MAP3K7 and CHD1 Are Novel Mediators of Resistance to Oncolytic Vesicular Stomatitis Virus in Prostate Cancer Cells

ABSTRACT Oncolytic virotherapy represents a promising experimental anticancer strategy, based on the use of genetically modified viruses to selectively infect and kill cancer cells. Vesicular stomatitis virus (VSV) is a prototypic oncolytic virus (OV) that induces cancer cell death through activation of the apoptotic pathway, although intrinsic resistance to oncolysis is found in some cell lines and many primary tumors, as a consequence of residual innate immunity to the virus. In the effort to improve OV therapeutic efficacy, we previously demonstrated that different agents, including histone deacetylase inhibitors (HDIs), functioned as reversible chemical switches to dampen the innate antiviral response and improve the susceptibility of resistant cancer cells to VSV infection. In the present study, we demonstrated that the NAD+-dependent histone deacetylase SIRT1 (silent mating type information regulation 2 homolog 1) plays a key role in the permissivity of prostate cancer PC-3 cells to VSVΔM51 replication and oncolysis. HDI-mediated enhancement of VSVΔM51 infection and cancer cell killing directly correlated with a decrease of SIRT1 expression. Furthermore, pharmacological inhibition as well as silencing of SIRT1 by small interfering RNA (siRNA) was sufficient to sensitize PC-3 cells to VSVΔM51 infection, resulting in augmentation of virus replication and spread. Mechanistically, HDIs such as suberoylanilide hydroxamic acid (SAHA; Vorinostat) and resminostat upregulated the microRNA miR-34a that regulated the level of SIRT1. Taken together, our findings identify SIRT1 as a viral restriction factor that limits VSVΔM51 infection and oncolysis in prostate cancer cells. IMPORTANCE The use of nonpathogenic viruses to target and kill cancer cells is a promising strategy in cancer therapy. However, many types of human cancer are resistant to the oncolytic (cancer-killing) effects of virotherapy. In this study, we identify a host cellular protein, SIRT1, that contributes to the sensitivity of prostate cancer cells to infection by a prototypical oncolytic virus. Knockout of SIRT1 activity increases the sensitivity of prostate cancer cells to virus-mediated killing. At the molecular level, SIRT1 is controlled by a small microRNA termed miR-34a. Altogether, SIRT1 and/or miR-34a levels may serve as predictors of response to oncolytic-virus therapy.

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Early Steps of the Virus Replication Cycle Are Inhibited in Prostate Cancer Cells Resistant to Oncolytic Vesicular Stomatitis Virus

Journal of Virology ◽

10.1128/jvi.01508-08 ◽

2008 ◽

Vol 82 (24) ◽

pp. 12104-12115 ◽

Cited By ~ 37

Author(s):

Brooke L. Carey ◽

Maryam Ahmed ◽

Shelby Puckett ◽

Douglas S. Lyles

Keyword(s):

Prostate Cancer ◽

Cancer Cells ◽

Tumor Cells ◽

Vesicular Stomatitis Virus ◽

Virus Replication ◽

Oncolytic Virus ◽

Lncap Cells ◽

Prostate Cancer Cells ◽

Pc3 Cells ◽

Vesicular Stomatitis

ABSTRACT Vesicular stomatitis virus (VSV) is currently being studied as a candidate oncolytic virus for tumor therapies due to its potent tumoricidal activity. Previous studies have demonstrated that VSV selectively infects tumor cells due to defects in their antiviral pathways. These defects make them more susceptible to VSV-induced killing than normal cells. However, some cancer cells display differential sensitivity to VSV. Specifically, LNCaP prostate cancer cells are sensitive to infection with VSV, while PC3 prostate cancer cells are relatively resistant to VSV. This suggests that tumor cells vary in the extent to which they develop defects in antiviral pathways and, thus, permit virus replication. The goal of these studies was to identify the step(s) of the viral replication cycle that is inhibited in PC3 cells. Results showed that although attachment of VSV was not significantly different among cell types, penetration was delayed by 10 to 30 min in PC3 cells relative to LNCaP cells. Primary transcription was delayed by 6 to 8 h in PC3 cells relative to LNCaP cells. Similarly, both secondary transcription and viral protein synthesis rates were delayed by about 6 to 8 h. The progressively increasing delay suggests that more than one step is affected in PC3 cells. Analysis of cellular gene expression showed that in contrast to LNCaP cells, PC3 cells constitutively expressed numerous antiviral gene products, which may enhance their resistance to VSV. These data indicate that the use of VSV for oncolytic virus therapy for prostate tumors may require prescreening of tumors for their level of susceptibility.

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