EGCG suppresses CD3-mediated T-cell-induced pathways in leukemia cells via Zap-70 inhibition

2344

The zeta chain associated protein of 70 kDa (Zap-70) tyrosine kinase plays a critical role in cell surface expression of T-cell antigen receptor/CD3 complex signaling. A high level of Zap-70 expression is found in T-cell proliferative diseases and a subgroup of chronic lymphocytic leukemia (CLL), which suggests that Zap-70 could be an excellent prognostic biomarker for CLL. (-)-Epigallocatechin gallate (EGCG) is suggested to have a role as a preventive agent in cancer, obesity, diabetes, and cardiovascular disease. Here we identified Zap-70 as an important and novel molecular target of EGCG in leukemia. Zap-70 and EGCG showed high binding affinity (Kd = 0.6207 μmol/L) and additional results revealed that EGCG effectively suppressed Zap-70, LAT, PLCγ1, MEK and ERK1/2 kinase activities in CD3-induced T-cell leukemia. EGCG decreased CD3-induced DNA-binding activity of AP-1 and NFAT and also suppressed IL-2 secretion. Finally, EGCG inhibited cell proliferation and induced apoptosis in Zap-70 expressing cells but had no effect on Zap-70 deficient cells. Information acquired from molecular docking studies was supported by site-directed mutagenesis experiments and these results indicated that EGCG could form a series of intermolecular hydrogen bonds and hydrophobic interactions within the ATP binding domain, which may contribute to the stability of the Zap70-EGCG complex. We suggest that EGCG might be a potential immunomodulator for the management of Zap-70-dependent T-cells in human leukemia.