Inhibition of glioma growth by minocycline is mediated through endoplasmic reticulum stress-induced apoptosis and autophagic cell death

The combination therapy using tyrosine kinase receptors inhibitors and repurposed drugs to target patient-derived glioblastoma stem cells

The lesson from many studies investigating the efficacy of targeted therapy in glioblastoma (GBM) showed that a future perspective should be focused on combining multiple target treatments. Our research aimed to assess the efficacy of drug combinations against glioblastoma stem cells (GSCs). Patient-derived cells U3042, U3009, and U3039 were obtained from the Human Glioblastoma Cell Culture resource. Additionally, the study was conducted on a GBM commercial U251 cell line. Gene expression analysis related to receptor tyrosine kinases (RTKs), stem cell markers and genes associated with significant molecular targets was performed, and selected proteins encoded by these genes were assessed using the immunofluorescence and flow cytometry methods. The cytotoxicity studies were preceded by analyzing the expression of specific proteins that serve as targets for selected drugs. The cytotoxicity study using the MTS assay was conducted to evaluate the effects of selected drugs/candidates in monotherapy and combinations. The most cytotoxic compounds for U3042 cells were Disulfiram combined with Copper gluconate (DSF/Cu), Dacomitinib, and Foretinib with IC50 values of 52.37 nM, 4.38 µM, and 4.54 µM after 24 h incubation, respectively. Interactions were assessed using SynergyFinder Plus software. The analysis enabled the identification of the most effective drug combinations against patient-derived GSCs. Our findings indicate that the most promising drug combinations are Dacomitinib and Foretinib, Dacomitinib and DSF/Cu, and Foretinib and AZD3759. Since most tested combinations have not been previously examined against glioblastoma stem-like cells, these results can shed new light on designing the therapeutic approach to target the GSC population.

Minocycline as a prospective therapeutic agent for cancer and non-cancer diseases: a scoping review

Minocycline is an FDA-approved secondary-generation tetracycline antibiotic. It is a synthetic antibiotic having many biological effects, such as antioxidant, anti-inflammatory, anti-cancer, and neuroprotective functions. This study discusses the pharmacological mechanisms of preventive and therapeutic effects of minocycline. Specifically, it provides a comprehensive overview of the molecular pathways by which minocycline acts on the different cancers, including ovarian, breast, glioma, colorectal, liver, pancreatic, lung, prostate, melanoma, head and neck, leukemia, and non-cancer diseases such as Alzheimer's disease, Parkinson, schizophrenia, multiple sclerosis, Huntington, polycystic ovary syndrome, and coronavirus disease 19. Minocycline may be a potential medication for these disorders due to its strong blood-brain barrier penetrance. It is also widely accepted as a specific medication, has a well-known side-effect characteristic, is reasonably priced, making it appropriate for continuous use in managing diseases, and has been demonstrated as an oral approach because it is effectively absorbed and accomplished almost all of the body's parts.

The application of electrosprayed minocycline-loaded PLGA microparticles for the treatment of glioblastoma

The survival of patients with glioblastoma multiforme (GBM), the most common and invasive form of malignant brain tumors, remains poor despite advances in current treatment methods including surgery, radiotherapy, and chemotherapy. Minocycline is a semi-synthetic tetracycline derivative that has been widely used as an antibiotic and more recently, it has been utilized as an antiangiogenic factor to inhibit tumorigenesis. The objective of this study was to investigate the utilization of electrospraying process to fabricate minocycline-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles with high drug loading and loading efficiency and to evaluate their ability to induce cell toxicity in human glioblastoma (i.e., U87-MG) cells. The results from this study demonstrated that solvent mixture of dicholoromethane (DCM) and methanol is the optimal solvent combination for minocycline and larger amount of methanol (i.e., 70:30) resulted in a higher drug loading. All three solvent ratios of DCM:methanol tested produced microparticles that were both spherical and smooth, all in the micron size range. The electrosprayed microparticles were able to elicit a cytotoxic response in U87-MG glioblastoma cells at a lower concentration of drug compared to the free drug. This work provides proof of concept to the hypothesis that electrosprayed minocycline-loaded PLGA microparticles can be a promising agent for the treatment of GBM and could have potential application for cancer therapies.

Chaperone-Mediated Autophagy Controls Proteomic and Transcriptomic Pathways to Maintain Glioma Stem Cell Activity

Chaperone-mediated autophagy (CMA) is a homeostatic process essential for the lysosomal degradation of a selected subset of the proteome. CMA activity directly depends on the levels of LAMP2A, a critical receptor for CMA substrate proteins at the lysosomal membrane. In glioblastoma (GBM), the most common and aggressive brain cancer in adulthood, high levels of LAMP2A in the tumor and tumor-associated pericytes have been linked to temozolomide resistance and tumor progression. However, the role of LAMP2A, and hence CMA, in any cancer stem cell type or in glioblastoma stem cells (GSC) remains unknown. In this work, we show that LAMP2A expression is enriched in patient-derived GSCs, and its depletion diminishes GSC-mediated tumorigenic activities. Conversely, overexpression of LAMP2A facilitates the acquisition of GSC properties. Proteomic and transcriptomic analysis of LAMP2A-depleted GSCs revealed reduced extracellular matrix interaction effectors in both analyses. Moreover, pathways related to mitochondrial metabolism and the immune system were differentially deregulated at the proteome level. Furthermore, clinical samples of GBM tissue presented overexpression of LAMP2, which correlated with advanced glioma grade and poor overall survival. In conclusion, we identified a novel role of CMA in directly regulating GSCs activity via multiple pathways at the proteome and transcriptome levels.

