Oncolytic vesicular stomatitis virus modulates invadopodia morphology and inhibits invasive behaviors in Src-transformed fibroblasts

Vesicular stomatitis virus (VSV) preferentially kills tumor cells, but its effects on invasive cancer cell behavior is less clear. Invadopodia are actin-dense, cell surface protrusions with extracellular matrix-remodeling proteolytic activity that facilitate invasive processes within the metastatic cascade. Previous studies have shown that VSV can manipulate the host cell cytoskeleton in order to potentiate viral infection. We therefore hypothesized that VSV infection would alter invadopodia and thereby compromise invasive cell behavior. We tested the impact of VSV infection on Src-transformed NIH3T3 (Src3T3) fibroblasts, a highly invasive cancer cell line similar to those first used in invadopodia studies. We also compared the effects of wild-type VSV (rwt virus) versus a matrix (M) protein mutant strain (rM51R-M virus) capable of inducing host antiviral responses. Infection with either strain caused a 4-fold reduction in punctate invadopodia, but a 4-fold increase in rosette-shaped invadopodia-like superstructures. This coincided with a reduction in invadopodia-associated gelatin degradation activity by nearly 70%. Src3T3 cell invasion was also inhibited by both viral strains, including at a low multiplicity of infection (e.g., rM51R-M virus inhibited invasion by 66% at an MOI of 0.1 pfu/cell). Importantly, these effects on Src3T3 invasive behavior occurred alongside active viral replication, and at a time and MOI where cells were minimally impacted by VSV-induced cell death (e.g., rM51R-M virus inhibited viability by 2% at an MOI of 0.1 pfu/cell). This study highlights VSV as a potent antagonist of cell invasion and provides insights into additional mechanisms employed by oncolytic VSV strains to perturb tumor progression.