms. We further highlight the commonalities and differences between PDGFRα and PDGFRβ signaling, revealing critical gaps in knowledge. In total, this review provides a conclusive summary on the state of the PDGFR field and underscores the need for novel techniques to fully elucidate the mechanisms of PDGFR activation, internalization and signal attenuation.

Pathologic HIF1α signaling drives adipose progenitor dysfunction in obesity

Adipose precursor cells (APCs) exhibit regional variation in response to obesity, for unclear reasons. Here, we reveal that HIFα-induced PDGFRβ signaling within murine white adipose tissue (WAT) PDGFRβ⁺ cells drives inhibitory serine 112 (S112) phosphorylation of PPARγ, the master regulator of adipogenesis. Levels of PPARγ S112 phosphorylation in WAT PDGFRβ⁺ cells are depot dependent, with levels of PPARγ phosphorylation in PDGFRβ⁺ cells inversely correlating with their capacity for adipogenesis upon high-fat-diet feeding. HIFα suppression in PDGFRβ⁺ progenitors promotes subcutaneous and intra-abdominal adipogenesis, healthy WAT remodeling, and improved metabolic health in obesity. These metabolic benefits are mimicked by treatment of obese mice with the PDGFR antagonist Imatinib, which promotes adipocyte hyperplasia and glucose tolerance in a progenitor cell PPARγ-dependent manner. Our studies unveil a mechanism underlying depot-specific responses of APCs to high-fat feeding and highlight the potential for APCs to be targeted pharmacologically to improve metabolic health in obesity.

Expression and prognostic significance of PDGF ligands and receptors across soft tissue sarcomas

Background

While the anti-PDGFRA antibody olaratumab failed to confirm an impact on survival in unselected advanced soft tissue sarcoma (STS) patients, the level of expression and the prognosis of platelet-derived growth factor (PDGF) receptors and ligands in STS remain unclear.

Patients and methods

We analyzed PDGF ligands and receptors' expression levels in a series of 255 patients with different histologies of STS [gastrointestinal stromal tumor (GIST), myxoid liposarcoma (MLPS), sarcoma with complex genomics, synovial sarcoma (SyS)] with Agilent single-color micro-arrays. We explored expression levels as prognostic values in univariate and multivariate analysis using R software (version 3.4.2).

Results

Complex patterns of correlation of expression between ligands and receptors were observed for each histotype. PDGFA levels were highest in SyS and lowest in MLPS (P < 4 × 10⁻⁹), PDGFB and C levels were lower in GIST (P < 2 × 10⁻¹⁵ and P < 3 × 10⁻⁹) while PDGFD expression was similar across histological subtypes. PDGF receptor (PDGFR) A expression was lowest in MLPS (P < 0.002), whereas PDGFRB and L expressions were lowest in GIST and SyS (P < 0.0004). Interestingly, high PDGFA expression levels were associated with higher risk of metastasis (P = 0.006), whereas PDGFD levels above average were associated with a reduced risk of metastasis (P = 0.01) in univariate and multivariate analysis.

Conclusions

The expression of PDGF ligands and receptors varies across sarcoma histological subtypes. PDGFA and D expression levels independently and inversely correlate with the risk of metastatic relapse.

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The expression of PDGF ligands and receptors substantially varies across sarcoma histological subtypes.

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PDGFA and D expression levels independently and inversely correlate with the risk of metastatic relapse.

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The differential expression of ligands might be used as biomarker of efficacy for PDGFRα antibodies in STS.

