Doxorubicin-mediated apoptosis in glioma cells requires NFAT3

Recent knowledge of NFATc4 in oncogenesis and cancer prognosis

Nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4), a transcription factor of NFAT family, which is activated by Ca²⁺/calcineurin signaling. Recently, it is reported that aberrantly activated NFATc4 participated and modulated in the initiation, proliferation, invasion, and metastasis of various cancers (including cancers of the lung, breast, ovary, cervix, skin, liver, pancreas, as well as glioma, primary myelofibrosis and acute myelocytic leukemia). In this review, we cover the latest knowledge on NFATc4 expression pattern, post-translational modification, epigenetic regulation, transcriptional activity regulation and its downstream targets. Furthermore, we perform database analysis to reveal the prognostic value of NFATc4 in various cancers and discuss the current unexplored areas of NFATc4 research. All in all, the result from these studies strongly suggest that NFATc4 has the potential as a molecular therapeutic target in multiple human cancer types.

Expression, Prognosis and Gene Regulation Network of NFAT Transcription Factors in Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide. The nuclear factor of activated T cells (NFAT) family is implicated in tumorigenesis and progression in various types of cancer. However, little is known about their expression patterns, distinct prognostic values, and potential regulatory networks in NSCLC. In this study, we comprehensively analyzed the distinct expression and prognostic value of NFATs in NSCLC through various large databases, including the Oncomine, UCSC Xena Browser, UALCAN databases, Kaplan–Meier Plotter, cBioPortal, and Enrichr. In lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), NFAT1/2/4/5 mRNA expression levels were significantly decreased and NFAT3 mRNA expression level was significantly increased. The cBioPortal database analysis showed that the mRNA dysregulation was one of the single most important factors for NFAT alteration in LUAD and LUSC and that both LUAD and LUSC cases with the alterations in the mRNA expression of NFATs had significantly better overall survival (OS). High expression levels of NFAT1/2/4/5 were significantly associated with better OS in LUAD, whereas high NFAT3 expression led to a worse OS. Overexpression of NFAT1/2 predicted better OS in LUSC, whereas high NFAT5 expression led to a worse OS. The networks for NFATs and the 50 most frequently altered neighbor genes in LUAD and LUSC were also constructed. NFATs and genes significantly associated with NFAT mRNA expression in LUAD and LUSC were significantly enriched in the cGMP-dependent protein kinase and Wnt signaling pathways. These results showed that the NFAT family members displayed varying degrees of abnormal expressions, suggesting that NFATs may be therapeutic targets for patients with NSCLC. Aberrant expression of NFATs was found to be associated with OS in the patients with NSCLC; among NFATs, NFAT3/4 may be new biomarkers for the prognosis of LUAD. However, further studies are required to validate our findings.

Specific Compositions of Cannabis sativa Compounds Have Cytotoxic Activity and Inhibit Motility and Colony Formation of Human Glioblastoma Cells In Vitro

Glioblastoma multiforme (GBM) is the most lethal subtype of glioma. Cannabis sativa is used for the treatment of various medical conditions. Around 150 phytocannabinoids have been identified in C. sativa, among them Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) that trigger GBM cell death. However, the optimal combinations of cannabis molecules for anti-GBM activity are unknown. Chemical composition was determined using high-performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC/MS). Cytotoxic activity was determined by XTT and lactate dehydrogenase (LDH) assays and apoptosis and cell cycle by fluorescence-activated cell sorting (FACS). F-actin structures were observed by confocal microscopy, gene expression by quantitative PCR, and cell migration and invasion by scratch and transwell assays, respectively. Fractions of a high-THC cannabis strain extract had significant cytotoxic activity against GBM cell lines and glioma stem cells derived from tumor specimens. A standard mix (SM) of the active fractions F4 and F5 induced apoptosis and expression of endoplasmic reticulum (ER)-stress associated-genes. F4 and F5 inhibited cell migration and invasion, altered cell cytoskeletons, and inhibited colony formation in 2 and 3-dimensional models. Combinations of cannabis compounds exert cytotoxic, anti-proliferative, and anti-migratory effects and should be examined for efficacy on GBM in pre-clinical studies and clinical trials.

