Suppression of autophagic genes sensitizes CUG2-overexpressing A549 human lung cancer cells to oncolytic vesicular stomatitis virus-induced apoptosis

Abstract

Abstract. We showed in our previous study that cancer upregulated gene (CUG) 2, a novel oncogene, confers resistance to infection of oncolytic vesicular stomatitis virus (VSV) by activating Stat1-mediated signal transduction. Since many studies have reported that autophagy is involved in virus replication, we investigated whether autophagy also plays a role in the antiviral activity in A549 cells overexpressing CUG2 (A549-CUG2). We suppressed Atg5 or Beclin 1 expression using siRNA and examined its effect on the susceptibility of cells to infection by oncolytic VSV. We found that A549-CUG2 cells treated with Atg5 or Beclin 1 siRNA became susceptible to VSV infection, whereas A549-CUG2 cells treated with control siRNA were resistant. This result suggests that autophagy is involved in the antiviral response of A549-CUG2 cells. Further investigation revealed that autophagy impairment enhanced the generation of reactive oxygen species (ROS), which resulted in inactivation of S6 kinase. Under these conditions, the levels of ISG15 transcript and protein decreased, which conferred on A549-CUG2 cell susceptibility to VSV infection. Finally, we found that overloading of H 2 O 2 sensitized control A549-CUG2 cells to VSV-induced apoptosis. Taken together, these results indicate that autophagy impairment induces excessive ROS formation, which decreases S6 kinase activity and ISG15 expression, ultimately rendering the A549-CUG2 cells susceptible to VSV infection. We propose that autophagy impairment is a potential strategy for successful VSV virotherapy of CUG2-overexpressing tumors.

Overexpression of Smac by an Armed Vesicular Stomatitis Virus Overcomes Tumor Resistance

“…Our results revealed that endogenous Smac was diminished when HeLa cells were infected by wtVSV for 24 hr. The exact mechanisms of inhibition remain to be determined, but VSV has been shown to activate autophagy and ubiquitination to inhibit apoptosis 41, 42, 43. On the other hand, the level of Smac in HeLa cells was maintained or enhanced throughout the 24-hr course of VSV-S infection (Figure 2).…”

Recent advances in vesicular stomatitis virus-based oncolytic virotherapy: a 5-year update

“…Interestingly, suppressing autophagy genes (Atg5 or Beclin-1) by siRNA increased reactive oxygen species formation and decreased ISG15 expression, which sensitized CUG2-overexpressing A549 human lung cancer cells to VSV-induced apoptosis. Chemical agents targeting autophagy genes such as Atg5 and Beclin-1 would be promising for CUG2-overexpressing cancers [93]. Another novel target is Livin, which is a member of the inhibitors of the apoptosis family.…”

Investigating CENPW as a Novel Biomarker Correlated With the Development and Poor Prognosis of Breast Carcinoma

“…Centromeric protein W (CENPW), also known as cancer upregulated gene 2 (CUG2) protein, is overexpressed in multiple tumor tissues, including cervical, colon, liver, and lung cancers (Malilas et al, 2014). The CENPW is located at human chromosome 6q22.32 and is regulated by the upstream TSS region, which can transcribe a full-length mRNA of 600 bp (Lee et al, 2007).…”