Identification of a Dexamethasone Mediated Radioprotection Mechanism Reveals New Therapeutic Vulnerabilities in Glioblastoma

(1) Background: Despite the indisputable effectiveness of dexamethasone (DEXA) to reduce inflammation in glioblastoma (GBM) patients, its influence on tumour progression and radiotherapy response remains controversial. (2) Methods: We analysed patient data and used expression and cell biological analyses to assess effects of DEXA on GBM cells. We tested the efficacy of tyrosine kinase inhibitors in vitro and in vivo. (3) Results: We confirm in our patient cohort that administration of DEXA correlates with worse overall survival and shorter time to relapse. In GBM cells and glioma stem-like cells (GSCs) DEXA down-regulates genes controlling G2/M and mitotic-spindle checkpoints, and it enables cells to override the spindle assembly checkpoint (SAC). Concurrently, DEXA up-regulates Platelet Derived Growth Factor Receptor (PDGFR) signalling, which stimulates expression of anti-apoptotic regulators BCL2L1 and MCL1, required for survival during extended mitosis. Importantly, the protective potential of DEXA is dependent on intact tyrosine kinase signalling and ponatinib, sunitinib and dasatinib, all effectively overcome the radio-protective and pro-proliferative activity of DEXA. Moreover, we discovered that DEXA-induced signalling creates a therapeutic vulnerability for sunitinib in GSCs and GBM cells in vitro and in vivo. (4) Conclusions: Our results reveal a novel DEXA-induced mechanism in GBM cells and provide a rationale for revisiting the use of tyrosine kinase inhibitors for the treatment of GBM.

Structural studies of full-length receptor tyrosine kinases and their implications for drug design

Receptor tyrosine kinases (RTKs) are important drug targets for cancer and immunological disorders. Crystal structures of individual RTK domains have contributed greatly to the structure-based drug design of clinically used drugs. Low-resolution structures from electron microscopy are now available for the RTKs, EGFR, PDGFR, and Kit. However, there are still no high-resolution structures of full-length RTKs due to the technical challenges of working with these complex, membrane proteins. Here, we review what has been learned from structural studies of these three RTKs regarding their mechanisms of ligand binding, activation, oligomerization, and inhibition. We discuss the implications for drug design. More structural data on full-length RTKs may facilitate the discovery of druggable sites and drugs with improved specificity and effectiveness against resistant mutants.

Nintedanib plus mFOLFOX6 as second-line treatment of metastatic, chemorefractory colorectal cancer: The randomised, placebo-controlled, phase II TRICC-C study (AIO-KRK-0111)

Nintedanib is a triple angiokinase inhibitor of vascular endothelial growth factor receptor 1-3, fibroblast growth factor receptor 1-3 and platelet-derived growth factor receptor-a/-b. Thereby, it targets angiogenic escape mechanisms. The trial TyRosine kinase Inhibitor for the treatment of Chemorefractory Colorectal Cancer (TRICC-C) trial evaluates the addition of nintedanib to mFOLFOX6 (fluorouracil, folinic acid and oxaliplatin) in patients with metastatic colorectal cancer (mCRC). TRICC-C is a randomised controlled, double-blinded, phase II trial in mCRC patients that received a first-line non-oxaliplatin containing chemotherapy. Patients received mFOLFOX6 + nintedanib (F + N) (2 × 200 mg p.o./d, d1-d14) or mFOLFOX6 + placebo (F + P), in a 1:1 ratio. Primary endpoint was median progression free survival (mPFS) and secondary overall response rate (ORR), overall survival (OS) and safety. Fifty-three patients (27 F + N; 26 F + P) were randomised between 12/2012 and 5/2016 (scheduled n = 180). The trial was terminated prematurely due to slow accrual. The trial did not reach its primary endpoint but mPFS, median overall survival (mOS) and disease control rate (DCR) were numerically higher in the F + N arm compared to the F + P arm; however, the difference was not significant (mPFS: F + P: 4.6 months vs F + N: 8.1 months; HR 0.65; 95% CI 0.32-1.30; P = .2156; mOS: F + P: 9.9 months vs F + N: 17.1 months; HR 1.03, 95% CI 0.48-2.23; P = .9387; DCR: F + P: 50% vs F + N: 66,7%; P = .2709). Toxicity was moderate and only different for neutropenia (F + P: 11.5%, F + N: 19.2%) and gastrointestinal disorders (F + P: 65.4%, F + N: 84.6%). Final results show safety and a nonsignificant trend towards improved PFS and DCR for the combination of mFOLFOX6 + nintedanib in the second-line therapy of mCRC.