SIGNIFICANCE

A receptor of chaperone-mediated autophagy regulates glioblastoma stem cells and may serve as a potential biomarker for advanced tumor grade and poor survival in this disease.

Paclitaxel-induced stress granules increase LINE-1 mRNA stability to promote drug resistance in breast cancer cells

Abnormal expression of long interspersed element-1 (LINE-1) has been implicated in drug resistance, while our previous study showed that chemotherapy drug paclitaxel (PTX) increased LINE-1 level with unknown mechanism. Bioinformatics analysis suggested the regulation of LINE-1 mRNA by drug-induced stress granules (SGs). This study aimed to explore whether and how SGs are involved in drug-induced LINE-1 increase and thereby promotes drug resistance of triple negative breast cancer (TNBC) cells. We demonstrated that SGs increased LINE-1 expression by recruiting and stabilizing LINE-1 mRNA under drug stress, thereby adapting TNBC cells to chemotherapy drugs. Moreover, LINE-1 inhibitor efavirenz (EFV) could inhibit drug-induced SG to destabilize LINE-1. Our study provides the first evidence of the regulation of LINE-1 by SGs that could be an important survival mechanism for cancer cells exposed to chemotherapy drugs. The findings provide a useful clue for developing new chemotherapeutic strategies against TNBCs.

Caffeine Inhibits Growth of Temozolomide-Treated Glioma via Increasing Autophagy and Apoptosis but Not via Modulating Hypoxia, Angiogenesis, or Endoplasmic Reticulum Stress in Rats

Thirty rats with glioma were divided into control group, temozolomide (TMZ) group (TMZ 30 mg/kg once daily for 5 day), and TMZ plus Caffeine group (TMZ 30 mg/kg once daily for 5 day and caffeine 100 mg/kg once daily for 2 weeks). The relative tumor fold and expression of hypoxia-induced factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), neuropilin-1 (NRP-1), CCAAT/enhancer-binding protein homologous protein (CHOP), LC-3A/B, apoptosis-inducing factor-1 (AIF-1), and cleaved caspase three were compared. The relative tumor fold of TMZ plus Caffeine group was lower significantly than that of TMZ group at day 14. HIF-1α, VEGF, NRP-1, and CHOP expressions were not significantly different in the three groups. The LC-3A/B expression of TMZ plus Caffeine group was higher significantly than that of the control group and TMZ group. The AIF expressions of TMZ group and TMZ plus Caffeine group were higher significantly than that of the control group. The caspase-3 expression of TMZ plus Caffeine group was higher significantly than that of the control group and TMZ group. In conclusions, the inhibitory effect of caffeine on TMZ-treated glioma might be associated with increasing expressions of autophagy- and apoptosis-related genes.

Characterizing Cell Stress and GRP78 in Glioma to Enhance Tumor Treatment

Glioblastoma (GBM) is the most common primary brain tumor, carrying a very poor prognosis, with median overall survival at about 12 to 15 months despite surgical resection, chemotherapy with temozolomide (TMZ), and radiation therapy. GBM recurs in the vast majority of patients, with recurrent tumors commonly displaying increase in resistance to standard of care chemotherapy, TMZ, as well as radiotherapy. One of the most commonly cited mechanisms of chemotherapeutic and radio-resistance occurs via the glucose-regulated protein 78 (GRP78), a well-studied mediator of the unfolded protein response (UPR), that has also demonstrated potential as a biomarker in GBM. Overexpression of GRP78 has been directly correlated with malignant tumor characteristics, including higher tumor grade, cellular proliferation, migration, invasion, poorer responses to TMZ and radiation therapy, and poorer patient outcomes. GRP78 expression is also higher in GBM tumor cells upon recurrence. Meanwhile, knockdown or suppression of GRP78 has been shown to sensitize cells to TMZ and radiation therapy. In light of these findings, various novel developing therapies are targeting GRP78 as monotherapies, combination therapies that enhance the effects of TMZ and radiation therapy, and as treatment delivery modalities. In this review, we delineate the mechanisms by which GRP78 has been noted to specifically modulate glioblastoma behavior and discuss current developing therapies involving GRP78 in GBM. While further research is necessary to translate these developing therapies into clinical settings, GRP78-based therapies hold promise in improving current standard-of-care GBM therapy and may ultimately lead to improved patient outcomes.

Minocycline in Treating Glioblastoma Multiforme: Far beyond a Conventional Antibiotic

One of the most lethal forms of CNS pathologies is glioblastoma multiforme (GBM) that represents high invasiveness, uncontrolled proliferation, and angiogenic features. Its invasiveness is responsible for the high recurrence even after maximal surgical interventions. Minocycline is a semisynthetic analog of tetracyclines with potential anti-inflammatory and anticancer effects, distinct from its antimicrobial activity. In this review, we highlight the importance and the cytotoxic mechanisms of minocycline on GBM pathophysiology. Considering the role of certain enzymes in autophagy, apoptosis, tumor cell invasion, and metastatic ability, the possible use of tetracyclines for cancer therapy should be investigated, especially GBM. The present study is, therefore, going to cover the main topics in minocycline pharmacology to date, encouraging its consideration as a new treatment approach for cancer and GBM.

