Apoptin induces pyroptosis of colorectal cancer cells via the GSDME-dependent pathway.

Apoptin is a small molecular weight protein encoded by the VP3 gene of chicken anemia virus (CAV). It can induce apoptosis of tumor cells and play anti-tumorigenic functions. In this study, we identified a time-dependent inhibitory role of apoptin on the viability of HCT116 cells. We also demonstrated that apoptin induces pyroptosis through cleaved caspase 3, and with a concomitant cleavage of gasdermin E (GSDME) rather than GSDMD. GSDME knockdown switched the apoptin-induced cell death from pyroptosis to apoptosis in vitro. Furthermore, we demonstrated that the effect of apoptin on GSDME-dependent pyroptosis could be mitigated by caspase-3 and caspase-9 siRNA knockdown. Additionally, apoptin enhanced the intracellular reactive oxygen species (ROS), causing aggregation of the mitochondrial membrane protein Tom20. Moreover, bax and cytochrome c were released to the activating caspase-9, eventually triggering pyroptosis. Therefore, GSDME mediates the apoptin-induced pyroptosis through the mitochondrial apoptotic pathway. Finally, using nude mice xenografted with HCT116 cells, we found that apoptin induces pyroptosis and significantly inhibits tumor growth. Based on this mechanism, apoptin may provide a new strategy for colorectal cancer therapy.

Inhibition of Autophagy Suppresses SARS-CoV-2 Replication and Ameliorates Pneumonia in hACE2 Transgenic Mice and Xenografted Human Lung Tissues.

Autophagy is thought to be involved in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, how SARS-CoV-2 interferes with the autophagic pathway and whether autophagy contributes to virus infection in vivo is unclear. In this study, we identified SARS-CoV-2-triggered autophagy in animal models, including the long-tailed or crab-eating macaque (Macaca fascicularis), human angiotensin-converting enzyme 2 (hACE2) transgenic mice, and xenografted human lung tissues. In Vero E6 and Huh-7 cells, SARS-CoV-2 induces autophagosome formation, accompanied by consistent autophagic events, including inhibition of the Akt-mTOR pathway and activation of the ULK-1-Atg13 and VPS34-VPS15-Beclin1 complexes, but it blocks autophagosome-lysosome fusion. Modulation of autophagic elements, including the VPS34 complex and Atg14, but not Atg5, inhibits SARS-CoV-2 replication. Moreover, this study represents the first to demonstrate that the mouse bearing xenografted human lung tissue is a suitable model for SARS-CoV-2 infection and that autophagy inhibition suppresses SARS-CoV-2 replication and ameliorates virus-associated pneumonia in human lung tissues. We also observed a critical role of autophagy in SARS-CoV-2 infection in an hACE2 transgenic mouse model. This study, therefore, gives insights into the mechanisms by which SARS-CoV-2 manipulates autophagosome formation, and we suggest that autophagy-inhibiting agents might be useful as therapeutic agents against SARS-CoV-2 infection. IMPORTANCE Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a global pandemic with limited therapeutics. Insights into the virus-host interactions contribute substantially to the development of anti-SARS-CoV-2 therapeutics. The novelty of this study is the use of a new animal model: mice xenografted with human lung tissues. Using a combination of in vitro and in vivo studies, we have obtained experimental evidence that induction of autophagy contributes to SARS-CoV-2 infection and improves our understanding of potential therapeutic targets for SARS-CoV-2.

lncRNA MIAT/HMGB1 Axis Is Involved in Cisplatin Resistance via Regulating IL6-Mediated Activation of the JAK2/STAT3 Pathway in Nasopharyngeal Carcinoma.

