Vesicular stomatitis virus (VSV) is a prototypic nonsegmented negative-strand RNA virus. VSV’s broad cell tropism makes it a popular model virus for many basic research applications. In addition, a lack of preexisting human immunity against VSV, inherent oncotropism and other features make VSV a widely used platform for vaccine and oncolytic vectors. However, VSV’s neurotropism that can result in viral encephalitis in experimental animals needs to be addressed for the use of the virus as a safe vector. Therefore, it is very important to understand the determinants of VSV tropism and develop strategies to alter it. VSV glycoprotein (G) and matrix (M) protein play major roles in its cell tropism. VSV G protein is responsible for VSV broad cell tropism and is often used for pseudotyping other viruses. VSV M affects cell tropism via evasion of antiviral responses, and M mutants can be used to limit cell tropism to cell types defective in interferon signaling. In addition, other VSV proteins and host proteins may function as determinants of VSV cell tropism. Various approaches have been successfully used to alter VSV tropism to benefit basic research and clinically relevant applications.

Vesicular stomatitis virus (VSV) is an effective oncolytic virus against most human pancreatic ductal adenocarcinoma (PDAC) cell lines. However, some PDAC cell lines are highly resistant to oncolytic VSV-ΔM51 infection. To better understand the mechanism of resistance, we tested a panel of 16 small molecule inhibitors of different cellular signaling pathways, and identified TPCA-1 (IKK-β inhibitor) and ruxolitinib (JAK1/2 inhibitor), as strong enhancers of VSV-ΔM51 replication and virus-mediated oncolysis in all VSV-resistant PDAC cell lines. Both TPCA-1 and ruxolitinib similarly inhibited STAT1 and STAT2 phosphorylation and decreased expression of antiviral genes MxA and OAS. Moreover, an in situ kinase assay provided biochemical evidence that TPCA-1 directly inhibits JAK1 kinase activity. Together, our data demonstrate that TPCA-1 is a unique dual inhibitor of IKK-β and JAK1 kinase, and provide a new evidence that upregulated type I interferon signaling plays a major role in resistance of pancreatic cancer cells to oncolytic viruses.

O-mannosylated α-dystroglycan (α-DG) serves as receptors for cell–cell and cell–extracellular matrix adhesion and signaling. Hypoglycosylation of α-DG is involved in cancer progression and underlies dystroglycanopathy with aberrant neuronal development. Here we report that ribitol, a pentose alcohol with previously unknown function in mammalian cells, partially restores functional O-mannosylation of α-DG (F-α-DG) in the dystroglycanopathy model containing a P448L mutation in fukutin-related protein (FKRP) gene, which is clinically associated with severe congenital muscular dystrophy. Oral administration of ribitol increases levels of ribitol-5-phosphate and CDP-ribitol and restores therapeutic levels of F-α-DG in skeletal and cardiac muscles. Furthermore, ribitol, given before and after the onset of disease phenotype, reduces skeletal muscle pathology, significantly decreases cardiac fibrosis and improves skeletal and respiratory functions in the FKRP mutant mice. Ribitol treatment presents a new class, low risk, and easy to administer experimental therapy to restore F-α-DG in FKRP-related muscular dystrophy.

Vesicular stomatitis virus (VSV) based recombinant viruses (such as VSV-ΔM51) are effective oncolytic viruses (OVs) against a majority of pancreatic ductal adenocarcinoma (PDAC) cell lines. However, some PDAC cell lines are highly resistant to VSV-ΔM51. We recently showed that treatment of VSV-resistant PDAC cells with ruxolitinib (JAK1/2 inhibitor) or TPCA-1 (IKK-β inhibitor) breaks their resistance to VSV-ΔM51. Here we compared the global effect of ruxolitinib or TPCA-1 treatment on cellular gene expression in PDAC cell lines highly resistant to VSV-ΔM51. Our study identified a distinct subset of 22 interferon-stimulated genes (ISGs) downregulated by both ruxolitinib and TPCA-1. Further RNA and protein analyses demonstrated that 4 of these genes (MX1, EPSTI1, XAF1, and GBP1) are constitutively co-expressed in VSV-resistant, but not in VSV-permissive PDACs, thus serving as potential biomarkers to predict OV therapy success. Moreover, shRNA-mediated knockdown of one of such ISG, MX1, showed a positive effect on VSV-ΔM51 replication in resistant PDAC cells, suggesting that at least some of the identified ISGs contribute to resistance of PDACs to VSV-ΔM51. As certain oncogene and tumor suppressor gene variants are often associated with increased tropism of OVs to cancer cells, we also analyzed genomic DNA in a set of PDAC cell lines for frequently occurring cancer associated mutations. While no clear correlation was found between such mutations and resistance of PDACs to VSV-ΔM51, the analysis generated valuable genotypic data for future studies.