The effect of low doses of doxorubicin on the rat glioma C6 cells in the context of the proteins involved in intercellular interactions

The aim of this investigation was to determine the effect of doxorubicin on F-actin rearrangement and β-catenin and cofilin-1 in a rat glioma C6 cell line in combination with changes in their morphology and ultrastructure. The experimental material constituted rat glioma C6 cell line. The cells were incubated with sublethal doses of doxorubicin in the concentration of 50, 100 and 200 nM. The blue trypan dye method was used to determine the number of dead cells. Morphological and ultrastructural changes in the cells were evaluated using light and transmission electron microscope, respectively. In order to determine the rearrangements and level of expression of F-actin, β-catenin and cofilin-1 they were analyzed using a fluorecence microscope. In turn, cell death and cell cycle were evaluated by Guava 6HT-2 L Cytometer. The performed experiments showed a dose-dependent decrease in the survival of C6 cells after treatment with doxorubicin. The analysis of cell death showed a dose-dependent increase in the population of apoptotic and necrotic cells. These results were confirmed by microscopy observation. The changes in morphology, ultrastructure, and rearrangements of F-actin, β-catenin and cofilin-1 were also observed. The results obtained in the study showed that sublethal concentrations of doxorubicin influenced the structure of F-actin and other proteins involved in cell-cell interactions. Moreover, mitotic catastrophe may preceding apoptosis, what suggest the cytotoxic effect of low dose of doxorubicin. Furthermore, our results confirmed the multi-dimensional mechanism of DOX action in tumor cells.

Tacrolimus and ascomycin inhibit melanoma cell growth, migration and invasion via targeting nuclear factor of activated T-cell 3

Melanoma is the most malignant form of skin cancer with high metastatic potential. Nuclear factor of activated T-cells (NFATs) are discovered as transcription factors that regulate the expression of proinflammatory cytokines and other genes during the immune response. Among five NFAT members, NFAT3 is exclusively not expressed in immune cells and its role in progression of different types of cancer remains controversial. Our previous study showed that NFAT3 was highly expressed in skin cancer compared with normal skin tissues and critical for melanoma cell survival and tumor growth. Here, we reported that knockdown of NFAT3 expression, as well as treatment with the calcineurin (CaN) inhibitors, tacrolimus (FK506) or ascomycin (FK520) inhibits melanoma cell migration and invasion, and also proliferation and colony formation. Mechanistic studies revealed that FK506 or FK520 blocked the nuclear translocation and reduced the transcriptional activity of NFAT3. These data support that the antimelanoma effect of FK506 and FK520 is partially mediated by inhibiting the oncogenic factor NFAT3, suggesting that therapeutics based on NFAT3 inhibition may be effective in clinical melanoma treatment.

NFATC4 promotes quiescence and chemotherapy resistance in ovarian cancer

Development of chemotherapy resistance is a major problem in ovarian cancer. One understudied mechanism of chemoresistance is the induction of quiescence, a reversible nonproliferative state. Unfortunately, little is known about regulators of quiescence. Here, we identify the master transcription factor nuclear factor of activated T cells cytoplasmic 4 (NFATC4) as a regulator of quiescence in ovarian cancer. NFATC4 is enriched in ovarian cancer stem-like cells and correlates with decreased proliferation and poor prognosis. Treatment of cancer cells with cisplatin resulted in NFATC4 nuclear translocation and activation of the NFATC4 pathway, while inhibition of the pathway increased chemotherapy response. Induction of NFATC4 activity resulted in a marked decrease in proliferation, G0 cell cycle arrest, and chemotherapy resistance, both in vitro and in vivo. Finally, NFATC4 drove a quiescent phenotype in part via downregulation of MYC. Together, these data identify NFATC4 as a driver of quiescence and a potential new target to combat chemoresistance in ovarian cancer.

