In vitro treatment with retinoids decreases bcl-2 protein expression and enhances dexamethasone-induced cytotoxicity and apoptosis in multiple myeloma cells

All-trans retinoic acid (ATRA) has been shown to inhibit in vitro growth of multiple myeloma (MM) cells, and this effect can be further potentiated by the addition of Dexamethasone (DEX). We here extended this study by testing the activity of 9-cis retinoic acid (9-cis RA) and 13-cis retinoic acid (13-cis RA), both alone and in combination with DEX, in two MM cell lines, U266 and RPMI 8226. Furthermore, we aimed at investigating the mechanisms involved in the interactions of retinoids and DEX in this setting. 9-cis RA appeared to be the most active agent in U266 cell line (IC50 = 1.2 mumol/l vs 10.5 and 9.8 mumol/l obtained with ATRA and 13-cis RA, respectively) while, in RPMI 8226 cell line, 9-cis RA and 13-cis RA were almost equally cytotoxic (IC50 = 1 and 0.8 mumol/l) and ATRA was less effective. Co-incubation with DEX resulted in a synergistic cytotoxic activity in both the cell lines except for the combinations DEX + 9-cis RA in U266 cell line and DEX + 13-cis RA in RPMI 8226 cell line, where the effect was merely additive. A synergistic cytotoxic effect of retinoids and DEX was also observed on fresh MM cells obtained from 7 patients. Both retinoids and DEX are known to be inducers of apoptosis; we verified that the combined inhibitory activity of retinoids and DEX could be attributed to an increased induction of apoptosis. This effect may be mediated by a reduced intracellular expression of BCL-2 protein, which indeed observed after prolonged in vitro treatment with retinoids. It has been described recently that an enhanced expression of BCL-2 protein can contribute to the occurrence of early chemoresistance; the downregulation of BCL-2 protein induced by retinoids could thus be exploited, by means of novel chemotherapy plus retinoids combinations, in order to improve the efficacy of conventional chemotherapy in MM.     

Retinoids (all-trans and 9-cis retinoic acid) stimulate production of macrophage colony-stimulating factor and granulocyte-macrophage colony- stimulating factor by human bone marrow stromal cells

Retinoic acids (RAs) exert pleiotropic effects on cellular growth and differentiation. All-trans retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA), a stereoisomer of ATRA, induce differentiation of leukemic cell lines and cells from patients with acute myelogenous leukemia (AML) in vitro. Despite information on the effects of RAs on hematopoietic cells, little is known about how RAs act on the hematopoietic microenvironment, especially on bone marrow stromal cells. Based on recent observations that various cytokines produced mainly by bone marrow stromal cells regulate hematopoiesis, we analyzed the effects of RAs on cytokine production by these cells. ATRA or 9-cis RA treatment of human bone marrow stromal cell line KM101, which produces macrophage colony-stimulating factor (M-CSF) and granulocyte- macrophage colony-stimulating factor (GM-CSF) constitutively, enhanced mRNA levels of both cytokines in a dose-dependent manner. Both RAs also stimulated M-CSF production from primary cultures of human bone marrow stromal cells. Both retinoic acid receptor (RAR)-alpha and retinoid X receptor (RXR)-alpha were expressed constitutively in KM101 cells. ATRA did not affect the expression of either receptor, whereas 9-cis RA increased RXR-alpha mRNA expression in a dose-dependent manner, but did not affect levels of RAR-alpha mRNA. These findings may have important biologic implications for both the role of RAs in hematopoiesis and the therapeutic effects of ATRA on the hematopoietic microenvironment in patients with acute promyelocytic leukemia (APL).     

