Proliferation-Attenuating and Apoptosis-Inducing Effects of Tryptanthrin on Human Chronic Myeloid Leukemia K562 Cell Line in Vitro

Shan Miao,Yong Zhao,Wei Hua,Hai Zhang,Siwang Wang,Qing Miao,Xiaopeng Shi,Jiyuan Sun,Caiqin Zhang

doi:10.3390/ijms12063831

Abstract

Tryptanthrin, a kind of indole quinazoline alkaloid, has been shown to exhibit anti-microbial, anti-inflammation and anti-tumor effects both in vivo and in vitro. However, its biological activity on human chronic myeloid leukemia cell line K562 is not fully understood. In the present study, we investigated the proliferation-attenuating and apoptosis-inducing effects of tryptanthrin on leukemia K562 cells in vitro and explored the underlying mechanisms. The results showed that tryptanthrin could significantly inhibit K562 cells proliferation in a time- and dose-dependent manner as evidenced by MTT assay and flow cytometry analysis. We also observed pyknosis, chromatin margination and the formation of apoptotic bodies in the presence of tryptanthrin under the electron microscope. Nuclei fragmentation and condensation by Hoechst 33258 staining were detected as well. The amount of apoptotic cells significantly increased whereas the mitochondrial membrane potential decreased dramatically after tryptanthrin exposure. K562 cells in the tryptanthrin treated group exhibited an increase in cytosol cyt-c, Bax and activated caspase-3 expression while a decrease in Bcl-2, mito cyt-c and pro-caspase-3 contents. However, the changes of pro-caspase-3 and activated caspase-3 could be abolished by a pan-caspase inhibitor ZVAD-FMK. These results suggest that tryptanthrin has proliferation-attenuating and apoptosis-inducing effects on K562 cells. The underlying mechanism is probably attributed to the reduction in mitochondria membrane potential, the release of mito cyt-c and pro-caspase-3 activation.

Highlights

Chronic myeloid leukemia (CML) is initiated by the aberrant pluripotent hematopoietic stem cell (HSC) growth and apoptosis characterized by accumulation of immature granulocytes in the peripheral blood and bone marrow
We show that tryptanthrin inhibits mitochondria membrane potential in the human CML cell line K562, accompanied by cell cycle arrest, caspases activation, apoptosis induction and proliferation inhibition
K562 cells are derived from human CML and express the bcr/abl kinase. bcr/abl kinase enables the CML cells to growth in a uncontrolled way by inducing p38 MAPK, Ras, Jun, pyrimidine of iodinate (PI)-3K/Akt and STAT5 pathways, and blockage of bcr/abl kinase by imatinib mesylate has been recognized as the target therapy for CML [2,16,17,18]

Summary

Introduction

Chronic myeloid leukemia (CML) is initiated by the aberrant pluripotent hematopoietic stem cell (HSC) growth and apoptosis characterized by accumulation of immature granulocytes in the peripheral blood and bone marrow. Inhibiting HSC proliferation might promote leukemia cell apoptosis and cell cycle arrest, which is clinically beneficial in the therapeutic strategy of CML [1]. An orally administrated tyrosine kinase inhibitor is recommended as the first-line drug for bcr-abl fusion gene positive CML patients. Imatinib mesylate competitively inhibits ATP binding to bcr-abl tyrosine kinase and promotes CML cells apoptosis. Known as programmed cell death (PCD), is essential for normal development and cell homeostasis and it participates in many pathological processes [4]. It is morphologically characterized by chromatin margination and the formation of apoptotic bodies [5]. Decreased mitochondria membrane potential inhibits ATP generation, results in oxidative stress and promotes mitochondria dysfunction

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