Inhibition of autophagy enhances anticancer effects of bevacizumab in hepatocarcinoma

Tumor-derived lactate promotes resistance to bevacizumab treatment by facilitating autophagy enhancer protein RUBCNL expression through histone H3 lysine 18 lactylation (H3K18la) in colorectal cancer

Bevacizumab plays an important role in the first and second line treatment for metastatic colorectal cancer (CRC). And induction of hypoxia and the tumors response to it plays an important role in determining the efficacy of antiangiogenic therapy while the connection between them remains unclear. Here, we found that lactate accumulated in the tumor environment of CRC and acted as substrates for histone lactylation, and this process was further induced by cellular enhanced glycolysis in hypoxia. We determined that CRC patients resistant to bevacizumab treatment presented with elevated levels of histone lactylation and inhibition of histone lactylation efficiently suppressed CRC tumorigenesis, progression and survival in hypoxia. Histone lactylation promoted the transcription of RUBCNL/Pacer, facilitating autophagosome maturation through interacting with BECN1 (beclin 1) and mediating the recruitment and function of the class III phosphatidylinositol 3-kinase complex, which had a crucial role in hypoxic cancer cells proliferation and survival. Moreover, combining inhibition of histone lactylation and macroautophagy/autophagy with bevacizumab treatment demonstrated remarkable treatment efficacy in bevacizumab-resistance patients-derived pre-clinical models. These findings delivered a new exploration and important supplement of metabolic reprogramming-epigenetic regulation, and provided a new strategy for improving clinical efficacy of bevacizumab in CRC by inhibition of histone lactylation.Abbreviations: 2-DG: 2-deoxy-D-glucose; BECN1: beclin 1; CQ: chloroquine; CRC: colorectal cancer; DMOG: dimethyloxalylglycine; H3K18la: histone H3 lysine 18 lactylation; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; Nala: sodium lactate; PDO: patient-derived orgnoid; PDX: patient-derived xenograft; RUBCNL/Pacer: rubicon like autophagy enhancer; SQSTM1/p62: sequestosome 1.

ROS in hepatocellular carcinoma: What we know

Hepatocellular carcinoma (HCC), which is a primary liver cancer subtype, has a poor prognosis due to its high degree of malignancy. The lack of early diagnosis makes systemic therapy the only hope for HCC patients with advanced disease; however, resistance to drugs is a major obstacle. In recent years, targeted molecular therapy has gained popularity as a potential treatment for HCC. An increase in reactive oxygen species (ROS), which are cancer markers and a potential target for HCC therapy, can both promote and inhibit the disease. At present, many studies have examined targeted regulation of ROS in the treatment of HCC. Here, we reviewed the latest drugs that are still in the experimental stage, including nanocarrier drugs, exosome drugs, antibody drugs, aptamer drugs and polysaccharide drugs, to provide new hope for the clinical treatment of HCC patients.

Autophagy: A challengeable paradox in cancer treatment

OBJECTIVE

Autophagy is an intracellular degradation pathway conserved in all eukaryotes from yeast to humans. This process plays a quality-control role by destroying harmful cellular components under normal conditions, maintaining cell survival, and establishing cellular adaptation under stressful conditions. Hence, there are various studies indicating dysfunctional autophagy as a factor involved in the development and progression of various human diseases, including cancer. In addition, the importance of autophagy in the development of cancer has been highlighted by paradoxical roles, as a cytoprotective and cytotoxic mechanism. Despite extensive research in the field of cancer, there are many questions and challenges about the roles and effects suggested for autophagy in cancer treatment. The aim of this study was to provide an overview of the paradoxical roles of autophagy in different tumors and related cancer treatment options.

METHODS

In this study, to find articles, a search was made in PubMed and Google scholar databases with the keywords Autophagy, Autophagy in Cancer Management, and Drug Design.

RESULTS

According to the investigation, some studies suggest that several advanced cancers are dependent on autophagy for cell survival, so when cancer cells are exposed to therapy, autophagy is induced and suppresses the anti-cancer effects of therapeutic agents and also results in cell resistance. However, enhanced autophagy from using anti-cancer drugs causes autophagy-mediated cell death in several cancers. Because autophagy also plays roles in both tumor suppression and promotion further research is needed to determine the precise mechanism of this process in cancer treatment.

CONCLUSION

We concluded in this article, autophagy manipulation may either promote or hinder the growth and development of cancer according to the origin of the cancer cells, the type of cancer, and the behavior of the cancer cells exposed to treatment. Thus, before starting treatment it is necessary to determine the basal levels of autophagy in various cancers.

Nanotherapeutics in autophagy: a paradigm shift in cancer treatment

Autophagy is a catabolic process in which an organism responds to its nutrient or metabolic emergencies. It involves the degradation of cytoplasmic proteins and organelles by forming double-membrane vesicles called "autophagosomes." They sequester cargoes, leading them to degradation in the lysosomes. Although autophagy acts as a protective mechanism for maintaining homeostasis through cellular recycling, it is ostensibly a cause of certain cancers, but a cure for others. In other words, insufficient autophagy, due to genetic or cellular dysfunctions, can lead to tumorigenesis. However, many autophagy modulators are developed for cancer therapy. Diverse nanoparticles have been documented to induce autophagy. Also, the highly stable nanoparticles show blockage to autophagic flux. In this review, we revealed a general mechanism by which autophagy can be induced or blocked via nanoparticles as well as several studies recently performed to prove the stated fact. In addition, we have also elucidated the paradoxical roles of autophagy in cancer and how their differential role at different stages of various cancers can affect its treatment outcomes. And finally, we summarize the breakthroughs in cancer disease treatments by using metallic, polymeric, and liposomal nanoparticles as potent autophagy modulators.

Myricetin Induces Apoptosis and Protective Autophagy through Endoplasmic Reticulum Stress in Hepatocellular Carcinoma

Myricetin, a natural flavonoid, exhibits diverse biological activities, including antitumor effects. The present study aimed to investigate the effects of myricetin on hepatocellular carcinoma (HCC) cells and explore the underlying molecular mechanisms. Our results showed that myricetin significantly inhibited cell proliferation and induced apoptosis in HCC cells. The apoptosis induced by myricetin was associated with the activation of endoplasmic reticulum (ER) stress. In addition, autophagy was enhanced in response to ER stress. Inhibition of autophagy by RNA interference or chemical inhibitors resulted in increased apoptosis in myricetin-treated HCC cells. The in vivo experiment also showed that myricetin effectively reduced tumor growth in an HCC xenograft model and that combination treatment with an autophagy inhibitor significantly enhanced this effect. These results indicated that myricetin induced apoptosis in HCC cells through the activation of ER stress. Protective autophagy was also upregulated during this process. Simultaneous inhibition of autophagy enhanced the anti-HCC activity of myricetin. Myricetin might be a promising drug candidate for HCC therapy, and the combined use of myricetin with autophagy inhibitors could be an effective therapeutic strategy.

Naturally Occurring Antioxidant Therapy in Alzheimer’s Disease

It is estimated that the prevalence rate of Alzheimer’s disease (AD) will double by the year 2040. Although currently available treatments help with symptom management, they do not prevent, delay the progression of, or cure the disease. Interestingly, a shared characteristic of AD and other neurodegenerative diseases and disorders is oxidative stress. Despite profound evidence supporting the role of oxidative stress in the pathogenesis and progression of AD, none of the currently available treatment options address oxidative stress. Recently, attention has been placed on the use of antioxidants to mitigate the effects of oxidative stress in the central nervous system. In preclinical studies utilizing cellular and animal models, natural antioxidants showed therapeutic promise when administered alone or in combination with other compounds. More recently, the concept of combination antioxidant therapy has been explored as a novel approach to preventing and treating neurodegenerative conditions that present with oxidative stress as a contributing factor. In this review, the relationship between oxidative stress and AD pathology and the neuroprotective role of natural antioxidants from natural sources are discussed. Additionally, the therapeutic potential of natural antioxidants as preventatives and/or treatment for AD is examined, with special attention paid to natural antioxidant combinations and conjugates that are currently being investigated in human clinical trials.

