Autophagic Cell Death Research Articles

Deacetylation of GLUD1 maintains the survival of lung adenocarcinoma cells under glucose starvation by inhibiting autophagic cell death

Enhanced glutamine catabolism is one of the main metabolic features of cancer, providing energy and intermediate metabolites for cancer progression. However, the functions of glutamine catabolism in cancer under nutrient deprivation need to be further clarified. Here, we discovered that deacetylation of glutamate dehydrogenase 1 (GLUD1), one of the key enzymes in glutamine catabolism, maintains the survival of lung adenocarcinoma (LUAD) cells under glucose starvation by inhibiting autophagic cell death. We found that glucose starvation increased GLUD1 activity by reducing its acetylation on Lys84 and promoted its active hexamer formation. Besides, deacetylation of GLUD1 induced its cytoplasmic localization, where GLUD1 was ubiquitinated in K63-linkage by TRIM21, leading to the binding of GLUD1 with cytoplasmic glutaminase KGA. These two effects enhanced glutamine metabolism both in mitochondria and cytoplasm, increased the production of alpha-ketoglutarate (α-KG). Meanwhile, cytoplasmic GLUD1 also interacted with p62 and prevented its acetylation, leading to the inhibition of p62 body formation. All these effects blocked autophagic cell death of LUAD cells under glucose starvation. Taken together, our results reveal a novel function of GLUD1 under glucose deprivation in LUAD cells and provide new insights into the functions of glutamine catabolism during cancer progression.

Fucoidan Inhibits Prostate Cancer Growth Through Modulation of Different Cell Deaths.

Docetaxel (DOC) is the main chemotherapeutic agent for the treatment of advanced metastatic prostate cancer. Docetaxel shows anticancer effects by preventing the depolymerization of microtubules in the cell, therefore preventing cell division. However, the low survival effect of docetaxel has prompted researchers to search for novel therapeutic agents. Fucoidan (FUC) is a sulfated polysaccharide derived from brown algae. It has many bioactivities which makes fucoidan a promising anticancer agent. In this study, the potential anti-tumorigenic and preventive effects of fucoidan with or without docetaxel in prostate cancer were investigated by analyzing different cell death modalities. The in-vivo six groups (n = 8) were conducted; preventive (Pt), docetaxel treated after preventive (Pt-D), control, fucoidan (FUC), docetaxel (DOC), and FUC and DOC (FUC+DOC) combination. Apoptotic, necroptotic, and autophagic cell death-related protein expressions were assessed in tumor tissues by using immunohistochemical staining. Oxidative stress-related lipid peroxidation, glutathione peroxidase, and glutathione levels were also determined in tumor tissues. Although apoptotic, necroptotic, and autophagic cell deaths were significantly induced in agent-treated groups compared to the control. Apoptotic cell death was more significantly induced in FUC and FUC+DOC-treated groups. Necroptotic cell death was increased considerably by inducing MLKL protein expression in all treatment groups. In the FUC, Pt, and DOC groups, LC3A/B expressions were significantly increased. DOC, FUC+DOC, and Pt-D treatments caused a significant increase in Beclin-1 expression. Oxidative stress-related MDA, GPX, and GSH levels significantly decreased with FUC treatment. The anti-tumorigenic effects of FUC and DOC were also demonstrated through tumor size reduction. According to the findings of this study, FUC inhibited tumor growth temporally and dimensionally, especially in preventive applications. FUC and FUC+DOC combinations in both treatment groups showed anti-tumorigenic effects. The results of this study suggest that fucoidan is a promising anticancer agent against prostate cancer. FUC can be considered as a preventive or treatment agent in prostate cancer therapy with DOC. Further studies are needed to fully elucidate the mechanism of action of fucoidan in metastatic prostate cancer.