Additive Inhibitory Effect of Experimentally Induced Hepatic Cirrhosis by Agonists of Peroxisome Proliferator Activator Receptor γ and Retinoic Acid Receptor

Peroxisome proliferator activator receptor (PPAR) ligands prevent liver fibrosis, while the role of all-trans retinoic acid (ATRA) and its metabolite 9-cis retinoic acid (9-cis RA) is less clear. We have investigated the ability of the combination of PPARγ ligand rosiglitazone (RSG) and of ATRA to prevent liver fibrosis. In vivo treatment with RSG or ATRA reduced fibrotic nodules, spleen weight, and hydroxyproline levels in rat model of thioacetamide-induced liver fibrosis. The combination of ATRA + RSG caused the strongest inhibition, accompanied by decreased expression of collagen I, α-smooth muscle actin, TGFβ1, and TNFα. In vitro studies showed that PPARγ ligand 15-deoxy-Δ12,14-prostaglandinJ(2)[PJ(2)] and RXR ligand 9-cis RA or PJ(2) and ATRA inhibited proliferation of hepatic stellate cells HSC-T6. 9-cis RA inhibited c-jun levels and also inhibited expression of its receptor RXRα in HSC-T6 cells. The combination of PPAR-γ and RAR agonists demonstrated an additive effect in the inhibition of TAA-induced hepatic fibrosis, due to inhibition of HSC proliferation and reduction of profibrotic TGFβ1 and proinflammatory TNFα.     

All-trans retinoic acid at low concentration directly stimulates normal adult megakaryocytopoiesis in the presence of thrombopoietin or combined cytokines.

In order to investigate the direct effects of retinoids on normal adult hematopoietic progenitors, purified CD34+ cells were seeded in serum-free cultures in the presence of pharmacological (10(-6)) M or physiological (10(-12)) M concentrations of all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA) plus combinations of specific cytokines. 10(-6) M ATRA and 9-cis RA significantly decreased the number of granulomacrophagic, erythroid and megakaryocytic (CFU-meg) progenitors. On the other hand, 10(-12) M ATRA significantly promoted the growth of CFU-meg, in the presence either of thrombopoietin or of IL-3+ GM-CSF, and induced a reproducible stimulation of the immature CD34+DR- subset. In conclusion, our findings suggest that retinoic acids probably play a direct role in normal adult hematopoietic development at both physiological and pharmacological concentrations. The stimulatory effect on megakaryocytopoiesis should be considered in the perspective of a potential use of low-dose ATRA, combined with thrombopoietin or other cytokines, in pathological conditions where the megakaryocytic compartment is impaired and the stimulation of megakaryocytopoiesis is requested.     

Superior effect of 9‐cis retinoic acid (RA) compared with all‐trans RA and 13‐cis RA on the inhibition of clonogenic cellgrowth and the induction of apoptosis in OCI/AML‐2 subclones: is the p53 pathway involved?

In the present study, the effects of 9-cis retinoic acid (RA) and 13-cis RA on acute myeloblastic leukaemia (AML) cell growth and the induction of apoptosis as well as its relationship with bcl-2 and p53 were compared with those of all-trans RA (ATRA). The study was performed with the subclones of the retinoid-sensitive OCI/AML-2 cell line. The most prominent inhibitory effect on clonogenic cell growth and morphological apoptosis was shown by 9-cis RA. In addition, Western blotting revealed the most obvious translocation of p53 from cytosol to nucleus in the case of 9-cis RA, which was the only retinoid able to change the conformation of p53 from mutational to wild type, as demonstrated by flow cytometry. There was no difference between the retinoids in the downregulation of bcl-2 as analysed by Western blotting and flow cytometry. The RA receptor (RAR)-alpha antagonist had no effect on apoptosis in any of the three retinoids studied using the annexin V method. In conclusion, this study shows that 9-cis RA was a more potent agent than ATRA or 13-cis RA in inducing growth arrest and apoptosis in the OCI/AML-2 subclones. The effect was associated with the downregulation of bcl-2 and was hardly mediated through the RAR-alpha receptor, but might be related to the activation of p53.     

