Apoptotic Effects of a Thioether Analog of Vitamin K3 in a Human Leukemia Cell Line

Research suggests that thioether analogs of vitamin K3 (VK3) can act to preserve the phosphorylation of epidermal growth factor receptors by blocking enzymes (phosphatases) responsible for their dephosphorylation. Additionally, these derivatives can induce apoptosis via mitogen-activated protein kinase and caspase-3 activation, inducing reactive oxygen species (ROS) production, and apoptosis. However, vitamin K1 exhibits only weak inhibition of phosphatase activity, while the ability of VK3 to cause oxidative DNA damage has raised concerns about carcinogenicity. Hence, in the current study, we designed, synthesized, and screened a number of VK3 analogs for their ability to enhance phosphorylation activity, without inducing off-target effects, such as DNA damage. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay revealed that each analog produced a different level of cytotoxicity in the Jurkat human leukemia cell line; however, none elicited a cytotoxic effect that differed significantly from that of the control. Of the VK3 analogs, CPD5 exhibited the lowest EC50, and flow cytometry results showed that apoptosis was induced at final concentrations of ≥10 μM; hence, only 0.1, 1, and 10 μM were evaluated in subsequent assays. Furthermore, CPD5 did not cause vitamin K-attributed ROS generation and was found to be associated with a significant increase in caspase 3 expression, indicating that, of the synthesized thioether VK3 analogs, CPD5 was a more potent inducer of apoptosis than VK3. Hence, further elucidation of the apoptosis-inducing effect of CPD5 may reveal its efficacy in other neoplastic cells and its potential as a medication.

The IN VITRO STUDY OF APOPTOSIS INDUCTION BY L-ASPARAGINASE OF ASPERGILLUS FUMIGATUS (ASPF-6) ON HUMAN LEUKEMIA CELL LINES

Objective: L-Asparaginase is a relatively widespread enzyme used in the lymphoblastic leukemia chemotherapy. In the present investigation, we report new potential fungal L-asparaginase producer Aspergillus fumigatus from Kadalundi mangrove forest, Kerala. The aim of the present investigation was to evaluate the concentration-dependent cytotoxicity and apoptosis-inducing the effect of extracted enzyme and its ability to induce apoptosis against human leukemia cell lines-HL-60. Methods: The fungal strain was isolated by serial dilution method from rhizosphere soil of mangrove forest. The isolated enzyme purified by 80% ammonium sulfate precipitation, dialysis, and ion exchange chromatography. To determine cytotoxicity and level of apoptosis, three different tests were performed: (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, JC-1 flow cytometry, and Annexin V/propidium iodide (PI) flow cytometric DNA fragmentation. The test compound efficiency compared with positive drug doxorubicin against HL-60 cell lines. Results: The test compound exhibited a concentration-dependent cytotoxic effect on proliferation of HL-60 cell lines (IC-50 12.39 U) with a different level of apoptosis induction (LR-11.3%). Conclusion: A. fumigatus derived L-asparaginase may be clinically useful and results in better utilization for limited fungal-derived drug resources and improve financial feasibility as a therapeutic option for human leukemia.