Hernandonine-mediated autophagic cell death in hepatocellular carcinoma: Interplay of p53 and YAP signaling pathways

Hepatocellular carcinoma (HCC), the primary form of liver cancer, is the third leading cause of cancer-related death globally. Hernandonine is a natural alkaloid derived from Hernandia nymphaeifolia that has been shown to exert various biological functions. In a previous study, hernandonine was shown to suppress the proliferation of several solid tumor cell lines without affecting normal human cell lines. However, little is known about the effect of hernandonine on HCC. Therefore, this study aimed to investigate the effect and mechanism of hernandonine on HCC in relation to autophagy. We found that hernandonine inhibited HCC cell growth in vitro and in vivo. In addition, hernandonine elicited autophagic cell death and DNA damage in HCC cells. RNA-seq analysis revealed that hernandonine upregulated p53 and Hippo signaling pathway-related genes in HCC cells. Small RNA interference of p53 resulted in hernandonine-induced autophagic cell death attenuation. However, inhibition of YAP sensitized HCC cells to hernandonine by increasing the autophagy induction. This is the first study to illustrate the complex involvement of p53 and YAP in the hernandonine-induced autophagic cell death in human HCC cells. Our findings provide novel evidence for the potential of hernandonine as a therapeutic agent for HCC treatment.

The dual-specificity kinase MoLKH1-mediated cell cycle, autophagy, and suppression of plant immunity is critical for development and pathogenicity of Magnaporthe oryzae

Cell cycle progression, autophagic cell death during appressorium development, and ROS degradation at the infection site are important for the development of rice blast disease. However, the association of cell cycle, autophagy and ROS detoxification remains largely unknown in M. oryzae. Here, we identify the dual-specificity kinase MoLKH1, which serves as an important cell cycle regulator required for appressorium formation by regulating cytokinesis and cytoskeleton in M. oryzae. MoLKH1 is transcriptionally activated by H2O2 and required for H2O2-induced autophagic cell death and suppression of ROS-activated plant defense during plant invasion of M. oryzae. In addition, the Molkh1 mutant also showed several phenotypic defects, including delayed growth, abnormal conidiation, damaged cell wall integrity, impaired glycogen and lipid transport, reduced secretion of extracellular enzymes and effectors, and attenuated virulence of M. oryzae. Nuclear localization of MoLKH1 requires the nuclear localization sequence, Lammer motif, as well as the kinase active site and ATP-binding site in this protein. Site-directed mutagenesis showed that each of them plays crucial roles in fungal growth and pathogenicity of M. oryzae. In conclusion, our results demonstrate that MoLKH1-mediated cell cycle, autophagy, and suppression of plant immunity play crucial roles in development and pathogenicity of M. oryzae.

Bacillus sonorinses derived exopolysaccharide enhances cell cycle arrest, apoptosis, necrosis, autophagy and COX-2 down regulation in liver cancer cells

BackgroundHepatocellular carcinoma (HCC) is one of the most serious types of cancer that accounts for numerous cancer deaths worldwide. HCC is poorly prognosed and is a highly chemotherapy-resistant tumor. Therefore, new treatments are urgently needed. Exopolysaccharides (EPS-1) produced from the novel Bacillus sonorensis strain was found to exhibit chemopreventive effects against cancer. ObjectiveEvaluating the anti-cancer cytotoxic effect of exopolysaccharides (EPS-1) produced by the newly studied Bacillus sonorensis strain SAmt2. MethodsThe cytotoxic activity was investigated through cell cycle, apoptosis, and autophagy analyses using flow cytometry technique. Also, the effect of EPS-1 on Huh7 release of COX-2 was examined using ELISA. ResultsOur results revealed that EPS-1exhibit an anti-proliferative effect on Huh7 cells through decreasing the percentage of cells at the S-phase and G2 phase, while increasing the cell population at the sub-G1 and G1 phases. Apoptosis analysis showed that EPS-1 increased necrotic and apoptotic cell fractions in EPS-1 treated Huh7. In addition, it induced significant autophagic cell death in the Huh7.Finally, antiproliferative and apoptosis induction results were supportedby ELISA assay results where the protein level of COX-2 was declined. Conclusion: In conclusion, EPS-1 derived from B. sonorensis SAmt2, is a promising proliferation inhibitor of Huh7 cells with potential anticancer effects.

Determination of Inhibitory Effect of PKM2 Enzyme and Antitumoral Activity of Novel Coumarin-Naphthoquinone Hybrids.

