Cell death by autophagy: emerging molecular mechanisms and implications for cancer therapy

Autophagy genes and signaling pathways in endometrial decidualization and pregnancy complications

Autophagy is a process that occurs in almost all eukaryotic cells and this process is controlled by several molecular processes. Its biological roles include the provision of energy, the maintenance of cell homeostasis, and the promotion of aberrant cell death. The importance of autophagy in pregnancy is gradually becoming recognized. In literature, it has been indicated that autophagy has three different effects on the onset and maintenance of pregnancy: embryo (embryonic development), feto-maternal immune crosstalk, and maternal (decidualization). In humans, proper decidualization is a major predictor of pregnancy accomplishment and it can be influenced by different factors. This review highlights the genes, pathways, regulation, and function of autophagy in endometrial decidualization and other involved factors in this process.

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

BACKGROUND

Epidermal 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.

METHODS

We 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.

RESULTS

Betulinic 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.

CONCLUSIONS

BA 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.

Let-7a-3p overexpression increases chemosensitivity to carmustine and synergistically promotes autophagy and suppresses cell survival in U87MG glioblastoma cancer cells

In terms of primary brain tumors, glioblastoma is one of the most aggressive and common brain tumors. The high resistance of glioblastoma to chemotherapy has made it vital to find alternative treatments and biological mechanisms to reduce the survival of cancer cells. Given that, the objective of the present research was to explore the potential of let-7a-3p when used in combination with carmustine in human glioblastoma cancer cells. Based on previous studies, the expression of let-7a is downregulated in the U87MG cell line. Let-7a-3p transfected into U87MG glioblastoma cells. Cell viability of the cells was assessed by MTT assay. The apoptotic induction in U87MG cancerous cells was determined through the utilization of DAPI and Annexin V/PI staining techniques. Moreover, the induction of autophagy and cell cycle arrest was evaluated by flow cytometry. Furthermore, cell migration was evaluated by the wound healing assay while colony formation assay was conducted to evaluate colony formation. Also, the expression of the relevant genes was evaluated using qRT-PCR. Transfection of let-7a-3p mimic in U87MG cells increased the expression of the miRNA and also increased the sensitivity of U87MG cells to carmustine. Let-7a-3p and carmustine induced sub-G1 and S phase cell cycle arrest, respectively. Combination treatment of let-7a-3p and carmustine synergistically increased arrested cells and induced apoptosis through regulating involved genes including P53, caspase-3, Bcl-2, and Bax. Combined treatment with let-7a-3p and carmustine also induced autophagy and increased the expression of the ATG5 and Beclin 1 (ATG6). Furthermore, let-7a-3p combined with carmustine inhibited cell migration via decreasing the expression of MMP-2. Moreover, the combination therapy decreased the ability of U87MG to form colonies through downregulating CD-44. In conclusion, our work suggests that combining let-7a-3p replacement therapy with carmustine treatment could be considered a promising strategy in treatment and can increase efficiency of glioblastoma chemotherapy.

AMPKα is active in autophagy of endothelial cells in arsenic-induced vascular endothelial dysfunction by regulating mTORC1/p70S6K/ULK1

Cardiovascular disease (CVD) is the most common cause of death, environmental factors, such as arsenic, playing an important role in the progress of CVD. Vascular endothelial dysfunction (VED) is a crucial early feature for CVD, inorganic arsenic (iAs) can induce autophagy in various cells. However, the role of endothelial autophagy has rarely been studied in VED triggered by arsenic. Total of one hundred and twenty healthy male C57BL/6J mice weighing 18-22 g were randomly divided into an arsenic-exposure group and a control group for 3, 6, 9, and 12 weeks. The results showed that, independent of the exposure period, autophagy markers of p-ATG16L1 levels and Beclin 1 contents in the aortic arch endothelium increased significantly compared with those of the corresponding control group. And different exposure duration decreased NO contents in the serum significantly. Combined with the histological changes that endothelial injury aggravated gradually with the increasing exposure period, suggesting that under exposure to iAs over 9 weeks, VED was remarkably induced, and consistant high levels of endothelial autophagy may play an important role. Additionally, levels of p-AMPKα/AMPKα increased significantly and p-mTORC1/mTORC1 levels decreased remarkably in the aortic arch endothelium. Then, a NaAsO2-induced-VED in vitro model was used to explore the mechanism of arsenic-induced endothelial autophagy. Similarly, p-AMPKα/AMPKα level significantly increased, and p-mTORC1/mTORC1 level remarkably decreased induced by 30 μmol/L NaAsO2 in HUAECs. Further, an AMPK inhibitor (Compound C) pre-treatment prior to arsenic exposure reversed the increased autophagy level, and alleviated the endothelial dysfunction in HUVECs, as shown by the significant increase in the intracellular NO content and the cell vitality. Mechanistically, we revealed that AMPKα is active in autophagy of endothelial cells in arsenic-induced VED by regulating mTORC1/p70S6K/ULK1. The present study provide a new promising target for prevention and control arsenic-associated CVD.

Telomeres as hotspots for innate immunity and inflammation

Aging is marked by the gradual accumulation of deleterious changes that disrupt organ function, creating an altered physiological state that is permissive for the onset of prevalent human diseases. While the exact mechanisms governing aging remain a subject of ongoing research, there are several cellular and molecular hallmarks that contribute to this biological process. This review focuses on two factors, namely telomere dysfunction and inflammation, which have emerged as crucial contributors to the aging process. We aim to discuss the mechanistic connections between these two distinct hallmarks and provide compelling evidence highlighting the loss of telomere protection as a driver of pro-inflammatory states associated with aging. By reevaluating the interplay between telomeres, innate immunity, and inflammation, we present novel perspectives on the etiology of aging and its associated diseases.

Blockade of DDR1/PYK2/ERK signaling suggesting SH2 superbinder as a novel autophagy inhibitor for pancreatic cancer

Pancreatic cancer is highly lethal, of which 90% is pancreatic ductal adenocarcinoma (PDAC), with a 5-year survival rate of less than 12%, lacking effective treatment options and late diagnosis. Furthermore, the tumors show an intense resistance to cytotoxic chemotherapies. As autophagy is elevated in PDAC, targeting the autophagic pathway is regarded as a promising strategy for cancer treatment. Immunofluorescence and transmission electron microscopy were utilized to assess the autophagic flux. Label-free quantitative phosphoproteomics was used to figure out critically altered tyrosine phosphorylation of the proteins. Tumor-bearing mice were used to validate that SH2 TrM-(Arg)9 restrained the growth of tumor cells. SH2 TrM-(Arg)9 inhibited collagen-induced autophagy via blocking the DDR1/PYK2/ERK signaling cascades. SH2 TrM-(Arg)9 improved the sensitivity of PANC-1/GEM cells to gemcitabine (GEM). Inhibition of autophagy by SH2 TrM-(Arg)9 may synergized with chemotherapy and robusted tumor suppression in pancreatic cancer xenografts. SH2 TrM-(Arg)9 could enter into PDAC cells and blockade autophagy through inhibiting DDR1/PYK2/ERK signaling and may be a new treatment strategy for targeted therapy of PDAC.

