Many cancer patients derive little benefit from checkpoint inhibitors, drugs that target immune system checkpoints, mechanisms that temper immune responses. To date, most checkpoint inhibitors target checkpoints on T cells to unleash T cells’ full anticancer potential. But new checkpoint inhibitors could target cells of a different kind, myeloid cells, potentially enhancing cancer immunotherapy. Specifically, checkpoint inhibitors could target c-Rel, a protein expressed by myeloid cells, to block the generation of myeloid-derived suppressor cells (MDSCs).