Inhibition of MEK/ERK activation attenuates autophagy and potentiates pemetrexed-induced activity against HepG2 hepatocellular carcinoma cells

Autophagy-based therapy for hepatocellular carcinoma: from standard treatments to combination therapy, oncolytic virotherapy, and targeted nanomedicines

Human hepatocellular carcinoma (HCC) has been identified as a significant cause of mortality worldwide. In recent years, extensive research has been conducted to understand the underlying mechanisms of autophagy in the pathogenesis of the disease, with the aim of developing novel therapeutic agents. Targeting autophagy with conventional therapies in invasive HCC has opened up new opportunities for treatment. However, the emergence of resistance and the immunosuppressive tumor environment highlight the need for combination therapy or specific targeting, as well as an efficient drug delivery system to ensure targeted tumor areas receive sufficient doses without affecting normal cells or tissues. In this review, we discuss the findings of several studies that have explored autophagy as a potential therapeutic approach in HCC. We also outline the potential and limitations of standard therapies for autophagy modulation in HCC treatment. Additionally, we discuss how different combination therapies, nano-targeted strategies, and oncolytic virotherapy could enhance autophagy-based HCC treatment in future research.

Lentinan mitigates pemetrexed chemoresistance by the PI3K/Akt pathway in non-small cell lung cancer

Pemetrexed is a folate analog metabolic inhibitor that is given for therapy of non-small cell lung cancer (NSCLC). Drug resistance affects the efficacy of pemetrexed in NSCLC. Lentinan is a polysaccharide extracted from Shiitake mushrooms which has antitumor roles in multiple cancers, including lung cancer. However, the effects of lentinan on pemetrexed resistance in NSCLC remain unclear. In present study, The pemetrexed-resistant NSCLC cells were established and exposed to pemetrexed and lentinan. Oxidative stress was investigated via mitochondrial membrane potential (JC-1 staining), levels of MDA and SOD.The phosphorylation and total of PI3K and Akt levels were actuated using specific activator 740Y-P and measured through western blot. We observed that Lentinan decreased IC50 of pemetrexed in resistant NSCLC cells. Lentinan aggravated pemetrexed-induced proliferation inhibition of resistant NSCLC cells via reducing PCNA levels. Lentinan exacerbated pemetrexed-triggered oxidative stress through increasing ROS and MDA levels, and reducing mitochondrial membrane potential and SOD levels. Lentinan inhibited PI3K/Akt signaling activation in pemetrexed-treated cells. Activated PI3K/Akt pathway using activator 740Y-P reversed the effects of lentinan on pemetrexed-mediated proliferation inhibition and oxidative stress. Our findings uncover that Lentinan mitigates pemetrexed resistance in NSCLC through inhibiting cell proliferation and inducing oxidative stress by suppressing PI3K/Akt signaling.

Simultaneous activation and blockade of autophagy to fight hepatocellular carcinoma

Autophagy is considered a target for cancer treatment, although few compounds manipulating this process have been added to the anticancer arsenal in humans. Pharmacological manipulation of autophagy has therefore been considered in the treatment and chemosensitization of hepatocellular carcinoma (HCC), a heterogeneous malignancy that remains difficult to treat (limited impact of genomic discoveries for the implementation of personalized precision medicine). We analyzed the autophagy marker proteins p62 and LC3 in paired tumor and adjacent cirrhotic non-tumor tissues of human HCC. We show strong variability in p62 and LC3-II levels between tumor parts of different HCC patients and between tumor and non-tumor HCC in the same patient, suggesting heterogeneity in autophagy flux. This diversity in flux led us to consider a non-personalized method of autophagy targeting, combining simultaneous activation and blockade of autophagy, which could, in theory, benefit a substantial number of HCC patients, irrespective of tumor autophagic flux. We show that the combination of sodium butyrate (NaB, autophagy inducer) and chloroquine (CQ, autophagy blocker) has a marked and synergistic cytotoxic effect in vitro on all human liver cancer cell lines studied, compared with the cellular effect of each product separately, and with no deleterious effect on normal hepatocytes in culture. Cancer cell death was associated with accumulation of autophagosomes, induction of lysosome membrane permeabilization and increased oxidative stress. Our results suggest that simultaneous activation and blockade of autophagy may be a valuable approach against HCC, and that microbiota-derived products improve the sensitivity of HCC cells to antitumor agents. Abbreviations AV: annexin V; CI: combination index; CTSB: Cathepsin B; CTSD: Cathepsin D; CTSF: Cathepsin F; CQ: chloroquine; DEN: N-diethylnitrosamine; DMEM: Dulbecco's modified eagle medium; FBS: fetal bovine serum; FSC: forward scatter; GNS: N-acetylglucosamine-6-sulfatase; HCC: hepatocellular carcinoma; HDACi: histone deacetylase inhibitor; HCQ: hydroxychloroquine; LMP: lysosomal membrane permeabilization; LAMP1: lysosome-associated membrane protein; LIPA: Lysosomal acid lipase; LSR: Lysosomal staining cells; MAP1LC3A: microtubule associated protein 1 light chain 3 alpha; NaB: sodium butyrate; NASH: non-alcoholic steatohepatitis; NRF2: nuclear factor erythroid 2-related factor 2; PI: propidium iodide; PMSF: phenylmethanesulfonyl fluoride; ROS: reactive oxygen species; SCARB2: Scavenger receptor class B member 2; SQSTM1/p62: sequestosome 1; SMPD1: Sphingomyelin phosphodiesterase 1; SSC: side scatter; TFEB: transcription factor EB.

LncRNA-NEAT1 facilitates autophagy to boost pemetrexed resistance in lung adenocarcinoma via the mir-379-3p/HIF1A pathway

BACKGROUND

As a primary chemotherapeutic agent for lung adenocarcinoma (LUAD), pemetrexed (PEM) faces the challenge of resistance development in cancer cells due to its chronic use, which compromises its therapeutic benefits. LncRNA-NEAT1, implicated in the promotion of cancer, is a key player in LUAD. The objective of this study is to explore the contribution of lncRNA-NEAT1 to PEM resistance in LUAD and to dissect the molecular mechanisms involved.

METHOD

The expression levels of lncRNA-NEAT1 in LUAD tissues and cells were deciphered using the TCGA database and qRT-PCR. To delve into the functional implications of lncRNA-NEAT1, we engineered plasmids to modulate its expression levels in PEM-resistant A549 cells. PEM resistance in the modified cells was then quantitatively assessed via a panel of assays including cell counting kit-8 (CCK-8), and colony formation, and flow cytometry. To predict the interaction sites between lncRNA-NEAT1 and miR-379-3p, along with the miR-379-3p and hypoxia-inducible factor (HIF1A), we referred to the StarBase and TargetScan databases. The interplay between these RNA molecules was further characterized by RNA immunoprecipitation (RIP) and dual-luciferase reporter assays, while the expression of autophagy-related proteins LC3I, LC3II, and Beclin1 was profiled using western blot (WB).

RESULTS

Abundant lncRNA-NEAT1 expression was observed in LUAD tissues and cell lines. Its depletion resulted in impeded growth of A549/PEM cells, enhanced apoptotic rates, and a lowered threshold for PEM to exert a half-maximal inhibitory effect. The interplay between lncRNA-NEAT1 and miR-379-3p, as evidenced by dual-luciferase reporter assays, RIP, and qRT-PCR, led to the upregulation of HIF1A. WB and CCK-8 outcomes illustrated that the autophagy and PEM resistance were compromised when HIF1A expression was curtailed by miR-379-3p mimics in A549/PEM cells. The restoration of these effects was observed upon lncRNA-NEAT1-mediated downregulation of miR-379-3p.

CONCLUSION

Our study illuminates the role of lncRNA-NEAT1 in LUAD, where it mediates resistance to PEM through the activation of autophagy via the miR-379-3p/HIF1A axis. This work paves the way for new therapeutic strategies for managing PEM resistance in LUAD patients.