The iron chelator and OXPHOS inhibitor VLX600 induces mitophagy and an autophagy-dependent type of cell death in glioblastoma cells

Induction of alternative, non-apoptotic cell death programs such as cell-lethal autophagy and mitophagy represent possible strategies to combat glioblastoma (GBM). Here we report that VLX600, a novel iron chelator and oxidative phosphorylation (OXPHOS) inhibitor, induces a caspase-independent type of cell death that is partially rescued in adherent U251 ATG5/7 (autophagy related 5/7) knockout (KO) GBM cells and NCH644 ATG5/7 knockdown (KD) glioma stem-like cells (GSCs), suggesting that VLX600 induces an autophagy-dependent cell death (ADCD) in GBM. This ADCD is accompanied by decreased oxygen consumption, increased expression/mitochondrial localization of BNIP3 (BCL2 interacting protein 3) and BNIP3L (BCL2 interacting protein 3 like), the induction of mitophagy as demonstrated by diminished levels of mitochondrial marker proteins [e.g., COX4I1 (cytochrome c oxidase subunit 4I1)] and the mitoKeima assay as well as increased histone H3 and H4 lysine tri-methylation. Furthermore, the extracellular addition of iron is able to significantly rescue VLX600-induced cell death and mitophagy, pointing out an important role of iron metabolism for GBM cell homeostasis. Interestingly, VLX600 is also able to completely eliminate NCH644 GSC tumors in an organotypic brain slice transplantation model. Our data support the therapeutic concept of ADCD induction in GBM and suggest that VLX600 may be an interesting novel drug candidate for the treatment of this tumor.NEW & NOTEWORTHY Induction of cell-lethal autophagy represents a possible strategy to combat glioblastoma (GBM). Here, we demonstrate that the novel iron chelator and OXPHOS inhibitor VLX600 exerts pronounced tumor cell-killing effects in adherently cultured GBM cells and glioblastoma stem-like cell (GSC) spheroid cultures that depend on the iron-chelating function of VLX600 and on autophagy activation, underscoring the context-dependent role of autophagy in therapy responses. VLX600 represents an interesting novel drug candidate for the treatment of this tumor.

Curcumin induces mitophagy by promoting mitochondrial succinate dehydrogenase activity and sensitizes human papillary thyroid carcinoma BCPAP cells to radioiodine treatment

Thyroid cancer is one of the most common endocrine malignancies. Differentiated thyroid cancer (DTC) treatment is based on the ability of thyroid follicular cells to accumulate radioactive iodide (RAI). DTC generally has a good prognosis. However, tumor dedifferentiation or defect in certain cell death mechanism occurs in a subset of DTC patients, leading to RAI resistance. Therefore, developing novel therapeutic approaches that enhance RAI sensitivity are still warranted. We found that curcumin, an active ingredient in turmeric with anti-cancer properties, rapidly accumulated in the mitochondria of thyroid cancer cells but not normal epithelial cells. Curcumin treatment triggered mitochondrial membrane depolarization, engulfment of mitochondria within autophagosomes and a robust decrease in mitochondrial mass and proteins, indicating that curcumin selectively induced mitophagy in thyroid cancer cells. In addition, curcumin-induced mitophagic cell death and its synergistic cytotoxic effect with radioiodine could be attenuated by autophagy inhibitor, 3-methyladenine (3-MA). Interestingly, the mechanism of mitophagy-inducing potential of curcumin was its unique mitochondria-targeting property, which induced a burst of SDH activity and excessive ROS production. Our data suggest that curcumin induces mitochondrial dysfunction and triggers lethal mitophagy, which synergizes with radioiodine to kill thyroid cancer cells.

Molecular mechanism by which RRM2-inhibitor (cholagogue osalmid) plus bafilomycin A1 cause autophagic cell death in multiple myeloma

Despite significant improvement in the prognosis of multiple myeloma (MM), the disease remains incurable; thus, more effective therapies are required. Ribonucleoside-diphosphate reductase subunit M2 (RRM2) is significantly associated with drug resistance, rapid relapse, and poor prognosis. Previously, we found that 4-hydroxysalicylanilide (osalmid), a specific inhibitor of RRM2, exhibits anti-MM activity in vitro, in vivo, and in human patients; however, the mechanism remains unclear. Osalmid inhibits the translocation of RRM2 to the nucleus and stimulates autophagosome synthesis but inhibits subsequent autophagosome-lysosome fusion. We confirm that RRM2 binds to receptor-interacting protein kinase 3 (RIPK3) and reduces RIPK3, inhibiting autophagosome-lysosome fusion. Interestingly, the combination of osalmid and bafilomycin A1 (an autophagy inhibitor) depletes RIPK3 and aggravates p62 and autophagosome accumulation, leading to autophagic cell death. Combination therapy demonstrates synergistic cytotoxicity both in vitro and in vivo. Therefore, we propose that combining osalmid and bafilomycin A1(BafA1) may have clinical benefits against MM.

Pathological study of proximal tubule mitochondria in diclofenac-induced acute kidney injury model mice

Diclofenac, a non-steroidal anti-inflammatory drug, reportedly targets mitochondria and induces nephrotoxicity via reactive oxygen species. However, there are few detailed reports of pathological analyses of mitochondria and the factors that cause acute kidney injury (AKI) as a result of nephrotoxicity. In this study, we investigated mitochondrial damage in the proximal tubule in AKI mice at 6, 12, and 24 h after administration of diclofenac. Statistical analysis of immunohistochemistry results confirmed that expression of p62 and LC3, which is associated with autophagy, reached a maximum level in the degenerated proximal renal tubule 12 h after diclofenac treatment, with high autophagy activity. Electron microscopy images provided clear evidence that confirmed mitochondrial degeneration and injury as well as autophagy (mitophagy) in mitochondria treated with diclofenac. The purpose of this study was to pathologically characterize both mitochondrial damage in the proximal renal tubules induced by diclofenac and the course of mitophagy to remove the damaged mitochondria. This report provides important information regarding mitochondrial damage in the proximal tubules in diclofenac-induced nephropathy.

Pharmacological Akt and JNK Kinase Inhibitors 10-DEBC and SP600125 Potentiate Anti-Glioblastoma Effect of Menadione and Ascorbic Acid Combination in Human U251 Glioblastoma Cells

Glioblastoma multiforme (GBM) is the most lethal primary brain tumor in adults, characterized by a highly invasive nature and therapy resistance. Combination of menadione and ascorbic acid (AA+MD) exerts strong ROS-mediated anti-GBM activity in vitro. The objective of this study was to improve AA+MD anti-GBM potential by modulating the activity of Akt and c-Jun N-terminal kinase (JNK), molecules with an important role in GBM development. The effects of Akt and JNK modulation on AA+MD toxicity in U251 human glioblastoma cells were assessed by cell viability assays, flow cytometry, RNA interference and plasmid overexpression, and immunoblot analysis. The AA+MD induced severe oxidative stress, an early increase in Akt phosphorylation followed by its strong inhibition, persistent JNK activation, and U251 cell death. Small molecule Akt kinase inhibitor 10-DEBC enhanced, while pharmacological and genetic Akt activation decreased, AA+MD-induced toxicity. The U251 cell death potentiation by 10-DEBC correlated with an increase in the combination-induced autophagic flux and was abolished by genetic autophagy silencing. Additionally, pharmacological JNK inhibitor SP600125 augmented combination toxicity toward U251 cells, an effect linked with increased ROS accumulation. These results indicate that small Akt and JNK kinase inhibitors significantly enhance AA+MD anti-GBM effects by autophagy potentiation and amplifying deleterious ROS levels.

Usenamine A induces apoptosis and autophagic cell death of human hepatoma cells via interference with the Myosin-9/actin-dependent cytoskeleton remodeling

BACKGROUND

Hepatocellular carcinoma (HCC) is a major cause of cancer-associated mortality worldwide. Myosin-9's role in HCC and the anti-HCC effect of the drugs targeting Myosin-9 remain poorly understood so far. Candidate antitumor agents obtained from natural products have attracted worldwide attention. Usenamine A is a novel product, which was first extracted in our laboratory from the lichen Usnea longissima. According to published reports, usenamine A exhibits good antitumor activity, while the mechanisms underlying its antitumor effects remain to be elucidated.

PURPOSE

The present study investigated the anti-hepatoma effect of usenamine A and the underlying molecular mechanisms, along with evaluating the therapeutic potential of targeting Myosin-9 in HCC.

METHODS

The CCK-8, Hoechst staining, and FACS assays were conducted in the present study to investigate how usenamine A affected the growth and apoptosis of human hepatoma cells. Moreover, TEM, acridine orange staining, and immunofluorescence assay were performed to explore the induction of autophagy by usenamine A in human hepatoma cells. The usenamine A-mediated regulation of protein expression in human hepatoma cells was analyzed using immunoblotting. MS analysis, SPR assay, CETSA, and molecular modeling were performed to identify the direct target of usenamine A. Immunofluorescence assay and co-immunoprecipitation assay were conducted to determine whether usenamine A affected the interaction between Myosin-9 and the actin present in human hepatoma cells. In addition, the anti-hepatoma effect of usenamine A was investigated in vivo using a xenograft tumor model and the IHC analysis.

