Oncolytic herpes virus with defective ICP6 specifically replicates in quiescent cells with homozygous genetic...

Area of Science:

• Oncolytic virotherapy
• Molecular virology
• Cancer biology

Background:

• Oncolytic herpes simplex viruses (HSVs) are investigated for malignant glioma treatment.
• Current HSV oncolytics rely on tumor cell cycling for replication, limiting efficacy as most tumor cells are quiescent.
• Viral ICP6 and gamma34.5 mutations are thought to confer tumor selectivity by complementing with cell cycle-dependent host factors.

Purpose of the Study:

• To investigate the replication of ICP6-defective HSVs in quiescent cells.
• To determine if ICP6-negative HSVs can replicate independently of cell cycle status in a relevant tumor model.

Main Methods:

• In vitro replication assays using quiescent murine embryonic fibroblasts from p16-deleted mice.
• In vivo intracranial inoculation of ICP6-negative HSV into p16-/- and wild-type mice brains.
• Assessment of viral replication in both quiescent and cycling cells, and in vivo tumor models.

Main Results:

• ICP6-defective HSV replicated efficiently in quiescent murine embryonic fibroblasts lacking p16.
• Significant viral replication was observed in the brains of p16-/- mice but not in wild-type mice.
• These findings demonstrate that ICP6-negative HSVs can replicate in quiescent cells with specific oncogene deletions.

Conclusions:

• ICP6-negative HSVs exhibit molecular targeting, replicating in quiescent tumor cells with specific genetic alterations (e.g., p16 deletion).
• This replication is independent of the cell cycle status of the tumor cells.
• ICP6-negative HSVs represent a promising, broadly applicable oncolytic virus strategy for cancers with specific oncogene deletions.