Autophagy delays sulindac sulfide-induced apoptosis in the human intestinal colon cancer cell line HT-29

Knockdown of LIMD2 inhibits the progression of ovarian carcinoma through ERK1/2 pathway

BACKGROUND

The incidence rate of ovarian carcinoma (OC) is the third of the female reproductive system malignant tumors, while its mortality rate ranks first among causes of female reproductive system tumor related death in the world.

METHODS

In the present research, we investigated the specific role of LIMD2 through LIMD2 knockdown in OC cells.

RESULTS

The results of online analysis and expression detection proved that LIMD2 was up-regulated in human OC tissues and cells. Knockdown of LIMD2 inhibited the proliferation, migration and invasion in OC cells. LIMD2 knockdown promoted the apoptosis, as well as the expression of Cleaved-Caspase3 and Bax. Importantly, knockdown of LIMD2 promotes cell autophagy. LC3-II/I ratio and Beclin1 expression increased in LIMD2 knockdown cells, while P62 expression declined in LIMD2 knockdown cells. Additionally, the phosphorylation of ERK1/2 was inhibited by the knockdown of LIMD2 in SKOV3 and OVCAR3 cells.

CONCLUSION

Knockdown of LIMD2 inhibits cell proliferation, migration, invasion and autophagy, and promotes the apoptosis through the ERK1/2 signaling pathway, suggesting that LIMD2-siRNA may be an effective molecule to prevent OC progression.

Autophagy: A Key Regulator of Homeostasis and Disease: An Overview of Molecular Mechanisms and Modulators

Autophagy is a highly conserved lysosomal degradation pathway active at basal levels in all cells. However, under stress conditions, such as a lack of nutrients or trophic factors, it works as a survival mechanism that allows the generation of metabolic precursors for the proper functioning of the cells until the nutrients are available. Neurons, as post-mitotic cells, depend largely on autophagy to maintain cell homeostasis to get rid of damaged and/or old organelles and misfolded or aggregated proteins. Therefore, the dysfunction of this process contributes to the pathologies of many human diseases. Furthermore, autophagy is highly active during differentiation and development. In this review, we describe the current knowledge of the different pathways, molecular mechanisms, factors that induce it, and the regulation of mammalian autophagy. We also discuss its relevant role in development and disease. Finally, here we summarize several investigations demonstrating that autophagic abnormalities have been considered the underlying reasons for many human diseases, including liver disease, cardiovascular, cerebrovascular diseases, neurodegenerative diseases, neoplastic diseases, cancers, and, more recently, infectious diseases, such as SARS-CoV-2 caused COVID-19 disease.

Crosstalk Between ROS and Autophagy in Tumorigenesis: Understanding the Multifaceted Paradox

Cancer formation is a highly regulated and complex process, largely dependent on its microenvironment. This complexity highlights the need for developing novel target-based therapies depending on cancer phenotype and genotype. Autophagy, a catabolic process, removes damaged and defective cellular materials through lysosomes. It is activated in response to stress conditions such as nutrient deprivation, hypoxia, and oxidative stress. Oxidative stress is induced by excess reactive oxygen species (ROS) that are multifaceted molecules that drive several pathophysiological conditions, including cancer. Moreover, autophagy also plays a dual role, initially inhibiting tumor formation but promoting tumor progression during advanced stages. Mounting evidence has suggested an intricate crosstalk between autophagy and ROS where they can either suppress cancer formation or promote disease etiology. This review highlights the regulatory roles of autophagy and ROS from tumor induction to metastasis. We also discuss the therapeutic strategies that have been devised so far to combat cancer. Based on the review, we finally present some gap areas that could be targeted and may provide a basis for cancer suppression.

Curcumin mediates autophagy and apoptosis in granulosa cells: a study of integrated network pharmacology and molecular docking to elucidate toxicological mechanisms

Curcumin (Cur) is a flavonoid derived from Curcuma longa L. that has been shown to have a variety of biological activities, but some previous studies have described its non-negligible negative effects on female reproduction and embryo development. To further explore the toxic stress effect, this study investigated apoptosis and autophagy of healthy buffalo (Bubalus bubalis) derived granulosa cells (GCs) exposed to Cur and/or autophagy inhibitors. Results showed that Cur declined viability of GCs in a concentration-dependent manner. Apoptosis was observed in Cur-treated GCs from 3 h. Meanwhile, under Cur stress, autophagosomes accumulated in cells, and the expression levels of autophagy key proteins LC3 and Beclin 1 were up-regulated, suggesting that Cur could induce autophagy in GCs. Early autophagy inhibitor 3-methyladenine (3-MA) increased the apoptosis rate of Cur exposed GCs, but the autophagosome degradation inhibitor chloroquine (CQ) had no effect on the apoptosis rate. The network pharmacological and molecular docking analysis indicated that the perturbation of IKK/NF-κB might be the cause of Cur toxicity toward GCs. This study unveiled another side of Cur pharmacological effects that programmed cell death can be induced by Cur in GCs, suggesting that it should be prudent to use Cur as a clinical drug for its side effects on the female reproductive system.

Autophagy inhibitor potentiates the antitumor efficacy of apatinib in uterine sarcoma by stimulating PI3K/Akt/mTOR pathway

AIM

The present study aims to examine the effects of apatinib combined with autophagy inhibitor 3-Methyladenine (3-MA) on the proliferation and apoptosis of human uterine sarcoma in FU-MMT-1 and MES-SA cells and its tumor inhibition effect in xenograft model of uterine sarcoma.

METHODS

Different concentrations of 3-MA and apatinib were used to treat the uterine sarcoma cell lines (MES-SA and FU-MMT-1 cells). The cell viability was detected by CCK8 method. Flow cytometry was used to detect the apoptosis and cell cycle. Wound closure assay and Transwell assay were performed to measure the migration ability of cells. Western blot was used to determine the apoptosis proteins and autophagy proteins. A nude mice sarcoma xenograft model was established and treated with apatinib alone, 3-MA alone, or combined incubation of them. Tumor size of xenograft and the mice survival rate were measured.

RESULTS

Combination of 3-MA and apatinib significantly inhibited the proliferation and migration ability, but increased the apoptosis rate of uterine sarcoma cells compared to apatinib. The combination of 3-MA and apatinib significantly limited the tumor size of xenograft and increased the survival rate of mice compared to apatinib alone. Apatinib inhibited the PI3K/Akt/mTOR pathway, while 3-MA and the combination of 3-MA and apatinib significantly activated the PI3K/Akt/mTOR pathway and inhibited autophagy. Combination of 3-MA and apatinib increased apoptosis compared to apatinib alone. The expression of VEGFR-2 was not impacted by 3-MA.

CONCLUSION

Combination of apatinib and autophagy inhibitor 3-MA significantly inhibited the growth and migration of uterine sarcoma cells and xenograft. Autophagy inhibition may increase the antitumor effect of apatinib via the PI3K/Akt/mTOR pathway.