Betulinic Acid-Mediated Tuning of PERK/CHOP Signaling by Sp1 Inhibition as a Novel Therapeutic Strategy for Glioblastoma

Patients with glioblastoma are at high risk of local recurrences after initial treatment with standard therapy, and recurrent tumor cells appear to be resistant to first-line drug temozolomide. Thus, finding an effective second-line agent for treating primary and recurrent glioblastomas is critical. Betulinic acid (BA), a natural product of plant origin, can cross the blood-brain barrier. Here, we investigated the antitumor effects of BA on typical glioblastoma cell lines and primary glioblastoma cells from patients, as well as corresponding temozolomide-resistant cells. Our findings verified that BA significantly reduced growth in all examined cells. Furthermore, gene-expression array analysis showed that the unfolded-protein response was significantly affected by BA. Moreover, BA treatment increased activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK)/C/EBP homologous protein (CHOP) apoptotic pathway, and reduced specificity protein 1 (Sp1) expression. However, Sp1 overexpression reversed the observed cell-growth inhibition and PERK/CHOP signaling activation induced by BA. Because temozolomide-resistant cells exhibited significantly increased Sp1 expression, we concluded that Sp1-mediated PERK/CHOP signaling inhibition protects glioblastoma against cancer therapies; hence, BA treatment targeting this pathway can be considered as an effective therapeutic strategy to overcome such chemoresistance and tumor relapse.

Receptor tyrosine kinase targeting in glioblastoma: performance, limitations and future approaches

From all central nervous system tumors, gliomas are the most common. Nowadays, researchers are looking for more efficient treatments for these tumors, as well as ways for early diagnosis. Receptor tyrosine kinases (RTKs) are major targets for oncology and the development of small-molecule RTK inhibitors has been proven successful in cancer treatment. Mutations or aberrant activation of the RTKs and their intracellular signaling pathways are linked to several malignant diseases, including glioblastoma. The progress in the understanding of malignant glioma evolution has led to RTK targeted therapies with high capacity to improve the therapeutic response while reducing toxicity. In this review, we present the most important RTKs (i.e. EGFR, IGFR, PDGFR and VEGFR) currently used for developing cancer therapeutics together with the potential of RTK-related drugs in glioblastoma treatment. Also, we focus on some therapeutic agents that are currently at different stages of research or even in clinical phases and proved to be suitable as re-purposing candidates for glioblastoma treatment.

Autophagy in the Immunosuppressive Perivascular Microenvironment of Glioblastoma

Glioblastoma (GB) has been shown to up-regulate autophagy with anti- or pro-oncogenic effects. Recently, our group has shown how GB cells aberrantly up-regulate chaperone-mediated autophagy (CMA) in pericytes of peritumoral areas to modulate their immune function through cell-cell interaction and in the tumor’s own benefit. Thus, to understand GB progression, the effect that GB cells could have on autophagy of immune cells that surround the tumor needs to be deeply explored. In this review, we summarize all the latest evidence of several molecular and cellular immunosuppressive mechanisms in the perivascular tumor microenvironment. This immunosuppression has been reported to facilitate GB progression and may be differently modulated by several types of autophagy as a critical point to be considered for therapeutic interventions.

Relevance of Translation Initiation in Diffuse Glioma Biology and its Therapeutic Potential

Cancer cells are continually exposed to environmental stressors forcing them to adapt their protein production to survive. The translational machinery can be recruited by malignant cells to synthesize proteins required to promote their survival, even in times of high physiological and pathological stress. This phenomenon has been described in several cancers including in gliomas. Abnormal regulation of translation has encouraged the development of new therapeutics targeting the protein synthesis pathway. This approach could be meaningful for glioma given the fact that the median survival following diagnosis of the highest grade of glioma remains short despite current therapy. The identification of new targets for the development of novel therapeutics is therefore needed in order to improve this devastating overall survival rate. This review discusses current literature on translation in gliomas with a focus on the initiation step covering both the cap-dependent and cap-independent modes of initiation. The different translation initiation protagonists will be described in normal conditions and then in gliomas. In addition, their gene expression in gliomas will systematically be examined using two freely available datasets. Finally, we will discuss different pathways regulating translation initiation and current drugs targeting the translational machinery and their potential for the treatment of gliomas.

The dual roles of autophagy in gliomagenesis and clinical therapy strategies based on autophagic regulation mechanisms

Autophagy, a self-digestion intracellular catabolic process, plays a crucial role in cellular homeostasis under conditions of starvation, oxidative stress and genotoxic stress. The capability of maintaining homeostasis contributes to preventing malignant behavior in normal cells. Many studies have provided compelling evidence that autophagy is involved in brain tumor recurrence and chemotherapy and radiotherapy resistance. Gliomas, as the primary central nervous system (CNS) tumors, are characterized by rapid, aggressive growth and recurrence and have a poor prognosis and bleak outlook even with modern multimodality strategies involving maximal surgical resection, radiotherapy and alkylating agent-based chemotherapy. Autophagy-associated signaling pathways, such as the extracellular signal-regulated kinase1/2 (ERK1/2) pathway, class I phosphatidylinositol 3-phosphate kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway and nuclear factor kappa-B (NF-κB) pathway, act as tumor suppressors or protect tumor cells against chemotherapy/radiotherapy-induced cytotoxicity in gliomagenesis. Through these pathways, both lethal autophagy and protective autophagy play crucial roles in tumor initiation, chemoresistance and glioma stem cell differentiation. Moreover, lethal autophagy and protective autophagy have been identified as novel therapeutic targets in glioma according to the mechanisms described above. Here, we discuss the multiple impacts of the autophagic response on distinct phases of gliomagenesis and the advanced progress of therapies based on this concept.