Retinoids induce fibroblast growth factor-2 production in endothelial cells via retinoic acid receptor alpha activation and stimulate angiogenesis in vitro and in vivo

The effect of retinoic acid (RA) on endothelial cells is still controversial and was examined in the present study. In bovine aortic endothelial cells (BAECs), all-trans RA (ATRA) and 9-cis RA (9CRA), but not 13-cis RA (13CRA), induced fibroblast growth factor-2 (FGF-2) production and exhibited a biphasic dose-dependent effect to enhance BAEC proliferation and differentiation into tubular structures on reconstituted basement membrane proteins (Matrigel); both processes were inhibited by FGF-2-neutralizing antibody. The pan RA receptor (RAR)-selective ligand (E)-4-[2-(5,5,8,8,-tetramethyl-5,6,7,8-tetrahydro-2-naphtalenyl)-1-propenyl] benzoic acid and the RARalpha-selective ligand 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphtyl)-ethenyl] benzoic acid stimulated the production of FGF-2, whereas the addition of the RARalpha-antagonist RO 41-5253 inhibited this effect. In BAECs, the forced expression of RARalpha, but not RARbeta or RARgamma, enhanced FGF-2 production, whereas the RARalpha-dominant negative, Delta403, blocked this effect. Furthermore, RARalpha overexpression directly stimulated BAEC differentiation on Matrigel and potentiated the effects of ATRA in this assay. Finally, ATRA-treated BAECs coinjected with Matrigel subcutaneously in mice induced neovascularization within the Matrigel plug, and ATRA also enhanced angiogenesis in the chicken chorioallantoic membrane assay. In conclusion, RA can stimulate endothelial cell proliferation and differentiation in vitro via enhanced RARalpha-dependent FGF-2 production, and it can also induce angiogenesis in vivo. The full text of this article is available at http://www.circresaha.org.     

All-trans and 9-cis retinoic acid alter rat hepatic stellate cell phenotype differentially

BACKGROUND: Hepatic stellate cells exert specific functions in the liver: storage of large amounts of retinyl esters, synthesis and breakdown of hepatic extracellular matrix, secretion of a variety of cytokines, and control of the diameter of the sinusoids. AIMS: To examine the influence of all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9RA) on extracellular matrix production and proliferation of activated hepatic stellate cells. METHODS: Cells were isolated using collagenase/pronase, purified by centrifugation in nycodenz, and cultured for two weeks. At this time point the cells exhibited the activated phenotype. Cells were exposed to various concentrations of ATRA and 9RA. The expression of procollagens I, III, and IV, of fibronectin and of laminin were analysed by immunoprecipitation and northern hybridisation. RESULTS: ATRA exerted a significant inhibitory effect on the synthesis of procollagens type I, III, and IV, fibronectin, and laminin, but did not influence stellate cell proliferation, whereas 9RA showed a clear but late effect on proliferation. 9RA increased procollagen I mRNA 1.9-fold, but did not affect the expression of other matrix proteins. CONCLUSION: Results showed that ATRA and 9RA exert different, often contrary effects on activated stellate cells. These observations may explain prior divergent results obtained following retinoid administration to cultured stellate cells or in animals subjected to fibrogenic stimuli.     

Dual action of retinoic acid on human embryonic/fetal hematopoiesis: blockade of primitive progenitor proliferation and shift from multipotent/erythroid/monocytic to granulocytic differentiation program

In preliminary studies, we have analyzed the hematopoietic growth factor (HGF) requirement of hematopoietic progenitor cells (HPCs) purified from embryonic-fetal liver (FL) and grown in fetal calf serum- supplemented (FCS+) clonogenic culture. The key role of erythropoietin (Epo) for colony formation by early erythroid progenitors (burst- forming units-erythroid [BFU-E]) has been confirmed. Furthermore, in the absence of exogenous HGFs, FL monocytic progenitors (colony-forming unit monocyte [CFU-M]) generate large colonies exclusively composed of monocytes-macrophages; these colonies are absent in FCS- clonogenic culture. On this basis, we have investigated the role of all-trans retinoic acid (ATRA) and its isomer 9-cis RA in FL hematopoiesis. Both compounds modulate the growth of purified FL HPCs, which show a dose- dependent shift from mixed/erythroid/ monocytic to granulocytic colony formation. Studies on unicellular and paired daughter cell culture unequivocally indicate that the shift is mediated by modulation of the HPC differentiation program to the granulopoietic pathway (rather than RA-induced down-modulation of multipotent/ erythroid/monocytic HPC growth coupled with recruitment of granulocytic HPCs). ATRA and 9-cis RA also exert their effect on the proliferation of primitive HPCs (high- proliferative potential colony-forming cells [HPP-CFCs]) and putative hematopoietic stem cells (HSCs; assayed in Dexter-type long-term culture). High concentrations of either compound (1) drastically reduced the number of primary HPP-CFC colonies and totally abolished their recloning capacity and (2) inhibited HSC proliferation. It is crucial that these results mirror recent observations indicating that murine adult HPCs transduced with dominant negative ATRA receptor (RAR) gene are immortalized and show a selective blockade of granulocytic differentiation. Altogether, these results suggest that ATRA/9-cis RA may play a key role in FL hematopoiesis via a dual effect hypothetically mediated by interaction with the RAR/RXR heterodimer, ie, inhibition of HSC/ primitive HPC proliferation and induction of CFU- GEMM/ BFU-E/CFU-M shift from the multipotent/erythroid/monocytic to the granulocytic-neutrophilic differentiation program.     