Regulation of Autophagy by Non-Steroidal Anti-Inflammatory Drugs in Cancer

Cancer is the leading cause of death, placing a substantial global health burden. The development of the most effective treatment regimen is the unmet clinical need for cancer. Inflammation plays a role in tumorigenesis and progression, and anti-inflammation may be a promising option for cancer management and prevention. Emerging studies have shown that non-steroidal anti-inflammatory drugs (NSAIDs) display anticarcinogenic and chemopreventive properties through the regulation of autophagy in certain types of cancer. In this review, we summarize the pharmacological functions and side effects of NSAIDs as chemotherapeutic agents, and focus on its mode of action on autophagy regulation, which increases our knowledge of NSAIDs and cancer-related inflammation, and contributes to a putative addition of NSAIDs in the chemoprevention and treatment of cancer.

Liposomes encapsulated iridium(III) polypyridyl complexes enhance anticancer activity in vitro and in vivo

Three iridium(III) complexes [Ir(ppy)₂(CPIP)](PF₆) (Ir-1, ppy = 2-phenylpyridine, CPIP = 2-(4-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), [Ir(ppy)₂(DCPIP)](PF₆) (Ir-2, DCPIP = 2-(3,4-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ir(ppy)₂(TCPIP)](PF₆) (Ir-3, TCPIP = 2,3,5-trichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized. The complexes Ir-1, Ir-2 and Ir-3 were encapsulated in liposomes to form Ir-1-Lipo, Ir-2-Lipo and Ir-3-Lipo. Morphology, size distribution, and zeta potential of liposomes were examined by transmission electron microscopy (TEM) and Zetasizer. The cytotoxic activity in vitro of Ir-1, Ir-2 and Ir-3 against cancer A549, HTC-116, HepG2, BEL-7402, Eca-109, B16, HeLa SGC-7901 and normal NIH3T3 cells was evaluated by 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) method. Ir-2 and Ir-3 show no cytotoxic activity against the selected cancer cells, and Ir-1 displays moderate cytotoxic effect on the cell growth in A549 cells. However, Ir-1, Ir-2 and Ir-3 were encapsulated in liposomes, the cytotoxic activity was greatly enhanced. In particular, Ir-1-Lipo and Ir-2-Lipo can effectively inhibit the cell growth in A549 cells with a low IC₅₀ value of 3.1 ± 0.3 and 1.2 ± 0.4 μM. The apoptosis was assayed by flow cytometry. Ir-1, Ir-2 and Ir-3 reveal weak apoptotic effect, whereas Ir-1-Lipo, Ir-2-Lipo and Ir-3-Lipo induce an apoptotic percentage of 55.6%, 69.3% and 16.7% in A549 cells, respectively. Specially, in the assay of antitumor activity in vivo, the inhibiting percentage of tumor growth induced by Ir-2 is 27.65%, while inhibiting percentage of tumor growth caused by Ir-2-Lipo is 57.45%. Obviously, the liposomes can enhance anticancer activity in vitro and in vivo compared with the complexes. The results show that the iridium(III) complexes encapsulated liposomes induce apoptosis in A549 cells through ROS-mediated lysosome-mitochondria dysfunction pathway and target the microtubules.

High glucose: activating autophagy and affecting the biological behavior of human lens epithelial cells

AIM

To clarify the effect of autophagy on human lens epithelial cells (HLECs) under high glucose conditions.

METHODS

HLECs were cultured with different concentrations of glucose and 3-methyladenine (3-MA); the expression of autophagy-related protein LC3B was detected by Western blotting and immunofluorescence histochemistry. The migration of HLECs was quantified by scratch wound assay and the expression of transforming growth factor-β (TGF-β) was measured by real-time polymerase chain reaction.

RESULTS

Compared with 5 mmol/L normal glucose treatment, 40 mmol/L glucose treatment can significantly increase the generation of autophagosome in HLECs, which could be inhibited by 0.375 mmol/L 3-MA treatment. The migration of HLECs and the expression of TGF-β in HLECs induced by high glucose were significantly suppressed by 0.375 mmol/L 3-MA treatment.

CONCLUSION

Autophagy promotes HLECs cell migration and increases the expression of TGF-β after exposed to high glucose, which may relate to the development of diabetic cataract.

Protective mechanism of Wnt4 gene on Parkinson's disease (PD) transgenic Drosophila

OBJECTIVE

The main pathological change of Parkinson's disease (PD) is progressive degeneration and necrosis of dopaminergic neurons in the midbrain, forming a Lewy body in many of the remaining neurons. Studies have found that in transgenic Drosophila, mutations in the PTEN-inducible kinase 1 (PINK1) gene may cause indirect flight muscle defects in Drosophila, and mitochondrial structural dysfunction as well.

METHODS

In this study, Wnt4 gene overexpression and knockdown were performed in PINK1 mutant PD transgenic Drosophila, and the protective effect of Wnt4 gene on PD transgenic Drosophila and its possible mechanism were explored. The Wnt4 gene was screened in the previous experiment; And by using the PD transgenic Drosophila model of the MHC-Gal4/UAS system, the PINK1 gene could be specifically activated in the Drosophila muscle tissue.

RESULTS

In PINK1 mutation transgenic fruit flies, the Wnt4 gene to study its implication on PD transgenic fruit flies' wing normality and flight ability. We found that overexpression of Wnt4 gene significantly reduced abnormality rate of PD transgenic Drosophila and improved its flight ability, and then, increased ATP concentration, enhanced mitochondrial membrane potential and normalized mitochondrial morphology were found. All of these findings suggested Wnt4 gene may have a protective effect on PD transgenic fruit flies. Furthermore, in Wnt4 gene overexpression PD transgenic Drosophila, down-regulation autophagy and apoptosis-related proteins Ref(2)P, Pro-Caspase3, and up-regulation of Beclin1, Atg8a, Bcl2 protein were confirmed by Western Blotting.

CONCLUSION

The results imply that the restoring of mitochondrial function though Wnt4 gene overexpression in the PINK1 mutant transgenic Drosophila may be related to autophagy and/or apoptosis.

Autophagy in Ovarian Follicular Development and Atresia

Autophagy is a mechanism that exists in all eukaryotes under a variety of physiological and pathological conditions. In the mammalian ovaries, less than 1% of follicles ovulate, whereas the remaining 99% undergo follicular atresia. Autophagy and apoptosis have been previously found to be involved in the regulation of both primordial follicular development as well as atresia. The relationship between autophagy, follicular development, and atresia have been summarized in this review with the aim to obtain a more comprehensive understanding of the role played by autophagy in follicular development and atresia.

Autophagy: novel applications of nonsteroidal anti-inflammatory drugs for primary cancer

In eukaryotic cells, autophagy is a process associated with programmed cell death. During this process, cytoplasmic proteins and organelles are engulfed by double-membrane autophagosomes, which then fuse with lysosomes to form autolysosomes. These autolysosomes then degrade their contents to recycle the cellular components. Autophagy has been implicated in a wide variety of physiological and pathological processes that are closely related to tumorigenesis. In recent years, an increasing number of studies have indicated that nonsteroidal anti-inflammatory drugs, such as celecoxib, meloxicam, sulindac, aspirin, sildenafil, rofecoxib, and sodium salicylate, have diverse effects in cancer that are mediated by the autophagy pathway. These nonsteroidal anti-inflammatory drugs can modulate tumor autophagy through the PI3K/Akt/mTOR, MAPK/ERK1/2, P53/DRAM, AMPK/mTOR, Bip/GRP78, CHOP/ GADD153, and HGF/MET signaling pathways and inhibit lysosome function, leading to p53-dependent G1 cell-cycle arrest. In this review, we summarize the research progress in autophagy induced by nonsteroidal anti-inflammatory drugs and the molecular mechanisms of autophagy in cancer cells to provide a reference for the potential benefits of nonsteroidal anti-inflammatory drugs in cancer chemotherapy.

