Targeting autophagy in liver cancer

Cold atmospheric plasma sensitizes head and neck cancer to chemotherapy and immune checkpoint blockade therapy

Head and neck cancer (HNC) is the seventh most prevalent cancer globally, often characterized by chemo-resistance and immunosuppression, which significantly hampers treatment efficacy. Cold atmospheric plasma (CAP) has recently emerged as a promising adjuvant oncotherapy with substantial potential and advantages. In this study, Piezobrush® PZ2, a handheld CAP unit based on the piezoelectric direct discharge technology, was used to generate and deliver non-thermal plasma. We aimed to investigate the effects of CAPPZ2 on various types of HNC cells and elucidate the underlying mechanisms. In addition, we endeavored to examine the efficacy of combining CAPPZ2 with chemotherapy drugs (i.e., cisplatin) or immune checkpoint blockade (ICB, i.e., PD1 antibody) in HNC treatment. Firstly, the results demonstrated that CAPPZ2 exerted anti-neoplastic functions through inhibiting cell proliferation, migration and invasion, and promoting apoptosis and autophagy. Secondly, using transcriptomic sequencing, Western blotting, and quantitative real-time PCR, the mechanisms underlying CAPPZ2 treatment in vitro was presumed to be a multitargeted blockade of major cancer survival pathways, such as redox balance, glycolysis, and PI3K/AKT/mTOR/HIF-1α signaling. Lastly, combinatorial thearpy containing CAPPZ2 and cisplatin or PD-1 antibody significantly suppressed tumor growth and prolonged recipient survival in vivo. Collectively, the synergistic effects of CAPPZ2 and cisplatin or PD-1 antibody could serve as a promising solution to enhance head and neck tumor elimination.

TRIM13 inhibits cell proliferation and induces autophagy in lung adenocarcinoma by regulating KEAP1/NRF2 pathway

Lung adenocarcinoma (LUAD) is the most common type of lung cancer. Tripartite motif 13 (TRIM13) is a member of TRIM protein family and is downregulated in multiple cancers, especially non-small cell lung cancers (NSCLC). In this study, we investigated anti-tumor mechanism of TRIM13 in non-small cell lung cancer tissues and cell lines. First, the mRNA and protein levels of TRIM13 in LUAD tissue and cells were measured. TRIM13 was overexpressed on LUAD cells to investigate the effects on cell proliferation, apoptosis, oxidative stress, p62 ubiquitination, and autophagy activation. Finally, mechanistic role of TRIM13 in regulating the Keap1/Nrf2 pathway was investigated. Results indicated that low level of TRIM13 mRNA and protein expression was found in LUAD tissue and cells. Overexpression of TRIM13 in LUAD cancer cells suppressed their proliferation, increased apoptosis, and oxidative stress, ubiquitinated p62, and activated autophagy via the RING finger domain of TRIM13. Furthermore, TRIM13 showed interaction with p62 and mediated its ubiquitination and degradation in LUAD cells. Mechanistically, TRIM13 exerted the tumor suppressor functions in LUAD cells by negatively regulating Nrf2 signaling and downstream antioxidants, which was further confirmed by in vivo data from xenografts. In conclusion, TRIM13 behaves like a tumor suppressor and triggers autophagy in LUAD cells by mediating p62 ubiquitination via KEAP1/Nrf2 pathway. Our findings provide a novel insight into targeted therapy plans for LUAD.