RESULTS

The present study initially revealed that usenamine A could suppress the proliferation of HepG2 and SK-HEP-1 cells (hepatoma cell lines). Furthermore, usenamine A induced cell apoptosis via the activation of caspase-3. In addition, usenamine A enhanced autophagy. Moreover, usenamine A administration could dramatically suppress the carcinogenic ability of HepG2 cells, as evidenced by the nude mouse xenograft tumor model. Importantly, it was initially revealed that Myosin-9 was a direct target of usenamine A. Usenamine A could block cytoskeleton remodeling through the disruption of the interaction between Myosin-9 and actin. Myosin-9 participated in suppressing proliferation while inducing apoptosis and autophagy in response to treatment with usenamine A. In addition, Myosin-9 was revealed as a potential oncogene in HCC.

CONCLUSIONS

Usenamine A was initially revealed to suppress human hepatoma cells growth by interfering with the Myosin-9/actin-dependent cytoskeleton remodeling through the direct targeting of Myosin-9. Myosin-9 is, therefore, a promising candidate target for HCC treatment, while usenamine A may be utilized as a possible anti-HCC therapeutic, particularly in the treatment of HCC with aberrant Myosin-9.

Adapting to hormone-therapy resistance for adopting the right therapeutic strategy in advanced prostate cancer

INTRODUCTION

The androgen/androgen receptor (AR) axis represents a key driver of treatment resistance in prostate cancer (PCa) patients receiving androgen deprivation therapy (ADT) and targeted agents, and a deeper comprehension of resistance mechanisms is fundamental to adopt effective therapeutic strategies.

AREAS COVERED

We review the mechanisms of primary or secondary resistance to hormone therapy (HT) in PCa, especially focusing on available data and emerging evidence.

EXPERT OPINION

First- and second-generation HT resistance has been associated with several AR-dependent and AR-independent mechanisms, ranging from the amplification of the AR gene locus to somatic AR mutations and the intratumoral synthesis of androgens from adrenal steroids and cholesterol. As reported in the current review, the development of novel and effective treatments is needed to personalize anticancer therapies in this setting and to finally improve clinical outcomes in patients with HT resistant disease.

The "Self-eating" of cancer-associated fibroblast: A potential target for cancer

Autophagy helps maintain energy homeostasis and protect cells from stress effects by selectively removing misfolded/polyubiquitylated proteins, lipids, and damaged mitochondria. Cancer-associated fibroblasts (CAFs) are cellular components of tumor microenvironment (TME). Autophagy in CAFs inhibits tumor development in the early stages; however, it has a tumor-promoting effect in advanced stages. In this review, we aimed to summarize the modulators responsible for the induction of autophagy in CAFs, such as hypoxia, nutrient deprivation, mitochondrial stress, and endoplasmic reticulum stress. In addition, we aimed to present autophagy-related signaling pathways in CAFs, and role of autophagy in CAF activation, tumor progression, tumor immune microenvironment. Autophagy in CAFs may be an emerging target for tumor therapy. In summary, autophagy in CAFs is regulated by a variety of modulators and can reshape tumor immune microenvironment, affecting tumor progression and treatment.

Serine hydroxymethyltransferase 2 knockdown induces apoptosis in ccRCC by causing lysosomal membrane permeabilization via metabolic reprogramming

Serine hydroxymethyltransferase 2 (SHMT2) plays an important role in converting serine to glycine and supplying carbon to one-carbon metabolism to sustain cancer cell proliferation. However, the expression, function, and underlying mechanisms of SHMT2 in clear cell renal cell carcinoma (ccRCC) remain largely unknown. In this study, we demonstrated that SHMT2 was upregulated in ccRCC tissues compared with controls and associated with patient survival. SHMT2 knockdown inhibited proliferation, migration, and invasion in ccRCC cells. Overexpression of SHMT2 promoted tumor progression. Mechanistically, SHMT2 depletion disrupted one-carbon metabolism, increased reactive oxygen species (ROS) levels, and decreased ATP levels via metabolic reprogramming, which destroyed cell homeostasis. The SHMT2 knockdown-induced stress activated autophagy. A mass of autophagosomes fused with lysosomes, resulting in lysosomal membrane permeabilization (LMP) and leakage of lysosomal contents into the cytoplasm, which eventually led to apoptosis. Our work reveals that SHMT2 functions as an oncogenic gene to promote ccRCC progression. SHMT2 depletion induces apoptosis by causing LMP through excessive activation of the autophagy-lysosome pathway via metabolic reprogramming.

Cudraflavone B induces human glioblastoma cells apoptosis via ER stress-induced autophagy

BACKGROUND

Glioblastoma (GBM) is the most common malignant intracranial tumor with a low survival rate. However, only few drugs responsible for GBM therpies, hence new drug development for it is highly required. The natural product Cudraflavone B (CUB) has been reported to potentially kill a variety of tumor cells. Currently, its anit-cancer effect on GBM still remains unknown. Herein, we investigated whether CUB could affect the proliferation and apoptosis of GBM cells to show anti-GBM potential.

RESULTS

CUB selectively inhibited cell viability and induced cell apoptosis by activating the endoplasmic reticulum stress (ER stress) related pathway, as well as harnessing the autophagy-related PI3K/mTOR/LC3B signaling pathway. Typical morphological changes of autophagy were also observed in CUB treated cells by microscope and scanning electron microscope (SEM) examination. 4-Phenylbutyric acid (4-PBA), an ER stress inhibitor, restored the CUB-caused alteration in signaling pathway and morphological change.

CONCLUSIONS

Our finding suggests that CUB impaired cell growth and induced cell apoptosis of glioblastoma through ER stress and autophagy-related signaling pathways, and it might be an attractive drug for treatment of GBM.

P16INK4a Regulates ROS-Related Autophagy and CDK4/6-Mediated Proliferation: A New Target of Myocardial Regeneration Therapy

Neonatal mice achieve complete cardiac repair through endogenous myocardial regeneration after apical resection (AR), but this capacity is rapidly lost 7 days after birth. As an upstream inhibitor of cyclin-dependent kinase 4/6- (CDK4/6-) mediated cell cycle activity, p16^INK4a is widely involved in regulating tumor and senescence. Given that p16^INK4a had a significant negative regulation on cell proliferation, targeting cardiomyocytes (CMs) to inhibit p16^INK4a seems to be a promising attempt at myocardial regeneration therapy. The p16^INK4a expression was upregulated during perimyocardial regeneration time. Knockdown of p16^INK4a stimulated CM proliferation, while p16^INK4a overexpression had the opposite effect. In addition, p16^INK4a knockdown prolonged the proliferation time window of newborn myocardium. And p16^INK4a overexpression inhibited cell cycle activity and deteriorated myocardial regeneration after AR. The quantitative proteomic analysis showed that p16^INK4a knockdown mediated the cell cycle progression and intervened in energy metabolism homeostasis. Mechanistically, overexpression of p16^INK4a causes abnormal accumulation of reactive oxygen species (ROS) to induce autophagy, while scavenging ROS with N-acetylcysteine can alleviate autophagy and regulate p16^INK4a, CDK4/6, and CyclinD1 in a covering manner. And the effect of inhibiting the proliferation of p16^INK4a-activated CMs was significantly blocked by the CDK4/6 inhibitor Palbociclib. In summary, p16^INK4a regulated CM proliferation progression through CDK4/6 and ROS-related autophagy to jointly affect myocardial regeneration repair. Our study revealed that p16^INK4a might be a potential therapeutic target for myocardial regeneration after injury.