Beclin-1-mediated Autophagy Protects Against Cadmium-activated Apoptosis via the Fas/FasL Pathway in Primary Rat Proximal Tubular Cell Culture

The Fas/FasL signaling pathway is one of the primary apoptosis pathways, but the involvement and regulatory mechanism of this pathway by autophagy remain unclear. Here we demonstrated that cadmium (Cd) activated the Fas/FasL apoptosis pathway in rat proximal tubular (rPT) cells; this was accompanied by simultaneous activation of autophagy resulted in reduced apoptosis. In this model, we induced autophagy through RAPA and further demonstrated that autophagy protects against activation of Fas/FasL signaling and apoptosis. The antiapoptotic effect of autophagy was blocked by 3-MA, an autophagy inhibitor. The interactions between Beclin-1 and Fas, FasL, FADD, caspase-8 and BID/tBID were relatively weak, with the exception of cleaved caspase-8, indicated that minimal interactions between these proteins and Beclin-1 are involved in maintaining the balance of autophagy and apoptosis. Beclin-1 precipitated with cleaved caspase-8 in a dose-dependent mannter, and the expression was increased by siRNA against Beclin-1. These data suggested that Beclin-1-mediated autophagy impairs the expression and function of cleaved caspase-8 to protect against Cd-induced activation of apopotosis through Fas/FasL signaling pathway.

Bisindolylmaleimide alkaloid BMA-155Cl induces autophagy and apoptosis in human hepatocarcinoma HepG-2 cells through the NF-κB p65 pathway

Bisindolylmaleimides, a series of derivatives of a PKC inhibitor staurosporine, exhibit potential as anti-cancer drugs and have received considerable attention in clinical trials. This study aims to investigate the effects of a bisindolylmaleimide alkaloid 155Cl (BMA-155Cl) with a novel structure on autophagy and apoptosis in human hepatocarcinoma HepG-2 cells in vitro and in vivo. The cell poliferation was assessed with a MTT assay. Autophagy was evaluated by MDC staining and TEM analysis. Apoptosis was investigated using Annexin V-FITC/PI and DAPI staining. The antitumor effects were further evaluated in nude mice bearing HepG-2 xenografts, which received BMA-155Cl (10, 20 mg/kg, ip) for 18 days. Autophagy- and apoptosis-associated proteins and their mRNA levels were examined with Western blotting, immunohistochemistry, and RT-PCR. BMA-155Cl (2.5-20 μmol/L) inhibited the growth of HepG-2 cells with IC₅₀ values of 16.62±1.34, 12.21±0.83, and 8.44±1.82 μmol/L at 24, 48, and 72 h, respectively. Furthermore, BMA-155Cl (5-20 μmol/L) dose-dependently induced autophagy and apoptosis in HepG-2 cells. The formation of autophagic vacuoles was induced by BMA-155Cl (10 μmol/L) at approximately 6 h and peaked at approximately 15 h. Pretreatment with 3-MA potentiated BMA-155Cl-mediated apoptotic cell death. This compound dose-dependently increased the mRNA and protein levels of Beclin-1, NF-κB p65, p53, and Bax, but decreased the expression of IκB and Bcl-2. Pretreatment with BAY 11-7082, a specific inhibitor of NF-κB p65, blocked BMA-155Cl-induced expression of autophagy- and apoptosis-associated proteins. BMA-155Cl administration effectively suppressed the growth of HepG-2 xenografts in vivo, and increased the protein expression levels of LC3B, Beclin-1, NF-κB p65, and Bax in vivo. We conclude that the NF-κB p65 pathway is involved in BMA-155Cl-triggered autophagy, followed by apoptosis in HepG-2 cells in vitro and in vivo. Hence, BMA-155Cl could be a promising pro-apoptotic candidate for developing as a novel anti-cancer drug.

In vitro antiglioma action of indomethacin is mediated via AMP-activated protein kinase/mTOR complex 1 signalling pathway

We investigated the role of the intracellular energy-sensing AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway in the in vitro antiglioma effect of the cyclooxygenase (COX) inhibitor indomethacin. Indomethacin was more potent than COX inhibitors diclofenac, naproxen, and ketoprofen in reducing the viability of U251 human glioma cells. Antiglioma effect of the drug was associated with p21 increase and G₂M cell cycle arrest, as well as with oxidative stress, mitochondrial depolarization, caspase activation, and the induction of apoptosis. Indomethacin increased the phosphorylation of AMPK and its targets Raptor and acetyl-CoA carboxylase (ACC), and reduced the phosphorylation of mTOR and mTOR complex 1 (mTORC1) substrates p70S6 kinase and PRAS40 (Ser183). AMPK knockdown by RNA interference, as well as the treatment with the mTORC1 activator leucine, prevented indomethacin-mediated mTORC1 inhibition and cytotoxic action, while AMPK activators metformin and AICAR mimicked the effects of the drug. AMPK activation by indomethacin correlated with intracellular ATP depletion and increase in AMP/ATP ratio, and was apparently independent of COX inhibition or the increase in intracellular calcium. Finally, the toxicity of indomethacin towards primary human glioma cells was associated with the activation of AMPK/Raptor/ACC and subsequent suppression of mTORC1/S6K. By demonstrating the involvement of AMPK/mTORC1 pathway in the antiglioma action of indomethacin, our results support its further exploration in glioma therapy.

Effects of HSP27 downregulation on PDT resistance through PDT-induced autophagy in head and neck cancer cells

We previously reported that photodynamic therapy (PDT) induces cell death in head and neck cancer through both autophagy and apoptosis. Regulation of cell death by autophagy and apoptosis is important to enhance the effects of PDT. Autophagy maintains a balance between cell death and PDT resistance. Downregulation of heat shock protein 27 (HSP27) induces PDT resistance in head and neck cancer cells. Furthermore, HSP70 regulates apoptosis during oxidative stress. However, the role of HSPs in PDT-induced cell death through autophagy and apoptosis is unclear. Therefore, in the present study, we investigated the effects of HSP27 and HSP70 on PDT-induced cell death of oral cancer cells through autophagy and apoptosis. Cancer cells were treated with hematoporphyrin at varying doses, followed by irradiation at 635 nm with an energy density of 5 mW/cm2. We determined the changes in HSP expression by determining the levels of PARP-1 and LC3II in PDT-resistant cells. Furthermore, we assessed cell death signaling after downregulating HSPs by transfecting specific siRNAs. We observed that PDT decreased HSP27 expression but increased HSP70 expression in the head and neck cancer cells. Treatment of cells with LC3II and PARP-1 inhibitors resulted in upregulation of HSP70 and HSP27 expression, respectively. Downregulation of HSP27 and HSP70 induced cell death and PDT resistance through autophagy and apoptosis. Moreover, downregulation of HSP27 in PDT-resistant cells resulted in enhanced survival. These results indicate that the regulation of HSP27 and HSP70 plays a principal role in increasing the effects of PDT by inducing autophagic and apoptotic cell death.

