Chloroquine inhibits colon cancer cell growth in vitro and tumor growth in vivo via induction of apoptosis

Chloroquine-induced DNA damage synergizes with DNA repair inhibitors causing cancer cell death

Background

Cancer is a global health problem accounting for nearly one in six deaths worldwide. Conventional treatments together with new therapies have increased survival to this devastating disease. However, the persistent challenges of treatment resistance and the limited therapeutic arsenal available for specific cancer types still make research in new therapeutic strategies an urgent need.

Methods

Chloroquine was tested in combination with different drugs (Panobinostat, KU-57788 and NU-7026) in 8 human-derived cancer cells lines (colorectal: HCT116 and HT29; breast: MDA-MB-231 and HCC1937; glioblastoma: A-172 and LN-18; head and neck: CAL-33 and 32816). Drug´s effect on proliferation was tested by MTT assays and cell death was assessed by Anexin V-PI apoptosis assays. The presence of DNA double-strand breaks was analyzed by phospho-H2AX fluorescent staining. To measure homologous recombination efficiency the HR-GFP reporter was used, which allows flow cytometry-based detection of HR stimulated by I-SceI endonuclease-induced DSBs.

Results

The combination of chloroquine with any of the drugs employed displayed potent synergistic effects on apoptosis induction, with particularly pronounced efficacy observed in glioblastoma and head and neck cancer cell lines. We found that chloroquine produced DNA double strand breaks that depended on reactive oxygen species formation, whereas Panobinostat inhibited DNA double-strand breaks repair by homologous recombination. Cell death caused by chloroquine/Panobinostat combination were significantly reduced by N-Acetylcysteine, a reactive oxygen species scavenger, underscoring the pivotal role of DSB generation in CQ/LBH-induced lethality. Based on these data, we also explored the combination of CQ with KU-57788 and NU-7026, two inhibitors of the other main DSB repair pathway, nonhomologous end joining (NHEJ), and again synergistic effects on apoptosis induction were observed.

Conclusion

Our data provide a rationale for the clinical investigation of CQ in combination with DSB inhibitors for the treatment of different solid tumors.

The Influence of Lysosomal Stress on Dental Pulp Stem Cell-Derived Schwann Cells

BACKGROUND

Dysregulation of the endo-lysosomal-autophagy pathway has been identified as a critical factor in the pathology of various demyelinating neurodegenerative diseases, including peripheral neuropathies. This pathway plays a crucial role in transporting newly synthesized myelin proteins to the plasma membrane in myelinating Schwann cells, making these cells susceptible to lysosome-related dysfunctions. Nevertheless, the specific impact of lysosomal dysfunction in Schwann cells and its contribution to neurodegeneration remain poorly understood.

METHODS

We aim to mimic lysosomal dysfunction in Schwann cells using chloroquine, a lysosomal dysfunction inducer, and to monitor lysosomal leakiness, Schwann cell viability, and apoptosis over time. Additionally, due to the ethical and experimental issues associated with cell isolation and the culturing of human Schwann cells, we use human dental pulp stem cell-derived Schwann cells (DPSC-SCs) as a model in our study.

RESULTS

Chloroquine incubation boosts lysosomal presence as demonstrated by an increased Lysotracker signal. Further in-depth lysosomal analysis demonstrated an increased lysosomal size and permeability as illustrated by a TEM analysis and GAL3-LAMP1 staining. Moreover, an Alamar blue assay and Caspase-3 staining demonstrates a reduced viability and increased apoptosis, respectively.

CONCLUSIONS

Our data indicate that prolonged lysosomal dysfunction leads to lysosomal permeability, reduced viability, and eventually apoptosis in human DPSC-SCs.

Osthole impairs mitochondrial metabolism and the autophagic flux in colorectal cancer

BACKGROUND

Osthole is active constituent of Cnidium monnieri (L.) Cuss. with various physiological functions including anti-inflammation and anti-lipedemic effects. However, the regulatory activity of osthole in colorectal cancer development, focusing on mitochondrial metabolism, is not well known.

HYPOTHESIS/PURPOSE

We hypothesized that osthole may suppress progression of colorectal cancer and aimed to determine the underlying mitochondrial metabolism and the autophagic flux.

STUDY DESIGN

In this study, we elucidated the mechanism of action of osthole in colorectal cancer using an in vivo azoxymethane/dextran sodium sulfate (AOM/DSS) mouse model and an in vitro cell culture system.

METHODS

AOM/DSS mouse model was established and analyzed the effects of osthole on survival rate, diseases activity index, number of tumor and histopathology. Then, cell based assays including viability, cell cycle, reactive oxygen species (ROS), apoptosis, calcium efflux, and mitochondrial function were analyzed. Moreover, osthole-mediated signaling was demonstrated by western blot analyses.

RESULTS

Osthole effectively suppressed the growth of colorectal tumors and alleviated AOM/DSS-induced intestinal injury. Osthole restored the function of goblet cells and impaired the expression of Claudin1 and Axin1 impaired by AOM/DSS. In addition, osthole specifically showed cytotoxicity in colorectal carcinoma cells, but not in normal colon cells. Osthole decreased the ASC/caspase-1/IL-1β inflammasome pathway and induced mitochondrial dysfunction in redox homeostasis, calcium homeostasis. Furthermore, osthole inhibited both oxidative phosphorylation (OXPHOS) and glycolysis, leading to the suppression of ATP production. Moreover, via combination treatment with chloroquine (CQ), we demonstrated that osthole impaired autophagic flux, leading to apoptosis of HCT116 and HT29 cells. Finally, we elucidated that the functional role of tiRNAHisGTG regulated by osthole directly affects the cellular fate of colon cancer cells.

CONCLUSION

These results suggest that osthole has the potential to manage progression of colorectal cancer by regulating autophagy- and mitochondria-mediated signal transduction.

Antimalarial Drugs Induce the Selective Folding of Human Telomeric G-Quadruplex in a Cancer-Mimicking Microenvironment

Regulating the equilibrium between the duplex form of DNA and G-quadruplex (Gq) and stabilizing the folded Gq are the critical factors for any drug to be effective in cancer therapy due to the direct involvement of Gq in controlling the transcription process. Antimalarial drugs are in the trial stage for different types of cancer diseases; however, the plausible mechanism of action of these drug molecules is not well known. Hence, we investigate the plausible role of antimalarial drugs in the folding and stabilization of Gq-forming DNA sequences from the telomere and promoter gene regions by varying the salt (KCl) concentrations, mimicking the in vitro cancerous and normal cell microenvironments. The study reveals that antimalarial drugs fold and stabilize specifically to telomere Gq-forming sequences in the cancerous microenvironment than the DNA sequences located in the promoter region of the gene. Antimalarial drugs are not only able to fold Gq but also efficiently protect them from unfolding by their complementary strands, hence significantly biasing the equilibrium toward the Gq formation from the duplex. In contrast, in a normal cell microenvironment, K+ controls the folding of telomeres, and the role of antimalarial drugs is not prominent. This study suggests that the action of antimalarial drugs is sensitive to the cancer microenvironment as well as selective to the Gq-forming region.