3'-epi-12β-hydroxyfroside-mediated autophagy degradation of RIPK1/RIPK3 necrosomes leads to anergy of immunogenic cell death in triple-negative breast cancer cells

Increasing studies have suggested that some cardiac glycosides, such as conventional digoxin (DIG) and digitoxin, can induce immunogenic cell death (ICD) in various tumors. We previously found that 3'-epi-12β-hydroxyfroside (HyFS), a novel cardenolide compound isolated by our group, could induce cytoprotective autophagy through inactivation of the Akt/mTOR pathway. However, whether HyFS can induce ICD remains unknown. In this study, we extend our work to further investigate whether HyFS could induce both autophagy and ICD, and we investigated the relationship between autophagy and ICD in three TNBC cell lines. Unexpectedly, compared to DIG, we found that HyFS could induce complete autophagy flux but not ICD in three human triple-negative breast cancer (TNBC) cell lines and one murine TNBC model. Inhibition of HyFS-induced autophagy resulted in the production of ICD in TNBC MDA-MB-231, MDA-MB-436, and HCC38 cells. A further mechanism study showed that formation of RIPK1/RIPK3 necrosomes was necessary for ICD induction in DIG-treated TNBC cells, while HyFS treatment led to receptor-interacting serine-threonine kinase (RIPK)1/3 necrosome degradation via an autophagy process. Additionally, inhibition of HyFS-induced autophagy by the autophagy inhibitor chloroquine resulted in the reoccurrence of ICD and reversion of the tumor microenvironment, leading to more significant antitumor effects in immunocompetent mice than in immunodeficient mice. These findings indicate that HyFS-mediated autophagic degradation of RIPK1/RIPK3 necrosomes leads to inactivation of ICD in TNBC cells. Moreover, combined treatment with HyFS and an autophagy inhibitor may enhance the antitumor activities, suggesting an alternative therapeutic for TNBC treatment.

Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl) homoserine lactone induces calcium signaling-dependent crosstalk between autophagy and apoptosis in human macrophages

N-(3-oxododecanoyl) homoserine lactone (3oc) is a Pseudomonas aeruginosa secreted quorum-sensing signal molecule playing a crucial role in regulating quorum-sensing (QS) dependent biofilm formation and secretion of virulence factors. In addition to regulating quorum sensing, 3oc also plays an immunomodulatory role in the host by triggering regulated cell death in immune cells. The molecular mechanisms of 3oc in modulating macrophage pathologies are still unclear. In this study, we hypothesized the novel 3oc mediated crosstalk between autophagy and apoptosis at the interphase of calcium signaling in human macrophages. The study showed that 3oc induces mitochondrial dysfunction and apoptosis in macrophages through elevating cytosolic Ca⁺² ([Ca⁺²]_cyt) levels. Pre-treatment with the calcium-specific chelator BAPTA-AM effectively abrogated 3oc-induced apoptotic events, like mitochondrial ROS generation (mROS), mitochondrial membrane potential (MMP) drop, and phosphatidylserine (PS) exposure. The study also showed that 3oc induces autophagy, as assessed by the accumulation of autophagic vacuoles, induction of lysosomal biogenesis, upregulation of autophagy genes (LC3, BECLIN 1, STX17, PINK1, and TFEB), autophagosomes formation, and LC3 lipidation. Mechanistically, our study proved that 3oc-induced autophagy was [Ca⁺²]_cyt dependent as BAPTA-AM pre-treatment reduced autophagosome formation. Furthermore, inhibiting autophagy with chloroquine attenuated 3oc-induced apoptosis, while autophagy induction with rapamycin aggravated cell death, suggesting autophagy plays a role in cell death in 3oc-treated macrophages. In conclusion, our findings indicate that 3oc activates a multifaceted death signaling by activating autophagy and apoptosis through Ca⁺² signaling, and we propose pharmacological modulation of Ca⁺² signaling may act as a combinatorial therapeutic intervention in patients with Pseudomonas aeruginosa-associated infections.

Identification of an autophagy-related 12-lncRNA signature and evaluation of NFYC-AS1 as a pro-cancer factor in lung adenocarcinoma

Objective: To develop an autophagy-related lncRNA-based risk signature and corresponding nomogram to predict overall survival (OS) for LUAD patients and investigate the possible meaning of screened factors.

Methods: Differentially expressed lncRNAs and autophagy genes were screened between normal and LUAD tumor samples from the TCGA LUAD dataset. Univariate and multivariate Cox regression analyses were performed to construct the lncRNA-based risk signature and nomogram incorporating clinical information. Then, the accuracy and sensitivity were confirmed by the AUC of ROC curves in both training and validation cohorts. qPCR, immunoblot, shRNA, and ectopic expression were used to verify the positive regulation of NFYC-AS1 on BIRC6. CCK-8, immunofluorescence, and flow cytometry were used to confirm the influence of NFYC-AS1 on cell proliferation, autophagy, and apoptosis via BIRC6.

Results: A 12-lncRNA risk signature and a nomogram combining related clinical information were constructed. Furthermore, the abnormal increase of NFYC-AS1 may promote LUAD progression through the autophagy-related gene BIRC6.

Conclusion: 12-lncRNA signature may function as a predictive marker for LUAD patients, and NFYC-AS1 along with BIRC6 may function as carcinogenic factors in a combinatorial manner.

Artesunate Inhibits the Cell Growth in Colorectal Cancer by Promoting ROS-Dependent Cell Senescence and Autophagy

Although artesunate has been reported to be a promising candidate for colorectal cancer (CRC) treatment, the underlying mechanisms and molecular targets of artesunate are yet to be explored. Here, we report that artesunate acts as a senescence and autophagy inducer to exert its inhibitory effect on CRC in a reactive oxygen species (ROS)-dependent manner. In SW480 and HCT116 cells, artesunate treatment led to mitochondrial dysfunction, drastically promoted mitochondrial ROS generation, and consequently inhibited cell proliferation by causing cell cycle arrest at G0/G1 phase as well as subsequent p16- and p21-mediated cell senescence. Senescent cells underwent endoplasmic reticulum stress (ERS), and the unfolded protein response (UPR) was activated via IRE1α signaling, with upregulated BIP, IRE1α, phosphorylated IRE1α (p-IRE1α), CHOP, and DR5. Further experiments revealed that autophagy was induced by artesunate treatment due to oxidative stress and ER stress. In contrast, N-Acetylcysteine (NAC, an ROS scavenger) and 3-Methyladenine (3-MA, an autophagy inhibitor) restored cell viability and attenuated autophagy in artesunate-treated cells. Furthermore, cellular free Ca²⁺ levels were increased and could be repressed by NAC, 3-MA, and GSK2350168 (an IRE1α inhibitor). In vivo, artesunate administration reduced the growth of CT26 cell-derived tumors in BALB/c mice. Ki67 and cyclin D1 expression was downregulated in tumor tissue, while p16, p21, p-IRE1α, and LC3B expression was upregulated. Taken together, artesunate induces senescence and autophagy to inhibit cell proliferation in colorectal cancer by promoting excessive ROS generation.

A review on therapeutical potential of paeonol in atherosclerosis

The morbidity and mortality of atherosclerotic cardiovascular disease (ASCVD) is increasing year by year. Cortex Moutan is a traditional Chinese medicinal herb that has been widely used for thousands of years to treat a wide variety of diseases in Eastern countries due to its heat-clearing and detoxifying effects. Paeonol is a bioactive monomer extracted from Cortex Moutan, which has anti-atherosclerotic effects. In this article, we reviewed the pharmacological effects of paeonol against experimental atherosclerosis, as well as its protective effects on vascular endothelial cells, smooth muscle cells, macrophages, platelets, and other important cell types. The pleiotropic effects of paeonol in atherosclerosis suggest that it can be a promising therapeutic agent for atherosclerosis and its complications. Large-scale randomized clinical trials are warranted to elucidate whether paeonol are effective in patients with ASCVD.

