Introduction: Adult T-cell leukemia (ATL) is an aggressive form of malignancy caused by human T-
cell lymphotropic virus 1 (HTLV-1). Currently, there is no effective treatment for ATL. Thymoquinone has
been reported to have anti-cancer properties.
Objective: The aim of this study is to investigatthe effects of TQ on proliferation, apoptosis induction and the
underlying mechanism of action in both HTLV-1 positive (C91-PL and HuT-102) and HTLV-1 negative (CEM
and Jurkat) malignant T-lymphocytes.
Materials and methods: Cells were incubated with different thymoquinone concentrations for 24h. Cell cytotoxicity
was assayed using the CytoTox 96® Non-Radioactive Cytotoxicity Assay Kit. Cell proliferation was determined
using CellTiter 96® Non-Radioactive Cell Proliferation. Cell cycle analysis was performed by staining
with propidium iodide. Apoptosis was assessed using cell death ELISA kit. The effect of TQ on p53, p21, Bcl-2
protein expression was determined using Western blot analysis while TGF mRNA expression was determined
Results: At non-cytotoxic concentrations of TQ, it resulted in the inhibition of proliferation in a dose dependent
manner. Flow cytometric analysis revealed a shift in the cell cycle distribution to the PreG1 phase which is a
marker of apoptosis. Also TQ increase DNA fragmentation. TQ mediated its anti-proliferative effect and apoptosis
induction by an up-regulation of TGFβ1, p53 and p21 and a down-regulation of TGF-α and Bcl-2α.
Conclusion: Thymoquinone presents antiproliferative and proapoptotic effects in ATL cells. For this reason,
further research is required to investigate its possible application in the treatment of ATL.