CSF2 and neoplasm: In some CRPC patients, combining CTLA-4 blockade with systemic granulocyte-macrophage colony-stimulating factor (GM-CSF) induced a decline in PSA with an expansion of activated circulating CD8+ T cells, presumably mediated by preexisting tumor-specific T cells that were primed by endogenous tumor-derived antigens and were receptive to the CTLA-4 blockade [61].