rApoptin induces apoptosis in human breast cancer cells via phosphorylation of Nur77 and Akt

Apoptin gene delivery by a PAMAM dendrimer modified with a nuclear localization signal peptide as a gene carrier for brain cancer therapy

In this study, we aimed to synthesize PAMAMG3 derivatives (PAMAMG3-KRRR and PAMAMG3-HKRRR), using KRRR peptides as a nuclear localization signal and introduced histidine residues into the KRRR-grafted PAMAMG3 for delivering a therapeutic, carcinoma cell-selective apoptosis gene, apoptin into human primary glioma (GBL-14) cells and human dermal fibroblasts. We examined their cytotoxicity and gene expression using luciferase activity and enhanced green fluorescent protein PAMAMG3 derivatives in both cell lines. We treated cells with PAMAMG3 derivative/apoptin complexes and investigated their intracellular distribution using confocal microscopy. The PAMAMG3-KRRR and PAMAMG3-HKRRR dendrimers were found to escape from endolysosomes into the cytosol. The JC-1 assay, glutathione levels, and Annexin V staining results showed that apoptin triggered cell death in GBL-14 cells. Overall, these findings indicated that the PAMAMG3-HKRRR/apoptin complex is a potential candidate for an effective nonviral gene delivery system for brain tumor therapy in vitro.

Viral Proteins as Emerging Cancer Therapeutics

Simple Summary

This review is focused on enlisting viral proteins from different host sources, irrespective of their origin, that may act as future cancer curatives. Unlike the viral proteins that are responsible for tumor progression, these newly emerged viral proteins function as tumor suppressors. Their ability to regulate various cell signaling mechanisms specifically in cancer cells makes them interesting candidates to explore their use in cancer therapy. The discussion about such viral components may provide new insights into cancer treatment in the absence of any adverse effects to normal cells. The study also highlights avian viral proteins as a substitute to human oncolytic viruses for their ability to evade pre-existing immunity.

Abstract

Viruses are obligatory intracellular parasites that originated millions of years ago. Viral elements cover almost half of the human genome sequence and have evolved as genetic blueprints in humans. They have existed as endosymbionts as they are largely dependent on host cell metabolism. Viral proteins are known to regulate different mechanisms in the host cells by hijacking cellular metabolism to benefit viral replication. Amicable viral proteins, on the other hand, from several viruses can participate in mediating growth retardation of cancer cells based on genetic abnormalities while sparing normal cells. These proteins exert discreet yet converging pathways to regulate events like cell cycle and apoptosis in human cancer cells. This property of viral proteins could be harnessed for their use in cancer therapy. In this review, we discuss viral proteins from different sources as potential anticancer therapeutics.

Apoptin as a Tumor-Specific Therapeutic Agent: Current Perspective on Mechanism of Action and Delivery Systems

Cancer remains one of the leading causes of death worldwide in humans and animals. Conventional treatment regimens often fail to produce the desired outcome due to disturbances in cell physiology that arise during the process of transformation. Additionally, development of treatment regimens with no or minimum side-effects is one of the thrust areas of modern cancer research. Oncolytic viral gene therapy employs certain viral genes which on ectopic expression find and selectively destroy malignant cells, thereby achieving tumor cell death without harming the normal cells in the neighborhood. Apoptin, encoded by Chicken Infectious Anemia Virus' VP3 gene, is a proline-rich protein capable of inducing apoptosis in cancer cells in a selective manner. In normal cells, the filamentous Apoptin becomes aggregated toward the cell margins, but is eventually degraded by proteasomes without harming the cells. In malignant cells, after activation by phosphorylation by a cancer cell-specific kinase whose identity is disputed, Apoptin accumulates in the nucleus, undergoes aggregation to form multimers, and prevents the dividing cancer cells from repairing their DNA lesions, thereby forcing them to undergo apoptosis. In this review, we discuss the present knowledge about the structure of Apoptin protein, elaborate on its mechanism of action, and summarize various strategies that have been used to deliver it as an anticancer drug in various cancer models.

The Effects of Interleukin-33 (IL-33) on Osteosarcoma Cell Viability, Apoptosis, and Epithelial-Mesenchymal Transition are Mediated Through the PI3K/AKT Pathway

Background

Osteosarcoma is the most common primary tumor of bone. Interleukin-33 (IL-33) is a pro-inflammatory cytokine that also participates in tumor progression. This study aimed to investigate the role of IL-33 in human osteosarcoma cell viability, proliferation, apoptosis, and epithelial-mesenchymal transition (EMT) in vitro and the molecular mechanisms involved.

Material/Methods

The normal osteoblast cell line, hFOB 1.19, and the human osteosarcoma cell lines SOSP-9607, SAOS2, MG63, and U2OS were studied. The expression of IL-33 mRNA and protein in human osteosarcoma cell lines were detected using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. The effects of IL-33 on human osteosarcoma cell viability, apoptosis, EMT, and the signaling pathways were studied using the MTT assay, flow cytometry, qRT-PCR, and Western blot.

Results

IL-33 was upregulated in human osteosarcoma cell lines, including U2OS cells. The use of an IL-33 gene plasmid promoted osteosarcoma cell viability, inhibited cell apoptosis, increased the expression of Bcl-2, and reduced the expression of Bax. IL-33 reduced the level of E-cadherin and increased the levels of N-cadherin and matrix metalloproteinase-9 (MMP-9) in osteosarcoma cells at the mRNA and protein level. The use of the IL-33 plasmid increased the protein expression levels of p-AKT and the p-AKT/AKT ratio in osteosarcoma cells, and IL-33 siRNA reversed these findings.

Conclusions

IL-33 was highly expressed in human osteosarcoma cells. Down-regulation of IL-33 reduced cell viability and EMT of osteosarcoma cells, and induced cell apoptosis through activation of the PI3K/AKT signaling pathway.