Oral squamous cell carcinoma (OSCC) represents the primary form of oral cancer, posing a significant global health threat. The existing chemotherapy options are accompanied by notable side effects impacting patient treatment adherence. Consequently, the exploration and development of novel substances with enhanced anticancer effects and fewer side effects have become pivotal in the realms of biological and chemical science. This work presents the pioneering examples of naphthoquinone-coumarin hybrids as a new category of highly effective cytotoxic substances targeting oral squamous cell carcinoma (OSCC). Given the significance of both naphthoquinones and coumarins as essential pharmacophores/ privileged structures in the quest for anticancer compounds, this study focused on the synthesis and evaluation of novel naphthoquinones/coumarin hybrids against oral squamous cell carcinoma. By several in vitro, in silico, and in vivo approaches, we demonstrated that compound 6e was highly cytotoxic against OSCC cells and several other cancer cell types and was more selective than current chemotherapeutic drugs (carboplatin) and the naphthoquinone lapachol. Furthermore, compound 6e was non-hemolytic and tolerated in vivo at 50 mg/kg with an LD50 of 62.5 mg/kg. Furthermore, compound 6e did not induce apoptosis and cell cycle arrest but led to intracellular vesicle formation with LC3 aggregation in autophagosomes, suggesting an autophagic cell death. Additionally, 6e had a high-affinity potential for PKM2 protein, higher than the known ligands, such as lapachol or shikonin, and was able to inhibit this enzyme activity in vitro. We assert that compound 6e shows promise as a potential lead for a novel chemotherapeutic drug targeting OSCC, with potential applicability to other cancer types.

Effect of punicalagin on the autophagic cell death in triple-negative breast cancer cells.

Effect of punicalagin on the autophagic cell death in triple-negative breast cancer cells.

Peimenine unleashes therapeutic promise in urothelial bladder cancer: inhibition of proliferation, induction of cell death and modulation of key pathways.

Peimenine (PEI) is a steroid alkaloid substance isolated from Fritillaria thunbergii bulbs. It has various pharmacological activities, such as relief from coughs and asthma, expectorant properties, antibacterial effects, sedative qualities, and anti-inflammatory properties. Notably, PEI can effectively inhibit the proliferation and tumor formation of liver cancer and osteosarcoma cells by inducing autophagic cell death. However, the precise effect and mechanisms of PEI on urothelial bladder cancer (UBC) cells remain uncertain. Thus, this study aims to investigate the impact of PEI on UBC cells both invivo and invitro. The IC50 values of BIU-87 and EJ-1 cells after 48 h were 710.3 and 651.1 μg/mL, respectively. Additionally, PEI blocked the cell cycle in BIU-87 and EJ-1 cells during the G1 phase. Furthermore, it hindered the migration of BIU-87 and EJ-1 cells substantially. PEI significantly inhibited the tumor development of EJ-1 cells within the xenograft tumor model invivo. Mechanically, PEI augmented the protein and mRNA expression of BIM, BAK1, and Cytochrome C (CYCS) in UBC cells. Taken together, PEI suppressed the proliferation of UBC cells both invitro and invivo by inducing cell death and cell cycle arrest, suggesting that PEI could be applied in the treatment of UBC.

Hernandezine acts as a CDK4 suppressor inhibiting tumor growth by the CDK4/PKM2/NRF2 axis in colon cancer

BackgroundThe cyclin-dependent kinase 4 (CDK4) interacts with its canonical and non-canonical substrates modulating the cell cycle in tumor cells. However, the potential substrates and the beyond-cell-cycle-regulated functions of CDK4 in colon cancer (CC) are still unknown. Hernandezine (HER) is previously verified to induce G0/G1 phase arrest and autophagic cell death in human cancer cells, which implies that HER might target G0/G1 phase-related proteins, including CDK4. PurposeThe present study tried to investigate the glycolytic metabolism and oxidative stress functions of CDK4 in colon cancer. Furthermore, the inhibitory effects and potential binding sites of HER on CDK4, as well as its anti-tumor activity were investigated in CC cells. MethodsThe mass spectrometry assay was performed to identify potential endogenous substrates of CDK4 and the correlation between glycolytic metabolic rate and CDK4 level in COAD patient tissues. Meanwhile, after inhibiting the activity or the expression of CDK4, the binding capacity of CDK4 to PKM2 and NRF2 and the latter two protein distributions in cytoplasm and nucleus were detected in CC cells. In vitro, the regulatory effects of the CDK4-PKM2-NRF2 axis on glycolysis and oxidative stress were performed by ECAR, OCR, and ROS assay. The inhibitory effect of HER on CDK4 activity was explored in CC cells and the potential binding sites were predicted and testified in vitro. Furthermore, tumor growth inhibition of HER by suppressing the CDK4-PKM2-NRF2 axis was also investigated in vitro and in vivo. ResultsPKM2 and NRF2 were identified as endogenous substrates of CDK4 and, high-expressed CDK4 was associated with low-level glycolysis in COAD. In vitro, inactivated CDK4 facilitated CDK4-PKM2-NRF2 complex formation which resulted in 1) inhibited PKM2 activity and retarded the glycolytic rate; 2) cytoplasm-detained NRF2 failed to transcript anti-oxidative gene expressions and induced oxidant stress. Additionally, as a CDK4 inhibitor, HER developed triple anti-tumor effects including induced G0/G1 phase arrest, suppressed glycolysis, and disrupted the anti-oxidative capacity of CC cells. Conclusion: The results first time revealed that CDK4 modulated glycolytic and anti-oxidative capacity of CC cells via bound to its endogenous substrates, PKM2 and NRF2. Additionally, 140Asp145Asn amino acid sites of CDK4 were potential targets of HER. HER exerts anti-tumor activity by inhibited the activity of CDK4, promoted the CDK4-PKM2-NRF2 complex formation in the CC cells.

