Tamoxifen improves cytopathic effect of oncolytic adenovirus in primary glioblastoma cells mediated through autophagy

Autophagy inhibition is the next step in the treatment of glioblastoma patients following the Stupp era

It has now been nearly 15 years since the last major advance in the treatment of patients with glioma. "The addition of temozolomide to radiotherapy for newly diagnosed glioblastoma resulted in a clinically meaningful and statistically significant survival benefit with minimal additional toxicity". Autophagy is primarily a survival pathway, literally self-eating, that is utilized in response to stress (such as radiation and chemotherapy), enabling clearance of effete protein aggregates and multimolecular assemblies. Promising results have been observed in patients with glioma for over a decade now when autophagy inhibition with chloroquine derivatives coupled with conventional therapy. The application of autophagy inhibitors, the role of immune cell-induced autophagy, and the potential role of novel cellular and gene therapies, should now be considered for development as part of this well-established regimen.

Metabolome-Driven Regulation of Adenovirus-Induced Cell Death

A viral infection that involves virus invasion, protein synthesis, and virion assembly is typically accompanied by sharp fluctuations in the intracellular levels of metabolites. Under certain conditions, dramatic metabolic shifts can result in various types of cell death. Here, we review different types of adenovirus-induced cell death associated with changes in metabolic profiles of the infected cells. As evidenced by experimental data, in most cases changes in the metabolome precede cell death rather than represent its consequence. In our previous study, the induction of autophagic cell death was observed following adenovirus-mediated lactate production, acetyl-CoA accumulation, and ATP release, while apoptosis was demonstrated to be modulated by alterations in acetate and asparagine metabolism. On the other hand, adenovirus-induced ROS production and ATP depletion were demonstrated to play a significant role in the process of necrotic cell death. Interestingly, the accumulation of ceramide compounds was found to contribute to the induction of all the three types of cell death mentioned above. Eventually, the characterization of metabolite analysis could help in uncovering the molecular mechanism of adenovirus-mediated cell death induction and contribute to the development of efficacious oncolytic adenoviral vectors.

TMZ regulates GBM stemness via MMP14-DLL4-Notch3 pathway

Glioblastoma (GBM) is one of the most aggressive primary brain tumors with frequent recurrences following the standard methods of treatment-temozolomide (TMZ), ionizing radiation and surgical resection. The objective of our study was to investigate GBM resistance mediated via MMP14 (matrix metalloproteinase 14). We used multiple PDX GBM models and established glioma cell lines to characterize expression and subcellular localization of MMP14 after TMZ treatment. We performed a Kiloplex ELISA-based array to evaluate changes in cellular proteins induced by MMP14 expression and translocation. Lastly, we conducted functional and mechanistic studies to elucidate the role of DLL4 (delta-like canonical notch ligand 4) in regulation of glioma stemness, particularly in the context of its relationship to MMP14. We detected that TMZ treatment promotes nuclear translocation of MMP14 followed by extracellular release of DLL4. DLL4 in turn stimulates cleavage of Notch3, its nuclear translocation and induction of sphering capacity and stemness.

Estrogen receptor variant ER-α36 promotes tamoxifen agonist activity in glioblastoma cells

