Impact of Chemotherapies on immunosuppression and discovery of new therapeutic targets

MDSC (myeloid derived suppressor cells) are immature cells from myeloid origin that accumulate in spleen and tumor bed during tumor growth and that can suppress anti-tumor immunity by various ways. Two chemotherapeutic agents, 5-fluorouracil and gemcitabin, that are commonly used in the treatment of colon cancer and pancreatic cancer, can selectively kill MDSC. Beneficial effects of 5-Fluorouracil and gemcitabin are however temporary. After treatment with those chemotherapies, an activation of the NLRP3 inflammasome is observed in MDSC, due to an interaction between cathepsin B and NLRP3, which leads to the production of IL-1 beta thus increasing pro-tumor immune responses. IL-1 beta enhances the production of IL-17 by CD4 T cells which in turn favors angiogenesis and tumor growth.