Neuronal autosis is Na+/K+-ATPase alpha 3-dependent and involved in hypoxic-ischemic neuronal death

Macroautophagy (hereafter called autophagy) is an essential physiological process of degradation of organelles and long-lived proteins. The discovery of autosis, a Na+/K+-ATPase (ATP1)-dependent type of autophagic cell death with specific morphological and biochemical features, has strongly contributed to the acceptance of a pro-death role of autophagy. However, the occurrence and relevance of autosis in neurons has never been clearly investigated, whereas we previously provided evidence that autophagy mechanisms could be involved in neuronal death in different in vitro and in vivo rodent models of hypoxia-ischemia (HI) and that morphological features of autosis were observed in dying neurons following rat perinatal cerebral HI. In the present study, we demonstrated that neuronal autosis could occur in primary cortical neurons using two different stimulations enhancing autophagy flux and neuronal death: a neurotoxic concentration of Tat-BECN1 (an autophagy-inducing peptide) and a hypoxic/excitotoxic stimulus (mimicking neuronal death induced by cerebral HI). Both stimulations induce autophagic neuronal death (dependent on canonical autophagic genes and independent on apoptotic, necroptotic or ferroptotic pathways) with all morphological and biochemical (ATP1a-dependent) features of autosis. However, we demonstrated that autosis is not dependent on the ubiquitous subunit ATP1a1 in neurons, as in dividing cell types, but on the neuronal specific ATP1a3 subunit. We also provided evidence that, in different in vitro and in vivo models where autosis is induced, ATP1a3-BECN1 interaction is increased and prevented by cardiac glycosides treatment. Interestingly, an increase in ATP1a3-BECN1 interaction is also detected in dying neurons in the autoptic brains of human newborns with severe hypoxic-ischemic encephalopathy (HIE). Altogether, these results suggest that ATP1a3-BECN1-dependent autosis could play an important role in neuronal death in HI conditions, paving the way for the development of new neuroprotective strategies in hypoxic-ischemic conditions including in severe case of human HIE.

Combination of betulinic acid and EGFR-TKIs exerts synergistic anti-tumor effects against wild-type EGFR NSCLC by inducing autophagy-related cell death via EGFR signaling pathway

BackgroundEpidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of lung cancer patients with mutated EGFR. However, the efficacy of EGFR-TKIs in wild-type EGFR tumors has been shown to be marginal. Methods that can sensitize EGFR-TKIs to EGFR wild-type NSCLC remain rare. Hence, we determined whether combination treatment can maximize the therapeutic efficacy of EGFR-TKIs.MethodsWe established a focused drug screening system to investigate candidates for overcoming the intrinsic resistance of wild-type EGFR NSCLC to EGFR-TKIs. Molecular docking assays and western blotting were used to identify the binding mode and blocking effect of the candidate compounds. Proliferation assays, analyses of drug interactions, colony formation assays, flow cytometry and nude mice xenograft models were used to determine the effects and investigate the molecular mechanism of the combination treatment.ResultsBetulinic acid (BA) is effective at targeting EGFR and synergizes with EGFR-TKIs (gefitinib and osimertinib) preferentially against wild-type EGFR. BA showed inhibitory activity due to its interaction with the ATP-binding pocket of EGFR and dramatically enhanced the suppressive effects of EGFR-TKIs by blocking EGFR and modulating the EGFR-ATK-mTOR axis. Mechanistic studies revealed that the combination strategy activated EGFR-induced autophagic cell death and that the EGFR-AKT-mTOR signaling pathway was essential for completing autophagy and cell cycle arrest. Activation of the mTOR pathway or blockade of autophagy by specific chemical agents markedly attenuated the effect of cell cycle arrest. In vivo administration of the combination treatment caused marked tumor regression in the A549 xenografts.ConclusionsBA is a potential wild-type EGFR inhibitor that plays a critical role in sensitizing EGFR-TKI activity. BA combined with an EGFR-TKI effectively suppressed the proliferation and survival of intrinsically resistant lung cancer cells via the inhibition of EGFR as well as the induction of autophagy-related cell death, indicating that BA combined with an EGFR-TKI may be a potential therapeutic strategy for overcoming the primary resistance of wild-type EGFR-positive lung cancers.Graphical abstract

Examination of the effects of excess microalgae availability on the disruption of mussel byssus secretion

The present study evaluated the effects of food availability on byssus secretion in the hard-shelled mussel Mytilus coruscus. Byssus production was evaluated, and foot tissue transcriptomes, the site of byssus production, were generated. The results showed that byssus secretion was disrupted in mussels fed high levels of microalgae (HFL, 88.8 mg/L day−1), compared to the control group (p < 0.05), and that more byssus production occurred in the HFL group during the recovery period. Byssus secretion was not affected in mussels fed low levels of microalgae (8.88 × 10−3 mg/L day−1), but the shedding of byssus filaments was significantly increased compared to the control mussels (p < 0.05). Transcriptome data of the foot tissue revealed that lysosome, FoxO signaling, and autophagy pathways involved in autophagic cell death and apoptosis were significantly affected (p < 0.05) and may explain differences in byssus growth under modified food availability in M. coruscus. High feed levels modified metabolic pathways, such as sphingolipid, tyrosine, and phenylalanine, and downregulated genes coding for mussel foot proteins, which may explain reduced byssus production. The study found that contrary to expectation increased food availability reduced mussel byssus production by altering foot metabolism and promoting autophagy of foot tissue.

Nitric oxide water-driven immunogenic cell death: Unfolding mitochondrial dysfunction's role in sensitizing lung adenocarcinoma to ferroptosis and autophagic cell death

Non-small cell lung cancer (NSCLC), particularly lung adenocarcinoma (LUAD), significantly influences cancer-related mortality and is frequently considered by poor therapeutic responses due to genetic alterations. Cancer cells possess an inclination to develop resistance to individual treatment modalities, thus it is necessary to investigate several pathways simultaneously to obtain insights that will aid in the establishment of improved therapeutic approaches. Exploring regulated cell death (RCD) mechanisms offers promising avenues to augment immunotherapy by reshaping the tumor microenvironment (TME). Here, we investigated the prospective of microwave plasma-infused nitric oxide water (NOW) to initiate immunogenic cell death (ICD) while concurrently modulating autophagy and ferroptosis signaling in LUAD-associated A549 cells. Plasma treatment results in stable NO species nitrite/nitrate (NO2−/NO3−) in the water, altering its physicochemical properties. Analysis of ICD markers reveals increased expression of damage-associated molecular patterns (DAMPs) at both protein and mRNA levels post-NOW exposure. Intracellular reactive oxygen and nitrogen species (RONS) accumulation suggests NO-mediated mitochondrial dysfunction, triggering autophagy induction. Flow cytometry and western blotting confirm alterations in autophagy regulators Beclin 1 and SQSTM1. Furthermore, NOW treatment induces lipid peroxidation and upregulates ferroptosis-associated genes, as determined by qRT-PCR. Transmission electron microscopy (TEM) imaging reveals autophagosome formation and loss of cristae structures, corroborating the occurrence of autophagy and ferroptosis. Our findings propose that NOW may considered as inducer of ICD and the stimulation of other RCD-related proteins may enhance the anti-tumor immunogenicity.