Recombinant Newcastle disease virus expressing human IFN-λ1 (rL-hIFN-λ1)-induced apoptosis of A549 cells is connected to endoplasmic reticulum stress pathways

BACKGROUND

IFN-λs are a kind of cytokine with anti-tumor, immunomodulatory, and anti-proliferative activity. Recent studies have shown that the recombinant Newcastle disease virus expresses human IFN-λ1 (rL-hIFN-λ1), which plays a role in gastric cancer cell apoptosis. Endoplasmic reticulum stress (ERS) induces autophagy and apoptosis in tumor cells. In this study, we explored the relationship between ERS and rL-hIFN-λ1-induced apoptosis of lung adenocarcinoma A549 cells and its underlying mechanism.

METHODS

First, we investigated the effect of rL-hIFN-λ1 on cellular proliferation, migration, and proteins associated with ERS, autophagy, and apoptosis of A549. Second, after administration of the ERS inhibitor, the associated proteins induced by rL-hIFN-λ1 were detected. Finally, a subcutaneous mouse model was used to examine the effect of rL-hIFN-λ1 on tumor growth and the ERS and apoptosis associated proteins in tumor tissues.

RESULTS

The results showed that the proliferation and migration of A549 cells, and tumor tissue growth were significantly inhibited and the ERS, autophagy, and apoptosis associated proteins were upregulated in the experimental group. Additionally, both 4-PBA and knockdown of PERK or CHOP reduced the levels of rL-hIFN-λ1-induced autophagy and apoptosis-associated proteins. BCL-2 knockdown caused autophagy and apoptosis associated protein upregulation.

CONCLUSIONS

In summary, rL-hIFN-λ1 inhibited cell proliferation and activated ERS, autophagy, and apoptosis in A549 cells and tissues, and when ERS pathways were blocked, the inhibiting effect was even more pronounced. Therefore, the recombinant Newcastle disease virus rL-hIFN-λ1-induced apoptosis of A549 cells is connected to ER stress and could be a promising therapeutic agent for lung adenocarcinoma.

Fisetin: A bioactive phytochemical with potential for cancer prevention and pharmacotherapy

A wide variety of chronic diseases, such as neurodegenerative and cardiovascular disorders, diabetes mellitus, osteoarthtitis, obesity and various cancers, are now being treated with cost effective phytomedicines. Since synthetic medicines are very expensive, concerted efforts are being made in developing and poor countries to discover cost effective medicines for the treatment of non-communicable diseases (NCDs). Understanding the underlying mechanisms of bioactive medicines from natural sources would not only open incipient avenues for the scientific community and pharmaceutical industry to discover new drug molecules for the therapy of NCDs, but also help to garner knowledge for alternative therapeutic approaches for the management of chronic diseases. Fisetin is a polyphenolic molecule of flavonoids class, and belongs to the bioactive phytochemicals that have potential to block multiple signaling pathways associated with NCDs such as cell division, angiogenesis, metastasis, oxidative stress, and inflammation. The emerging evidence suggests that fisetin may be useful for the prevention and management of several types of human malignancies. Efforts are being made to enhance the bioavailability of fisetin after oral administration to prevent and/or treat cancer of the liver, breast, ovary and other organs. The intent of this review is to highlight the in vitro and in vivo activities of fisetin and to provide up-to-date information about the molecular interactions of fisetin with its cellular targets involved in cancer initiation, promotion and progression as well as to focus on strategies underway to increase the bioavailability and reduce the risk of deleterious effects, if any, associated with fisetin administration.

Regulation of autophagy inhibition and inflammatory response in glioma by Wnt signaling pathway

The objective of this study was to investigate the mechanism of the function of Wnt signaling pathway in regulating autophagy and inflammatory response in glioma cells. Human brain glioma cells U118 were selected and divided into three groups: i) the Wnt signaling inhibitor IWR-1 group (the observation group); ii) the PBS negative control group (the PBS group) and iii) the blank control group. After 24 h culture, Wnt5a/β-catenin protein, autophagy marker, microtubule-associated-proteins-1A1B-light-chain-3C (LC-3) II and Beclin I, and inflammatory factors IL-6 and TNF-α protein expression levels were evaluated using western blotting. Compared with both control groups, Wnt5a/β-catenin, IL-6 and TNF-α protein expression levels were significantly lower, and LC-3II and Beclin I protein expression levels were significantly higher in the observation group. In conclusion, Wnt5a/β-catenin signaling pathway regulates autophagy and inflammatory response of glioma cells.

