Mediation of multiple pathways regulating cell proliferation, migration, and apoptosis in the human malignant glioma cell line U87MG via unphosphorylated STAT1

Neuropilin-1 enhances temozolomide resistance in glioblastoma via the STAT1/p53/p21 axis

Glioblastoma (GBM) is the most prevalent primary intracranial tumor. Temozolomide (TMZ) is the first-line chemotherapy for GBM. Nonetheless, the development of TMZ resistance has become a main cause of treatment failure in GBM patients. Evidence suggests that neuropilin-1 (NRP-1) silencing can attenuate GBM cell resistance to TMZ. This study aims to determine potential mechanisms by which NRP-1 affects TMZ resistance in GBM. The parental U251 and LN229 GBM cells were exposed to increasing concentrations of TMZ to construct TMZ-resistant GBM cells (U251/TMZ, LN229/TMZ). BALB/c nude mice were injected with U251/TMZ cells to establish the xenograft mouse model. Functional experiments were carried out to examine NRP-1 functions. Western blotting and real-time quantitative polymerase chain reaction were used to evaluate molecular protein and mRNA expression, respectively. Immunohistochemical staining showed NRP-1 and STAT1 expression in mouse tumors. The results showed that NRP-1 was highly expressed in TMZ-resistant cells. Moreover, knocking down NRP-1 attenuated the TMZ resistance of U251/TMZ cells, while upregulating NRP-1 enhanced TMZ resistance of the parental cells. NRP-1 silencing elevated GBM cell sensitivity to TMZ in tumor-bearing mice. Depleting NRP-1 reduced STAT1, p53, and p21 expression in U251/TMZ cells. STAT1 depletion offset NRP-1 silencing evoked attenuation of GBM cell resistance to TMZ. Collectively, our study reveals that NRP-1 enhances TMZ resistance in GBM possibly by regulating the STAT1/p53/p21 axis.

CPVL promotes glioma progression via STAT1 pathway inhibition through interactions with the BTK/p300 axis

CPVL (carboxypeptidase, vitellogenic-like) is a serine carboxypeptidase that was first characterized in human macrophages. However, the function of CPVL remains unclear in a variety of tumors. The quantitative PCR (qPCR), Western blotting, and IHC assays were utilized to measure the CPVL expression. CPVL was significantly upregulated in glioma cells and tissues compared with normal cells and tissues, respectively. Moreover, high CPVL expression was correlated with advanced clinical grade and poor prognosis. Silencing of CPVL promoted glioma cell apoptosis, and it inhibited cell proliferation and tumorigenicity in vitro and in vivo. Ingenuity Pathway Analysis (IPA) demonstrated that CPVL silencing activated the IFN-γ/STAT1 signaling pathway, thereby inducing glioma cell apoptosis. Mechanistically, immunopurification, mass spectrometry, IP, and glutathione S-transferase (GST) pull-down experiments elucidated that CPVL physically interacts with Bruton’s tyrosine kinase (BTK) and downregulates the STAT1 phosphorylation through promoting p300-mediated STAT1 acetylation. Our findings reveal the crucial role of CPVL in promoting the progression of glioma through suppressing STAT1 phosphorylation. CPVL might serve as a potential prognostic biomarker and therapeutic target for the treatment of glioma.

Molecular mechanisms of cordycepin emphasizing its potential against neuroinflammation: An update