Lomitapide, a cholesterol-lowering drug, is an anticancer agent that induces autophagic cell death via inhibiting mTOR

Autophagy is a biological process that maintains cellular homeostasis and regulates the internal cellular environment. Hyperactivating autophagy to trigger cell death has been a suggested therapeutic strategy for cancer treatment. Mechanistic target of rapamycin (mTOR) is a crucial protein kinase that regulates autophagy; therefore, using a structure-based virtual screen analysis, we identified lomitapide, a cholesterol-lowering drug, as a potential mTOR complex 1 (mTORC1) inhibitor. Our results showed that lomitapide directly inhibits mTORC1 in vitro and induces autophagy-dependent cancer cell death by decreasing mTOR signaling, thereby inhibiting the downstream events associated with increased LC3 conversion in various cancer cells (e.g., HCT116 colorectal cancer cells) and tumor xenografts. Lomitapide also significantly suppresses the growth and viability along with elevated autophagy in patient-derived colorectal cancer organoids. Furthermore, a combination of lomitapide and immune checkpoint blocking antibodies synergistically inhibits tumor growth in murine MC38 or B16-F10 preclinical syngeneic tumor models. These results elucidate the direct, tumor-relevant immune-potentiating benefits of mTORC1 inhibition by lomitapide, which complement the current immune checkpoint blockade. This study highlights the potential repurposing of lomitapide as a new therapeutic option for cancer treatment.

A Tale of Two Cancers: A Current Concise Overview of Breast and Prostate Cancer

Simple Summary

Breast and prostate cancers are serious public health issues that create considerable burden to both people and healthcare systems worldwide. Cancer is a heterogeneous disease influenced by numerous components, and its diverse intricate pathology challenges disease prevention, diagnosis, treatment, and survival. Although recent statistics suggest improvements in cancer diagnosis and treatment, many challenges remain before cancers are curable. This review presents relevant summarized information related to breast and prostate cancer.

Abstract

Cancer is a global issue, and it is expected to have a major impact on our continuing global health crisis. As populations age, we see an increased incidence in cancer rates, but considerable variation is observed in survival rates across different geographical regions and cancer types. Both breast and prostate cancer are leading causes of morbidity and mortality worldwide. Although cancer statistics indicate improvements in some areas of breast and prostate cancer prevention, diagnosis, and treatment, such statistics clearly convey the need for improvements in our understanding of the disease, risk factors, and interventions to improve life span and quality of life for all patients, and hopefully to effect a cure for people living in developed and developing countries. This concise review compiles the current information on statistics, pathophysiology, risk factors, and treatments associated with breast and prostate cancer.

Patulin Induces Acute Kidney Injury in Mice through Autophagy-Ferroptosis Pathway

Patulin (PAT) is a common mycotoxin, widely found in cereals, seafood, nuts, and especially in fruits and their products. Exposure to this mycotoxin has been reported to induce kidney injury. However, the possible mechanism remains unclear. In our study, short-term high-dose intake of PAT caused acute kidney injury (AKI) in mice. We performed high-throughput transcriptional sequencing to identify differentially expressed genes (DEGs) between the treatment and control groups. The ferroptosis signaling pathway had the highest enrichment, suggesting ferroptosis is involved in PAT-induced AKI. Further, the existence of ferroptosis and autophagy was confirmed by observing the changes of mitochondria morphology and the formation of autophagosomes by electron microscopy. And the expression of solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase 4 (GPX4), p62, nuclear receptor coactivator 4 (NCOA4), and ferritin heavy chain 1 (FTH1) were downregulated, whereas acyl-CoA synthase long-chain family member 4 (ACSL4), transferrin (TF), LC3, and ferritin light chain (FTL) expression were upregulated in PAT-exposed mice. These results suggested autophagy-dependent ferroptosis occurred in the animal model. This view has also been confirmed in the human renal tubular epithelial cell (HKC) experiments. Autophagy inhibitor 3-methyladenine (3MA) attenuated PAT-induced ferroptosis and the iron contents in HKC cells. Simultaneous autophagy-dependent ferroptosis can be inhibited by ferroptosis inhibitors ferrostatin-1 (Fer-1) and desferrioxamine (DFO). In general, this study provides a new perspective for exploring the new mechanism of acute kidney injury caused by PAT.

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

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Theabrownins Produced via Chemical Oxidation of Tea Polyphenols Inhibit Human Lung Cancer Cells in vivo and in vitro by Suppressing the PI3K/AKT/mTOR Pathway Activation and Promoting Autophagy

During the fermentation of dark tea, theabrownins (TBs), carbohydrates, and other substances get irreversibly complex. Recent research on the biological activity of TBs is not based on free TBs. In the present study, some brown polyphenol oxidized polymers, the generalized TBs (TBs-C), were prepared via alkali oxidation from tea polyphenols (TP). We also investigated the inhibitory mechanism of TBs-C on non-small-cell-lung cancer (NSCLC). TBs-C demonstrated a stronger inhibition than TP on the NSCLC cell lines A549, H2030, HCC827, H1975, and PC9. Next, A549 and H2030 cell lines were selected as subjects to explore this mechanism. TBs-C was found to inhibit proliferation, promote apoptosis, and induce G1 cell-cycle arrest in the cells. In addition, TBs-C increased autophagic flux, which in turn promoted the death of lung cancer cells. Moreover, TBs-C suppressed the PI3K/AKT/mTOR pathway activation, promoted autophagy, and increased the expression of p21 downstream of AKT, which resulted in G1 cell-cycle arrest. In xenotransplanted NSCLC nude mice derived from A549 cells, TBs-C could significantly suppress tumor growth by inhibiting the PI3K/AKT/mTOR pathway without causing hepatotoxicity, brain toxicity, or nephrotoxicity. We believe that our present findings would facilitate advancement in the research and industrialization of TBs.

F-box protein FBXO41 plays vital role in arsenic trioxide-mediated autophagic death of cancer cells

Arsenic trioxide (ATO), a potent anti-neoplastic drug, is known to prevent cancer cell growth through induction of autophagic cell death. However, importance of cellular factors in ATO-mediated autophagic cell death is poorly understood. In this study, using biochemical and immunofluorescence techniques, we show that F-box protein FBXO41 plays a critical role in anti-proliferative activity of ATO. Our study reveals the importance of FBXO41 in induction of autophagic death of cancer cells by ATO. Further, we show that the autophagic cell death induced by FBXO41 is distinct and independent of apoptosis and necrosis, showing that FBXO41 may play vital role in inducing autophagic death of apoptosis resistant cancer cells. Overall, our study elucidates the importance of FBXO41 in ATO induced autophagic cell death to prevent cancer progression, which could be explored to develop promising cancer therapeutic strategy.

In search of autophagy biomarkers in breast cancer: Receptor status and drug agnostic transcriptional changes during autophagy flux in cell lines

Autophagy drives drug resistance and drug-induced cancer cell cytotoxicity. Targeting the autophagy process could greatly improve chemotherapy outcomes. The discovery of specific inhibitors or activators has been hindered by challenges with reliably measuring autophagy levels in a clinical setting. We investigated drug-induced autophagy in breast cancer cell lines with differing ER/PR/Her2 receptor status by exposing them to known but divergent autophagy inducers each with a unique molecular target, tamoxifen, trastuzumab, bortezomib or rapamycin. Differential gene expression analysis from total RNA extracted during the earliest sign of autophagy flux showed both cell- and drug-specific changes. We analyzed the list of differentially expressed genes to find a common, cell- and drug-agnostic autophagy signature. Twelve mRNAs were significantly modulated by all the drugs and 11 were orthogonally verified with Q-RT-PCR (Klhl24, Hbp1, Crebrf, Ypel2, Fbxo32, Gdf15, Cdc25a, Ddit4, Psat1, Cd22, Ypel3). The drug agnostic mRNA signature was similarly induced by a mitochondrially targeted agent, MitoQ. In-silico analysis on the KM-plotter cancer database showed that the levels of these mRNAs are detectable in human samples and associated with breast cancer prognosis outcomes of Relapse-Free Survival in all patients (RSF), Overall Survival in all patients (OS), and Relapse-Free Survival in ER⁺ Patients (RSF ER⁺). High levels of Klhl24, Hbp1, Crebrf, Ypel2, CD22 and Ypel3 were correlated with better outcomes, whereas lower levels of Gdf15, Cdc25a, Ddit4 and Psat1 were associated with better prognosis in breast cancer patients. This gene signature uncovers candidate autophagy biomarkers that could be tested during preclinical and clinical studies to monitor the autophagy process.

