The synthetic flavanone 6-methoxy-2-(naphthalen-1-yl)chroman-4-one induces apoptosis and activation of the MAPK pathway in human U-937 leukaemia cells

Abstract

Synthetic flavonoids containing a naphthalene ring have attracted attention as potential cytotoxic compounds. Here, we synthesized ten chalcones and their corresponding flavanones and evaluated their antiproliferative activity against the human tumour cell line U-937. This series of chalcone derivatives was characterized by the presence of a naphthalene ring which was kept unaltered- and attached to the β carbon of the 1-phenyl-2-propen-1-one framework. The structure-activity relationship of these chalcone derivatives and their corresponding cyclic compounds was investigated by the introduction of different substituents (methyl, methoxy, benzyloxy, chlorine) or by varying the position of the methoxy or benzyloxy groups on the A ring. The results revealed that both the chalcone containing the methoxy group at 5′ position of the A ring as well as its corresponding flavanone [6-methoxy-2-(naphthalen-1-yl)chroman-4-one] were the most cytotoxic compounds, with IC50 values of 2.8 ± 0.2 and 1.3 ± 0.2 μM, respectively, against U-937 cells. This synthetic flavanone was as cytotoxic as the antitumor etoposide in U-937 cells and displayed strong cytotoxicity against additional human leukaemia cell lines, including HL-60, MOLT-3 and NALM-6. Human peripheral blood mononuclear cells were more resistant than leukaemia cells to the cytotoxic effects of the flavanone. Treatment of U-937 cells with this compound induced G2-M cell cycle arrest, an increase in sub-G1 ratio and annexin-V positive cells, mitochondrial cytochrome c release, caspase activation and poly(ADP-ribose)polymerase processing. Apoptosis induction triggered by this flavonoid was blocked by overexpression of the anti-apoptotic protein Bcl-2. This flavanone induces phosphorylation of p38 mitogen-activated protein kinases, extracellular-signal regulated kinases and c-jun N-terminal kinases/stress-activated protein kinases (JNK/SAPK) following different kinetics. Moreover, cell death was attenuated by the inhibition of mitogen-activated extracellular kinases and JNK/SAPK and was independent of reactive oxygen species generation.