NF-κB pathway link with ER stress-induced autophagy and apoptosis in cervical tumor cells

Targeting endoplasmic reticulum (ER) stress is being investigated for its anticancer effect in various cancers, including cervical cancer. However, the molecular pathways whereby ER stress mediates cell death remain to be fully elucidated. In this study, we confirmed that ER stress triggered by compounds such as brefeldin A (BFA), tunicamycin (TM), and thapsigargin (TG) leads to the induction of the unfolded protein response (UPR) in cervical cancer cell lines, which is characterized by elevated levels of inositol-requiring kinase 1α, glucose-regulated protein-78, and C/EBP homologous protein, and swelling of the ER observed by transmission electron microscope (TEM). We found that BFA significantly increased autophagy in tumor cells and induced TC-1 tumor cell death in a dose-dependent manner. BFA increased punctate staining of LC3 and the number of autophagosomes observed by TEM in TC-1 and HeLa cells. The autophagic flux was also assessed. Bafilomycin, which blocked degradation of LC3 in lysosomes, caused both LC3I and LC3II accumulation. BFA initiated apoptosis of TC-1 tumor cells through activation of the caspase-12/caspase-3 pathway. At the same time, BFA enhanced the phosphorylation of IκBα protein and translocation into the nucleus of NF-κB p65. Quinazolinediamine, an NF-κB inhibitor, attenuated both autophagy and apoptosis induced by BFA; meanwhile, it partly enhances survival of cervical cancer cells following BFA treatment. In conclusion, our results indicate that the cross-talk between ER stress, autophagy, apoptosis, and the NF-κB pathways controls the fate of cervical cancer cells. Careful evaluation should be given to the addition of an NF-κB pathway inhibitor to treat cervical cancer in combination with drugs that induce ER stress-mediated cell death.

A novel HDAC6 inhibitor Tubastatin A: Controls HDAC6-p97/VCP-mediated ubiquitination-autophagy turnover and reverses Temozolomide-induced ER stress-tolerance in GBM cells

Temozolomide (TMZ) is the cornerstone of therapy for glioblastoma multiforme (GBM). However, its efficacy is limited due to the development of multidrug resistance (MDR). In this study, we first identified the occurrence of ER stress-tolerance (ERST) in glioma cells and confirmed that ERST was positively correlated with TMZ resistance. We further showed that the seesaw-effect of HDAC6-p97/VCP (increased HDAC6 and decreased p97/VCP) in glioma cells was crucial to ERST-associated TMZ resistance. Moreover, the combination treatment of Tubastatin A (TUB, a selective inhibitor of HDAC6) and TMZ synergistically overcame ERST, reduced cell viability and induced apoptosis in TMZ-resistant glioma cells. TUB and TMZ triggered pro-apoptotic signals of the unfolded protein response (UPR) and ER stress and reversed the ratio between HDAC6 and p97/VCP, which potentially attenuated the activation of heat shock proteins and mediated the reversal of ERST. The combination treatment also triggered the dissociation of Dynein-HDAC6 and attenuation of the Dynein-Dynactin motor complex. In addition, this treatment induced HDAC6-p97/VCP-mediated ubiquitination-autophagy turnover, which was involved in the degradation and clearance of ubiquitinated misfolded proteins. This effect could be partially reversed by HDAC6 KO and/or p97/VCP overexpression. Therefore, we proposed that glioma cells optimized the clearance of ubiquitinated misfolded proteins via the reinforcement of HDAC6-facilitated autophagy and attenuation of the p97/VCP-mediated ubiquitin-proteasome system (UPS). In conclusion, our findings showed that the balance of HDAC6-p97/VCP was crucial to ERST-associated TMZ resistance and that HDAC6 inhibition might be a synergistic target and strategy along with TMZ for the improvement of clinical glioma treatment.

Recombinant Newcastle disease virus (rL-RVG) triggers autophagy and apoptosis in gastric carcinoma cells by inducing ER stress

We have reported that the recombinant avirulent Newcastle disease virus (NDV) LaSota strain expressing the rabies virus glycoprotein (rL-RVG) could induce autophagy and apoptosis in gastric carcinoma cells. In the present study, we explored the upstream regulators, endoplasmic reticulum (ER) stress that induce autophagy and apoptosis and the relationships among them. For this purpose, SGC-7901 and HGC cells were infected with rL-RVG. NDV LaSota strain and phosphate-buffered saline (PBS) were treated as the control groups. Western blotting and immunofluorescence microscopy were used to detect the expression of the ER stress-related proteins glucose-regulated protein 78 (GRP78) and the transcription factor GADD153 (CHOP), among others. The expression of beclin-1 and the conversion of light chain (LC) 3-I were used to determine the occurrence of autophagy, and flow cytometry (FCM) and western blotting were used to examine apoptosis-related protein expression. Transmission electron microscopy was also performed to monitor the ultrastructure of the cells. Moreover, small interfering (si) RNA was used to knock down CHOP expression. rL-RVG treatment increased the expression of ER stress-related proteins, such as GRP78, CHOP, activating transcriptional factor 6 (ATF6), X-box-binding protein 1 (XBP-1), and phosphorylated eukaryotic initiation factor 2 (p-eIF2α), in a time- and concentration-dependent manner, and knockdown of CHOP reduced LC3-II conversion and beclin-1 expression. When ER stress was inhibited with 4-PBA, the expression of both autophagy-related proteins and apoptosis-related proteins markedly decreased. Interestingly, inhibition of autophagy with 3-methyladenine (3MA) decreased not only apoptosis-related protein expression but also ER stress-related protein expression. Moreover, we found that downregulation of the c-Jun N-terminal kinase (JNK) pathway by SP600125 reduced LC3-II conversion, beclin-1 expression and caspase-3 activation. Collectively, the results suggest that rL-RVG increased ER stress in three branch pathways (ATF6, inositol-requiring enzyme 1 (IRE1), and PKR-like ER protein kinase (PERK)) that are upstream regulators of autophagy and apoptosis. Moreover, the IRE1-JNK pathway played an important role in switching ER stress to autophagy. These findings will provide molecular bases for developing rL-RVG into a drug candidate for the treatment of gastric carcinoma.