Potential effect of chloroquine and propranolol combination to treat colorectal and triple-negative breast cancers

Drug repositioning explores the reuse of non-cancer drugs to treat tumors. In this work, we evaluated the effect of the combination of chloroquine and propranolol on colorectal and triple-negative breast cancers. Using as in vitro models the colorectal cancer cell lines HCT116, HT29, and CT26, and as triple-negative breast cancer models the 4T1, M-406, and MDA-MB-231 cell lines, we evaluated the effect of the drugs combination on the viability, apoptosis, clonogenicity, and cellular migratory capacity. To explore the in vivo effects of the combination on tumor growth and metastasis development we employed graft models in BALB/c, nude, and CBi mice. In vitro studies showed that combined treatment decreased cell viability in a dose-dependent manner and increased apoptosis. Also, we demonstrated that these drugs act synergically and that it affects clonogenicity and migration. In vivo studies indicated that this drug combination was effective on colorectal models but only partially on breast cancer. These results contributed to the search for new and safe treatments for colorectal and triple-negative carcinomas.

Natural Compounds Targeting the Autophagy Pathway in the Treatment of Colorectal Cancer

Autophagy is a highly conserved intracellular degradation pathway by which misfolded proteins or damaged organelles are delivered in a double-membrane vacuolar vesicle and finally degraded by lysosomes. The risk of colorectal cancer (CRC) is high, and there is growing evidence that autophagy plays a critical role in regulating the initiation and metastasis of CRC; however, whether autophagy promotes or suppresses tumor progression is still controversial. Many natural compounds have been reported to exert anticancer effects or enhance current clinical therapies by modulating autophagy. Here, we discuss recent advancements in the molecular mechanisms of autophagy in regulating CRC. We also highlight the research on natural compounds that are particularly promising autophagy modulators for CRC treatment with clinical evidence. Overall, this review illustrates the importance of autophagy in CRC and provides perspectives for these natural autophagy regulators as new therapeutic candidates for CRC drug development.

Chloroquine synergizes doxorubicin efficacy in cervical cancer cells through flux impairment and down regulation of proteins involved in the fusion of autophagosomes to lysosomes

Drug repurposing holds abundant opportunity in the development of novel anticancer drugs. Chloroquine (CQ), a FDA approved anti-malarial drug, is demonstrated to enhance anticancer efficacy of standard anticancer drugs including doxorubicin (DOX) in several types of cancer cells. Here, we aimed to exploit the chemosensitizing effects of CQ against DOX in human cervical cancer (HeLa) cells that remains to be investigated yet. We show that a combination of DOX (40 nM) and CQ (40 μM) resulted in a synergistic cytotoxicity (combination index; CI < 1) in HeLa cells compared to the DOX or CQ alone. Synergistic effect of the combination (DOX + CQ) was associated with the impaired autophagic flux and enhanced apoptosis. Following treatment with the combination (DOX + CQ), the level of p62/SQSTM and LC-3II proteins was increased, while a decrease was noted in the expression of LAMP-2, Syntaxin17, Rab 5, and Rab 7 proteins that play critical roles in the fusion of autophagosomes to lysosomes. Autophagy inhibition by combination (DOX + CQ) enhanced the apoptotic cell death synergistically by increasing the cleavage of procaspase-3 and PARP1. Further, a prior incubation of HeLa cells with Z-VAD-FMK (a pan-caspase inhibitor) for 4 h, suppressed the combination (DOX + CQ)-induced cell death. Our data suggest that a combination of DOX + CQ had a better anti-cancer efficacy in HeLa cells than either of the drugs alone. Thus, CQ, as a repurposed drug, may hold the potential to synergize anticancer effects of DOX in cervical cancer cells.

Autophagy: Dual roles and perspective for clinical treatment of colorectal cancer

Colorectal cancer (CRC) raises concerns to people because of its high recurrence and metastasis rate, diagnosis challenges, and poor prognosis. Various studies have shown the association of altered autophagy with tumorigenesis, tumor-stroma interactions, and resistance to cancer therapy in CRC. Autophagy is a highly conserved cytosolic catabolic process in eukaryotes that plays distinct roles in CRC occurrence and progression. In early tumorigenesis, autophagy may inhibit tumor growth through diverse mechanisms, whereas it exhibits a tumor promoting function in CRC progression. This different functions of autophagy in CRC occurrence and progression make developing therapies targeting autophagy complicated. In this review, we discuss the classification and process of autophagy as well as its dual roles in CRC, functions in the tumor microenvironment, cross-talk with apoptosis, and potential usefulness as a CRC therapeutic target.

Blocking autophagy with chloroquine aggravates lipid accumulation and reduces intracellular energy synthesis in hepatocellular carcinoma cells, both contributing to its anti-proliferative effect

PURPOSE

The autophagy inhibitor chloroquine enhances the effect of targeted therapy using tyrosine kinase inhibitor in liver cancer. We would like to further understand the specific mechanism by which chloroquine inhibits the proliferation of tumor cells.

METHODS

We used a human hepatocarcinoma cell line (HepG2) as cell culture model. In contrast to the control groups (treated only with complete medium), cells in experimental groups were treated either with complete medium + 40 ng/ml Hepatocyte growth factor (HGF), or with complete medium + 60 μM chloroquine or with complete medium + 40 ng/ml HGF + 60 μM chloroquine for 24 h. Cell number and ATP content were investigated using spectrophotometric assays. Cell proliferation and apoptosis were detected by immunohistochemistry. Cell morphological alterations were examined by Giemsa and H&E staining. Cellular lipid content was determined by Oil Red O staining and Triglyceride quantification assay. Autophagy-related proteins (LC3B and p62) and hepatocyte proliferation-related protein (S6K1) were examined using western blot. The autophagic flux of cells was assessed by mRFP-EGFP-LC3 transfection assay.

RESULTS

We found that chloroquine inhibited the proliferation of HepG2 cells, as evidenced by a decrease in cellular ATP content, Ki-67 and S6K1 protein expression and a reduction in cell number. This finding was associated with an increase in lipid content. As expected, chloroquine inhibited autophagy of HepG2 cells, as evidenced by the accumulation of LC3B-II and the significant upregulation of p62. mRFP-EGFP-LC3 transfection assay showed that indeed chloroquine blocked the autophagic flux in HepG2 cells.

CONCLUSION

Chloroquine impaired proliferation of HepG2 cells might be due to intracellular accumulation of lipids and inhibition of energy synthesis.

Inhibition of TLR7 and TLR9 Reduces Human Cholangiocarcinoma Cell Proliferation and Tumor Development

BACKGROUND

Toll-like receptors (TLRs) are key players in innate immunity and modulation of TLR signaling has been demonstrated to profoundly affect proliferation and growth in different types of cancer. However, the role of TLRs in human intrahepatic cholangiocarcinoma (ICC) pathogenesis remains largely unexplored.

AIMS

We set out to determine if TLRs play any role in ICCs which could potentially make them useful treatment targets.

METHODS

Tissue microarrays containing samples from 9 human ICCs and normal livers were examined immunohistochemically for TLR4, TLR7, and TLR9 expression. Proliferation of human ICC cell line HuCCT1 was measured by MTS assay following treatment with CpG-ODN (TLR9 agonist), imiquimod (TLR7 agonist), chloroquine (TLR7 and TLR9 inhibitor) and IRS-954 (TLR7 and TLR9 antagonist). The in vivo effects of CQ and IRS-954 on tumor development were also examined in a NOD-SCID mouse xenograft model of human ICC.

