Cancer Chemoprevention with PV-1, a Novel Prunella Vulgaris containing Herbal Mixture that Remodels the Tumor Immune Microenvironment in Mice

The herb Prunella vulgaris has shown significant immune-stimulatory and anti-inflammatory effects in mouse models. Here, the effects of a novel Prunella vulgaris-containing herbal mixture, PV-1, were examined in several mouse models for cancer, including chemically induced models of lung and oral cancers as well as syngraft models for lung cancer and melanoma. PV-1 exhibited no toxicity in a dose escalation study over 8 weeks in A/J mice. PV-1 significantly inhibited mouse lung tumor development induced by the lung carcinogens. PV-1 also hindered the induction of oral squamous cell carcinomas in C57BL/6 mice. Flow cytometry analysis showed that PV-1 increased the numbers of CD8+ tumor infiltrating lymphocytes (TILs) and increased the production of granzyme B, TNFalpha, and IFNgamma by CD8+ TILs. These results indicate that PV-1 remodels the tumor immune microenvironment by selectively inhibiting g-MDSCs and increasing CD8+ TILs within tumors, resulting in decreased immune suppression and enhanced cancer chemopreventive efficacy.