Growth Control of C6 glioma in vivo by Nerve Growth Factor

Treatment with nerve growth factor (NGF) causes differentiation of rat C6 glioma cells and strongly inhibits their proliferation in vitro. This suggests that induction of NGF-mediated differentiation may provide a novel therapeutic approach to growth control of glial tumors. We examined the effects of NGF treatment on the growth potential of C6 glioma, which expressed NGF receptor in vivo. C6 glioma cells (1 × 10⁶ cells/10 l) were transplanted into the rat striatum. After 4 days, the animals were given successive injections of 100 ng NGF into the growing tumor at every 4 days (n = 10 rats). Controls were subjected to identical procedures with vehicle which did not contain NGF (n = 10 rats). At 14 days after transplantation, we evaluated the tumor volume, proliferative cell index (PCI) based on the MIB-1 immunoreactivity and enzyme activities related to energy metabolism by enzyme histochemistry. We found that the NGF treatment markedly reduced the tumor volume of the C6 glioma (34.00 ± 8.47 mm³ to 7.22 ± 4.92 mm³, p < 0.01). NGF treatment also decreased the PCI (33.34 ± 9.57% to 3.85 ± 3.56%, p < 0.01) with a negative correlation with tumor volume (r = 0.972, p < 0.01), and the hexokinase (HK) and glucose-6-phosphate dehydrogenase (G6PDH) activities (p < 0.01 and p < 0.01, respectively) which reflect the demand for nucleic acid synthesis for proliferation through the glycolytic and pentose phosphate pathways. The present results demonstrate for the first time that inhibition of tumor cell proliferation of C6 glioma by NGF occurs in vivo, probably through the NGF-mediated differentiation of C6 glioma cells which has been observed in in vitro studies.     

Control of Proliferation and Survival of C6 Glioma Cells with Modification of the Nerve Growth Factor Autocrine System

Nerve growth factor (NGF) plays an important physiological role in differentiation and survival of various types of neurons. Glial cells and glial tumor cells synthesize multiple neurotrophic factors including NGF and secrete them into the surrounding environment; however, the mechanisms of NGF and the significance of NGF receptors have not been studied in detail. The C6 glioma cell line can synthesize NGF, respond to exogenous application of NGF and stimulate the expression of NGF receptor in an autocrine manner. In order to determine the significance of such an NGF autocrine system, the effects of exposure to exogenous NGF and deprivation of endogenous NGF were examined in a C6 glioma cell line in vitro. Exogenous NGF significantly inhibited maintenance of the cell number and thymidine incorporation. Morphological changes, including the formation of growth cones, outgrowth of processes and cellular hypertrophy, were observed, concurrently, indicating that exogenous NGF stimulated differentiation and thereby inhibited proliferation of the cells. Deprivation of endogenous NGF with anti-NGF antibody elicited a rapid decrease in cell number and thymidine incorporation, and led almost all of the cells to death within 8 days. The protein synthesis inhibitor, cycloheximide, strongly inhibited the death of NGF-deprived cells, suggesting the involvement of an active process requiring synthesis of suicide proteins. These findings imply that the NGF autocrine system plays a significant role in regulating the differentiation and survival of C6 glioma cells, similarly to neuronal cells.     

Differentiation and Growth Inhibition of Glioma Cells Induced by Transfer of trk A Proto-oncogene

The induction of growth inhibition and differentiation of a glioma cell line by transfection of trk A cDNA was examined, and production of endogenous nerve growth factor (NGF) also was studied in these cells. When human trk A cDNA was transfected into a human glioma cell line, U-251MG, which lacks expression of both endogenous trk A and low-affinity NGF receptor, the transfectant expressed the exogenous trk A mRNA and a functional high-affinity NGF receptor. Transfection of trk A cDNA caused a partial induction of cell differentiation, G1 arrest, growth inhibition, tyrosine phosphorylation of the trk A proto-oncogene product, and activation of MAP kinase. Exogenous NGF treatment induced further terminal differentiation and growth inhibition. In summary, our data suggest that endogenous NGF secreted by glioma cells has an important role in the induction of glioma-cell differentiation occuring with transfer of exogenous trk A cDNA.     