Paclitaxel and the dietary flavonoid fisetin: a synergistic combination that induces mitotic catastrophe and autophagic cell death in A549 non-small cell lung cancer cells

Background

The use of the dietary polyphenols as chemosensitizing agents to enhance the efficacy of conventional cytostatic drugs has recently gained the attention of scientists and clinicians as a plausible approach for overcoming the limitations of chemotherapy (e.g. drug resistance and cytotoxicity). The aim of this study was to investigate whether a naturally occurring diet-based flavonoid, fisetin, at physiologically attainable concentrations, could act synergistically with clinically achievable doses of paclitaxel to produce growth inhibitory and/or pro-death effects on A549 non-small cell lung cancer cells, and if it does, what mechanisms might be involved.

Methods

The drug–drug interactions were analyzed based on the combination index method of Chou and Talalay and the data from MTT assays. To provide some insights into the mechanism underlying the synergistic action of fisetin and paclitaxel, selected morphological, biochemical and molecular parameters were examined, including the morphology of cell nuclei and mitotic spindles, the pattern of LC3-II immunostaining, the formation of autophagic vacuoles at the electron and fluorescence microscopic level, the disruption of cell membrane asymmetry/integrity, cell cycle progression and the expression level of LC3-II, Bax, Bcl-2 and caspase-3 mRNA.

Results

Here, we reported the first experimental evidence for the existence of synergism between fisetin and paclitaxel in the in vitro model of non-small cell lung cancer. This synergism was, at least partially, ascribed to the induction of mitotic catastrophe. The switch from the cytoprotective autophagy to the autophagic cell death was also implicated in the mechanism of the synergistic action of fisetin and paclitaxel in the A549 cells. In addition, we revealed that the synergism between fisetin and paclitaxel was cell line-specific as well as that fisetin synergizes with arsenic trioxide, but not with mitoxantrone and methotrexate in the A549 cells.

Conclusions

Our results provide rationale for further testing of fisetin in the combination with paclitaxel or arsenic trioxide to obtain detailed insights into the mechanism of their synergistic action as well as to evaluate their toxicity towards normal cells in an animal model in vivo. We conclude that this study is potentially interesting for the development of novel chemotherapeutic approach to non-small cell lung cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-016-0288-3) contains supplementary material, which is available to authorized users.

Dracorhodin perchlorate induces the apoptosis of glioma cells

Dracorhodin perchlorate (Dp), a synthetic analogue of the antimicrobial anthocyanin red pigment, has recently been shown to induce apoptotic cell death in various types of cancer cells. Yet, the inhibitory effect of Dp on human glioma cells remains uninvestigated. Therefore, in the present study, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry were used to detect cell viability and cell cycle progression in glioma U87MG and T98G cells, respectively. Annexin V-FITC/propidium iodide double staining and JC-1 staining were separately applied to determine cellular apoptosis and mitochondrial membrane potential damage in the cells. The expression levels of associated proteins involved in cell cycle progression and apoptosis were measured by western blotting. The activities of caspase‑9/-3 were determined by Caspase-Glo-9/3 assay. The results indicated that Dp treatment significantly inhibited cell proliferation in a dose- and time-dependent manner, and blocked cell cycle progression at the G1/S phase in the U87MG and T98G cells via the upregulation of p53 and p21 protein expression, and simultaneous downregulation of Cdc25A, Cdc2 and P-Cdc2 protein expression. Additionally, Dp treatment led to the loss of cellular mitochondrial membrane potential, and the release of cytochrome c, and strongly induced the occurence of apoptosis. Increased expression levels of Bim and Bax protein and the downregulated expression of Bcl-2 protein were observed. Caspase-9/-3 were activated and their activities were elevated after Dp treatment. These findings indicate that Dp inhibits cell proliferation, induces cell cycle arrest and apoptosis in glioma cells, and is a possible candidate for glioma treatment.

Antibiotic drug tigecycline inhibits melanoma progression and metastasis in a p21CIP1/Waf1-dependent manner

Antibiotics are common drugs with low toxicity but high effectiveness. They have been suggested to be drug candidates for cancer therapy in recent years. Here, we tried to investigate the antitumour effect of tigecycline on malignant melanoma. We showed that tigecycline dramatically inhibited cell proliferation and induced cell cycle arrest at G0/G1 phase. At the same time, tigecycline suppressed cell invasion and migration through preventing epithelial-mesenchymal transition (EMT) process. In addition, tigecycline also significantly blocked tumor growth in vivo. Expression of cell cycle-related proteins were investigated and resulted in downregulation of G1/S checkpoint proteins, such as CDK2 and Cyclin E. However, cyclin-dependent kinase inhibitor 1 (CDKN1A, p21(CIP1/Waf1)) was downregulated after tigecycline treatment, which was not conformed to its conventional function. To explain this, we overexpressed p21 in melanoma cells. We found that p21 overexpression significantly rescued tigecycline-induced cell proliferation inhibition as well as migration and invasion suppression. Taken together, our results revealed that the essential role of p21 in the inhibitory effect of tigecycline on proliferation, migration and invasion of melanoma. Tigecycline might act as a candidate therapeutic drug for treatment of patients suffering from malignant melanoma.