Unraveling the Janus-Faced Role of Autophagy in Hepatocellular Carcinoma: Implications for Therapeutic Interventions

This review aims to provide a comprehensive understanding of the molecular mechanisms underlying autophagy and mitophagy in hepatocellular carcinoma (HCC). Autophagy is an essential cellular process in maintaining cell homeostasis. Still, its dysregulation is associated with the development of liver diseases, including HCC, which is one of leading causes of cancer-related death worldwide. We focus on elucidating the dual role of autophagy in HCC, both in tumor initiation and progression, and highlighting the complex nature involved in the disease. In addition, we present a detailed analysis of a small subset of autophagy- and mitophagy-related molecules, revealing their specific functions during tumorigenesis and the progression of HCC cells. By understanding these mechanisms, we aim to provide valuable insights into potential therapeutic strategies to manipulate autophagy effectively. The goal is to improve the therapeutic response of liver cancer cells and overcome drug resistance, providing new avenues for improved treatment options for HCC patients. Overall, this review serves as a valuable resource for researchers and clinicians interested in the complex role of autophagy in HCC and its potential as a target for innovative therapies aimed to combat this devastating disease.

Combating drug resistance in hepatocellular carcinoma: No awareness today, no action tomorrow

Hepatocellular carcinoma (HCC), the sixth most common cancer worldwide, is associated with a high degree of malignancy and poor prognosis. Patients with early HCC may benefit from surgical resection to remove tumor tissue and a margin of healthy tissue surrounding it. Unfortunately, most patients with HCC are diagnosed at an advanced or distant stage, at which point resection is not feasible. Systemic therapy is now routinely prescribed to patients with advanced HCC; however, drug resistance has become a major obstacle to the treatment of HCC and exploring purported mechanisms promoting drug resistance remains a challenge. Here, we focus on the determinants of drug resistance from the perspective of non-coding RNAs (ncRNAs), liver cancer stem cells (LCSCs), autophagy, epithelial-mesenchymal transition (EMT), exosomes, ferroptosis, and the tumor microenvironment (TME), with the aim to provide new insights into HCC treatment.

Preparation of a modified silk-based gel/microsphere composite as a potential hepatic arterial embolization agent

Transcatheter arterial chemoembolization (TACE) is an effective method for treating hepatocellular carcinoma (HCC). In this study, chitosan (CS), sodium glycerophosphate (GP), and sodium alginate (SA) were used as the main raw materials to develop clinically non-degradable embolization microspheres (Ms). Chitosan/sodium alginate embolization Ms. were generated using an emulsification cross-linking method. The Ms. were then uniformly dispersed in CS/GP temperature-sensitive gels to produce Gel/Ms. composite embolic agents. The results showed that Gel/Ms. had good morphology and a neatly arranged three-dimensional structure, and the Ms. dispersed in the Gel as evidenced by SEM. Furthermore, Gel/Ms. has good blood compatibility, with a hemolysis rate of ≤5 %. The cytotoxicity experiments have also proven its excellent cell compatibility. The degradation rate of Gel/Ms. was 58.869 ± 1.754 % within 4 weeks, indicating that Gel/Ms. had good degradation performance matching its drug release purpose. The Gel/Ms. adheres better at the target site than Ms. alone and releases the drug steadily over a long period, and the maximum release rate of Gel/Ms. within 8 h was 38.33 ± 1.528 %, and within 168 h was 81.266 ± 1.193 %. Overall, Gel/Ms. demonstrate better slow drug release, reduced sudden drug release, prolonged drug action time at the target site, and reduced toxic side effects on the body compared to Gel alone.

Targeting and regulation of autophagy in hepatocellular carcinoma: revisiting the molecular interactions and mechanisms for new therapy approaches

Autophagy is an evolutionarily conserved process that plays a role in regulating homeostasis under physiological conditions. However, dysregulation of autophagy is observed in the development of human diseases, especially cancer. Autophagy has reciprocal functions in cancer and may be responsible for either survival or death. Hepatocellular carcinoma (HCC) is one of the most lethal and common malignancies of the liver, and smoking, infection, and alcohol consumption can lead to its development. Genetic mutations and alterations in molecular processes can exacerbate the progression of HCC. The function of autophagy in HCC is controversial and may be both tumor suppressive and tumor promoting. Activation of autophagy may affect apoptosis in HCC and is a regulator of proliferation and glucose metabolism. Induction of autophagy may promote tumor metastasis via induction of EMT. In addition, autophagy is a regulator of stem cell formation in HCC, and pro-survival autophagy leads to cancer cell resistance to chemotherapy and radiotherapy. Targeting autophagy impairs growth and metastasis in HCC and improves tumor cell response to therapy. Of note, a large number of signaling pathways such as STAT3, Wnt, miRNAs, lncRNAs, and circRNAs regulate autophagy in HCC. Moreover, regulation of autophagy (induction or inhibition) by antitumor agents could be suggested for effective treatment of HCC. In this paper, we comprehensively review the role and mechanisms of autophagy in HCC and discuss the potential benefit of targeting this process in the treatment of the cancer. Video Abstract.

Cathelicidin LL-37 Activates Human Keratinocyte Autophagy through the P2X₇, Mechanistic Target of Rapamycin, and MAPK Pathways

Human cathelicidin LL-37 is a multifunctional antimicrobial peptide that exhibits antimicrobial and immunomodulatory activities. LL-37 regulates skin barrier function and was recently reported to activate autophagy in macrophages. Because autophagy deficiency is associated with skin diseases characterized by a dysfunctional epidermal barrier, we hypothesized that LL-37 might regulate the skin barrier through autophagy modulation. We showed that LL-37 activated autophagy in human keratinocytes and three-dimensional skin equivalent models as indicated by increases in LC3 puncta formation, decreases in p62, and autophagosome and autolysosome formation. LL-37‒induced autophagy was suppressed by P2X₇ receptor, adenosine monophosphate‒activated protein kinase, and unc-51-like kinase 1 inhibitors, suggesting that the P2X₇, adenosine monophosphate‒activated protein kinase, and unc-51-like kinase 1 pathways are involved. Moreover, LL-37 enhanced the phosphorylation of adenosine monophosphate‒activated protein kinase and unc-51-like kinase 1. In addition, LL-37‒mediated autophagy involves the mechanistic target of rapamycin and MAPK pathways. Interestingly, the LL-37‒induced distribution of tight junction proteins and improvement in the tight junction barrier were inhibited in autophagy-deficient keratinocytes and keratinocytes and skin models treated with autophagy inhibitors, indicating that the LL-37‒mediated tight junction barrier is associated with autophagy activation. Collectively, these findings suggest that LL-37 is a potential therapeutic target for skin diseases characterized by dysfunctional autophagy and skin barriers.

Autophagy: A Key Player in Pancreatic Cancer Progression and a Potential Drug Target

Pancreatic cancer is known to have the lowest survival outcomes among all major cancers, and unfortunately, this has only been marginally improved over last four decades. The innate characteristics of pancreatic cancer include an aggressive and fast-growing nature from powerful driver mutations, a highly defensive tumor microenvironment and the upregulation of advantageous survival pathways such as autophagy. Autophagy involves targeted degradation of proteins and organelles to provide a secondary source of cellular supplies to maintain cell growth. Elevated autophagic activity in pancreatic cancer is recognized as a major survival pathway as it provides a plethora of support for tumors by supplying vital resources, maintaining tumour survival under the stressful microenvironment and promoting other pathways involved in tumour progression and metastasis. The combination of these features is unique to pancreatic cancer and present significant resistance to chemotherapeutic strategies, thus, indicating a need for further investigation into therapies targeting this crucial pathway. This review will outline the autophagy pathway and its regulation, in addition to the genetic landscape and tumor microenvironment that contribute to pancreatic cancer severity. Moreover, this review will also discuss the mechanisms of novel therapeutic strategies that inhibit autophagy and how they could be used to suppress tumor progression.

Regulation of autophagy by controlling Erk1/2 and mTOR for platelet-derived growth factor-BB-mediated vascular smooth muscle cell phenotype shift

AIMS

Vascular smooth muscle cell (VSMC) phenotype shift is involved in the pathophysiology of vascular injury or platelet-derived growth factor (PDGF)-induced abnormal proliferation and migration of VSMCs. We aimed to investigate the underlying mechanism involved in PDGF-mediated signaling pathways and autophagy regulation followed by VSMC phenotype shift.

MAIN METHODS

The proliferation, migration and apoptosis of cultured rat aortic VSMCs were measured, and cells undergoing phenotype shift and autophagy were examined. Specific inhibitors for target proteins in signaling pathways were applied to clarify their roles in regulating cell functions.

