EGCG Supresses CLL Pathways through ZAP-70

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EGCG suppresses CD3-mediated T-cell-induced pathways in leukemia

cells via Zap-70 inhibition

Jung-Hyun Shim, Hong Seok Choi, Angelo Pugliese, Bu Young Choi, Ann

M. Bode, Zigang Dong. Hormel Institute, University of Minnesota,

Austin, MN

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 ìmol/L) and additional results revealed that EGCG

effectively suppressed Zap-70, LAT, PLCã1, 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.