MG Xenograft Research Articles

Synthesis and Characterization of a Novel PET Tracer for Noninvasive Evaluation of FGL1 Status in Tumors.

Fibrinogen-like protein 1 (FGL1) is a potential novel immune checkpoint target for malignant tumor diagnosis and therapy. Accurate detection of FGL1 levels in tumors via noninvasive PET imaging might be beneficial for managing the disease. To achieve this, multiple FGL1-targeting peptides (FGLP) were designed, and a promising candidate, 68Ga-NOTA-FGLP2, was identified through a high-throughput screening approach using microPET imaging of 68Ga-labeled peptides. Subsequent in vitro cell experiments showed that uptake values of 68Ga-NOTA-FGLP2 in FGL1 positive Huh7 tumor cells were significantly higher than those in FGL1 negative U87 MG tumor cells. Further microPET imaging showed that the Huh7 xenografts were clearly visualized with a favorable contrast. ROI analysis showed that the uptake values of the tracer in Huh7 xenografts were 2.63 ± 0.07% ID/g at 30 min p.i.. After treatment with an excess of unlabeled FGLP2, the tumor uptake significantly decreased to 0.54 ± 0.05% ID/g at 30 min p.i.. Moreover, the uptake in U87 MG xenografts was 0.44 ± 0.06% ID/g at the same time point. The tracer was excreted mainly through the renal system. 18F-FDG PET imaging was also performed in mice bearing Huh7 and U87 MG xenografts, respectively. However, there was no significant difference in the uptake between the tumors with different FGL1 expressions. Preclinical data indicated that 68Ga-NOTA-FGLP2 might be a suitable radiotracer for in vivo noninvasive visualization of tumors with abundant expression of FGL1. Further investigation of 68Ga-NOTA-FGLP2 for tumor diagnosis and therapy is undergoing.

The Recombinant Oncolytic Virus VV-GMCSF-Lact and Chemotherapy Drugs against Human Glioma.

Virotherapy is one of the perspective technologies in the treatment of malignant neoplasms. Previously, we have developed oncolytic vaccinia virus VV-GMCSF-Lact and its high cytotoxic activity and antitumor efficacy against glioma was shown. In this work, using immortalized and patient-derived cells with different sensitivity to VV-GMCSF-Lact, we evaluated the cytotoxic effect of chemotherapy agents. Additionally, we studied the combination of VV-GMCSF-Lact with temozolomide which is the most preferred drug for glioma treatment. Experimental results indicate that first adding temozolomide and then the virus to the cells is inherently more efficient than dosing it in the reverse order. Testing these regimens in the U87 MG xenograft glioblastoma model confirmed this effect, as assessed by tumor growth inhibition index and histological analysis. Moreover, VV-GMCSF-Lact as monotherapy is more effective against U87 MG glioblastoma xenografts comparing temozolomide.

Molecular Imaging of Ultrasound-Mediated Blood-Brain Barrier Disruption in a Mouse Orthotopic Glioblastoma Model.

Glioblastoma (GBM) is an aggressive and malignant primary brain tumor. The blood-brain barrier (BBB) limits the therapeutic options available to tackle this incurable tumor. Transient disruption of the BBB by focused ultrasound (FUS) is a promising and safe approach to increase the brain and tumor concentration of drugs administered systemically. Non-invasive, sensitive, and reliable imaging approaches are required to better understand the impact of FUS on the BBB and brain microenvironment. In this study, nuclear imaging (SPECT/CT and PET/CT) was used to quantify neuroinflammation 48 h post-FUS and estimate the influence of FUS on BBB opening and tumor growth in vivo. BBB disruptions were performed on healthy and GBM-bearing mice (U-87 MG xenograft orthotopic model). The BBB recovery kinetics were followed and quantified by [99mTc]Tc-DTPA SPECT/CT imaging at 0.5 h, 3 h and 24 h post-FUS. The absence of neuroinflammation was confirmed by [18F]FDG PET/CT imaging 48 h post-FUS. The presence of the tumor and its growth were evaluated by [68Ga]Ga-RGD2 PET/CT imaging and post-mortem histological analysis, showing that tumor growth was not influenced by FUS. In conclusion, molecular imaging can be used to evaluate the time frame for systemic treatment combined with transient BBB opening and to test its efficacy over time.

