Cancer immunotherapy based on killing of Salmonella-infected tumor cells

Area of Science:

• Oncology
• Immunology
• Microbiology

Background:

• Tumor immune escape remains a significant hurdle in developing effective cancer immunotherapies.
• Targeting tumor cells as infected entities, rather than malignant ones, offers a potential strategy to overcome immune evasion.

Purpose of the Study:

• To investigate a novel cancer immunotherapy approach using in vivo tumor infection.
• To evaluate the efficacy of using attenuated Salmonella typhimurium to induce tumor cell death and anti-tumor immunity.

Main Methods:

• Attenuated Salmonella typhimurium was used to infect melanoma cells in tumor-bearing mice.
• Mice were vaccinated against Salmonella typhimurium prior to intratumoral bacterial injection.
• Tumor growth, immune cell recruitment, and long-term protection were assessed.

Main Results:

• Intratumoral Salmonella typhimurium infection, combined with anti-Salmonella vaccination, resulted in 50-100% tumor-free mice.
• This combined approach showed improved efficacy against larger tumors.
• Salmonella infection also induced indirect tumor cell toxicity via inflammatory cell recruitment and cross-presentation of tumor antigens, leading to tumor-specific immune responses.

Conclusions:

• In vivo infection of tumors with Salmonella typhimurium, coupled with vaccination, represents a promising new strategy for cancer immunotherapy.
• This approach effectively eliminates tumors and establishes long-term anti-tumor immunity, even against distant tumors.
• The dual action of direct bacterial targeting and host immune stimulation highlights the therapeutic potential of this method.