Mouse low-grade gliomas contain cancer stem cells with unique molecular and functional properties

The availability of adult malignant glioma stem cells (GSCs) has provided unprecedented opportunities to identify the mechanisms underlying treatment resistance. Unfortunately, there is a lack of comparable reagents for the study of pediatric low-grade glioma (LGG). Leveraging a neurofibromatosis 1 (Nf1) genetically engineered mouse LGG model, we report the isolation of CD133(+) multi-potent low-grade glioma stem cells (LG-GSCs), which generate glioma-like lesions histologically similar to the parent tumor following injection into immunocompetent hosts. In addition, we demonstrate that these LG-GSCs harbor selective resistance to currently employed conventional and biologically targeted anti-cancer agents, which reflect the acquisition of new targetable signaling pathway abnormalities. Using transcriptomic analysis to identify additional molecular properties, we discovered that mouse and human LG-GSCs harbor high levels of Abcg1 expression critical for protecting against ER-stress-induced mouse LG-GSC apoptosis. Collectively, these findings establish that LGG cancer stem cells have unique molecular and functional properties relevant to brain cancer treatment.

Cellular factors promoting resistance to effective treatment of glioma with oncolytic myxoma virus

Oncolytic virus therapy is being evaluated in clinical trials for human glioma. While it is widely assumed that the immune response of the patient to the virus infection limits the utility of the therapy, investigations into the specific cell type(s) involved in this response have been performed using nonspecific pharmacologic inhibitors or allogeneic models with compromised immunity. To identify the immune cells that participate in clearing an oncolytic infection in glioma, we used flow cytometry and immunohistochemistry to immunophenotype an orthotopic glioma model in immunocompetent mice after Myxoma virus (MYXV) administration. These studies revealed a large resident microglia and macrophage population in untreated tumors, and robust monocyte, T-, and NK cell infiltration 3 days after MYXV infection. To determine the role on the clinical utility of MYXV therapy for glioma, we used a combination of knockout mouse strains and specific immunocyte ablation techniques. Collectively, our experiments identify an important role for tumor-resident myeloid cells and overlapping roles for recruited NK and T cells in the clearance and efficacy of oncolytic MYXV from gliomas. Using a cyclophosphamide regimen to achieve lymphoablation prior and during MYXV treatment, we prevented treatment-induced peripheral immunocyte recruitment and, surprisingly, largely ablated the tumor-resident macrophage population. Virotherapy of cyclophosphamide-treated animals resulted in sustained viral infection within the glioma as well as a substantial survival advantage. This study demonstrates that resistance to MYXV virotherapy in syngeneic glioma models involves a multifaceted cellular immune response that can be overcome with cyclophosphamide-mediated lymphoablation.

Cell death and tissue reorganization in Rhynchosciara americana (Sciaridae: Diptera) metamorphosis and their relation to molting hormone titers

Programmed cell death (PCD) is a focal topic for understanding processes underlying metamorphosis in insects, especially so in holometabolous orders. During adult morphogenesis it allows for the elimination of larva-specific tissues and the reorganization of others for their functionalities in adult life. In Rhynchosciara, this PCD process could be classified as autophagic cell death, yet the expression of apoptosis-related genes and certain morphological aspects suggest that processes, autophagy and apoptosis may be involved. Aiming to reveal the morphological changes that salivary gland and fat body cells undergo during metamorphosis we conducted microscopy analyses to detect chromatin condensation and fragmentation, as well as alterations in the cytoplasm of late pupal tissues of Rhynchosciara americana. Transmission electron microscopy and confocal microscopy revealed cells in variable stages of death. By analyzing the morphological structure of the salivary gland we observed the presence of cells with autophagic vacuoles and apoptotic bodies and DNA fragmentation was confirmed with the TUNEL assay in salivary gland. The reorganization of fat body occurs with discrete detection of cell death by TUNEL assay. However, both salivary gland histolysis and fat body reorganization occur under control of the hormone ecdysone.

Mig-2 attenuates cisplatin-induced apoptosis of human glioma cells in vitro through AKT/JNK and AKT/p38 signaling pathways

AIM

Mig-2 (also known as Kindlin-2 and FERMT2) is an important regulator of integrin activation and cell-extracellular matrix adhesion, and involved in carcinogenesis and tumor progression. The aim of this study was to investigate the role of mig-2 in cisplatin-induced apoptosis of human glioma cells in vitro.

METHODS

The expression of mig-2 was modulated in human glioma H4, HS 683 and U-87 MG cells by transfection with a plasmid carrying mig-2 or mig-2 siRNA. Cisplatin-induced apoptosis was detected using Annexin V/PI staining and flow cytometry, as well as MTS analyses. The expression of apoptosis-related or signaling proteins was examined using Western blotting analysis. H4 cells were transfected with plasmids carrying mig-2 mutants to determine the functional domain of mig-2.