KEY FINDINGS

PDGF-BB stimulation initiated autophagy activation and synthetic phenotype transition by decreasing α-smooth muscle-actin (SMA), calponin and myosin heavy chain (MHC) and increasing osteopontin (OPN) expression. However, U0126, a potent extracellular signal-regulated kinase 1/2 (Erk1/2) inhibitor, decreased PDGF-BB-induced LC3 expression, while rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), increased it. Furthermore, U0126 decreased the expresseion of autophagy-related genes (Atgs) such as beclin-1, Atg7, Atg5, and Atg12-Atg5 complex, indicating that Erk1/2 is a regulator of PDGF-BB-induced VSMC autophagy. Regardless of autophagy inhibition by U0126 or activation by rapamycin, the PDGF-BB-induced decrease in SMA, calponin and MHC and increase in OPN expression were inhibited. Furthermore, PDGF-BB-stimulated VSMC proliferation, migration and proliferating cell nuclear antigen (PCNA) expression were inhibited by U0126 and rapamycin.

SIGNIFICANCE

These findings suggest that PDGF-BB-induced autophagy is strongly regulated by Erk1/2, an mTOR-independent pathway, and any approach for targeting autophagy modulation is a potential therapeutic strategy for addressing abnormal VSMC proliferation and migration.

Molecular imaging of the kinetics of hyperactivated ERK1/2-mediated autophagy during acquirement of chemoresistance

Alterations in key kinases and signaling pathways can fine-tune autophagic flux to promote the development of chemoresistance. Despite empirical evidences of strong association between enhanced autophagic flux with acquired chemoresistance, it is still not understood whether an ongoing autophagic flux is required for both initiation, as well as maintenance of chemoresistance, or is sufficient for one of the either steps. Utilizing indigenously developed cisplatin-paclitaxel-resistant models of ovarian cancer cells, we report an intriguing oscillation in chemotherapy-induced autophagic flux across stages of resistance, which was found to be specifically elevated at the early stages or onset of chemoresistance. Conversely, the sensitive cells and cells at late stages of resistance showed stalled and reduced autophagic flux. This increased flux at early stages of resistance was found to be dictated by a hyperactive ERK1/2 signaling, which when inhibited either pharmacologically (U0126/Trametinib) or genetically, reduced p62 degradation, number of LC3+veLAMP1+ve puncta, autophagolysosome formation, and led to chemo-sensitization and apoptosis. Inhibition of ERK1/2 activation also altered the level of UVRAG and Rab7, the two key proteins involved in autophagosome-lysosome fusion. Noninvasive imaging of autophagic flux using a novel autophagy sensor (mtFL-p62 fusion reporter) showed that combinatorial treatment of platinum-taxol along with Trametinib/chloroquine blocked autophagic flux in live cells and tumor xenografts. Interestingly, Trametinib was found to be equally effective in blocking autophagic flux as chloroquine both in live cells and tumor xenografts. Combinatorial treatment of Trametinib and platinum-taxol significantly reduced tumor growth. This is probably the first report of real-time monitoring of chemotherapy-induced autophagy kinetics through noninvasive bioluminescence imaging in preclinical mouse model. Altogether our data suggest that an activated ERK1/2 supports proper completion of autophagic flux at the onset of chemoresistance to endure initial chemotherapeutic insult and foster the development of a highly chemoresistant phenotype, where autophagy becomes dispensable.

PLCγ1 inhibition-driven autophagy of IL-1β-treated chondrocyte confers cartilage protection against osteoarthritis, involving AMPK, Erk and Akt

Previous studies identified the involvement of phosphoinositide‐specific phospholipase C (PLC) γ1 in some events of chondrocytes. This study aims to investigate whether and how PLCγ1 modulates autophagy to execute its role in osteoarthritis (OA) progression. Rat normal or human OA chondrocytes were pretreated with IL‐1β for mimicking or sustaining OA pathological condition. Using Western blotting, immunoprecipitation, qPCR, immunofluorescence and Dimethylmethylene blue assays, and ELISA and transmission electron microscope techniques, we found that PLCγ1 inhibitor U73122 enhanced Collagen II, Aggrecan and GAG levels, accompanied with increased LC3B‐II/I ratio and decreased P62 expression level, whereas autophagy inhibitor Chloroquine partially diminished its effect. Meanwhile, U73122 dissociated Beclin1 from Beclin1‐IP3R‐Bcl‐2 complex and blocked mTOR/ULK1 axis, in which the crosstalk between PLCγ1, AMPK, Erk and Akt were involved. Additionally, by haematoxylin and eosin, Safranin O/Fast green, and immunohistochemistry staining, we observed that intra‐articular injection of Ad‐shPLCγ1‐1/2 significantly enhanced Collagen and Aggrecan levels, accompanied with increased LC3B and decreased P62 levels in a rat OA model induced by anterior cruciate ligament transection and medial meniscus resection. Consequently, PLCγ1 inhibition‐driven autophagy conferred cartilage protection against OA through promoting ECM synthesis in OA chondrocytes in vivo and in vitro, involving the crosstalk between PLCγ1, AMPK, Erk and Akt.

Tubeimoside I Inhibits Cell Proliferation and Induces a Partly Disrupted and Cytoprotective Autophagy Through Rapidly Hyperactivation of MEK1/2-ERK1/2 Cascade via Promoting PTP1B in Melanoma

Tubeimoside I (TBMS1), also referred to as tubeimoside A, is a natural compound extracted from the plant Tu Bei Mu (Bolbostemma paniculatum), which is a traditional Chinese herb used to treat multiple diseases for more than 1,000 years. Studies in recent years reported its anti-tumor activity in several cancers. However, whether it is effective in melanoma remains unknown. In the current study, we discovered that TBMS1 treatment inhibited melanoma cell proliferation in vitro and tumorigenecity in vivo. Besides, we also observed that TBMS1 treatment induced a partly disrupted autophagy, which still remained a protective role, disruption of which by chloroquine (CQ) or 3-methyladenine (3-MA) enhanced TBMS1-induced cell proliferation inhibition. CQ combined with TBMS1 even induced cellular apoptosis. BRAF(V600E) mutation and its continuously activated downstream MEK1/2-ERK1/2 cascade are found in 50% of melanomas and are important for malanomagenesis. However, hyperactivating MEK1/2-ERK1/2 cascade can also inhibit tumor growth. Intriguingly, we observed that TBMS1 rapidly hyperactivated MEK1/2-ERK1/2, inhibition of which by its inhibitor SL-327 rescued the anti-cancerous effects of TBMS1. Besides, the targets of TBMS1 were predicted by the ZINC Database based on its structure. It is revealed that protein-tyrosine phosphatase 1B (PTP1B) might be one of the targets of TBMS1. Inhibition of PTP1B by its selective inhibitor TCS401 or shRNA rescued the anti-cancerous effects of TBMS1 in melanoma cells. These results indicated that TBMS1 might activate PTP1B, which further hyperactivates MEK1/2-ERK1/2 cascade, thereby inhibiting cell proliferation in melanoma. Our results provided the potentiality of TBMS1 as a drug candidate for melanoma therapy and confirmed that rapidly hyperactivating an oncogenic signaling pathway may also be a promising strategy for cancer treatment.

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.

Levamisole enhances DR4-independent apoptosis induced by TRAIL through inhibiting the activation of JNK in lung cancer

THE HEADINGS AIMS

Levamisole has anti-parasite and antitumor activities, but the anti-lung cancer mechanism has not been studied. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is regarded as a promising drug because of the ability to selectively target cancer cells. However, the tolerance of cancer cells to TRAIL limits its antitumor activity. Other drugs combined with TRAIL need to be explored to enhance its antitumor activity. Based on the adjuvant anticancer effect of levamisole on anticancer drugs activity, the antitumor activity of levamisole combined with TRAIL will be investigated.

MATERIALS AND METHODS

In vitro and in vivo experiments were employed to investigate the anti-tumor activity. Flow-cytometry analysis, western blotting and siRNA transfection were used to explore the molecular mechanism.

KEY FINDINGS

Levamisole decreased the proliferation of lung cancer cells in vitro and in vivo and induced cell cycle arrest in G0/G1 phase. Besides, levamisole also enhanced TRAIL-induced DR4-independent apoptosis by inhibiting the phosphorylation of cJUN. A new cellular protective pathway LC3B-DR4/Erk was also disclosed, in which levamisole only increased the expression of LC3B and then activated the phosphorylation of Erk and increased the expression of DR4, while p-Erk and DR4 inter-regulated.