Glioblastoma (GBM) is a highly infiltrative and malignant primary brain tumor. Despite aggressive therapy, patients with GBM have a dismal prognosis with median survival of approximately 1 year. Tamoxifen (TAM), a selective estrogen receptor modulator (SERM), has been used to treat GBM for many years. ER‐α36 is a novel variant of estrogen receptor‐alpha66 (ER‐α66) and can mediate cell proliferation through estrogen or anti‐estrogen signaling in different cancer cells. Previously, we found that ER‐α36 was highly expressed in GBM and was involved in the tamoxifen sensitivity of glioblastoma cells. However, the molecular mechanism responsible has not been well established. Here, we found that ER‐α36 is highly expressed in glioblastoma specimens. We further found that ER‐α36 knockdown increased sensitivity of glioblastoma U87 cells to TAM and decreased autophagy in these cells. However, ER‐α36 overexpression decreased TAM sensitivity and induced autophagy. We also established TAM‐resistant glioblastoma U251 cells by a long‐term culture in TAM‐containing medium and found that TAM‐resistant cells showed a six‐fold increase of ER‐α36 mRNA expression and elevated basal autophagy. ER‐α36 knockdown in these TAM‐resistant cells restored TAM sensitivity. In addition, we recapitulated the physiologically relevant tumor microenvironment in an integrated microfluidic device, and U87 cells were treated with a gradient of TAM. We found that ER‐α36 expression is consistent with autophagy protein P62 in a three‐dimensional microenvironment. In summary, these results indicate that ER‐α36 contributes to tamoxifen resistance in glioblastoma cells presumably through regulation of autophagy.

Tamoxifen overrides autophagy inhibition in Beclin-1-deficient glioma cells and their resistance to adenovirus-mediated oncolysis via upregulation of PUMA and BAX

Autophagy is an evolutionarily conserved process regulating cellular homeostasis via digestion of dysfunctional proteins and whole cellular organelles by mechanisms, involving their enclosure into double-membrane vacuoles that are subsequently fused to lysosomes. Glioma stem cells utilize autophagy as a main mechanism of cell survival and stress response. Most recently, we and others demonstrated induction of autophagy in gliomas in response to treatment with chemical drugs, such as temozolomide (TMZ) or oncolytic adenoviruses (Ads). As autophagy has been implicated in the mechanism of Ad-mediated cell killing, autophagy deficiency in some glioma tumors could be the reason for their resistance to oncolysis. Despite the observed connection, the exact relationship between autophagy-activating cell signaling and adenoviral infection remains unclear. Here, we report that inhibition of autophagy in target glioma cells induces their resistance to killing by oncolytic agent CRAd-S-5/3. Furthermore, we found that downregulation of autophagy inducer Beclin-1 inhibits replication-competent Ad-induced oncolysis of human glioma by suppressing cell proliferation and inducing premature senescence. To overcome the autophagy-deficient state of such glioma cells and restore their susceptibility to oncolytic Ad infection, we propose treating glioma tumors with an anticancer drug tamoxifen (TAM) as a means to induce apoptosis in Ad-targeted cancer cells via upregulation of BAX/PUMA genes. In agreement with the above hypothesis, our data suggest that TAM improves susceptibility of Beclin-1-deficient glioma cells to CRAd-S-5/3 oncolysis by means of activating autophagy and pro-apoptotic signaling pathways in the target cancer cells.

Autophagy in glioma cells: An identity crisis with a clinical perspective

Over the last decade, autophagy has emerged as one of the critical cellular systems that control homeostasis. Besides management of normal homeostatic processes, autophagy can also be induced by tissue damage stress or by rapidly progressing tumors. During tumor progression, autophagy mediates a cellular reaction to the changes inside and outside of cells, which leads to tumor adaptation. Even though the regulation of autophagy seems universal and is a well-described process, its dysregulation and role in glioma progression remain an important topic of investigation. In this review, we summarize recent evidence of autophagy regulation in brain tumor tissues and possible interconnection between signaling pathways that govern cellular responses. This perspective may help to assess the qualitative differences and various outcomes in response to autophagy stimulation.

PM2.5 induces autophagy-mediated cell death via NOS2 signaling in human bronchial epithelium cells

The biggest victim of ambient air pollution is the respiratory system. Mainly because of the harmful components, especially the particulate matters with an aerodynamic diameter of ≤ 2.5µm (PM2.5), can be directly inhaled and deeply penetrate into the lung alveoli, thus causing severe lung dysfunction, including chronic cough, bronchitis and asthma, even lung cancer. Unfortunately, the toxicological mechanisms of PM2.5 associations with these adverse respiratory outcomes have still not been clearly unveiled. Here, we found that PM2.5 rapidly induced inflammatory responses, oxidative injure and cell death in human bronchial epithelium cells through upregulation of IL-6 expression, ROS production and apoptosis. Furthermore, PM2.5 specifically induced nitric oxide synthase 2 (NOS2) expression and NO generation to elevate excessive autophagy. Finally, disruption of NOS2 signaling effectively blocked autophayosome formation and the subsequent cell death. Our novel findings systemically reveled the role of autophagy-mediated cell death in PM2.5-treated human bronchial epithelium cells and provided potential strategy for future clinic intervention.

