Mechanisms of resistance to the cytotoxic effects of oxysterols in human leukemic cells

• Published in: The Journal of steroid biochemistry and molecular biology Vol. 88; no. 3; pp. 311 - 320
• Main Authors: Gregorio-King, Claudia C, Gough, Tamara, Van Der Meer, Gavin J, Hosking, Jane B, Waugh, Caryll M, McLeod, Janet L, Collier, Fiona Mc, Kirkland, Mark A
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.2004; Elsevier Science
• Subjects: ACAT; Amino Acid Sequence; Apoptosis; Base Sequence; bcl-2; Biological and medical sciences; c-myc; CNBP; DNA Primers; Fundamental and applied biological sciences. Psychology; HL-60 Cells; HL60; HMG-CoA; Human leukemic cells; Humans; Leukemia - metabolism; Molecular Sequence Data; Nifedipine - pharmacology; ORP3; OSBPL3; Oxysterols; Rhotekin; Sequence Homology, Amino Acid; Sterols - pharmacology; Vertebrates: endocrinology; Rhotekin; bcl-2; ORP3; c-myc; Human leukemic cells; CNBP; OSBPL3; Oxysterols; HMG-CoA; ACAT; HL60; Apoptosis; Human; HMG; Bcl-2 protein; Gonadotropin; Resistance; C-Onc gene; Coenzyme A; Protooncogene
• ISSN: 0960-0760; 1879-1220
• DOI: 10.1016/j.jsbmb.2003.12.007

We have developed hematopoietic cells resistant to the cytotoxic effects of oxysterols. Oxysterol-resistant HL60 cells were generated by continuous exposure to three different oxysterols—25-hydroxycholesterol (25-OHC), 7-beta-hydroxycholesterol (7β-OHC) and 7-keto-cholesterol (7κ-C). We investigated the effects of 25-OHC, 7β-OHC, 7κ-C and the apoptotic agent staurosporine on these cells. The effect of the calcium channel blocker nifedipine on oxysterol cytotoxicity was also investigated. Differential display and real-time PCR were used to quantitate gene expression of oxysterol-sensitive and -resistant cells. Our results demonstrate that resistance to the cytotoxic effects of oxysterols is relatively specific to the type of oxysterol, and that the cytotoxicity of 25-OHC but not that of 7β-OHC and 7κ-C, appears to occur by a calcium dependent mechanism. Oxysterol-resistant cells demonstrated no significant difference in the expression of several genes previously implicated in oxysterol resistance, but expressed the bcl-2 gene at significantly lower levels than those observed in control cells. We identified three novel genes differentially expressed in resistant cells when compared to HL60 control cells. Taken together, the results of this study reveal potentially novel mechanisms of oxysterol cytotoxicity and resistance, and indicate that cytotoxicity of 25-OHC, 7β-OHC and 7κ-C occur by independent, yet overlapping mechanisms.