Abstract
BackgroundLeukemia is a cancer of blood and bone marrow cells, causing about 300,000 deaths worldwide. Photodynamic therapy (PDT) is a promising alternative for the treatment of malignant tumors. KillerRed is a genetically encoded red fluorescent protein photosensitizer (PS). In this study, we aimed to investigate the effects of KillerRed-mediated PDT on chronic myelogenous leukemia K562 cells, acute monocytic leukemia NB4 cells, and acute monocytic leukemia THP1 cells.MethodsKillerRed was expressed in Escherichia coli cells, purified by Q-Sepharose column, and confirmed by western-blotting. The PDT effect on cell proliferation was evaluated by Cell Counting Kit-8 (CCK-8). Cell apoptosis was determined by PE Annexin V/7-AAD staining and flow cytometry. The distribution of KillerRed in leukemia cells was detected by confocal laser scanning microscopy (CLSM) and western-blotting. The ROS generation was measured by flow cytometry.ResultsPure KillerRed was obtained with a yield of about 37 mg per liter of bacterial cells. KillerRed photodynamic inactivated the leukemia cells in a concentration-dependent manner, but exhibited no obvious dark toxicity. PDT mediated by KillerRed could also induce apoptotic response (mainly early apoptosis) in the three cell lines. The CLSM imaging indicated that KillerRed was distributed within the cytoplasm and nuclei of leukemia cells, causing damages to the cytoplasm and leaving the nuclear envelope intact during light irradiation. KillerRed distributed both in the cytosol and nuclei was confirmed by western blotting, and ROS significantly increased in PDT treated cells compared to the cells treated with KillerRed alone.ConclusionsOur studies demonstrated that KillerRed-mediated PDT could effectively inactivate K562, NB4, and THP1 leukemia cells and trigger cell apoptosis, and it has potential to be used individually or complementally, in the treatment of leukemia.
Highlights
Leukemia is a cancer of blood and bone marrow cells, causing about 300,000 deaths worldwide
The results showed that exposure of cells to KillerRed-mediated Photodynamic therapy (PDT) resulted in significantly increased reactive oxygen species (ROS) production, as compared to the cells treated with KillerRed alone (Fig. 4)
The results showed that ROS level significantly increased in PDT treated cells compared to the cells treated with KillerRed alone
Summary
Leukemia is a cancer of blood and bone marrow cells, causing about 300,000 deaths worldwide. Leukemia, defined as cancer of the blood and bone marrow cells, usually results in high numbers of abnormally immature white blood cells which distribute at the early steps of the hematopoietic hierarchy [1], and cause a lot of symptoms such as bleeding, fever, feeling tired, and an increased risk of infections. Acute leukemia is usually characterized by overgrowth and rapid accumulation of immature malignant blood cells. The current treatment for leukemia mainly involves allogenous stem cell transplantation, radiation therapy, and chemotherapy, these therapies could lead to serious late effects such as higher risk of infections, graft-versus-host disease (GVHD), cytotoxicity to normal cells, and especially drug-resistance [5]. Much more attention has been focused on searching for alternative approaches
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