Retinoic acid is a negative regulator for the differentiation of cord blood-derived human mast cell progenitors

We examined the effects of retinoids on the human mast cell development using a serum-deprived culture system. When 10-week cultured mast cells derived from CD34(+) cord blood cells were used as target cells, both all-trans retinoic acid (ATRA) and 9-cis RA inhibited the progeny generation under stimulation with stem cell factor (SCF) in a dose-dependent manner (the number of progeny grown by SCF plus RA at 10(-7) mol/L was one tenth of the value obtained by SCF alone). The early steps in mast cell development appear to be less sensitive to RA according to the single CD34(+)c-kit(+) cord blood cell culture study. The optimal concentration of RAs also reduced the histamine concentration in the cultured mast cells (3.00 +/- 0.47 pg per cell in SCF alone, 1.44 +/- 0.18 pg per cell in SCF+ATRA, and 1.41 +/- 0.10 pg per cell in SCF+9-cis RA). RT-PCR analyses showed the expression of RARalpha, RARbeta, RXRalpha, and RXRbeta messenger ribonucleic acid (mRNA) in 10-week cultured mast cells. The addition of an RAR-selective agonist at 10(-10) mol/L to 10(-7) mol/L decreased the number of mast cells grown in SCF, whereas an RXR-selective agonist at up to 10(-8) mol/L was inactive. Among RAR subtype selective retinoids used at 10(-9) mol/L to 10(-7) mol/L, only the RARalpha agonist was equivalent to ATRA at 10(-7) mol/L in its ability to inhibit mast cell growth. Conversely, the addition of excess concentrations of a RARalpha antagonist profoundly counteracted the retinoid-mediated suppressive effects. These results suggest that RA inhibits SCF-dependent differentiation of human mast cell progenitors through a specific receptor. (Blood. 2000;95:2821-2828)     

Retinoids and retinol differentially regulate steroid biosynthesis in ovarian theca cells isolated from normal cycling women and women with polycystic ovary syndrome

CONTEXT: Polycystic ovary syndrome (PCOS) is characterized by ovarian androgen excess and infertility. Recent experiments have suggested that several genes involved in retinoic acid synthesis may be differentially expressed in PCOS theca cells and may contribute to excessive theca-derived androgen production. OBJECTIVE: The study was performed to examine whether there are differential effects of retinol and retinoids on normal and PCOS theca cell function. DESIGN: We used in vitro assays. SETTING: The study was conducted at the university laboratory. PATIENTS: We studied theca interna cells isolated from normal-cycling women and women with PCOS. INTERVENTIONS: Theca cells were treated with all-trans-retinoic acid (atRA), 9-cis retinoic acid (9-cis RA), or the retinoic acid precursor retinol. MAIN OUTCOME MEASURE(S): We measured dehydroepiandrosterone, testosterone, and progesterone biosynthesis as well as cytochrome P450 17alpha-hydroxylase (CYP17), cytochrome P450 cholesterol side-chain cleavage, and steroidogenic acute regulatory protein mRNA abundance and promoter function. RESULTS: Dehydroepiandrosterone production was increased by atRA and 9-cis RA in normal cells and by atRA, 9-cis RA, and retinol in PCOS. Testosterone production was increased by atRA in normal and by atRA, 9-cis RA, and retinol in PCOS. Progesterone production was not altered by retinoid treatment. Retinoids stimulated mRNA abundance and promoter function for CYP17 and steroidogenic acute regulatory protein in both cell types and cytochrome P450 cholesterol side-chain cleavage in normal cells. Retinol stimulated CYP17 mRNA accumulation and promoter function in PCOS but not normal theca cells. P < 0.05 was considered statistically significant. CONCLUSIONS: Differential responses to retinol and retinoids in normal and PCOS theca suggest that altered retinoic acid synthesis and action may be involved in augmented CYP17 gene expression and androgen production in PCOS.     