Inhibition of autophagy enhances cisplatin-induced apoptosis in the MG63 human osteosarcoma cell line

Autophagy is a significant catabolic process that allows the renewal of intracellular organelles, through which cells are able to maintain homeostasis. In addition, autophagy may be associated with the carcinogenesis of osteosarcoma (OS). Cisplatin (CDDP) is an alkylating agent that is commonly used as an anticancer therapy. However, the pathways underlying the effects of CDDP remain to be elucidated. The present study demonstrated that 3-methyladenine (3-MA), an inhibitor of autophagy, was able to increase the proliferation inhibition ratios of MG63 human OS cells when used in combination with CDDP. Furthermore, MG63 cells produced significantly more microtubule-associated protein light chain 3II (LC3II), a widely used marker for monitoring autophagy, following CDDP treatment. Treatment with 3-MA was observed to inhibit these changes. Similarly, MG63 cells co-treated with 3-MA and CDDP demonstrated increased sensitivity to CDDP-induced apoptosis, compared with those exposed to CDDP alone. The present study revealed variation in the expression of LC3II and caspase-3 activity following treatment with certain drugs. The results of the present study suggest that CDDP may be capable of inducing apoptosis and autophagy, and that autophagy may be able to inhibit apoptosis in MG63 cells. Therefore, downregulation of autophagy may increase the chemotherapeutic sensitivity of MG63 cells to CDDP.

Modulating polyplex-mediated gene transfection by small-molecule regulators of autophagy

Nonviral gene transfection mediated by cationic polymer/DNA polyplexes often imposes stress and toxicity to cells. To better understand the relationship between cellular stress responses and polyplex-mediated transfection, polyplex-induced early autophagy in mouse fibroblasts was characterized and the impact of autophagy modulation on transgene expression evaluated. Transmission electron microscopy revealed the formation of double-membraned autophagosome in the cytoplasm of polyplex-transfected cells. Immunofluorescence staining and microscopy revealed intracellular LC3 punctation that was characteristic of early autophagy activation. Elevated expression of autophagosome-associated LC3 II protein was also detected by Western blot. When cells were treated with small-molecule modulators of autophagy, polyplex-mediated gene transfection efficiency was significantly affected. 3-Methyladenine (3-MA), an early autophagy inhibitor, reduced transfection efficiency, whereas rapamycin, an autophagy inducer, enhanced transgene expression. Importantly, the observed functional impact on gene transfection by autophagy modulation was decoupled from that of other modes of cellular stress response (apoptosis/necrosis). Treatment of cells by 3-MA or rapamycin did not affect the level of intracellular reactive oxygen species (ROS) but did decrease or increase, respectively, nuclear localization of polyplex-delivered plasmid DNA. These findings suggest new possibilities of enhancing polyplex-mediated gene delivery by codelivery of small-molecule regulators of autophagy.

Apogossypolone inhibits the proliferation of LNCaP cells in vitro and in vivo

The aim of the present study was to investigate the anti-tumor effect of apogossypolone (ApoG2) on human LNCaP cells in vitro and in vivo. Cell viability was evaluated using an MTT assay. Cell autophagy and apoptosis were detected by flow cytometry and using a terminal deoxynucleotidyl transferase dUTP nick end labeling assay, respectively. Morphological autophagy alterations were observed by transmission electron microscopy. The formation of acidic vesicular organelles was assessed by acridine orange staining and fluorescence microscopy. Quantitative polymerase chain reaction (qPCR) was conducted to detect the expression levels of apoptosis-associated protein B-cell lymphoma 2 (Bcl-2) and Bak. The models of transplantation tumors in nude mice were established via subcutaneous injection of LNCaP cells. Growth of LNCaP cells was inhibited by ApoG2 treatment. Flow cytometry demonstrated that ApoG2 induced apoptosis in LNCaP cells. The Bcl-2 expression was decreased while Bak expression was increased. In addition, activation of cysteine aspartate protease (caspase)-3 and -8 was observed and 3-methyladenine (3-MA) enhanced apoptosis of LNCaP cells. Furthermore, nude mice treated with ApoG2 demonstrated a significant decrease in tumor volume and a significant increase in cell viability. Immunohistochemical analysis of tumor tissues demonstrated that ApoG2 enhanced caspase-3, -8, LC-3B and beclin-1 expression and reduced the expression of Bcl-2. ApoG2 was able to effectively suppress the growth of LNCaP cells through the induction of autophagy and apoptosis.

Autophagy promotes resistance to photodynamic therapy-induced apoptosis selectively in colorectal cancer stem-like cells

Recent studies have indicated that cancer stem-like cells (CSCs) exhibit a high resistance to current therapeutic strategies, including photodynamic therapy (PDT), leading to the recurrence and progression of colorectal cancer (CRC). In cancer, autophagy acts as both a tumor suppressor and a tumor promoter. However, the role of autophagy in the resistance of CSCs to PDT has not been reported. In this study, CSCs were isolated from colorectal cancer cells using PROM1/CD133 (prominin 1) expression, which is a surface marker commonly found on stem cells of various tissues. We demonstrated that PpIX-mediated PDT induced the formation of autophagosomes in PROM1/CD133⁺ cells, accompanied by the upregulation of autophagy-related proteins ATG3, ATG5, ATG7, and ATG12. The inhibition of PDT-induced autophagy by pharmacological inhibitors and silencing of the ATG5 gene substantially triggered apoptosis of PROM1/CD133⁺ cells and decreased the ability of colonosphere formation in vitro and tumorigenicity in vivo. In conclusion, our results revealed a protective role played by autophagy against PDT in CSCs and indicated that targeting autophagy could be used to elevate the PDT sensitivity of CSCs. These findings would aid in the development of novel therapeutic approaches for CSC treatment.

Acute spinal cord injury in rats should target activated autophagy

OBJECT

Autophagy is a cellular mechanism of maintaining balance between protein synthesis and degradation; the latter can be induced by starvation and neurodegenerative disease. Spinal cord injury (SCI) induces necrosis and apoptosis. Autophagic flux has not yet been defined, especially the potential role of autophagy in relation to apoptosis in different tissue cells. The object of this study was to investigate the occurrence of autophagic flux and the potential role of autophagy and apoptosis post-SCI in rats.

METHODS

Following creation of SCI in rats, activation of autophagic flux was detected at the protein (LC3, beclin1, and p62) and mRNA (beclin1) levels and on electron microscopy images. Distribution of LC3, colocalization of activated caspase-3, and changes in expression levels of bcl-2 and Bax were assessed to investigate the potential role of autophagy and apoptosis. Sprague-Dawley rats were used, and T9-10 hemitransection was performed. Expression levels of LC3, beclin1, p62, bcl-2, and Bax were assessed by Western blot analysis, and beclin1 mRNA levels were assessed by reverse transcription-polymerase chain reaction. Distribution of LC3 and colocalization of activated caspase-3 were analyzed by immunohistochemistry. Autophagosome formation was investigated by electron microscopy.