Blockade of Uttroside B-Induced Autophagic Pro-Survival Signals Augments Its Chemotherapeutic Efficacy Against Hepatocellular Carcinoma

Our previous study has demonstrated that Uttroside B (Utt-B), a saponin isolated from the leaves of Solanum nigrum Linn induces apoptosis in hepatic cancer cells and exhibits a remarkable growth inhibition of Hepatocellular Carcinoma (HCC). Our innovation has been granted a patent from the US (US 2019/0160088A1), Canada (3,026,426.), Japan (JP2019520425) and South Korea (KR1020190008323) and the technology have been transferred commercially to Q Biomed, a leading US-based Biotech company. Recently, the compound received approval as 'Orphan Drug' against HCC from US FDA, which reveals the clinical relevance of evaluating its antitumor efficacy against HCC. In the present study, we report that Utt-B promotes pro-survival autophagy in hepatic cancer cells as evidenced by the increased expression of autophagy-related proteins, including LC3-II, Beclin1, ATG 5, and ATG 7, as well as a rise in the autophagic flux. Hence, we investigated whether Utt-B-induced autophagic response is complementing or contradicting its apoptotic program in HCC. Inhibition of autophagy using the pharmacological inhibitors, Bafilomycin A1(Baf A1), and 3-methyl adenine (3-MA), and the biological inhibitor, Beclin1 siRNA, significantly enhances the apoptosis of hepatic cancer cells and hence the cytotoxicity induced by Utt-B. We also found increased expression of autophagy markers in Utt-B-treated xenografts derived from HCC. We further analyzed whether the antimalarial drug, Chloroquine (Cqn), a well-known autophagy inhibitor, can enhance the anticancer effect of Utt-B against HCC. We found that inhibition of autophagy using Cqn significantly enhances the antitumor efficacy of Utt-B in vitro and in vivo, in NOD SCID mice bearing HCC xenografts. Taken together, our results suggest that the antitumor effect of Utt-B against HCC can be further enhanced by blocking autophagy. Furthermore, Utt-B in combination with Cqn, a clinically approved drug, if repurposed and used in a combinatorial regimen with Utt-B, can further improve the therapeutic efficacy of Utt-B against HCC.

Dichloroacetate enhances the anti-tumor effect of sorafenib via modulating the ROS-JNK-Mcl-1 pathway in liver cancer cells

Liver cancer is one of the most common and high recurrence malignancies. Besides radiotherapy and surgery, chemotherapy also plays an essential role in the treatment of liver cancer. Sorafenib and sorafenib-based combination therapies have been proven efficacy against tumors. However, previous clinical studies have indicated that some patients with liver cancer are resistant to sorafenib treatment and the existing strategies are not satisfactory in the clinic. Therefore, it is urgent to investigate strategies to improve the effectiveness of sorafenib for liver cancer and to explore effective drug combinations. In the present study, we found that dichloroacetate (DCA) could significantly enhance the anti-tumor effect of sorafenib on liver cancer cells, including reduced viability and dramatically promoted apoptosis in liver cancer cells. Moreover, compared to sorafenib alone, the combination of DCA and sorafenib markedly increased the degradation of anti-apoptotic protein Mcl-1 by enhancing its phosphorylation. Overexpression of Mcl-1 could significantly attenuate the synergetic effect of DCA and sorafenib on apoptosis induction in liver cancer cells. Furthermore, we found that the ROS-JNK pathway was obviously activated in the DCA combined sorafenib group. The levels of ROS and p-JNK were dramatically up-regulated in the two drug combination groups. Antioxidant NAC could alleviate the synergetic effects of DCA and sorafenib on ROS generation, JNK activation, Mcl-1 degradation, and cell apoptosis. Moreover, DCA and sorafenib's effects on Mcl-1 degradation and apoptosis could also be inhibited by JNK inhibitor 'SP'600125. Finally, the synergetic effects of DCA and sorafenib on tumor growth suppression, Mcl-1 degradation and induction of apoptosis were also validated in liver cancer xenograft in vivo. These findings indicate that DCA enhances the anti-tumor effect of sorafenib via the ROS-JNK-Mcl-1 pathway in liver cancer cells. This study may provide new insights to improve the chemotherapeutic effect of sorafenib, which may be beneficial for further clinical application of sorafenib in liver cancer treatment.

Different effects of anti-VEGF drugs (Ranibizumab, Aflibercept, Conbercept) on autophagy and its effect on neovascularization in RF/6A cells

INTRODUCTION

Choroidal neovascularization (CNV) is the main pathological change of wet age-related macular degeneration. Anti-VEGF drugs are the most commonly used treatment for CNV. The biggest drawback of anti-VEGF drugs is the recurrence of CNV, which requires repeated therapy several times. Autophagy activation may be involved in reducing the therapeutic effect of anti-VEGF drugs. So, this study aims to elucidate the effect and mechanism of anti-VEGF drugs on endothelial autophagy and neovascularization in vitro.

METHODS

RF/6A cells were randomly divided into five groups: The control group, hypoxia group (1% O₂, 5% CO₂, 94% N₂), anti-VEGF group (group1: Ranibizumab 100 μg/ml; group2: Aflibercept, 400 μg/ml; group3: Conbercept, 100 μg/ml). Autophagy-related proteins were examined by Western blot. RFP-GFP-LC3 was used to detect autophagy and autophagic flow. Subsequently, we used autophagy inhibitors (3-MA or CQ) to inhibit Conbercept induced autophagy and to observe its effect on angiogenesis in vitro. Proliferation, migration, and tube formation of endothelial cells can be used to study neovascularization in vitro. In this research, the CCK-8 assay was used to detect cell proliferation. Cell migration and tube formation were assessed by wound assay and matrix method, respectively. Flow cytometry and Tunel were used to detect cell apoptosis. Finally, the mechanism of Conbercept activated autophagy was studied. Western blot was used to detect the expression of p53 and DRAM (damage-regulated autophagy modulator), upstream activators of autophagy.

RESULTS

The protein levels of Beclin-1 and LC3-2/1 in Ranibizumab and Conbercept groups were significantly higher than in the hypoxia group(P < 0.05). While the expression of P62 was decreased (P < 0.05). The autophagic flux was showed the same results. However, Aflibercept showed the opposite effect on autophagy. Compared with the Conbercept group, autophagy inhibitor 3-MA or CQ can further inhibit cell proliferation and promotes cell apoptosis (P < 0.05). Conbercept significantly inhibited cell migration compared with the hypoxia group (633.08 ± 72.52 vs. 546.33 ± 24.61), while the autophagy inhibitor group (3-MA or CQ) had a more obvious inhibition effect (309.75 ± 86.36 and 263.33 ± 68.67) (P < 0.05). For tube formation, the number of tube formation was decreased significantly in the Conbercept group (32.00 ± 2.00) compared to the hypoxia group (39.00 ± 1.53) and even further reduced in 3-MA or CQ group (24.00 ± 3.61, 20.00 ± 2.65). The length of master segments in the hypoxia group was 15,668.00 ± 894.11. It was decreased in Conbercept (13,885.34 ± 730.03). In 3-MA or CQ group, the length of master segments dropped further (11,997.00 ± 433.66, 10,617.67 ± 543.21). Compare with the hypoxia group, the expression P53 and DRAM were increased in the Conbercept group (P < 0.05). Autophagy-related proteins LC-3, Beclin-1, and DRAM were inhibited by P53 inhibitor Pifithrin-α (PFTα) (P < 0.05).

CONCLUSION

Ranibizumab and Conbercept can trigger the autophagy of vascular endothelial cells while Aflibercept can inhibit it. The combination of Conbercept and autophagy inhibitor can significantly inhibit the formation of angiogenesis in vitro. The mechanism of autophagy activation is related to the activation of the p53/DRAM pathway.

