Costimulatory domain Sample Clauses

Costimulatory domain. Second-generation CARs can differ in their choice of costimulatory domain, which affects the efficacy, phenotype and metabolic properties of the resulting CAR T-cells122. In CARs the most frequently used costimulatory domains derive from the CD28 family (CD28 and ICOS) or the TNFR family (4-1BB, CD27, OX40). In their endogenous contexts CD28 family and TNFR family molecules function with notable differences, these distinctions are translated in CAR T-cells comprising of the different costimulatory domains. Second-generation CARs used in the clinic that utilize either a CD28 or 4-1BB costimulatory module and both have shown impressive outcomes123–125. Preclinical evaluations of CD28 costimulation suggest it is fundamental for early activation of naïve T-cells and promotes the rapid development of T- cell effector functions. After initiation of signal 1, T-cells require co-stimulation (signal 2) to achieve optimal activation and prevent anergy126. Endogenous T-cell co-stimulation is usually provided by CD28 once it encounters its ligands B7.1 and B7.2. This ligation results in phosphorylation of membrane proximal YMNM motif by Src family tyrosine kinases, enabling PI3K to bind and activate AKT, which leads to initiation of signalling cascades including the mTOR127,128, GRB2-SOS129 and glycogen synthase kinase 3 pathways130. CD28 contains the proline rich motifs PRRP and PYAP which bind Lck and ITK and other SH3- containing proteins such as GRB2 and filamin A129,131. Furthermore, the YMNM and PYAP motifs are essential for immunological synapse formation132. In comparison, 4-1BB is up-regulated on T-cells 24 hours after activation to stimulate proliferation, effector function and to inhibit apoptosis133,134. 4-1BB contains binding sites for TRAF1-3, and these adaptor molecules can modulate the activation of the canonical and noncanonical nuclear factor κβ (NF-κβ) pathway as well as mitogen-activated protein kinases (MAPKs)135,136. Signalling downstream of these TRAF family members up-regulates the transcription of pro-survival proteins such as BCL-2 and BCL-XL as well as proinflammatory cytokines such as IL-2 and IFN-γ137. However, in TNFR-containing CAR T- cells pathway activation occurs immediately upon CAR ligation, which potentially leads to differing biochemical function compared to non-transduced T-cells. Studies have demonstrated that activation of 4-1BB containing CARs leads to higher levels of BCL-2 and BCL-XL when compared to CD28 CARs, in keeping wi...