Recent research emphasizes the central role of neuroinflammation in complex neurological disorders such as Alzheimer's disease, Parkinson's disease, depression, multiple sclerosis, and traumatic brain injury. Multiple pathological variables with identical molecular mechanisms have been implicated in the development of CNS inflammatory diseases. Therefore, one of the most crucial tasks in the management of CNS disorders is the alleviation of neuroinflammation. However, there are many drawbacks of new pharmacological drugs used in the management of CNS disorders, including medication side effects, and treatment complications. There is a growing inclination towards bioactive constituents of natural origin to unearth the potential remedies. Cordycepin, an adenosine analogue, is one such bioactive constituent with multiple actions, viz., anticancer, anti-inflammatory, hepato-protective, antidepressant, anti-Alzheimer's, anti-Parkinsonian and immunomodulatory effects, along with the promotion of remyelination. This review highlights the converging neuroinflammatory targets of cordycepin in Alzheimer's disease, Parkinson's disease, and depression, to substantiate its anti-neuroinflammatory property. Cordycepin acts by downregulation of adenosine A₂ receptor, inhibition of microglial activation, and subsequent inhibition of several neuroinflammatory markers (NF-κB, NLRP3 inflammasome, IL-1β, iNOS, COX-2, TNF-α, and HMGB1). Cordycepin mitigates LPS-mediated toll-like receptor activation by activating adenosine receptor A₁, thereby improving antioxidant enzymes (superoxide dismutase, glutathione peroxidase) levels. These pieces of evidence point to the probable anti-neuroinflammatory mechanisms of cordycepin, which could facilitate the development of new remedies against neuroinflammation-associated CNS disorders.

Bioinformatics Analysis of Expression Profiles and Prognostic Values of the Signal Transducer and Activator of Transcription Family Genes in Glioma

Signal transducer and activator of transcription (STAT) family genes—of which there are seven members: STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B, and STAT6—have been associated with the progression of multiple cancers. However, their prognostic values in glioma remain unclear. In this study, we systematically investigated the expression, the prognostic value, and the potential mechanism of the STAT family genes in glioma. The expression of STAT1/2/3/5A/6 members were significantly higher and positively correlated with IDH mutations, while the expression of STAT5B was lower and negatively correlated with IDH mutations in glioma. Survival analysis indicated that the upregulation of STAT1/2/3/5A/6 and downregulation of STAT5B expression was associated with poorer overall survival in glioma. Joint effects analysis of STAT1/2/3/5A/5B/6 expression suggested that the prognostic value of the group was more significant than that of each individual gene. Thus, we constructed a risk score model to predict the prognosis of glioma. The receiver operating characteristic curve and calibration curves showed good performance as prognostic indicators in both TCGA (The Cancer Genome Atlas) and the CGGA (Chinese Glioma Genome Atlas) databases. Furthermore, we analyzed the correlation between STAT expression with immune infiltration in glioma. The Protein–protein interaction network and enrichment analysis showed that STAT members and co-expressed genes mainly participated in signal transduction activity, Hepatitis B, the Jak-STAT signaling pathway, transcription factor activity, sequence-specific DNA binding, and the cytokine-mediated signaling pathway in glioma. In summary, our study analyzed the expression, prognostic values, and biological roles of the STAT gene family members in glioma, based on which we developed a new risk score model to predict the prognosis of glioma more precisely.

Up-regulation of MARVEL domain-containing protein 1 (MARVELD1) accelerated the malignant phenotype of glioma cancer cells via mediating JAK/STAT signaling pathway

This work aimed to research the function of MARVEL domain-containing protein 1 (MARVELD1) in glioma as well as its functioning mode. Bioinformatics analysis was utilized to assess the MARVELD1 expression in glioma tissues and its relationship with grade and prognosis, based on The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Chinese Glioma Genome Atlas (CGGA) databases. Cell Counting Kit-8 (CCK-8), colony formation, and Transwell assays were carried out to determine the impact of MARVELD1 on malignant biological behavior of glioma, such as proliferation, invasion, and migration. qRT-PCR was carried out to test the mRNA level of MARVELD1. Western blot assay was performed to measure the protein expression of MARVELD1 and JAK/STAT pathway-related proteins. MARVELD1 was expressed at high levels in glioma tissues and cell lines. Kaplan-Meier survival analysis revealed that the higher MARVELD1 expression, the shorter the survival time of patients with glioma. Also, the MARVELD1 expression in WHO IV was significantly enhanced compared to that in WHO II and WHO III. Furthermore, the functional analysis of MARVELD1 in vitro revealed that knockdown of MARVELD1 in U251 cells restrained cell proliferation, migration, and invasion, while up-regulation of MARVELD1 in U87 cells presented opposite outcomes. Finally, we found that JAK/STAT signaling pathway mediated the function of MARVELD1 in glioma. MARVELD1 contributed to promoting the malignant progression of glioma, which is the key driver of activation of JAK/STAT signaling pathway in gliomas.

