CTLA4 and prostate cancer: Following numerous disappointing efforts and unequivocal clinical failures, the field of cancer immunotherapy has recently received a significant boost, encouraged primarily by the approval of the autologous cellular immunotherapy, sipuleucel-T, for the treatment of prostate cancer in 2010 [3] and the approval of the anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) antibody, ipilimumab, and of anti-programmed cell death protein 1 (PD1) antibodies for the treatment of melanoma in 2011 and 2014, [4] respectively.