All-trans retinoic acid in acute promyelocytic leukemias. II. In vitro studies: structure-function relationship

All-trans retinoic acid induces leukemic cells from patients with acute promyelocytic leukemia (M3) to differentiate in vitro to mature granulocytes which express the CD15 antigen and are capable of respiratory burst function. Of 35 M3 samples, only one failed to respond. In eight cases, we compared the efficacy of two naturally occurring isomers of retinoic acid, all-trans RA and 13-cis RA. Both isomers induce maximal differentiation at 10(-6) mol/L. The maximal response was maintained at 10(-7) mol/L for the all-trans but not for the 13-cis RA. We also observed that the metabolites 4-oxo-all-trans and 4-oxo-13-cis were effective at 10(-6) mol/L. This 1 order of magnitude difference in the in vitro differentiating potencies of all-trans RA and 13-cis RA in the blasts of promyelocytic leukemias predicts a difference in the clinical efficacy of the two drugs.     

Retinoic acid treatment of human leiomyoma cells transformed the cell phenotype to one strongly resembling myometrial cells

Background  Uterine leiomyomas are clinically significant tumours that may develop due to an altered differentiation pathway. We have previously identified a dysregulated retinoic acid (RA) pathway that reduced retinoic exposure in human leiomyoma surgical specimens, and have shown that the leiomyoma phenotype was characterized by excessive and disorganized extracellular matrix (ECM).
Objective  The goal of this study was to determine the impact of RA exposure on the disrupted ECM phenotype of leiomyomas.
Design and methods  Study of immortalized and molecularly confirmed cells generated from surgical specimens of spontaneous uterine leiomyoma and matched myometrium.
Results  Immortalized leiomyoma and myometrial cells retained the molecular characteristics of their progenitor tissue. Proliferation of leiomyoma cells was inhibited by all -trans retinoic acid (ATRA). Furthermore, there was a dose-dependent decrease in soluble extracellular collagen protein in ATRA-treated leiomyoma cells. Exposure of leiomyoma cells to ATRA resulted in a dose-dependent inhibition of templates for specific ECM protein production including collagen 1, collagen 4, fibronectin and versican. Notably, expression levels in treated leiomyoma cells approached those found in myometrial cells. These mRNA alterations translated into altered protein. Down-regulation was also observed among the RA pathway genes such as CYP26A1 with exposure to ATRA. Finally, ATRA down-regulated TGF-β3 mRNA expression and the TGF-β regulated genes in leiomyoma cells.
Conclusion  Exposure of leiomyomas to ATRA down-regulated cell proliferation, ECM formation, RA metabolism and TGF-β regulation, suggesting that RA exposure can alter the leiomyoma phenotype to one that more closely approximates normal myometrium.     

Novel retinoic acid, 9-cis retinoic acid, in combination with all-trans retinoic acid is an effective inducer of differentiation of retinoic acid-resistant HL-60 cells

