Enhancement of 1α25-dihydroxyvitamin D3-induced differentiation of human leukaemia HL-60 cells into monocytes by parthenolide via inhibition of NF-κB activity

摘要

class="enumerated" style="list-style-type:decimal">Transcription factors such as NF-κB provide powerful targets for drugs to use in the treatment of cancer. In this report parthenolide (PT), a sesquiterpene lactone of herbal remedies such as feverfew (Tanacetum parthenium) with NF-κB inhibitory activity, markedly increased the degree of human leukaemia HL-60 cell differentiation when simultaneously combined with 5 nM 1α,25-dihydroxyvitamin D3 (1,25-(OH)2D3). PT by itself did not induce HL-60 cell differentiation.Cytofluorometric analysis indicated that PT stimulated 1,25-(OH)2D3-induced differentiation of HL-60 cells predominantly into monocytes.Pretreatment of HL-60 cells with PT before the 1,25-(OH)2D3 addition also potentiated the 1,25-(OH)2D3-induced HL-60 cell differentiation in both a dose- and a time-dependent manner, in which the enhanced levels of cell differentiation closely correlated with the inhibitory levels of NF-κB binding activity by PT.In contrast, santonin, a sesquiterpene lactone without an inhibitory activity of NF-κB binding to the κB sites, did not enhance the 1,25-(OH)2D3-induced HL-60 cell differentiation.In transfection experiments, PT enhanced 1,25-(OH)2D3-induced VDRE-dependent promoter activity. Furthermore, PT restored 1,25-(OH)2D3-induced VDRE-dependent promoter activity inhibited by TNF-α, an activator of NF-κB signalling pathway.These results indicate that PT strongly potentiates the 1,25-(OH)2D₃-induced HL-60 cell differentiation into monocytes via the inhibition of NF-κB activity and provide evidence that inhibition of NF-κB activation can be a pre-requisite to the efficient entry of promyelocytic leukaemia cells into a differentiation pathway.