Cisplatin-based chemotherapy and radiotherapy are the main first-line treatment strategies for nasopharyngeal carcinoma (NPC) patients. Unfortunately, resistance is a major obstacle in the clinical management of NPC patients. We prove that the expression level of high-mobility group box 1 (HMGB1) is dramatically increased in resistant NPC cells than that in sensitive cells. HMGB1 induces the expression and secretion of IL6, which leads to constitutive autocrine activation of the JAK2/STAT3 pathway and eventually contributes to chemoresistance in NPC cells. Long non-coding RNAs (lncRNAs) have been identified as key regulators involved in drug resistance. In this study, using GO analysis of the biological process and differential expression analysis, we find 12 significantly altered IncRNAs in NPC cell lines, which may be involved in regulating gene expression. Furthermore, we determine that elevated lncRNA MIAT level upregulates HMGB1 expression, contributing to cisplatin resistance in NPC cells. We find that the deficiency of the lncRNA MIAT/HMGB1 axis, inhibition of JAK2/STAT3, or neutralization of IL6 by antibodies significantly re-sensitizes resistant NPC cells to cisplatin in resistant NPC cells. Moreover, we provide the in vivo evidence that the deficiency of HMGB1 reduces cisplatin-resistant tumor growth. Most importantly, we provide clinical evidence showing that the expression level of the lncRNA MIAT/HMGB1/IL6 axis is elevated in resistant NPC tumors, which is highly correlated with poor clinical outcome. Our findings identify a novel chemoresistance mechanism regulated by the lncRNA MIAT/HMGB1/IL6 axis, which indicates the possibilities for lncRNA MIAT, HMGB1, and IL6 as biomarkers for chemoresistance and targets for developing novel strategies to overcome resistance in NPC patients.

Effects of Apoptin-Induced Endoplasmic Reticulum Stress on Lipid Metabolism, Migration, and Invasion of HepG-2 Cells.

In this study, we investigated the effects of Apoptin-induced endoplasmic reticulum (ER) stress on lipid metabolism, migration and invasion of HepG-2 cells, and preliminarily explored the relationship between endoplasmic reticulum stress, lipid metabolism, migration, and invasion. The effects of Apoptin on ER function and structure in HepG-2 cells were determined by flow cytometry, fluorescence staining and western blotting by assessing the expression levels of ER stress related proteins. The effects of Apoptin on HepG-2 cells' lipid metabolism were determined by western blot analysis of the expression levels of triglyceride, cholesterol, and lipid metabolism related enzymes. The effects of Apoptin on HepG-2 cells' migration and invasion were studied using migration and invasion assays and by Western-blot analysis of the expression of proteins involved in migration and invasion. The in vivo effects of endoplasmic reticulum stress on lipid metabolism, migration and invasion of HepG-2 cells were also investigated by immunohistochemistry analysis of tumor tissues from HepG2 cells xenografted nude mice models. Both in vitro and in vivo experiments showed that Apoptin can cause a strong and lasting ER stress response, damage ER functional structure, significantly change the expression levels of lipid metabolism related enzymes and reduce the migration and invasion abilities of HepG-2 cells. Apoptin can also affect HepG-2 cells' lipid metabolism through endoplasmic reticulum stress and the abnormal expression of enzymes closely related to tumor migration and invasion. These results also showed that lipid metabolism may be one of the main inducements that reduce HepG-2 cells' migration and invasion abilities.

Inhibitors of endosomal acidification suppress SARS-CoV-2 replication and relieve viral pneumonia in hACE2 transgenic mice.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2 and broke out as a global pandemic in late 2019. The acidic pH environment of endosomes is believed to be essential for SARS-CoV-2 to be able to enter cells and begin replication. However, the clinical use of endosomal acidification inhibitors, typically chloroquine, has been controversial with this respect. METHODS: In this study, RT-qPCR method was used to detect the SARS-CoV-2N gene to evaluate viral replication. The CCK-8 assay was also used to evaluate the cytotoxic effect of SARS-CoV-2. In situ hybridization was used to examine the distribution of the SARS-CoV-2 gene in lung tissues. Hematoxylin and eosin staining was also used to evaluate virus-associated pathological changes in lung tissues. RESULTS: In this study, analysis showed that endosomal acidification inhibitors, including chloroquine, bafilomycin A1 and NH4CL, significantly reduced the viral yields of SARS-CoV-2 in Vero E6, Huh-7 and 293T-ACE2 cells. Chloroquine and bafilomycin A1 also improved the viability and proliferation of Vero E6 cells after SARS-CoV-2 infection. Moreover, in the hACE2 transgenic mice model of SARS-CoV-2 infection, chloroquine and bafilomycin A1 reduced viral replication in lung tissues and alleviated viral pneumonia with reduced inflammatory exudation and infiltration in peribronchiolar and perivascular tissues, as well as improved structures of alveolar septum and pulmonary alveoli. CONCLUSIONS: Our research investigated the antiviral effects of endosomal acidification inhibitors against SARS-CoV-2 in several infection models and provides an experimental basis for further mechanistic studies and drug development.

