Constitutive NF-κB Activation is Amplified by VSV in Aggressive PC3 Prostate Cancer Cells that Resist Viral Oncolysis

Cancer cells often have defects in antiviral pathways, making them susceptible to oncolytic viruses like vesicular stomatitis virus (VSV). However, some cancer cells resist viral infection through the constitutive expression of interferon-stimulated genes. This study examined whether NF-κB activation and NF-κB-dependent antiviral signaling contributes to resistance to VSV infection in the PC3 cell line, derived from an aggressive metastatic prostate cancer (PrCa) tumor. We found that NF-κB localized to the nucleus in VSV-infected PC3 cells, but not in the VSV-susceptible LNCaP PrCa cell line. Analysis of the upstream NF-κB inhibitor IκB- α revealed higher levels of both total and phosphorylated IκB- α in PC3 cells compared to LNCaP cells, indicating constitutive activation of the NF-κB pathway via an IκB-α–dependent mechanism. Notably, VSV infection did not alter IκB-α phosphorylation in PC3 cells, suggesting that VSV may amplify NF-κB signaling through an IκB- α –independent pathway. Furthermore, PC3 cells displayed elevated levels of the NF-κB p65 protein subunit compared to LNCaP cells, with its phosphorylated form significantly increased upon VSV infection. These results from phosphorylation assays confirm that multiple steps in the NF-κB pathway are differentially activated in PC3 and LNCaP cells. Additionally, the expression of several NF-κB-dependent cytokine and proinflammatory genes, including IL12 and IL6, were upregulated following VSV infection in PC3 cells, as compared to LNCaP cells. Blocking the NF-κB pathway using a pharmaceutical inhibitor resulted in increased PC3 cell death with VSV infection. Collectively, these findings suggest that enhanced NF-κB signaling may underlie the resistance of PC3 cells to VSV oncolysis, potentially offering new insights into therapeutic strategies targeting NF-κB in resistant prostate cancers.