Published in Cancer Detection and Prevention 2000; 24(4):325-342.

Inhibition of Cytochrome P-450 Modulates AII-Trans-Retinoic Acid-Induced Differentiation and Apoptosis of HL-60 Cells

Jirina Hofmanová, PhD,a Karel Soucek,a Ladislav Dusek, PhD,b Jaromíra Netíkováa, and Alois Kozubík, PhDa

aInstitute of Biophysics, Academy of Sciences of the Czech Republic, and bDepartment of Environmental Chemistry and Ecotoxicology, Faculty of Sciences, Masaryk University, Brno, Czech Republic

Address all correspondence and reprint requests to: Jirina Hofmanová, PhD, Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, CZ-612 65 Bmo, Czech Republic.

ABSTRACT: We studied the effects of inhibition of cytochrome P-450 by proadifen (SKF525A) on the processes induced in myeloid leukemia HL-60 cells by all-trans-retinoic acid (ATRA). The parameters reflecting cell proliferation, differentiation, and apoptosis were detected by flow cytometry as the principal method at selected time intervals (24 - 96 hours). Changes in the expression of Bcl-2 protein were detected by Western blotting. The majority of experiments were designed as a factorial combination of the treatment and assessed for significance of the interactions. Proadifen was demonstrated synergistically (1) to potentiate the antiproliferative and differentiation effects of ATRA, and (2) to increase cell viability and prevent ATRA-induced apoptosis. Moreover, proadifen weakened ATRA-induced downregulation of the Bcl-2 protein. Our results may be of practical importance because cytochrome P-450 inhibitors are used clinically in treating cancer patients. Assuming that effects on the leukemic cells in vivo would be similar, this type of combined therapy could help to achieve better results even with lower doses of ATRA.

KEY WORDS: Bcl-2 protein, cell cycle, dimethyl sulfoxide, myeloid leukemia, proadifen, .