Vesicular Organelles Research Articles

Acridine orange exhibits photodamage in human bladder cancer cells under blue light exposure

Human bladder cancer (BC) cells exhibit a high basal level of autophagic activity with accumulation of acridine-orange(AO)-stained acidic vesicular organelles. The rapid AO relocalization was observed in treated BC cells under blue-light emission. To investigate the cytotoxic effects of AO on human BC cell lines under blue-light exposure, human immortalized uroepithelial (SV-Huc-1) and BC cell lines (5637 and T24) were treated with indicated concentrations of AO or blue-light exposure alone and in combination. The cell viability was then determined using WST-1, time-lapse imaging with a Cytosmart System and continuous quantification with a multi-mode image-based reader. Treatment of AO or blue-light exposure alone did not cause a significant loss of viability in BC cells. However, AO exhibited a dose-dependent increment of cytotoxicity toward BC cells under blue-light exposure. Furthermore, the tumor formation of BC cells with treatment was significantly reduced when evaluated in a mouse xenograft model. The photodamage caused by AO was nearly neglected in SV-Huc-1 cells, suggesting a differential effect of this treatment between cancer and normal cells. In summary, AO, as a photosensitizer, disrupts acidic organelles and induces cancer cell death in BC cells under blue-light irradiation. Our findings may serve as a novel therapeutic strategy against human BC.

Hispolon suppresses metastasis via autophagic degradation of cathepsin S in cervical cancer cells

Hispolon, a phenolic compound isolated from Phellinus igniarius, induces apoptosis and anti-tumor effects in cancers. However, the molecular mechanism involved in hispolon-mediated tumor-suppressing activities observed in cervical cancer is poorly characterized. Here, we demonstrated that treatment with hispolon inhibited cell metastasis in two cervical cancer cell lines. In addition, the downregulation of the lysosomal protease Cathepsin S (CTSS) was critical for hispolon-mediated suppression of tumor cell metastasis in both in vitro and in vivo models. Moreover, hispolon induced autophagy, which increased LC3 conversion and acidic vesicular organelle formation. Mechanistically, hispolon inhibited the cell motility of cervical cells through the extracellular signal-regulated kinase (ERK) pathway, and blocking of the ERK pathway reversed autophagy-mediated cell motility and CTSS inhibition. Our results indicate that autophagy is essential for decreasing CTSS activity to inhibit tumor metastasis by hispolon treatment in cervical cancer; this finding provides a new perspective on molecular regulation.

Beclin 1 expression is associated with the occurrence and development of esophageal squamous cell carcinoma.

Beclin 1 has a central role in the regulation of autophagy, differentiation, apoptosis resistance, tumorigenesis and cancer progression. The role of Beclin 1 in the development of esophageal squamous cell carcinoma (ESCC) and its subsequent progression is not fully characterized. In the present study, the role of Beclin 1 and autophagy in ESCC was evaluated. The expression of Beclin 1 mRNA and protein levels in human ESCC tumor and adjacent normal esophageal tissue was measured. Beclin 1 mRNA and protein were significantly lower in tumor tissue than in normal esophageal tissue (P<0.05). Cells of the less differentiated esophageal tumors expressed lower Beclin 1 mRNA and protein (P<0.05). Tumors from patients in early clinical stages (I/II) exhibited significantly higher Beclin 1 mRNA and protein expression levels than patients with tumors in mid-to-late stages (III/IV; P<0.05). Tumors from patients with lymph node metastasis exhibited significantly lower Beclin 1 mRNA and protein expression levels compared with tumors from patients without lymph node involvement (P<0.05). Beclin 1 downregulation was demonstrated to significantly upregulate invasion by ESCC EC9706 cells (P<0.01), and downregulate the number of acidic vesicular organelles, a process associated with autophagy. These results suggest that the expression of Beclin 1 is associated with the occurrence and development of ESCC. Measuring the Beclin 1 expression of tumors from patient may improve the understanding of the prognosis of patients with ESCC.

Oncolytic Reovirus Infection Is Facilitated by the Autophagic Machinery.