The Anti-Tumor Effect of Boron Neutron Capture Therapy in Glioblastoma Subcutaneous Xenograft Model Using the Proton Linear Accelerator-Based BNCT System in Korea.

Boron neutron capture therapy (BNCT) is a radiation therapy that selectively kills cancer cells and is being actively researched and developed around the world. In Korea, development of the proton linear accelerator-based BNCT system has completed development, and its anti-cancer effect in the U-87 MG subcutaneous xenograft model has been evaluated. To evaluate the efficacy of BNCT, we measured 10B-enriched boronophenylalanine (BPA) uptake in U-87 MG, FaDu, and SAS cells and evaluated cell viability by clonogenic assays. In addition, the boron concentration in the tumor, blood, and skin on the U-87 MG xenograft model was measured, and the tumor volume was measured for 4 weeks after BNCT. In vitro, the intracellular boron concentration was highest in the order of SAS, FaDu, and U-87 MG, and cell survival fractions decreased depending on the BPA treatment concentration and neutron irradiation dose. In vivo, the tumor volume was significantly decreased in the BNCT group compared to the control group. This study confirmed the anti-cancer effect of BNCT in the U-87 MG subcutaneous xenograft model. It is expected that the proton linear accelerator-based BNCT system developed in Korea will be a new option for radiation therapy for cancer treatment.

PET in vivo generators 134Ce and 140Nd on an internalizing monoclonal antibody probe

The in vivo-generator radionuclides 140Nd (t1/2 = 3.4 d) and 134Ce (t1/2 = 3.2 d) were used to trace a urokinase-type plasminogen activator (uPA)-targeting mouse monoclonal antibody, ATN-291, in U87 MG xenograft tumor-bearing mice. ATN-291 is known to internalize on the uPA/uPA-receptor pair, making it an appropriate targeting vector for investigating the fate of in vivo generator daughters on internalizing probes. Ante-mortem and post-mortem PET imaging at 120 h post-injection gave no indication of redistribution of the positron emitting daughter nuclides 134La and 140Pr from tumor tissue (p > 0.5). The lack of redistribution indicates that the parent radionuclides 134Ce and 140Nd could be considered as long-lived PET-diagnostic matches to therapeutic radionuclides like 177Lu, 161Tb and 225Ac when internalizing bioconjugates are employed.

Biological evaluation of complexes of cyclopentadienyl M(CO)3+ (M = Re, 99mTc) with high blood-brain barrier penetration potential as brain cancer agents.

To address the major medical need for effective chemotherapeutics/diagnostics for brain cancer, in this work three cyclopentadienyl M(CO)3+ (M = Re, 99mTc) complexes, which cross the blood-brain barrier (BBB) in high % and are designed to mimic the anticancer agent 2-phenylbenzothiazole, are in vitro and in vivo evaluated for anticancer action. The study includes cytotoxicity and uptake studies in cancer and healthy neuronal cell lines, mechanistic investigation of potential anticancer pathways, and biodistribution studies in mice bearing glioblastoma xenografts. The stable Re complexes exhibit selective uptake and significant antiproliferative effect, particularly against U-251 MG glioblastoma cells, with no significant toxicity in healthy neurons, demonstrating the suitability of this type of complexes to serve as selective therapeutic/imaging agents for brain cancer. Furthermore, they result in the generation of elevated Reactive Oxygen Species (ROS) levels, and lead to significant G2/M arrest followed by apoptosis. Biodistribution studies in U-251 MG xenograft bearing mice with the radioactive 99mTc complex that exhibits the highest BBB penetration, show retention at the tumor-site offering a diagnostic prospect and, in addition, indicating the capability of the Re analogue to accumulate at the tumor site for therapeutic action. Overall, the complexes demonstrate significant anticancer properties that, combined with their high BBB penetration potential, render them strong candidates for further evaluation as brain cancer agents.

Synthesis and Biological Evaluation of 99mTc-Labeled Phenylpiperazine Derivatives as Selective Serotonin-7 Receptor Ligands for Brain Tumor Imaging.