SIGNIFICANCE

Levamisole may be used as an adjuvant of TRAIL in treating lung cancer. The discovery of LC3B-DR4/Erk as a new protective pathway provides a new direction for sensitizing lung cancer cells to TRAIL.

Roles of Macrophage Migration Inhibitory Factor in Dengue Pathogenesis: From Pathogenic Factor to Therapeutic Target

Dengue virus (DENV) infection is the most prevalent mosquito-borne viral infection and can lead to severe dengue hemorrhagic fever (DHF) and even life-threatening dengue shock syndrome (DSS). Although the cytokine storm has been revealed as a critical factor in dengue disease, the limited understanding of dengue immunopathogenesis hinders the development of effective treatments. Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine that mediates diverse immune responses, and the serum level of MIF positively correlates with disease severity in patients with dengue. MIF is involved in DENV replication and many pathological changes, such as vascular leakage, during DENV infection. In this paper, the pathogenic roles of MIF and the regulation of MIF secretion during DENV infection are reviewed. Furthermore, whether MIF is a potential therapeutic target against DENV infection is also discussed.

Modulation of the Autophagy-lysosomal Pathway in Hepatocellular Carcinoma Using Small Molecules

Hepatocellular carcinoma (HCC) accounts for approximately 90% of all cases of primary liver cancer; it is the third most frequent cause of cancer-related death worldwide. In early-stage disease, surgical resection and liver transplantation are considered curative treatments. However, the majority of HCC patients present with advanced-stage disease that is treated using palliative systemic therapy. Since HCC is heterogeneous owing to its multiple etiologies, various risk factors, and inherent resistance to chemotherapy, the development of an effective systemic treatment strategy for HCC remains a considerable challenge. Autophagy is a lysosome-dependent catabolic degradation pathway that is essential for maintaining cellular energy homeostasis. Autophagy dysfunction is closely linked with the pathogenesis of various cancers; therefore, the discovery of small molecules that can modulate autophagy has attracted considerable interest in the development of a systemic treatment strategy for advanced HCC. Here, we reviewed the roles of autophagy in HCC and the recent advances regarding small molecules that target autophagy regulatory mechanisms.

Autophagy-based unconventional secretion of HMGB1 by keratinocytes plays a pivotal role in psoriatic skin inflammation

The precise mechanism through which macroautophagy/autophagy affects psoriasis is poorly understood. Here, we found that keratinocyte (KC) autophagy, which was positively correlated with psoriatic severity in patients and mouse models and could be inhibited by mitogen-activated protein kinase (MAPK) family inactivation. The impairment of autophagic flux alleviated psoriasisform inflammation. We also found that an autophagy-based unconventional secretory pathway (autosecretion) dependent on ATG5 (autophagy related 5) and GORASP2 (golgi reassembly stacking protein 2) promoted psoriasiform KC inflammation. Moreover, the alarmin HMGB1 (high mobility group box 1) was more effective than other autosecretory proteins in regulating psoriasiform cutaneous inflammation. HMGB1 neutralization in autophagy-efficient KCs eliminated the differences in psoriasiform inflammation between Krt14^+/+-Atg5^f/f KCs and Krt14^Cre/+-atg5^f/f KCs, and conversely, recombinant HMGB1 almost completely restored psoriasiform inflammation in Krt14^Cre/+-atg5^f/f KCs in vivo. These results suggest that HMGB1-associated autosecretion plays a pivotal role in cutaneous inflammation. Finally, we demonstrated that Krt14^Cre/+-hmgb1^f/f mice displayed attenuated psoriatic inflammation due to the essential crosstalk between KC-specific HMGB1-associated autosecretion and γδT cells. Thus, this study uncovered a novel autophagy mechanism in psoriasis pathogenesis, and the findings imply the clinical significance of investigating and treating psoriasis.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; AGER: advanced glycosylation end-product specific receptor; Anti-HMGB1: anti-HMGB1 neutralizing antibody; Anti-IL18: anti-IL18 neutralizing antibody; Anti-IL1B: anti-IL1B neutralizing antibody; ATG5: autophagy related 5; BAF: bafilomycin A₁; BECN1: beclin 1; CASP1: caspase 1; CCL: C-C motif chemokine ligand; CsA: cyclosporine A; ctrl shRNA: lentivirus harboring shRNA against control; CXCL: C-X-C motif chemokine ligand; DCs: dendritic cells; DMEM: dulbecco's modified Eagle's medium; ELISA: enzyme-linked immunosorbent assay; EM: electron microscopy; FBS: fetal bovine serum; GORASP2 shRNA: lentivirus harboring shRNA against GORASP2; GORASP2/GRASP55: golgi reassembly stacking protein 2; GR1: a composite epitope between LY6 (lymphocyte antigen 6 complex) locus C1 and LY6 locus G6D antigens; H&E: hematoxylin and eosin; HMGB1: high mobility group box 1; HMGB1 shRNA: lentivirus harboring shRNA against HMGB1; IFNG/IFN-γ: interferon gamma; IL17A: interleukin 17A; IL18: interleukin 18; IL1A/IL-1α: interleukin 1 alpha; IL1B/IL-1β: interleukin 1 beta; IL22/IL-22: interleukin 22; IL23A: interleukin 23 subunit alpha; IL23R: interleukin 23 receptor; IMQ: imiquimod; ITGAM/CD11B: integrin subunit alpha M; ITGAX/CD11C: integrin subunit alpha X; IVL: involucrin; KC: keratinocyte; KD: knockdown; KO: knockout; Krt14^+/+-Atg5^f/f mice: mice bearing an Atg5 flox allele, in which exon 3 of the Atg5 gene is flanked by two loxP sites; Krt14^+/+-Hmgb1^f/f: mice bearing an Hmgb1 flox allele, in which exon 2 to 4 of the Hmgb1 gene is flanked by two loxP sites; Krt14^Cre/+-atg5^f/f mice: keratinocyte-specific atg5 knockout mice generated by mating Atg5-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt4; Krt14^Cre/+-hmgb1^f/f mice: keratinocyte-specific hmgb1 knockout mice generated by mating Hmgb1-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt14; Krt14-Vegfa mice: mice expressing 164-amino acid Vegfa splice variant recombinase under the control of promoter of Krt14; LAMP1: lysosomal associated membrane protein 1; LDH: lactate dehydrogenase; LORICRIN: loricrin cornified envelope precursor protein; M5: TNF, IL1A, IL17A, IL22 and OSM in combination; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MKI67: marker of proliferation Ki-67; MTT: thiazolyl blue tetrazolium bromide; NFKB/NF-κB: nuclear factor kappa B; NHEKs: primary normal human epidermal keratinocytes; NS: not significant; OSM: oncostatin M; PASI: psoriasis area and severity index; PtdIns3K: class III phosphatidylinositol 3-kinase; qRT-PCR: quantitative RT-PCR; RELA/p65: RELA proto-oncogene, NF-kB subunit; rHMGB1: recombinant HMGB1; rIL18: recombinant interleukin 18; rIL1B: recombinant interleukin 1 beta; S100A: S100 calcium binding protein A; SQSTM1/p62: sequestosome 1; T17: IL17A-producing T; TCR: T-cell receptor; tcrd KO mice: tcrd (T cell receptor delta chain) knockout mice, which show deficient receptor expression in all adult lymphoid and epithelial organs; TLR: toll-like receptor; TNF/TNF-α: tumor necrosis factor; WOR: wortmannin; WT: wild-type; γδT17 cells: IL17A-producing γδ T cells.

Melatonin Protects Intervertebral Disc from Degeneration by Improving Cell Survival and Function via Activation of the ERK1/2 Signaling Pathway

Melatonin, a neuroendocrine hormone secreted by the pineal body, has a positive effect on intervertebral disc degeneration. The present study is aimed at investigating the biological role of melatonin in intervertebral disc degeneration and its underlying mechanism. A human nucleus pulposus cell (NPC) line was exposed to melatonin at different concentrations. Cell proliferation was measured by CCK-8 assay. Cell cycle and apoptosis were analyzed by flow cytometry. Western blot was performed to measure the protein expression of indicated genes. A rabbit model of intervertebral disc degeneration was established to detect the role and mechanism of melatonin on intervertebral disc degeneration. Our study showed that melatonin promoted NPC viability and inhibited cell arrest. Furthermore, melatonin treatment led to the upregulation of collagen II and aggrecan and downregulation of collagen X. Moreover, melatonin significantly elevated the activity of the ERK signaling pathway. Inhibition of the ERK1/2 signals reversed the role of melatonin in the regulation of NPCs both in vitro and in vivo. Melatonin increased NPC viability through inhibition of cell cycle arrest and apoptosis. Moreover, melatonin promoted the secretion of functional factors influencing the nucleus pulposus cell physiology and retarded cell degeneration. Our results suggest that melatonin activated the ERK1/2 signaling pathway, thereby affecting the biological properties of the intervertebral disc degeneration.