Mammalian reovirus is a double-stranded RNA virus that selectively infects and lyses transformed cells, making it an attractive oncolytic agent. Despite clinical evidence for anti-tumor activity, its efficacy as a stand-alone therapy remains to be improved. The success of future trials can be greatly influenced by the identification and the regulation of the cellular pathways that are important for reovirus replication and oncolysis. Here, we demonstrate that reovirus induces autophagy in several cell lines, evident from the formation of Atg5-Atg12 complexes, microtubule-associated protein 1 light chain 3 (LC3) lipidation, p62 degradation, the appearance of acidic vesicular organelles, and LC3 puncta. Furthermore, in electron microscopic images of reovirus-infected cells, autophagosomes were observed without evident association with viral factories. Using UV-inactivated reovirus, we demonstrate that a productive reovirus infection facilitates the induction of autophagy. Importantly, knock-out cell lines for specific autophagy-related genes revealed that the expression of Atg3 and Atg5 but not Atg13 facilitates reovirus replication. These findings highlight a central and Atg13-independent role for the autophagy machinery in facilitating reovirus infection and contribute to a better understanding of reovirus-host interactions.

Hexane fraction of Pluchea indica root extract inhibits proliferation and induces autophagy in human glioblastoma cells.

Pluchea indica (L.) Less. is a perennial plant known for its versatile uses in traditional medicine. Previous findings have shown that the extracts of Pluchea indica possess significant anti-inflammatory, anti-ulcer and anti-tuberculosis activity. The aim of this study was to demonstrate the anticancer activity of the hexane fraction of P. indica root extract (H-PIRE) in human glioblastoma cells using flow cytometric and western blot analysis. The results shoewd that, H-PIRE suppressed the growth of glioblastoma cells in a dose-dependent manner. H-PIRE treatment markedly decreased the population of cells in S and G2/M phases. The significant upregulation of acidic vesicular organelle (AVO) was detected during H-PIRE treatment. The expression levels of microtubule-associated light chain 3-II (LC3-II) protein, phosphorylated JNK and phosphorylated p38 were significantly increased, confirming the occurrence of autophagy during the process. Finally, the combination treatment of H-PIRE and LY294002, a pan PI3K inhibitor, further decreased cell viability, suggesting an additive anticancer effect. Taken together, our results suggest that H-PIRE suppresses the proliferation of glioblastoma cells by inducing cell cycle arrest and autophagy.

Adenine causes cell cycle arrest and autophagy of chronic myelogenous leukemia K562 cells via AMP-activated protein kinase signaling.

AMP-activated protein kinase (AMPK) is known as a pivotal regulator of cellular metabolism. Mounting evidences have demonstrated that AMPK activation exerts tumor suppressive activity on leukemia cells. The present study reported that adenine, an AMPK activator, triggers cell cycle arrest and autophagy of human chronic myelogenous leukemia K562 cells consequently suppressing cell viability. The present findings revealed that adenine treatment (4.0-8.0 mM) significantly inhibited the viability of K562 cells to 69.3±2.5% (24 h) and 53.4±2.1% (48 h) of the control. Flow cytometric analysis revealed that there was a significant accumulation in G2/M phase, but not sub-G1 phase K562 cells following exposure to adenine. Additional investigation demonstrated that adenine treatments significantly increased the number of acidic vesicular organelles and the level of autophagosomal microtubule associated protein 1 light chain 3 α (LC3) marker. By contrast, cleavage of caspase-9, caspase-3 and poly-ADP-ribose polymerase was insignificantly affected in K562 cells following adenine treatment. In K562 cells, adenine was able to markedly promote the phosphorylation of AMPKα and suppress the phosphorylation of mammalian target of rapamycin (mTOR), a downstream target of AMPK. In addition, inhibiting AMPK phosphorylation using dorsomorphin restored mTOR phosphorylation, inhibited the accumulation of LC3 and significantly recovered the suppressed cell viability in response to adenine. Taken together, the present results demonstrated that adenine induced G2/M phase arrest and autophagic cell death, consequently suppressing the viability of K562 cells, which may attribute to the AMPK activation triggered by adenine. These findings provide evidence that adenine may be beneficial to chronic myelogenous leukemia therapy by suppressing excessive cell proliferation.