With a poor prognosis, glioblastoma multiforme is the most aggressive tumor of the central nervous system in humans. The aim of this study was to develop novel tracers for the tumor targeting and imaging of overexpressed serotonin-7 receptors (5-HT7Rs) in U-87 MG glioma xenografted nude mice. Two phenylpiperazine derivatives named as PHH and MPHH were designed, and the corresponding radiotracers 99mTc-PHH and 99mTc-MPHH were synthesized in high radiochemical purity (>95%). 99mTc-MPHH showed a higher affinity to 5-HT7Rs on U-87 MG cells compared to 99mTc-PHH. In biodistribution studies, the radiocomplexes showed good brain uptake at 15 min combined with good radioactivity retention in the brain for 240 min. Regional rabbit brain studies indicated a higher radioactivity concentration in the hippocampus and diencephalon than in the cerebellum. Compared to 99mTc-MPHH, the 99mTc-PHH exhibited a significantly increased tumor uptake at 15 and 60 min, but the rapid blood clearance of 99mTc-MPHH led to enhanced tumor-to-muscle ratios at 240 min. A significant reduction in tumor uptake 60 min after an injection of pimozide (5-HT7 receptor antagonist) confirms the tumor uptake was receptor-mediated specifically. The tumor-to-contralateral muscle tissue ratio of 99mTc-PHH and 99mTc-MPHH in nude mice with U-87 MG xenograft was measured (5.25 and 4.65) at 60 min as well as (6.25 and 6.76) at 240 min, respectively.

Molecular Imaging and Preclinical Studies of Radiolabeled Long-Term RGD Peptides in U-87 MG Tumor-Bearing Mice.

The Arg–Gly–Asp (RGD) peptide shows a high affinity for αvβ3 integrin, which is overexpressed in new tumor blood vessels and many types of tumor cells. The radiolabeled RGD peptide has been studied for cancer imaging and radionuclide therapy. We have developed a long-term tumor-targeting peptide DOTA-EB-cRGDfK, which combines a DOTA chelator, a truncated Evans blue dye (EB), a modified linker, and cRGDfK peptide. The aim of this study was to evaluate the potential of indium-111(111In) radiolabeled DOTA-EB-cRGDfK in αvβ3 integrin-expressing tumors. The human glioblastoma cell line U-87 MG was used to determine the in vitro binding affinity of the radiolabeled peptide. The in vivo distribution of radiolabeled peptides in U-87 MG xenografts was investigated by biodistribution, nanoSPECT/CT, pharmacokinetic and excretion studies. The in vitro competition assay showed that 111In-DOTA-EB-cRGDfK had a significant binding affinity to U-87 MG cancer cells (IC50 = 71.7 nM). NanoSPECT/CT imaging showed 111In-DOTA-EB-cRGDfK has higher tumor uptake than control peptides (111In-DOTA-cRGDfK and 111In-DOTA-EB), and there is still a clear signal until 72 h after injection. The biodistribution results showed significant tumor accumulation (27.1 ± 2.7% ID/g) and the tumor to non-tumor ratio was 22.85 at 24 h after injection. In addition, the pharmacokinetics results indicated that the 111In-DOTA-EB-cRGDfK peptide has a long-term half-life (T1/2λz = 77.3 h) and that the calculated absorbed dose was safe for humans. We demonstrated that radiolabeled DOTA-EB-cRGDfK may be a promising agent for glioblastoma tumor imaging and has the potential as a theranostic radiopharmaceutical.

The Effectiveness of Dichloroacetate on Human Glioblastoma Xenograft Growth Depends on Na+ and Mg2+ Cations.

The study’s aim was to investigate the effectiveness of sodium dichloroacetate (NaDCA) or magnesium dichloroacetate (MgDCA) on adult U87 MG and pediatric PBT24 cell lines glioblastoma (GB) xenografts in a chicken chorioallantoic membrane (CAM) model. The study groups were: treated with 10 mM, 5 mM of NaDCA, and 5 mM, 2.5 mM of MgDCA, and controls. The U87 MG and PBT24 xenografts growth, frequency of tumor invasion into CAM, CAM thickening, and the number of blood vessels in CAM differed depending on the dichloroacetate salt treatment. NaDCA impact on U87 MG and PBT24 tumor on proliferating cell nunclear antigen (PCNA) and enhancer of zeste homolog 2 (EZH2) expression in the tumor was different, depending on the NaDCA dose. The 5 mM MgDCA impact was more potent and had similar effects on U87 MG and PBT24 tumors, and its impact was also reflected in changes in PCNA and EZH2 expression in tumor cells. The U87 MG and PBT24 tumor response variations to treatment with different NaDCA concentration on tumor growth or a contrast between NaDCA and MgDCA effectiveness may reflect some differences in U87 MG and PBT24 cell biology.

