PDCD1 and neoplasm: To identify the potent PD-1-controlled tumor-suppressor programs that prevent T cell transformation upon oncogenic T cell signaling, we induced ITK–SYK expression in vivo in primary CD4+ T cells with and without Pdcd1 by injecting tamoxifen into ITK-SYKCD4-CreERT2 and ITK-SYKCD4-CreERT2;Pdcd1−/− mice.