Recombinant adenoviruses expressing apoptin suppress the growth of MCF‑7 breast cancer cells and affect cell autophagy

Apoptin Inhibits Glycolysis and Regulates Autophagy by Targeting Pyruvate Kinase M2 (PKM2) in Lung Cancer A549 Cells

BACKGROUND

Pyruvate kinase M2 (PKM2) is a key enzyme in aerobic glycolysis and plays an important role in tumor energy metabolism and tumor growth. Ad-apoptin, a recombinant oncolytic adenovirus, can stably express apoptin in tumor cells and selectively causes cell death in tumor cells.

OBJECTIVE

The relationship between the anti-tumor function of apoptin, including apoptosis and autophagy activation, and the energy metabolism of tumor cells has not been clarified.

METHODS

In this study, we used the A549 lung cancer cell line to analyze the mechanism of PKM2 involvement in apoptin-mediated cell death in tumor cells. PKM2 expression in lung cancer cells was detected by Western blot and qRT-PCR. In the PKM2 knockdown and over-expression experiments, A549 lung cancer cells were treated with Ad-apoptin, and cell viability was determined by the CCK-8 assay and crystal violet staining. Glycolysis was investigated using glucose consumption and lactate production experiments. Moreover, the effects of Ad-apoptin on autophagy and apoptosis were analyzed by immunofluorescence using the Annexin v-mCherry staining and by western blot for c-PARP, p62, and LC3-II proteins. Immunoprecipitation analysis was used to investigate the interaction between apoptin and PKM2. In addition, following PKM2 knockdown and overexpression, the expression levels of p-AMPK, p-mTOR, p-ULK1, and p-4E-BP1 proteins in Ad-apoptin treated tumor cells were analyzed by western blot to investigate the mechanism of apoptin effect on the energy metabolism of tumor cells. The in vivo antitumor mechanism of apoptin was analyzed by xenograft tumor inhibition experiment in nude mice and immunohistochemistry of tumors' tissue.

RESULTS

As a result, apoptin could target PKM2, inhibit glycolysis and cell proliferation in A549 cells, and promote autophagy and apoptosis in A549 cells by regulating the PKM2/AMPK/mTOR pathway.

CONCLUSION

This study confirmed the necessary role of Ad-apoptin in the energy metabolism of A549 cells.

Oncolytic viruses-modulated immunogenic cell death, apoptosis and autophagy linking to virotherapy and cancer immune response

Recent reports have revealed that oncolytic viruses (OVs) play a significant role in cancer therapy. The infection of OVs such as oncolytic vaccinia virus (OVV), vesicular stomatitis virus (VSV), parvovirus, mammalian reovirus (MRV), human adenovirus, Newcastle disease virus (NDV), herpes simplex virus (HSV), avian reovirus (ARV), Orf virus (ORFV), inactivated Sendai virus (ISV), enterovirus, and coxsackievirus offer unique opportunities in immunotherapy through diverse and dynamic pathways. This mini-review focuses on the mechanisms of OVs-mediated virotherapy and their effects on immunogenic cell death (ICD), apoptosis, autophagy and regulation of the immune system.

Apoptin mediates mitophagy and endogenous apoptosis by regulating the level of ROS in hepatocellular carcinoma

Background

Apoptin, as a tumor-specific pro-apoptotic protein, plays an important anti-tumoral role, but its mechanism of autophagy activation and the interaction between autophagy and apoptosis have not been accurately elucidated. Here, we studied the mechanism of apoptin-induced apoptosis and autophagy and the interaction between two processes.

Methods

Using crystal violet staining and the CCK-8 assay, we analyzed the effect of apoptin in the inhibition of liver cancer cells in vitro and analyzed the effect of inhibiting liver cancer in vivo by establishing a nude mouse tumor model. Flow cytometry and fluorescence staining were used to analyze the main types of apoptin-induced apoptosis and autophagy. Subsequently, the relationship between the two events was also analyzed. Flow cytometry was used to analyze the effect of ROS on apoptin-mediated apoptosis and autophagy mediated by apoptin. The effect of ROS on two phenomena was analyzed. Finally, the role of key genes involved in autophagy was analyzed using gene silencing.

Results

The results showed that apoptin can significantly increase the apoptosis and autophagy of liver cancer cells, and that apoptin can cause mitophagy through the increase in the expression of NIX protein. Apoptin can also significantly increase the level of cellular ROS, involved in apoptin-mediated autophagy and apoptosis of liver cancer cells. The change of ROS may be a key factor causing apoptosis and autophagy.