Synergic Induction of Autophagic Cell Death in Anaplastic Thyroid Carcinoma

Anaplastic thyroid carcinoma (ATC) has poor prognosis, high mortality rate and lack of effective therapy. A synergic combination of PD-L1 antibody together with cell death promoting substances like deacetylase inhibitors (DACi) and multi-kinase inhibitors (MKI) could sensitize ATC cells and promote decay by autophagic cell death. The PD-L1-inhibitor atezolizumab synergized with panobinostat (DACi) and sorafenib (MKI) leading to significant reduction of the viability, measured by real time luminescence, of three different patient-derived primary ATC cells, of C643 cells and follicular epithelial thyroid cells too. Solo administration of these compounds caused a significant over-expression of autophagy transcripts; meanwhile autophagy proteins were almost not detectable after the single administration of panobinostat, thus supporting a massive autophagy degradation process. Instead, the administration of atezolizumab caused an accumulation of autophagy proteins and the cleavage of the active caspases 8 and 3. Interestingly, only panobinostat and atezolizumab were able to exacerbate the autophagy process by increasing the synthesis, the maturation and final fusion with the lysosomes of the autophagosome vesicles. Despite ATC cells could be sensitized by atezolizumab via the cleavage of the caspases, no reduction of cell proliferation or promotion of cell death was observed. The apoptosis assay evidenced the ability of panobinostat alone and in combination with atezolizumab to induce the phosphatidil serine exposure (early apoptosis) and further the secondary necrosis. Instead, sorafenib was only able to cause necrosis. The increase of caspases activity induced by atezolizumab, the apoptosis and autophagy processes promoted by panobinostat synergize thus promoting cell death in well-established and primary anaplastic thyroid cancer cells. The combined therapy could represent a future clinical application for the treatment of such lethal and untreatable solid cancer.

MHBSt167 induced autophagy promote cell proliferation and EMT by activating the immune response in L02 cells

Background

Hepatitis B virus can induce hepatocellular carcinoma (HCC) by inducing a host immune response against infected hepatocytes. C-terminally truncated middle surface protein (MHBSt) has been reported to contribute to HCC through transcriptional activation in epidemiology studies, while the underlying mechanism of MHBSt-induced HCC is unknown.

Methods

In this study, a premature stop at codon 167 in MHBS (MHBSt¹⁶⁷) was investigated into eukaryotic expression plasmid pcDNA3.1(-). MHBSt¹⁶⁷ expressed plasmid was transfected into the L02 cell line, cell proliferation was analyzed by CCK-8 and high-content screening assays, the cell cycle was analyzed by flow cytometry, and epithelial-to-mesenchymal transition and autophagy were analyzed by immunoblotting and immunofluorescence. NF-κB activation and the MHBSt¹⁶⁷-induced immune response were analyzed by immunoblotting and immunofluorescence. IFN-α, IFN-β and IL-1α expression were analyzed by qPCR. Autophagy inhibitors were used to analyze the relationship between the immune response and autophagy.

Results

The results showed that MHBSt¹⁶⁷ promoted L02 cell proliferation, accelerated cell cycle progression from the S to G2 phase and promoted epithelial-to-mesenchymal transition through ER-stress, leading to autophagy and NF-κB activation and increased immune-related factor expression. The MHBSt¹⁶⁷-induced acceleration of cell proliferation and the cell cycle was abolished by autophagy or NF-κB inhibitors.

Conclusion

In summary, MHBSt¹⁶⁷ could promote cell proliferation, accelerate cell cycle progression, induce EMT and activate autophagy through ER-stress to induce the host immune response, supporting a potential role of MHBSt¹⁶⁷ in contributing to carcinogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01840-z.

Long Non-Coding RNA H19 Expression Correlates with Autophagy Process in Adrenocortical Carcinoma

Adrenocortical carcinoma (ACC) is characterized by poor prognosis and high mortality. The suppression of the long-non-coding RNA H19, counterbalanced by IGF2 over-expression, leads to down-regulation of the autophagy markers, high proliferation rate and metastatic potential in patients affected by ACC. The administration of the deacetylase inhibitors (DACi) panobinostat, trichostatin A (TSA) and SAHA affected the cell viability of H295R monolayer and spheroids and induced the over-expression of H19 and autophagy transcripts. H19 knock down in H295R cells was not able to modulate the expression level of autophagy transcripts. Instead, H19 knock down was able to impede the ability of DACi to modulate the protein level of the autophagy markers. Furthermore, the administration of higher concentration of DACi was able to down-regulate the protein level of Beclin1 and p62 and to induce the conversion of LC3B-I into the active LC3B-II form, thus confirming an active autophagic process. Neither the active protein level nor the activity of caspases 8 and 3 was prompted by the DACi, thus excluding the involvement of the executioners of apoptosis in H295R decay. The DACi restore H19, the autophagy markers and trigger cell death in ACC cells. The re-activation of autophagy would represent a novel strategy for the treatment of patients affected by this severe malignancy.