Curcumin induces apoptosis and protective autophagy in human gastric cancer cells with different degree of differentiation

Objective: To investigate the effect of curcumin on the apoptosis and autophagy of human gastric cancer cells with different degree of differentiation. Methods: Gastric cancer cell lines BGC-823 and MKN-28 were treated with curcumin at different concentrations. The effect of curcumin on cell proliferation was measured by MTT assay. Apoptosis was assessed by flow cytometry. Autophagy status was analyzed by acridine orange staining. The expression levels of apoptotic and autophagy-related proteins were detected by Western blot. Results: The cell viability of BGC-823 and MKN-28 was inhibited by curcumin in a time- and dose-dependent manner. At 48 h after treatment, the IC(50) value of BGC-823 (15.18 μmol/L) was close to that of MKN-28 (15.84 μmol/L), and the difference was not statistically significant (P=0.513). Meanwhile, flow cytometry showed that curcumin induced the apoptosis of gastric cancer cells in a dose-dependent manner. Western blot results showed that the expression of pro-apoptotic proteins bax, active-caspase-3 and active-caspase-9 was significantly increased in BGC-823 and MKN-28 cells, whereas that of the anti-apoptotic protein bcl-2 was strikingly reduced. In addition, the formation of acidic vesicular organelles in cytoplasm, conversion of LC3-Ⅰ to LC3-Ⅱ and increased levels of autophagy-related proteins Beclin1, Atg7 and Atg5-Atg12 were observed in curcumin-treated cells. Moreover, activation of PI3K/Akt/mTOR signaling pathway was also significantly suppressed after curcumin treatment. Blocking autophagy by adding the autophagy inhibitor 3-methyladenine (3-MA) significantly promoted the apoptotic cell death induced by curcumin. Conclusions: Curcumin induces apoptosis and protective autophagy in human gastric cancer cells in vitro. Curcumin combined with autophagy inhibitor may provide a more effective strategy for its clinical application.

Cryo-EM structure and biochemical analysis reveal the basis of the functional difference between human PI3KC3-C1 and -C2.

Phosphatidylinositol 3-phosphate (PI3P) plays essential roles in vesicular trafficking, organelle biogenesis and autophagy. Two class III phosphatidylinositol 3-kinase (PI3KC3) complexes have been identified in mammals, the ATG14L complex (PI3KC3-C1) and the UVRAG complex (PI3KC3-C2). PI3KC3-C1 is crucial for autophagosome biogenesis, and PI3KC3-C2 is involved in various membrane trafficking events. Here we report the cryo-EM structures of human PI3KC3-C1 and PI3KC3-C2 at sub-nanometer resolution. The two structures share a common L-shaped overall architecture with distinct features. EM examination revealed that PI3KC3-C1 "stands up" on lipid monolayers, with the ATG14L BATs domain and the VPS34 C-terminal domain (CTD) directly contacting the membrane. Biochemical dissection indicated that the ATG14L BATs domain is responsible for membrane anchoring, whereas the CTD of VPS34 determines the orientation. Furthermore, PI3KC3-C2 binds much more weakly than PI3KC3-C1 to both PI-containing liposomes and purified endoplasmic reticulum (ER) vesicles, a property that is specifically determined by the ATG14L BATs domain. The in vivo ER localization analysis indicated that the BATs domain was required for ER localization of PI3KC3. We propose that the different lipid binding capacity is the key factor that differentiates the functions of PI3KC3-C1 and PI3KC3-C2 in autophagy.

Abstract 3304: Inhibition of autophagy enhances mitochondria-mediated apoptosis in malignant mesothelioma cells by cisplatin and sulforaphane