RESULTS

TLR4 was expressed in all normal human bile duct epithelium but absent in the majority (60%) of ICCs. TLR7 and TLR9 were expressed in 80% of human ICCs. However, TLR7 was absent in all cases of normal human bile duct epithelium and only one was TLR9 positive. HuCCT1 cell proliferation in vitro significantly increased following IMQ or CpG-ODN treatment (P < 0.03 and P < 0.002, respectively) but decreased with CQ (P < 0.02). In the mouse xenograft model there was significant reduction in size of tumors from CQ and IRS-954 treated mice compared to untreated controls.

CONCLUSION

TLR7 and TLR9 should be further explored for their potential as actionable targets in the treatment of ICC.

The Emerging Roles of Autophagy in Human Diseases

Autophagy, a process of cellular self-digestion, delivers intracellular components including superfluous and dysfunctional proteins and organelles to the lysosome for degradation and recycling and is important to maintain cellular homeostasis. In recent decades, autophagy has been found to help fight against a variety of human diseases, but, at the same time, autophagy can also promote the procession of certain pathologies, which makes the connection between autophagy and diseases complex but interesting. In this review, we summarize the advances in understanding the roles of autophagy in human diseases and the therapeutic methods targeting autophagy and discuss some of the remaining questions in this field, focusing on cancer, neurodegenerative diseases, infectious diseases and metabolic disorders.

Combination Chemotherapy with Cisplatin and Chloroquine: Effect of Encapsulation in Micelles Formed by Self-Assembling Hybrid Dendritic-Linear-Dendritic Block Copolymers

Clinical outcomes of conventional drug combinations are not ideal due to high toxicity to healthy tissues. Cisplatin (CDDP) is the standard component for many cancer treatments, yet its principal dose-limiting side effect is nephrotoxicity. Thus, CDDP is commonly used in combination with other drugs, such as the autophagy inhibitor chloroquine (CQ), to enhance tumor cell killing efficacy and prevent the development of chemoresistance. In addition, nanocarrier-based drug delivery systems can overcome chemotherapy limitations, decreasing side effects and increasing tumor accumulation. The aim of this study was to evaluate the toxicity of CQ and CDDP against tumor and non-tumor cells when used in a combined treatment. For this purpose, two types of micelles based on Pluronic^® F127 hybrid dendritic–linear–dendritic block copolymers (HDLDBCs) modified with polyester or poly(esteramide) dendrons derived from 2,2′-bis(hydroxymethyl)propionic acid (HDLDBC-bMPA) or 2,2′-bis(glycyloxymethyl)propionic acid (HDLDBC-bGMPA) were explored as delivery nanocarriers. Our results indicated that the combined treatment with HDLDBC-bMPA(CQ) or HDLDBC-bGMPA(CQ) and CDDP increased cytotoxicity in tumor cells compared to the single treatment with CDDP. Encapsulations demonstrated less short-term cytotoxicity individually or when used in combination compared to the free drugs. However, and more importantly, a low degree of cytotoxicity against non-tumor cells was maintained, even when drugs were given simultaneously.

Wnt/β-catenin Antagonists: Exploring New Avenues to Trigger Old Drugs in Alleviating Glioblastoma Multiforme

BACKGROUND

Glioblastoma multiforme is one of the most heterogenous primary brain tumor with high mortality. Nevertheless, of the current therapeutic approaches, survival rate remains poor with 12 to 15 months following preliminary diagnosis, this warrants the need for effective treatment modality. Wnt/β-catenin pathway is presumably the most noteworthy pathway up-regulated in almost 80% GBM cases contributing to tumor-initiation, progression and survival. Therefore, therapeutic strategies targeting key components of Wnt/β-catenin cascade using established genotoxic agents like temozolomide and pharmacological inhibitors would be an effective approach to modulate Wnt/β-catenin pathway. Recently, drug repurposing by means of effective combination therapy has gained importance in various solid tumors including GBM, by targeting two or more proteins in a single pathway, thereby possessing the ability to overcome the hurdle implicated by chemo-resistance in GBM.

OBJECTIVE

In this context, by employing computational tools, an attempt has been carried out to speculate the novel combinations against Wnt/β-catenin signaling pathway.

METHODS

We have explored the binding interactions of three conventional drugs namely temozolomide, metformin, chloroquine along with three natural compounds viz., epigallocatechin gallate, naringenin and phloroglucinol on the major receptors of Wnt/β-catenin signaling.

RESULTS

It was noted that all the experimental compounds possessed profound interaction with the two major receptors of Wnt/β-catenin pathway.

CONCLUSION

To the best of our knowledge, this study is the first of its kind to characterize the combined interactions of the afore-mentioned drugs on Wnt/β-catenin signaling in silico and this will putatively open up new avenues for combination therapies in GBM treatment.

TRIM39 deficiency inhibits tumor progression and autophagic flux in colorectal cancer via suppressing the activity of Rab7

The biological function of TRIM39, a member of TRIM family, remains largely unexplored in cancer, especially in colorectal cancer (CRC). In this study, we show that TRIM39 is upregulated in tumor tissues compared to adjacent normal tissues and associated with poor prognosis in CRC. Functional studies demonstrate that TRIM39 deficiency restrains CRC progression in vitro and in vivo. Our results further find that TRIM39 is a positive regulator of autophagosome–lysosome fusion. Mechanistically, TRIM39 interacts with Rab7 and promotes its activity via inhibiting its ubiquitination at lysine 191 residue. Depletion of TRIM39 inhibits CRC progression and autophagic flux in a Rab7 activity-dependent manner. Moreover, TRIM39 deficiency suppresses CRC progression through inhibiting autophagic degradation of p53. Thus, our findings uncover the roles as well as the relevant mechanisms of TRIM39 in CRC and establish a functional relationship between autophagy and CRC progression, which may provide promising approaches for the treatment of CRC.

New Trends for Antimalarial Drugs: Synergism between Antineoplastics and Antimalarials on Breast Cancer Cells

Chemotherapy plays a key role in breast cancer therapy, but drug resistance and unwanted side effects make the treatment less effective. We propose a new combination model that combines antineoplastic drugs and antimalarials for breast cancer therapy. Cytotoxic effects of two antineoplastic agents alone and in combination with several antimalarials on MCF-7 tumor cell line was evaluated. Different concentrations in a fixed ratio were added to the cultured cells and incubated for 48 h. Cell viability was evaluated using MTT and SRB assays. Synergism was evaluated using the Chou-Talalay method. The results indicate doxorubicin (DOX) and paclitaxel (PTX) alone at concentrations of their IC50 and higher are cell growth inhibitors. Mefloquine, artesunate, and chloroquine at concentrations of their IC50 demonstrate anti-cancer activity. In combination, almost all antimalarials demonstrate higher ability than DOX and PTX alone to decrease cell viability at concentrations of IC50 and lower than their IC50. The combination of chloroquine, artesunate and mefloquine with DOX and PTX was synergic (CI < 1). The combination of DOX and mefloquine after 48 h incubation demonstrated the highest cytotoxicity against MCF-7 cells, and the combination of DOX and artesunate was the most synergic. These results suggest antimalarials could act synergistically with DOX/PTX for breast cancer therapy.