Role of Autophagy in Cadmium-Induced Hepatotoxicity and Liver Diseases

Cadmium (Cd) is a toxic pollutant that is associated with several severe human diseases. Cd can be easily absorbed in significant quantities from air contamination/industrial pollution, cigarette smoke, food, and water and primarily affects the liver, kidney, and lungs. Toxic effects of Cd include hepatotoxicity, nephrotoxicity, pulmonary toxicity, and the development of various human cancers. Cd is also involved in the development and progression of fatty liver diseases and hepatocellular carcinoma. Cd affects liver function via modulation of cell survival/proliferation, differentiation, and apoptosis. Moreover, Cd dysregulates hepatic autophagy, an endogenous catabolic process that detoxifies damaged cell organelles or dysfunctional cytosolic proteins through vacuole-mediated sequestration and lysosomal degradation. In this article, we review recent developments and findings regarding the role of Cd in the modulation of hepatotoxicity, autophagic function, and liver diseases at the molecular level.

Biochemical Mechanisms Associating Alcohol Use Disorders with Cancers

Simple Summary

Of all yearly deaths attributable to alcohol consumption globally, approximately 12% are due to cancers, representing approximately 0.4 million deceased individuals. Ethanol metabolism disturbs cell biochemistry by targeting the structure and function of essential biomolecules (proteins, nucleic acids, and lipids) and by provoking alterations in cell programming that lead to cancer development and cancer malignancy. A better understanding of the metabolic and cell signaling realm affected by ethanol is paramount to designing effective treatments and preventive actions tailored to specific neoplasias.

Abstract

The World Health Organization identifies alcohol as a cause of several neoplasias of the oropharynx cavity, esophagus, gastrointestinal tract, larynx, liver, or female breast. We review ethanol’s nonoxidative and oxidative metabolism and one-carbon metabolism that encompasses both redox and transfer reactions that influence crucial cell proliferation machinery. Ethanol favors the uncontrolled production and action of free radicals, which interfere with the maintenance of essential cellular functions. We focus on the generation of protein, DNA, and lipid adducts that interfere with the cellular processes related to growth and differentiation. Ethanol’s effects on stem cells, which are responsible for building and repairing tissues, are reviewed. Cancer stem cells (CSCs) of different origins suffer disturbances related to the expression of cell surface markers, enzymes, and transcription factors after ethanol exposure with the consequent dysregulation of mechanisms related to cancer metastasis or resistance to treatments. Our analysis aims to underline and discuss potential targets that show more sensitivity to ethanol’s action and identify specific metabolic routes and metabolic realms that may be corrected to recover metabolic homeostasis after pharmacological intervention. Specifically, research should pay attention to re-establishing metabolic fluxes by fine-tuning the functioning of specific pathways related to one-carbon metabolism and antioxidant processes.

Interplay of autophagy and cancer stem cells in hepatocellular carcinoma

Liver cancer is the sixth most common cancer and the fourth leading cause of cancer deaths in the world. The most common type of liver cancers is hepatocellular carcinoma (HCC). Autophagy is the cellular digestion of harmful components by sequestering the waste products into autophagosomes followed by lysosomal degradation for the maintenance of cellular homeostasis. The impairment of autophagy is highly associated with the development and progression of HCC although autophagy may be involved in tumour-suppressing cellular events. In regards to its protecting role, autophagy also shelters the cells from anoikis- a programmed cell death in anchorage-dependent cells detached from the surrounding extracellular matrix which facilitates metastasis in HCC. Liver cancer stem cells (LCSCs) have the ability for self-renewal and differentiation and are associated with the development and progression of HCC by regulating stemness, resistance and angiogenesis. Interestingly, autophagy is also known to regulate normal stem cells by promoting cellular survival and differentiation and maintaining cellular homeostasis. In this review, we discuss the basal autophagic mechanisms and double-faceted roles of autophagy as both tumour suppressor and tumour promoter in HCC, as well as its association with and contribution to self-renewal and differentiation of LCSCs.