Autophagy deficiency downregulates O6methylguanine-DNA methyltransferase and increases chemosensitivity of liver cancer cells

It is known that autophagy-deficient cells are prone to DNA damage, but the specific role of autophagy in DNA damage repair is not fully known. Here, we show that autophagy-deficient liver cancer cells exhibit increased DNA damage caused by the chemotherapeutic agent epirubicin. Autophagy deficiency promotes downregulation of the DNA repair enzyme O⁶methylguanine-DNA methyltransferase (MGMT) in liver cancer cells. However, autophagy induction with epirubicin had no impact on MGMT gene or protein expression in liver cancer cells. In the absence of autophagy, the chemosensitivity of liver cancer cells was increased, but this was reversed by MGMT overexpression, indicating that autophagy mediates resistance to chemotherapy in liver cancer cells via MGMT. These findings demonstrate a direct link between autophagy, MGMT, and DNA damage repair in liver cancer cells, and show that MGMT not only regulates chemosensitivity to alkylating agents, but may also be involved in other DNA damage repair processes in autophagy-deficient cells.

Novel Ferrocene Derivatives Induce G0/G1 Cell Cycle Arrest and Apoptosis through the Mitochondrial Pathway in Human Hepatocellular Carcinoma

In this study, detailed information on hepatocellular carcinoma (HCC) cells (HepG-2, SMMC-7721, and HuH-7) and normal human liver cell L02 treated by ferrocene derivatives (compounds 1, 2 and 3) is provided. The cell viability assay showed that compound 1 presented the most potent and selective anti-HCC activity. Further mechanism study indicated that the proliferation inhibition effect of compound 1 was associated with the cycle arrest at the G0/G1 phase and downregulation of cyclin D1/CDK4. Moreover, compound 1 could induce apoptosis in HCC cells by loss of mitochondrial membrane potential (ΔΨm), accumulation of reactive oxygen species (ROS), decrease in Bcl-2, increase in BAX and Bad, translocation of Cytochrome c, activation of Caspase-9, -3, and cleavage of PARP. These results indicated that compound 1 would be a promising candidate against HCC through G0/G1 cell cycle arrest-related proliferation inhibition and mitochondrial pathway-dependent apoptosis.

Combining Everolimus and Ku0063794 Promotes Apoptosis of Hepatocellular Carcinoma Cells via Reduced Autophagy Resulting from Diminished Expression of miR-4790-3p

It is challenging to overcome the low response rate of everolimus in the treatment of patients with hepatocellular carcinoma (HCC). To overcome this challenge, we combined everolimus with Ku0063794, the inhibitor of mTORC1 and mTORC2, to achieve higher anticancer effects. However, the precise mechanism for the synergistic effects is not clearly understood yet. To achieve this aim, the miRNAs were selected that showed the most significant variation in expression according to the mono- and combination therapy of everolimus and Ku0063794. Subsequently, the roles of specific miRNAs were determined in the processes of the treatment modalities. Compared to individual monotherapies, the combination therapy significantly reduced viability, increased apoptosis, and reduced autophagy in HepG2 cells. The combination therapy led to significantly lower expression of miR-4790-3p and higher expression of zinc finger protein225 (ZNF225)—the predicted target of miR-4790-3p. The functional study of miR-4790-3p and ZNF225 revealed that regarding autophagy, miR-4790-3p promoted it, while ZNF225 inhibited it. In addition, regarding apoptosis, miR-4790-3p inhibited it, while ZNF225 promoted it. It was also found that HCC tissues were characterized by higher expression of miR-4790-3p and lower expression of ZNF225; HCC tissues were also characterized by higher autophagic flux. We, thus, conclude that the potentiated anticancer effect of the everolimus and Ku0063794 combination therapy is strongly associated with reduced autophagy resulting from diminished expression of miR-4790-3p, as well as higher expression of ZNF225.

A novel hypoxia gene signature indicates prognosis and immune microenvironments characters in patients with hepatocellular carcinoma

Due to the lack of a suitable gene signature, it is difficult to assess the hypoxic exposure of HCC tissues. The clinical value of assessing hypoxia in HCC is short of tissue‐level evidence. We tried to establish a robust and HCC‐suitable hypoxia signature using microarray analysis and a robust rank aggregation algorithm. Based on the hypoxia signature, we obtained a hypoxia‐associated HCC subtypes system using unsupervised hierarchical clustering and a hypoxia score system was provided using gene set variation analysis. A novel signature containing 21 stable hypoxia‐related genes was constructed to effectively indicate the exposure of hypoxia in HCC tissues. The signature was validated by qRT‐PCR and compared with other published hypoxia signatures in multiple large‐size HCC cohorts. The subtype of HCC derived from this signature had different prognosis and other clinical characteristics. The hypoxia score obtained from the signature could be used to indicate clinical characteristics and predict prognoses of HCC patients. Moreover, we reveal a landscape of immune microenvironments in patients with different hypoxia score. In conclusion, we identified a novel HCC‐suitable 21‐gene hypoxia signature that could be used to estimate the hypoxia exposure in HCC tissues and indicated prognosis and a series of important clinical features in HCCs. It may enable the development of personalized counselling or treatment strategies for HCC patients with different levels of hypoxia exposure.

Hypoxia-Induced Autophagy Enhances Cisplatin Resistance in Human Bladder Cancer Cells by Targeting Hypoxia-Inducible Factor-1α

Purpose

To investigate the effect of hypoxia on chemoresistance and the underlying mechanism in bladder cancer cells.

Methods

BIU-87 bladder cancer cell line was treated with cisplatin under hypoxic and normoxic conditions and tested using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and Western blotting. All the data were expressed as mean ± standard error from three independent experiments and analyzed by multiple t-tests.

Results

Apoptosis of bladder cancer cells caused by cisplatin was attenuated in hypoxic conditions. Hypoxia enhanced autophagy caused by cisplatin. The autophagy inhibitor and HIF-1α inhibitor can reverse the chemoresistance in hypoxic condition. Apoptosis and autophagy of bladder cancer cells were downregulated by HIF-1α inhibitor YC-1. Hypoxia-induced autophagy enhanced chemoresistance to cisplatin via the HIF-1 signaling pathway.

Conclusion

Resistance to cisplatin in BIU-87 bladder cancer cells under hypoxic conditions can be explained by activation of autophagy, which is regulated by HIF-1α-associated signaling pathways. The hypoxia–autophagy pathway may be a target for improving the efficacy of cisplatin chemotherapy in bladder cancer.

Antiangiogenic effect of arsenic trioxide in HUVECs by FoxO3a-regulated autophagy

Arsenic trioxide (ATO) has been shown to have antitumor effect in different tumors, although the underlying mechanisms are not fully understood. Autophagy plays a critical role in tumorigenesis and cancer therapy and has been found to be activated by ATO in different cells. However, the role of autophagy in the antitumor effect of ATO has not yet been elucidated. In this study, we investigated the role of autophagy in the antiangiogenic effect of ATO in human umbilical vein endothelial cells (HUVECs) in vitro and its underlying mechanism. Our data showed that ATO suppresses angiogenesis and induces autophagy in HUVECs through upregulation of forkhead box protein O3 (FoxO3a). Co-incubated with autophagy inhibitor or knockdown of FoxO3a effectively inhibited ATO-induced autophagy and reversed the antiangiogenic effect of ATO, indicating that ATO-induced autophagy plays an antiangiogenic role in HUVECs. Our results highlight the importance of autophagy in the antiangiogenic effect of ATO and provide an improved understanding of the function of ATO.

The Emerging Roles of Exosomes in the Chemoresistance of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common gastrointestinal malignancy with a leading incidence of cancer-related mortality worldwide. Despite the progress of treatment options, there remains low efficacy for patients with intermediate-advanced HCC, due to tumor metastasis, recurrence and chemoresistance. Increasing evidence suggests that exosomes in the tumor microenvironment (TME), along with other extracellular vesicles (EVs) and cytokines, contribute to the drug chemosensitivity of cancer cells. Exosomes, the intercellular communicators in various biological activities, have shown to play important roles in HCC progression. This review summarizes the underlying associations between exosomes and chemoresistance of HCC cells. The exosomes derived from distinct cell types mediate the drug resistance by regulating drug efflux, epithelial-mesenchymal transition (EMT), cancer stem cell (CSC) properties, autophagic phenotypes, as well as the immune response. In summary, TME-related exosomes can be a potential target to reverse chemoresistance and a candidate biomarker of drug efficacy in HCC patients.