The regulation, function, and role of lipophagy, a form of selective autophagy, in metabolic disorders

Autophagy is a conserved method of quality control in which cytoplasmic contents are degraded via lysosomes. Lipophagy, a form of selective autophagy and a novel type of lipid metabolism, has recently received much attention. Lipophagy is defined as the autophagic degradation of intracellular lipid droplets (LDs). Although much remains unknown, lipophagy appears to play a significant role in many organisms, cell types, metabolic states, and diseases. It participates in the regulation of intracellular lipid storage, intracellular free lipid levels (e.g., fatty acids), and energy balance. However, it remains unclear how intracellular lipids regulate autophagy. Impaired lipophagy can cause cells to become sensitive to death stimuli and may be responsible for the onset of a variety of diseases, including nonalcoholic fatty liver disease and metabolic syndrome. Like autophagy, the role of lipophagy in cancer is poorly understood, although analysis of specific autophagy receptors has helped to expand the diversity of chemotherapeutic targets. These studies have stimulated increasing interest in the role of lipophagy in the pathogenesis and treatment of cancer and other human diseases.

New insights into the role of melatonin in diabetic cardiomyopathy

Diabetic cardiovascular complications and impaired cardiac function are considered to be the main causes of death in diabetic patients worldwide, especially patients with type 2 diabetes mellitus (T2DM). An increasing number of studies have shown that melatonin, as the main product secreted by the pineal gland, plays a vital role in the occurrence and development of diabetes. Melatonin improves myocardial cell metabolism, reduces vascular endothelial cell death, reverses microcirculation disorders, reduces myocardial fibrosis, reduces oxidative and endoplasmic reticulum stress, regulates cell autophagy and apoptosis, and improves mitochondrial function, all of which are the characteristics of diabetic cardiomyopathy (DCM). This review focuses on the role of melatonin in DCM. We also discuss new molecular findings that might facilitate a better understanding of the underlying mechanism. Finally, we propose potential new therapeutic strategies for patients with T2DM.

A natural derivative from ethnomedicinal mushroom potentiates apoptosis, autophagy and attenuates cell migration, via fine tuning the Akt signaling in human lung adenocarcinoma cells (A549)

Although comprehensive exertions have been made in late decades for treating advanced lung cancer with inclusive therapies but efficient anti-lung cancer therapeutics are statically inadequate in the clinics. Hence, compelling novel anti-lung cancer drugs are considerably desired. This backdrop enticed us to unveil anticancer efficacy of astrakurkurol, derivative of wild edible mushroom against lung cancer, whose effects have not yet been described. Mechanistic analysis disclosed that sensitizing effect of astrakurkurol is due to cell cycle arrest at G0/G1 phase, increased level of Fas, FADD, decreased ratio of Bax/Bcl-2, and increased cleaved form of caspase 9, 8, and 3. Apart from the induction of apoptosis, it was demonstrated for the first time that astrakurkurol induced an autophagic response as evidenced by the development of acidic vesicular organelles (AVOs) with up-regulation of beclin-1, Atg7, and downregulated p62. Apoptosis and autophagy can be sparked by the same stimuli, which was as evident from the astrakurkurol-induced inactivation of PI3K/AKT signaling. The thorough scanning of the mechanism of crosstalk between apoptosis and autophagy is requisite for prosperous anticancer remedy. Triterpenoid has evidently intensified cytotoxicity, induced apoptosis and autophagy on A549 cells. Besides astrakurkurol could also curb migration and regress the size of tumor in ex ovo xenograft model. All these findings put forth astrakurkurol as a convincing novel anti-cancer agent, for scrutinizing the lung cancer therapies and as a robust contender for future in vitro and in vivo analysis.

Vorinostat in autophagic cell death: A critical insight into autophagy-mediated, -associated and -dependent cell death for cancer prevention

Histone deacetylases (HDACs) inhibit the acetylation of crucial autophagy genes, thereby deregulating autophagy and autophagic cell death (ACD) and facilitating cancer cell survival. Vorinostat, a broad-spectrum pan-HDAC inhibitor, inhibits the deacetylation of key autophagic markers and thus interferes with ACD. Vorinostat-regulated ACD can have an autophagy-mediated, -associated or -dependent mechanism depending on the involvement of apoptosis. Molecular insights revealed that hyperactivation of the PIK3C3/VPS34-BECN1 complex increases lysosomal disparity and enhances mitophagy. These changes are followed by reduced mitochondrial biogenesis and by secondary signals that enable superactivated, nonselective or bulk autophagy, leading to ACD. Although the evidence is limited, this review focuses on molecular insights into vorinostat-regulated ACD and describes critical concepts for clinical translation.

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

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

Self-assembled ruthenium and osmium nanosystems display a potent anticancer profile by interfering with metabolic activity

Amphiphilic ruthenium and osmium complexes auto-assemble to nanosystems that poison mitochondria and show highly promising in vitro and in vivo anticancer activity.

Esterase D stabilizes FKBP25 to suppress mTORC1

Background

Esterase D (ESD) is a nonspecific esterase that detoxifies formaldehyde. Many reports have stated that ESD activity is associated with a variety of physiological and pathological processes. However, the detailed signaling pathway of ESD remains poorly understood.

Methods

Considering the advantages of the small chemical molecule, our recent work demonstrated that 4-chloro-2-(5-phenyl-1-(pyridin-2-yl)-4,5-dihydro-1H-pyrazol-3-yl) phenol (FPD5) activates ESD, and will be a good tool for studying ESD further. Firstly, we determined the interaction between ESD and FK506 binding protein 25 (FKBP25) by yeast two-hybrid assay and co-immunoprecipitation (CO-IP) and analyzed the phosphorylation levels of mTORC1, P70S6K and 4EBP1 by western blot. Furthermore, we used the sulforhodamine B (SRB) and chick chorioallantoic membrane (CAM) assay to analyze cell viability in vitro and in vivo after treatment with ESD activator FPD5.

Results

We screened FKBP25 as a candidate protein to interact with ESD by yeast two-hybrid assay. Then we verified the interaction between ESD and endogenous FKBP25 or ectopically expressed GFP-FKBP25 by CO-IP. Moreover, the N-terminus (1–90 aa) domain of FKBP25 served as the crucial element for their interaction. More importantly, ESD reduced the K48-linked poly-ubiquitin chains of FKBP25 and thus stabilized cytoplasmic FKBP25. ESD also promoted FKBP25 to bind more mTORC1, suppressing the activity of mTORC1. In addition, ESD suppressed tumor cell growth in vitro and in vivo through autophagy.

Conclusions

These findings provide novel evidence for elucidating the molecular mechanism of ESD and ubiquitination of FKBP25 to regulate autophagy and cancer cell growth. The ESD/FKBP25/mTORC1 signaling pathway is involved in inhibiting tumor cell growth via regulating autophagy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-021-00297-2.

Grape Seed Proanthocyanidin Ameliorates FB1-Induced Meiotic Defects in Porcine Oocytes

Fumonisin B₁ (FB₁), as the most prevalent and toxic fumonisin, poses a health threat to humans and animals. The cytotoxicity of FB₁ is closely related to oxidative stress and apoptosis. The purpose of this study is to explore whether Grape seed proanthocyanidin (GSP), a natural antioxidant, could alleviate the meiotic maturation defects of oocytes caused by FB₁ exposure. Porcine cumulus oocyte complexes (COCs) were treated with 30 μM FB₁ alone or cotreated with 100, 200 and 300 μM GSP during in vitro maturation for 44 h. The results show that 200 μM GSP cotreatment observably ameliorated the toxic effects of FB₁ exposure, showing to be promoting first polar body extrusion and improving the subsequent cleavage rate and blastocyst development rate. Moreover, 200 μM GSP cotreatment restored cell cycle progression, reduced the proportion of aberrant spindles, improved actin distribution and protected mitochondrial function in FB₁-exposed oocytes. Furthermore, reactive oxygen species (ROS) generation was significantly decreased and the mRNA levels of CAT, SOD2 and GSH-PX were obviously increased in the 200 μM GSP cotreatment group. Notably, the incidence of early apoptosis and autophagy level were also significantly decreased after GSP cotreatment and the mRNA expression levels of BAX, CASPASE3, LC3 and ATG5 were markedly decreased, whereas BCL2 and mTOR were observably increased in the oocytes after GSP cotreatment. Together, these results indicate that GSP could exert significant preventive effects on FB₁-induced oocyte defects by ameliorating oxidative stress through repairing mitochondrial dysfunction.