Isogarcinol inhibits nasopharyngeal carcinoma growth through mitochondria-mediated autophagic cell death

Background and aimsIsogarcinol, a natural compound extracted from the fruits of Garcinia oblongifolia, has potential chemopreventive activity. This study aimed to elucidate the anti-tumor effects and mechanism of action of isogarcinol on nasopharyngeal carcinoma (NPC). MethodsIsogarcinol was isolated from Garcinia oblongifolia by using chromatographic separation. The anti-tumor effects of isogarcinol in NPC cells were tested by MTT assay, flow cytometry, wound healing assay, western blotting, transwell assay, colony formation assay, immunofluorescence, and transmission electron microscopy (TEM). The anti-tumor efficacy in vivo was evaluated in NPC cells xenograft models. ResultsFunctional studies revealed that isogarcinol inhibited the proliferation, colony formation, migration and invasion abilities of NPC cells in vitro. Isogarcinol caused mitochondrial damage to overproduce reactive oxygen species through reducing the mitochondrial membrane potential and ΔΨm. Isogarcinol also substantially inhibited NPC cells growth in a xenograft tumor model without any obvious toxicity when compared with paclitaxel (PTX). Mechanistic studies have illustrated that isogarcinol increased the Bax/Bcl-2 ratio, cleaved caspase-3, and cytoplasmic cytochrome C levels to induce mitochondrial apoptosis. The ROS overproduction by isogarcinol could suppress EMT pathway via decreasing the levels of p-Akt and Snail. Furthermore, isogarcinol promoted the conversion of LC3-Ⅰ to LC3-Ⅱ, but increased p62 level to block autophagic flux, resulting in the accumulation of damaged mitochondria to promote autophagic cell death in NPC cells. ConclusionThis study provides a new theoretical foundation for the anti-tumor application of Garcinia oblongifolia and confirms that isogarcinol could be developed as a candidate drug for NPC treatment with low toxicity.

Clemastine and hyperthermia enhance sensitization of osteosarcoma cells for apoptosis

ABSTRACT Clemastine is an antagonist of histamine H1 receptor may provide benefits in the treatment of osteosarcoma (OS). In the current study, we used hyperthermia approach to sensitize OS cells to clemastine-mediated cell death. Osteosarcoma U-2 OS and Saos-2 cells were treated with clemastine at 37°C, followed by 42°C for 2 h, and released at 37°C for 6 h. The impact of clemastine and hyperthermia on OS cell survival and autophagy-mediated cell death was investigated. Exposure of U-2 OS and Saos-2 cells to clemastine and hyperthermia (42°C) inhibited dose-dependent clemastine-mediated cell survival by increasing cell apoptosis. Hyperthermia and clemastine exposure modulated inflammatory and unfolded protein response (UPR) signaling differentially in U-2 OS and Saos-2 cells. Exposure of U-2 OS and Saos-2 cells to hyperthermia and clemastine inhibited AKT/mTOR and induced expression of the autophagy biomarkers LC3B II and LC3-positive puncta formation. The inhibition of autophagy by 3-methyladenine blocked hyperthermia and clemastine-mediated induction of LC3B II, LC3-positive puncta formation, and OS cell apoptosis. These results indicate that clemastine and hyperthermia sensitize OS cell lines by inducing increased autophagic cell death. Collectively, our data suggest that hyperthermia along with antihistamine therapy may provide an improved approach for the treatment of OS.

SCFFBXW5-mediated degradation of AQP3 suppresses autophagic cell death through the PDPK1-AKT-MTOR axis in hepatocellular carcinoma cells

