Synergistic induction of HL60 cell differentiation by ketoconazole and 1-desoxy analogues of vitamin D3.
BACKGROUND
The goal of differentiation therapy is to induce cancer cells to stop proliferating and to express characteristics of normal cells. Vitamin D analogues, such as the deltanoids, are being evaluated as differentiation agents in the treatment of several human cancers (e.g., myeloid leukemias); however, these compounds have a tendency to produce hypercalcemia in patients receiving therapy. A combination of a differentiation-inducing deltanoid with a compound that blocks entry of calcium into cells (e.g., ketoconazole) may offer a new approach to differentiation therapy and address the problem of hypercalcemia. We investigated whether various ketoconazole-deltanoid combinations would alter cellular differentiation or intracellular calcium homeostasis in comparison with deltanoids used alone.


METHODS
Cultured human leukemia HL60 cells were treated with ketoconazole-deltanoid combinations. Markers of differentiation (expression of CD11b and CD14 antigens and of non-specific esterase) were measured by flow cytometry and cytochemistry; cell cycle distribution was measured by flow cytometry of propidium iodide-stained cells. Expression of differentiation-related genes was assessed by northern blotting and immunoblotting, and changes in intracellular calcium homeostasis were monitored by fluorescence analysis of fura-2-containing cells.


RESULTS
Ketoconazole strongly potentiated the differentiating activity of the deltanoids, which exhibited low potency when used alone. Ketoconazole-deltanoid combinations had little effect on HL60 cell-cycle distribution, although the cells did stop proliferating and they differentiated. Ketoconazole-deltanoid combinations produced only minor changes in intracellular calcium homeostasis compared with changes produced by 1,25-dihydroxyvitamin D3, either alone or in combination with ketoconazole.


CONCLUSIONS
These results suggest that ketoconazole may be useful in combination with vitamin D analogues in the differentiation therapy for myeloid leukemias.
Wang
X
X
Department of Pathology & Laboratory Medicine, UMDNJ-New Jersey Medical School, Newark 07103, USA.
Gardner
J P
JP
Kheir
A
A
Uskokovic
M R
MR
Studzinski
G P
GP
D000970:Antineoplastic Agents / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000032:analysis; D018845:CD11 Antigens / Q000032:analysis; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004357:Drug Synergism; D018922:HL-60 Cells / Q000187:drug effects* / Q000276:immunology; D006801:Humans; D007654:Ketoconazole / Q000494:pharmacology*; D007951:Leukemia, Myeloid / Q000188:drug therapy; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D009000:Monocytes / Q000187:drug effects; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000494:pharmacology
D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D018845:CD11 Antigens; D015220:Calcium Channels; D018950:Lipopolysaccharide Receptors; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D007654:Ketoconazole; D002118:Calcium