The role of ERK-RSK signaling in the proliferation of intrahepatic biliary epithelial cells exposed to microcystin-leucine arginine

Microcystin-leucine arginine (MC-LR) is a potent specific hepatotoxin produced by cyanobacteria in diverse water systems, and it has been documented to induce liver injury and hepatocarcinogenesis. However, its toxic effects on intrahepatic biliary epithelial cells have not been invested in detail. In this study, we aimed to investigate the effects of MC-LR exposure on the intrahepatic biliary epithelial cells in the liver. MC-LR was orally administered to mice at 1 μg/L, 7.5 μg/L, 15 μg/L, or 30 μg/L for 180 consecutive days for histopathological and immunoblot analysis. We observed that MC-LR can enter intrahepatic bile duct tissue and induce hyperplasia of mice. Human primary intrahepatic biliary epithelial cells (HiBECs) were cultured with various concentrations of MC-LR for 24 h, meanwhile the cell viability and proteins level were detected. Western blotting analysis revealed that MC-LR increased RSK phosphorylation via ERK signaling. RSK participated in cell proliferation and cell cycle progression. Taken together, after chronic exposure, MC-LR-treated mice exhibited abnormal bile duct hyperplasia and thickened bile duct morphology through activating the ERK-RSK signaling. These data support the potential toxic effects of MC-LR on bile duct tissue of the liver.

Bone marrow mesenchymal stem cells repair Cr (VI)- injured kidney by regulating mitochondria-mediated apoptosis and mitophagy mediated via the MAPK signaling pathway

The present study aimed to explore the repair effect and mechanism of bone marrow mesenchymal stem cells (BMSCs) transplantation on injured kidneys caused by hexavalent chromium (Cr (VI)). Wistar rats were intraperitoneally injected with 0.4 mg/kg•bw Cr (VI) ion solution. After 30 days, 1 × 10⁷ BMSCs were transplanted into rats. After cell transplantation for 2 weeks, there was no significant difference in the chromium content between the model and BMSCs-therapy group by atomic absorption spectrometry. In BMSCs-therapy group, the renal organ index, the serum levels of blood urea nitrogen (BUN) and creatinine (CRE), malonaldehyde (MDA) content were significantly decreased, superoxide dismutase (SOD) activity was significantly elevated, and the pathological changes were improved compared with the model group. The results of immunohistochemical and western blot assays showed that the expressions of apoptosis-related proteins Bax, Cytochrome c, and Caspase-3, as well as autophagy-associated proteins Beclin 1, PINK1, Parkin, p-Parkin, LC3B, and the MAPK signaling pathway, including the ratio of p-p38 to p38 and p-JNK to JNK were all significantly decreased, Bcl-2 and p62 expressions, and the ratio of p-ERK to ERK were significantly elevated in BMSCs-therapy group compared with the model group. These results suggested that BMSCs repaired Cr (VI)-injured kidney through decreasing mitochondria-mediated apoptosis and mitophagy mediated by downregulating phosphorylation of p38 and JNK, upregulating phosphorylation of ERK.

Chondroprotection of PPARα activation by WY14643 via autophagy involving Akt and ERK in LPS-treated mouse chondrocytes and osteoarthritis model

Autophagy maintains cellular homoeostasis. The enhancement of autophagy in chondrocytes could prevent osteoarthritis (OA) progression in articular cartilage. Peroxisome proliferator-activated receptor α (PPARα) activation may also protect articular chondrocytes against cartilage degradation in OA. However, whether the protective effect of activated PPARα is associated with autophagy induction in chondrocytes is not determined. In this study, we investigated the effect of PPARα activation by its agonist, WY14643, on the protein expression level of Aggrecan and ADAMTS5, and the protein expression level of autophagy biomarkers, including LC3B and P62, using Western blotting analysis in isolated mouse chondrocytes pre-treated with lipopolysaccharides (LPS, mimicking OA chondrocytes) with or without the autophagy inhibitor chloroquine diphosphate salt. Furthermore, Akt and ERK phosphorylation was detected in LPS-treated chondrocytes in response to WY14643. In addition, the effect of intra-articularly injected WY14643 on articular cartilage in a mouse OA model established by the destabilization of the medial meniscus was assessed using the Osteoarthritis Research Society International (OARSI) histopathology assessment system, along with the detection of Aggrecan, ADAMTS5, LC3B and P62 protein levels using immunohistochemistry assay. The results indicated that PPARα activation by WY14643 promoted proteoglycan synthesis by autophagy enhancement in OA chondrocytes in vivo and in vitro concomitant with the elevation of Akt and ERK phosphorylation. Therefore, autophagy could contribute to the chondroprotection of PPARα activation by WY14643, with the implication that PPARα activation by WY14643 may be a potential approach for OA therapy.

Autophagy: Dual Response in the Development of Hepatocellular Carcinoma

Autophagy is an evolutionary conserved intracellular mechanism which helps eukaryotic cells in maintaining their metabolic state to afford high-efficiency energy requirements. In the physiology of a normal liver and the pathogenesis of liver diseases, autophagy plays a crucial role. Autophagy has been found to be both upregulated and downregulated in different cancers providing the evidence that autophagy plays a dual role in suppressing and promoting cell survival. Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the major leading cause of cancer mortality worldwide. In light of its high complexity and poor prognosis, it is essential to improve our understanding of autophagy’s role in HCC. In this review, we summarize the dual mechanism of autophagy in the development of HCC and elucidate the currently used therapeutic strategies for anti-HCC therapy.

Intracellular Iron Chelation by a Novel Compound, C7, Reactivates Epstein⁻Barr Virus (EBV) Lytic Cycle via the ERK-Autophagy Axis in EBV-Positive Epithelial Cancers

Pharmaceutical reactivation of lytic cycle of Epstein–Barr virus (EBV) represents a potential therapeutic strategy against EBV-associated epithelial malignancies, e.g., gastric carcinoma (GC) and nasopharyngeal carcinoma (NPC). A novel lytic-inducing compound, C7, which exhibits structural similarity to Di-2-Pyridyl Ketone 4, 4-Dimethyl-3-Thiosemicarbazone (Dp44mT), a known chelator of intracellular iron, is found to reactivate EBV lytic cycle in GC and NPC. This study aims to investigate the role of intracellular iron chelation by C7 and other iron chelators in lytic reactivation of EBV in GC and NPC. Testing of six structural analogs of C7 revealed only those which have high affinity towards transition metals could induce EBV lytic cycle. Precomplexing C7 and iron chelators to iron prior to treatment of the cells abolished EBV lytic reactivation. Though hypoxia signaling pathway was activated, it was not the only pathway associated with EBV reactivation. Specifically, C7 and iron chelators initiated autophagy by activating extracellular signal-regulated kinase (ERK1/2) to reactivate EBV lytic cycle since autophagy and EBV lytic reactivation were abolished in cells treated with ERK1/2 blockers whilst inhibition of autophagy by 3-Methyladenine (3-MA) and atg5 knockdown significantly abolished EBV lytic reactivation. In summary, we discovered a novel mechanism of reactivation of the EBV lytic cycle through intracellular iron chelation and induction of ERK-autophagy axis in EBV-positive epithelial malignancies, raising the question whether clinically available iron chelators can be incorporated into existing therapeutic regimens to treat these cancers.

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.

The multifaceted role of autophagy in cancer and the microenvironment

Autophagy is a crucial recycling process that is increasingly being recognized as an important factor in cancer initiation, cancer (stem) cell maintenance as well as the development of resistance to cancer therapy in both solid and hematological malignancies. Furthermore, it is being recognized that autophagy also plays a crucial and sometimes opposing role in the complex cancer microenvironment. For instance, autophagy in stromal cells such as fibroblasts contributes to tumorigenesis by generating and supplying nutrients to cancerous cells. Reversely, autophagy in immune cells appears to contribute to tumor‐localized immune responses and among others regulates antigen presentation to and by immune cells. Autophagy also directly regulates T and natural killer cell activity and is required for mounting T‐cell memory responses. Thus, within the tumor microenvironment autophagy has a multifaceted role that, depending on the context, may help drive tumorigenesis or may help to support anticancer immune responses. This multifaceted role should be taken into account when designing autophagy‐based cancer therapeutics. In this review, we provide an overview of the diverse facets of autophagy in cancer cells and nonmalignant cells in the cancer microenvironment. Second, we will attempt to integrate and provide a unified view of how these various aspects can be therapeutically exploited for cancer therapy.