The Role and Therapeutic Targeting of JAK/STAT Signaling in Glioblastoma

Glioblastoma remains one of the deadliest and treatment-refractory human malignancies in large part due to its diffusely infiltrative nature, molecular heterogeneity, and capacity for immune escape. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway contributes substantively to a wide variety of protumorigenic functions, including proliferation, anti-apoptosis, angiogenesis, stem cell maintenance, and immune suppression. We review the current state of knowledge regarding the biological role of JAK/STAT signaling in glioblastoma, therapeutic strategies, and future directions for the field.

Neuroinflammation Mediated by NLRP3 Inflammasome After Intracerebral Hemorrhage and Potential Therapeutic Targets

Intracerebral hemorrhage (ICH) is the most fatal subtype of stroke; there is still a lack of effective treatment. Microglia are a major component of the innate immune system, and they respond to acute brain injury by activating and forming classic M1-like (pro-inflammatory) or alternative M2-like (anti-inflammatory) phenotype. The existence of the polarization indicates that the role of microglia in disease's progression and recovery after ICH is still unclear, perhaps involving microglial secretion of anti-inflammatory or pro-inflammatory cytokines and chemokines. The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is considered to be the main participant in neuroinflammation. Recent evidence has shown that NLRP3 inflammasome can be activated after ICH, resulting in inflammatory cascade reactions and aggravating brain injury. Furthermore, previous studies have reported that NLRP3 inflammasome is mainly present in microglia, so we speculate that its activation may be strongly associated with microglial polarization. Many scholars have investigated the role of brain injury caused by NLRP3 inflammasome after ICH, but the precise operating mechanisms remain uncertain. This review summarized the activation mechanism of NLRP3 inflammasome after ICH and the possible mechanism of NLRP3 inflammasome promoting neuroinflammation and aggravating nerve injury and discussed the relevant potential therapeutic targets.

Activation of STAT1 by the FRK tyrosine kinase is associated with human glioma growth

PURPOSE

Glioma is a highly aggressive and lethal brain tumor. Signal transducers and activators of transcription (STAT) pathway are widely implicated in glioma carcinogenesis. Our previous study found that the Fynrelated kinase (FRK) gene, plays as a tumor suppressor in the development and progression of glioma. This study aimed to investigate the role of FRK in the activation pathway of STATs and its effect on the growth of glioma.

METHODS

The U251 and U87 cells with stable FRK overexpression were generated by lentivirus technique. The effects of FRK on the related proteins of STAT signaling pathway were detected by western blotting. Coimmunoprecipitation was used to detect the association of FRK and STAT1. The effects of STAT1 on the proliferation of glioma cells were detected by CCK8 or Edu cell proliferation assays. The expressions and correlation of FRK and p-STAT1 in glioma tissues were detectd by western blotting or immunohistochemistry. The effect of FRK on the growth of glioma was investigated in vivo mouse model.

RESULTS

The level of p-JAK2 and p-STAT1 increased after FRK overexpression, while they decreased after FRK downregulation both in U251 and U87 cells. However, FRK had no effect on STAT3 phosphorylation. FRK-induced STAT1 activation was not dependent on JAK2. FRK associated with STAT1, induced STAT1 nuclear translocation and regulated the expressions of STAT1-related target genes. STAT1 overexpression suppressed the proliferation of glioma cells. In contrast, STAT1 knockdown by siRNA promoted glioma cell growth. Importantly, down-regulation of STAT1 partially attenuated FRK-induced growth suppression. The clinical sample-based study indicated that the expression of FRK was significantly correlated with the expression of p-STAT1. FRK significantly inhibited glioma tumor growth in vivo.