RESULTS

In the 3 glioma cell lines tested, overexpression of mig-2 significantly attenuated cisplatin-induced apoptosis, whereas knock-down of mig-2 potentiated the apoptosis. The mechanisms of action of mig-2 were further addressed in H4 cells: overexpression of mig-2 markedly reduced cleaved caspase-9, caspase-8, caspase-3 and PARP, as well as p-JNK and p-p38, and increased p-AKT in cisplatin-treated H4 cells, whereas mig-2 siRNA reversely changed these apoptosis-related and signaling proteins. Furthermore, pretreatment with JNK inhibitor SP600125 and p38 inhibitor SB203580, or with AKT inhibitor LY294002 abolished the effects of mig-2 on cisplaxtin-induced apoptosis. In H4 cells, GFP-mig-2 F3 plasmid that contained only the F3 subdomain showed the same efficiency in attenuating cisplatin-induced apoptosis, as the mig-2 wild-type vector did, whereas GFP-mig-2 (1-541) plasmid that lacked the F3 subdomain was inactive.

CONCLUSION

Mig-2 significantly attenuates the antitumor action of cisplatin against human glioma cells in vitro through AKT/JNK and AKT/p38 signaling pathways. The F3 subdomain of mig-2 is necessary and sufficient for this effect.

Glioma-associated microglial MMP9 expression is upregulated by TLR2 signaling and sensitive to minocycline

The invasiveness of malignant gliomas is one of the major obstacles in glioma therapy and the reason for the poor survival of patients. Glioma cells infiltrate into the brain parenchyma and thereby escape surgical resection. Glioma associated microglia/macrophages support glioma infiltration into the brain parenchyma by increased expression and activation of extracellular matrix degrading proteases such as matrix metalloprotease (MMP) 2, MMP9 and membrane-type 1 MMP. In this work we demonstrate that, MMP9 is predominantly expressed by glioma associated microglia/macrophages in mouse and human glioma tissue but not by the glioma cells. Supernatant from glioma cells induced the expression of MMP9 in cultured microglial cells. Using mice deficient for different Toll-like receptors we identified Toll-like receptor 2/6 as the signaling pathway for the glioma induced upregulation of microglial MMP9. Also in an experimental mouse glioma model, Toll-like receptor 2 deficiency attenuated the upregulation of microglial MMP9. Moreover, glioma supernatant triggered an upregulation of Toll-like receptor 2 expression in microglia. Both, the upregulation of MMP9 and Toll-like receptor 2 were attenuated by the antibiotic minocycline and a p38 mitogen-activated protein kinase antagonist in vitro. Minocycline also extended the survival rate of glioma bearing mice when given to the drinking water. Thus glioma cells change the phenotype of glioma associated microglia/macrophages in a complex fashion using Toll-like receptor 2 as an important signaling pathway and minocycline further proved to be a potential candidate for adjuvant glioma therapy.

Tetracycline derivative minocycline inhibits autophagy and inflammation in concanavalin-a-activated human hepatoma cells

Inhibition of soluble matrix metalloproteinase (MMP) activity is among the non-antibiotic cellular effects exerted by the anti-inflammatory tetracycline derivative minocycline. The impact of minocycline on the signal transduction functions of membrane-bound MMPs is however unknown. We assessed minocycline in a concanavalin-A (ConA)-activated human HepG2 hepatoma cell model, a condition known to increase the expression of membrane type-1 MMP (MT-MMP) and to trigger inflammatory and autophagy processes. We found that minocycline inhibited ConA-induced formation of autophagic acidic vacuoles, green fluorescent microtubule-associated protein 1 light chain 3 (GFP-LC3) puncta formation, gene and protein expression of autophagy biomarker BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3), invasion biomarker MT1-MMP, and inflammation biomarker cyclooxygenase (COX)-2. Gene silencing of MT1-MMP abrogated ConA-induced formation of autophagic acidic vacuoles and ConA-induced expressions of BNIP3 and COX-2. Minocycline was also shown to inhibit ConA-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation as well as gene expression of NANOS1, a biomarker believed to colocalize with MT1-MMP and the specific silencing of which further inhibited ConA-induced STAT3 phosphorylation. Collectively, our data demonstrate that part of minocycline’s effects on autophagy could be exerted through the inhibition of MT1-MMP signaling functions, which contribute to the autophagy and inflammatory phenotype of ConA-activated HepG2 cells.

Minocycline inhibits angiogenesis in vitro through the translational suppression of HIF-1α

Minocycline was recently found to be effective against cancer. However, the precise molecular mechanisms of minocycline in cancer are poorly understood. Hypoxia-inducible factor-1 (HIF-1, a heterodimeric transcription factor composed of HIF-1α and β) activates the transcription of genes that are involved in angiogenesis in cancer. In this study, we found that minocycline significantly inhibits HIF-1α protein expression and suppresses HIF-1 transcriptional activity. The tube formation assay showed that minocycline has anti-angiogenic activity and suppresses hypoxia-induced vascular endothelial growth factor (VEGF) expression. The metabolic labeling assay showed that minocycline reduces HIF-1α protein translation and global protein synthesis. In addition, minocycline suppresses mTOR signaling and increases the phosphorylation of eIF2α, which is known to be related to the translational regulation of HIF-1α expression. These findings collectively indicate that minocycline is a potential inhibitor of HIF-1α and provide new insight into the discovery of drugs for cancer treatment.