Pharmacological Advances of Chloroquine and Hydroxychloroquine: From Antimalarials to Investigative Therapies in COVID-19

During the coronavirus disease 2019 (COVID-19) pandemic, numerous existing chemicals have been screened for antiviral potential against the emerging coronavirus severe acute respiratory syndrome coronavirus 2. Chloroquine and hydroxychloroquine, after exhibiting potent in vitro efficacy, have gained tremendous attention. Both therapeutics are derivatives of natural alkaloid quinine and were first synthesized to treat malaria. Thereafter, the pharmaceutical applications of the agents have expanded to many new areas. In this article, the medicinal history and pharmacological activities of chloroquine and hydroxychloroquine are summarized. Antimalarial, anti-inflammatory, antitumor, antiviral properties, and therapeutic potential in the emerging viral infection COVID-19 are discussed. Pharmacokinetics, adverse effects, and toxicities are reviewed.

Anti-malarial Drugs Reduce Vascular Smooth Muscle Cell Proliferation via Activation of AMPK and Inhibition of Smad3 Signaling

Objective

The aim of this study was to investigate the effects of 2 anti-malarial drugs, chloroquine (CQ) and hydroxychloroquine (HCQ), on inhibition of vascular smooth muscle cell (VSMC) proliferation both in vivo and in vitro via Adenosine monophosphate-activated protein kinase (AMPK) activation.

Methods

Protein and mRNA levels were determined by western blot analysis and real-time reverse transcription-polymerase chain reaction in primary rat VSMCs treated with CQ and HCQ, respectively. Cell proliferation was measured by flow cytometry and cell counting. Mice carotid arteries were ligated and treated with CQ or HCQ every other day for 3 weeks. Pathological changes of carotid arteries were visualized by both microscopy and fluorescence microscopy.

Results

CQ and HCQ increase AMPK phosphorylation in VSMCs. Both CQ and HCQ decrease platelet-derived growth factor-induced VSMC proliferation and cell cycle progression in an AMPK-dependent manner. In addition, CQ and HCQ inhibit Smad3 phosphorylation and VSMC proliferation induced by transforming growth factor-β1. Moreover, CQ and HCQ diminished neointimal proliferation in a mouse model of carotid artery ligation-induced neointima formation.

Conclusion

The results demonstrated that CQ and HCQ inhibit cell proliferation and cell cycle progression in VSMCs via the AMPK-dependent signaling pathway. Carotid artery ligation-induced intima thickness was reduced in mouse arteries treated with CQ or HCQ, suggesting a role for antimalarial drugs in treating atherosclerosis and restenosis.

Chloroquine Triggers Cell Death and Inhibits PARPs in Cell Models of Aggressive Hepatoblastoma

Background: Hepatoblastoma (HB) is the most common pediatric liver malignancy. Despite advances in chemotherapeutic regimens and surgical techniques, the survival of patients with advanced HB remains poor, underscoring the need for new therapeutic approaches. Chloroquine (CQ), a drug used to treat malaria and rheumatologic diseases, has been shown to inhibit the growth and survival of various cancer types. We examined the antineoplastic activity of CQ in cell models of aggressive HB. Methods: Seven human HB cell models, all derived from chemoresistant tumors, were cultured as spheroids in the presence of relevant concentrations of CQ. Morphology, viability, and induction of apoptosis were assessed after 48 and 96 h of CQ treatment. Metabolomic analysis and RT-qPCR based Death Pathway Finder array were used to elucidate the molecular mechanisms underlying the CQ effect in a 2-dimensional cell culture format. Quantitative western blotting was performed to validate findings at the protein level. Results: CQ had a significant dose and time dependent effect on HB cell viability both in spheroids and in 2-dimensional cell cultures. Following CQ treatment HB spheroids exhibited increased caspase 3/7 activity indicating the induction of apoptotic cell death. Metabolomic profiling demonstrated significant decreases in the concentrations of NAD⁺ and aspartate in CQ treated cells. In further investigations, oxidation of NAD⁺ decreased as consequence of CQ treatment and NAD⁺/NADH balance shifted toward NADH. Aspartate supplementation rescued cells from CQ induced cell death. Additionally, downregulated expression of PARP1 and PARP2 was observed. Conclusions: CQ treatment inhibits cell survival in cell models of aggressive HB, presumably by perturbing NAD⁺ levels, impairing aspartate bioavailability, and inhibiting PARP expression. CQ thus holds potential as a new agent in the management of HB.

Toward fully exploiting the therapeutic potential of marketed pharmaceuticals: the use of octreotide and chloroquine in oncology

Pleiotropy in biological systems and their targeting allows many pharmaceuticals to be used for multiple therapeutic purposes. Fully exploiting the therapeutic properties of drugs that are already marketed would be highly advantageous. This is especially the case in the field of oncology, where the ineffectiveness of typical anticancer agents is a common issue, while the development of novel anticancer agents is a costly and particularly time-consuming process. Octreotide and chloroquine are two pharmaceuticals that exhibit profound antitumorigenic activities. However, the current therapeutic use of octreotide is restricted primarily to the management of acromegaly and neuroendocrine tumors, both of which are rare medical conditions. Similarly, chloroquine is used mainly for the treatment of malaria, which is designated as a rare disease in Western countries. This limited exploitation contradicts the experimental findings of numerous studies outlining the possible expansion of the use of octreotide to include the treatment of common human malignancies and the repositioning of chloroquine in oncology. Herein, we review the current knowledge on the antitumor function of these two agents stemming from preclinical or clinical experimentation. In addition, we present in silico evidence on octreotide potentially binding to multiple Wnt-pathway components. This will hopefully aid in the design of new efficacious anticancer therapeutic regimens with minimal toxicity, which represents an enormous unmet demand in oncology.

Chloroquine exerts antitumor effects on NB4 acute promyelocytic leukemia cells and functions synergistically with arsenic trioxide

Chloroquine (CQ) has been confirmed to exhibit antitumor effects on different types of cancer cell, but whether it exerts the same effect on acute promyelocytic leukemia (APL) cells remains to be confirmed. In the present study, the effects of various concentrations of CQ on the growth, apoptosis and cell cycle distribution of NB4 cells, as well as the potential mechanisms underlying these effects, were examined. The combined effect of CQ and arsenic trioxide (ATO) on the growth of NB4 cells was also determined. The results of the present study demonstrated that CQ treatment inhibited cell proliferation, and induced mitochondrial pathway apoptosis and S phase arrest in a dose-dependent manner by regulating apoptosis- and cell cycle-related proteins. CQ and ATO had a synergistic effect on the growth inhibition of NB4 cells, which may have been induced through the inhibition of autophagy. In conclusion, the results of the present study indicated that CQ exhibits a cytotoxic effect on NB4 cells and has a synergistic effect when combined with ATO, which thereby improves the curative effect of ATO on APL.