Evaluation of 99mTc-CN5DG as a broad-spectrum SPECT probe for tumor imaging

Previously, we reported a [99mTc(ǀ)]+ labeled d-glucoamine derivative (99mTc-CN5DG) and evaluated it as a tumor imaging agent in mice bearing A549 tumor xenografts. In this paper, 99mTc-CN5DG was further studied in U87 MG (human glioma cells), HCT-116 (human colon cancer cells), PANC-1 (human pancreatic cancer cells) and TE-1 (human esophageal cancer cells) tumor xenografts models to verify its potential application for imaging of different kinds of tumors. The biodistribution data showed that 99mTc-CN5DG had a similar biodistribution pattern in four tumor models at 2 h post-injection with high accumulation in tumors and kidneys. The tumor/muscle ratios (from 4.08 ± 0.42 to 9.63 ± 3.53) and tumor/blood ratios (from 17.18 ± 7.40 to 53.17 ± 16.16) of 99mTc-CN5DG in four tumor models were high. All four kinds of tumors could be clearly seen on their corresponding SPECT/CT images. Pharmacokinetic study in healthy CD-1 mice demonstrated that 99mTc-CN5DG cleared fast from blood (2 min, 12.97 ± 0.88%ID/g; 60 min, 0.33 ± 0.06%ID/g) and the blood distribution, elimination half-life was 5.81 min and 21.16 min, respectively. No abnormality was observed through the abnormal toxicity study. All of the above results demonstrated that 99mTc-CN5DG could be a broad-spectrum SPECT probe for tumor imaging and its further clinical application is warranted.

Structure-activity relationship study of novel quinazoline-based 1,6-naphthyridinones as MET inhibitors with potent antitumor efficacy.

As a privileged scaffold, the quinazoline ring is widely used in the development of EGFR inhibitors, while few quinazoline-based MET inhibitors are reported. In our ongoing efforts to develop new MET-targeted anticancer drug candidates, a series of quinazoline-based 1,6-naphthyridinone derivatives were designed, synthesized, and evaluated for their biological activities. The preliminary SARs studies indicate that the quinazoline scaffold was also acceptable for the block A of class II MET inhibitors. The further pharmacokinetic studies led to the identification of the most promising compound 22a with favorable invitro potency (MET, IC50=9.0nM), human microsomal metabolic stability (t1/2=621.2min) and oral bioavailability (F=42%). Moreover, 22a displayed good invivo antitumor efficacy (IR of 81% in 75mg/kg) in MET-positive human glioblastoma U-87 MG xenograft model. These positive results indicated that 22a is a potential new MET-targeted antitumor drug lead, which is worthy of further development.

Penetrating the Blood-Brain Barrier by Self-Assembled 3D DNA Nanocages as Drug Delivery Vehicles for Brain Cancer Therapy.

The development of biocompatible drug delivery vehicles for cancer therapy in the brain remains a big challenge. In this study, we designed self-assembled DNA nanocages functionalized with or without blood-brain barrier (BBB)-targeting ligands, d and we investigated their penetration across the BBB. Our DNA nanocages were not cytotoxic and they were substantially taken up in brain capillary endothelial cells and Uppsala 87 malignant glioma (U-87 MG) cells. We found that ligand modification is not essential for this DNA system as the ligand-free DNA nanocages (LF-NCs) could still cross the BBB by endocytosis inin vitro and in vivo models. Our spherical DNA nanocages were more permeable across the BBB compared with tubular DNA nanotubes. Remarkably, in vivo studies revealed that DNA nanocages could carry anticancer drugs across the BBB and inhibit the tumor growth in a U-87 MG xenograft mouse model. This is the first example showing the potential of DNA nanocages as innovative delivery vehicles to the brain for cancer therapy. Unlike other delivery systems, our work suggest that a DNA nanocage-based platform provides a safe and cost-effective tool for targeted delivery to the brain and therapy for brain tumors.