CONCLUSIONS

Our findings highlighted a critical role of FRK in tumor suppression ability through promoting STAT1 activation, and provided a potential therapeutic target for glioma.

Upregulation of DNA Metabolism-Related Genes Contributes to Radioresistance of Glioblastoma

Glioblastomas (GBMs) are the most prevalent brain tumor and exhibit poor prognosis. Radiotherapy is an important strategy for GBMs patients; however, this care remains palliative because of GBMs' radioresistance. Glioma stem cells (GSCs), as a subpopulation residing at the apex of the hierarchy, have been believed to be a pivotal population in radioresistance and recurrence of GBMs. To know the key genes involved in radioresistance of GSCs, the gene expression profiles of GSE54660 and GSE60921 were downloaded from Gene Expression Omnibus for genetic and transcriptomic analysis to identify the potential biomarker genes differentially expressed between GSCs and GBMs. These candidate genes were then filtered by the GSCs gene profile responding to radiation and the radioresistant biomarker genes including DNAJC9, GINS2, STAT1, CHAC2, MT1M, and ZNF226 were screened. The differentially expressed genes in GSCs post-irradiation were submitted to Gene Ontology (GO) for further enrichment analysis and protein-protein interaction (PPI) network analysis. A significant module correlated with GINS2 was finally chosen and a series of genes participating in DNA metabolism were identified. In conclusion, this study propounds a set of novel genes that are differentially expressed in the radioresistant subpopulation within GBMs and could serve as promising therapeutic targets.

Overexpression of STAT1 suppresses angiogenesis under hypoxia by regulating VEGF‑A in human glioma cells

Hypoxia is common in Glioblastoma (GBM). By regulating the 'hypoxia signaling cascade', hypoxia affects several processes including cell proliferation, invasion, and angiogenesis. Some studies have revealed that signal transducer and activator of transcription (STAT), including STAT1, is abnormal under hypoxia in several cancers. Here, we investigated the role of STAT1 under hypoxia in glioma progression. We found that STAT1 was downregulated under a hypoxic condition in U251 and U373. STAT1 overexpression can not only decrease proliferation, migration and invasion in U251 and U373 but also inhibit tube formation of HBMECs. Moreover, overexpression of STAT1 decreased tumor growth and prolonged the overall survival of xenograft mice. We also showed that STAT1 overexpression inhibited the expression of HIF-1α and VEGF-A. Our work suggests that STAT1 plays a pivotal role as a tumor suppressor in glioma under hypoxia, and it could be a potential new therapeutic target in glioma.

Brain-derived neurotrophic factor propeptide inhibits proliferation and induces apoptosis in C6 glioma cells

There are several forms of brain-derived neurotrophic factor (BDNF), the precursor of BDNF, mature BDNF, and BDNF propeptide. They exert different effects through different transmembrane receptor signaling systems. Precursor of BDNF is enzymatically cleaved, either by intracellular or by extracellular proteases, to generate mature BDNF and its propeptide (BDNF propeptide). The aim of this study was to evaluate the potential molecular mechanisms that underlie the inhibition of glioma cell growth by the BDNF propeptide. To achieve this, we examined the expression of BDNF propeptide in C6 glioma cells. The 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide assay and the apoptosis assay were used to assess the effects of the BDNF propeptide on the growth and apoptosis of glioma cells. We found that the BDNF propeptide promoted C6 glioma cell apoptosis and decreased in-vitro cell growth. We also found using western blot that cleaved caspase3 and B cell lymphoma 2 (Bcl2)-associated X protein abundances increased, whereas Bcl2 abundance decreased. Our data suggest that the BDNF propeptide may have an inhibitory effect on glioma through activation of the caspase3 pathway.