Podophyllotoxin-combined 5-aminolevulinic acid photodynamic therapy significantly promotes HR-HPV-infected cell death

BACKGROUND

Human papillomavirus (HPV) infection and related diseases are difficult clinical challenges. The efficacy of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) in treating condyloma acuminata is remarkable, with high virus clearance and low recurrence rates. Podophyllotoxin (POD) is the first-line drug with a significant therapeutic effect on condyloma acuminata. However, no studies have determined whether POD-combined ALA-PDT improves high-risk (HR)-HPV-infected cell killing. We aimed to investigate whether POD-combined ALA-PDT could promote HPV-infected cell death more effectively than the single treatment and explore the underlying mechanism.

METHODS

In HeLa and SiHa cells, flow cytometry, EdU assay and LDH release test were used to detect apoptosis, cell proliferation change and necrosis, respectively. To investigate whether the combined therapy might activate apoptosis and induce endoplasmic reticulum (ER) stress, flow cytometry was used to determine intracellular levels of ROS and calcium, and Western blotting was used to determine the expression of related proteins. Mitochondrial membrane depolarization was detected by JC-1 assay. Immunofluorescence staining and Western blotting were used to detect the activation of autophagy.

RESULTS

Podophyllotoxin -combined ALA-PDT inhibited the proliferation and promoted apoptosis and necrosis more effectively than the single treatment at the same intensity and concentration. The activation of the caspase-dependent apoptosis pathway, ER stress and autophagy was more substantial in POD-combined ALA-PDT than with single treatments.

CONCLUSION

Podophyllotoxin -combined ALA-PDT effectively promoted cell death through several pathways in HeLa and SiHa cells. This combination might be a promising therapeutic strategy for the HR-HPV infection.

Autophagy activation, lipotoxicity and lysosomal membrane permeabilization synergize to promote pimozide- and loperamide-induced glioma cell death

Increasing evidence suggests that induction of lethal macroautophagy/autophagy carries potential significance for the treatment of glioblastoma (GBM). In continuation of previous work, we demonstrate that pimozide and loperamide trigger an ATG5- and ATG7 (autophagy related 5 and 7)-dependent type of cell death that is significantly reduced with cathepsin inhibitors and the lipid reactive oxygen species (ROS) scavenger α-tocopherol in MZ-54 GBM cells. Global proteomic analysis after treatment with both drugs also revealed an increase of proteins related to lipid and cholesterol metabolic processes. These changes were accompanied by a massive accumulation of cholesterol and other lipids in the lysosomal compartment, indicative of impaired lipid transport/degradation. In line with these observations, pimozide and loperamide treatment were associated with a pronounced increase of bioactive sphingolipids including ceramides, glucosylceramides and sphingoid bases measured by targeted lipidomic analysis. Furthermore, pimozide and loperamide inhibited the activity of SMPD1/ASM (sphingomyelin phosphodiesterase 1) and promoted induction of lysosomal membrane permeabilization (LMP), as well as release of CTSB (cathepsin B) into the cytosol in MZ-54 wild-type (WT) cells. Whereas LMP and cell death were significantly attenuated in ATG5 and ATG7 knockout (KO) cells, both events were enhanced by depletion of the lysophagy receptor VCP (valosin containing protein), supporting a pro-survival function of lysophagy under these conditions. Collectively, our data suggest that pimozide and loperamide-driven autophagy and lipotoxicity synergize to induce LMP and cell death. The results also support the notion that simultaneous overactivation of autophagy and induction of LMP represents a promising approach for the treatment of GBM.Abbreviations: ACD: autophagic cell death; AKT1: AKT serine/threonine kinase 1; ATG5: autophagy related 5; ATG7: autophagy related 7; ATG14: autophagy related 14; CERS1: ceramide synthase 1; CTSB: cathepsin B; CYBB/NOX2: cytochrome b-245 beta chain; ER: endoplasmatic reticulum; FBS: fetal bovine serum; GBM: glioblastoma; GO: gene ontology; HTR7/5-HT7: 5-hydroxytryptamine receptor 7; KD: knockdown; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LAP: LC3-associated phagocytosis; LMP: lysosomal membrane permeabilization; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; RB1CC1: RB1 inducible coiled-coil 1; ROS: reactive oxygen species; RPS6: ribosomal protein S6; SMPD1/ASM: sphingomyelin phosphodiesterase 1; VCP/p97: valosin containing protein; WT: wild-type.

Reactive Oxygen Species Mediate 6c-Induced Mitochondrial and Lysosomal Dysfunction, Autophagic Cell Death, and DNA Damage in Hepatocellular Carcinoma

Increasing the level of reactive oxygen species (ROS) in cancer cells has been suggested as a viable approach to cancer therapy. Our previous study has demonstrated that mitochondria-targeted flavone-naphthalimide-polyamine conjugate 6c elevates the level of ROS in cancer cells. However, the detailed role of ROS in 6c-treated cancer cells is not clearly stated. The biological effects and in-depth mechanisms of 6c in cancer cells need to be further investigated. In this study, we confirmed that mitochondria are the main source of 6c-induced ROS, as demonstrated by an increase in 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) and MitoSox fluorescence. Compound 6c-induced mitochondrial ROS caused mitochondrial dysfunction and lysosomal destabilization confirmed by absolute quantitation (iTRAQ)-based comparative proteomics. Compound 6c-induced metabolic pathway dysfunction and lysosomal destabilization was attenuated by N-acetyl-L-cysteine (NAC). iTRAQ-based comparative proteomics showed that ROS regulated the expression of 6c-mediated proteins, and treatment with 6c promoted the formation of autophagosomes depending on ROS. Compound 6c-induced DNA damage was characterized by comet assay, p53 phosphorylation, and γH2A.X, which was diminished by pretreatment with NAC. Compound 6c-induced cell death was partially reversed by 3-methyladenine (3-MA), bafilomycin (BAF) A1, and NAC, respectively. Taken together, the data obtained in our study highlighted the involvement of mitochondrial ROS in 6c-induced autophagic cell death, mitochondrial and lysosomal dysfunction, and DNA damage.

Understanding the Radiobiology of Vestibular Schwannomas to Overcome Radiation Resistance

Vestibular schwannomas (VS) are benign tumors arising from cranial nerve VIII that account for 8-10% of all intracranial tumors and are the most common tumors of the cerebellopontine angle. These tumors are typically managed with observation, radiation therapy, or microsurgical resection. Of the VS that are irradiated, there is a subset of tumors that are radioresistant and continue to grow; the mechanisms behind this phenomenon are not fully understood. In this review, the authors summarize how radiation causes cellular and DNA injury that can activate (1) checkpoints in the cell cycle to initiate cell cycle arrest and DNA repair and (2) key events that lead to cell death. In addition, we discuss the current knowledge of VS radiobiology and how it may contribute to clinical outcomes. A better understanding of VS radiobiology can help optimize existing treatment protocols and lead to new therapies to overcome radioresistance.

