CTLA4 and prostate cancer: The importance of antibodies is not only true for melanoma as a group has recently shown in prostate cancer that clinical responders to CTLA4-blockade and granulocyte macrophage colony-stimulating factor (GM-CSF) developed enhanced antibody responses to a higher number of antigens than non-responders and that pre-existing antibodies to these antigens were more likely to be present in the clinical responders compared to non-responders [54].