Signaling pathways subverted in T-cell oncogenesis. TCR costimulatory receptors CD28 and inducible T-cell costimulator (ICOS) and interleukin receptor are depicted with a simplified representation of the downstream signaling mediators. The receptors and signaling pathway components that are recurrently mutated in T-cell lymphoma are depicted with bold outlines. DAG, diacylglycerol; GTP, guanine nucleotide triphosphate; IL-6, interleukin-6; ITAM, immunoreceptor tyrosine-based activation motif; IP₃, inositol 3-phosphate; JAK, Janus kinase; MHC, major histocompatibility complex; mTOR, mammalian target of rapamycin; P, phosphorylation; PTPN, protein tyrosine phosphatase nonreceptor; STAT, signal transducer and activator of transcription.