A study on the correlation between STAT‑1 and mutant p53 expression in glioma

Glioma is the most common primary brain tumor in adults and the second most common malignant tumor in children. Aberrant expression of signal transducer and activator of transcription 1 (STAT‑1) and p53 are known to affect the occurrence and progression of malignant tumors. The aim of the present study was to investigate the expression of STAT‑1 and mutant p53 gene, as well as their correlation, in patients with glioma. The present study included 50 patients who underwent glioma resection at the First Affiliated Hospital of Inner Mongolia Medical University between December 2007 and December 2011, and 10 patients with acute cerebral contusion who underwent intracerebral hematoma removal at the same hospital between January 2013 and January 2014. The expression of STAT‑1 and mutant p53 protein in patients with different grades of glioma was assessed by immunohistochemistry. Spearman's correlation coefficient was employed to examine the correlation between STAT‑1 and the grade of glioma, and mutant p53 expression. The results demonstrated that the mean expression of STAT‑1 in glioma was significantly lower compared with normal brain tissue (P<0.05). However, there was no significant difference in the STAT‑1 positive expression rate between the two groups (χ2=1.38, P>0.05). The expression score (P<0.05) and positive expression rate (χ2=31.27, P<0.05) of mutant p53 in glioma was significantly higher compared with those in normal brain tissue. Statistical analysis revealed a negative correlation between STAT‑1 expression and the grade of glioma (r=‑0.767, P<0.05). In addition, mutant p53 expression was negatively correlated with STAT‑1 expression in glioma (r=‑0.876, P<0.05). The observed negative correlation between STAT‑1 and the pathological grade of glioma suggested an association between STAT‑1 and the occurrence and development of glioma, thus revealing the potential of STAT‑1 as a diagnostic biomarker and therapeutic target for glioma.

The function of BTG3 in colorectal cancer cells and its possible signaling pathway

PURPOSE

B-cell translocation gene 3 (BTG3) has been identified as a candidate driver gene for various cancers, but its specific role in colorectal cancer (CRC) is poorly understood. We aimed to investigate the relationship between expression of BTG3 and clinicopathological features and prognosis, as well as to explore the effects and the role of a possible BTG3 molecular mechanism on aggressive colorectal cancer behavior.

METHODS

BTG3 expression was assessed by immunohistochemistry (IHC) on specimens from 140 patients with CRC. The association of BTG3 expression with clinicopathological features was examined. To confirm the biological role of BTG3 in CRC, two CRC cell lines expressing BTG3 were used and BTG3 expression was knocked down by shRNA. CCK-8, cell cycle, apoptosis, migration, and invasion assays were performed. The influence of BTG3 knockdown was further investigated by genomic microarray to uncover the potential molecular mechanisms underlying BTG3-mediated CRC development and progression.

RESULTS

BTG3 was downregulated in colorectal cancer tissues and positively correlated with pathological classification (p = 0.037), depth of invasion (p = 0.016), distant metastasis (p = 0.024), TNM stage (p = 0.007), and overall survival (OS) and disease-free survival (DFS). BTG3 knockdown promoted cell proliferation, migration, invasion, relieved G2 arrest, and inhibited apoptosis in HCT116 and LoVo cells. A genomic microarray analysis showed that numerous tumor-associated signaling pathways and oncogenes were altered by BTG3 knockdown. At the mRNA level, nine genes referred to the extracellular-regulated kinase/mitogen-activated protein kinase pathway were differentially expressed. Western blotting revealed that BTG3 knockdown upregulated PAK2, RPS6KA5, YWHAB, and signal transducer and activator of transcription (STAT)3 protein levels, but downregulated RAP1A, DUSP6, and STAT1 protein expression, which was consistent with the genomic microarray data.

CONCLUSIONS

BTG3 expression might contribute to CRC carcinogenesis. BTG3 knockdown might strengthen the aggressive colorectal cancer behavior.