ABSTRACT AQP3 (aquaporin 3 (Gill blood group)), a member of the AQP family, is an aquaglyceroporin which transports water, glycerol and small solutes across the plasma membrane. Beyond its role in fluid transport, AQP3 plays a significant role in regulating various aspects of tumor cell behavior, including cell proliferation, migration, and invasion. Nevertheless, the underlying regulatory mechanism of AQP3 in tumors remains unclear. Here, for the first time, we report that AQP3 is a direct target for ubiquitination by the SCFFBXW5 complex. In addition, we revealed that downregulation of FBXW5 significantly induced AQP3 expression to prompt macroautophagic/autophagic cell death in hepatocellular carcinoma (HCC) cells. Mechanistically, AQP3 accumulation induced by FBXW5 knockdown led to the degradation of PDPK1/PDK1 in a lysosomal-dependent manner, thus inactivating the AKT-MTOR pathway and inducing autophagic death in HCC. Taken together, our findings revealed a previously undiscovered regulatory mechanism through which FBXW5 degraded AQP3 to suppress autophagic cell death via the PDPK1-AKT-MTOR axis in HCC cells. Abbreviation: BafA1: bafilomycin A1; CQ: chloroquine; CRL: CUL-Ring E3 ubiquitin ligases; FBXW5: F-box and WD repeat domain containing 5; HCC: hepatocellular carcinoma; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; 3-MA: 3-methyladenine; PDPK1/PDK1: 3-phosphoinositide dependent protein kinase 1; RBX1/ROC1: ring-box 1; SKP1: S-phase kinase associated protein 1; SCF: SKP1-CUL1-F-box protein.

A Redox-Triggered Autophagy-Induced Nanoplatform with PD-L1 Inhibition for Enhancing Combined Chemo-Immunotherapy.

Epirubicin (EPI) alone can trigger mildly protective autophagy in residual tumor cells, resulting in an immunosuppressive microenvironment. This accelerates the recurrence of residual tumors and leads to antiprogrammed death ligand 1 (anti-PD-1)/PD-L1 therapy resistance, posing a significant clinical challenge in tumor immunotherapy. The combination of checkpoint inhibitors targeting the PD-1/PD-L1 pathway and amplifying autophagy presents an innovative approach to tumor treatment, which can prevent tumor immune escape and enhance therapeutic recognition. Herein, we aimed to synthesize a redox-triggered autophagy-induced nanoplatform with SA&EA-induced PD-L1 inhibition. The hyaluronic acid (HA) skeleton and arginine segment promoted active nanoplatform targeting, cell uptake, and penetration. The PLGLAG peptide was cleaved by overexpressing matrix metalloproteinase-2 (MMP-2) in the tumor microenvironment, and the PD-L1 inhibitor D-PPA was released to inhibit tumor immune escape. The intense autophagy inducers, STF-62247 and EPI, were released owing to the cleavage of disulfide bonds influenced by the high glutathione (GSH) concentration in tumor cells. The combination of EPI and STF induced apoptosis and autophagic cell death, effectively eliminating a majority of tumor cells. This indicated that the SA&EA nanoplatform has better therapeutic efficacy than the single STF@AHMPP and EPI@AHMPTP groups. This research provided a way to set up a redox-triggered autophagy-induced nanoplatform with PD-L1 inhibition to enhance chemo-immunotherapy.

Phenformin activates ER stress to promote autophagic cell death via NIBAN1 and DDIT4 in oral squamous cell carcinoma independent of AMPK

The efficient clinical treatment of oral squamous cell carcinoma (OSCC) is still a challenge that demands the development of effective new drugs. Phenformin has been shown to produce more potent anti-tumor activities than metformin on different tumors, however, not much is known about the influence of phenformin on OSCC cells. We found that phenformin suppresses OSCC cell proliferation, and promotes OSCC cell autophagy and apoptosis to significantly inhibit OSCC cell growth both in vivo and in vitro. RNA-seq analysis revealed that autophagy pathways were the main targets of phenformin and identified two new targets DDIT4 (DNA damage inducible transcript 4) and NIBAN1 (niban apoptosis regulator 1). We found that phenformin significantly induces the expression of both DDIT4 and NIBAN1 to promote OSCC autophagy. Further, the enhanced expression of DDIT4 and NIBAN1 elicited by phenformin was not blocked by the knockdown of AMPK but was suppressed by the knockdown of transcription factor ATF4 (activation transcription factor 4), which was induced by phenformin treatment in OSCC cells. Mechanistically, these results revealed that phenformin triggers endoplasmic reticulum (ER) stress to activate PERK (protein kinase R-like ER kinase), which phosphorylates the transitional initial factor eIF2, and the increased phosphorylation of eIF2 leads to the increased translation of ATF4. In summary, we discovered that phenformin induces its new targets DDIT4 and especially NIBAN1 to promote autophagic and apoptotic cell death to suppress OSCC cell growth. Our study supports the potential clinical utility of phenformin for OSCC treatment in the future.

Drosophila Nhe2 overexpression induces autophagic cell death.