Regulation of autophagy by microRNAs in human breast cancer

Breast cancer is the most common solid cancer that affects female population globally. MicroRNAs (miRNAs) are short non-coding RNAs that can regulate post-transcriptional modification of multiple downstream genes. Autophagy is a conserved cellular catabolic activity that aims to provide nutrients and degrade un-usable macromolecules in mammalian cells. A number of in vitro, in vivo and clinical studies have reported that some miRNAs could modulate autophagy activity in human breast cancer cells, and these would influence human breast cancer progression and treatment response. Therefore, this review was aimed to discuss the roles of autophagy-regulating miRNAs in influencing breast cancer development and treatment response. The review would first introduce autophagy types and process, followed by the discussion of the roles of different miRNAs in modulating autophagy in human breast cancer, and to explore how would this miRNA-autophagy regulatory process affect the disease progression or treatment response. Lastly, the potential applications and challenges of utilizing autophagy-regulating miRNAs as breast cancer biomarkers and novel therapeutic agents would be discussed.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

Combination treatment strategies with a focus on rosiglitazone and adriamycin for insulin resistant liver cancer

Insulin resistance promotes the occurrence of liver cancer and decreases its chemosensitivity. Rosiglitazone (ROSI), a thiazolidinedione insulin sensitiser, could be used for diabetes with insulin resistance and has been reported to show anticancer effects on human malignant cells. In this paper, we investigated the combination of ROSI and chemotherapeutics on the growth and metastasis of insulin-resistant hepatoma. In vitro assay, ROSI significantly enhanced the inhibitory effects of adriamycin (ADR) on the proliferation, autophagy and migration of insulin-resistant hepatoma HepG2/IR cells via downregulation of EGFR/ERK and AKT/mTOR signalling pathway. In addition, ROSI promoted the apoptosis of HepG2/IR cells induced by ADR. In vivo assay, high fat and glucose diet and streptozotocin (STZ) induced insulin resistance in mice by increasing the body weight, fasting blood glucose (FBG) level, oral glucose tolerance, fasting insulin level and insulin resistance index. Both the growth of mouse liver cancer hepatoma H22 cells and serum FBG level in insulin resistant mice were significantly inhibited by combination of ROSI and ADR. Thus, ROSI and ADR in combination showed a stronger anti-tumour effect in insulin resistant hepatoma cells accompanying with glucose reduction and might represent an effective therapeutic strategy for liver cancer accompanied with insulin resistant diabetes.

Modulation of Pancreatic Neuroendocrine Neoplastic Cell Fate by Autophagy-Mediated Death

INTRODUCTION

Autophagic cell death in cancer cells can be mediated by inhibition of deacetylases. Although extensive studies have focused on the autophagic process in cancer, little is known about the role of autophagy in degrading cytosolic and nuclear components of pancreatic neuroendocrine neoplastic (pNEN) cells leading to cell death, thus improving the therapy of patients affected by pNEN.

METHODS

2D and 3D human pNEN and pancreatic stellate cells were treated with panobinostat and bafilomycin. Autophagy markers were detected by RT-qPCR, immunofluorescence, and Western blot. Autophagosomes were detected by electron microscopy and their maturation by real-time fluorescence of LC3B stable transfected cells. ChIP was performed at the cAMP responsive element. Immunofluorescence was performed in murine pancreatic tissue.

RESULTS

We observed that pan-deacetylase inhibitor panobinostat treatment causes autophagic cell death in pNEN cells. We also found that although AMPK-α phosphorylation is counterbalanced by phosphorylated AKT, it is not capable to inhibiting autophagic cell death. However, the binding activity of the cAMP responsive element is prompted by panobinostat. Although autophagy inhibition prevented autophagosome synthesis, maturation, and cell death, panobinostat treatment induced the accumulation of mature autophagosomes in the cytosol and the nucleus, leading to disruption of the organelles, cellular digestion, and decay. Observation of autophagosome membrane proteins Beclin1 and LC3B aggregation in murine pancreatic islets indicates that autophagy restoration may also lead to autophagosome aggregation in murine insulinoma cells. A basal low expression of autophagy markers was detectable in patients affected by pNEN, and, interestingly, the expression of these markers was significantly lower in metastatic pNEN.

DISCUSSION/CONCLUSION

Our study highlights that the autophagy functional restoration and prolongation of this catabolic process, mediated by inhibition of deacetylase, is responsible for the reduction of pNEN cells. Prompting of autophagy cell death could be a promising strategy for the therapy of pNEN.