Nfatc4 Deficiency Attenuates Ototoxicity by Suppressing Tnf-Mediated Hair Cell Apoptosis in the Mouse Cochlea

The loss of sensory hair cells in the cochlea is the major cause of sensorineural hearing loss, and inflammatory processes and immune factors in response to cochlear damage have been shown to induce hair cell apoptosis. The expression and function of Nfatc4 in the cochlea remains unclear. In this study, we investigated the expression of Nfatc4 in the mouse cochlea and explored its function using Nfatc4^−/− mice. We first showed that Nfatc4 was expressed in the cochlear hair cells. Cochlear hair cell development and hearing function were normal in Nfatc4^−/− mice, suggesting that Nfatc4 is not critical for cochlear development. We then showed that when the hair cells were challenged by ototoxic drugs Nfatc4 was activated and translocated from the cytoplasm to the nucleus, and this was accompanied by increased expression of Tnf and its downstream targets and subsequent hair cell apoptosis. Finally, we demonstrated that Nfatc4-deficient hair cells showed lower sensitivity to damage induced by ototoxic drugs and noise exposure compared to wild type controls. The Tnf-mediated apoptosis pathway was attenuated in Nfatc4-deficient cochlear epithelium, and this might be the reason for the reduced sensitivity of Nfatc4-deficient hair cells to injury. These findings suggest that the amelioration of inflammation-mediated hair cell apoptosis by inhibition of Nfatc4 activation might have significant therapeutic value in preventing ototoxic drug or noise exposure-induced sensorineural hearing loss.

Prophylactic supplementation of resveratrol is more effective than its therapeutic use against doxorubicin induced cardiotoxicity

Resveratrol (RSV), a polyphenolic compound and naturally occurring phytoalexin, has been reported to exert cardio-protective effects in several animal studies. However, the outcome of initial clinical trials with RSV was less effective compared to pre-clinical studies. Therefore, RSV treatment protocols need to be optimized. In this study we evaluated prophylactic versus therapeutic effect of resveratrol (RSV) in mitigating doxorubicin (Dox)-induced cardiac toxicity in rats. To investigate prophylactic effects, RSV was supplemented for 2 weeks along with Dox administration. After 2 weeks, Dox treatment was stopped and RSV was continued for another 4 weeks. To study therapeutic effects, RSV treatment was initiated after 2 weeks of Dox administration and continued for 4 weeks. Both prophylactic and therapeutic use of RSV mitigated Dox induced deterioration of cardiac function as assessed by echocardiography. Also RSV treatment (prophylactic and therapeutic) prevented Dox induced myocardial damage as measured by cardiac enzymes (LDH and CK-MB) in serum. Which was associated with decrease in Dox induced myocardial apoptosis and fibrosis. Interestingly our study also reveals that prophylactic use of RSV was more effective than its therapeutic use in mitigating Dox induced apoptosis and fibrosis in the myocardium. Therefore, prophylactic use of resveratrol may be projected as a possible future adjuvant therapy to minimize cardiotoxic side effects of doxorubicin in cancer patients.

DT(270-326) , a Truncated Diphtheria Toxin, Increases Blood-Tumor Barrier Permeability by Upregulating the Expression of Caveolin-1

AIM

The nontoxic mutant of diphtheria toxin (DT) has been demonstrated to act as a receptor-specific carrier protein to delivery drug into brain. Recent research showed that the truncated "receptorless" DT was still capable of being internalized into cells. This study investigated the effects and potential mechanisms of DT(270-326) , a truncated "receptorless" DT, on the permeability of the blood-tumor barrier (BTB).

METHODS

BTB and GECs were subjected to DT(270-326) treatment. HRP flux assays, immunofluorescent, co-immunoprecipitation, Western blot, CCK-8, and Flow cytometry analysis were used to evaluate the effects of DT(270-326) administration.

RESULTS

Our results revealed that 5 μM of DT(270-326) significantly increased the permeability of BTBin vitro, which reached its peak at 6 h. The permeability was reduced by pretreatment with filipinIII. DT(270-326) co-localized and interacted with caveolin-1 via its caveolin-binding motif. The mRNA and protein expression levels of caveolin-1 were identical with the changes of BTB permeability. The upregulated expression of caveolin-1 was associated with Src kinase-dependent tyrosine phosphorylation of caveolin-1, which subsequently induced phosphorylation and inactivation of the transcription factor Egr-1. The combination of DT(270-326) with doxorubicin significantly enhanced the loss of cell viability and apoptosis of U87 glioma cells in contrast to doxorubicin alone.

