Synergistic antitumour effects of rapamycin and oncolytic reovirus

Area of Science:

• Oncology
• Virology
• Immunology

Background:

• Oncolytic viruses are a promising cancer treatment modality, with one agent approved for malignant melanoma.
• Current research focuses on combining oncolytic viruses with conventional therapies or agents that enhance viral replication and oncolysis.
• The mTOR pathway is a potential target for enhancing oncolytic virus efficacy.

Purpose of the Study:

• To evaluate the combination of reovirus and rapamycin in a murine model of malignant melanoma (B16F10 cells).
• To investigate the mechanisms by which mTOR inhibitors, specifically rapamycin, might enhance viral oncolysis.
• To assess the impact of rapamycin on reovirus replication, cell cycle, apoptosis, and anti-viral immune response.

Main Methods:

• Combination therapy of reovirus and rapamycin was tested in B16F10 melanoma cells and C57/black 6 mice.
• Viral replication, cell cycle progression, and apoptosis (Annexin V/PI, caspase 3/7 activation) were analyzed.
• Antireovirus-neutralizing antibody responses were measured in mice.

Main Results:

• Rapamycin did not affect the generation of anti-reovirus antibodies in mice.
• Rapamycin did not alter the cell cycle effects of reovirus.
• Rapamycin attenuated viral replication and reduced reovirus-induced apoptosis when administered prior to or concurrently with reovirus.
• Synergistic antitumor effects were observed for the reovirus-rapamycin combination both in vitro and in vivo, with sequence-dependent efficacy in vitro.

Conclusions:

• The combination of reovirus and rapamycin demonstrates synergistic antitumor efficacy in preclinical models of melanoma.
• Rapamycin's inhibitory effect on viral replication and apoptosis does not preclude its beneficial combination with reovirus for enhanced antitumor activity.
• Further investigation into this combination therapy is warranted for cancer treatment.