The PAD4 inhibitor GSK484 enhances the radiosensitivity of triple-negative breast cancer

Triple-negative breast cancer (TNBC) accounts for approximately 10-20% of all breast cancers and is one of the leading causes of mortality among females. Radiotherapy is essential during the treatment of breast cancer. Growing evidence has indicated that peptidyl arginine deiminase-4 (PAD4) inhibitor can alleviate the development of multiple cancers, including breast cancer, through inhibiting cell proliferation. GSK484 is considered to be a highly potent PAD4-selective inhibitors. However, the potential role and mechanism of GSK484 in TNBC remain unclear. In this study, we intended to explore the effects of GSK484 on the radiosensitivity of TNBC cell lines (MDA-MB-231 and BT-549). We found that the pretreatment of GSK484 enhanced irradiation (IR)-induced inhibitory effects on cell proliferation, migration and invasion. Besides, our findings revealed that GSK484 facilitated TNBC cell apoptosis. IR treatment-induced increase of the protein level of ATG5 and ATG7, and decrease of p62 protein level were countervailed by GSK484. In addition, GSK484 enhanced DNA damage induced by IR. Moreover, in vivo experiments demonstrated that the combined treatment of IR and GSK484 showed an obvious decline of tumor growth in contrast to IR-alone or GSK484-alone treatment. Overall, GSK484 may serve as a radiosensitizer of TNBC through inhibiting IR-induced autophagy.

The Role of Autophagy in Liver Cancer: Crosstalk in Signaling Pathways and Potential Therapeutic Targets

Autophagy is an evolutionarily conserved lysosomal-dependent pathway for degrading cytoplasmic proteins, macromolecules, and organelles. Autophagy-related genes (Atgs) are the core molecular machinery in the control of autophagy, and several major functional groups of Atgs coordinate the entire autophagic process. Autophagy plays a dual role in liver cancer development via several critical signaling pathways, including the PI3K-AKT-mTOR, AMPK-mTOR, EGF, MAPK, Wnt/β-catenin, p53, and NF-κB pathways. Here, we review the signaling pathways involved in the cross-talk between autophagy and hepatocellular carcinoma (HCC) and analyze the status of the development of novel HCC therapy by targeting the core molecular machinery of autophagy as well as the key signaling pathways. The induction or the inhibition of autophagy by the modulation of signaling pathways can confer therapeutic benefits to patients. Understanding the molecular mechanisms underlying the cross-link of autophagy and HCC may extend to translational studies that may ultimately lead to novel therapy and regimen formation in HCC treatment.

The dichotomous role of TGF-β in controlling liver cancer cell survival and proliferation

Hepatocellular carcinoma (HCC) is the major form of primary liver cancer and one of the most prevalent and life-threatening malignancies globally. One of the hallmarks in HCC is the sustained cell survival and proliferative signals, which are determined by the balance between oncogenes and tumor suppressors. Transforming growth factor beta (TGF-β) is an effective growth inhibitor of epithelial cells including hepatocytes, through induction of cell cycle arrest, apoptosis, cellular senescence, or autophagy. The antitumorigenic effects of TGF-β are bypassed during liver tumorigenesis via multiple mechanisms. Furthermore, along with malignant progression, TGF-β switches to promote cancer cell survival and proliferation. This dichotomous nature of TGF-β is one of the barriers to therapeutic targeting in liver cancer. Thereafter, understanding the underlying molecular mechanisms is a prerequisite for discovering novel antitumor drugs that may specifically disable the growth-promoting branch of TGF-β signaling or restore its tumor-suppressive arm. This review summarizes how TGF-β inhibits or promotes liver cancer cell survival and proliferation, highlighting the functional switch mechanisms during the process.

Autophagy and Liver Diseases

Autophagy plays an important role in the physiology and pathology of the liver. It is involved in the development of many liver diseases such as α-1-antitrypsin deficiency, chronic hepatitis virus infection, alcoholic liver disease, nonalcoholic fatty liver disease, and liver cancer. Autophagy has thus become a new target for the treatment of liver diseases. How to treat liver diseases by regulating autophagy has been a hot topic.