Abstract Drug resistance to current chemotherapy regimens has been considered a cell survival adaptive response in malignant mesothelioma cells. Therefore, new strategies to enhance the apoptotic signal and overcome resistance to chemotherapeutics are necessary to improve treatment outcomes for this deadly disease. Here, the effect of sulforaphane, an isothiocyanate compound derived from glucoraphanin present in cruciferous vegetables, on enhancing anticancer role of cisplatin was investigated in malignant mesothelioma cells. At concentrations showing little toxicity in normal human mesothelial MeT-5A cells, the combined treatment with both compounds exhibited synergistic growth-inhibiting and apoptosis-promoting effects, as demonstrated in a series of pro-apoptotic events including reactive oxygen species (ROS) accumulation, loss of mitochondrial membrane potential, up-regulation of p53, increased Bax/Bcl-2 ratio, activation of caspase-3, and the occurrence of a sub-G0/G1 peak with an increase in the cells with pyknotic and fragmented nuclei, Annexin V-PE(+), and G2/M phase transition delay in the cell cycle. The levels of phosphorylation of both Akt and mTOR were decreased by the combined treatment, which was accompanied by a significant increase in the level of autophagosomal marker protein LC3-II and the accumulation of acidic vesicular organelles. Furthermore, scavenging of ROS by antioxidant N-acetylcysteine inhibited both the apoptosis and autophagy, while the inhibition of autophagy by bafilomycin A1 potentiated apoptotic cell death following the combination treatment of sulforaphane and cisplatin, indicating the cytoprotective role of autophagy counteracts apoptosis of malignant mesothelioma cells. Considering the pro-oxidant-based combinational approach, our data provide a rationale for targeting cytoprotective autophagy as a potential therapeutic strategy for malignant mesothelioma. Citation Format: Yoon Jin Lee, David M. Lee, Hae Nam, Sang Lee. Inhibition of autophagy enhances mitochondria-mediated apoptosis in malignant mesothelioma cells by cisplatin and sulforaphane [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3304. doi:10.1158/1538-7445.AM2017-3304

Abstract 3300: Inhibition of autophagy by 3-MA enhances the effect of ursolic acid-induced apoptosis in hepatoma SK-Hep-1 cells

Abstract Purpose The aim of this study is to investigate the autophagic effect of Ursolic Acid (UA) on hepatoma SK-Hep-1 cells. Methods The cytotoxicity of UA in hepatoma SK-Hep-1 cells was measured by MTT assay, the accumulation of acidic vesicular organelles was measured by FACS, the protein expression of LC3-II was detected by immunofluorescence staining, and the autophagic protein expression was evaluated by western blotting. Hepatoma SK-Hep-1 cells treated with a combination of autophagy inhibitor 3-Methyladenine (3-MA) and UA, then use Annexin V/PI Double Staining and western blotting to detect apoptosis and apoptotic protein levels. Statistical Analyses Data was expressed as the mean ± standard deviation and were compared using the Student’s t-test. A p value of &amp;lt;0.05 was considered to indicate statistical significance. All statistical analyses were performed using GraphPad Prism software, version 4.0 (GraphPad Software, Inc., La Jolla, CA, USA). Preliminary Results SK-Hep-1 cells treated with different concentrations of UA (0, 20, 40, and 60 μM). Regarding the results, the half-maximal inhibitory concentration (IC50) was 45.9 and 36.6 μM for 24 and 48 h, respectively. The FACS results showed that when increase the dose of UA could increase the percentages of autophagic populations. The anti-autophagic proteins such as Beclin, Atg-5, Atg-7, and LC3-II, in our results showed that UA decreased the protein expression of mTOR, PI3K, and p62 and PI3K/Akt/mTOR expression. Immunocytochemistry staining showed that SK-Hep-1 cells treated with UA increased the protein expression of LC3-II. The combination treatment of 3-MA and UA significantly increased the apoptotic cell death as monitored by increased protein expression of Caspase-3 and PAPR. Conclusions UA could induced autophagy in hepatoma SK-Hep-1 cells through inhibition of mTOR and PI3K signaling pathways. SK-Hep-1 cells treated with UA exhibited LC3-І/LC3-II conversion, increased protein expression levels of Beclin, Atg-7, and Atg-5 along with reduced protein expression levels of p62. UA-induced apoptosis was enhanced by the treatment of autophagy inhibitor 3-MA. Our findings may assist in the development of novel chemotherapeutic agents for the treatment of malignant types of liver cancer. Citation Format: Chuang Wan-Ling, Lin Ping-Yi, Chen Yao-Li. Inhibition of autophagy by 3-MA enhances the effect of ursolic acid-induced apoptosis in hepatoma SK-Hep-1 cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3300. doi:10.1158/1538-7445.AM2017-3300

Abstract 2322: Antitumor activity of spicatoside A, a steroidal saponin, via induction of switch from autophagy to apoptotic cell death