RESULTS

The authors found a dramatic elevation in LC3 and beclin1 levels near the scar region. Using double staining, they observed that upregulation of LC3 started at 4 hours in neurons and at 3 days in astrocytes after SCI. Confocal images indicated that the percentage of neurons with apoptosis was reduced, while the percentage of astrocytes with apoptosis was high at 4 hours, 8 hours, and 1 day post-SCI but decreased sharply at 3 days. Electron microscopy images provided evidence of autophagosome formation. Elimination of p62 indicated occurrence of autophagic flux. Expression levels of bcl-2 and Bax were increased and decreased, respectively, near the injury site.

CONCLUSIONS

The results of this research demonstrated that autophagic flux is activated after SCI. Potentially, inhibition of apoptosis could be a target to promote neural recovery.

Modelling the effect of GRP78 on anti-oestrogen sensitivity and resistance in breast cancer

Understanding the origins of resistance to anti-oestrogen drugs is of critical importance to many breast cancer patients. Recent experiments show that knockdown of GRP78, a key gene in the unfolded protein response (UPR), can re-sensitize resistant cells to anti-oestrogens, and overexpression of GRP78 in sensitive cells can cause them to become resistant. These results appear to arise from the operation and interaction of three cellular systems: the UPR, autophagy and apoptosis. To determine whether our current mechanistic understanding of these systems is sufficient to explain the experimental results, we built a mathematical model of the three systems and their interactions. We show that the model is capable of reproducing previously published experimental results and some new data gathered specifically for this paper. The model provides us with a tool to better understand the interactions that bring about anti-oestrogen resistance and the effects of GRP78 on both sensitive and resistant breast cancer cells.

Rosiglitazone protects against palmitate-induced pancreatic beta-cell death by activation of autophagy via 5'-AMP-activated protein kinase modulation

Promoting beta-cell survival is crucial for the prevention of beta-cell failure in diabetes. Thiazolidinediones, a widely used drug to improve insulin sensitivity in clinical practice, is found to have a protective effect on islet beta-cell. To date, the mechanism underlying the protective role of thiazolidinedione on beta-cell survival remain largely unknown. Activation of autophagy was detected by transmission electron microscopy, western blot, and GFP-LC3 transfection. Cell viability was examined by WST-8. Cell apoptosis was demonstrated by DAPI and Annexin V/PI staining. Colony formation assay was used to detect long-term cell viability. We demonstrated that rosiglitazone-treated beta-cells were more resistant to palmitate-induced apoptosis. The conversion of LC3-I to LC3-II and accumulated autophagosomes were found to be upregulated in rosiglitazone-treated cells. Inhibition of autophagy augmented palmitate-induced apoptosis with rosiglitazone treatment, suggesting that autophagy plays an important role in the survival function of rosiglitazone on beta-cells. Furthermore, we showed that rosiglitazone could induce AMP-activated protein kinase (AMPK) phosphorylation and reduce p70S6 kinase phosphorylation. Inhibition of AMPK impaired autophagy activation and enhanced palmitate-induced apoptosis during rosiglitazone treatment. These findings reveal that rosiglitazone-induced autophagy contributes to its protective function on beta-cells during palmitate treatment.

COX-Independent Mechanisms of Cancer Chemoprevention by Anti-Inflammatory Drugs

Epidemiological and clinical studies suggest that non-steroidal anti-inflammatory drugs (NSAIDs), including cyclooxygenase (COX)-2 selective inhibitors, reduce the risk of developing cancer. Experimental studies in human cancer cell lines and rodent models of carcinogenesis support these observations by providing strong evidence for the antineoplastic properties of NSAIDs. The involvement of COX-2 in tumorigenesis and its overexpression in various cancer tissues suggest that inhibition of COX-2 is responsible for the chemopreventive efficacy of these agents. However, the precise mechanisms by which NSAIDs exert their antiproliferative effects are still a matter of debate. Numerous other studies have shown that NSAIDs can act through COX-independent mechanisms. This review provides a detailed description of the major COX-independent molecular targets of NSAIDs and discusses how these targets may be involved in their anticancer effects. Toxicities resulting from COX inhibition and the suppression of prostaglandin synthesis preclude the long-term use of NSAIDs for cancer chemoprevention. Furthermore, chemopreventive efficacy is incomplete and treatment often leads to the development of resistance. Identification of alternative NSAID targets and elucidation of the biochemical processes by which they inhibit tumor growth could lead to the development of safer and more efficacious drugs for cancer chemoprevention.

Nanomaterials and autophagy: new insights in cancer treatment

Autophagy represents a cell’s response to stress. It is an evolutionarily conserved process with diversified roles. Indeed, it controls intracellular homeostasis by degradation and/or recycling intracellular metabolic material, supplies energy, provides nutrients, eliminates cytotoxic materials and damaged proteins and organelles. Moreover, autophagy is involved in several diseases. Recent evidences support a relationship between several classes of nanomaterials and autophagy perturbation, both induction and blockade, in many biological models. In fact, the autophagic mechanism represents a common cellular response to nanomaterials. On the other hand, the dynamic nature of autophagy in cancer biology is an intriguing approach for cancer therapeutics, since during tumour development and therapy, autophagy has been reported to trigger both an early cell survival and a late cell death. The use of nanomaterials in cancer treatment to deliver chemotherapeutic drugs and target tumours is well known. Recently, autophagy modulation mediated by nanomaterials has become an appealing notion in nanomedicine therapeutics, since it can be exploited as adjuvant in chemotherapy or in the development of cancer vaccines or as a potential anti-cancer agent. Herein, we summarize the effects of nanomaterials on autophagic processes in cancer, also considering the therapeutic outcome of synergism between nanomaterials and autophagy to improve existing cancer therapies.

Nutrient availability alters the effect of autophagy on sulindac sulfide-induced colon cancer cell apoptosis

Autophagy is a catabolic process by which a cell degrades its intracellular materials to replenish itself. Induction of autophagy under various cellular stress stimuli can lead to either cell survival or cell death via apoptotic and/or autophagic (nonapoptotic) pathways. The NSAID sulindac sulfide induces apoptosis in colon cancer cells. Here, we show that inhibition of autophagy under serum-deprived conditions resulted in significant reductions of sulindac sulfide-induced apoptosis in HT-29 colon cancer cells. In contrast, inhibition of autophagy under conditions where serum is available significantly increased sulindac sulfide-induced apoptosis in HT-29 cells. We previously showed that the apoptosis inhibitor, survivin, plays a role in regulating NSAID-induced apoptosis and autophagic cell death. Here, we show that survivin protein half-life is increased in the presence of autophagy inhibitors under serum-deprived conditions, but not under conditions when serum is available. Thus, the increased levels of survivin may be a factor contributing to inhibition of sulindac sulfide-induced apoptosis under serum-deprived conditions. These results suggest that whether a cell lives or dies due to autophagy induction depends on the balance of factors that regulate both autophagic and apoptotic processes.

