Target For Glioma Therapy Research Articles

Evaluation of folate‐PAMAM for the delivery of antisense oligonucleotides to rat C6 glioma cells in vitro and in vivo

In the current study, we evaluated the efficiency of folate-polyamidoamine dendrimers conjugates (FA-PAMAM) for the in situ delivery of therapeutic antisense oligonucleotides (ASODN) that could inhibit the growth of C6 glioma cells. Folic acid was coupled to the surface amino groups of G5-PAMAM dendrimer (G5D) through a 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide bond, and ASODNs corresponding to rat epidermal growth factor receptor (EGFR) were then complexed with FA-PAMAM. At an ASODN to PAMAM ratio of 16:1, agarose electrophoresis indicated that antisense oligonucleotides were completely complexed with PAMAM or FA-PAMAM. The ASODN transfection rates mediated by FA-PAMAM and PAMAM were superior to oligofectamine, resulting in greater suppression of EGFR expression and glioma cell growth. Stereotactic injection of EGFR ASODN:FA-PAMAM complexes into established rat C6 intracranial gliomas resulted in greater suppression of tumor growth and longer survival time of tumor-bearing rats compared with PAMAM and oligofectamine-mediated EGFR-ASODN therapy. The current study demonstrates the suitability of folate-PAMAM dendrimer conjugates for efficient EGFR ASODN delivery into glioma cells, wherein they release the ASODN from the FA-PAMAM to knock down EGFR expression in C6 glioma cells, both in vitro and in vivo. FA-PAMAM may thus represent a novel delivery system for short oligonucleotides in glioma-targeted therapy.

Down-regulation of LRIG2 expression by RNA interference inhibits glioblastoma cell (GL15) growth, causes cell cycle redistribution, increases cell apoptosis and enhances cell adhesion and invasion in vitro

The leucine-rich and immunoglobulin-like domains (LRIG) gene family contains LRIG1, 2 and 3. LRIG1 is a negative regulator of EGFR, but little is known about the function of LRIG2. To determine the role of LRIG2 in the progression of glioma, we performed RNA interference-mediated knockdown of LRIG2 in a human glioma cell line (GL15). Down-regulation of LRIG2 expression resulted in: rapid EGF-mediated loss of EGFR; decreased proliferation; G0/G1 arrest; increased spontaneous apoptosis; enhanced cell adhesion and increased invasion capability of GL15 cells in vitro. These findings indicate that LRIG2 possesses distinct functions compared with LRIG1 and validate the attractiveness of LRIG2 as a target in glioma therapy.

Rosiglitazone reduces cell invasiveness by inducing MKP-1 in human U87MG glioma cells

We sought to investigate the molecular mechanisms by which rosiglitazone (RGZ) inhibits cell invasion in human glioma cells. In this study, we found that RGZ attenuated MMP-2 protein levels, MMP-2 gelatinolytic activity, and cell invasiveness through a PPAR-γ independent pathway. RGZ increased mitogen activated protein kinase phosphatase-1 (MKP-1) expression. The addition of triptolide (a diterpenoid triepoxide, which blocked MKP-1 induction) abolished the inhibitory effects by RGZ. Furthermore, we demonstrated that the knock down of MKP-1 by MKP-1 specific small interference RNA reversed the reduction of MMP-2 secretion, and of cell invasiveness by RGZ. In contrast, the stable expression of MKP-1 in glioma cell lines decreased MMP-2 activity and cell invasiveness. These results suggest that RGZ may mediate the inhibitory effects through MKP-1 induction. Thus, MKP-1 could be a potential target in glioma therapy.

Gamma-Secretase Represents a Therapeutic Target for the Treatment of Invasive Glioma Mediated by the p75 Neurotrophin Receptor

The multifunctional signaling protein p75 neurotrophin receptor (p75NTR) is a central regulator and major contributor to the highly invasive nature of malignant gliomas. Here, we show that neurotrophin-dependent regulated intramembrane proteolysis (RIP) of p75NTR is required for p75NTR-mediated glioma invasion, and identify a previously unnamed process for targeted glioma therapy. Expression of cleavage-resistant chimeras of p75NTR or treatment of animals bearing p75NTR-positive intracranial tumors with clinically applicable γ-secretase inhibitors resulted in dramatically decreased glioma invasion and prolonged survival. Importantly, proteolytic processing of p75NTR was observed in p75NTR-positive patient tumor specimens and brain tumor initiating cells. This work highlights the importance of p75NTR as a therapeutic target, suggesting that γ-secretase inhibitors may have direct clinical application for the treatment of malignant glioma.