CMV70-3P miRNA contributes to the CMV mediated glioma stemness and represents a target for glioma experimental therapy

Glioblastoma multiforme (GBM) is a rapidly progressive brain tumor with a median survival of 15–19 months. Therapeutic resistance and recurrence of the disease is attributed to cancer stem cells (CSC). Here, we report that CMV70-3P miRNA encoded by CMV increases GBM CSC stemness. Inhibition of CMV70-3P expression using oligo inhibitors significantly attenuated the ability of primary glioma cells to proliferate and form neurospheres. At the molecular level, we show that CM70-3P increases expression of cellular SOX2. Collectively, these findings indicate that CMV70-3P is a potential regulator of CMV- mediated glioma progression and cancer stemness.

KISS1 tumor suppressor restricts angiogenesis of breast cancer brain metastases and sensitizes them to oncolytic virotherapy in vitro

KISS1 tumor suppressor protein regulates cancer cell invasion via MMP9 metalloproteinase. Downregulation of KISS1 gene expression promotes progression of breast cancer and melanoma, resulting in the development of distant metastases. In the current study, we investigated whether restoration of KISS1 expression in KISS1-deficient human metastatic breast cancer cells holds potential as an advanced anticancer strategy. To this end we engineered an infectivity-enhanced conditionally-replicative human adenovirus type 5 encoding KISS1 as an "arming" transgene in the Ad5 E3 region for an ectopic KISS1 expression in transduced cancer cells. The oncolytic potential of the vector was examined using brain-invading metastatic clones of CN34 and MDA-MB-231 breast cancer cells, which supported high levels of AdKISS1 replication, correlating with a robust CRAd-mediated cytotoxicity. Secretion of cellular factors responsible for tumor angiogenesis, cell-to-cell communication and anti-tumoral immune responses upon KISS1 expression in breast cancer cells was analyzed by a RayBiotech Kiloplex Quantibody array. Overall, our results indicate that KISS1 transgene expression provides an important benefit for CRAd-mediated cytotoxicity in breast cancer cells and holds potential as an anticancer treatment in conjunction with oncolytic virotherapy of breast and other metastatic cancers.

[ARTICLE WITHDRAWN] Knockdown of Long Noncoding RNA LINC00152 Suppresses Cellular Proliferation and Invasion in Glioma Cells by Regulating miR-4775

Long noncoding RNAs (lncRNAs) play an important role in various biological properties of glioma cells. Herein we aimed to elucidate the function and the possible molecular mechanisms of long intergenic noncoding RNA 152 (LINC00152) in glioma cells. Relative expressions of LINC00152, miR-4775, and CDK6 in U-118 MG cells were regulated by transfections. Thereafter, cell viability, migration, invasion, and apoptosis were analyzed by CCK-8, Transwell, and flow cytometry assays. Dual-Luciferase Reporter Assay was conducted to validate the target genes of LINC00152 and miR-4775. Expression of components of the signal pathways were detected by Western blot. The results showed that LINC00152 knockdown significantly suppressed cell viability, migration, and invasion and induced apoptosis in vitro. Additionally, LINC00152 functioned as a molecular sponge for miR-4775, and inhibition of miR-4775 reversed the tumor-suppressive effects of LINC00152 knockdown on glioma cells. Furthermore, CDK6 was confirmed to be a target of miR-4775, and overexpression of CDK6 reduced apoptosis and abolished the inhibitory effects of miR-4775 overexpression on cell viability, migration, and invasion. Overexpression of CDK6 activated the PI3K/AKT/MAPK and Notch signal pathways. Overall, these findings demonstrate that LINC00152 plays an oncogenic role in glioma cells by regulation of miR-4775, which may therefore be a potential therapeutic target for glioma.