Conclusion

The above results indicate that the increase in ROS levels after apoptin treatment of liver cancer cells leads to the loss of mitochondrial transmembrane potential, resulting in endogenous apoptosis and mitophagy through the recruitment of NIX. Therefore, ROS may be a key factor connecting endogenous apoptosis and autophagy induced by apoptin in liver cancer cells.

Graphical abstract

Ad-VT enhances the sensitivity of chemotherapy-resistant lung adenocarcinoma cells to gemcitabine and paclitaxel in vitro and in vivo

Background One of the main challenges in the clinical treatment of lung cancer is resistance to chemotherapeutic drugs. P-glycoprotein (P-gp)-mediated drug resistance is the main obstacle to successfully implementing microtubule-targeted tumor chemotherapy. Purpose In this study, we explored the effect of Ad-hTERTp-E1a-Apoptin (Ad-VT) on drug-resistant cell lines and the molecular mechanism by which Ad-VT combined with chemotherapy affects drug-resistant cells and parental cells. Methods In vitro, cell proliferation, colony formation, resistance index (RI), apoptosis and autophagy assays were performed. Protein expression was analyzed by Western blotting. Finally, a xenograft tumor model in nude mice was used to detect tumor growth and evaluate histological characteristics. Results Our results showed that Ad-VT had an obvious killing effect on A549, A549/GEM and A549/Paclitaxel cancer cells, and the sensitivity of drug-resistant cell lines to Ad-VT was significantly higher than that of parental A549 cells. Compared with A549 cells, A549/GEM and A549/Paclitaxel cells had higher autophagy levels and higher viral replication ability. Ad-VT decreased the levels of p-PI3k, p-Akt and p-mTOR and the expression of P-gp. In vivo, Ad-VT combined with chemotherapy can effectively inhibit the growth of chemotherapy-resistant tumors and prolong the survival of mice. Conclusions Thus, the combination of Ad-VT and chemotherapeutic drugs will be a promising strategy to overcome chemoresistance.

Ad-Apoptin-hTERTp-E1a Regulates Autophagy Through the AMPK-mTOR-eIF4F Signaling Axis to Reduce Drug Resistance of MCF-7/ADR Cells

Ad-VT (Ad-Apoptin-hTERTp-E1a) is a type of oncolytic adenovirus with dual specific tumor cell death ability. It can effectively induce cell death of breast cancer cells and has better effect when used in combination with chemotherapy drugs. However, it has not been reported whether Ad-VT reduces the resistance of breast cancer cells to chemotherapy drugs. The purpose of this study is to investigate the effect of Ad-VT on drug resistance of Adriamycin-resistant breast cancer cells. For this, the effects of different doses of Ad-VT on the resistance of breast cancer cells to Adriamycin were analyzed using qualitative and quantitative experiments in vitro and in vivo. The Ad-VT can reduce the resistance of MCF-7/ADR to adriamycin, which is caused by the reduction of MRP1 protein level in MCF-7/ADR cells after treatment with Ad-VT, and MRP1 can be interfered with by autophagy inhibitors. Subsequently, the upstream signal of autophagy was analyzed and it was found that Ad-VT reduced the resistance of cells to doxorubicin by reducing the level of mTOR, and then the analysis of the upstream and downstream proteins of mTOR found that Ad-VT increased the sensitivity of MCF-7/ADR cells to adriamycin by activating AMPK-mTOR-eIF4F signaling axis. Ad-VT can not only significantly induce cell death in MCF-7/ADR cells, but also improved their sensitivity to Adriamycin. Therefore, the combination of Ad-VT and chemotherapy drugs may become a new strategy for the treatment of breast cancer in overcoming Adriamycin resistance.

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.

Development of oncolytic virotherapy: from genetic modification to combination therapy

Oncolytic virotherapy (OVT) is a novel form of immunotherapy using natural or genetically modified viruses to selectively replicate in and kill malignant cells. Many genetically modified oncolytic viruses (OVs) with enhanced tumor targeting, antitumor efficacy, and safety have been generated, and some of which have been assessed in clinical trials. Combining OVT with other immunotherapies can remarkably enhance the antitumor efficacy. In this work, we review the use of wild-type viruses in OVT and the strategies for OV genetic modification. We also review and discuss the combinations of OVT with other immunotherapies.