Tyrosine kinase inhibitor therapy and metabolic remodelling in papillary thyroid cancer

Targeted therapy is increasingly used to manage metastatic papillary thyroid cancer. The focus of the present study was to examine glucose metabolism and tumor responses for thyroid cancer xenografts expressing the glycolytic pathway modulators platelet-derived growth factor receptor (PDGFR) and BRAFV600E. Radiolabelled glucose derivative [18F]FDG was used to analyze the effects of PDGFR blockade with imatinib, BRAF blockade with vemurafenib, as well as combined PDGFR and BRAF blockade in vitro and in vivo with PET. Dynamic PET data was correlated with immunohistochemistry staining and kinetic analysis for facilitative glucose transporter 1 (GLUT1) and hexokinase-II (HK2). Vemurafenib decreased [18F]FDG uptake in BCPAP cells in vitro; however, it was increased by ~70% with imatinib application to BCPAP cells. This metabolic response to tyrosine kinase inhibition required BRAFV600E as it was not seen in cell lines lacking mutated BRAF (TPC1). In xenografts, imatinib therapy in BCPAP thyroid tumour-bearing mice significantly increased [18F]FDG uptake and retention (>30%) in BCPAP tumours with PDGFRβ or both (α+β) isoforms. Kinetic analysis revealed that the increased glucose uptake is a consequence of increased phosphorylation and intracellular trapping of [18F]FDG confirmed by an increase in HK2 protein expression and activity, but not GLUT1 activity. BRAF inhibition alone, or combined PDGFR and BRAF inhibition, reduced (~60%) [18F]FDG uptake in both types of BCPAP (β or α+β) tumours. In terms of tumour growth, combination therapy with imatinib and vemurafenib led to a near abolition of the tumors (~90% reduction), but single therapy for BCPAP with PDGFRα expression was much less effective. In summary, imatinib led to a paradoxical increase of [18F]FDG uptake in xenografts that was reversed through BRAFV600E inhibition. The present data show that metabolic reprogramming in thyroid cancer occurs as a consequence of BRAF-mediated upregulation of HK2 expression that may permit tumour growth with isolated blockade of upstream tyrosine kinase receptors.

Sunitinib induces primary ectopic endometrial cell apoptosis through up-regulation of STAT1 in vitro

Background

Endometriosis (EMS) is a prevalent gynecological condition characterized by the growth of endometrial tissue outside the uterine cavity. This study aimed to clarify the targeted therapeutic effect of sunitinib in an endometriosis in vitro experiment.

Methods

Primary culture of ectopic endometrial cells and normal endometrial cells. Six tumor targeting drugs were selected to screen. MTT was used to determine the IC50, flow cytometry, and DAPI staining of the targeted drugs, in order to determine the apoptosis. The differential proteins after seeding were analyzed by protein spectrum, the correlation between the specific protein and cell apoptosis was determined by small molecule interference, and the expression of each related protein was detected by Western blot. Immunohistochemistry and ELISA were used to detect the expression of p‐PDGFR and p‐STAT1 in clinical samples, and the correlation between p‐STAT1 expression and ectopic focal size was analyzed by SPSS 19.

Results

Through the drug screening, it was found that sunitinib has a significant inhibitory effect on ectopic endometrial cells. It was determined that the IC50 of sunitinib on ectopic stromal endometrial cells was 3.32 μM, while the IC50 on normal endometrium was 7.9 μM. Meanwhile, the flow cytometry and DAPI nuclear dye that took out sunitinib had an inhibition effect on the ectopic endometrium at a concentration of 4 μM. Protein spectrum analysis was conducted on ectopic intimal cells after sunitinib treatment, and it was found that STAT1 is specifically expressed in ectopic endometrial cells. In vitro, and through fludarabine interference, it was revealed that sunitinib specifically inhibited the phosphorylation site Tyr751 of PDGFR, while the expression of STAT1, p‐STAT1, and caspase‐3 was significantly upregulated, and the expression of STAT1 and p‐STAT1 was positively correlated with the expression of caspase‐3. Finally, the expression of p‐PDGFR and p‐STAT1 in ectopic foal tissues was both higher than that in normal endometrium, and p‐STAT1 expression was positively with ectopic focal size.