Repurposing Drugs in Oncology (ReDO)-chloroquine and hydroxychloroquine as anti-cancer agents

Chloroquine (CQ) and hydroxychloroquine (HCQ) are well-known 4-aminoquinoline antimalarial agents. Scientific evidence also supports the use of CQ and HCQ in the treatment of cancer. Overall, preclinical studies support CQ and HCQ use in anti-cancer therapy, especially in combination with conventional anti-cancer treatments since they are able to sensitise tumour cells to a variety of drugs, potentiating the therapeutic activity. Thus far, clinical results are mostly in favour of the repurposing of CQ. However, over 30 clinical studies are still evaluating the activity of both CQ and HCQ in different cancer types and in combination with various standard treatments. Interestingly, CQ and HCQ exert effects both on cancer cells and on the tumour microenvironment. In addition to inhibition of the autophagic flux, which is the most studied anti-cancer effect of CQ and HCQ, these drugs affect the Toll-like receptor 9, p53 and CXCR4-CXCL12 pathway in cancer cells. In the tumour stroma, CQ was shown to affect the tumour vasculature, cancer-associated fibroblasts and the immune system. The evidence reviewed in this paper indicates that both CQ and HCQ deserve further clinical investigations in several cancer types. Special attention about the drug (CQ versus HCQ), the dose and the schedule of administration should be taken in the design of new trials.

Chloroquine is a potent pulmonary vasodilator that attenuates hypoxia-induced pulmonary hypertension

BACKGROUND AND PURPOSE

Sustained pulmonary vasoconstriction and excessive pulmonary vascular remodelling are two major causes of elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension. The purpose of this study was to investigate whether chloroquine induced relaxation in the pulmonary artery (PA) and attenuates hypoxia-induced pulmonary hypertension (HPH).

EXPERIMENTAL APPROACH

Isometric tension was measured in rat PA rings pre-constricted with phenylephrine or high K⁺ solution. PA pressure was measured in mouse isolated, perfused and ventilated lungs. Fura-2 fluorescence microscopy was used to measure cytosolic free Ca²⁺ concentration levels in PA smooth muscle cells (PASMCs). Patch-clamp experiments were performed to assess the activity of voltage-dependent Ca²⁺ channels (VDCCs) in PASMC. Rats exposed to hypoxia (10% O₂ ) for 3 weeks were used as the model of HPH or Sugen5416/hypoxia (SuHx) for in vivo experiments.

KEY RESULTS

Chloroquine attenuated agonist-induced and high K⁺ -induced contraction in isolated rat PA. Pretreatment with l-NAME or indomethacin and functional removal of endothelium failed to inhibit chloroquine-induced PA relaxation. In PASMC, extracellular application of chloroquine attenuated store-operated Ca²⁺ entry and ATP-induced Ca²⁺ entry. Furthermore, chloroquine also inhibited whole-cell Ba²⁺ currents through VDCC in PASMC. In vivo experiments demonstrated that chloroquine treatment ameliorated the HPH and SuHx models.

CONCLUSIONS AND IMPLICATIONS

Chloroquine is a potent pulmonary vasodilator that may directly or indirectly block VDCC, store-operated Ca²⁺ channels and receptor-operated Ca²⁺ channels in PASMC. The therapeutic potential of chloroquine in pulmonary hypertension is probably due to the combination of its vasodilator, anti-proliferative and anti-autophagic effects.

In vitro and in vivo antitumor effects of chloroquine on oral squamous cell carcinoma

Chloroquine, which is a widely used antimalarial drug, has been reported to exert anticancer activity in some tumor types; however, its potential effects on oral squamous cell carcinoma (OSCC) remain unclear. The present study aimed to explore the effects and possible underlying mechanisms of chloroquine against OSCC. MTT and clonogenic assays were conducted to evaluate the effects of chloroquine on the human OSCC cell lines SCC25 and CAL27. Cell cycle progression and apoptosis were detected using flow cytometry. Autophagy was monitored using microtubule-associated protein 1A/1B-light chain 3 as an autophagosomal marker. In order to determine the in vivo antitumor effects of chloroquine on OSCC, a CAL27 xenograft model was used. The results demonstrated that chloroquine markedly inhibited the proliferation and the colony-forming ability of both OSCC cell lines in a dose- and time-dependent manner in vitro. Chloroquine also disrupted the cell cycle, resulting in the cell cycle arrest of CAL27 and SCC25 cells at G₀/G₁ phase, via downregulation of cyclin D1. In addition, chloroquine inhibited autophagy, and induced autophagosome and autolysosome accumulation in the cytoplasm, thus interfering with degradation; however, OSCC apoptosis was barely affected by chloroquine. The results of the in vivo study demonstrated that chloroquine effectively inhibited OSCC tumor growth in the CAL27 xenograft model. In conclusion, the present study reported the in vitro and in vivo antitumor effects of chloroquine on OSCC, and the results indicated that chloroquine may be considered a potent therapeutic agent against human OSCC.

Glucose Restriction Combined with Autophagy Inhibition and Chemotherapy in HCT 116 Spheroids Decreases Cell Clonogenicity and Viability Regulated by Tumor Suppressor Genes

Drug resistance is a prevalent phenomenon that decreases the efficacy of cancer treatments and contributes to cancer progression and metastasis. Weakening drug-resistant cancer cells prior to chemotherapy is a potential strategy to combat chemoresistance. One approach to damage resistant cancer cells is modulation of nutritional intake. The combination of nutrient restriction with targeted compound treatment results in pronounced molecular changes. This study provides valuable information about augmenting existing chemotherapeutic regimes with simultaneous glucose restriction and autophagy inhibition in colorectal cancer cells. In this study, we explore the chemical pathways that drive the cellular response to nutrient restriction, autophagy inhibition, and the chemotherapy irinotecan using global quantitative proteomics and imaging mass spectrometry. We determined that significant pathways were altered including autophagy and metabolism via glycolysis, gluconeogenesis, and sucrose degradation. We also found that period circadian clock 2 (PER2), a tumor suppressor protein, was significantly up-regulated only when glucose was restricted with autophagy inhibition and chemotherapy. The upstream regulators of these differentially regulated pathways were determined to have implications in cancer, showing an increase in tumor suppressor proteins and a decrease in nuclear protein 1 (NUPR1) an important protein in chemoresistance. We also evaluated the phenotypic response of these cells and discovered autophagy inhibition and chemotherapy treatment increased apoptosis and decreased cell clonogenicity and viability. When glucose restriction was combined with autophagy inhibition and chemotherapy, all of the phenotypic results were intensified. In sum, our results indicate that glucose metabolism is of great importance in the ability of cancer cells to survive chemotherapy. By weakening cancer cells with glucose restriction and autophagy inhibition prior to chemotherapy, cancer cells become more sensitive to therapy.

New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets

Colorectal cancer (CRC), despite numerous therapeutic and screening attempts, still remains a major life-threatening malignancy. CRC etiology entails both genetic and environmental factors. Macroautophagy/autophagy and the unfolded protein response (UPR) are fundamental mechanisms involved in the regulation of cellular responses to environmental and genetic stresses. Both pathways are interconnected and regulate cellular responses to apoptotic stimuli. In this review, we address the epidemiology and risk factors of CRC, including genetic mutations leading to the occurrence of the disease. Next, we discuss mutations of genes related to autophagy and the UPR in CRC. Then, we discuss how autophagy and the UPR are involved in the regulation of CRC and how they associate with obesity and inflammatory responses in CRC. Finally, we provide perspectives for the modulation of autophagy and the UPR as new therapeutic options for CRC treatment.