CONCLUSIONS

DT(270-326) might provide a novel strategy to increase the delivery of macromolecular therapeutic agents across the BTB.

Cytotoxicity and apoptotic gene expression in an in vitro model of the blood-brain barrier following exposure to poly(butylcyanoacrylate) nanoparticles

Background Poly(butylcyanoacrylate) (PBCA) nanoparticles (NPs) loaded with doxorubicin (DOX) and coated with polysorbate 80 (PS80) have shown efficacy in the treatment of rat glioblastoma. However, cytotoxicity of this treatment remains unclear. Purpose The purpose of this study was to investigate cytotoxicity and apoptotic gene expression using a proven in vitro co-culture model of the blood-brain barrier. Methods The co-cultures were exposed to uncoated PBCA NPs, PBCA-PS80 NPs or PBCA-PS80-DOX NPs at varying concentrations and evaluated using a resazurin-based cytotoxicity assay and an 84-gene apoptosis RT-PCR array. Results The cytotoxicity assays showed PBCA-PS80-DOX NPs exhibited a decrease in metabolic function at lower concentrations than uncoated PBCA NPs and PBCA-PS80 NPs. The apoptosis arrays showed differential expression of 18 genes in PBCA-PS80-DOX treated cells compared to the untreated control. Discussion As expected, the cytotoxicity assays demonstrated enhanced dose-dependent toxicity in the DOX loaded NPs. The differentially expressed apoptotic genes participate in both the tumor necrosis factor receptor-1 and mitochondria-associated apoptotic pathways implicated in current DOX chemotherapeutic toxicity. Conclusion The following data suggest that the cytotoxic effect may be attributed to DOX and not the NPs themselves, further supporting the use of PBCA-PS80 NPs as an effective drug delivery vehicle for treating central nervous system conditions.

Nuclear factor of activated T cells in cancer development and treatment

Since nuclear factor of activated T cells (NFAT) was first identified as a transcription factor in T cells, various NFAT isoforms have been discovered and investigated. Accumulating studies have suggested that NFATs are involved in many aspects of cancer, including carcinogenesis, cancer cell proliferation, metastasis, drug resistance and tumor microenvironment. Different NFAT isoforms have distinct functions in different cancers. The exact function of NFAT in cancer or the tumor microenvironment is context dependent. In this review, we summarize our current knowledge of NFAT regulation and function in cancer development and treatment. NFATs have emerged as a potential target for cancer prevention and therapy.

Altered expression of long non-coding RNAs during genotoxic stress-induced cell death in human glioma cells

Long non-coding RNAs (lncRNAs), a recently discovered class of non-coding genes, are transcribed throughout the genome. Emerging evidence suggests that lncRNAs may be involved in modulating various aspects of tumor biology, including regulating gene activity in response to external stimuli or DNA damage. No data are available regarding the expression of lncRNAs during genotoxic stress-induced apoptosis and/or necrosis in human glioma cells. In this study, we detected a change in the expression of specific candidate lncRNAs (neat1, GAS5, TUG1, BC200, Malat1, MEG3, MIR155HG, PAR5, and ST7OT1) during DNA damage-induced apoptosis in human glioma cell lines (U251 and U87) using doxorubicin (DOX) and resveratrol (RES). We also detected the expression pattern of these lncRNAs in human glioma cell lines under necrosis induced using an increased dose of DOX. Our results reveal that the lncRNA expression patterns are distinct between genotoxic stress-induced apoptosis and necrosis in human glioma cells. The sets of lncRNA expressed during genotoxic stress-induced apoptosis were DNA-damaging agent-specific. Generally, MEG3 and ST7OT1 are up-regulated in both cell lines under apoptosis induced using both agents. The induction of GAS5 is only clearly detected during DOX-induced apoptosis, whereas the up-regulation of neat1 and MIR155HG is only found during RES-induced apoptosis in both cell lines. However, TUG1, BC200 and MIR155HG are down regulated when necrosis is induced using a high dose of DOX in both cell lines. In conclusion, our findings suggest that the distinct regulation of lncRNAs may possibly involve in the process of cellular defense against genotoxic agents.