Autophagy promotes oncolysis of an adenovirus expressing apoptin in human bladder cancer models.

As a potential cancer therapy, we developed a recombinant adenovirus named Ad-VT, which was designed to express the apoptosis-inducing gene (apoptin) and selectively replicate in cancer cells via E1a manipulation. However, how it performs in bladder cancer remains unclear. We examined the antitumor efficacy of Ad-VT in bladder cancers using CCK-8 assays and xenograft models. Autophagy levels were evaluated by western blotting, MDC staining, and RFP-GFP-LC3 aggregates' analyses. Here, we report the selective replication and antitumor efficacy (viability inhibition and apoptosis induction) of Ad-VT in bladder cancer cells. Using xenograft tumor models, we demonstrate that its effects are tumor specific resulting in the inhibition of tumor growth and improvement of the survival of mice models. Most Importantly, Ad-VT induced a complete autophagy flux leading to autophagic cancer cell death through a signaling pathway involving AMPK, raptor and mTOR. Finally, we suggest that treatment combination of Ad-VT and rapamycin results in a synergistic improvement of tumor control and survival compared to monotherapy. This study suggests that Ad-VT can induce selective autophagic antitumor activities in bladder cancer through the AMPK-Raptor-mTOR pathway, which can be further improved by rapamycin.

Anti-tumour effects of a dual cancer-specific oncolytic adenovirus on Breast Cancer Stem cells.

Apoptin can specifically kill cancer cells but has no toxicity to normal cells. Human telomerase reverse transcriptase (hTERT) can act as a tumour-specific promoter by triggering the expression of certain genes in tumour cells. This study aims to investigate the inhibitory effects and to explore the inhibitory pathway of a dual cancer-specific recombinant adenovirus (Ad-apoptin-hTERTp-E1a, Ad-VT) on breast cancer stem cells. Breast cancer cell spheres were obtained from MCF-7 cells through serum-free suspension culture. The cell spheres were detected by flow cytometry for CD44+ CD24- cell subsets. The stemness of MCF-7-CSC cells was confirmed by in vivo tumorigenesis experiments. The inhibitory effect of the recombinant adenoviruses on MCF-7-CSC cells was evaluated by CCK-8 assay. In addition, the stemness of adenovirus-infected MCF-7-CSC cells was analysed by testing the presence of CD44+ CD24- cell subsets. The ability of the recombinant adenovirus to induce MCF-7-CSC cell apoptosis was detected by staining JC-1, TMRM and Annexin V. Our results showed that a significantly higher proportion of the CD44+ CD24- cell subsets was present in MCF-7-CSC cells with a significantly increased expression of stem cell marker proteins. The MCF-7-CSC cells, whlist exhibited a strong tumorigenic ability with a certain degree of stemness in mice, were shown to be strongly inhibited by recombinant adenovirus Ad-VT through cell apoptosis. In addition, Ad-VT was shown to exert a killing effect on BCSCs. These results provide a new theoretical basis for the future treatment of breast cancer.

Apoptin Regulates Apoptosis and Autophagy by Modulating Reactive Oxygen Species (ROS) Levels in Human Liver Cancer Cells.

Apoptin is a protein that specifically induces apoptosis in tumor cells. The anti-tumorigenic functions of Apoptin, including autophagy activation and its interaction with apoptosis, have not been precisely elucidated. Here we investigate the main pathways of apoptin-mediated killing of human liver cancer cells, as well as its putative role in autophagy and apoptosis. The anti-proliferative effect of apoptin in liver cancer cells was analyzed in vitro by crystal violet staining and MTS detection, and also in vivo using a tumor-based model. The main pathway related to apoptin-induced growth inhibition in vitro was evaluated by flow cytometry and fluorescence staining. The relationship between apoptosis and autophagy on apoptin-treating cells was analyzed using apoptosis and autophagy inhibitors, mitochondrial staining, Annexin V-FITC/PI flow detection, LC3 staining, and western blotting. The effect of ROS toward the apoptosis and autophagy of apoptin-treating cells was also evaluated by ROS detection, Annexin V-FITC/PI flow detection, LC3 staining, and western blotting. Inhibition of apoptosis in apoptin-treating liver cancer cells significantly reduced the autophagy levels in vitro. The overall inhibition increased from 12 h and the effect was most obvious at 48 h. Inhibition of autophagy could increase apoptin-induced apoptosis of cells in a time-dependent manner, reaching its peak at 24 h. Apoptin significantly alters ROS levels in liver cancer cells, and this effect is directly related to apoptosis and autophagy. ROS appears to be the key factor linking apoptin-induced autophagy and apoptosis through the mitochondria in liver cancer cells. Therefore, evaluating the interaction between apoptin-induced apoptosis and autophagy is a promising step for the development of alternate tumor therapies.

