β-lapachone is a 1,2-naphthoquinone of great therapeutic interest that induces cell death by autophagy and apoptosis in tumor cells due to oxidative stress increasing. However, its high toxicity in healthy tissues limits its clinical use, which stimulates the planning and synthesis of more selective analogs. The aim of this study was to investigate the cytotoxic activity of three thiosemicarbazones derived from β-lapachone (BV2, BV3 and BV5) in leukemia cells. Cytotoxicity tests were performed on tumor cells (HL-60, K562, K562-Lucena and MOLT-4) and normal peripheral blood mononuclear cells (PBMCs). Subsequently, the mode of action of compounds was accessed by optical microscopy, transmission electron microscopy or fluorescence microscopy. Flow cytometry analysis was performed to investigate apoptosis induction, cell cycle, DNA fragmentation and mitochondrial depolarization. All derivatives inhibited tumor cell growth after 72 h (IC50 < 10 μM to all cell lines, including the resistant K562-Lucena) with less toxic effects in PBMC cells, being BV3 the most selective compound with selective index (SI) of 275 for HL-60; SI of 40 to K562; SI of 10 for MOLT-4 and SI of 50 to K562-Lucena compared to β-lapachone with SI of 18 to HL-60, SI of 3.7 to K562; SI of 2.4 to MOLT-4 and SI of 0.9 to K562-Lucena. In addition, the K562 or MOLT-4 cells treated with BV3 showed characteristics of both apoptosis and autophagy cell death, mainly by autophagy. These results demonstrate the potent cytotoxic effect of thiosemicarbazones derived from β-lapachone as promising anticancer drugs candidates, encouraging the continuity of in vivo tests.
Keywords: Apoptosis; Cell cycle; Leukemia; Quinones; Thiosemicarbazone.
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