Therapeutic effect of hydroxychloroquine on colorectal carcinogenesis in experimental murine colitis

Chronic inflammation in the intestine is a strong risk factor for colitis-associated colorectal cancer (CAC). Hydroxychloroquine (HCQ) is widely used as an anti-inflammatory drug in the treatment of immune-mediated inflammatory disorders and various tumors. However, little is known regarding the effects of HCQ on colitis-associated tumorigenesis. In this study, mice treated with HCQ showed a significant reduction in early-stage colitis following azoxymethane (AOM)/dextran sodium sulfate (DSS) administration, as well as a remarkable inhibition of colonic tumorigenesis and tumor growth at late stages of CAC. Mechanistically, the therapeutic effects of HCQ were attributed to inhibition of inflammatory responses and production of mutagenic reactive oxygen species (ROS) in immune cells and subsequent promotion of apoptosis and cell cycle arrest in tumor cells. Furthermore, we found that HCQ inhibited the production of inflammatory cytokines and ROS in response to toll-like receptor 4 (TLR4) activation in macrophages. Our data presented herein may help guide the clinical use of HCQ as a prevention and treatment strategy for CAC.

Autophagy inhibition facilitates erlotinib cytotoxicity in lung cancer cells through modulation of endoplasmic reticulum stress

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have revolutionized the treatment for non-small cell lung cancer patients, but acquired resistance limit the efficiency of this treatment. As a homeostatic cellular recycling mechanism, autophagy has been proposed to participate in the EGFR-TKI resistance. However, the role of autophagy in lung cancer treatment and the underlying mechanisms have not been clarified. In this study, we found the sensitivity to erlotinib, a well-used EGFR-TKI, was correlated with basal autophagy level. Erlotinib was able to induce autophagy not only in TKI-sensitive, but also TKI-resistant cancer cells. Inhibition of autophagy significantly enhanced cytotoxicity of erlotinib in TKI-resistant cancer cells via modulation of endoplasmic reticulum (ER) stress induced apoptosis. In this process, CCAAT/enhancer binding protein homologous protein (CHOP) acted as an executioner. Downregulation of CHOP with siRNA blocked the autophagy inhibition and erlotinib co-treatment induced apoptosis and prevented cancer cells from this co-treatment-induced cell death. Our findings suggest that autophagy inhibition overcomes erlotinib resistance through modulation of ER stress mediated apoptosis.

Chloroquine enhances TRAIL-mediated apoptosis through up-regulation of DR5 by stabilization of mRNA and protein in cancer cells

Chloroquine (CQ), an anti-malarial drug, has immune-modulating activity and lysosomotropic activity. In this study, we investigated CQ sensitizes TRAIL-mediated apoptosis in human renal cancer Caki cells. Combination of CQ and TRAIL significantly induces apoptosis in human renal cancer Caki cells and various human cancer cells, but not in normal mouse kidney cells (TMCK-1) and human mesangial cells (MC). CQ up-regulates DR5 mRNA and protein expression in a dose- and time- dependent manner. Interestingly, CQ regulates DR5 expression through the increased stability in the mRNA and protein of DR5, rather than through the increased transcriptional activity of DR5. Moreover, we found that CQ decreased the expression of Cbl, an E3 ligase of DR5, and knock-down of Cbl markedly enhanced DR5 up-regulation. Other lysosomal inhibitors, including monensin and nigericin, also up-regulated DR5 and sensitized TRAIL-mediated apoptosis. Therefore, this study demonstrates that lysosomal inhibition by CQ may sensitize TRAIL-mediated apoptosis in human renal cancer Caki cells via DR5 up-regulation.

Chloroquine inhibits hepatocellular carcinoma cell growth in vitro and in vivo

Recently, chloroquine (CQ) has been widely used to improve the efficacy of different chemotherapy drugs to treat tumors. However, the effects of single treatment of CQ on liver cancer have not been investigated. In the present study, we examined the effects of CQ on the growth and viability of liver cancer cells in vitro and in vivo, and revealed that CQ treatment triggered G0/G1 cell cycle arrest, induced DNA damage and apoptosis in a dose- and time-dependent manner in liver cancer cells. Moreover, administration of CQ to tumor-bearing mice suppressed the tumor growth in an orthotopic xenograft model of liver cancer. These findings extend our understanding and suggest that CQ could be repositioned as a treatment option for liver cancer as a single treatment or in combination.

A synthesized butyrolactone derivative in combination with chloroquine can inhibit cancer cell growth and lysosome vacuolation induced by chloroquine in A549 lung cancer cells

3BDO in combination with chloroquine could elevate the Na⁺,K⁺-ATPase activity and decrease the expression of competing endogenous non-coding RNA TGFB2-OT1. Therefore, ​ the combination inhibited the cells growth and lysosomal vacuolation induced by CQ.

Time to use a dose of Chloroquine as an adjuvant to anti-cancer chemotherapies

Chloroquine, a drug used for over 80 years to treat and prevent malaria and, more recently, to treat autoimmune diseases, is very safe but has a plethora of dose-dependent effects. By increasing pH in acidic compartments it inhibits for example lysosomal enzymes. In the context of cancer, Chloroquine was found to have direct effects on different types of malignancies that could potentiate chemotherapies. For example, the anti-malaria drug may inhibit both the multidrug-resistance pump and autophagy (mechanisms that tumor cells may use to resist chemotherapies), intercalate in DNA and enhance the penetration of chemotherapeutic drugs in cells or solid cancer tissues. However, these activities were mostly demonstrated at high doses of Chloroquine (higher than 10mg/kg or 10mg/l i.e. ca. 31μM). Nevertheless, it was reported that daily uptake of clinically acceptable doses (less than 10mg/kg) of Chloroquine in addition to chemo-radio-therapy increases the survival of glioblastoma patients (Sotelo et al., 2006; Briceno et al., 2007). However, the optimal dose and schedule of this multi-active drug with respect to chemotherapy has never been experimentally determined. The present article reviews the several known direct and indirect effects of different doses of Chloroquine on cancer and how those effects may indicate that a fine tuning of the dose/schedule of Chloroquine administration versus chemotherapy may be critical to obtain an adjuvant effect of Chloroquine in anti-cancer treatments. We anticipate that the appropriate (time and dose) addition of Chloroquine to the standard of care may greatly and safely potentiate current anti-cancer treatments.

The utility of chloroquine in cancer therapy

BACKGROUND

The anti-malarial drug chloroquine has recently been discovered as a novel anti-tumor agent. This article is to review the recent development of chloroquine being used in cancer therapy.

METHODS

PubMed, ScienceDirect and ClinicalKey served as the major databases. Key words included 'chloroquine', 'cancer', and 'autophagy'. The publication date was up to June 2015.

RESULTS

Chloroquine mainly executes its anti-tumor function through inhibition of autophagy. It can accumulate inside the lysosome resulting in lysosomal membrane permeabilization (LMP) which will eventually lead to apoptosis. Chloroquine has been shown to stabilize p53 and induce p53-dependent apoptosis or cell cycle arrest. It can also inhibit ABC (ATP-binding cassette) family protein. The anti-cancer effect of chloroquine has been observed both in vitro and in vivo. However, it is considered more as a potential chemotherapy and radiotherapy sensitizer rather than an antineoplastic.