Identification of DNA-PKcs as a primary resistance factor of TIC10 in hepatocellular carcinoma cells

The current study tested the anti-hepatocellular carcinoma (HCC) cell activity of TIC10, a first-in-class small-molecule tumor necrosis (TNF)-related apoptosis-inducing ligand (TRAIL) inducer. TIC10 exerted potent anti-proliferative and pro-apoptotic actions in primary and established human HCC cells. TIC10 blocked Akt-Erk activation, leading to Foxo3a nuclear translocation, as well as TRAIL and death receptor-5 (DR5) transcription in HCC cells. We propose that DNA-PKcs is a major resistance factor of TIC10 possibly via inhibiting Foxo3a nuclear translocation. DNA-PKcs inhibition, knockdown or mutation facilitated TIC10-induced Foxo3a nuclear translocation, TRAIL/DR5 expression and cell apoptosis. Reversely, exogenous DNA-PKcs over-expression inhibited above actions by TIC10. In vivo, oral administration of TIC10 significantly inhibited HepG2 tumor growth in nude mice, which was further potentiated with Nu7026 co-administration. Thus, TIC10 shows promising anti-HCC activity, alone or together with DNA-PKcs inhibitors.

Chloroquine upregulates TRAIL/TRAILR2 expression and potentiates doxorubicin anti-tumor activity in thioacetamide-induced hepatocellular carcinoma model

Impaired apoptosis and systemic toxicity of chemotherapeutic drugs make cancer treatment suboptimal. Thus, there is urgency for drug repurposing which facilitates discovery of safe and effective combination therapy. This study aimed to evaluate chloroquine's (CQ) ability to trigger TRAIL/TRAILR2 apoptotic pathway in thioacetamide (TAA)-induced hepatocellular carcinoma (HCC) either alone or in combination with doxorubicin (DOX). Moreover, its ability to attenuate DOX-induced cardiotoxicity was investigated. TAA was injected in male Sprague Dawely rats (200 mg/kg; ip; 2 times/week) for 16 weeks. After the 16th week, rats were further divided into different groups (n = 10) and treated for 7 weeks. CQ group (received CQ 25 mg/kg/day; orally), DOX group (received DOX 1 mg/kg; ip; 2 times/week) and CQ/DOX group. Liver function biomarkers, AFP, hepatic levels of MDA and GSH, serum CK-MB and LDH enzymes activity were measured. Quantitative, Real-Time PCR was used to measure TRAIL, TRAILR2, caspase-8, caspase-9, caspase-3, BCL-2 and TGF-β1 genes expression levels. Necroinflammation and fibrosis were scored by histopathological examination. CQ improved liver functions, reduced AFP level and attenuated HCC progression. CQ induced apoptosis via upregulation of TRAIL/TRAILR2, caspase-8, caspase-3 and caspase-8 genes and downregulation of BCL-2 gene. Moreover, CQ/DOX showed marked decrease in hepatic MDA level, serum CK-MB, LDH enzymes activity, as well as marked increase in hepatic GSH level. In conclusion, this work assess the in vivo efficacy of CQ/DOX combination therapy in this HCC model that not only has enhanced anti-tumor activity but it also protects against DOX-induced cardiotoxicity. Nevertheless, more studies should be performed to illustrate the molecular mechanism of CQ's cardioprotective effect.

KU-0060648 inhibits hepatocellular carcinoma cells through DNA-PKcs-dependent and DNA-PKcs-independent mechanisms

Here we tested anti-tumor activity of KU-0060648 in preclinical hepatocellular carcinoma (HCC) models. Our results demonstrated that KU-0060648 was anti-proliferative and pro-apoptotic in established (HepG2, Huh-7 and KYN-2 lines) and primary human HCC cells, but was non-cytotoxic to non-cancerous HL-7702 hepatocytes. DNA-PKcs (DNA-activated protein kinase catalytic subunit) is an important but not exclusive target of KU-0060648. DNA-PKcs knockdown or dominant negative mutation inhibited HCC cell proliferation. On the other hand, overexpression of wild-type DNA-PKcs enhanced HepG2 cell proliferation. Importantly, KU-0060648 was still cytotoxic to DNA-PKcs-silenced or -mutated HepG2 cells, although its activity in these cells was relatively weak. Further studies showed that KU-0060648 inhibited PI3K-AKT-mTOR activation, independent of DNA-PKcs. Introduction of constitutively-active AKT1 (CA-AKT1) restored AKT-mTOR activation after KU-0060648 treatment in HepG2 cells, and alleviated subsequent cytotoxicity. In vivo, intraperitoneal (i.p.) injection of KU-0060648 significantly inhibited HepG2 xenograft growth in nude mice. AKT-mTOR activation was also inhibited in xenografted tumors. Finally, we showed that DNA-PKcs expression was significantly upregulated in human HCC tissues. Yet miRNA-101, an anti-DNA-PKcs miRNA, was downregulated. Over-expression of miR-101 in HepG2 cells inhibited DNA-PKcs expression and cell proliferation. Together, these results indicate that KU-0060648 inhibits HCC cells through DNA-PKcs-dependent and -independent mechanisms.

Mitochondrial ROS activates ERK/autophagy pathway as a protected mechanism against deoxypodophyllotoxin-induced apoptosis

Deoxypodophyllotoxin (DPT) is a naturally occurring flavolignan isolated from Anthriscus sylvestris. Recently, it has been reported that DPT inhibits tubulin polymerization and induces G2/M cell cycle arrest followed by apoptosis through multiple cellular processes. Despite these findings, details regarding the cellular and molecular mechanisms underlying the DPT-mediated cell death have been poorly understood. To define a mechanism of DPT-mediated cell death response, we examined whether DPT activates signaling pathways for autophagy and apoptosis. We demonstrated that DPT inhibited cell viability and induced apoptosis in prostate cancer cell lines, as evidenced by a mitochondrial membrane potential and expression of apoptosis-related proteins. Reactive oxygen species (ROS), primarily generated from the mitochondria, play an important role in various cellular responses, such as apoptosis and autophagy. DPT significantly triggered mitochondrial ROS, which were detected by MitoSOX, a selective fluorescent dye of mitochondria-derived ROS. Furthermore, DPT induced autophagy through an up-regulation of autophagic biomarkers, including a conversion of microtubule-associated protein 1 light chain 3 - I (LC3-I) into LC3-II and a formation of acidic vesicular organelles. Moreover, mitochondrial ROS promoted AKT-independent autophagy and ERK signaling. The inhibition of autophagy with 3-methyladenine or LC3 knockdown enhanced DPT-induced apoptosis, suggesting that an autophagy plays a protective role in cell survival against apoptotic prostate cancer cells. Additionally, the results from an in vivo xenograft model confirmed that DPT inhibited tumor growth by regulating the apoptosis- and autophagy-related proteins.

AMPK-autophagy inhibition sensitizes icaritin-induced anti-colorectal cancer cell activity

The current research studied the potential effect of autophagy on icaritin-induced anti-colorectal cancer (CRC) cell activity. Treatment of icaritin in both primary and established (HT-29) CRC cells induced feedback activation of autophagy, evidenced by p62 degradation, Beclin-1 and autophagy-related gene-5 (ATG-5) upregulation, as well as light chain 3B (LC3B)-GFP puncta formation. Pharmacological inhibiting of autophagy dramatically potentiated icaritin-induced CRC cell death and apoptosis. Meanwhile, shRNA-mediated knockdown of Beclin-1 or ATG-5 also sensitized icaritin-induced CRC cell death and apoptosis. Icaritin activated AMP-activated protein kinase (AMPK) signaling in CRC cells, functioning as the upstream signaling for autophagy activation. shRNA/siRNA-mediated knockdown of AMPKα1inhibited icaritin-induced autophagy activation, but exacerbated CRC cell death. On the other hand, the AMPK activator compound 13 (C13) or the autophagy activator MHY1485 attenuated icaritin-induced cytotoxicity. In nude mice, icaritin (oral administration)-induced HT-29 tumor growth inhibition was potentiated when combined with AMPKα1 shRNA knockdown in tumors. We conclude that feedback activation of AMPK-autophagy pathway could be a primary resistance factor of icaritin.