Loss of PDCD4 contributes to enhanced chemoresistance in Glioblastoma multiforme through de-repression of Bcl-xL translation

Glioblastoma multiforme (GBM) is the most common and aggressive form of tumor of the central nervous system. Despite significant efforts to improve treatments, patient survival rarely exceeds 18 months largely due to the highly chemoresistant nature of these tumors. Importantly, misregulation of the apoptotic machinery plays a key role in the development of drug resistance. We previously demonstrated that Bcl-xL, an important anti-apoptotic protein, is regulated at the level of translation by the tumor suppressor programmed cell death 4 (PDCD4). We report here a strong correlation between low expression of PDCD4 and high expression of Bcl-xL in adult de novo GBM, GBM tumor initiating cells, and established GBM cell lines. Importantly, high Bcl-xL expression correlated significantly with poor progression and patient survival. We demonstrate that re-expression of PDCD4 in GBM cells down-regulated Bcl-xL expression and decreased cell viability. Finally, we show that direct inhibition of Bcl-xL by small molecule antagonist ABT-737 sensitizes GBM cells to doxorubicin. Our results identify Bcl-xL as a novel marker of GBM chemoresistance and advocate for the combined use of Bcl-xL antagonists and existing chemotherapeutics as a treatment option for this aggressive tumor.

Role of methamphetamine on glioblastoma cytotoxicity induced by doxorubicin and methotrexate

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor with a high mortality rate. Doxorubicin (DOX) and methotrexate (MTX) showed to be effective against a wide range of tumors, but its use in GBM treatment is limited in part due to the inability to cross the blood-brain barrier (BBB). Based on recent studies demonstrating that methamphetamine (METH) increases BBB permeability, we hypothesized that it could be used as a pharmacological tool to allow the entry of potential therapeutic drugs into the brain. Nevertheless, before attempting this approach it is crucial to understand the cytotoxicity of such drug combinations. Herein, we evaluated the effects of METH on cell viability, migration, chemotaxis, and cell cycle, as well as its modulator effects on DOX or MTX-induced cytotoxicity in a human U118 GBM cell line. Our results demonstrated that both chemotherapeutic drugs DOX and MTX induced a pronounced decrease in cell viability, migration, and chemotaxis, and led to a cell cycle arrest at G2 and S phases, respectively. Additionally, METH (1 μM) neither interfered with U-118 cell viability, migration, or cell cycle nor modified DOX- or MTX-induced cytotoxicity. Noteworthy, METH by itself impaired cell chemotaxis with a similar effect to that induced by DOX or MTX alone. Overall, we can conclude that both DOX and MTX are highly cytotoxic against GBM cells and that METH, at a concentration previously shown to increase endothelial cell permeability without leading to cell death, does not interfere with the cytotoxicity of both chemotherapeutic drugs.

PMA and ionomycin induce glioblastoma cell death: activation-induced cell-death-like phenomena occur in glioma cells

Phorbol myristate acetate (PMA) and ionomycin (Io) can induce T cell activation and proliferation. Furthermore, they stimulate activation-induced cell death (AICD) in mature lymphocytes via Fas/Fas ligand (FasL) up-regulation. In this study, we explored the influence of PMA/Io treatment on glioblastoma cells, and found that AICD-like phenomena may also occur in glioma. Using the MTT assay and cell counting, we demonstrated that treatment of PMA/Io significantly inhibited the proliferation of glioma cell lines, U87 and U251. TUNEL assays and transmission electron microscopy revealed that PMA/Io markedly induced U87 and U251 cell apoptosis. Propidium iodide staining and flow cytometry showed that treatment with PMA/Io resulted in an arrestment of cell cycle and an increase in cell death. Using real-time PCR and western blot, we found that PMA/Io up-regulated the expression of Fas and FasL at both mRNA and protein level, which confirmed that PMA/Io induced glioma cell death. Specific knockdown of NFAT1 expression by small hairpin RNA greatly reduced the PMA/Io induced cell death and apoptosis by inhibition of FasL expression. Microarray analysis showed that the expression of NFAT1 significantly correlated with the expression of Fas. The coexistence of Fas with NFAT1 in vivo provides the background for AICD-like phenomena to occur in glioma. These findings demonstrate that PMA/Io can induce glioblastoma cell death through the NFAT1-Fas/FasL pathway. Glioma-related AICD-like phenomena may provide a novel avenue for glioma treatment.