CONCLUSION

Although the utility of chloroquine is promising in cancer therapy, some safety issues have been brought to attention, and further studies on safety profile and the signs of clinical activity of chloroquine including its derivatives should be conducted.

Effect of toll-like receptor 7 and 9 targeted therapy to prevent the development of hepatocellular carcinoma

BACKGROUND & AIMS

Chronic liver disease is a predisposing factor for development of hepatocellular carcinoma (HCC). Toll-like receptors play a crucial role in immunity against microbial pathogens and recent evidence suggests that they may also be important in pathogenesis of chronic liver disease. The purpose of this study was to determine whether TLR7 and TLR9 are potential targets for prevention and progression of HCC.

METHODS

Tissue microarrays containing liver samples from patients with cirrhosis, viral hepatitis and HCC were examined for expression of TLR7 and TLR9 and the data obtained was validated in liver specimens from the hospital archives. Proliferation of human HCC cell lines was studied following stimulation of TLR7 and TLR9 using agonists (imiquimod and CpG-ODN respectively) and inhibition with a specific antagonist (IRS-954) or chloroquine. The effect of these interventions was confirmed in a xenograft model and diethylnitrosamine (DEN)/nitrosomorpholine (NMOR)-induced model of HCC.

RESULTS

TLR7 and TLR9 expression was up-regulated in human HCC tissue. Proliferation of HuH7 cells in vitro increased significantly in response to stimulation of TLR7. TLR7 and TLR9 inhibition using IRS-954 or chloroquine significantly reduced HuH7 cell proliferation in vitro and inhibited tumour growth in the mouse xenograft model. HCC development in the DEN/NMOR rat model was also significantly inhibited by chloroquine (P < 0.001).

CONCLUSION

The data suggest that inhibiting TLR7 and TLR9 with IRS-954 or chloroquine could potentially be used as a novel therapeutic approach for preventing HCC development and/or progression in susceptible patients.

Inhibition of autophagy by chloroquine potentiates synergistically anti-cancer property of artemisinin by promoting ROS dependent apoptosis

Artemisinin (ART) is a well-known anti-malarial drug, and recently it is shown prospective to selectively kill cancer cells. But low potency makes it inappropriate for use as an anticancer drug. In this study, we modulated the ART-induced autophagy to increase Potency of ART as an anticancer agent. ART reduced the cell viability and colony forming ability of non-small lung carcinoma (A549) cells and it was non-toxic against normal lung (WI38) cells. ART induced autophagy at the early stage of treatment. Pre-treatment with chloroquine (CQ) and followed by ART treatment had synergistic combination index (CI) for cell death. Inhibition of autophagy by CQ pre-treatment led to accumulation of acidic vacuoles (AVOs) which acquainted with unprocessed damage mitochondria that subsequently promoted ROS generation, and resulted releases of Cyt C in cytosol that caused caspase-3 dependent apoptosis cell death in ART-treated A549 cells. Scavenging of ROS by antioxidant N-acetyl-cysteine (NAC) inhibited caspase-3 activity and rescued the cells from apoptosis. Similar effects were observed in other cancer cells SCC25 and MDA-MB-231. The appropriate manipulation of autophagy by using CQ provides a powerful strategy to increase the Potency of selective anticancer property of ART.

SKLB316, a novel small-molecule inhibitor of cell-cycle progression, induces G2/M phase arrest and apoptosis in vitro and inhibits tumor growth in vivo

Benzothiazole derivatives have received considerable attentions for their potencies in cancer therapy. In the present study, we reported that SKLB316, a novel synthesized benzothiazole derivative, exhibits activities to inhibit colorectal and pancreatic cancer in vitro and in vivo by inducing G2/M cell cycle arrest and apoptosis. In vitro, it exhibited significant anti-proliferative activities against human cancer cells derived from different histotypes including the colorectal cancer cell line HCT116 and pancreatic cancer cell line CFPAC-1. We chose these cell lines to study the possible anti-tumor mechanism because they are sensitive to SKLB316 treatment. Flow cytometry assays showed that SKLB316 could induce G2/M cell cycle arrest. Mechanistically, SKLB316 could decrease the activities of cdc2/cyclin B1 complex, including decreasing the synthesis of cyclin B1, cdc2 and cdc25c, while accumulating the levels of phosphorylated cdc2 (Tyr15) and checkpoint kinase 2. SKLB316 could also decrease the level of cyclin E and A2. Moreover, SKLB316 could induce cancer cell apoptosis, which was associated with activation of caspase 9, downregulation of Bcl-2 and upregulation of Bax. SKLB316 could also decrease the mitochondrial membrane potential and induce the generation of reactive oxygen species in cells. The results implied that SKLB316 may induce apoptosis via the mitochondria-mediated apoptotic pathway. Moreover, SKLB316 could suppress the growth of established colorectal and pancreatic cancer tumors in nude mice without causing obvious side effects. TUNEL assays confirmed that SKLB316 could also induce tumor cell apoptosis in vivo. Taken together, these findings demonstrate the potential value of SKLB316 as a novel anti-tumor drug candidate.

Temsirolimus and chloroquine cooperatively exhibit a potent antitumor effect against colorectal cancer cells

PURPOSE

Temsirolimus (TEM) is a novel, water-soluble mammalian target of rapamycin (mTOR) inhibitor that has shown activity against a wide range of cancers in preclinical models, but its efficacy against colorectal cancer (CRC) has not been fully explored.

METHODS

We evaluated the antitumor effect of TEM in CRC cell lines (CaR-1, HT-29, Colon26) in vitro and in vivo. In vitro, cell growth inhibition was assessed using a MTS assay. Apoptosis induction and cell cycle effects were measured using flow cytometry. Modulation of mTOR signaling was measured using immunoblotting. Antitumor activity as a single agent was evaluated in a mouse subcutaneous tumor model of CRC. The effects of adding chloroquine, an autophagy inhibitor, to TEM were evaluated in vitro and in vivo.

RESULTS

In vitro, TEM was effective in inhibiting the growth of two CRC cell lines with highly activated AKT, possibly through the induction of G1 cell cycle arrest via a reduction in cyclin D1 expression, whereas TEM reduced HIF-1α and VEGF in all three cell lines. In a mouse subcutaneous tumor model, TEM inhibited the growth of tumors in all cell lines, not only through direct growth inhibition but also via an anti-angiogenic effect. We also explored the effects of adding chloroquine, an autophagy inhibitor, to TEM. Chloroquine significantly potentiated the antitumor activity of TEM in vitro and in vivo. Moreover, the combination therapy triggered enhanced apoptosis, which corresponded to an increased Bax/Bcl-2 ratio.

CONCLUSIONS

Based on these data, we propose TEM with or without chloroquine as a new treatment option for CRC.