ANGI-07. NOVEL FUSION GENE PTPRZ1-MET PROMOTES GLIOMAS ANGIOGENESIS BY UP-REGULATING EXOCRINE PROTEIN IGF2BP3

Abstract We previously reported a novel fusion gene PTPRZ1-MET in 15% of secondary GBM (sGBM). Subsequent studies showed that ZM fusion indicates a significantly worse prognosis and promotes glioma progression by increasing MET activity. We have demonstrated hyper-activation of MAPK and STAT3 signaling and elevated angiogenesis activities in patients and subcutaneous tumors with ZM fusion. However, the angiogenesis mechanism regulated by ZM is still unclear. In this study, 66 up-regulated and 66 down-regulated genes were identified on 8 sGBMs with ZM fusion comparing gene expression with 135 negative sGBMs (fold-change >2.5 & p.value < 0.05). ZM-harboring U87 MG xenograft models were conducted and RNA sequencing was performed in 3 subcutaneous tumors with ZM-harboring U87 MG and 3 negative control. 384 up-regulated and 698 down-regulated genes were identified on 3 ZM-harboring samples comparing gene expression with 3 negative control samples (fold-change >2.5 & p.value < 0.05. Three subcutaneous tumors with ZM-harboring U87 MG were treated by a MET kinase inhibitor, PLB-1001. Finally, the expression of 13 up-regulated gene decreased and 10 down-regulated genes increased after treatment by PLB-1001. We overlapped the candidate genes between patient samples and subcutaneous tumors and 5 up-regulated and 4 down-regulated genes was appeared and most associated with ZM fusion. Prognostic analysis of 9 candidate genes on sGBM revealed that a higher expression of IGF2BP3 indicates a worse prognosis. In further study, we found that IGF2BP3 can be secreted out of the gliomas stem cells (GSCs) and promote proliferation of vascular endothelial cells and the expression of CD31. IGF2BP3 siRNA can block this pathway and inhibit the angiogenesis. Conclusion, our study demonstrated a new pathway promoting angiogenesis in gliomas. But the regulating mechanism between ZM fusion gene and IGF2BP3 deserves to do further research.

2,7-naphthyridinone-based MET kinase inhibitors: A promising novel scaffold for antitumor drug development

As part of our effort to develop new molecular targeted antitumor drug, a novel 2,7-naphthyridone-based MET kinase inhibitor, 8-((4-((2-amino-3-chloropyridin-4-yl)oxy)- 3-fluorophenyl)amino)-2-(4-fluorophenyl)-2,7-naphthyridin-1(2H)-one (13f), was identified. Knowledge of the binding mode of BMS-777607 in MET led to the design of new inhibitors that utilize novel 2,7-naphthyridone scaffold to conformationally restrain the key pharmacophoric groups (block C). Detailed SAR studies resulted in the discovery of a new MET inhibitor 13f, displaying favorable in vitro potency and oral bioavailability. More importantly, 13f exhibited excellent in vivo efficacy (tumor growth inhibition/TGI of 114% and 95% in 50 mg/kg, respectively) both in the U-87 MG and HT-29 xenograft models. The favorable drug-likeness of 13f indicated that 2,7-naphthyridinone may be used a promising novel scaffold for antitumor drug development. The preclinical studies of 13f are under way.

Anticancer effects of FL34 through the inhibition of GLI1 in glioblastoma.

The hedgehog (HH) signaling pathway is abnormally activated in glioblastoma (GBM); thus, its downstream effector GLI1 may be a suitable target for the treatment of GBM. The aim of the present study was to evaluate the antitumor activities of a novel compound, FL34, in GBM through the inhibition of GLI1. The effect of FL34 on suppressing the proliferation, angiogenesis, and invasion of GBM cells was investigated in vitro using proliferation, invasion, tube formation, flow cytometry, GLI1 dual luciferase, reverse transcription-quantitative polymerase chain reaction, and western blot assays. A subcutaneously transplanted and orthotopic U-87 MG GBM cell xenograft model was used to study the effect of FL34 on tumor growth in vivo. The results of the present study demonstrated that FL34 markedly inhibited the proliferation, invasion, and angiogenesis of GBM, in addition to decreasing the transcriptional activity and expression of GLI1, resulting in the downregulation of GLI1 target genes, including B-cell lymphoma-2, vascular endothelial growth factor, and matrix metalloproteinases. Furthermore, FL34 inhibited the activation of GLI1 without influencing upstream canonical HH/Smoothened signaling or through crosstalk with other oncogenic pathways, including Ras/ERK and AKT signaling. At a dose of 30.0 mg/kg, FL34 suppressed tumor growth by 78.74% in tumor weight in subcutaneously transplanted U-87 MG xenograft models and by 64.24% in volume in orthotopic U-87 MG GBM xenograft models. These data suggested that FL34 exerted antitumor activity mediated by the inhibition of GLI1 and that FL34 may be a potential antitumor candidate compound that could be used to develop new antitumor drugs for the treatment of GBM.

