This cell-based assay is designed to monitor the phosphorylation of SHP2 on Tyr542, which represents a hallmark of its activation.
Many cancer cells overexpress checkpoint inhibitor ligands such as PD-L1. PD-L1 binds its counterpart checkpoint inhibitor receptor PD1, present at the surface of T lymphocytes. In turn, the PD1-PDL1 complex recruits and activates inhibitory effectors, such as SHP1 or SHP2. These two phosphatases, which are phosphorylated on Tyr564 and Tyr542 respectively by the kinase Lck, trigger the dephosphorylation of signaling proteins such as ZAP-70 or SLP-76, involved in the T cell activation pathway. Finally, activated SHP1 and SHP2 participate in T cell inactivation.
Preventing activation of SHP1 and/or SHP2 by small molecule inhibitors is believed to contribute to restoring the immune response against tumors.