Trichosanthin increases Granzyme B penetration into tumor cells by upregulation of CI-MPR on the cell surface.

Trichosanthin is a plant toxin belonging to the family of ribosome-inactivating proteins. It has various biological and pharmacological activities, including anti-tumor and immunoregulatory effects. In this study, we explored the potential medicinal applications of trichosanthin in cancer immunotherapy. We found that trichosanthin and cation-independent mannose-6-phosphate receptor competitively bind to the Golgi-localized, γ-ear containing and Arf-binding proteins. It in turn promotes the translocation of cation-independent mannose-6-phosphate receptor from the cytosol to the plasma membrane, which is a receptor of Granzyme B. The upregulation of this receptor on the tumor cell surface increased the cell permeability to Granzyme B, and the latter is one of the major factors of cytotoxic T lymphocyte-mediated tumor cell apoptosis. These results suggest a novel potential application of trichosanthin and shed light on its anti-tumor immunotherapy.