ProBDNF and its receptors are upregulated in glioma and inhibit the growth of glioma cells in vitro

Background

High-grade glioma is incurable, with a short survival time and poor prognosis. The increased expression of p75 neurotrophin receptor (NTR) is a characteristic of high-grade glioma, but the potential significance of increased p75NTR in this tumor is not fully understood. Since p75NTR is the receptor for the precursor of brain-derived neurotrophic factor (proBDNF), it is suggested that proBDNF may have an impact on glioma.

Methods

In this study we investigated the expression of proBDNF and its receptors p75NTR and sortilin in 52 cases of human glioma and 13 cases of controls by immunochemistry, quantitative real-time PCR, and Western blot methods. Using C6 glioma cells as a model, we investigated the roles of proBDNF on C6 glioma cell differentiation, growth, apoptosis, and migration in vitro.

Results

We found that the expression levels of proBDNF, p75NTR, and sortilin were significantly increased in high-grade glioma and were positively correlated with the malignancy of the tumor. We also observed that tumors expressed proBDNF, p75NTR, and sortilin in the same cells with different subcellular distributions, suggesting an autocrine or paracrine loop. The ratio of proBDNF to mature BDNF was decreased in high-grade glioma tissues and was negatively correlated with tumor grade. Using C6 glioma cells as a model, we found that proBDNF increased apoptosis and differentiation and decreased cell growth and migration in vitro via p75NTR.

Conclusions

Our data indicate that proBDNF and its receptors are upregulated in high-grade glioma and might play an inhibitory effect on glioma.     

Vaccinia virus-mediated expression of wild-type p53 suppresses glioma cell growth and induces apoptosis

The use of vaccinia virus vectors for cancer gene therapy may become a powerful method to achieve efficient anti-tumor effects. We used recombinant vaccinia virus expressing wild-type p53 (rVV-p53) to examine the biological effects of exogenous tumor suppressor p53 in human (U-373MG, U-87MG, LN-Z308) and rat glioma cells (9L, C6) in vitro. All glioma cell lines infected with rVV-p53 exhibited growth inhibition and underwent apoptosis as demonstrated by morphological studies using nuclear staining and flow cytometry. The key role of p53 in cell growth inhibition was confirmed as measured by colony forming efficiency. Growth inhibition and apoptosis were independent of the endogenous p53 status of the glioma cell lines.     

Growth Inhibition and Radiosensitization of Cultured Glioma Cells by Nitric Oxide Generating Agents

The authors examined the effect of nitric oxide (NO) generating agents on the growth and radiosensitivity of cultured glioma cells. Three glioma, rat C6, and human T98G and U87 cell lines were treated with the NO generating agents, S-nitroso-N-acetyl-penicillamine (SNAP) or sodium nitroprusside (SNP). These agents released NO in the cell culture media and inhibited the growth of the glioma cells. Growth-inhibition was attenuated by hemoglobin, a known inhibitor of NO, suggesting it is mediated by NO. When C6 and T98G cells were irradiated in the presence of SNAP or SNP at 100µM, radiosensitization was observed. SNAP at 100µM exhibited a sensitizer enhancement ratio (SER) of 1.4 for C6 cells and 1.8 for T98G cells. SNP at 100µM only radiosensitized T98G cells with a SER of 1.9. The effect of SNP on radiosensitization of C6 cells was unclear. We conclude that NO generating agents are potential growth inhibitors and radiosensitizers for malignant glioma cells. NO mediated radiosensitization of glioma cells by NO generating agents may offer a new therapeutic approach for malignant glioma.     

An anti-apoptotic role for NGF receptors in human rhabdomyosarcoma

The expression and biological function of Nerve Growth Factor (NGF) receptors was studied in a panel of rhabdomyosarcoma cell lines derived from embryonal and alveolar histotype. All the cell lines expressed both the high affinity receptor TrkA and the low affinity receptor p75(NTR). Treatment with exogenous NGF did not considerably alter rhabdomyosarcoma cell growth or differentiation, but significantly inhibited spontaneous apoptosis as well as apoptosis, and induced by serum starvation or apoptosis induced by treatment with cycloheximide (CHX). Rhabdomyosarcoma cell lines expressed NGF and other neurotrophins and trace amounts of NGF protein were found in the supernatants of rhabdomyosarcoma cell cultures. Blocking the putative autocrine loop with an anti-NGF antibody resulted in an increase in apoptosis compared with control cultures. These data suggest that the simultaneous presence of both high and low affinity NGF receptors engaged by endogenous or exogenous NGF might contribute to the escape from apoptosis exhibited by the rhabdomyosarcoma cells.     