A zinc finger family protein, ZNF263, promotes hepatocellular carcinoma resistance to apoptosis via activation of ER stress-dependent autophagy

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide. Endoplasmic reticulum stress (ERS) is generally activated in HCC and is important for the sensitivity of HCC to anticancer drugs. ERS-dependent autophagy is a crucial mechanism affecting the sensitivity of HCC to anticancer drugs, but the mechanism by which ERS regulates autophagy is not well understood. Zinc finger protein 263 (ZNF263) is a transcription factor member of the zinc finger family. However, its functional role in HCC remains to be studied. In the current study, we investigated the role of ZNF263 in regulating ERS-induced chemoresistance in HCC and its possible mechanism. We found that ZNF263 was the most significant ERS-specific super-enhancer bounding transcriptional factor and was up-regulated in HCC patients and cell lines. Further, ZNF263 expression correlated with ERS, clinical stage and shorter survival in HCC patients. ZNF263 knockdown by RNA interference results in decreased proliferation, apoptosis resistance, and chemoresistance. Further study showed that ZNF263 increased chemoresistance by activating ERS-related autophagy. In conclusion, our study highlights ZNF263 as a functional ERS-related tumor activator and indicates it as a potential target for HCC therapy.

A combination of AZD5363 and FH5363 induces lethal autophagy in transformed hepatocytes

Hepatocellular carcinoma (HCC) is one of the major causes of cancer-related death worldwide. High Akt activation and aberrant β-catenin expression contribute to HCC cell proliferation, stem cell generation, and metastasis. Several signaling pathway-specific inhibitors are in clinical trials and display different efficacies against HCC. In this study, we observed that a β-catenin inhibitor (FH535) displays antiproliferative effect on transformed human hepatocytes (THH). A combination treatment of these cells with FH535 and Akt inhibitor (AZD5363) exerted a stronger effect on cell death. Treatment of THH with AZD5363 and FH535 inhibited cell-cycle progression, enhanced autophagy marker protein expression, and autophagy-associated death, while FH535 treatment alone induced apoptosis. The use of chloroquine or z-VAD further verified these observations. Autophagy flux was evident from lowering marker proteins LAMP2, LAPTM4B, and autophagic protein expression by confocal microscopy using mCherry-EGFP-LC3 reporter construct. A combination treatment with AZD5363 and FH535 enhanced p53 expression, by modulating MDM2 activation; however, AZD5363 treatment alone restricted p53 to the nucleus by inhibiting dynamin-related protein activation. Nuclear p53 plays a crucial role for activation of autophagy by regulating the AMPK–mTOR-ULK1 pathway. Hep3B cells with null p53 did not modulate autophagy-dependent death from combination treatment. Together, our results strongly suggested that a combination treatment of Akt and β-catenin inhibitors exhibits efficient therapeutic potential for HCC.

Autophagy: A Potential Therapeutic Target of Polyphenols in Hepatocellular Carcinoma

Autophagy is a conserved biological phenomenon that maintains cellular homeostasis through the clearing of damaged cellular components under cellular stress and offers the cell building blocks for cellular survival. Aberrations in autophagy subsidize to various human pathologies, such as dementia, cardiovascular diseases, leishmaniosis, influenza, hepatic diseases, and cancer, including hepatocellular carcinoma (HCC). HCC is the fifth common mortal type of liver cancer globally, with an inhomogeneous topographical distribution and highest incidence tripled in men than women. Existing treatment procedures with liver cancer patients result in variable success rates and poor prognosis due to their drug resistance and toxicity. One of the pathophysiological mechanisms that are targeted during the development of anti-liver cancer drugs is autophagy. Generally, overactivated autophagy may lead to a non-apoptotic form of programmed cell death (PCD) or autophagic cell death or type II PCD. Emerging evidence suggests that manipulation of autophagy could induce type II PCD in cancer cells, acting as a potential tumor suppressor. Hence, altering autophagic signaling offers new hope for the development of novel drugs for the therapy of resistant cancer cells. Natural polyphenolic compounds, including flavonoids and non-flavonoids, execute their anticarcinogenic mechanism through upregulating tumor suppressors and autophagy by modulating canonical (Beclin-1-dependent) and non-canonical (Beclin-1-independent) signaling pathways. Additionally, there is evidence signifying that plant polyphenols target angiogenesis and metastasis in HCC via interference with multiple intracellular signals and decrease the risk against HCC. The current review offers a comprehensive understanding of how natural polyphenolic compounds exhibit their anti-HCC effects through regulation of autophagy, the non-apoptotic mode of cell death.

