Multi-Omics Analysis of Glioblastoma Cells' Sensitivity to Oncolytic Viruses

Simple Summary

This study aims to uncover the contribution of interferon-dependent antiviral mechanisms preserved in tumor cells to the resistance of glioblastoma multiforme cells to oncolytic viruses. To characterize the functionality of interferon signaling, we used omics profiling and titration-based measurements of cell sensitivity to a panel of viruses of diverse oncolytic potential. This study shows why patient-derived glioblastoma cultures can acquire increased resistance to oncolytic viruses in the presence of interferons and suggests an approach to ranking glioblastoma cells by the acquired resistance. Our findings are important for monitoring the oncolytic potential of viruses to overcome IFN-induced resistance of tumor cells and contribute to successful therapy.

Abstract

Oncolytic viruses have gained momentum in the last decades as a promising tool for cancer treatment. Despite the progress, only a fraction of patients show a positive response to viral therapy. One of the key variable factors contributing to therapy outcomes is interferon-dependent antiviral mechanisms in tumor cells. Here, we evaluated this factor using patient-derived glioblastoma multiforme (GBM) cultures. Cell response to the type I interferons’ (IFNs) stimulation was characterized at mRNA and protein levels. Omics analysis revealed that GBM cells overexpress interferon-stimulated genes (ISGs) and upregulate their proteins, similar to the normal cells. A conserved molecular pattern unambiguously differentiates between the preserved and defective responses. Comparing ISGs’ portraits with titration-based measurements of cell sensitivity to a panel of viruses, the “strength” of IFN-induced resistance acquired by GBM cells was ranked. The study demonstrates that suppressing a single ISG and encoding an essential antiviral protein, does not necessarily increase sensitivity to viruses. Conversely, silencing IFIT3 and PLSCR1 genes in tumor cells can negatively affect the internalization of vesicular stomatitis and Newcastle disease viruses. We present evidence of a complex relationship between the interferon response genes and other factors affecting the sensitivity of tumor cells to viruses.

Prooxidant properties of p66shc are mediated by mitochondria in human cells

p66shc is a protein product of an mRNA isoform of SHC1 gene that has a pro-oxidant and pro-apoptotic activity and is implicated in the aging process. Mitochondria were suggested as a major source of the p66shc-mediated production of reactive oxygen species (ROS), although the underlying mechanisms are poorly understood. We studied effects of p66shc on oxidative stress induced by hydrogen peroxide or by serum deprivation in human colon carcinoma cell line RKO and in diploid human dermal fibroblasts (HDFs). An shRNA-mediated knockdown of p66shc suppressed and an overexpression of a recombinant p66shc stimulated the production of ROS in the both models. This effect was not detected in the mitochondrial DNA-depleted ρ0-RKO cells that do not have the mitochondrial electron transport chain (ETC). The p66shc-dependent accumulation of mitochondrial ROS was detected with HyPer-mito, a mitochondria-targeted fluorescent protein sensor for hydrogen peroxide. The fragmentation of mitochondria induced by mitochondrial ROS was significantly reduced in the p66shc deficient RKO cells. Mitochondria-targeted antioxidants SkQ1 and SkQR1 also decreased the oxidative stress induced by hydrogen peroxide or by serum deprivation. Together the data indicate that the p66shc-dependant ROS production during oxidative stress has mitochondrial origin in human normal and cancer cells.