Honokiol Eliminates Glioma/Glioblastoma Stem Cell-Like Cells Via JAK-STAT3 Signaling and Inhibits Tumor Progression by Targeting Epidermal Growth Factor Receptor.

Malignant gliomas are the most aggressive forms of brain tumors; whose metastasis and recurrence contribute to high rates of morbidity and mortality. Glioma stem cell-like cells are a subpopulation of tumor-initiating cells responsible for glioma tumorigenesis, metastasis, recurrence and resistance to therapy. Epidermal growth factor receptor (EGFR) has been reported to be dysregulated in most cancers, including gliomas and its functions are closely linked to initiating tumor metastasis and a very poor prognosis. In search for compounds that may reduce the tumorigenic potential of gliomas/glioblastomas honokiol attracted our attention. Honokiol, purified from the bark of traditional Chinese herbal medicine Magnolia species, is beneficial in vitro and in animal models via a variety of pharmacological effects, including anti-inflammatory, anti-angiogenetic, anti-arrhythmic and antioxidant activities, as well as anti-proliferative and proapoptotic effects in a wide range of human cancer cells. However, its effects on glioma cells are unknown. Here, we used different concentrations of honokiol in treating U251 and U-87 MG human glioma/glioblastoma cells in cell culture. Results showed that honokiol inhibited glioma cell viability and colony formation and promoted apoptosis. It also inhibited glioma cell migration/proliferation and invasion. In addition, honokiol promoted apoptosis and reduced Bcl-2 expression, accompanied by increase in Bax expression. Honokiol reduced expression of EGFR, CD133 and Nestin. Moreover, honokiol inhibited the activation of both AKT and ERK signaling pathways, increased active caspase-3 level and reduced phosphorylation of STAT3. U-87 MG xenografts in nude mice and in immunotolerant zebrafish yolk sac showed that honokiol inhibits tumor growth and metastasis. Altogether, results indicate that honokiol reduces tumorigenic potentials, suggesting hopes for honokiol to be useful in the clinical management of glioma/glioblastoma.

TLR-4/Wnt modulation as new therapeutic strategy in the treatment of glioblastomas.

PurposeGlioblastomas are highly aggressive brain tumors. Various pathways are involved in gliomagenesis, among which the Wingless (Wnt) signaling. Dickkopf protein-related protein 3 (Dkk-3) interacts with proteins of Wnt pathwayas inhibitor. The Wnt signaling contributes to activity of the claudins, that are critical components of tight junctions, whose expression was altered selectively in cerebral microvessels of glioblastoma. The aim of this study was to determine the role of Wnt pathways in the regulation of tumor growth, apoptosis process by targeting Dkk-3, tight junctions alteration involving claudin-5, suggesting possible therapeutic interactions involving Wnt/Toll-like receptors (TLRs) pathways.ResultsWe showed a significant decreasing of Dkk-3 and claudin-5 in human glioblastoma cell lines, as well as in U-87 MG xenograft tumors and in glioblastoma human patient’s tissues, with an involvement of the apoptosis process. Also, an interesting TLR-4/Wnt modulation highlighted that the absence of TLR-4 determined resistance to the tumor onset.ConclusionsWe concluded that combined modulation of Wnt/Dkk-3/claudin-5 and TLR-4 pathways, simultaneously targeting apoptosis and survival signaling defects, might shift the balance from tumor growth stasis to cytotoxic therapeutic responses, flowing in greater therapeutic benefits.MethodsIn the present study we investigated the expression of Dkk-3, claudin-5, apoptosis markers and TLR-4 receptor protein levels in in vitro studies on U-138MG, A-172, LN-18 and LN-229 human glioblastoma cell lines, and in vivo study using TLR-4 KO mice and in glioblastoma human patient’s tissues.

Delta-6-desaturase inhibitor enhances radiation therapy in glioblastoma in vitro and in vivo.