Inhibition of HMGB1 Overcomes Resistance to Radiation and Chemotherapy in Nasopharyngeal Carcinoma.

OBJECTIVE: This study aimed to investigate the effect of high mobility group protein B1 (HMGB1) on chemoresistance and radioresistance in nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: HMGB1-knockout HK1 cell lines were generated using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) system. Western blotting was used to evaluate the protein expression level of HMGB1. DNA repair efficiency of non-homologous end joining (NHEJ) and homologous recombination (HR) was monitored through NHEJ and HR reporter assay. Cellular protein-protein interaction between HMGB1 and NHEJ apparatus was determined by immunoprecipitation. Direct protein-protein interaction was examined by affinity capture assay with purified protein. Protein-DNA binding was evaluated by chromatin fractionation assay. Cell viability assay was employed to measure cell sensitivity to ionizing radiation (IR) or cisplatin. RESULTS: HMGB1-knockout NPC cells showed significant decrease in NHEJ efficiency. HMGB1 immunoprecipitated NHEJ key factors in NPC cells and promoted DNA-binding activity of Ku70. Mutational analysis revealed that serine 155 of Ku70 was required for its direct interaction with HMGB1. HMGB1 was highly expressed in radio- and chemoresistant NPC cells. Deficiency of HMGB1 sensitized wild-type (WT) and resistant NPC cells to IR and cisplatin. Glycyrrhizin, which is HMGB1 inhibitor, impaired DNA binding of HMGB1 and exhibited excellent synergy with IR and cisplatin. CONCLUSION: HMGB1 promotes NHEJ via interaction with Ku70 resulting in resistance to IR and cisplatin. Inhibition of HMGB1 by glycyrrhizin is a potential therapeutic regimen to treat cisplatin and IR resistant NPC patients.

Association analysis of high-mobility group box-1 protein 1 (HMGB1)/toll-like receptor (TLR) 4 with nasal interleukins in allergic rhinitis patients.

BACKGROUND: High mobility group box 1 (HMGB1) acts as an inflammatory mediator initiator, and has shown to increase in nasal secretions of allergic rhinitis (AR) patients. The purpose of the present study was to investigate the association of HMGB1 and its receptor, toll-like receptor (TLR) 4 with proinflammatory interleukins in AR patients. METHODS: The interleukin (IL) -4, -5, -13, -17A, -10 in nasal lavage fluid and the serum IgE were examined with enzyme-linked immunosorbent assay (ELISA) in 125 AR patients or 87 healthy subjects (as control). The mRNA levels of HMGB1, receptor for advanced glycation end products (RAGE) and TLR 2, 3 and 4 were examined in these participants with real-time quantitative PCR (RT-qPCR) method. Spearman rank correlation was adopted to analyze the relationship between any two factors of clinical characteristics and laboratory-examined biomarkers. RESULTS: IL-4, -5, -13 and -17A were significantly higher, whereas IL-10 was markedly lower in the nasal lavage fluid samples from AR patients, compared with the control subjects. High expression of HMGB1, TLR2 and TLR4 were observed in the nasal brushing samples from these AR patients, whereas there was no significant difference for the mRNA levels of TLR3 and RAGE. Besides, HMGB1/TLR4 mRNA levels correlated positively with IL-4, -5, -13 and -17A, whereas negatively with IL-10. A linear regression of HMGB1/TLR4 was also found positively with IL-4, -5 (only for TLR4), -13 or -17A, whereas negatively with IL-10. CONCLUSION: High mRNA levels of HMGB1 and TLR4 were found in the nasal brushing samples in AR patients, correlating positively with IL-4, -5, -13 or -17A, wheareas negatively with IL-10. HMGB1/TLR4 signaling pathway might be well responsive targets as immunotherapy for allergic rhinitis.