Adaptive response of resistant cancer cells to chemotherapy

Despite advances in cancer therapeutics and the integration of personalized medicine, the development of chemoresistance in many patients remains a significant contributing factor to cancer mortality. Upon treatment with chemotherapeutics, the disruption of homeostasis in cancer cells triggers the adaptive response which has emerged as a key resistance mechanism. In this review, we summarize the mechanistic studies investigating the three major components of the adaptive response, autophagy, endoplasmic reticulum (ER) stress signaling, and senescence, in response to cancer chemotherapy. We will discuss the development of potential cancer therapeutic strategies in the context of these adaptive resistance mechanisms, with the goal of stimulating research that may facilitate the development of effective cancer therapy.

Spermidine endows macrophages anti-inflammatory properties by inducing mitochondrial superoxide-dependent AMPK activation, Hif-1α upregulation and autophagy

Distinct metabolic programs, either energy-consuming anabolism or energy-generating catabolism, were required for different biological functions. Macrophages can adopt different immune phenotypes in response to various cues and exhibit anti- or pro-inflammatory properties relying on catabolic pathways associated with oxidative phosphorylation (OXPHOS) or glycolysis. Spermidine, a natural polyamine, has been reported to regulate inflammation through inducing anti-inflammatory (M2) macrophages. However, the underlying mechanisms remain elusive. We show here that the M2-polarization induced by spermidine is mediated by mitochondrial reactive oxygen species (mtROS). The levels of mitochondrial superoxide and H₂O₂ were markedly elevated by spermidine. Mechanistically, mtROS were found to activate AMP-activated protein kinase (AMPK), which in turn enhanced mitochondrial function. Furthermore, hypoxia-inducible factor-1α (Hif-1α) was upregulated by the AMPK activation and mtROS and was required for the expression of anti-inflammatory genes and induction of autophagy. Consistent with previous report that autophagy is required for the M2 polarization, we found that the M2 polarization induced by spermidine was also mediated by increased autophagy. The macrophages treated with spermidine in vitro were found to ameliorate Dextran Sulfate Sodium (DSS)-induced inflammatory bowel disease (IBD) in mice. Thus, spermidine can elicit an anti-inflammatory program driven by mtROS-dependent AMPK activation, Hif-1α stabilization and autophagy induction in macrophages. Our studies revealed a critical role of mtROS in shaping macrophages into M2-like phenotype and provided novel information for management of inflammatory disease by spermidine.

Targeting autophagy to overcome drug resistance: further developments

Inhibiting cell survival and inducing cell death are the main approaches of tumor therapy. Autophagy plays an important role on intracellular metabolic homeostasis by eliminating dysfunctional or unnecessary proteins and damaged or aged cellular organelles to recycle their constituent metabolites that enable the maintenance of cell survival and genetic stability and even promotes the drug resistance, which severely limits the efficacy of chemotherapeutic drugs. Currently, targeting autophagy has a seemingly contradictory effect to suppress and promote tumor survival, which makes the effect of targeting autophagy on drug resistance more confusing and fuzzier. In the review, we summarize the regulation of autophagy by emerging ways, the action of targeting autophagy on drug resistance and some of the new therapeutic approaches to treat tumor drug resistance by interfering with autophagy-related pathways. The full-scale understanding of the tumor-associated signaling pathways and physiological functions of autophagy will hopefully open new possibilities for the treatment of tumor drug resistance and the improvement in clinical outcomes.

Morin Hydrate Sensitizes Hepatoma Cells and Xenograft Tumor towards Cisplatin by Downregulating PARP-1-HMGB1 Mediated Autophagy

The cross-talk between apoptosis and autophagy influences anticancer drug sensitivity and cellular death in various cancer cell lines. However, the fundamental mechanisms behind this phenomenon are still unidentified. We demonstrated anti-cancerous role of cisplatin (CP) and morin hydrate (Mh) as an individual and/or in combination (CP-Mh) in hepatoma cells and tumor model. Exposure of CP resulted in the production of intracellular reactive oxygen species (ROS)-mediated cellular vacuolization, expansion of mitochondria membrane and activation of endoplasmic reticulum (ER)-stress. Consequently, Cyt c translocation led to the increase of Bax/Bcl-2 ratio, which simultaneously triggered caspase-mediated cellular apoptosis. In addition, CP-induced PARP-1 activation led to ADP-ribosylation of HMGB1, which consequently developed autophagy as evident by the LC3I/II ratio. Chemically-induced inhibition of autophagy marked by increased cell death signified a protective role of autophagy against CP treatment. CP-Mh abrogates the PARP-1 expression and significantly reduced HMGB1-cytoplasmic translocation with subsequent inhibition of the HMGB1-Beclin1 complex formation. In the absence of PARP-1, a reduced HMGB1 mediated autophagy was observed followed by induced caspase-dependent apoptosis. To confirm the role of PARP-1-HMGB1 signaling in autophagy, we used the PARP-1 inhibitor, 4-amino-1,8-naphthalimide (ANI), HMGB1 inhibitor, ethyl pyruvate (EP), autophagy inhibitors, 3-methyl adenine (3-MA) and bafilomycin (baf) and small interfering RNAs (siRNA) to target Atg5 in combination of CP and Mh. Exposure to these inhibitors enhanced the sensitivity of HepG2 cells to CP. Collectively, our findings indicate that CP-Mh in combination served as a prominent regulator of autophagy and significant inducer of apoptosis that maintains a homeostatic balance towards HepG2 cells and the subcutaneous tumor model.

Autophagy as a mechanism for anti-angiogenic therapy resistance

Autophagy is a lysosomal-dependent degradation process that is highly conserved and maintains cellular homeostasis by sequestering cytosolic material for degradation either non-specifically by non-selective autophagy, or targeting specific proteins aggregates by selective autophagy. Autophagy serves as a protective mechanism defending the cell from stressors and also plays an important role in enabling tumor cells to overcome harsh conditions arising in their microenvironment during growth as well as oxidative and non-oxidative injuries secondary to therapeutic stressors. Recently, autophagy has been implicated to cause tumor resistance to anti-angiogenic therapy, joining an existing literature implicating autophagy in cancer resistance to conventional DNA damaging chemotherapy and ionizing radiation. In this review, we discuss the role of angiogenesis in malignancy, mechanisms of resistance to anti-angiogenic therapy in general, the role of autophagy in driving malignancy, and the current literature in autophagy-mediated anti-angiogenic therapy resistance. Finally, we provide future insight into the current challenges of using autophagy inhibitors in the clinic and provides tips for future studies to focus on to effectively target autophagy in overcoming resistance to anti-angiogenic therapy.

Inhibiting Autophagy in Renal Cell Cancer and the Associated Tumor Endothelium

The clear cell subtype of kidney cancer encompasses most renal cell carcinoma cases and is associated with the loss of von Hippel-Lindau gene function or expression. Subsequent loss or mutation of the other allele influences cellular stress responses involving nutrient and hypoxia sensing. Autophagy is an important regulatory process promoting the disposal of unnecessary or degraded cellular components, tightly linked to almost all cellular processes. Organelles and proteins that become damaged or that are no longer needed in the cell are sequestered and digested in autophagosomes upon fusing with lysosomes, or alternatively, released via vesicular exocytosis. Tumor development tends to disrupt the regulation of the balance between this process and apoptosis, permitting prolonged cell survival and increased replication. Completed trials of autophagic inhibitors using hydroxychloroquine in combination with other anticancer agents including rapalogues and high-dose interleukin 2 have now been reported. The complex nature of autophagy and the unique biology of clear cell renal cell carcinoma warrant further understanding to better develop the next generation of relevant anticancer agents.

