All-trans-retinoic acid metabolites significantly inhibit the proliferation of MCF-7 human breast cancer cells in vitro

Abstract

Summary All-trans-retinoic acid (ATRA) is well known to inhibit the proliferation of human breast cancer cells. Much less is known about the antiproliferative activity of the naturally occurring metabolites and isomers of ATRA. In the present study, we investigated the antiproliferative activity of ATRA, its physiological catabolites 4-oxo-ATRA and 5,6-epoxy-ATRA and isomers 9-cis-RA and 1 3-cis-RA in MCF-7 human breast cancer cells by bromodeoxyuridine incorporation. MCF-7 cells were grown in steroid-and retinoid-free medium supplemented with growth factors. Under these culture conditions, ATRA and its naturally occurring catabolites and isomers showed significant antiproliferative activity in MCF-7 cells in a concentration-dependent manner (10-11 M to 10-M). The antiproliferative activity of ATRA catabolites and isomers was equal to that of the parent compound ATRA at concentrations of 10-M and 1 07 M. Only at 10-6 M were the catabolites and the stereoisomer 1 3-cis-RA less potent. The stereoisomer 9-cis-RA was as potent as ATRA at all concentrations tested (1 0-11 M to 10-M). In addition, we show that the catabolites and isomers were formed from ATRA to only a limited extent. Together, our findings suggest that in spite of their high antiproliferative activity the catabolites and isomers of ATRA cannot be responsible for the observed growth inhibition induced by ATRA.

The antiproliferative activity of all-trans-retinoic acid catabolites and isomers is differentially modulated by liarozole-fumarate in MCF-7 human breast cancer cells

“…These effects could only be properly studied in a steroid-and retinoid-free culture medium supplemented with growth factors. We have previously demonstrated that not only ATRA itself, but also its naturally occurring catabolites, 4-oxo-ATRA and 5,6-epoxy-ATRA, as well as its stereoisomers, 9-cis-RA and 13-cis-RA, significantly inhibit the proliferation of MCF-7 human breast cancer cells (Van heusden et al, 1998). Liarozole-fumarate, at a concentration of 106 M, enhanced the antiproliferative activity of ATRA and its catabolites, but not that of the stereoisomers of ATRA.…”

“…Preparation of dextran-coated charcoal (DCC)-treated fetal bovine serum (FBS) DCC-treated FBS was prepared as described by Horwitz and McGuire (1978 (Van heusden et al, 1998).…”

“…Also, ATRA can isomerize in cell culture to 9-cis-RA and 13-cis-RA, an obviously non-enzymatic process (Urbach and Rando, 1994). ATRA and its naturally occurring catabolites and isomers possess significant antiproliferative activity in MCF-7 cells (Van heusden et al, 1998). To further explore its mechanism of action, we studied whether liarozole-fumarate was able to enhance the antiproliferative activity of these naturally occurring ATRA catabolites and isomers.…”

Retinoic acid receptor α and retinoid-X receptor-specific agonists synergistically target telomerase expression and induce tumor cell death

“…These results demonstrate that the occupancy of the ligand-binding sites of both RXR and (PML-)RARa in a heterodimer is required to mediate the optimal telomerase downregulation consistent with cell death. This enables us to propound a reasonable explanation for the threshold of ATRA activity, that is the steady cellular production of small amounts of the natural RXR ligand (9-cis-RA) as a byproduct of ATRA by isomerization (about 7-9%) (Urbach and Rando, 1994;Van heusden et al, 1998). Although the precise mechanisms remain to be elucidated, these results, indicating that receptor cross-talk does exist within a double-liganded heterodimeric receptor complex and is necessary for efficient hTERT Targeting hTERT expression by receptor-specific retinoids F Pendino et al regulation, are consistent with previous observations that both RAR and RXR partners of RAR-RXR heterodimers can synergistically activate transcription of RA-responsive genes (Roy et al, 1995;Germain et al, 2002).…”

Expression of estrogen receptor α, retinoic acid receptor α and cellular retinoic acid binding protein II genes is coordinately regulated in human breast cancer cells

“…ATRA has been successfully used to induce clinical remission in acute promyelocytic leukemia patients (Huang et al, 1988;Warrell et al, 1991;Degos et al, 1995;Tallman et al, 2002) and retinoids are of therapeutic interest in breast cancer because of their efficacy in preventing carcinogen-induced rat mammary cancers (Anzano et al, 1994;Gottardis et al, 1996), and their antiproliferative effect toward breast cancer cells in vitro (Seewaldt et al, 1995;Zhao et al, 1995;Fitzgerald et al, 1997;Van heusden et al, 1998;Niles, 2000;Yang et al, 2002). The effects of ATRA are mainly mediated by two classes of proteins, cellular retinoic acid binding proteins (CRABPs) and nuclear receptors (Chambon, 1996).…”