Conclusion

The in vitro experiments revealed that sunitinib could upregulate the expression of STAT1 by inhibiting the phosphorylation site Tyr751 of PDGFR, thereby specifically inducing the apoptosis of the primary heterotopic mesenchymal endometrium.

NRF2 activates growth factor genes and downstream AKT signaling to induce mouse and human hepatomegaly

BACKGROUND & AIMS

Hepatomegaly can be triggered by insulin and insulin-unrelated etiologies. Insulin acts via AKT, but how other challenges cause hepatomegaly is unknown.

METHODS

Since many hepatomegaly-inducing toxicants and stressors activate NRF2, we examined the effect of NRF2 activation on liver size and metabolism using a conditional allele encoding a constitutively active NRF2 variant to generate Nrf2^Act-hep mice in which NRF2 is selectively activated in hepatocytes. We also used adenoviruses encoding variants of the autophagy adaptor p62/SQSTM1, which activates liver NRF2, as well as liver-specific ATG7-deficient mice (Atg7^Δhep) and liver specimens from patients with hepatic sinusoidal obstruction syndrome (HSOS) and autoimmune hepatitis (AIH). RNA sequencing and cell signaling analyses were used to determine cellular consequences of NRF2 activation and diverse histological analyses were used to study effects of the different manipulations on liver and systemic pathophysiology.

RESULTS

Hepatocyte-specific NRF2 activation, due to p62 accumulation or inhibition of KEAP1 binding, led to hepatomegaly associated with enhanced glycogenosis, steatosis and G2/M cell cycle arrest, fostering hyperplasia without cell division. Surprisingly, all manipulations that led to NRF2 activation also activated AKT, whose inhibition blocked NRF2-induced hepatomegaly and glycogenosis, but not NRF2-dependent antioxidant gene induction. AKT activation was linked to NRF2-mediated transcriptional induction of PDGF and EGF receptor ligands that signaled through their cognate receptors in an autocrine manner. Insulin and insulin-like growth factors were not involved. The NRF2-AKT signaling axis was also activated in human HSOS- and AIH-related hepatomegaly.

CONCLUSIONS

NRF2, a transcription factor readily activated by xenobiotics, oxidative stress and autophagy disruptors, may be a common mediator of hepatomegaly; its effects on hepatic metabolism can be reversed by AKT/tyrosine kinase inhibitors.

LAY SUMMARY

Hepatomegaly can be triggered by numerous etiological factors, including infections, liver cancer, metabolic disturbances, toxicant exposure, as well as alcohol abuse or drug-induced hepatitis. This study identified the oxidative stress response transcription factor NRF2 as a common mediator of hepatomegaly. NRF2 activation results in elevated expression of several growth factors. These growth factors are made by hepatocytes and activate their receptors in an autocrine fashion to stimulate the accumulation of glycogen and lipids that lead to hepatocyte and liver enlargement. The protein kinase AKT plays a key role in this process and its inhibition leads to reversal of hepatomegaly.

Imatinib Sets Pericyte Mosaic in the Retina

The nervous system demands an adequate oxygen and metabolite exchange, making pericytes (PCs), the only vasoactive cells on the capillaries, essential to neural function. Loss of PCs is a hallmark of multiple diseases, including diabetes, Alzheimer's, amyotrophic lateral sclerosis (ALS) and Parkinson's. Platelet-derived growth factor receptors (PDGFRs) have been shown to be critical to PC function and survival. However, how PDGFR-mediated PC activity affects vascular homeostasis is not fully understood. Here, we tested the hypothesis that imatinib, a chemotherapeutic agent and a potent PDGFR inhibitor, alters PC distribution and thus induces vascular atrophy. We performed a morphometric analysis of the vascular elements in sham control and imatinib-treated NG2-DsRed mice. Vascular morphology and the integrity of the blood-retina barrier (BRB) were evaluated using blood albumin labeling. We found that imatinib decreased the number of PCs and blood vessel (BV) coverage in all retinal vascular layers; this was accompanied by a shrinkage of BV diameters. Surprisingly, the total length of capillaries was not altered, suggesting a preferential effect of imatinib on PCs. Furthermore, blood-retina barrier disruption was not evident. In conclusion, our data suggest that imatinib could help in treating neurovascular diseases and serve as a model for PC loss, without BRB disruption.