Abstract The antitumor activity of spicatoside A (SA), a steroidal saponin isolated from the tuber of Liriope platyphylla (Liliaceae), and its underlying mechanisms were investigated in HCT116 human colorectal cancer cells. SA induced autophagy and apoptotic cell death and inhibited tumor growth in a nude mouse xenograft model implanted with HCT116 cells. Treatment with SA for 24 h enhanced the formation of acidic vesicular organelles in the cytoplasm, indicating the induction of the onset of autophagy. This event was associated with the regulation of autophagic markers including microtubule-associated protein 1 light chain 3 (LC3)-II, p62, beclin 1, lysosomal-associated membrane protein 1, and cathepsin D by inhibiting the PI3K/Akt/mTOR signaling pathway, regulating mitogen-activated protein kinase signaling, and increasing p53 levels. However, a prolonged exposure to SA resulted in apoptosis characterized by the accumulation of a sub-G1 cell population and an annexin V/propidium iodide-positive cell population. Apoptosis induced by SA was associated with the regulation of apoptotic proteins including Bcl-2, Bax, and Bid, the release of cytochrome c into the cytosol, and the accumulation of cleaved poly ADP-ribose polymerase (PARP). Further study revealed that cleavage of beclin 1 by caspase-8 plays a critical role in the SA-mediated switch from autophagy to apoptosis. Taken together, these findings highlight the significance of SA in the modulation of crosstalk between autophagy and apoptosis, as well as the potential use of SA as a novel candidate in the treatment of human colorectal cancer cells. Acknowledgement: This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean Government (MEST) (No. 2009-0083533) Citation Format: Won Kyung Kim, Yuna Pyee, Hyen Joo Park, Ji-Young Hong, Sang Kook Lee. Antitumor activity of spicatoside A, a steroidal saponin, via induction of switch from autophagy to apoptotic cell death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2322. doi:10.1158/1538-7445.AM2017-2322

Abstract 185: Development of a novel non-diuretic brain-penetrating ethacrynic acid analog and demonstration of its potent efficacy in orthotopic glioblastoma (GBM) models

Abstract The incidence of pediatric and adult brain tumors has continued to rise and temozolomide (TMZ) has remained the sole choice for chemotherapy of these cancers. A number of factors including the inefficient drug entry through the BBB, intratumoral heterogeneity, overexpression of MGMT repair protein and bone marrow toxicity due to alkylating regimens have impeded successful therapy of these cancers. There is, therefore, an urgent need to design new, more effective brain-penetrating drugs that can effectively eliminate brain tumors. We are highly interested in exploiting the elevated oxidative stress present in gliomas and have synthesized a hydrophobic, non-diuretic analog of ethacrynic acid (EA) called KSS72 [1-(2,3-dichloro-4-methoxyphenyl)-2-methylenebutan-1-one] by removing the carboxylate side chain. KSS72 was selectively cytotoxic to cancer cells including gliomas. Compared to EA which does not cross the BBB, Pharmacokinetics following intravenous or oral administrations in mice showed its excellent penetrance through the blood brain-barrier, KSS72 accumulating at levels equivalent to TMZ (25% of plasma levels) in the brain In vitro assays measuring protein carbonyl content, GSH content, ROS generation, GSTpi enzyme activity and others showed that KSS72 triggers a redox imbalance by inhibiting GSTpi and by lowering the antioxidant (GSH) and reducing equivalent (NADPH) levels, leading to a significant elevation of ROS levels. We also showed the upregulation of endoplasmic reticulum (ER) stress-responsive proteins, activation of MAPK, autophagy and apoptotic pathways by KSS72 in several cell lines. KSS72-induced autophagy was a post event of redox perturbation that displayed a wide array of characteristic features including double membranous vacuoles with entrapped organelles, acidic vesicular organelles, and increased expression of LC3-II and beclin-1. In view of its excellent brain penetrance and multiple cytocidal events mediated by ROS and autophagy, we tested the antitumor efficacy of KSS72 in human GBM cell lines and intracranial GBM xenografts. SF-188 human GBM cells expressing firefly luciferase were injected into the brain just left of bregma for the development of orthotopic GBM in nude mice. These mice were given 25 mg/kg/day of KSS72 intraperitoneally for 2 weeks. The animals when imaged by IVIS after luciferin injections showed a complete lack of intracranial tumors in all KSS72 administered animals. H&amp;E staining of mouse brain sections confirmed the total elimination of GBM by KSS72. KSS72 did not exert any toxicity on host tissues and serum ALT and AST levels were not altered. In summary, we conclude that KSS72 acting through multiple pathways of oxidative stress is a hugely promising non-toxic anti-glioma drug with potential to enter clinical trials (supported by CPRIT grants RP130266 and RP170207 to KSS). Citation Format: Surendra R. Punganuru, Hanumantha Rao Madala, Kalkunte S. Srivenugopal. Development of a novel non-diuretic brain-penetrating ethacrynic acid analog and demonstration of its potent efficacy in orthotopic glioblastoma (GBM) models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 185. doi:10.1158/1538-7445.AM2017-185