Androgens promote prostate cancer cell growth through induction of autophagy

Androgens regulate both the physiological development of the prostate and the pathology of prostatic diseases. However, the mechanisms by which androgens exert their regulatory activities on these processes are poorly understood. In this study, we have determined that androgens regulate overall cell metabolism and cell growth, in part, by increasing autophagy in prostate cancer cells. Importantly, inhibition of autophagy using either pharmacological or molecular inhibitors significantly abrogated androgen-induced prostate cancer cell growth. Mechanistically, androgen-mediated autophagy appears to promote cell growth by augmenting intracellular lipid accumulation, an effect previously demonstrated to be necessary for prostate cancer cell growth. Further, autophagy and subsequent cell growth is potentiated, in part, by androgen-mediated increases in reactive oxygen species. These findings demonstrate a role for increased fat metabolism and autophagy in prostatic neoplasias and highlight the potential of targeting underexplored metabolic pathways for the development of novel therapeutics.

Role of melatonin in the regulation of autophagy and mitophagy: a review

Oxidative stress plays an essential role in triggering many cellular processes including programmed cell death. Proving a relationship between apoptosis and reactive oxygen species has been the goal of numerous studies. Accumulating data point to an essential role for oxidative stress in the activation of autophagy. The term autophagy encompasses several processes including not only survival or death mechanisms, but also pexophagy, mitophagy, ER-phagy or ribophagy, depending of which organelles are targeted for specific autophagic degradation. However, whether the outcome of autophagy is survival or death and whether the initiating conditions are starvation, pathogens or death receptors, reactive oxygen species are invariably involved. The role of antioxidants in the regulation of these processes, however, has been sparingly investigated. Among the known antioxidants, melatonin has high efficacy and, in both experimental and clinical situations, its protective actions against oxidative stress are well documented. Beneficial effects against mitochondrial dysfunction have also been described for melatonin; thus, this indoleamine seems to be linked to mitophagy. The present review focuses on data and the most recent advances related to the role of melatonin in health and disease, on autophagy activation in general, and on mitophagy in particular.

Lysosomal membrane protein TMEM192 deficiency triggers crosstalk between autophagy and apoptosis in HepG2 hepatoma cells

As constituents of lysosomes, lysosomal membrane proteins play important roles in lysosome-related autophagy and apoptosis. In a recent proteomic study of lysosomal proteins, we identified transmembrane protein 192 (TMEM192) as a novel lysosomal membrane protein candidate. Using specific anti-TMEM192 antibody and lysosomal markers, the lysosomal localization of TMEM192 was determined by immunofluorescence. TMEM192 shows a wide expression pattern in mouse tissues. Interestingly, TMEM192 was found to be highly expressed in tumor cell lines, while it was not expressed or was detected at low levels in normal cell lines. By knockdown of TMEM192 expression using specific siRNAs, we found that TMEM192-deficient HepG2 hepatoma cells show growth inhibition and increased apoptosis. Autophagy was shown to be activated through detection of LC3II expression. Increased apoptosis was inhibited by blocking the expression of the key autophagy gene Atg7 in TMEM192-deficient HepG2 cells. The results suggest that TMEM192 is important for tumor cell growth and proliferation. TMEM192 deficiency can induce autophagy in tumor cells, and can further activate apoptosis by the mitochondrial pathway through autophagy. TMEM192 promotion of autophagy may be a new route for tumor therapy.

P38 MAP kinase functions as a switch in MS-275-induced reactive oxygen species-dependent autophagy and apoptosis in human colon cancer cells

MS-275 is a synthetic benzamide derivative of the histone deacetylase inhibitor and is currently in phase I/II clinical trials. Many reports have shown that the anti-tumor activity of MS-275 in several types of cancer is mainly attributable to its capacity to induce the apoptotic death of tumor cells. It remains unclear if autophagy is involved in MS-275 treatment of cancer cells. Here, we first show that MS-275 induces human colon cancer cell HCT116 autophagy as well as apoptosis. Short-term treatment (24h) induced HCT116 cells to undergo autophagy with dependence on intracellular reactive oxygen species production and ERK activation. The activated reactive oxygen species/ERK signal promoted Atg7 protein expression, which triggered MS-275-induced cancer cell autophagy. However, after prolonged treatment with MS-275 (over 48h), autophagic cells turned apoptotic, which was also dependent on reactive oxygen species generation. Interestingly, we found that p38 MAP kinase played a vital role in the switch from autophagy to apoptosis in MS-275-induced human colon cancer cells. High expression of p38 induced cell autophagy, but low expression resulted in apoptosis. In addition, observations in vivo are strongly consistent with the in vitro results. Therefore, these findings extend our understanding of the action of MS-275 in inducing cancer cell death and suggest that it may be a promising clinical chemotherapeutic agent with multiple effects.

Autophagy in tumorigenesis and cancer therapy: Dr. Jekyll or Mr. Hyde?

Autophagy is an evolutionarily conserved mechanism for intracellular substance degradation, responsible for the recycling of metabolic substances and the maintenance of intracellular stability. It has early been demonstrated to play a significant role in tumorigenesis, but whether it acts as a promoter or a suppressor during tumorigenesis seems to be context-specific. Moreover, autophagy is also implicated in promoting chemoresistance of cancer cells so as to attenuate therapeutic efficacy of chemotherapy. On the contrary, other reports highlight a tumor-killing role of autophagy during cancer treatment. Herein, this review aims to revisit the key features of autophagy, summarize the seemingly contradictory roles of autophagy during both tumorigenesis and cancer chemotherapy, and evaluate the feasibility of altering the level of cellular autophagy as part of cancer adjuvant treatment.

Resveratrol enhances the therapeutic effect of temozolomide against malignant glioma in vitro and in vivo by inhibiting autophagy

The alkylating agent temozolomide (TMZ) is the major chemotherapeutic drug used clinically in the treatment of malignant gliomas. This study investigated the mechanism behind TMZ-induced cell death and the possibility that resveratrol might increase TMZ efficacy. TMZ induced both apoptotic cell death and cytoprotective autophagy through a reactive oxygen species (ROS) burst and extracellular signal-regulated kinase (ERK) activation, which was suppressed by resveratrol, resulting in a decrease in autophagy and an increase in apoptosis, suggesting that the ROS/ERK pathway plays a crucial role in the fate of cells after TMZ treatment. Isobolographic analysis indicated that the combination of TMZ and resveratrol has a synergistic effect. Moreover, an in vivo mouse xenograft study also showed that coadministration of resveratrol and TMZ reduced tumor volumes by suppressing ROS/ERK-mediated autophagy and subsequently inducing apoptosis. Taken together, our data indicate that TMZ-induced ROS/ERK-mediated autophagy protected glioma cells from apoptosis, and the combination of resveratrol with TMZ could improve the efficacy of chemotherapy for brain tumors.

