Activation of Myosin Phosphatase by Epigallocatechin-Gallate Sensitizes THP-1 Leukemic Cells to Daunorubicin.

Anti-cancer Agents in Medicinal Chemistry
Emese TóthAndrea Kiss

Abstract

The Myosin Phosphatase (MP) holoenzyme is composed of a Protein Phosphatase type 1 (PP1) catalytic subunit and a regulatory subunit termed Myosin Phosphatase Target subunit 1 (MYPT1). Besides dephosphorylation of myosin, MP has been implicated in the control of cell proliferation via dephosphorylation and activation of the tumor suppressor gene products, retinoblastoma protein (pRb) and merlin. Inhibition of MP was shown to attenuate the drug-induced cell death of leukemic cells by chemotherapeutic agents, while activation of MP might have a sensitizing effect. Recently, Epigallocatechin-Gallate (EGCG), a major component of green tea, was shown to activate MP by inducing the dephosphorylation of MYPT1 at phospho-Thr696 (MYPT1pT696), which might confer enhanced chemosensitivity to cancer cells. THP-1 leukemic cells were treated with EGCG and Daunorubicin (DNR) and cell viability was analyzed. Phosphorylation of tumor suppressor proteins was detected by Western blotting. EGCG or DNR (at sub-lethal doses) alone had moderate effects on cell viability, while the combined treatment caused a significant decrease in the number of viable cells by enhancing apoptosis and decreasing proliferation. EGCG plus DNR decreased the phosphorylati...Continue Reading

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Apr 4, 2021·International Journal of Molecular Sciences·Emese TóthAndrea Kiss

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