Targeted inflammation during oncolytic virus therapy severely compromises tumor blood flow

Area of Science:

• Oncology
• Virology
• Immunology

Background:

• Oncolytic viruses (OVs) are engineered to directly infect and lyse cancer cells.
• The direct tumor lysis mechanism may not fully explain the therapeutic efficacy of some OVs.

Purpose of the Study:

• To investigate the mechanisms underlying the in vivo anti-cancer activity of vesicular stomatitis virus (VSV) and vaccinia virus.
• To determine the role of indirect tumor cell killing and inflammatory responses in OV therapy.

Main Methods:

• Administered VSV and vaccinia virus to tumor models.
• Analyzed tumor tissues for viral infection, blood flow, apoptosis, and immune cell infiltration.
• Performed transcript profiling to identify gene expression changes.
• Depleted neutrophils to assess their role in OV efficacy.

Main Results:

• Observed significant indirect killing of uninfected tumor cells, independent of extensive viral replication.
• Identified rapid induction of apoptosis in tumor cells and loss of tumor blood flow post-OV administration.
• Found virus infection upregulated pro-inflammatory genes, attracting neutrophils to the tumor site.
• Demonstrated that neutrophil depletion abrogated indirect tumor cell killing and enhanced viral spread.

Conclusions:

• Neutrophil recruitment to OV-infected tumors plays a crucial role in eliminating uninfected malignant cells.
• The inflammatory response, particularly neutrophil infiltration, enhances the efficacy of oncolytic virus therapeutics.
• Therapeutic strategies should consider leveraging inflammatory cell activation to optimize OV treatment outcomes.