Inhibition of glioblastoma growth and angiogenesis by gambogic acid: An in vitro and in vivo study

Gambogic acid (GA) is the major active ingredient of gamboge, a brownish to orange resin exuded from Garcinia hanburryi tree in Southeast Asia. The present study aims to demonstrate that gambogic acid (GA) has potent anticancer activity for glioblastoma by in vitro and in vivo study. Rat brain microvascular endothelial cells (rBMEC) were used as an in vitro model of the blood–brain barrier (BBB). To reveal an involvement of the intrinsic mitochondrial pathway of apoptosis, the mitochondrial membrane potential and the western blot evaluation of Bax, Bcl-2, Caspase-3, caspase-9 and cytochrome c released from mitochondria were performed. Angiogenesis was detected by CD31 immunochemical study. The results showed that the uptake of GA by rBMEC was time-dependent, which indicated that it could pass BBB and represent a possible new target in glioma therapy. GA could cause apoptosis of rat C6 glioma cells in vitro in a concentration-dependent manner by triggering the intrinsic mitochondrial pathway of apoptosis. In vivo study also revealed that i.v. injection of GA once a day for two weeks could significantly reduce tumor volumes by antiangiogenesis and apoptotic induction of glioma cells. Collectively, the current data indicated that GA may be of potential use in treatment of glioblastoma by apoptotic induction and antiangiogenic effects.

Inhibition of in Vivo Glioma Growth and Invasion by Peroxisome Proliferator-Activated Receptor γ Agonist Treatment

The peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor family, represents a possible new target in glioma therapy. Because PPARgamma plays a crucial role in regulation of insulin sensitivity, synthetic agonists are already in clinical use for type II diabetes treatment. Beyond these metabolic effects, PPARgamma agonists exhibit antineoplastic effects. In this study, we investigated the antineoplastic effects of the PPARgamma agonist pioglitazone in glioma cells. Pioglitazone reduced cellular viability of rat, human, and PPARgamma-overexpressing glioma cells in vitro in a time- and concentration-dependent manner. No antineoplastic effects were induced by pioglitazone in glioma cells overexpressing a PPARgamma mutant. Furthermore, proliferation was reduced by pioglitazone, as measured by Ki-67 immunoreactivity, in vitro. Continuous intracerebral infusion of pioglitazone into gliomas induced by intrastriatal injection of C6 cells reduced tumor volumes by 83%. Oral administration of pioglitazone reduced tumor volumes by 76.9%. Subsequent brain tissue analysis revealed induction of apoptotic cell death. Ki-67 expression and BrdU incorporation revealed a reduction of proliferation in vivo. Reduced invasion of C6 cells and lower matrix metalloproteinase 9 levels in vivo indicate pioglitazone-mediated reduction of invasion. Together, these data indicate that pioglitazone may be of potential use in treatment of malignant gliomas.

β1,4-Galactosyltransferase V Functions as a Positive Growth Regulator in Glioma

beta1,4-galactosyltransferase V (GalT V; EC 2.4.1.38) can effectively galactosylate the GlcNAcbeta1-->6Man arm of the highly branched N-glycans that are characteristic of glioma. Previously, we have reported that the expression of GalT V is increased in the process of glioma. However, currently little is known about the role of GalT V in this process. In this study, the ectopic expression of GalT V could promote the invasion and survival of glioma cells and transformed astrocytes. Furthermore, decreasing the expression of GalT V in glioma cells promoted apoptosis, inhibited the invasion and migration and the ability of tumor formation in vivo, and reduced the activation of AKT. In addition, the activity of GalT V promoter could be induced by epidermal growth factor, dominant active Ras, ERK1, JNK1, and constitutively active AKT. Taken together, our results suggest that GalT V functioned as a novel glioma growth activator and might represent a novel target in glioma therapy.

High expression of Aurora-B/Aurora and Ipll-like midbody-associated protein (AIM-1) in astrocytomas.

Impaired regulation of Aurora-B/AIM-1 expression in human cells causes chromosomal abnormality and instability, and recent observations of high expression but not mutation of Aurora-B/AIM-1 in human cancers imply that Aurora-B/AIM-1 might be a candidate molecule for cancer progression. We analyzed the effects of modification of Aurora-B/AIM-1 expression on the growth of a human glioma cell line and the expression of Aurora-B/AIM-1 in astrocytomas. A glioma cell line, U251MG was transfected with wild type (WT) of Aurora-B/AIM-1 or kinase-inactive mutant of Aurora-B/AIM-1 in order to test the effects of overexpression of WT or kinase-inactive Aurora-B/AIM-1 on cell morphology and cell growth. Brain tissue samples were obtained during surgery and processed for reverse transcription-polymerase chain reaction, immunofluorescence in order to analyze the expression of Aurora-B/AIM-1 mRNA and protein. Exogenous overexpression of WT of Aurora-B/AIM-1 in cultured cells of U251MG produced multinuclearity and increased ploidy, and inhibited the growth of tumor cells. Exogenous overexpression of kinase-inactive Aurora-B/AIM-1 in a human glioma cell line also suppressed the tumor cell growth without affecting ploidy. Aurora-B/AIM-1 was highly expressed in astrocytomas and U251MG, and mRNA and protein levels of Aurora-B/AIM-1 in tumor tissues well correlated with their histological malignancy (World Health Organization grading). Survival time also negatively correlated with the levels of Aurora-B/AIM-1 mRNA in tumor samples. Aurora-B/AIM-1 was highly expressed in high-grade gliomas and its expression was well correlated with histological malignancy and clinical outcomes. The modification of the level of Aurora-B/AIM-1 expression might be a new target for glioma therapy.