Combination of an Autophagy Inducer and an Autophagy Inhibitor: A Smarter Strategy Emerging in Cancer Therapy

Autophagy is considered a cytoprotective function in cancer therapy under certain conditions and is a drug resistance mechanism that represents a clinical obstacle to successful cancer treatment and leads to poor prognosis in cancer patients. Because certain clinical drugs and agents in development have cytoprotective autophagy effects, targeting autophagic pathways has emerged as a potential smarter strategy for cancer therapy. Multiple preclinical and clinical studies have demonstrated that autophagy inhibition augments the efficacy of anticancer agents in various cancers. Autophagy inhibitors, such as chloroquine and hydroxychloroquine, have already been clinically approved, promoting drug combination treatment by targeting autophagic pathways as a means of discovering and developing more novel and more effective cancer therapeutic approaches. We summarize current studies that focus on the antitumor efficiency of agents that induce cytoprotective autophagy combined with autophagy inhibitors. Furthermore, we discuss the challenge and development of targeting cytoprotective autophagy as a cancer therapeutic approach in clinical application. Thus, we need to facilitate the exploitation of appropriate autophagy inhibitors and coadministration delivery system to cooperate with anticancer drugs. This review aims to note optimal combination strategies by modulating autophagy for therapeutic advantage to overcome drug resistance and enhance the effect of antitumor therapies on cancer patients.

Molecular Mechanisms Underlying Autophagy-Mediated Treatment Resistance in Cancer

Despite advances in diagnostic tools and therapeutic options, treatment resistance remains a challenge for many cancer patients. Recent studies have found evidence that autophagy, a cellular pathway that delivers cytoplasmic components to lysosomes for degradation and recycling, contributes to treatment resistance in different cancer types. A role for autophagy in resistance to chemotherapies and targeted therapies has been described based largely on associations with various signaling pathways, including MAPK and PI3K/AKT signaling. However, our current understanding of the molecular mechanisms underlying the role of autophagy in facilitating treatment resistance remains limited. Here we provide a comprehensive summary of the evidence linking autophagy to major signaling pathways in the context of treatment resistance and tumor progression, and then highlight recently emerged molecular mechanisms underlying autophagy and the p62/KEAP1/NRF2 and FOXO3A/PUMA axes in chemoresistance.

Licarin A induces cell death by activation of autophagy and apoptosis in non-small cell lung cancer cells

Lung cancer has a relatively poor prognosis with a low survival rate and drugs that target other cell death mechanism like autophagy may help improving current therapeutic strategy. This study investigated the anti-proliferative effect of Licarin A (LCA) from Myristica fragrans in non-small cell lung cancer cell lines-A549, NCI-H23, NCI-H520 and NCI-H460. LCA inhibited proliferation of all the four cell lines in a dose and time dependent manner with minimum IC50 of 20.03 ± 3.12, 22.19 ± 1.37 µM in NCI-H23 and A549 cells respectively. Hence NCI-H23 and A549 cells were used to assess the ability LCA to induce autophagy and apoptosis. LCA treatment caused G1 arrest, increase in Beclin 1, LC3II levels and degradation of p62 indicating activation of autophagy in both NCI-H23 and A549 cells. In addition, LCA mediated apoptotic cell death was confirmed by MMP loss, increased ROS, cleaved PARP and decreased pro-caspase3. To understand the role of LCA induced autophagy and its association with apoptosis, cells were analysed following treatment with a late autophagy inhibitor-chloroquine and also after Beclin 1 siRNA transfection. Data indicated that inhibition of autophagy resulted in reduced anti-proliferative as well as pro-apoptotic ability of LCA. These findings confirmed that LCA brought about autophagy dependent apoptosis in non-small cell lung cancer cells and hence it may serve as a potential drug candidate for non-small cell lung cancer therapy.

New insights into autophagy in hepatocellular carcinoma: mechanisms and therapeutic strategies

Autophagy is a mechanism by which cellular substances are transported to lysosomes for degradation, allowing the basic transformation of cellular components, and providing energy and macromolecular precursors. In cancer, the contradictory role of autophagy in tumor suppression and promotion has been widely acknowledged. Activation and suppression of autophagy have been proposed as cancer therapies, resulting in targeted treatment of cancer by autophagy being considered ambiguous. The dynamic effect of autophagy can also be applied to hepatocellular carcinoma (HCC), a malignant tumor with high incidence and a low survival rate. In this review, we introduce characteristics of different types of autophagy and summarize which genes, non-coding RNAs, and related signaling pathways are involved in autophagy and the regulation of the formation and progress of HCC. More importantly, we discuss the role of autophagy in the treatment of HCC, such as in traditional chemotherapy, molecular targeted drugs, and natural products.

Oxidative Stress-Driven Autophagy acROSs Onset and Therapeutic Outcome in Hepatocellular Carcinoma

Reactive oxygen species- (ROS-) mediated autophagy physiologically contributes to management of cell homeostasis in response to mild oxidative stress. Cancer cells typically engage autophagy downstream of ROS signaling derived from hypoxia and starvation, which are harsh environmental conditions that need to be faced for cancer development and progression. Hepatocellular carcinoma (HCC) is a solid tumor for which several environmental risk factors, particularly viral infections and alcohol abuse, have been shown to promote carcinogenesis via augmentation of oxidative stress. In addition, ROS burst in HCC cells frequently takes place after administration of therapeutic compounds that promote apoptotic cell death or even autophagic cell death. The interplay between ROS and autophagy (i) in the disposal of dysfunctional mitochondria via mitophagy, as a tumor suppressor mechanism, or (ii) in the cell survival adaptive response elicited by chemotherapeutic interventions, as a tumor-promoting event, will be depicted in this review in relation to HCC development and progression.

MicroRNAs contribute to ATP-binding cassette transporter- and autophagy-mediated chemoresistance in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has an elevated mortality rate, largely because of high recurrence and metastasis. Additionally, the main obstacle during treatment of HCC is that patients usually develop resistance to chemotherapy. Cancer drug resistance involves many different mechanisms, including alterations in drug metabolism and processing, impairment of the apoptotic machine, activation of cell survival signaling, decreased drug sensitivity and autophagy, among others. Nowadays, miRNAs are emerging as master regulators of normal physiology- and tumor-related gene expression. In HCC, aberrant expression of many miRNAs leads to chemoresistance. Herein, we particularly analyzed miRNA impact on HCC resistance to drug therapy. Certain miRNAs target ABC (ATP-binding cassette) transporter genes. As most of these miRNAs are downregulated in HCC, transporter levels increase and intracellular drug accumulation decrease, turning cells less sensitive to death. Others miRNAs target autophagy-related gene expression, inhibiting autophagy and acting as tumor suppressors. Nevertheless, due to its downregulation in HCC, these miRNAs do not inhibit autophagy or tumor growth and, resistance is favored. Concluding, modulation of ABC transporter and/or autophagy-related gene expression or function by miRNAs could be determinant for HCC cell survival under chemotherapeutic drug treatment. Undoubtedly, more insights on the biological processes, signaling pathways and/or molecular mechanisms regulated by miRNAs are needed. Anyway, miRNA-based therapy together with conventional chemotherapeutic drugs has a great future in cancer therapy.

Pro-survival autophagy and cancer cell resistance to therapy

Resistance to therapy is one of the prime causes for treatment failure in cancer and recurrent disease. In recent years, autophagy has emerged as an important cell survival mechanism in response to different stress conditions that are associated with cancer treatment and aging. Autophagy is an evolutionary conserved catabolic process through which damaged cellular contents are degraded after uptake into autophagosomes that subsequently fuse with lysosomes for cargo degradation, thereby alleviating stress. In addition, autophagy serves to maintain cellular homeostasis by enriching nutrient pools. Although autophagy can act as a double-edged sword at the interface of cell survival and cell death, increasing evidence suggest that in the context of cancer therapy-induced stress responses, it predominantly functions as a cell survival mechanism. Here, we provide an up-to-date overview on our current knowledge of the role of pro-survival autophagy in cancer therapy at the preclinical and clinical stages and delineate the molecular mechanisms of autophagy regulation in response to therapy-related stress conditions. A better understanding of the interplay of cancer therapy and autophagy may allow to unveil new targets and avenues for an improved treatment of therapy-resistant tumors in the foreseeable future.