Induced interleukin-33 expression enhances the tumorigenic activity of rat glioma cells

Background

Glioma development is a multistep process associated with progressive genetic alterations but also regulated by cellular and noncellular components in a tumor-associated niche.

Methods

Using 2 rat C6 glioma cell clones with different tumorigenesis, named C6-1 and C6-2, this study characterized genes associated with enhanced tumorigenic features of glioma cells by comparative cDNA microarray analysis combined with Q-PCR. Neurospehere formation and clonogenicity were examined to determine the growth of tumorigenic C6 glioma cells. The lentivirus-mediated gene knockdown approach was conducted to determine the role of interleukin-33 (IL-33) in glioma cell proliferation and migration. Transwell cell invasion assay was used to examine microglia migration induced by tumorigenic C6 cells.

Results

The functional analysis of gene ontology (GO) biological processes shows that the upregulated genes found in tumorigenic C6 (C6-1) cells are closely related to cell proliferation. Tumorigenic C6 cells expressed cytokines and chemokines abundantly. Among these genes, IL-33 was profoundly induced in tumorigenic C6 cells with the expression of IL-33 receptor ST2. Furthermore, the growth rate and colony formation of tumorigenic C6 cells were attenuated by the inhibition of IL-33 and ST2 gene expression. Moreover, IL-33 was involved in tumorigenic glioma cell migration and regulation of the expression of several glioma-associated growth factors and chemokines in tumorigenic C6 cells.

Conclusion

Accordingly, we concluded that glioma cells with abundant production of IL-33 grow rapidly; moreover, the interactions of multiple cytokines/chemokines induced by glioma cells may develop a microenvironment that facilitates microglia/macrophage infiltration and fosters glioma growth in the brain.     

Anti-apoptotic role and clinical relevance of neurotrophins in diffuse large B-cell lymphomas

Background:

Diffuse large B-cell lymphoma (DLBCL) is a fatal malignancy that needs to identify new targets for additional therapeutic options. This study aimed to clarify the clinical and biological significance of endogenous neurotrophin (nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF)) in DLBCL biopsy samples and cell lines.

Methods:

We analysed expression of NGF, BDNF, and their receptors (Trk, p75^NTR) in 51 biopsies and cell lines by immunohistochemistry, immunofluorescence, and western blotting. To investigate the biological role of BDNF/TrkB/p75^NTR axis, effects of neurotrophin signalling inhibition were determined on tumour cell survival and vascular endothelial growth factor (VEGF) secretion. The pharmacological pan-Trk inhibitor K252a was used for in vitro and in vivo studies.

Results:

A BDNF/TrkB axis was expressed in all biopsies, which was independent of the germinal centre B-cell (GCB)/non-GCB profile. p75^NTR, TrkB, and BDNF tumour scores were significantly correlated and high NGF expression was significantly associated with MUM1/IRF4, and the non-GCB subtype. Diffuse large B-cell lymphoma cell lines co-expressed neurotrophins and their receptors. The full-length TrkB receptor was found in all cell lines, which was also phosphorylated at Tyr-817. p75^NTR was associated to Trk and not to its cell death co-receptor sortilin. In vitro, inhibition of neurotrophin signalling induced cell apoptosis. K252a caused cell apoptosis, decreased VEGF secretion, and potentiated rituximab effect, notably in less rituximab-sensitive cells. In vivo, K252a significantly reduced tumour growth and potentiated the effects of rituximab in a GCB-DLBCL xenograft model.

Conclusions:

This work argues for a pro-survival role of endogenous neurotrophins in DLBCLs and inhibition of Trk signalling might be a potential treatment strategy for rituximab resistant subgroups.     

Assessment of laminin-mediated glioma invasion in vitro and by glioma tumors engrafted within rat spinal cord

