Induction of apoptosis in p53-null HL-60 cells by inhibition of lanosterol14-alpha demethylase

To determine the role of cholesterol deprivation in cell proliferation and, eventually, in apoptosis, HL-60 promyelocytic cells were incubated in a ch olesterol-depleted medium in the presence of SKF 104976, a specific inhibit or of lanosterol 14-alpha demethylase. As expected, SKF 104976 efficiently blocked the [C-14]-acetate incorporation into cholesterol, whereas it induc ed the accumulation of both lanosterol and, especially, dihydrolanosterol. As a consequence, cell proliferation was greatly depressed at 24 h of treat ment with the drug, and clear signs of apoptosis - annexin V binding, conde nsed and fragmented nuclei and DNA ladder - were observed thereafter. Provi ded that the HL-60 cell line does not express p53, it may be concluded that apoptosis induced by cholesterol deprivation is not dependent on this tumo r suppressor protein. Supplementing the incubation medium with LDL-choleste rol or pure free cholesterol, fully prevented cell growth inhibition and ap optosis induction, whereas mevalonate was ineffective. These results indica te that cholesterol plays a specific role in cell proliferation, a function that is not shared by its precursors lanosterol and dihydrolanosterol. (C) Societe francaise de biochimie et biologie moleculaire / Elsevier, Paris.