Silence of MACC1 expression by RNA interference inhibits proliferation, invasion and metastasis, and promotes apoptosis in U251 human malignant glioma cells

The overexpression of metastasis-associated in colon cancer 1 (MACC1) has been demonstrated not only in colon cancer, but also in various other types of cancer. Gliomas are the most common type of intracranial tumors, and recent studies have reported MACC1 to be involved in human glioma progression. The present study aimed to investigate the effects of MACC1 expression silencing in glioma cells using RNA interference, in order to determine the underlying biological mechanisms of glioma progression, including proliferation, apoptosis, invasion and metastasis. The expression levels of MACC1 were determined in various types of U251 glioma cells using western blot analyses. MACC1-specific short hairpin RNA (shRNA) was used to silence the expression of MACC1 in the U251 cells. The results obtained following MACC1 silencing demonstrated a significant inhibition of cell proliferation, invasion and migration, as well as a marked enhancement of apoptosis. MACC1 shRNA-induced inhibition of cell proliferation was observed by colony forming and MTT assays, and cell apoptosis was measured using flow cytometry and Hoechst staining. In addition, inhibition of cell invasion and migration was assessed using wound healing and transwell assays. Western blotting and fluorescence-activated cell sorting (FACS) revealed a G₀/G₁ phase cell cycle arrest regulated by cyclins D1 and E; cell apoptosis regulated by caspase-3; and cell invasion and migration regulated by matrix metalloproteinases 2 and 9, respectively. The present study demonstrated that the expression levels of MACC1 were significantly correlated with the biological processes underlying glioma cell proliferation, invasion and metastasis. Therefore, MACC1 may serve as a promising novel therapeutic target in human glioma. Notably, the inhibition of MACC1 expression by shRNA may prove to be an effective genetic therapeutic strategy for glioma treatment.

STAT-1 expression is regulated by IGFBP-3 in malignant glioma cells and is a strong predictor of poor survival in patients with glioblastoma

OBJECT

Insulin-like growth factor binding proteins (IGFBPs) have been implicated in the pathogenesis of glioma. In a previous study the authors demonstrated that IGFBP-3 is a novel glioblastoma biomarker associated with poor survival. Since signal transducer and activator of transcription 1 (STAT-1) has been shown to be regulated by IGFBP-3 during chondrogenesis and is a prosurvival and radioresistant molecule in different tumors, the aim in the present study was to explore the functional significance of IGFBP-3 in malignant glioma cells, to determine if STAT-1 is indeed regulated by IGFBP-3, and to study the potential of STAT-1 as a biomarker in glioblastoma.

METHODS

The functional significance of IGFBP-3 was investigated using the short hairpin (sh)RNA gene knockdown approach on U251MG cells. STAT-1 regulation by IGFBP-3 was tested on U251MG and U87MG cells by shRNA gene knockdown and exogenous treatment with recombinant IGFBP-3 protein. Subsequently, the expression of STAT-1 was analyzed with real-time reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) in glioblastoma and control brain tissues. Survival analyses were done on a uniformly treated prospective cohort of adults with newly diagnosed glioblastoma (136 patients) using Kaplan-Meier and Cox regression models.

RESULTS

IGFBP-3 knockdown significantly impaired proliferation, motility, migration, and invasive capacity of U251MG cells in vitro (p < 0.005). Exogenous overexpression of IGFBP-3 in U251MG and U87MG cells demonstrated STAT-1 regulation. The mean transcript levels (by real-time RT-PCR) and the mean labeling index of STAT-1 (by IHC) were significantly higher in glioblastoma than in control brain tissues (p = 0.0239 and p < 0.001, respectively). Multivariate survival analysis revealed that STAT-1 protein expression (HR 1.015, p = 0.033, 95% CI 1.001-1.029) along with patient age (HR 1.025, p = 0.005, 95% CI 1.008-1.042) were significant predictors of shorter survival in patients with glioblastoma.

CONCLUSIONS

IGFBP-3 influences tumor cell proliferation, migration, and invasion and regulates STAT-1 expression in malignant glioma cells. STAT-1 is overexpressed in human glioblastoma tissues and emerges as a novel prognostic biomarker.