Different Concentrations of Titanium Dioxide Nanoparticles Induce Autophagy Followed by Growth Inhibition or Cell Death in A375 Melanoma Cells

: Dysregulation of autophagy is currently known as a contributing factor to tumorigenesis. Accordingly, exploring novel compounds with autophagy - modulating properties is a priority in cancer research. While a number of synthetic compounds have been developed, autophagy - modulating Nanoparticles (NPs), such as titanium dioxide (TiO2), have been recently considered. This research investigated the effects of a well - dispersed form of TiO2 NPs on autophagic vesicle formation in human melanoma A375 cells. The cells were treated with different concentrations of TiO2 NPs (1 - 100 µg/mL) for 24 hours, then growth, cell death, and autophagy were, respectively, evaluated by trypan blue exclusion test, MTT assay, and acridine orange staining. The results showed that well - dispersed TiO2 NPs induced growth inhibition in a dose dependent manner, while cell death was only observed at high concentrations (100 µg/mL). In addition, a significant increase in Acidic Vesicular Organelles (AVO) formation was detected at all concentrations of NPs after 24 hours, suggesting that TiO2 NPs may induce both cytostatic and cytotoxic autophagic responses, depending on the concentration.

Eriocalyxin B, a novel autophagy inducer, exerts anti-tumor activity through the suppression of Akt/mTOR/p70S6K signaling pathway in breast cancer

Eriocalyxin B (EriB), a natural ent-kaurane diterpenoid presented in the plant Isodon eriocalyx var. laxiflora, has been reported to diminish angiogenesis-dependent breast tumor growth. In the present study, the effects of EriB on human breast cancer and its underlying mechanisms were further investigated. The in vitro anti-breast cancer activity of EriB was determined using MCF-7 and MDA-MB-231 cell lines. MDA-MB-231 xenograft model of human breast cancer was also established to explore the anti-tumor effect in vivo.We found that EriB was able to induce apoptosis accompanied by the activation of autophagy, which was evidenced by the increased accumulation of autophagosomes, acidic vesicular organelles formation, the microtubule-associated protein 1A/1B-light chain 3B-II (LC3B-II) conversion from LC3B-I and p62 degradation. Meanwhile, EriB treatment time-dependently decreased the phosphorylation of Akt, mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (p70S6K), leading to the inhibition of Akt/mTOR/p70S6K signaling pathway. Moreover, the blockage of autophagy obviously sensitized EriB-induced cell death, which suggested the cytoprotective function of autophagy in both MCF-7 and MDA-MB-231 cells. Interestingly, the autophagic features and apoptosis induction were prevented by reactive oxygen species (ROS) scavenger N-acetyl-l-cysteine, indicating that ROS played an essential role in the mediation of EriB-induced cell death. Furthermore, in MDA-MB-231 xenograft model, EriB displayed a significant anti-tumor effect via the activation of autophagy and apoptosis in breast tumor cells. Taken together, our findings firstly demonstrated that EriB suppressed breast cancer cells growth both in vitro and in vivo, and thus could be developed as a promising anti-breast tumor agent.

The cell biology of the thyroid-disrupting mechanism of dichlorodiphenyltrichloroethane (DDT).