Retinal degeneration in mice lacking the cyclic nucleotide-gated channel subunit CNGA1

Cyclic nucleotide-gated (CNG) channels are important mediators in the transduction pathways of rod and cone photoreceptors. Native CNG channels are heterotetramers composed of homologous A and B subunits. Biallelic mutations in CNGA1 or CNGB1 genes result in autosomal recessive retinitis pigmentosa (RP). To investigate the pathogenic mechanism of CNG channel-associated retinal degeneration, we developed a mouse model of CNGA1 knock-out using CRISPR/Cas9 technology. We observed progressive retinal thinning and a concomitant functional deficit in vivo as typical phenotypes for RP. Immunofluorescence and TUNEL staining showed progressive degeneration in rods and cones. Moreover, microglial activation and oxidative stress damage occurred in parallel. RNA-sequencing analysis of the retinae suggested down-regulated synaptic transmission and phototransduction as early as 9 days postnatal, possibly inducing later photoreceptor degeneration. In addition, the down-regulated PI3K-AKT-mTOR pathway indicated upregulation of autophagic process, and chaperone-mediated autophagy was further shown to coincide with the time course of photoreceptor death. Taken together, our studies add to a growing body of research exploring the mechanisms of photoreceptor death during RP progression and provide a novel CNGA1 knockout mouse model for potential development of therapies.

Autophagy is a major metabolic regulator involved in cancer therapy resistance

Autophagy sustains cellular homeostasis and metabolism in numerous diseases. By regulating cancer metabolism, both tumor and microenvironmental autophagy promote tumor growth. However, autophagy can support cancer progression through other biological functions such as immune response regulation or cytokine/growth factor secretion. Moreover, autophagy is induced in numerous tumor types as a resistance mechanism following therapy, highlighting autophagy inhibition as a promising target for anti-cancer therapy. Thus, better understanding the mechanisms involved in tumor growth and resistance regulation through autophagy, which are not fully understood, will provide insights into patient treatment.

The Synergistic Effects of Celastrol in combination with Tamoxifen on Apoptosis and Autophagy in MCF-7 Cells

Breast cancer is one of the most common cancers among females and is associated with high mortality and morbidity rates. Several studies have demonstrated that combination treatments with natural products and tamoxifen can improve the sensitivity and cytotoxicity of oestrogen-positive breast cancer cells in response to tamoxifen. Celastrol, a triterpene from traditional Chinese medicine, has been proven to exert significant anticancer effects on various cancers. Our study is aimed at exploring the interactive antitumour effects of celastrol combined with tamoxifen and the potential underlying anticancer mechanisms in MCF-7 cells. The results from MTT assays, isobolographic analyses, and clonogenic cell survival assays revealed that a combination of celastrol and tamoxifen exerted synergistic cytotoxic effects in MCF-7 cells. The results from Annexin V/PI staining and flow cytometry analysis suggested that celastrol enhanced tamoxifen-mediated apoptosis. In addition, exposure to a combination of celastrol and tamoxifen inhibited cell proliferation by causing G1 phase cell cycle arrest. Moreover, the distribution of LC3 was monitored by immunofluorescence, and the changes in the LC3II and P62 levels detected by western blot analysis suggested that celastrol in combination with tamoxifen triggered autophagy. Furthermore, the decrease in p-Akt and p-mTOR in MCF-7 cells, along with the increase in the autophagy marker proteins LC3II and P62, suggested that the Akt/mTOR pathway might be involved in the triggering of cell autophagy by the combination treatment. However, in an MCF-7-implanted nude mouse model, it was possible to detect significantly decreased tumour volumes and tumour weights and decreased p-Akt and p-mTOR protein expression in the celastrol+tamoxifen group. Therefore, our study provides the first evidence that celastrol combined with tamoxifen exerts synergistic anticancer effects by inducing apoptosis and autophagy in MCF-7 cells. Considering the urgent need for novel therapeutic strategies in anticancer therapy, this combinatorial approach is worthy of further investigation.

Autophagy Inhibition in BRAF-Driven Cancers

Simple Summary

BRAF is a protein kinase that is frequently mutationally activated in cancer. Mutant BRAF can be pharmacologically inhibited, which in combination with blockade of its direct effector, MEK1/2, is an FDA-approved therapeutic strategy for several BRAF-mutated cancer patients, such as melanoma, non-small-cell lung carcinoma, and thyroid cancer. However, therapy resistance is a major clinical challenge, highlighting the need for comprehensive investigations on the biological causes of such resistance, as well as to develop novel therapeutic strategies to improve patient survival. Autophagy is a cellular recycling process, which has been shown to allow cancer cells to escape from BRAF inhibition. Combined blockade of autophagy and BRAF signaling is a novel therapeutic strategy that is currently being tested in clinical trials. This review describes the relationship between BRAF-targeted therapy and autophagy regulation and discusses possible future treatment strategies.

Abstract

Several BRAF-driven cancers, including advanced BRAF^V600E/K-driven melanoma, non-small-cell lung carcinoma, and thyroid cancer, are currently treated using first-line inhibitor combinations of BRAF^V600E plus MEK1/2. However, despite the success of this vertical inhibition strategy, the durability of patient response is often limited by the phenomenon of primary or acquired drug resistance. It has recently been shown that autophagy, a conserved cellular recycling process, is increased in BRAF-driven melanoma upon inhibition of BRAF^V600E signaling. Autophagy is believed to promote tumor progression of established tumors and also to protect cancer cells from the cytotoxic effects of chemotherapy. To this end, BRAF inhibitor (BRAFi)-resistant cells often display increased autophagy compared to responsive lines. Several mechanisms have been proposed for BRAFi-induced autophagy, such as activation of the endoplasmic reticulum (ER) stress gatekeeper GRP78, AMP-activated protein kinase, and transcriptional regulation of the autophagy regulating transcription factors TFEB and TFE3 via ERK1/2 or mTOR inhibition. This review describes the relationship between BRAF-targeted therapy and autophagy regulation, and discusses possible future treatment strategies of combined inhibition of oncogenic signaling plus autophagy for BRAF-driven cancers.

Autophagy promotes invadopodia formation in human ovarian cancer cells via the p62-extracellular signal-regulated kinase 1/2 pathway

Invasiveness and metastatic potential are among the most essential characteristics of malignant tumors. Furthermore, it has been reported that autophagy and invasion are enhanced when tumor cells are grown in adverse conditions, such as nutritional deficiency and starvation. However, the association between autophagy and invasion remains largely unclear. In the present study, Earle's balanced salt solution (EBSS) was used to induce autophagy and an autophagy inhibitor was used to block autophagy. The results of Transwell assays revealed that autophagy inhibition limited the invasiveness of human ovarian cancer cells. Furthermore, the results of invadopodia formation assay indicated that autophagy stimulated invadopodia formation, and the selective autophagy receptor and signaling adaptor, sequestosome-1 (SQSTM1/p62 or simply p62), was closely associated with invadopodia formation in human ovarian cancer SKOV3 cells. The results of western blot analysis indicated that autophagy induced changes in p62 protein levels and p62 then functioned as a negative regulator of extracellular signal-regulated kinase 1/2 (ERK1/2) activity and invadopodia formation. The interaction between autophagy and invasion may thus be a self-protective mechanism for tumor cells in an unfavorable environment of nutritional deficiency, that maintains their survival and leads to increased invasiveness. An exploration of the intrinsic link between autophagy and invasion may provide a novel theoretical basis to reverse the resistance of tumor cells to a nutritional deficient environment.

Autophagy: Instructions from the extracellular matrix

In recent years, extensive research has uncovered crucial regulatory roles for the extracellular matrix (ECM) in regulating autophagy. Autophagy is a ubiquitous and highly conserved catabolic process that allows the selective removal and recycling of cytosolic components via lysosomal or vacuolar degradation. Due to its pivotal role in cellular homeostasis, the impairment of autophagy is involved in the pathophysiology of numerous diseases, comprising infectious diseases, immune and neurodegenerative disorders, renal and hepatic diseases, intervertebral and cartilage disorders, as well as fibrosis and cancer. Several ECM-derived proteoglycans and proteins, including decorin, biglycan, endorepellin, endostatin, collagen VI, and plasminogen kringle 5, have been identified as strong inducers of autophagy. In contrast, laminin α2, perlecan, and lumican exert opposite function by suppressing autophagy. Importantly, by direct interaction with various receptors, which interplay with their co-receptors and adhesion molecules, the ECM is able to direct autophagy in a molecular and cell context-specific manner. Thus, vast pharmacological potential resides in translating this knowledge into the development of ECM-derived therapeutics selectively regulating autophagy.