Summary Cell motility within central nervous system (CNS) neuropil may be largely restricted yet infiltration by glioma cells is commonly observed. Glioma cells remodel nervous tissue and may assemble extracellular matrix in order to migrate. We examined the rat C6 glioma cell line for laminin expression and response in vitro and following engraftment into rat spinal cord. C6 cell cultures expressed laminin-2. C6 cells attached equally well to substrates of purified laminin-1 and laminin-2 and laminin-2-enriched C6 conditioned medium. In contrast, C6 cell migration was substantially greater on laminin-2 and C6-derived substrata than on laminin-1. Glioma cell attachment to laminin-1 and -2 was largely inhibited by antibody to the laminin receptor LBP110 and by an IKVAV peptide but not by YIGSR or control peptides. IKVAV peptide and anti-LBP110 antibodies also inhibited glioma cell invasion through synthetic basement membrane. Anti-₁ integrin antibody selectively inhibited cell migration and invasion on laminin-2 substrata without affecting percent cell attachment. These findings suggest C6 cell migration and invasion are promoted by autocrine release of laminin-2 and involve LPB110 and ₁ integrin laminin receptors.A possible role for laminin-2 in CNS infiltration in vivo was examined following glioma engraftment into rat spinal cord. Engrafted C6 tumors share many histologic features of invasive human glioma. Engrafted glioma cells expressed laminin, LBP110 and ₁ integrin antigens, indicating the molecular mechanisms of C6 motility observed in culture may contribute to glioma invasion in vivo. NMR and corroborative immunocytochemistry provided precise means to monitor tumor progression following glioma engraftment into rat spinal cord. Advantages of this glioma model are discussed regarding the assessment of anti-adhesive therapies in vivo.     

Cell adhesion molecules acting between C6 glioma and endothelial cells

Summary The interactions between tumor cells and endothelium play a key role in the process of tumor growth, local invasion, and distant metastasis. In the present study, we examined the adhesion of C6 glioma cells to bovine endothelial cell (EC) monolayers and defined the cell adhesion molecules acting between these cells. Pretreatment of the EC monolayer with cytokines, tumor necrosis factor (TNF)-, interleukin (IL)-1, and interferon (INF)-, significantly increased the adhesion of C6 glioma cells to the EC monolayer. The effect lasted more than 24 hours and was protein-synthesis dependent. The adhesion of C6 glioma cells to TNF-activated ECs was blocked by the monoclonal antibody to the intercellular adhesion molecule-1 (ICAM-1) or ₂ integrin, whereas that of melanoma cells was not. These findings provide evidence that ICAM-1 and ₂ integrin function as inducible cell surface molecules that can support the adhesion of C6 glioma cells to ECs, and may contribute to the characteristic growth of glial tumorsin vivo.     

Systemic treatment with murine recombinant interleukin-1β inhibits the growth and progression of malignant glioma in the rat

We investigated the effects of daily subcutaneous (SC) injections of 100, 200, or 400 g/kg murine recombinant interleukin-1 (rIL-1) or its excipient on normal Fischer 344 rats and ones harboring a malignant RT-2 glioma. The tumor model has a predictable course with animals dying on days 14–17 following an intracerebral inoculation of 10⁴ RT-2 glioma cells. Treatments with (rIL-1) or excipient began on day seven post-tumor inoculation and continued for 7 days. We observed no significant effect on core body temperatures although there was a significant (p < 0.05) decrease in body weight in all (rIL-1) treated animals. When tumor-bearing animals became moribund, they received an intraperitoneal injection of bromodeoxyuridine (BUdr) and were sacrificed two hours later. Blood samples were obtained prior to their sacrifice by transcardiac perfusion with a buffered aldehyde solution. Recombinant IL-4ß affected blood differentials; causing neutrophilia, lymphopenia, and slight thrombocythemia. The BUdr labeling index of glioma cells did not significantly differ between treatment groups, although tumors differed histologically at the time of necropsy. Tumors of rIL-1 treated animals had more extensive necrosis and a greater degree of leukocyte infiltration. Survival studies were conducted in which rats were given continuous daily SC injections of (rIL-1) until day of death. Overall survival between the two groups differed significantly in studies using 100 g/kg/d (p < 0.05); (rIL-1ß) treated rats had a mean survival time of 22 (± 3.0) days while excipient controls had a mean survival time of 17 (± 0.5) days. Similarly, at a dose of 200 g rIL-1(3/kg/d), mean survival was significantly (p < 0.05) increased as compared to excipient controls (18.75 ± 1.5 vs. 15.25 ± 1.7 days, respectively). Daily injections of 400 g/kg did not significantly increase the survival of glioma bearing animals, possibly as a consequence of fIL-1ß toxicity at this dose.     