Autophagy is a conserved catabolic process where double membrane-bound structures form around macromolecules or organelles targeted for degradation. Autophagosomes fuse with lysosomes to facilitate degradation and macromolecule recycling for homeostasis or growth in a cell autonomous manner. In cancer cells, autophagy is often up-regulated and helps cancer cells survive nutrient deprivation and stressful growth conditions. Here, we propose that the increased intracellular pH (pHi) common to cancer cells is sufficient to induce autophagic cell death. We previously developed tools to increase pHi in the Drosophila eye via overexpression of DNhe2, resulting in aberrant patterning and reduced tissue size. We examined fly eyes at earlier stages of development and found fewer interommatidial cells. We next tested whether this decrease in cell number was due to increased cell death. We found that the DNhe2-induced cell death was caspase independent, which is inconsistent with apoptosis. However, this cell death required autophagy genes, which supports autophagy as the mode of cell death. We also found that expression of molecular markers supports increased autophagy. Together, our findings suggest new roles for ion transport proteins in regulating conserved, critical developmental processes and provide evidence for new paradigms in growth control.

Deciphering the potential of a novel cytostatic autophagy modulator for the treatment of brain cancer along with reduction in brain inflammation

Background and Purpose: Glioblastoma multiforme (GBM) is the most aggressive form of brain tumor, with significant failure of current treatment options, with the five-year survival rate of GBM being less than 7%. Temozolomide (TMZ), the standard chemotherapy, leads to severe toxicity, whereas radiation therapy leads to necrosis. Moreover, GBM leads to severe neuroinflammation, leading to severe fatalities and, thus, poor quality of life in patients. Therefore, owing to the pressing need for safer treatment alternatives, we repurposed a novel FDA-approved acetamide, BRZ, which not only exhibited a significant curbing of GBM progression but also reduced neuroinflammation. Thus, our study provides a treatment option that can also lead to better quality of life in GBM patients. Methods: Sulfarhodamine B cytotoxicity assay was performed on human (SF268, SF295, SF188) and murine (CT2A-LUC) GBM cell lines for both BRZ and TMZ. In the quest for figuring out the mode of cell-growth suppression, we performed annexin and acridine orange flow cytometry assays along with b-galactosidase cellular senescence staining assay. Cellular staining was also confirmed using confocal microscopy. Oncogenic modulation due to BRZ was studied by performing western blotting. In order to study the effect of BRZ on neuroinflammation, we examined the modulation of different neuroinflammatory genes on LPS-stimulated human and murine microglia using RT-qPCR and western blotting. We corroborated our in vitro findings by investigating the tumor progression in intracranially-injected GBM tumors in C57/BL6 mice. Mice weight and organ weights were recorded for both vehicle and BRZ-treated mice to assess toxicity profiles. Results: BRZ exhibited ~300 times more cytotoxicity in GBM cells as compared to TMZ, making it a more potent treatment option. BRZ lead to an increase in acridine orange in a concentration-dependent manner, hinting towards autophagic cell death. b-galactosidase staining assay and confocal microscopy exhibited a dose-dependent increase in b-galactosidase, showcasing a probable cytostatic effect. Expression of autophagic markers such as Atg5, Atg101, LC3A/B, and senescence markers b-galactosidase, p16, and p21 were increased due to BRZ confirming a cytostatic autophagic modulation in GBM cells. Immunoblotting revealed oncogenic modulation due to BRZ wherein Notch-1, Gli-1, Akt, and p-STAT3 were significantly downregulated, as observed in western blotting. Neuroinflammatory genes such as CXCL10, IL6, and ISG15 were downregulated in LPS-stimulated microglia using BRZ in a concentration-dependent manner, hinting towards the potential of BRZ in brain inflammation. BRZ significantly reduced the progression of orthotopic GBM tumors in C57/BL6 mice. There was no significant difference observed in body and organ weights in the vehicle and BRZ-treated mice, hinting toward the safety profile of BRZ. Conclusions and future direction: Our study provides a novel and safer treatment option for GBM in the form of a cytostatic autophagy modulator, BRZ, which also reduces neuroinflammation with the potential to increase patient’s quality of life. In the future, we aim to perform ex vivo analyses of mice brain tumors and perform the neuroinflammation study in GBM mice. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.