Dichlorodiphenyltrichloroethane (DDT) is an organochlorine known for its pesticide properties and for its negative effects on human health. It was banned in most countries for its toxicity to the endocrine system, but due to its persistence at clinically relevant concentrations in both soil and animal tissues, DDT is still linked to several health and social problems. We have previously shown that DDT exposure is causally related to the extracellular release of vesicular organelles such as microvesicles and/or exosomes by using immunocytochemistry with gold-tagged antibodies and various fluorescent membrane markers. It is now well recognized that microvesicles and/or exosomes organelles are implicated in cell-to-cell communication, and that they are fundamental elements for transferring proteins, RNA, DNA, lipids and transcriptional factors among cells. In this short review, we discussed the role of extracellular vesicle formation in the thyroid-disrupting mechanism of DDT. In particular, we described how DDT, by dislodging the thyrotropin hormone (TSH) receptor from the raft containing compartments of the cells, prevents its activation and internalization. Based on our earlier finding and on the large body of evidence here reviewed, we propose that DDT-induced formation of extracellular vesicles containing the TSH receptor could be directly involved in the development of autoimmune responses against the TSH receptor and that, therefore, their release could lead to the development of the Graves' disease.

Cytolethal Distending Toxin Enhances Radiosensitivity in Prostate Cancer Cells by Regulating Autophagy.

Cytolethal distending toxin (CDT) produced by Campylobacter jejuni contains three subunits: CdtA, CdtB, and CdtC. Among these three toxin subunits, CdtB is the toxic moiety of CDT with DNase I activity, resulting in DNA double-strand breaks (DSB) and, consequently, cell cycle arrest at the G2/M stage and apoptosis. Radiation therapy is an effective modality for the treatment of localized prostate cancer (PCa). However, patients often develop radioresistance. Owing to its particular biochemical properties, we previously employed CdtB as a therapeutic agent for sensitizing radioresistant PCa cells to ionizing radiation (IR). In this study, we further demonstrated that CDT suppresses the IR-induced autophagy pathway in PCa cells by attenuating c-Myc expression and therefore sensitizes PCa cells to radiation. We further showed that CDT prevents the formation of autophagosomes via decreased high-mobility group box 1 (HMGB1) expression and the inhibition of acidic vesicular organelle (AVO) formation, which are associated with enhanced radiosensitivity in PCa cells. The results of this study reveal the detailed mechanism of CDT for the treatment of radioresistant PCa.

Metformin Synergistically Potentiates the Antitumor Effects of Imatinib in Colorectal Cancer Cells.

ABSTRACTMetformin is the most commonly prescribed anti-diabetic drug with relatively minor side effect. Substantial evidence has suggested that metformin is associated with decreased cancer risk and anticancer activity against diverse cancer cells. The tyrosine kinase inhibitor imatinib has shown powerful activity for treatment of chronic myeloid leukemia and also induces growth arrest and apoptosis in colorectal cancer cells. In this study, we tested the combination of imatinib and metformin against HCT15 colorectal cancer cells for effects on cell viability, cell cycle and autophagy. Our data show that metformin synergistically enhances the imatinib cytotoxicity in HCT15 cells as indicated by combination and drug reduction indices. We also demonstrate that the combination causes synergistic down-regulation of pERK, cell cycle arrest in S and G2/M phases via reduction of cyclin B1 level. Moreover, the combination resulted in autophagy induction as revealed by increased acidic vesicular organelles and cleaved form of LC3-II. Inhibition of autophagic process by chloroquine led to decreased cell viability, suggesting that induction of autophagy seems to play a cell protective role that may act against anticancer effects. In conclusion, our present data suggest that metformin in combination with imatinib might be a promising therapeutic option in colorectal cancer.

Effect of Down-Regulatory Nucleostemin Expression on Autophagy Activities in p53 Null HL-60 Leukemia Cells

Based on previous microarry and bioinformatic analysis results, to investigate the effect of nucleostemin(NS) expression down-regulation on autophagy activity in p53 null HL-60 leukemia cells, so as to provide evidence for studying mechanisms of p53-independent signal pathway of NS in details. The autophagy activity of HL-60 cells after down-regulation of NS expression was detected with acidine orange staining, Western blot and transmission electron mcrioscope technique. The expression level of NS in test groups was lower than that in blank control and negative control groups after HL-60 cells were readily transinfected by lentivirus. The result of acidine orange staining showed that the number of acid vesicular organelle in test groups(22.4±0.76)% was higher than that in blank control groups(3.1±0.28)% and negative control groups(6.2±0.64)% (P<0.05). Western blot showed that the ratio of LC3II/LC3I in test groups(1.537±0.072) was higher than that in blank control and negative control groups (1.010±0.039) and (0.608±0.008). The result of transmission electron mcrioscopy also showed that the number of autophagosomes in test group(8.7±3.1) was higher than that in the blank control and negative control groups(4.2±1.2) and (2.3±0.5). Autophagy activty can be enhanced after the level of NS was down regulated. The change indicates the signaling transductions screened by bioinformatic analysis may be one of p53-independent pathway of NS, which lays a foundation for contineously studying key points of p53-independent signal pathway of NS.

