Antitumor efficacy of CRISPR/Cas9-engineered ICP6 mutant herpes simplex viruses in a mouse xenograft model for lung adenocarcinoma
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Longquan Ni1,2, Yi Li3, Ke Wu1,2
1State Key Laboratory of Virology and National Virus Resource Center, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
Abstract:
Oncolytic viruses (OVs), including oncolytic herpes simplex viruses (oHSVs), are promising therapeutics against cancer. Here, we report two ICP6-mutated HSVs (type I) generated by CRISPR/Cas9, rHSV1/∆RR (with ICP6 ribonucleotide reductase [RR] domain deleted) and rHSV1/∆ICP6 (with a complete deletion of ICP6), exhibiting potent antitumor efficacy against lung adenocarcinoma. Both the mutants showed strong cytotoxicity in vitro, comparable with the control viruses expressing intact ICP6, but in relatively lower titers. Moreover, these mutant viruses exhibited preferential killing ability against lung tumor cells rather than normal lung fibroblast cells. Further, unlike the control HSV-1 causing severe illness or death in the mouse model, the ICP6-mutated viruses did not induce significant pathogenicity but instead effectively reduced tumor burden in vivo and led to 100% survival of the animals, indicating notable antitumor activity and attenuated virulence. In addition, rHSV1/∆RR seemed to have even better antitumor efficacy than rHSV1/∆ICP6, albeit no statistical significance in inhibition of tumor volume. Histopathologically, rHSV1/∆RR induced massive neutrophil infiltration to the tumor microenvironment and consistently, triggered more antitumor immune and neutrophil chemotactic cytokines or higher expression levels of them (indicated by quantitative polymerase chain reaction and transcriptome analyses). These results demonstrate the anti-adenocarcinoma potential of the CRISPR/Cas9-engineered ICP6 mutant HSV1, especially the rHSV1/∆RR, which likely induces stronger innate antitumor immune response. Together, these findings may provide new valuable clues for further development of OV-based therapeutics against lung adenocarcinoma or other types of tumors.
Insights
CRISPR/Cas9-engineered ICP6 mutant herpes simplex viruses (HSVs) show potent antitumor effects against lung cancer. These modified viruses effectively reduced tumors and increased survival in mice with minimal pathogenicity.
Area of Science:
- Oncolytic virotherapy
- Cancer research
- Viral oncology
Background:
- Oncolytic viruses (OVs), specifically oncolytic herpes simplex viruses (oHSVs), represent a promising avenue for cancer treatment.
- Herpes simplex virus type 1 (HSV-1) ICP6 gene is crucial for viral replication and virulence.
Purpose of the Study:
- To engineer and evaluate ICP6-mutated HSV-1 strains for enhanced oncolytic efficacy and reduced pathogenicity against lung adenocarcinoma.
- To investigate the antitumor mechanisms of these engineered viruses, focusing on immune responses.
Main Methods:
- CRISPR/Cas9 gene editing was used to create two ICP6-mutated HSV-1 strains: rHSV1/∆RR (deleted ICP6 ribonucleotide reductase domain) and rHSV1/∆ICP6 (complete ICP6 deletion).
- In vitro cytotoxicity assays were performed on lung tumor cells and normal lung fibroblasts.
- In vivo antitumor efficacy and pathogenicity were assessed using a mouse model of lung adenocarcinoma.
- Quantitative polymerase chain reaction and transcriptome analyses were employed to study cytokine expression and immune responses.
Main Results:
- Both ICP6-mutated HSVs demonstrated significant in vitro cytotoxicity against lung tumor cells and preferential killing compared to normal cells.
- In vivo studies showed that the mutant viruses effectively reduced tumor burden and led to 100% survival in mice, with significantly attenuated pathogenicity compared to wild-type HSV-1.
- The rHSV1/∆RR mutant exhibited potent antitumor activity, potentially by inducing a stronger innate antitumor immune response characterized by neutrophil infiltration and elevated cytokine levels.
Conclusions:
- CRISPR/Cas9-engineered ICP6 mutant HSV-1, particularly rHSV1/∆RR, holds significant potential as an oncolytic therapeutic for lung adenocarcinoma.
- These mutants offer a favorable safety profile with potent antitumor efficacy, likely mediated by enhanced innate immune responses.
- The findings provide valuable insights for the development of novel oncolytic virus-based therapies for various cancers.
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