Antioxidative and anticancer properties of Licochalcone A from licorice

ETHNOPHARMACOLOGICAL RELEVANCE

Licochalcone A (LCA) is a characteristic chalcone that is found in licorice, which is a traditional medicinal plant. In traditional medicine, LCA possesses many potential biological activities, including anti-parasitic, anti-inflammatory and antitumor activities.

AIM OF THE STUDY

To determine the antioxidant activity of LCA and, on this basis, to investigate the role of its anticancer activity.

MATERIALS AND METHODS

To validate the antioxidant activity of LCA, the proteins SOD, CAT and GPx1 were analyzed using western blotting and cellular antioxidant activity (CAA) assays. Oxidative free radicals are associated with cancer cells. Therefore, the anticancer activity of LCA was also evaluated. To assess the anticancer activity, cell viability assays were performed and apoptosis was evaluated. In addition, MAPK-related proteins were analyzed using western blotting.

RESULTS

The experimental data showed that the EC₅₀ of LCA is 58.79±0.05μg/mL and 46.29±0.05μg/mL under the two conditions tested, with or without PBS. In addition, LCA at a concentration of approximately 2-8μg/mL can induce the expression of SOD, CAT and GPx1 proteins. Further, LCA inhibits the growth of HepG2 cells through cell proliferation arrest and the subsequent induction of apoptosis, and LCA attenuated the p38/JNK/ERK signaling pathway in a dose-dependent manner.

CONCLUSION

The results showed that LCA suppresses the oxidation of cells and markedly inhibits the proliferation of cancer cells. These findings confirm the traditional use of LCA in folk medicine.

Baicalein Induces Beclin 1- and Extracellular Signal-Regulated Kinase-Dependent Autophagy in Ovarian Cancer Cells

Baicalein (BA), one of the major compounds isolated from the root of Scutellaria baicalensis Gerogi, exhibits various pharmacological effects, such as anti-oxidant, anti-inflammatory, and anticancer effects. In this study, we found that BA reduced cell viability and increased apoptosis in ovarian cancer cells. Treatment of cells with BA enhanced microtubule-associated protein light chain 3-II (LC3-II) expression, acidic vesicular organelle and GFP-LC3 fluorescence dot accumulation. Combined treatment with chloroquine and BA apparently reduced cell viability and increased the cleavage of poly (ADPribose) polymerase (PARP) in both HEY and A2780 ovarian cancer cell lines, indicating that BA induces a protective autophagy in these cells. Knockdown of Beclin 1 by siRNA remarkably decreased BA-induced LC3-II lipidation. In addition, we found an increase in the phosphorylation of extracellular signal-regulated kinase (ERK, Thr202/Thr204) and AKT (Ser473) after BA treatment, and inhibition of ERK activation by the pharmacological inhibitor U0126 or ERK siRNA blocked BA-induced autophagy. Taken together, these results suggest that BA induces Beclin 1- and ERK-dependent autophagy in ovarian cancer cells.

Autophagy prevention sensitizes AKTi-1/2-induced anti-hepatocellular carcinoma cell activity in vitro and in vivo

Molecule-targeted therapy has become the research focus for hepatocellular carcinoma (HCC). Persistent PI3K-AKT activation is often detected in HCC, representing a valuable oncotarget for treatment. Here, we tested the anti-HCC activity by a potent AKT inhibitor: AKT inhibitor 1/2 (AKTi-1/2). In both established (HepG2 and Huh-7) and primary human HCC cells, treatment with AKTi-1/2 inhibited cell survival and proliferation, but induced cell apoptosis. AKTi-1/2 blocked AKT-mTOR activation, yet simultaneously provoked cytoprotective autophagy in HCC cells. The latter was evidenced by ATG-5 and Beclin-1 upregulation, p62 downregulation as well as LC3B-GFP puncta formation. Autophagy inhibition, via pharmacological inhibitors (3-methyladenine, ammonium chloride, and bafilomycin A1) or Beclin-1 siRNA knockdown, significantly potentiated AKTi-1/2-induced HepG2 cell death and apoptosis. In nude mice, AKTi-1/2 intraperitoneal injection inhibited HepG2 tumor growth. Significantly, its anti-tumor activity in vivo was further sensitized when combined with Beclin-1 shRNA knockdown in HepG2 tumors. Together, these results demonstrate that autophagy activation serves as a main resistance factor of AKTi-1/2 in HCC cells. Autophagy prevention therefore sensitizes AKTi-1/2-induced anti-HCC activity in vitro and in vivo.

Astaxanthin enhances pemetrexed-induced cytotoxicity by downregulation of thymidylate synthase expression in human lung cancer cells

Pemetrexed, a multitargeted antifolate agent, has demonstrated clinical activity in non-small cell lung cancer (NSCLC) cells. Increased expression of thymidylate synthase (TS) is thought to be associated with resistance to pemetrexed. Astaxanthin exhibits a wide range of beneficial effects including anti-cancer and anti-inflammatory properties. In this study, we showed that down-regulating of TS expression in two NSCLC cell lines, human lung adenocarcinoma H1650 and squamous cell carcinoma H1703 cells, with astaxanthin were associated with decreased MKK1/2-ERK1/2 activity. Enforced expression of constitutively active MKK1 (MKK1-CA) vector significantly rescued the decreased TS mRNA and protein levels in astaxanthin-treated NSCLC cells. Combined treatment with a MKK1/2 inhibitor (U0126 or PD98059) further decreased the TS expression in astaxanthin-exposed NSCLC cells. Knockdown of TS using small interfering RNA (siRNA) or inhibiting ERK1/2 activity enhanced the cytotoxicity and cell growth inhibition of astaxanthin. Combination of pemetrexed and astaxanthin resulted in synergistic enhancing cytotoxicity and cell growth inhibition in NSCLC cells, accompanied with reduced activation of phospho-MKK1/2, phopho-ERK1/2, and TS expression. Overexpression of MKK1/2-CA reversed the astaxanthin and pemetrexed-induced synergistic cytotoxicity. Our findings suggested that the down-regulation of MKK1/2-ERK1/2-mediated TS expression by astaxanthin is an important regulator of enhancing the pemetrexed-induced cytotoxicity in NSCLC cells.

PEBP1, a RAF kinase inhibitory protein, negatively regulates starvation-induced autophagy by direct interaction with LC3

Autophagy plays a critical role in maintaining cell homeostasis in response to various stressors through protein conjugation and activation of lysosome-dependent degradation. MAP1LC3B/LC3B (microtubule- associated protein 1 light chain 3 β) is conjugated with phosphatidylethanolamine (PE) in the membranes and regulates initiation of autophagy through interaction with many autophagy-related proteins possessing an LC3-interacting region (LIR) motif, which is composed of 2 hydrophobic amino acids (tryptophan and leucine) separated by 2 non-conserved amino acids (WXXL). In this study, we identified a new putative LIR motif in PEBP1/RKIP (phosphatidylethanolamine binding protein 1) that was originally isolated as a PE-binding protein and also a cellular inhibitor of MAPK/ERK signaling. PEBP1 was specifically bound to PE-unconjugated LC3 in cells, and mutation (WXXL mutated to AXXA) of this LIR motif disrupted its interaction with LC3 proteins. Interestingly, overexpression of PEBP1 significantly inhibited starvation-induced autophagy by activating the AKT and MTORC1 (mechanistic target of rapamycin [serine/threonine kinase] complex 1) signaling pathway and consequently suppressing the ULK1 (unc-51 like autophagy activating kinase 1) activity. In contrast, ablation of PEBP1 expression dramatically promoted the autophagic process under starvation conditions. Furthermore, PEBP1 lacking the LIR motif highly stimulated starvation-induced autophagy through the AKT-MTORC1-dependent pathway. PEBP1 phosphorylation at Ser153 caused dissociation of LC3 from the PEBP1-LC3 complex for autophagy induction. PEBP1-dependent suppression of autophagy was not associated with the MAPK pathway. These findings suggest that PEBP1 can act as a negative mediator in autophagy through stimulation of the AKT-MTORC1 pathway and direct interaction with LC3.