Regulator of G protein signaling 6 mediates doxorubicin-induced ATM and p53 activation by a reactive oxygen species-dependent mechanism

Doxorubicin (DXR), among the most widely used cancer chemotherapy agents, promotes cancer cell death via activation of ataxia telangiectasia mutated (ATM) and the resultant upregulation of tumor suppressor p53. The exact mechanism by which DXR activates ATM is not fully understood. Here, we discovered a novel role for regulator of G protein signaling 6 (RGS6) in mediating activation of ATM and p53 by DXR. RGS6 was robustly induced by DXR, and genetic loss of RGS6 dramatically impaired DXR-induced activation of ATM and p53, as well as its in vivo apoptotic actions in heart. The ability of RGS6 to promote p53 activation in response to DXR was independent of RGS6 interaction with G proteins but required ATM. RGS6 mediated activation of ATM and p53 by DXR via a reactive oxygen species (ROS)-dependent and DNA damage-independent mechanism. This mechanism represents the primary means by which DXR promotes activation of the ATM-p53 apoptosis pathway that underlies its cytotoxic activity. Our findings contradict the canonical theories that DXR activates ATM primarily by promoting DNA damage either directly or indirectly (via ROS) and that RGS6 function is mediated by its interactions with G proteins. These findings reveal a new mechanism for the chemotherapeutic actions of DXR and identify RGS6 as a novel target for cancer chemotherapy.

Downregulation of uPAR and cathepsin B induces apoptosis via regulation of Bcl-2 and Bax and inhibition of the PI3K/Akt pathway in gliomas

BACKGROUND

Glioma is the most commonly diagnosed primary brain tumor and is characterized by invasive and infiltrative behavior. uPAR and cathepsin B are known to be overexpressed in high-grade gliomas and are strongly correlated with invasive cancer phenotypes.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, we observed that simultaneous downregulation of uPAR and cathepsin B induces upregulation of some pro-apoptotic genes and suppression of anti-apoptotic genes in human glioma cells. uPAR and cathepsin B (pCU)-downregulated cells exhibited decreases in the Bcl-2/Bax ratio and initiated the collapse of mitochondrial membrane potential. We also observed that the broad caspase inhibitor, Z-Asp-2, 6-dichlorobenzoylmethylketone rescued pCU-induced apoptosis in U251 cells but not in 5310 cells. Immunoblot analysis of caspase-9 immunoprecipitates for Apaf-1 showed that uPAR and cathepsin B knockdown activated apoptosome complex formation in U251 cells. Downregulation of uPAR and cathepsin B also retarded nuclear translocation and interfered with DNA binding activity of CREB in both U251 and 5310 cells. Further western blotting analysis demonstrated that downregulation of uPAR and cathepsin B significantly decreased expression of the signaling molecules p-PDGFR-β, p-PI3K and p-Akt. An increase in the number of TUNEL-positive cells, increased Bax expression, and decreased Bcl-2 expression in nude mice brain tumor sections and brain tissue lysates confirm our in vitro results.

CONCLUSIONS/SIGNIFICANCE

In conclusion, RNAi-mediated downregulation of uPAR and cathepsin B initiates caspase-dependent mitochondrial apoptosis in U251 cells and caspase-independent mitochondrial apoptosis in 5310 cells. Thus, targeting uPAR and cathepsin B-mediated signaling using siRNA may serve as a novel therapeutic strategy for the treatment of gliomas.