Glycochenodeoxycholate promotes hepatocellular carcinoma invasion and migration by AMPK/mTOR dependent autophagy activation

Metastasis and recurrence severely impact the treatment effect of hepatocellular carcinoma (HCC). HCC complicated with cholestasis is more prone to recurrence and metastasis. Previous studies have implicated pathogenesis of HCC by bile acid; however, the underlying mechanism is unknown yet. Glycochenodeoxycholate (GCDC) is one of most important component of bile acid (BA). In the present study, the role of GCDC in HCC cells invasion was detected by in vitro and in vivo assays. GCDC was found to significantly enhance the invasive potential of HCC cells; Further studies showed that GCDC could induce autophagy activation and higher invasive capability in HCC cells. Interestingly, inhibition of autophagy by chloroquine (CQ) reversed this phenomenon. Subsequently, the correlation between TBA expression level and clinicopathological characteristics was analyzed in HCC patients. Clinically, high TBA level in HCC tissue was found to be associated with more invasive and poor survival in HCC patients. Mechanistic study showed that bile acid induced autophagy by targeting the AMPK/mTOR pathway in HCC cells. Therefore, our results suggest that bile acid may promote HCC invasion via activation of autophagy and the level of bile acid may serve as a potential useful indicator for prognosis of HCC patients.

Autophagy and liver cancer

Autophagy is a key biological phenomenon conserved from yeast to mammals. Under basal conditions, activation of autophagy leads to the protein degradation as well as damaged organelles for maintaining cellular homeostasis. Deregulation of autophagy has been identified as a key mechanism contributing to the pathogenesis and progression of several liver diseases, including hepatocellular carcinoma (HCC), one of the most common and mortal types of cancer. Currently used treatment strategies in patients with HCC result in variable success rates. Therefore, novel early diagnosis and treatment techniques should be developed. Manipulation of autophagy may improve responses of cancer cell to treatments and provide novel targeted therapy options for HCC. In this review, we summarized how our understanding of autophagy-cell death connection may have an impact on HCC therapy.

Inhibition of the formation of autophagosome but not autolysosome augments ABT-751-induced apoptosis in TP53-deficient Hep-3B cells

The objective was to investigate the upstream mechanisms of apoptosis which were triggered by a novel antimicrotubule drug, ABT-751, in a tumor protein p53 ( TP53)-deficient hepatocellular carcinoma-derived Hep-3B cells. A series of in vitro assays indicated that ABT-751 caused the disruption of the mitotic spindle structure, collapse of mitochondrial membrane potential, generation of reactive oxygen species, DNA damage, G ₂ /M cell cycle arrest, inhibition of anchorage-independent cell growth and apoptosis in Hep-3B cells accompanied by alteration of the expression levels of several DNA damage checkpoint proteins and cell cycle regulators. Subsequently, ABT-751 triggered apoptosis along with markedly upregulated several proapoptotic proteins involving in extrinsic, intrinsic, and caspase-mediated apoptotic pathways. A pan-caspase inhibitor suppressed ABT-751-induced apoptosis. ABT-751 also induced autophagy soon after the occurrence of apoptosis through the suppression of AKT serine/threonine kinase/mechanistic target of rapamycin signaling pathway. Exogenous expression of the TP53 gene significantly incurred both apoptosis and autophagy in Hep-3B cells. Pharmacological inhibition of autophagosome (early autophagy) but not autolysosome (late autophagy) enhanced ABT-751-induced apoptosis in TP53-deficient Hep-3B cells. Our study provided a new strategy to augment ABT-751-induced apoptosis in TP53-deficient cells.

Apoptosis and autophagy induced by DVDMs-PDT on human esophageal cancer Eca-109 cells

BACKGROUND

Esophageal cancer is a common gastrointestinal cancer. About 300,000 people die from esophageal cancer every year in the world. Photodynamic therapy (PDT) has attracted attention as a feasible cancer therap for this diagnosis. Sinoporphyrin sodium (DVDMs) is a novel sensitizer isolated from photofrin. In this study, we aimed to investigate the effects of DVDMs mediated photodynamic therapy and the possible mechanism on human esophageal cancer Eca-109 cells.

METHODS

Cell viability was measured by MTT assay and cell apoptosis was determined by Annexin V-PE/7-AAD and western blot. MDC staining and western blot were used to evaluate cell autophagy. The production of intracellular reactive oxygen species (ROS) was detected by flow cytometry. The expression of MAPK and HO-1 were detected by western blot.

RESULTS

DVDMs-PDT decreased cell viability and induced cell apoptosis and autophagy. Autophagy inhibition reduced cell apoptosis triggered by DVDMs-PDT in Eca-109 cells. Generation of ROS was detected in DVDMs-PDT group. p38MAPK, JNK and HO-1 were activated after PDT treatment and the activation were reversed by adding ROS scavenger NAC.

CONCLUSIONS

Our studies demonstrated that DVDMs-PDT induced apoptosis and autophagy in Eca-109 cells. DVDMs-PDT induced ROS generation in Eca-109 cells, and the generation of ROS activated p38MAPK and JNK. Activation of p38MAPK and JNK may be involved in PDT-induced apoptosis.

The role of ROS-induced autophagy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a main cause of cancer-related mortality and its etiology is not fully understood. As prominent factors that regulate cellular homeostasis, both reactive oxygen species (ROS) and autophagy are considered to play an essential role in the liver carcinogenesis. However, the crosstalk between ROS and autophagy is not well characterized in the pathogenesis of HCC. This review summarizes the roles of autophagy in ROS-mediated hepatocarcinogenesis and discusses the role of ROS-induced autophagy in HCC cell fate decision following treatment with chemotherapeutic agents in preclinical settings, which may allow the identification of novel strategies for the treatment of HCC.

Trophoblast-Specific Conditional Atg7 Knockout Mice Develop Gestational Hypertension

Hypertensive disorder of pregnancy (HDP) is a serious pregnancy complication that is life threatening to both the mother and fetus. Understanding HDP pathophysiology is important for developing medical treatments. This study demonstrates the involvement of autophagy deficiency in adverse maternal and fetal outcomes using trophoblast-specific autophagy related (Atg)7, an autophagy-related protein, knockout mice. Atg7 conditional knockout (cKO) placentas were significantly smaller than controls in the spongiotrophoblast layer but not the labyrinth layer, which significantly elevated blood pressure in dams. A marker of autophagy deficiency, sequestosome 1/p62, was accumulated in giant trophoblast cells and in the spongiotrophoblast layer, accompanying increased apoptosis. However, neither proteinuria in dams nor fetal growth restriction was observed. Regarding trophoblast function, the number of trophoblasts migrating into the maternal decidua was significantly reduced, and the wall/lumen ratio of the spiral arteries was significantly increased in cKO placentas, suggesting shallow trophoblast invasion and inadequate vascular remodeling. The relative expression of placental growth factor mRNA was significantly decreased in cKO placentas compared with the control, likely causing poor placentation; however, other factors were unchanged in cKO placentas. This is the first report of autophagy deficiency leading to impaired placentation complicated by maternal HDP attributable to trophoblast dysfunction, and it suggests that placental autophagy is required for normal placentation.

Induction of reactive oxygen species: an emerging approach for cancer therapy

Reactive oxygen species (ROS), a group of ions and molecules, include hydroxyl radicals (·OH), alkoxyl radicals, superoxide anion (O₂·-), singlet oxygen (¹O₂) and hydrogen peroxide (H₂O₂). Hydroxyl radicals and alkoxyl radicals are extremely and highly reactive species respectively. Endogenous ROS are mainly formed in mitochondrial respiratory chain. Low levels of ROS play important roles in regulating biological functions in mammalian cells. However, excess production of ROS can induce cell death by oxidative damaging effects to intracellular biomacromolecules. Cancer cell death types induced by ROS include apoptotic, autophagic, ferroptotic and necrotic cell death. Since abnormal metabolism in cancer cells, they have higher ROS content compared to normal cells. The higher endogenous ROS levels in cancer cells endow them more susceptible to the ROS-induction treatment. Indeed, some anticancer drugs currently used in clinic, such as molecular targeted drugs and chemotherapeutic agents, effectively kill cancer cells by inducing ROS generation. In addition, photodynamic therapy (PDT) is mainly based on induction of ROS burst to kill cancer cells. The mechanism of cell death induced by radiotherapy using ionizing radiation also refers to ROS production. Moreover, ROS play an important role in tumor immune therapy. Altogether, combining above traditional treatments with ROS-induced agents will be considered as a promising strategy in cancer therapy. In this review, we focus on our current understanding of the anticancer effects of ROS.