Immunohistochemical Characterization and Sensitivity to Human Adenovirus Serotypes 3, 5, and 11p of New Cell Lines Derived from Human Diffuse Grade II to IV Gliomas

BACKGROUND

Oncolytic adenoviruses show promise in targeting gliomas because they do not replicate in normal brain cells. However, clinical responses occur only in a subset of patients. One explanation could be the heterogenic expression level of virus receptors. Another contributing factor could be variable activity of tumor antiviral defenses in different glioma subtypes.

METHODS

We established a collection of primary low-passage cell lines from different glioma subtypes (3 glioblastomas, 3 oligoastrocytomas, and 2 oligodendrogliomas) and assessed them for receptor expression and sensitivity to human adenovirus (HAd) serotypes 3, 5, and 11p. To gauge the impact of antiviral defenses, we also compared the infectivity of the oncolytic adenoviruses in interferon (IFN)-pretreated cells with IFN-sensitive Semliki Forest virus (SFV).

RESULTS

Immunostaining revealed generally low expression of HAd5 receptor CAR in both primary tumors and derived cell lines. HAd11p receptor CD46 levels were maintained at moderate levels in both primary tumor samples and derived cell lines. HAd3 receptor DSG-2 was reduced in the cell lines compared to the tumors. Yet, at equal multiplicities of infection, the oncolytic potency of HAd5 in vitro in tumor-derived cells was comparable to HAd11p, whereas HAd3 lysed fewer cells than either of the other two HAd serotypes in 72 hours. IFN blocked replication of SFV, while HAds were rather unaffected.

CONCLUSIONS

Adenovirus receptor levels on glioma-derived cell lines did not correlate with infection efficacy and may not be a relevant indicator of clinical oncolytic potency. Adenovirus receptor analysis should be preferentially performed on biopsies obtained perioperatively.

Impact of Autophagy in Oncolytic Adenoviral Therapy for Cancer

Oncolytic virotherapy has recently emerged as a promising strategy for inducing tumor-specific cell death. Adenoviruses are widely and frequently used in oncolytic virotherapy. The mechanism of oncolytic adenovirus-mediated tumor suppression involves virus-induced activation of the autophagic machinery in tumor cells. Autophagy is a cytoprotective process that produces energy via lysosomal degradation of intracellular components as a physiologic response to various stresses, including hypoxia, nutrient deprivation, and disruption of growth signaling. However, infection with oncolytic adenoviruses induces autophagy and subsequent death of tumor cells rather than enhancing their survival. In this review, we summarize the beneficial role of autophagy in oncolytic adenoviral therapy, including the roles of infection, replication, and cell lysis. Numerous factors are involved in the promotion and inhibition of oncolytic adenovirus-mediated autophagy. Furthermore, recent evidence has shown that oncolytic adenoviruses induce autophagy-related immunogenic cell death (ICD), which enhances the antitumor immune response by inducing the activation of danger signal molecules and thus represents a novel cancer immunotherapy. Understanding the precise role of oncolytic adenovirus-induced autophagy and ICD could enhance the therapeutic potential of oncolytic adenoviral therapy for treating various cancers.