Metabolism of Histone Deacetylase Proteins Opsonizes Tumor Cells to Checkpoint Inhibitory Immunotherapies

LC3-associated phagocytosis, a distinct form of autophagy, plays a key role in antigen presentation. Autophagy itself plays a central role in the regulation of cellular metabolism. Proteins that regulate autophagy include the AMPK which senses high levels of AMP, and mTOR, which integrates amino acid and fatty acid metabolism with autophagy. More recently, autophagy has been demonstrated to regulate tumor cell immunogenicity via the degradation of histone deacetylase proteins. Individual drugs and drug combinations that activate the ATM-AMPK pathway and inactivate mTOR, cause autophagosome formation. The maturation of autophagosomes into autolysosomes causes the autophagic degradation of histone deacetylase proteins who regulate the transcription of PD-L1, Class I MHCA, ODC and IDO1. Indeed, drug combinations that do not contain an HDAC inhibitor can nevertheless act as de facto HDAC inhibitors, via autophagic degradation of HDAC proteins. Such drug combinations simultaneously kill tumor cells via immunogenic autophagy and in parallel opsonize tumor cells to checkpoint inhibitor immunotherapies via reduced expression of PD-L1, ODC and IDO1, and increased expression of Class I MHCA.

A New Histone Deacetylase Inhibitor Enhances Radiation Sensitivity through the Induction of Misfolded Protein Aggregation and Autophagy in Triple-Negative Breast Cancer

Radiation therapy (RT) is one of the main treatments for triple-negative breast cancer (TNBC). However, many patients experience RT failure due to the metastatic potential of RT and the radiation resistance of several cancers. Histone deacetylase inhibitors (HDACis) can serve as radiosensitizers. In this study, we investigated whether a novel HDACi, TMU-35435, could reinforce radiosensitivity through the induction of misfolded protein aggregation and autophagy in TNBC. Significantly enhanced toxicity was found for the combination treatment compared with TMU-35435 or irradiation (IR) treatment alone in TNBC cells. The combination treatment induced misfolded protein aggregation and TMU-35435 inhibited the interaction of HDAC6 with dynein. Furthermore, the combined treatment induced endoplasmic reticulum (ER) stress but did not trigger apoptosis. In addition, the combination treatment caused autophagic cell death. Tumor growth in the mouse of model orthotopic breast cancer was suppressed by the combination treatment through the induction of ER stress and autophagy. These findings support the future evaluation of the novel HDACi TMU-35435, as a potent radiosensitizer in TNBC.

Relevance of Autophagy in Parenchymal and Non-Parenchymal Liver Cells for Health and Disease

Autophagy is a highly conserved intracellular process for the ordered degradation and recycling of cellular components in lysosomes. In the liver, parenchymal cells (i.e., mainly hepatocytes) utilize autophagy to provide amino acids, glucose, and free fatty acids as sources of energy and biosynthesis functions, but also for recycling and controlling organelles such as mitochondria. Non-parenchymal cells of the liver, including endothelial cells, macrophages (Kupffer cells), and hepatic stellate cells (HSC), also employ autophagy, either for maintaining cellular homeostasis (macrophages, endothelium) or for providing energy for their activation (stellate cells). In hepatocytes, autophagy contributes to essential homeostatic functions (e.g., gluconeogenesis, glycogenolysis, fatty acid oxidation), but is also implicated in diseases. For instance, storage disorders (alpha 1 antitrypsin deficiency, Wilson's disease), metabolic (non-alcoholic steatohepatitis, NASH), and toxic (alcohol) liver diseases may benefit from augmenting autophagy in hepatocytes. In hepatic fibrosis, autophagy has been implicated in the fibrogenic activation of HSC to collagen-producing myofibroblasts. In hepatocellular carcinoma (HCC), autophagy may contribute to tumor surveillance as well as invasiveness, indicating a dual and stage-dependent function in cancer. As many drugs directly or indirectly modulate autophagy, it is intriguing to investigate autophagy-targeting, possibly even cell type-directed strategies for the treatment of hereditary liver diseases, NASH, fibrosis, and HCC.