Hypoxia-induced autophagy promotes gemcitabine resistance in human bladder cancer cells through hypoxia-inducible factor 1α activation

Overcoming the chemoresistance of bladder cancer is a pivotal obstacle in clinical treatments. Hypoxia widely exists in solid tumors and has been demonstrated to contribute to chemoresistance through hypoxia-inducible factor 1α (HIF‑1α)-mediated autophagy in several types of cancer. However, it is unclear whether HIF‑1α-mediated autophagy and chemoresistance occur in bladder cancer. The present study demonstrated that HIF‑1α was overexpressed in 20 bladder cancer tissues compared with matched paracarcinoma tissues. Gemcitabine-induced apoptosis during hypoxia was significantly reduced compared with that observed under normoxic conditions. In addition, hypoxia activated autophagy and enhanced gemcitabine-induced autophagy. Combined treatment using gemcitabine and an autophagy inhibitor (3-methyladenine) under hypoxia significantly increased gemcitabine cytotoxicity. Furthermore, it was demonstrated that hypoxia-activated autophagy depended on the HIF‑1α/BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3)/Beclin1 signaling pathway. Suppressing HIF‑1α inhibited autophagy, BNIP3 and Beclin1, as well as enhanced gemcitabine-induced apoptosis in bladder cancer cells under hypoxic conditions. Consequently, the results of the present study demonstrated that hypoxia-induced cytoprotective autophagy counteracted gemcitabine-induced apoptosis through increasing HIF‑1α expression. Therefore, targeting HIF‑1α-associated pathways or autophagy in bladder cancer may be a successful strategy to enhance the sensitivity of bladder cancer chemotherapy.

Autophagy: a potential target for the treatment of intraocular neovascularization

The formation of neovascularization is a common pathological feature of many ocular vascular diseases, and is an important cause of vision loss in patients. Neovascularization can cause retinal hemorrhage, vitreous hemorrhage, and other serious complications, leading to loss of vision. The treatment of intraocular neovascularization is the focus of ophthalmology research. In recent years, some studies have found that autophagy is closely related to vascular endothelial growth factor and the formation of neovascularization. Autophagy is expected to become a new target for the treatment of intraocular neovascularization. Therefore, this article reviews the research on autophagy and the formation of intraocular neovascularization.

Hepatoprotective Effect of Curcumin on Hepatocellular Carcinoma Through Autophagic and Apoptic Pathways

BACKGROUND AND RATIONALE

Microtubule-associated protein light chain 3-II (LC3-II), and Sequestosome-1 (SQSTM1) are proteins that can be used as markers for autophagic pathway. Bcl-2 protein is reported to be inversely correlated with apoptosis. We aimed to investigate the effects of curcumin on liver inflammation and fibrosis up to the first dysplastic stage of Hepatocellular carcinoma (HCC) induced by Thioacetamide (TAA) in rats and to clarify the effects of curcumin on LC3-II, SQSTM1, and Bcl-2. Male Sprague-Dawley rats were randomized into four groups: Control group, TAA group, Curcumin low-dose group, and Curcumin highdose group. The last three groups received TAA 200 mg/kg i.p. twice weekly for 18 weeks. Oxidative stress markers as hepatic malondialdehyde (MDA) concentration and superoxide dismutase (SOD) activity were measured by colorimetric methods. Hepatic SQSTM1 concentration was measured by ELISA, and gene expression levels of Bcl-2, and LC3-II were measured by RT-PCR.We also investigated the in vitro effect of curcumin on HepG2 cells viability through MTT assay, and the involvement of autophagy in this effect.

RESULTS

Curcumin increased the survival percent in rats, decreased -fetoprotein (AFP) concentration, and serum aspartate aminotransferase (AST) activity, and increased serum albumin concentration. Curcumin also significantly reduced oxidative stress in liver, inhibited apoptosis, and induced autophagy. In vitro, curcumin (50 µM) decreased HepG2 cells viabilityand the concentration of SQSTM1.

CONCLUSIONS

Curcumin leads to protection against TAA induced HCC up to the first dysplastic stage through activating autophagic pathway and inhibiting apoptosis. Also, the antioxidant activity of curcumin almost prevents liver fibrosis.

Targeting Oxidatively Induced DNA Damage Response in Cancer: Opportunities for Novel Cancer Therapies

Cancer is a death cause in economically developed countries that results growing also in developing countries. Improved outcome through targeted interventions faces the scarce selectivity of the therapies and the development of resistance to them that compromise the therapeutic effects. Genomic instability is a typical cancer hallmark due to DNA damage by genetic mutations, reactive oxygen and nitrogen species, ionizing radiation, and chemotherapeutic agents. DNA lesions can induce and/or support various diseases, including cancer. The DNA damage response (DDR) is a crucial signaling-transduction network that promotes cell cycle arrest or cell death to repair DNA lesions. DDR dysregulation favors tumor growth as downregulated or defective DDR generates genomic instability, while upregulated DDR may confer treatment resistance. Redox homeostasis deeply and capillary affects DDR as ROS activate/inhibit proteins and enzymes integral to DDR both in healthy and cancer cells, although by different routes. DDR regulation through modulating ROS homeostasis is under investigation as anticancer opportunity, also in combination with other treatments since ROS affect DDR differently in the patients during cancer development and treatment. Here, we highlight ROS-sensitive proteins whose regulation in oxidatively induced DDR might allow for selective strategies against cancer that are better tailored to the patients.

Resistance a major hindrance to chemotherapy in hepatocellular carcinoma: an insight

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer mortality, accounting for almost 90% of total liver cancer burden. Surgical resection followed by adjuvant and systemic chemotherapy are the most meticulously followed treatment procedures but the complex etiology and high metastatic potential of the disease renders surgical treatment futile in majority of the cases. Another hindrance to the scenario is the acquired resistance to drugs resulting in relapse of the disease. Hence, to provide insights into development of novel therapeutic targets and diagnostic biomarkers, this review focuses on the various molecular mechanisms underlying chemoresistance in HCC. We have provided a comprehensive summary of the various strategies adopted by HCC cells, extending from apoptosis evasion, autophagy activation, drug expulsion to epigenetic transformation as modes of therapy resistance. The role of stem cells in imparting chemoresistance is also discussed. Furthermore, the review also focuses on how this knowledge might be exploited for the development of an effective, prospective therapy against HCC.

An Interplay between Senescence, Apoptosis and Autophagy in Glioblastoma Multiforme-Role in Pathogenesis and Therapeutic Perspective

Autophagy, cellular senescence, programmed cell death and necrosis are key responses of a cell facing a stress. These effects are partly interconnected, but regulation of their mutual interactions is not completely clear. That regulation seems to be especially important in cancer cells, which have their own program of development and demand more nutrition and energy than normal cells. Glioblastoma multiforme (GBM) belongs to the most aggressive and most difficult to cure cancers, so studies on its pathogenesis and new therapeutic strategies are justified. Using an animal model, it was shown that autophagy is required for GBM development. Temozolomide (TMZ) is the key drug in GBM chemotherapy and it was reported to induce senescence, autophagy and apoptosis in GBM. In some GBM cells, TMZ induces small toxicity despite its significant concentration and GBM cells can be intrinsically resistant to apoptosis. Resveratrol, a natural compound, was shown to potentiate anticancer effect of TMZ in GBM cells through the abrogation G2-arrest and mitotic catastrophe resulting in senescence of GBM cells. Autophagy is the key player in TMZ resistance in GBM. TMZ can induce apoptosis due to selective inhibition of autophagy, in which autophagic vehicles accumulate as their fusion with lysosomes is blocked. Modulation of autophagic action of TMZ with autophagy inhibitors can result in opposite outcomes, depending on the step targeted in autophagic flux. Studies on relationships between senescence, autophagy and apoptosis can open new therapeutic perspectives in GBM.

