Retinoids in cancer prevention and therapy

Cytochrome P450-dependent oxidation is a pathway for all-trans-retinoic acid (all-trans-RA) catabolism. Induction of this catabolic pathway was studied in MCF-7 breast cancer cells. MCF-7 cells showed low constitutive all-trans-RA catabolism. Concentration-dependent induction was obtained by preincubation of the cells with all-trans-RA (10(-9) to 10(-6) M). Onset of induction was fast, being detectable within 60 min, with maximal induction (45-fold) obtained after 16 h. Enzymatic characterization of induced all-trans-RA catabolism showed an estimated Km value (Michaelis-Menten constant) of 0.33 microM and a Vmax value (maximal velocity of an enzyme-catalysed reaction) of 54.5 fmol polar all-trans-RA metabolites 10(6) cells(-1) h(-1). These kinetic parameters represent the overall formation of polar metabolites from all-trans-RA. Induction of all-trans-RA catabolism was also obtained with other retinoids, CH55 >> 13-cis-RA = all-trans-RA > 9-cis-RA > 4-keto-all-trans-RA > 4-keto-13-cis-RA > retinol. The potency of the retinoids to induce all-trans-RA catabolism was correlated to their retinoic acid receptor affinity (Crettaz et al, 1990; Repa et al, 1990; Sani et al, 1990). Induction of all-trans-RA catabolism was inhibited by actinomycin D. Furthermore, all-trans-RA did not increase cytosolic retinoic acid-binding protein (CRABP) mRNA levels. These data suggest that induction of all-trans-RA catabolism in MCF-7 cells is a retinoic acid receptor-mediated gene transcriptional event. Induced all-trans-RA catabolism was inhibited by various retinoids with decreasing potency in the order: all-trans-RA > 4-keto-all-trans-RA > 13-cis-RA > 9-cis-RA > 4-keto-13-cis-RA > retinol > CH55. The antitumoral compound liarozole-fumarate inhibited all-trans-RA catabolism with a potency similar to that of all-trans-RA. Images Figure 4

Section: Discussionmentioning

confidence: 41%

Induction of the oxidative catabolism of retinoic acid in MCF-7 cells

Krekels

Verhoeven²,

Dun³

et al. 1997

“…Recently, it has been demonstrated that ATRA may have a strong therapeutic activity in acute promyelocytic leukaemia; its mechanism primarily relates to the property of determining the maturation of the non-differentiated leukaemic promyelocytes into non-proliferating, differentiated granulocytes (Huang et al, 1988;Bollag and Holdener, 1992).…”

Section: Discussionmentioning

confidence: 99%

All-trans retinoic acid (ATRA)-induced apoptosis is preceded by G1 arrest in human MCF-7 breast cancer cells

Mangiarotti¹,

Danova²,

R³

et al. 1998

In this study the effects of all-trans retinoic acid (ATRA) on cell cycle and apoptosis of MCF-7 human breast cancer cells were investigated to elucidate the mechanisms underlying the antineoplastic potential of this retinoid in breast cancer. The antiproliferative effect of ATRA was evaluated by DNA content measurements and dual-parameter flow cytometry of bromodeoxyuridine (BrdU) incorporation and of the expression of cell cycle-related proteins (Ki-67 as proliferation marker and statin as quiescence marker) vs DNA content. Apoptosis was also studied by flow cytometry of either DNA content or Annexin V labelling. After 10(-6) M ATRA treatment, the fraction of S-phase cells decreased significantly, and cells accumulated in the G0/G1 range of DNA contents. Dual-parameter flow cytograms showed a decrease in the percentage of Ki-67-labelled cells (after 10 days, only 20% of the cells were still positive for Ki-67 compared with 95% in controls), while the fraction of statin-positive cells increased slightly. From 3 days of treatment onwards, apoptosis was found to occur. These results show that ATRA-induced inhibition of MCF-7 cell growth is related to two mechanisms, i.e. the block of cell proliferation, mostly in a pre-S phase, and the induction of apoptosis. These results should be taken into account when attempting to design treatment programmes that associate ATRA with antineoplastic compounds of different cell cycle specificity.

“…The finding that the locus for PKCoa is not within the amplicon, is again consistent with the observations in breast cancer (Keith et al, 1992) and demonstrates that the increased copy number of ERBB2, RARa and topoisomerase IIa in CALU3 is not due to aneuploidy. The RARx receptor regulates normal cellular proliferation and differentiation through activation by retinoids, (Bollag & Holdener, 1992) and can, when expressed as a fusion protein in acute promyelocytic leukaemia act as an oncogene. (Clarkson, 1991).…”

Section: Discussionmentioning

confidence: 99%

“…(Clarkson, 1991). Gebert et al (1991) have shown the RARa gene to be expressed at high levels in CALU3 and so CALU3 may be a suitable model to study retinoids in cancer therapy, (Bollag & Holdener, 1992).…”

Section: Discussionmentioning

confidence: 99%

Expression of topoisomerase II alpha and beta in an adenocarcinoma cell line carrying amplified topoisomerase II alpha and retinoic acid receptor alpha genes

Coutts¹,

Plumb²,

Brown³

et al. 1993

Summary Human topoisomerase II enzymes are targets for a number of widely used anticancer agents. We have analysed a lung adenocarcinoma cell line CALU3, which has co-amplified topoisomerase IIax and ERBB2 sequences, for the structure of the amplicon and for expression of both topoisomerase Ila and P. The al., 1989;Woessner et al., 1991). Recent studies have also indicated that the alpha and beta enzymes are sublocalised within the nucleus to the nucleoplasm and nucleoli respectively (Negri et al., 1992).Interest in topoisomerase II is due both to its essential catalytic activity in normal cells and that it is a key target for a group of anticancer agents including etoposide, doxorubicin and mAMSA (Takano et al., 1992;Liu, 1989 (Muggia & Gill, 1991) the levels of expression in tumours may be important in determining the success of the treatment. Molecular changes at topoisomerase loci which result in altered expression are therefore important and recently it has been shown that the topoisomerase II alpha gene is co-amplified along with ERBB2 in a subset of breast adenocarcinomas (Keith et al., 1993).We have previously shown that the lung adenocarcinoma cell line CALU3, has co-amplification of ERBB2 and topoisomerase Ilcc, (Keith et al., 1992). This cell line therefore provides a model to examine the role of topoisomerase Ila amplification and expression in drug sensitivity. We have now investigated the expression, localisation and enzymatic activity of both topoisomerase Ila and P in CALU3 and further characterised the amplicon containing the topoisomerase Ila gene. We show here that the amplified topoisomerase II alpha gene in CALU3 is expressed at a high level and that enzyme activity is inhibited by a topoisomerase II interactive drug. Immunofluorescence studies using antibodies against topoisomerase II alpha and beta show the alpha product to be expressed heterogeneously within the cell population. In contrast, the beta isoform is expressed in all cells and localised to the nucleolus. In addition, we show by fluorescence in situ hybridisation (FISH)