BackgroundIt has been reported that cell inflammation pathways contribute to the development of prostaglandin E2 (PGE2)-inhibitor of DNA-binding protein-1 (ID1)-dependent radio-resistance in glioblastoma. Here, we proposed that inhibiting delta-6-desaturase (D6D) could block arachidonic acid synthesis and PGE2 production, thereby reversing PGE2-ID1-dependent radioresistance in glioblastoma cells and xenograft tumor models.Materials and methodsTwo glioblastoma cell lines, namely, U-87 MG and LN-229, were used for the in vitro study. The combination effects of SC-26196 (a D6D inhibitor) and radiation were assessed by the MTS assay, colony formation assay, and cell apoptosis analysis. HPLC/MS analysis was performed to quantify the production of arachidonic acid and PGE2. For the in vivo study, 6-week-old nude mice, each bearing a U-87 MG xenograft tumor, were subjected to 4-week treatments of vehicle, SC-26196, radiation, or the combination of both. Tumor growth was monitored during the treatment, and the tumor tissues were collected at the end for further analysis.ResultsTreatment with SC-26196 significantly improved radiosensitivity in both glioblastoma cell lines in vitro, and radiosensitivity was associated with inhibited synthesis of arachidonic acid and PGE2. The combination of SC-26196 and radiation synergistically inhibited U-87 MG xenograft tumor growth, in association with the induction of tumor apoptosis and suppressed tumor proliferation. SC-26196 also inhibited arachidonic acid and PGE2 production in vivo and limited expression of ID1.ConclusionThese data suggested that the D6D inhibitor could reverse PGE2-ID1-dependent radioresistance in glioblastoma cells and xenograft tumor models by blocking the synthesis of arachidonic acid and PGE2. Although further investigation is required, the outcomes from this study may guide us in developing a potentially novel combination strategy for current glioblastoma therapy.

Evaluation of lauroyl-gemcitabine-loaded hydrogel efficacy in glioblastoma rat models.

Anticancer drug-loaded hydrogels are a promising strategy for the local treatment of incurable brain tumors such as glioblastoma (GBM). Recently, we demonstrated the efficacy of lauroyl-gemcitabine lipid nanocapsule hydrogel (GemC12-LNC) in a U-87 MG xenograft orthotopic mouse model. In this study, we developed a reliable and reproducible surgical procedure to resect orthotopic GBM tumors in rats. GemC12-LNC hydrogel integrity was tested after brain administration in rats and its anti-tumor efficacy was tested on a 9L syngeneic orthotopic model. We demonstrated that LNC integrity is maintained at least for one week after local administration of GemC12-LNC. GemC12-LNC was able to delay the formation of recurrences in 9L tumor-bearing resected rats, demonstrating the efficacy of this nanomedicine hydrogel in this preclinical model. Our results confirm that GemC12-LNC, a hydrogel uniquely formed by a nanocarrier and a cytotoxic drug, could be a promising and safe delivery tool for the local treatment of operable GBM tumors.

Histone deacetylase 1 promotes glioblastoma cell proliferation and invasion via activation of PI3K/AKT and MEK/ERK signaling pathways

Histone deacetylase 1 (HDAC1) plays a crucial role in cancer progression and development. This enzyme has been confirmed to be a key regulator of tumor biology functions, such as tumor cell proliferation, migration and invasion. However, HDAC1 expression in glioma remains controversial, and its specific function and molecular mechanism in glioblastoma is poorly understood. In this study, our findings demonstrated that protein and mRNA levels of HDAC1 were increased in glioma cell lines and glioma tissues compared to normal glial cell lines and non-neoplastic brain tissues, respectively. Furthermore, HDAC1 knockdown cells displayed decreased proliferation and invasion capabilities, whereas HDAC1 overexpressing glioblastoma cells displayed more proliferation and invasion capabilities in vitro. These novel outcomes suggested that knockdown of HDAC1 possibly suppressed the expression of phosphorylated AKT (p-AKT) and phosphorylated ERK (p-ERK) proteins, while overexpression of HDAC1 significantly increased p-AKT and p-ERK protein in glioblastoma cells. In addition, knockdown of HDAC1 repressed subcutaneous tumor growth in vivo, and led to down-regulation of p-AKT and p-ERK protein in U87 MG xenograft tumors. For the first time, we have demonstrated that HDAC1 promotes proliferation and invasion in glioblastoma cells by activating PI3K/AKT and MEK/ERK signaling pathways in vitro and in vivo. These results suggest that HDAC1 may be a novel biomarker and potential therapeutic target in glioblastoma.