Panduratin A induces protective autophagy in melanoma via the AMPK and mTOR pathway

BACKGROUND

Targeting autophagy is emerging as a promising strategy in cancer therapeutics in recent years. Autophagy can be modulated to drive cancer cell deaths that are notoriously resistant to apoptotic-inducing drugs. In addition, autophagy has been implicated as a prosurvival mechanism in mediating cancer chemoresistance. Our previous study has demonstrated that Panduratin A (PA), a plant-derived active compound exploits ER-stress-mediated apoptosis as its cytotoxic mechanism on melanoma.

PURPOSE

Our previous proteomics analysis revealed that treatment with PA resulted in the upregulation of an autophagy marker, LC3B in melanoma cells. Therefore, the present study sought to investigate the role of PA-induced autophagy in melanoma cells.

METHODS

Transmission electron microscopy was performed for examination of autophagic ultra-structures in PA-treated A375 cells. Cytoplasmic LC3B and p62/SQSMT1 punctate structures were detected using immunofluorescene staining. Expression levels of LC3B II, p62/SQSMT1, ATG 12, Beclin 1, phospho S6 (ser235/236), phospho AMPK (Thr172) and cleaved PARP were evaluated by western blotting.

RESULTS

Autophagosomes, autolysosomes and punctuates of LC3 proteins could be observed in PA-treated A375 cells. PA-induced autophagy in A375 melanoma cells was found to be mediated through the inhibition of mTOR signaling and activation of AMPK pathway. Furthermore, we showed that PA-induced apoptosis was increased in the presence of an autophagy inhibitor, signifying the cytoprotective effect of PA-induced autophagy in melanoma cells.

CONCLUSION

Taken together, results from the present study suggest that the inhibition of autophagy by targeting mTOR and AMPK could potentiate the cytotoxicity effects of PA on melanoma cells.

The Complex Link between Apoptosis and Autophagy: a Promising New Role for RB

Physiological processes, as autophagy, proliferation and apoptosis are affected during carcinogenesis. Restoring cellular sensitivity to apoptotic stimuli, such as the antineoplastic cocktails, has been explored as a strategy to eliminate cancer cells. Autophagy, a physiological process of recycling organelles and macromolecules can be deviated from homeostasis to support cancer cells survival, proliferation, escape from apoptosis, and therapy resistance. The relationship between autophagy and apoptosis is complex and many stimuli can induce both processes. Most chemotherapeutic agents induce autophagy and it is not clear whether and how this chemotherapy-induced autophagy might contribute to resistance to apoptosis. Here, we review current strategies to sensitize cancer cells by interfering with autophagy. Moreover, we discuss a new link between autophagy and apoptosis: the tumor suppressor retinoblastoma protein (RB). Inactivation of RB is one of the earliest and more frequent hallmarks of cancer transformation, known to control cell cycle progression and apoptosis. Therefore, understanding RB functions in controlling cell fate is essential for an effective translation of RB status in cancer samples to the clinical outcome.

Autophagy: 'Self-Eating' Your Way to Longevity

Ageing is the gradual decline in biological function both at the cellular and organismal level. One of the key characteristics of cellular ageing is the accumulation of damaged proteins and organelles which, in turn, can cause cellular toxicity and death. Autophagy is an evolutionarily conserved process that is responsible for the sequestration of damaged or surplus cytoplasmic components which are then delivered to the lysosome for degradation. This house-keeping mechanism is essential to maintain cellular homeostasis and survival, particularly during stress. A decline or loss of sensitivity/responsiveness of autophagy is intimately linked with an accelerated rate of ageing as well as many age-related diseases including neurodegeneration, cancer and metabolic disease where damage accumulation exceeds damage removal. This chapter summarises current knowledge regarding the relationship between autophagy and ageing and outlines some strategies that can be implemented to promote the anti-ageing effects of autophagy to improve human health and lifespan.

Regulation and role of nuclear factor-E2-related factor 2 (Nrf2) in multidrug resistance of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) chemoresistance, which is regarded as a kind of stress management reaction to chemotherapy drugs, severely hinders the therapy outcomes of HCC treatment. Stress management is generally achieved by activating certain signal pathways and chemical factors, among which, nuclear factor-E2-related factor2 (Nrf2) is a key factor in HCC chemoresistance formation. Nrf2 is a nuclear factor that coordinates the induction and expression of a battery of genes encoding cytoprotective proteins when participating in the Nrf2antioxidant response element (Nrf2/ARE) pathway, which is one of the most important intracellular antioxidant stress pathways. This review summarizes the recent understanding of the involvement of Nrf2 in the chemoresistance of liver cancer, its target proteins, expression regulation and potential Nrf2 inhibitors that sensitize chemotherapy drugs in HCC.

Autophagy inhibition contributes to Endostar sensitization in esophageal squamous cell carcinoma

Endostar is a novel artificially-synthesized anti-angiogenesis drug, and has been approved for clinical use. Previous studies have indicated that patients with esophageal cancer could benefit from Endostar combined with chemotherapy or chemoradiotherapy. However, the most advantageous use of this drug remains to be elucidated. The role of autophagy in cancer treatment remains controversial. The results of the present study demonstrated that Endostar promotes autophagy activation, which is regulated via phosphorylation inhibition of the downstream signaling molecules of the vascular endothelial growth factor, AKT serine/threonine kinase and mechanistic target of rapamycin signaling pathways. Furthermore, inhibiting autophagy using the pharmacological inhibitor chloroquine facilitated the antiproliferative effect of Endostar and increased the number of apoptotic cells, compared with Endostar monotherapy. Taken together, the results of the present study suggest that autophagy activation induced by Endostar serves a protective role in human esophageal cancer treatment, and that autophagy inhibition promotes the antiproliferative role of Endostar. Therefore, the combination of Endostar with an autophagy inhibitor may be a novel prospective approach to improving the efficacy of Endostar for the treatment of patients with esophageal cancer.

Role of early growth response 1 in liver metabolism and liver cancer

The liver is an essential organ for nutrient and drug metabolism - possessing the remarkable ability to sense environmental and metabolic stimuli and provide an optimally adaptive response. Early growth response 1 (Egr1), an immediate early transcriptional factor which acts as a coordinator of the complex response to stress, is induced during liver injury and controls the expression of a wide range of genes involved in metabolism, cell proliferation, and role of Egr1 in liver injury and repair, deficiency of Egr1 delays liver regeneration process. The known upstream regulators of Egr1 include, but are not limited to, growth factors (e.g. transforming growth factor β1, platelet-derived growth factor, epidermal growth factor, hepatocyte growth factor), nuclear receptors (e.g. hepatocyte nuclear factor 4α, small heterodimer partner, peroxisome proliferator-activated receptor-γ), and other transcription factors (e.g. Sp1, E2F transcription factor 1). Research efforts using various animal models such as fatty liver, liver injury, and liver fibrosis contribute greatly to the elucidation of Egr1 function in the liver. Hepatocellular carcinoma (HCC) represents the second leading cause of cancer mortality worldwide due to the heterogeneity and the late stage at which cancer is generally diagnosed. Recent studies highlight the involvement of Egr1 in HCC development. The purpose of this review is to summarize current studies pertaining to the role of Egr1 in liver metabolism and liver diseases including liver cancer.

Autophagy activation promotes bevacizumab resistance in glioblastoma by suppressing Akt/mTOR signaling pathway

Glioblastomas are the most common primary and malignant brain tumors. The standard therapy includes surgery and radiotherapy plus chemotherapy, with additional bevacizumab to block the angiogenesis in tumors. However, the ever-growing tolerance of glioblastomas to chemotherapeutic drugs impairs the clinical outputs of tumor treatment. The present study investigated the tolerance of glioblastomas to bevacizumab. Although bevacizumab resulted in direct anti-proliferation and pro-apoptosis effects on glioblastoma cells via downregulating the anti-apoptotic proteins and upregulating the pro-apoptotic proteins, tolerance was also encountered that was mainly caused by autophagy induction in tumor cells. The suppressed Akt-mTOR signaling pathway led to the upregulated autophagy process. Blockade of the autophagy process significantly increased the tumor-suppressive effect of bevacizumab on glioblastoma cells. To our knowledge, the present study is the first to report the involvement of autophagy in the tolerance of glioblastomas to bevacizumab. Therefore, autophagy inhibition may be considered a novel way to overcome the tolerance of glioblastomas to anti-angiogenic agents.