Suppression of autophagy by chloroquine sensitizes 5-fluorouracil-mediated cell death in gallbladder carcinoma cells

Autophagy1 is a complex of adaptive cellular response that enhances cancer cell survival in the face of cellular stresses such as chemothery. Here we show that in human gallbladder carcinoma (GBC) cells lines, SGC-996 and GBC-SD, autophagy is induced by the DNA damaging agent 5-fluorouracil (5-FU). While in combination with the pre-treatment of chloroquine (CQ), a inhibitor of autophagy, the inhibition of 5-FU to the proliferation and viability of GBC cells was potentiated. Furthermore, 5-FU treatment resulted in a general increase of the apoptotic rate and G0/G1 arrest of GBC cells, and the effect was potentiated by CQ pre-treatment. Since 5-FU induced autophagy in GBC cells, and CQ inhibited autophagy, our findings suggest a possible mechanism that CQ inhibited 5-FU-induced autophagy, which modified the cytotoxicity of 5-FU. The combination therapy of CQ and 5-FU should be considered as an effective strategy for the treatment of gallbladder carcinoma.

Inhibition of 6-phosphofructo-2-kinase (PFKFB3) induces autophagy as a survival mechanism

Background

Unlike glycolytic enzymes that directly catabolize glucose to pyruvate, the family of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFKFBs) control the conversion of fructose-6-phosphate to and from fructose-2,6-bisphosphate, a key regulator of the glycolytic enzyme phosphofructokinase-1 (PFK-1). One family member, PFKFB3, has been shown to be highly expressed and activated in human cancer cells, and derivatives of a PFKFB3 inhibitor, 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO), are currently being developed in clinical trials. However, the effectiveness of drugs such as 3PO that target energetic pathways is limited by survival pathways that can be activated by reduced ATP and nutrient uptake. One such pathway is the process of cellular self-catabolism termed autophagy. We hypothesized that the functional glucose starvation induced by inhibition of PFKFB3 in tumor cells would induce autophagy as a pro-survival mechanism and that inhibitors of autophagy could increase the anti-tumor effects of PFKFB3 inhibitors.

Results

We found that selective inhibition of PFKFB3 with either siRNA transfection or 3PO in HCT-116 colon adenocarcinoma cells caused a marked decrease in glucose uptake simultaneously with an increase in autophagy based on LC3-II and p62 protein expression, acridine orange fluorescence of acidic vacuoles and electron microscopic detection of autophagosomes. The induction of autophagy caused by PFKFB3 inhibition required an increase in reactive oxygen species since N-acetyl-cysteine blocked both the conversion of LC3-I to LC3-II and the increase in acridine orange fluorescence in acidic vesicles after exposure of HCT-116 cells to 3PO. We speculated that the induction of autophagy might protect cells from the pro-apoptotic effects of 3PO and found that agents that disrupt autophagy, including chloroquine, increased 3PO-induced apoptosis as measured by double staining with Annexin V and propidium iodide in both HCT-116 cells and Lewis lung carcinoma (LLC) cells. Chloroquine also increased the anti-growth effect of 3PO against LLCs in vivo and resulted in an increase in apoptotic cells within the tumors.

Conclusions

We conclude that PFKFB3 inhibitors suppress glucose uptake, which in turn causes an increase in autophagy. The addition of selective inhibitors of autophagy to 3PO and its more potent derivatives may prove useful as rational combinations for the treatment of cancer.

Inhibition of autophagy with chloroquine is effective in melanoma

BACKGROUND

Cancer cells adapt to the stress resulting from accelerated cell growth and a lack of nutrients by activation of the autophagy pathway. Two proteins that allow cell growth in the face of metabolic stress and hypoxia are hypoxia-inducible factor-1α (HIF-1α) and heat shock protein 90 (Hsp 90). We hypothesize that chloroquine (CQ), an antimalarial drug that inhibits autophagosome function, in combination with either echinomycin, a HIF-1α inhibitor, or 17-dimethylaminoethylamino-17-dimethoxygeldanamycin (17-DMAG), an Hsp 90 inhibitor, will result in cytotoxicity in melanoma.

MATERIALS AND METHODS

Multiple human melanoma cell lines (BRAF wild-type and mutant) were tested in vitro with CQ in combination with echinomycin or 17-DMAG. These treatments were performed in hypoxic (5% O2) and normoxic (18% O2) conditions. Mechanism of action was determined through Western blot of autophagy-associated proteins HIF-1α and Hsp 90.

RESULTS

Chloroquine, echinomycin, and 17-DMAG each induced cytotoxicity in multiple human melanoma cell lines, in both normoxia and hypoxia. Chloroquine combined with echinomycin achieved synergistic cytotoxicity under hypoxic conditions in multiple melanoma cell lines (BRAF wild-type and mutant). Western blot analysis indicated that echinomycin reduced HIF-1α levels, both alone and in combination with CQ. Changes in LC3 flux indicated inhibition of autophagy at the level of the autophagosome by CQ therapy.

CONCLUSIONS

Targeting autophagy with the antimalarial drug CQ may be an effective cancer therapy in melanoma. Sensitivity to chloroquine is independent of BRAF mutational status. Combining CQ with the HIF-1α inhibitor echinomycin improves cytotoxicity in hypoxic conditions.

Unfolded protein response to autophagy as a promising druggable target for anticancer therapy

The endoplasmic reticulum (ER) is responsible for protein processing. In rapidly proliferating tumor cells, the ER tends to be overloaded with unfolded and misfolded proteins due to high metabolic demand. With the limited protein-folding capacity of the ER, tumor cells often suffer from more ER stress than do normal cells. Thus, cellular stress responses to cope with ER stress, such as the unfolded protein response (UPR) and autophagy, might be more activated in cancer cells than in normal cells. The complex signaling pathways from the UPR to autophagy provide promising druggable targets; a number of UPR/autophagy-targeted anticancer agents are currently in development in preclinical and clinical studies. In this short review we will discuss the potential anticancer efficacy of modulators of cellular stress responses, especially UPR and autophagy, on the basis of their signaling pathways. In addition, the current developmental status of the UPR/autophagy-targeted agents will be discussed.

Resistance of colon cancer to 5-fluorouracil may be overcome by combination with chloroquine, an in vivo study

Autophagy is a complex of adaptive cellular response that enhances cancer cell survival in the face of cellular stresses such as chemotherapy. Recently, chloroquine diphosphate (CQ), a widely used antimalarial drug, has been studied as a potential inhibitor of autophagy. Here, we aimed to investigate the role of CQ in potentiating the effect of 5-fluorouracil (5-FU), the chemotherapeutic agent of first choice for the treatment of colorectal cancer, in an animal model of colon cancer. The mouse colon cancer cell line colon26 was used. For the in-vivo study, colon26 cells were injected subcutaneously into BALB/c mice, which were treated with saline as a control, CQ (50 mg/kg/day), 5-FU (30 mg/kg/day), or the combination therapy (CQ plus 5-FU). The tumor volume ratio and body weight were monitored. After the sacrifice, tumor tissue protein extracts and tumor sections were prepared and subjected to immunoblotting for the analysis of autophagy-related and apoptosis-related proteins, and the terminal transferase uridyl end labeling assay. The combination of CQ resulted in the inhibition of 5-FU-induced autophagy and a significant enhancement in the 5-FU-induced inhibition of tumor growth. Furthermore, the combination treatment of CQ and 5-FU resulted in a significant increase in the ratio of apoptotic cells compared with other treatments. The expression levels of the proapoptotic proteins, namely Bad and Bax, were increased by the CQ treatment in the protein extracts from tumors. Our findings suggest that the combination therapy of CQ and 5-FU should be considered as an effective strategy for the treatment of colorectal cancer.