Synergistic Effect of Genistein and BCNU on Growth Inhibition and Cytotoxicity of Glioblastoma Cells

Objective: Recent experiments have shown that dietary soy isoflavones such as genistein can significantly suppress invasiveness and growth of a number of human malignancies. This study examined whether genistein, at a concentration typical of plasma levels following soy diet intake, in combination with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, carmustine) exhibited an additive or synergistic inhibitory effect on the growth of glioma cells. Methods: The human glioblastoma multiforme (GBM) cell line U87 and the rodent C6 glioma were treated with genistein at 4M, combined with BCNU (0–50M). Monolayer cell growth and cytotoxicity, as measured by colonigenic survival in soft agarose, were then compared in control and drug-treated cultures. Presence of apoptosis, using the DNA ladder assay and laser scanning cytometry (LSC), was investigated in all cell lines at those concentrations where an enhancement of antiproliferative effect of BCNU in presence of genistein was observed. Results: A 32–41% increase in monolayer growth inhibition and a 28–42% increase in colony cytotoxicity in the U87 cell line were observed when genistein (4M) was added to BCNU in the 0–10M dose range. In the C6 cell line, a 30–36% increase in monolayer growth inhibition and a 39–54% increase in colony cytotoxicity were observed with the BCNU dose range of 0–50M. All experiments showed a significant increase in growth inhibition and a decrease in colonogenic survival (P<0.05). We were unable to detect apoptosis in any of the lines when genistein was combined with BCNU. Conclusion: These results indicate that genistein at typical adult dietary plasma levels can significantly enhance the antiproliferative and cytotoxic action of BCNU. The implication for treatment of GBM may be a reduction in the chemotherapeutic dose recommendations of these agents and subsequently a decrease in the risk of treatment sequelae for these patients.     

Interaction of transforming growth factor-β (TGF-β) and epidermal growth factor (EGF) in human glioma cells

Gliomas are characterized by a deregulation of growth factor production and growth factor receptors expression, e.g. overproduction of the cytokine transforming growth factor- (TGF-) and overexpression/constitutive activation of receptors for the epidermal growth factor (EGF). Potential interactions of such growth factors and their signaling cascades could enhance the malignancy of these tumors. Therefore, we investigated the effects of TGF- and EGF alone and in combination on the proliferation of glioma cells cultivated from eight solid human WHO grade IV gliomas and one glioma cell line, analyzed the expression and intactness of the TGF--signaling molecules Samd-4 and -2, and the phosphorylation of the EGF-signaling kinases ERK 1/2. The effects were divergent and complex: Whereas EGF mostly stimulated glioma cell proliferation, TGF- either enhanced, inhibited or had no significant effect on proliferation. In combination, co-stimulation and inhibition of the EGF-induced mitogenic activity could be observed. Smad-4/-2 were expressed in all glioma cells, one point mutation at base 1595 in Smad-4 did not affect its protein sequence. In part of the glioma cells, reduced phosphorylation of ERK 1/2 and expression of cyclin-dependent kinase inhibitor 1 or p21 was observed in co-stimulation experiments. These experiments show that TGF- can inhibit EGF-mediated effects only in some gliomas, whereas it enhances it in others. The interaction of both factors is very complex and varies between different gliomas.     

Exogenous IGFBP-2 promotes proliferation,invasion, and chemoresistance to temozolomide in glioma cells via the integrin β1-ERK pathway

Background:

Insulin-like growth factor binding protein-2 (IGFBP-2) is significantly increased in the serum of patients with malignant gliomas. High plasma IGFBP-2 levels are correlated with poor prognosis in glioma patients. However, the exact role of exogenous IGFBP-2 in gliomas is unclear.

Methods and results:

Using the MTT cell viability assay, cell cycle analysis, and the transwell migration assay, it was demonstrated that IGFBP-2 treatment stimulated proliferation and invasion in U87 and U251 cell lines and primary SU3 glioma cells. Western blot analysis and immunofluorescence staining revealed that IGFBP-2 promoted ERK phosphorylation and nuclear translocation. Moreover, blocking ERK activation using the inhibitor PD98059 markedly reduced the effects of IGFBP-2 in glioma cells. As IGFBP-2 has an integrin-binding domain, the contribution of integrin β1 to these IGFBP-2-mediated processes was examined. Neutralisation or knockdown of the expression of integrin β1 inhibited IGFBP-2-induced ERK activation, cell proliferation, and cell invasion. Significantly, IGFBP-2 induced temozolomide resistance in glioma cells in an integrin β1/ERK-dependent manner.