Autophagy inhibited Ehrlich ascitic tumor cells apoptosis induced by the nitrostyrene derivative compounds: relationship with cytosolic calcium mobilization

Apoptosis induction is often associated with increased autophagy, indicating interplay between these two important cellular events in cell death and survival. In this study, the programmed cell death and autophagy induced by two nitrostyrene derivative compounds (NTS1 and NTS2) was studied using the tumorigenic Ehrlich ascitic tumor (EAT) cells. EAT cells were highly sensitive to NTS1 and NTS2 cytotoxicity in a dose-dependent manner. NTS1 and NTS2 IC(50) was less than 15.0μM post 12h incubation. Apoptosis was primarily induced by both compounds, as demonstrated by an increase in Annexin-V positive cells, concurrently with cytochrome c release from mitochondria to cytosol and caspase-3 activation. Although cytosolic Ca(2+) mobilization is involved in autophagy as well as apoptosis in response to cellular stress in many cancer cell types, from the two nitrostyrene derivative compounds studied, mainly NTS1 mobilized this ion and disparate autophagy in EAT cells. These results suggest that EAT induced cell death by NTS1 and NTS2 involved a Ca(2+)-dependent and a Ca(2+)-independent pathways, respectively. In accordance with these results, the treatment of EAT cells with 3 methyladenine (3-MA), an autophagy inhibitor; significantly increased the number of apoptotic cells after NTS1 treatment, suggesting that pharmacological modulation of autophagy augments the NTS1 efficacy. Thus, we denote the importance of studies involving autophagy and apoptosis during pre-clinical studies of new drugs with anticancer properties.

AMPK-mediated autophagy inhibits apoptosis in cisplatin-treated tumour cells

The role of autophagy in cisplatin anticancer action was investigated using human U251 glioma, rat C6 glioma and mouse L929 fibrosarcoma cell lines. A dose- and time-dependent induction of autophagy was observed in tumour cells following cisplatin treatment, as demonstrated by up-regulation of autophagy-inducing protein beclin-1 and subsequent appearance of acridine orange-stained acidic autophagic vesicles. The presence of autophagosomes in cisplatin-treated cells was also confirmed by electron microscopy. Inhibition of autophagy with lysosomal inhibitors bafilomycin A1 and chloroquine, or a PI3 kinase inhibitor wortmannin, markedly augmented cisplatin-triggered oxidative stress and caspase activation, leading to an increase in DNA fragmentation and apoptotic cell death. The mechanisms underlying the protective effect of autophagy apparently involved the interference with cisplatin-induced modulation of Bcl-2 family proteins, as inhibition of autophagy potentiated cisplatin-mediated up-regulation of proapoptotic Bax and down-regulation of anti-apoptotic Bcl-2. Autophagy induction in cisplatin-treated cells was preceded by activation of adenosine monophosphate-activated protein kinase (AMPK) and concomitant down-regulation of mammalian target of rapamycin (mTOR)-mediated phosphorylation of p70S6 kinase. The ability of cisplatin to trigger autophagy was reduced by small interfering RNA (siRNA)-mediated AMPK silencing, while transfection with mTOR siRNA was sufficient to trigger autophagy in tumour cells. Finally, siRNA-mediated AMPK down-regulation and AMPK inhibitor compound C increased cisplatin-induced tumour cell death, while mTOR siRNA and AMPK activator metformin protected tumour cells from cisplatin. Taken together, these data suggest that cisplatin-triggered activation of AMPK and subsequent suppression of mTOR activity can induce an autophagic response that protects tumour cells from cisplatin-mediated apoptotic death.

Compromising the unfolded protein response induces autophagy-mediated cell death in multiple myeloma cells

Objective

To determine whether the Unfolded Protein Response (UPR) sensors (PERK, ATF6 and IRE-1) can be targeted to promote death of Multiple Myeloma (MM) cells.

Methods

We have knocked-down separately each UPR stress sensor in human MM cell lines using RNA interference and followed MM cell death by monitoring the membrane, mitochondrial and nuclear alterations. Involvement of caspases in MM cell death consecutive to UPR sensor knock-down was analyzed by western blotting, measurement of their enzymatic activity using fluorigenic substrates and susceptibility to a pan-caspase inhibitor. Activation of the autophagic process was measured directly by detection of autophagosomes (electronic microscopy), monodansylcadaverine staining, production of the cleaved form of the microtubule-associated protein 1A/1B light chain 3 (LC3) and indirectly by analyzing the impact of pharmacological inhibitors of autophagy such as 3MA and bafilomycin A1.

Results

We show that extinction of a single UPR stress sensor (PERK) induces a non-apoptotic form of cell death in MM cells that requires autophagy for its execution. We also show that this cytotoxic autophagic process represses the apoptosis program by reducing the cytosolic release of the apoptogenic factors Smac/DIABLO and cytochrome c.

Interpretation

Altogether our findings suggest that autophagy can contribute to execution of death in mammalian cells that are exposed to mild ER stress. They also suggest that the autophagic process can regulate the intrinsic apoptotic pathway by inhibiting production of death effectors by the mitochondria, thus preventing formation of a functional apoptosome. Altogether these findings give credit to the idea that UPR sensors can be envisaged as therapeutic targets for the treatment of MM.

New paradigms in chronic intestinal inflammation and colon cancer: role of melatonin

In intestinal bowel disease (IBD), immune-mediated conditions exert their effects through various cells and proinflammatory mediators. Recent data support a participation of the endoplasmic reticulum stress and mitochondrial dysfunctions in IBD. Moreover, it is evident that chronic degenerative pathologies, including IBD, share comparable disease mechanisms with alteration in the autophagy mechanisms. Chronic inflammation in IBD exposes these patients to a number of signals known to have tumorigenic effects. This circuitry of inflammation and cancer modifies apoptosis and autophagy, and promotes cellular cycle progression, invasion, and angiogenesis. Melatonin has been shown as a specific antioxidant reducing oxidative damage in both lipid and aqueous cell environments. However, several studies provide further insight into the molecular mechanisms of melatonin action in the colon. In this line, recent data suggest that melatonin modulates autophagy and sirtuin activity. An anti-autophagic property of melatonin has been demonstrated, and it could contribute to its anti-oncogenic activity. Nevertheless, there is no information about whether antitumoral effects of melatonin on colon cancer are dependent on autophagy. Sirtuins have pleiotropic effects on cancer development, being reported both as facilitator and as suppressor of colon cancer development. Sirtuins and melatonin are connected through the circadian clock machinery, and melatonin seems able to correct the alterations in sirtuin activity associated with several pathological conditions. Autophagy and sirtuin activities are linked through 5'AMP-activated protein kinase (AMPK) activation, which switches on autophagy and increases sirtuin. The effect of melatonin on AMPK and the impact of this effect on IBD and colon cancer remain an open question.

Polyphenols from evening primrose ( Oenothera paradoxa ) defatted seeds induce apoptosis in human colon cancer Caco-2 cells

Polyphenols extracted from evening primrose seeds (industrial waste product) were studied as apoptosis inducers in human colorectal adenocarcinoma Caco-2 and HT-29 cell lines and in rat normal intestinal IEC-6 cells. The extract dose-dependently inhibited the growth of Caco-2, HT-29, and IEC-6 cells. However, nuclear DNA fragmentation characteristic of apoptosis was observed only in Caco-2. After 72 h of incubation with the extract at 150 μM gallic acid equivalents (44.1 μg extract/mL), Caco-2 cell numbers decreased to 19% of control and 48.8% of the cells were identified by flow cytometry as apoptotic. Under the same conditions only 8% of HT-29 cells and 12.6% of IEC-6 cells exhibited hypodiploid DNA content. The effects of the extract and its fractions on phosphatidylserine exposure and cell membrane integrity were assessed by high content screening image cytometry. The fractions strongly and dose-dependently reduced Caco-2 cell numbers, whereas HT-29 and IEC-6 cells were affected to lesser extents.