Guanosine promotes cytotoxicity via adenosine receptors and induces apoptosis in temozolomide-treated A172 glioma cells.

Gliomas are a malignant tumor group whose patients have survival rates around 12months. Among the treatments are the alkylating agents as temozolomide (TMZ), although gliomas have shown multiple resistance mechanisms for chemotherapy. Guanosine (GUO) is an endogenous nucleoside involved in extracellular signaling that presents neuroprotective effects and also shows the effect of inducing differentiation in cancer cells. The chemotherapy allied to adjuvant drugs are being suggested as a novel approach in gliomas treatment. In this way, this study evaluated whether GUO presented cytotoxic effects on human glioma cells as well as GUO effects in association with a classical chemotherapeutic compound, TMZ. Classical parameters of tumor aggressiveness, as alterations on cell viability, type of cell death, migration, and parameters of glutamatergic transmission, were evaluated. GUO (500 and 1000μM) decreases the A172 glioma cell viability after 24, 48, or 72h of treatment. TMZ alone or GUO plus TMZ also reduced glioma cell viability similarly. GUO combined with TMZ showed a potentiation effect of increasing apoptosis in A172 glioma cells, and a similar pattern was observed in reducing mitochondrial membrane potential. GUO per se did not elevate the acidic vesicular organelles occurrence, but TMZ or GUO plus TMZ increased this autophagy hallmark. GUO did not alter glutamate transport per se, but it prevented TMZ-induced glutamate release. GUO or TMZ did not alter glutamine synthetase activity. Pharmacological blockade of glutamate receptors did not change GUO effect on glioma viability. GUO cytotoxicity was partially prevented by adenosine receptor (A1R and A2AR) ligands. These results point to a cytotoxic effect of GUO on A172 glioma cells and suggest an anticancer effect of GUO as a putative adjuvant treatment, whose mechanism needs to be unraveled.

Methylone and MDPV activate autophagy in human dopaminergic SH-SY5Y cells: a new insight into the context of β-keto amphetamines-related neurotoxicity.

Autophagy has an essential role in neuronal homeostasis and its dysregulation has been recently linked to neurotoxic effects of a growing list of psychoactive drugs, including amphetamines. However, the role of autophagy in β-keto amphetamine (β-KA) designer drugs-induced neurotoxicity has hitherto not been investigated. In the present study, we show that two commonly abused cathinone derivatives, 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxypyrovalerone (MDPV), elicit morphological changes consistent with autophagy and neurodegeneration, including formation of autophagic vacuoles and neurite retractionin dopaminergic SH-SY5Y cells. Methylone and MDPV prompted the formation of acidic vesicular organelles (AVOs) and lead to increased expression of the autophagy-associated protein LC3-II in a concentration- and time-dependent manner. Electron microscopy confirmed the presence of autophagosomes with typical double membranes and autolysosomes in cells exposed to both β-KA. The autophagic flux was further confirmed using bafilomycin A1, a known inhibitor of the late phase of autophagy. Moreover, we showed that autophagy markers were activated before the triggering of cell death and caspase3 activation, suggesting that β-KA-induced autophagy precedes apoptotic cell death. To address the role of oxidative stress in autophagy induction, we also investigated the effects of antioxidant treatment with N-acetyl-L-cysteine (NAC) on autophagy and apoptotic markers altered by these drugs. NAC significantly attenuated methylone- and MDPV-induced cell death by completely inhibiting the generation ofreactive oxygen and nitrogen species, and hampering both apoptotic and autophagic activity, suggesting that oxidative stress plays an important role in mediating autophagy and apoptosis elicited by these drugs.