Effect of Small-molecule Tyrosine Kinase Inhibitors on PDGF-AA/BB and PDGFRα/β Expression in SCC According to HPV16 Status

BACKGROUND

Despite extensive research into new treatment options, the prognosis for head and neck squamous cell carcinoma remains poor. Platelet-derived growth factor (PDGF) is up-regulated in HNSCC and expression levels decrease after surgery, suggesting its role in tumour development. The influence of HPV on the PDGF/PDGF receptor (PDGFR) pathway remains unclear. In this study, we investigated the effect of small-molecule tyrosine kinase inhibitors (TKIs) on the expression of PDGF and its receptor in vitro using squamous cancer cell lines with different human papillomavirus 16 (HPV16) status.

MATERIALS AND METHODS

Two human HPV16-negative cell lines (UMSCC-11A/-14C) and one HPV16-positive cell line (CERV196) were used. Tumour cells were incubated with 20 μmol/l of TKIs nilotinib, dasatinib, afatinib, gefitinib and erlotinib for 24-96 h. Cell proliferation was assessed via proliferation assay and protein concentrations of PDGF-AA and BB and PDGFRα and -β via sandwich enzyme-linked immunosorbent assay. For statistical analysis, the results were compared with those from an untreated negative control.

RESULTS

PDGF-AA/BB and PDGFRα/-β were detected in all three tested cell lines. The addition of TKI led to a significant (p<0.05) decrease of PDGF/PDGFR at different time points and cell lines. The strongest effects were seen for the expression of PDGF-AA, which was consistently inhibited by most drugs. The effects of the TKI were independent of the HPV status.

CONCLUSION

Proteins of this pathway can effectively be inhibited by small molecule TKIs. PDGF-AA seems to be a promising target for future studies with selective TKIs.

Dysregulated mesenchymal PDGFR-β drives kidney fibrosis

Kidney fibrosis is characterized by expansion and activation of platelet-derived growth factor receptor-β (PDGFR-β)-positive mesenchymal cells. To study the consequences of PDGFR-β activation, we developed a model of primary renal fibrosis using transgenic mice with PDGFR-β activation specifically in renal mesenchymal cells, driving their pathological proliferation and phenotypic switch toward myofibroblasts. This resulted in progressive mesangioproliferative glomerulonephritis, mesangial sclerosis, and interstitial fibrosis with progressive anemia due to loss of erythropoietin production by fibroblasts. Fibrosis induced secondary tubular epithelial injury at later stages, coinciding with microinflammation, and aggravated the progression of hypertensive and obstructive nephropathy. Inhibition of PDGFR activation reversed fibrosis more effectively in the tubulointerstitium compared to glomeruli. Gene expression signatures in mice with PDGFR-β activation resembled those found in patients. In conclusion, PDGFR-β activation alone is sufficient to induce progressive renal fibrosis and failure, mimicking key aspects of chronic kidney disease in humans. Our data provide direct proof that fibrosis per se can drive chronic organ damage and establish a model of primary fibrosis allowing specific studies targeting fibrosis progression and regression.

Receptor Tyrosine Kinases: Principles and Functions in Glioma Invasion

Protein tyrosine kinases are enzymes that are capable of adding a phosphate group to specific tyrosines on target proteins. A receptor tyrosine kinase (RTK) is a tyrosine kinase located at the cellular membrane and is activated by binding of a ligand via its extracellular domain. Protein phosphorylation by kinases is an important mechanism for communicating signals within a cell and regulating cellular activity; furthermore, this mechanism functions as an "on" or "off" switch in many cellular functions. Ninety unique tyrosine kinase genes, including 58 RTKs, were identified in the human genome; the products of these genes regulate cellular proliferation, survival, differentiation, function, and motility. Tyrosine kinases play a critical role in the development and progression of many types of cancer, in addition to their roles as key regulators of normal cellular processes. Recent studies have revealed that RTKs such as epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), c-Met, Tie, Axl, discoidin domain receptor 1 (DDR1), and erythropoietin-producing human hepatocellular carcinoma (Eph) play a major role in glioma invasion. Herein, we summarize recent advances in understanding the role of RTKs in glioma pathobiology, especially the invasive phenotype, and present the perspective that RTKs are a potential target of glioma therapy.