Autophagy-related cell death by pan-histone deacetylase inhibition in liver cancer

Autophagy is a homeostatic, catabolic degradation process and cell fate essential regulatory mechanism. Protracted autophagy triggers cell death; its aberrant function is responsible for several malignancies. Panobinostat, a potent pan-deacetylase inhibitor, causes endoplasmic reticulum stress-induced cell death. The aim of this study was to investigate the role of autophagy in deacetylase inhibitor-triggered liver cancer cell death.HepG2 (p53wt) and Hep3B (p53 null) liver cancer cell lines were exposed to panobinostat. RT-qPCR and western blot confirmed autophagic factor modulation. Immuno-fluorescence, -precipitation and -histochemistry as well as transmission electron microscopy verified autophagosome formation. The cytotoxicity of panobinostat and autophagy modulators was detected using a real time cell viability assay.Panobinostat induced autophagy-related factor expression and aggregation. Map1LC3B and Beclin1 were significantly over-expressed in HepG2 xenografts in nude mice treated with panobinostat for 4 weeks. Subcellular distribution of Beclin1 increased with the appearance of autophagosomes-like aggregates. Cytosolic loss of p53, in HepG2, and p73, in Hep3B cells, and a corresponding gain of their nuclear level, together with modulation of DRAM1, were observed. Autophagosome aggregation was visible after 6 h of treatment. Treatment of cells stably expressing GFP-RFPtag Map1LC3B resulted in aggregation and a fluorescence switch, thus confirming autophagosome formation and maturation. Tamoxifen, an inducer of autophagy, caused only a block in cell proliferation; but in combination with panobinostat it resulted in cell death.Autophagy triggers cell demise in liver cancer. Its modulation by the combination of tamoxifen and panobinostat could be a new option for palliative treatment of hepatocellular carcinoma.

Estradiol and Estrogen Receptor Agonists Oppose Oncogenic Actions of Leptin in HepG2 Cells

Obesity is a significant risk factor for certain cancers, including hepatocellular carcinoma (HCC). Leptin, a hormone secreted by white adipose tissue, precipitates HCC development. Epidemiology data show that men have a much higher incidence of HCC than women, suggesting that estrogens and its receptors may inhibit HCC development and progression. Whether estrogens antagonize oncogenic action of leptin is uncertain. To investigate potential inhibitory effects of estrogens on leptin-induced HCC development, HCC cell line HepG2 cells were treated with leptin in combination with 17 β-estradiol (E2), estrogen receptor-α (ER-α) selective agonist PPT, ER-β selective agonist DPN, or G protein-coupled ER (GPER) selective agonist G-1. Cell number, proliferation, and apoptosis were determined, and leptin- and estrogen-related intracellular signaling pathways were analyzed. HepG2 cells expressed a low level of ER-β mRNA, and leptin treatment increased ER-β expression. E2 suppressed leptin-induced HepG2 cell proliferation and promoted cell apoptosis in a dose-dependent manner. Additionally E2 reversed leptin-induced STAT3 and leptin-suppressed SOCS3, which was mainly achieved by activation of ER-β. E2 also enhanced ERK via activating ER-α and GPER and activated p38/MAPK via activating ER-β. To conclude, E2 and its receptors antagonize the oncogenic actions of leptin in HepG2 cells by inhibiting cell proliferation and stimulating cell apoptosis, which was associated with reversing leptin-induced changes in SOCS3/STAT3 and increasing p38/MAPK by activating ER-β, and increasing ERK by activating ER-α and GPER. Identifying roles of different estrogen receptors would provide comprehensive understanding of estrogenic mechanisms in HCC development and shed light on potential treatment for HCC patients.

Chloroquine alleviates etoposide-induced centrosome amplification by inhibiting CDK2 in adrenocortical tumor cells

The antitumor drug etoposide (ETO) is widely used in treating several cancers, including adrenocortical tumor (ACT). However, when used at sublethal doses, tumor cells still survive and are more susceptible to the recurring tumor due to centrosome amplification. Here, we checked the effect of sublethal dose of ETO in ACT cells. Sublethal dose of ETO treatment did not induce cell death but arrested the ACT cells in G2/M phase. This resulted in centrosome amplification and aberrant mitotic spindle formation leading to genomic instability and cellular senescence. Under such conditions, Chk2, cyclin A/CDK2 and ERK1/2 were aberrantly activated. Pharmacological inactivation of Chk2, CDK2 or ERK1/2 or depletion of CDK2 or Chk2 inhibited the centrosome amplification in ETO-treated ACT cells. In addition, autophagy was activated by ETO and was required for ACT cell survival. Chloroquine, the autophagy inhibitor, reduced ACT cell growth and inhibited ETO-induced centrosome amplification. Chloroquine alleviated CDK2 and ERK, but not Chk2, activation and thus inhibited centrosome amplification in either ETO- or hydroxyurea-treated ACT cells. In addition, chloroquine also inhibited centrosome amplification in osteosarcoma U2OS cell lines when treated with ETO or hydroxyurea. In summary, we have demonstrated that chloroquine inhibited ACT cell growth and alleviated DNA damage-induced centrosome amplification by inhibiting CDK2 and ERK activity, thus preventing genomic instability and recurrence of ACT.

Inside the biochemical pathways of thymidylate synthase perturbed by anticancer drugs: Novel strategies to overcome cancer chemoresistance

Our current understanding of the mechanisms of action of antitumor agents and the precise mechanisms underlying drug resistance is that these two processes are directly linked. Moreover, it is often possible to delineate chemoresistance mechanisms based on the specific mechanism of action of a given anticancer drug. A more holistic approach to the chemoresistance problem suggests that entire metabolic pathways, rather than single enzyme targets may better explain and educate us about the complexity of the cellular responses upon cytotoxic drug administration. Drugs, which target thymidylate synthase and folate-dependent enzymes, represent an important therapeutic arm in the treatment of various human malignancies. However, prolonged patient treatment often provokes drug resistance phenomena that render the chemotherapeutic treatment highly ineffective. Hence, strategies to overcome drug resistance are primarily designed to achieve either enhanced intracellular drug accumulation, to avoid the upregulation of folate-dependent enzymes, and to circumvent the impairment of DNA repair enzymes which are also responsible for cross-resistance to various anticancer drugs. The current clinical practice based on drug combination therapeutic regimens represents the most effective approach to counteract drug resistance. In the current paper, we review the molecular aspects of the activity of TS-targeting drugs and describe how such mechanisms are related to the emergence of clinical drug resistance. We also discuss the current possibilities to overcome drug resistance by using a molecular mechanistic approach based on medicinal chemistry methods focusing on rational structural modifications of novel antitumor agents. This paper also focuses on the importance of the modulation of metabolic pathways upon drug administration, their analysis and the assessment of their putative roles in the networks involved using a meta-analysis approach. The present review describes the main pathways that are modulated by TS-targeting anticancer drugs starting from the description of the normal functioning of the folate metabolic pathway, through the protein modulation occurring upon drug delivery to cultured tumor cells as well as cancer patients, finally describing how the pathways are modulated by drug resistance development. The data collected are then analyzed using network/netwire connecting methods in order to provide a wider view of the pathways involved and of the importance of such information in identifying additional proteins that could serve as novel druggable targets for efficacious cancer therapy.

Combination treatment with perifosine and MEK-162 demonstrates synergism against lung cancer cells in vitro and in vivo

Lung cancer is a global health problem. The search for new therapeutic approaches for the treatment of lung cancer is important. Here, we reported that the AKT inhibitor perifosine and the MEK\ERK inhibitor MEK-162 synergistically induced lung cancer cell (A549 and H460 lines) growth inhibition and apoptosis. The combined efficiency was significantly higher than either agent alone. For the molecular study, perifosine and MEK-162 worked together to concurrently block AKT, mammalian target of rapamycin (mTOR) complex 1 (mTORC1), and MEK-ERK signalings in lung cancer cells, while either agent alone only affected one or two signalings with lower efficiency. In vivo, MEK-162 and perifosine co-administration dramatically inhibited A549 lung cancer xenograft growth, without inducing apparent toxicities. The synergistic activity in vivo was again superior than either agent alone. Thus, perifosine and MEK-162 combination is biologically plausible by acting through effects on different proliferation and survival-related signaling pathways. Our in vitro and in vivo results support the feasibility of investigating the synergism regimen in clinical tests.