Enhancement of autophagy is a potential modality for tumors refractory to radiotherapy

Radiotherapy is a well-established treatment for cancer. However, the existence of radioresistant cells is one of the major obstacles in radiotherapy. In order to understand the mechanism of cellular radioresistance and develop more effective radiotherapy, we have established clinically relevant radioresistant (CRR) cell lines, which continue to proliferate under daily exposure to 2 Gray (Gy) of X-rays for >30 days. X-ray irradiation significantly induced autophagic cells in parental cells, which was exiguous in CRR cells, suggesting that autophagic cell death is involved in cellular radiosensitivity. An autophagy inducer, rapamycin sensitized CRR cells to the level of parental cells and suppressed cell growth. An autophagy inhibitor, 3-methyladenine induced radioresistance of parental cells. Furthermore, inhibition of autophagy by knockdown of Beclin-1 made parental cells radioresistant to acute radiation. These suggest that the suppression of autophagic cell death but not apoptosis is mainly involved in cellular radioresistance. Therefore, the enhancement of autophagy may have a considerable impact on the treatment of radioresistant tumor.

Regulation of autophagy in the heart: "you only live twice"

Autophagy is a highly orchestrated cellular process by which proteins and organelles are degraded via an elaborate lysosomal pathway to generate free amino acids and sugars for ATP during metabolic stress. At present, the exact role of autophagy in the heart is highly debated but suggested to play a key role in regulating cell turnover in cardiomyopathies and heart failure. The signaling pathways and molecular effectors that govern autophagy are incomplete, as are the mechanisms that determine whether autophagy promotes or prevents cell death. The mitochondrion has been identified as a key organelle centrally involved in regulating autophagy. Certain members of the Bcl-2 gene family, including Beclin-1, Bcl-2 nineteen kilodaltons interacting protein (Bnip3), and Nix/Bnip3L, provoke mitochondrial perturbations leading to permeability transition pore opening, resulting in apoptosis, autophagy, or both. These and other aspects of autophagy processes have been discussed.

At the core of survival: autophagy delays the onset of both apoptotic and necrotic cell death in a model of ischemic cell injury

Ischemic cell injury leads to cell death. Three main morphologies have been described: apoptosis, cell death with autophagy and necrosis. Their inherent dynamic nature, a point of no return (PONR) and molecular overlap have been stressed. The relationship between a defined cell death type and the severity of injury remains unclear. The functional role of autophagy and its effects on cell death onset is largely unknown. In this study we report a differential induction of cell death, which is dependent on the severity and duration of an ischemic insult. We show that mild ischemia leads to the induction of autophagy and apoptosis, while moderate or severe ischemia induces both apoptotic and necrotic cell death without increased autophagy. The autophagic response during mild injury was associated with an ATP surge. Real-time imaging and Fluorescence Resonance Energy Transfer (FRET) revealed that increased autophagy delays the PONR of both apoptosis and necrosis significantly. Blocking autophagy shifted PONR to an earlier point in time. Our results suggest that autophagic activity directly alters intracellular metabolic parameters, responsible for maintaining mitochondrial membrane potential and cellular membrane integrity. A similar treatment also improved functional recovery in the perfused rat heart. Taken together, we demonstrate a novel finding: autophagy is implicated only in mild injury and positions the PONR in cell death.

Mevalonate cascade regulation of airway mesenchymal cell autophagy and apoptosis: a dual role for p53

Statins inhibit the proximal steps of cholesterol biosynthesis, and are linked to health benefits in various conditions, including cancer and lung disease. We have previously investigated apoptotic pathways triggered by statins in airway mesenchymal cells, and identified reduced prenylation of small GTPases as a primary effector mechanism leading to p53-mediated cell death. Here, we extend our studies of statin-induced cell death by assessing endpoints of both apoptosis and autophagy, and investigating their interplay and coincident regulation. Using primary cultured human airway smooth muscle (HASM) and human airway fibroblasts (HAF), autophagy, and autophagosome formation and flux were assessed by transmission electron microscopy, cytochemistry (lysosome number and co-localization with LC3) and immunoblotting (LC3 lipidation and Atg12-5 complex formation). Chemical inhibition of autophagy increased simvastatin-induced caspase activation and cell death. Similarly, Atg5 silencing with shRNA, thus preventing Atg5-12 complex formation, increased pro-apoptotic effects of simvastatin. Simvastatin concomitantly increased p53-dependent expression of p53 up-regulated modulator of apoptosis (PUMA), NOXA, and damage-regulated autophagy modulator (DRAM). Notably both mevalonate cascade inhibition-induced autophagy and apoptosis were p53 dependent: simvastatin increased nuclear p53 accumulation, and both cyclic pifithrin-α and p53 shRNAi partially inhibited NOXA, PUMA expression and caspase-3/7 cleavage (apoptosis) and DRAM expression, Atg5-12 complex formation, LC3 lipidation, and autophagosome formation (autophagy). Furthermore, the autophagy response is induced rapidly, significantly delaying apoptosis, suggesting the existence of a temporally coordinated p53 regulation network. These findings are relevant for the development of statin-based therapeutic approaches in obstructive airway disease.

Autophagy as a therapeutic target in cancer

Autophagy is a self-catabolic process that maintains intracellular homeostasis and prolongs cell survival under stress via lysosomal degradation of cytoplasmic constituents and recycling of amino acids and energy. Autophagy is intricately involved in many aspects of human health and disease, including cancer. Autophagy is a double-edged sword in tumorigenesis, acting both as a tumor suppressor and a protector of cancer cell survival, and elucidation of its exact role at different stages of cancer progression and in treatment responsiveness is a complex and challenging task. Better understanding of autophagy regulation and its impact on treatment outcome will potentially allow us to identify novel therapeutic targets in cancer. In this review, we summarize current knowledge on the regulation and dual function of autophagy in tumorigenesis, as well as ongoing efforts in modulating autophagy for cancer treatment and prevention. This is a very exciting and highly promising area of cancer research, as pharmacologic modulation of autophagy appears to augment the efficacy of currently available anticancer regimens and opens the way to the development of new combinatorial therapeutic strategies that will hopefully contribute to cancer eradication.

Caspase dependence of the death of neonatal retinal ganglion cells induced by axon damage and induction of autophagy as a survival mechanism

We examined the degeneration of post-mitotic ganglion cells in ex-vivo neonatal retinal explants following axon damage. Ultrastructural features of both apoptosis and autophagy were detected. Degenerating cells reacted with antibodies specific for activated caspase-3 or -9, consistent with the presence of caspase activity. Furthermore, peptidic inhibitors of caspase-9, -6 or -3 prevented cell death (100 µM Ac-LEDH-CHO, 50 µM Ac-VEID-CHO and 10 µM Z-DEVD-fmk, respectively). Interestingly, inhibition of autophagy by 7-10 mM 3-methyl-adenine increased the rate of cell death. Immunohistochemistry data, caspase activation and caspase inhibition data suggest that axotomy of neonatal retinal ganglion cells triggers the intrinsic apoptotic pathway, which, in turn, is counteracted by a pro-survival autophagic response, demonstrated by electron microscopy profiles and pharmacological autophagy inhibitor.