Rational Drug Design Approach of Receptor Tyrosine Kinase Type III Inhibitors

Rational drug design is accomplished through the complementary use of structural biology and computational biology of biological macromolecules involved in disease pathology. Most of the known theoretical approaches for drug design are based on knowledge of the biological targets to which the drug binds. This approach can be used to design drug molecules that restore the balance of the signaling pathway by inhibiting or stimulating biological targets by molecular modeling procedures as well as by molecular dynamics simulations. Type III receptor tyrosine kinase affects most of the fundamental cellular processes including cell cycle, cell migration, cell metabolism, and survival, as well as cell proliferation and differentiation. Many inhibitors of successful rational drug design show that some computational techniques can be combined to achieve synergistic effects.

Phase I study of TAS-115, a novel oral multi-kinase inhibitor, in patients with advanced solid tumors

TAS-115 is a novel MET, VEGFR, FMS and PDGFR inhibitor, developed to improve the continuity of drug administration with a relatively short half-life. We assessed its tolerability, safety, pharmacokinetics, efficacy, and pharmacodynamics in patients with solid tumors. This open-label, dose-escalation phase I study of TAS-115 consisted of three parts: part 1 (TAS-115 was administered orally once daily [SID]); part 2 and an expansion part (SID in a 5 days on/2 days off [5-on/2-off] schedule for 21 days per cycle). In part 1 (200-800 mg SID administered to 21 patients), systemic exposure after single administration increased almost dose-proportionally. Three dose-limiting toxicities (DLTs) were observed in three patients: grade 3 rash (650 mg), thrombocytopenia with bleeding, and rash (800 mg). The maximum tolerated dose (MTD) was determined as 650 mg SID. In part 2, the 5-on/2-off schedule was evaluated at the MTD to improve treatment exposure. No DLTs were observed and no patients required treatment interruption in cycle 1. During part 2 and the expansion part (N = 61), grade ≥3 treatment-related adverse events were reported in 47 patients, with neutropenia (24.6%), hypophosphatemia (21.3%), anemia, and thrombocytopenia (14.8% each), and leukocytopenia (11.5%) occurring in ≥10% of patients. The best overall response was stable disease in 31 of 82 patients (37.8%). An apparent reduction in fluorodesoxyglucose-uptake and bone scan index was observed in some patients. TAS-115 was generally well tolerated, with manageable toxicities and recommended phase II dose was estimated as 650 mg SID, 5-on/2-off. Furthermore, promising antitumor activity was observed.

An update on current and future treatment options for chondrosarcoma

Introduction: Human chondrosarcomas (CS; a malignant cartilage-forming bone tumor) respond poorly to chemotherapy and radiation treatment, resulting in high morbidity and mortality rates. Expanded treatment options are urgently needed. Areas covered: This article updates our 2014 review, in which we evaluated the CS treatments available at that time and potential treatment options under investigation. Since then, advances in research findings, particularly from Chinese herbal medicines, may be bringing us closer to more effective therapies for CS. In particular, promising findings have been reported from research targeting platelet-derived growth factor receptor. Expert opinion: Few treatment options exist for CS; chemotherapy is not even an option for unresectable disease, in which 5-year survival rates are just 2%. New information about the multitude of genes and signaling pathways that encourage CS growth, invasion and metastasis are clarifying how certain signaling pathways and plant-derived active compounds, especially molecularly-targeted therapies that inhibit the PDGF receptor, interfering with these biological processes. This review summarizes discoveries from the last 5 years and discusses how these findings are fueling ongoing work into effectively dealing with the disease process and improving the treatment of CS.