Cancer immunotherapy, which uses the body’s immune system to destroy tumor cells, is particularly effective in tumors in an immune-infiltrated hot state. Only a minority of tumors are hot, however, limiting the number of people who can benefit from immunotherapies.

The researchers injected seasonal flu vaccine without synthetic adjuvants, which are compounds that enhance immune response, directly into tumors in mice. Monitoring indicators of tumor immune sensitivity, the authors found that cold tumors injected with the vaccine experienced systemic immune responses and sensitivity to treatments that block tumors’ antiimmune defenses.

The results suggest that the tumors had become hot, and that the injection had the additional benefit of conferring protection against influenza.

Similar injection of flu vaccine with a synthetic adjuvant resulted in a different response, in which mice were protected from influenza, but the tumors’ antiimmune defenses remained in place. Removal of the adjuvant or depletion of immune-suppressive tumor B cells restored the vaccine’s proimmune effect on tumors.

According to the authors, antipathogen vaccines may find additional benefit as cancer immunotherapies and, by virtue of their safety profiles and Food and Drug Administration approval status, could find potential clinical application. 

https://www.pnas.org/content/early/2019/12/26/1904022116

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