TGFβ-Responsive HMOX1 Expression Is Associated with Stemness and Invasion in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most common and lethal adult brain tumor. Resistance to standard radiation and chemotherapy is thought to involve survival of GBM cancer stem cells (CSCs). To date, no single marker for identifying GBM CSCs has been able to capture the diversity of CSC populations, justifying the needs for additional CSC markers for better characterization. Employing targeted mass spectrometry, here we present five cell-surface markers HMOX1, SLC16A1, CADM1, SCAMP3, and CLCC1 which were found to be elevated in CSCs relative to healthy neural stem cells (NSCs). Transcriptomic analyses of REMBRANDT and TCGA compendiums also indicated elevated expression of these markers in GBM relative to controls and non-GBM diseases. Two markers SLC16A1 and HMOX1 were found to be expressed among pseudopalisading cells that reside in the hypoxic region of GBM, substantiating the histopathological hallmarks of GBM. In a prospective study (N = 8) we confirmed the surface expression of HMOX1 on freshly isolated primary GBM cells (P0). Employing functional assays that are known to evaluate stemness, we demonstrate that elevated HMOX1 expression is associated with stemness in GBM and can be modulated through TGFβ. siRNA-mediated silencing of HMOX1 impaired GBM invasion-a phenomenon related to poor prognosis. In addition, surgical resection of GBM tumors caused declines (18% ± 5.1SEM) in the level of plasma HMOX1 as measured by ELISA, in 8/10 GBM patients. These findings indicate that HMOX1 is a robust predictor of GBM CSC stemness and pathogenesis. Further understanding of the role of HMOX1 in GBM may uncover novel therapeutic approaches. Stem Cells 2016;34:2276-2289.

Nucleolin antagonist triggers autophagic cell death in human glioblastoma primary cells and decreased in vivo tumor growth in orthotopic brain tumor model

Nucleolin (NCL) is highly expressed in several types of cancer and represents an interesting therapeutic target. It is expressed at the plasma membrane of tumor cells, a property which is being used as a marker for several human cancer including glioblastoma. In this study we investigated targeting NCL as a new therapeutic strategy for the treatment of this pathology. To explore this possibility, we studied the effect of an antagonist of NCL, the multivalent pseudopeptide N6L using primary culture of human glioblastoma cells. In this system, N6L inhibits cell growth with different sensitivity depending to NCL localization. Cell cycle analysis indicated that N6L-induced growth reduction was due to a block of the G1/S transition with down-regulation of the expression of cyclin D1 and B2. By monitoring autophagy markers such as p62 and LC3II, we demonstrate that autophagy is enhanced after N6L treatment. In addition, N6L-treatment of mice bearing tumor decreased in vivo tumor growth in orthotopic brain tumor model and increase mice survival. The results obtained indicated an anti-proliferative and pro-autophagic effect of N6L and point towards its possible use as adjuvant agent to the standard therapeutic protocols presently utilized for glioblastoma.

MT1-MMP silencing by an shRNA-armed glioma-targeted conditionally replicative adenovirus (CRAd) improves its anti-glioma efficacy in vitro and in vivo

MMP14 (MT1-MMP) is a cell membrane-associated proteinase of the extracellular matrix, whose biological roles vary from angiogenesis to cell proliferation and survival. We recently found a direct correlation between MMP14 expression levels in brain tumors of glioma patients and the disease progression. By using gene silencing as an experimental approach we found that MMP14 knockdown decreases production of pro-angiogenic factors such as VEGF and IL8 and thereby suppresses angiogenesis in glioma tumors. Although the clinical relevance of MMP14 down-regulation and its possible implications for glioma therapy in humans remain unclear, we observed a significant improvement in animal survival upon down-regulation of MMP14 in murine intracranial glioma xenografts infected with MMP14 shRNA-expressing CRAd. We further found that down-regulation of MMP14 in gliomas by combinational treatment with CRAd-S-5/3 and Marimastat, a chemical inhibitor of metalloproteinases, augments suppression of pro-angiogenic factors, caused by the replication-competent adenovirus. We also demonstrated that delivery of MMP14-targeting shRNA by a fiber-modified adenoviral vector to the glioma cells effectively suppresses their proliferation in vitro and in vivo. Thus our data indicate that inhibition of MMP14 expression in tumors in combination with glioma virotherapy could be effectively utilized to suppress angiogenesis and neovascularization of glioma tumors by decreasing production of pro-angiogenic factors.