Conclusions:

Exogenous IGFBP-2 induces proliferation, invasion, and chemoresistance in glioma cells via integrin β1/ERK signaling, suggesting that targeting this pathway could represent a potential therapeutic strategy for the treatment of gliomas. The identification of this pathway in glioma progression provides insight into the mechanism by which serum IGFBP-2 levels can predict the prognosis of glioma patients.     

Growth inhibitory effect of recombinant α and β interferon on human glioma cells

Summary Growth inhibitory activity of recombinant and interferon on two human glioma cell lines, EFC-2 and KE cells, was determined by two different growth assays. Recombinant interferon showed slight growth inhibitory effect on EFC-2 cells at day 3, and maximum inhibition was seen on day 6 with an ID50 of 50 U/ml. Recombinant interferon showed no significant growth inhibition at any concentration. KE cells were resistant to both recombinant and interferon. The growth inhibitory activity of recombinant interferon on EFC-2 cells was not blocked by recombinant interferon, although recombinant and interferons shared same receptors on EFC-2 cells. Addition of DFMO (-difluoromethylornithine) to interferon in the media showed additive effect rather than synergistic effect in growth inhibition of glioma cells. Out of 7 glioma cell lines tested, 4 showed heterogeneous sensitivity to recombinant interferon, and all were resistant to recombinant interferon. These results suggest differential sensitivity of EFC-2 cells to recombinant interferon, as well as a heterogeneous sensitivity to recombinant interferon among different glioma cell lines.     

Mitogenesis in Glioblastoma Multiforme Cell Lines: A Role for NGF and its TrkA Receptors

Neurotrophins have definitive roles in the growth/maintenance of neuronal populations, but their function in malignant gliomas is unknown. The ability for nerve growth factor (NGF) to serve as a mitogenic agent was investigated in several human glioblastoma multiforme (GBM) cell lines, including U251, U87, and U373. In a serum-free medium, the addition of NGF (200ng/ml) to these cell lines increased cell counts over controls, after 3 days in culture by 9%, 16%, and 33%, respectively. Dose-dependent increases in cell counts and [³H]thymidine uptake were found in the more rigorously investigated U373 cell line. Proteins for both the high affinity NGF-specific tyrosine kinase binding site (p140^TrkA; TrkA) and the low affinity neurotrophin (p75^NTR) receptor were present in all three GBM cell lines. TrkA mRNA was identified in U373 (only cell line studied). NGF-stimulated proliferation was inhibited in a dose-dependent fashion by K252a, a blocker of Trk-induced receptor kinases. NGF, measured by ELISA, was detectable in all GBM cell lines even after 7 days of growth in serum-free medium. These data suggest that GBM cell growth can be enhanced by NGF acting via Trk receptor phosphorylation. Future studies of antiproliferative therapies should consider agents directed against intracellular Trk signaling cascades.     

MiR-125b acts as an oncogene in glioblastoma cells and inhibits cell apoptosis through p53 and p38MAPK-independent pathways

Background:

We have recently identified miR-125b upregulation in glioblastoma (GMB). The aim of this study is to determine the correlation between miR-125b expression and malignant grades of glioma and the genes targeted by miR-125b.

Methods:

Real-time PCR was employed to measure the expression level of miR-125b. Cell viability was evaluated by cell growth and colony formation in soft-agar assays. Cell apoptosis was determined by Hoechst 33342 staining and AnnexinV-FITC assay. The Luciferase assay was used to confirm the actual binding sites of p38MAPK mRNA. Western blot was used to detect the gene expression level.

Results:

The expression level of miR-125b is positively correlated with the malignant grade of glioma. Ectopic expression of miR-125b promotes the proliferation of GMB cells. Knockdown of endogenous miR-125b inhibits cell proliferation and promotes cell apoptosis. Further studies reveal that p53 is regulated by miR-125b. However, downregulation of the endogenous miR-125b also results in p53-independent apoptotic pathway leading to apoptosis in p53 mutated U251 cells and p53 knockdown U87 cells. Moreover, p38MAPK is also regulated by miR-125b and downregulation of miR-125b activates the p38MAPK-induced mitochondria apoptotic pathway.

Conclusion:

High-level expression of miR-125b is associated with poor outcomes of GMB. MiR-125b may have an oncogenic role in GMB cells by promoting cell proliferation and inhibiting apoptosis.