Recent studies have shown that a high proportion of patients with acute promyelocytic leukemia (APL) achieve complete remission after treatment with all-trans retinoic acid (RA). Nevertheless, despite an initial good response, most patients that received continuous treatment with all-trans RA relapse and develop RA-resistant disease. The 9-cis RA is a high-affinity ligand for retinoid X receptors (RXRs) and also binds efficiently to retinoic acid receptors (RARs); all-trans RA is a ligand for RARs. Both alone are able to induce differentiation of wild-type HL- 60 cells. We found that neither all-trans RA nor 9-cis RA (< 2 x 10(-6) mol/L) induced differentiation of RA-resistant HL-60 cells into either mature granulocytes or monocytes. However, morphologic differentiation of the RA-resistant HL-60 cells was induced by 10(-6) mol/L all-trans RA combined with various concentrations (10(-12) to 10(-6) mol/L) of 9- cis RA. Electron microscopic examination also confirmed that the combination of both retinoids induced RA-resistant HL-60 cells to differentiate to mature granulocytes. Functional analysis of differentiation (NBT reduction activity) confirmed the necessity of both analogs to induce differentiation. Also, expression of myeloid- specific differentiation antigens (CD11b and CD14) as well as migration inhibitory factor-related protein (MRP)-8/14 mRNAs were upregulated only in the presence of both retinoids in a dose-dependent manner. In these conditions 3H-thymidine incorporation was inhibited and numbers of viable cells were decreased, suggesting that all-trans RA with 9-cis RA may inhibit cell growth and induce differentiation of RA-resistant HL-60 cells into mature granulocytes. These studies suggest that 9-cis RA in combination with all-trans RA is an effective inducer of RA- resistant HL-60 cells and may have implications for both the biology of retinoids and clinical treatment of RA-resistant acute myelogenous leukemia, including APL patients.     

Hyperthermia induces heat-shock protein expression, reduces pancreatic injury, and improves survival in necrotizing pancreatitis

Heat-shock proteins (HSPs) function in the cellular response to injury. Increased expression of these proteins was first described in response to hyperthermia, although their production may be prompted by a variety of metabolic insults. HSPs protect cellular proteins from degradation. The self-limited pancreatitis induced by hyperstimulation with supramaximal doses of cerulein is accompanied by increased HSP expression. It may be that HSPs serve a protective function in pancreatitis. We hypothesized that hyperthermia-induced production of HSP-70 would improve survival in a lethal murine model of necrotizing pancreatitis. Necrotizing pancreatitis was induced in two groups of 30 female Swiss Webster mice by feeding them a choline-deficient diet supplemented with 0.5 g% ethionine (CDE) for 72 hours. Immediately before initiation of the CDE diet, the core body temperatures of the mice in the experimental group were elevated to 42 degrees C for 12.5 minutes. Twenty mice from each group were killed after 24 hours. Pancreata were harvested, and pancreatic proteins were extracted from half of the pancreata. HSP-70 was assessed according to a standard Western blotting protocol. The remaining pancreata were used to make histologic comparisons. Serum interleukin 6 and tumor necrosis factor-alpha were determined by enzyme-linked immunosorbent assay (ELISA). Survival was determined by observation of the remaining mice. HSP-70 was expressed in pancreatic protein from all mice exposed to hypothermia but in none of the mice subjected to the CDE diet alone. Mortality was significantly reduced in mice pretreated with hyperthermia compared with control mice (p < 0.05). Survival in the hyperthermia group was 80%, whereas in the control group it was 30%. Hyperthermia resulted in expression of pancreatic HSP-70 in mice. Hyperthermia also reduced mortality in this lethal murine model of necrotizing pancreatitis. It is plausible that a causal relationship exists between HSP-70 production and improved survival in this model.     

9-cis retinoic acid induces complete remission but does not reverse clinically acquired retinoid resistance in acute promyelocytic leukemia

9-cis retinoic acid (RA) is a high-affinity ligand for both retinoic acid receptors (RARs) and retinoid "X" receptors (RXRs). Although all- trans RA does not bind to RXRs, RAR/RXR heterodimers or RXR/RXR homodimers bind to specific DNA response elements and modulate proliferation and differentiation of normal and malignant cells. Because the development of clinical resistance to all-trans RA has been associated with a progressive decrease in plasma drug concentrations, we evaluated the ability of 9-cis RA to induce in vitro cytodifferentiation in subclones of a retinoid-sensitive and resistant APL cell line (NB4) and in short-term cultures of fresh leukemic cells aspirated from patients. We also evaluated the clinical activity and pharmacokinetics of 9-cis RA (LGD 1057) in patients with APL who were previously treated with all-trans RA. In vitro tests of both retinoid- sensitive NB4 cells, as well as samples of fresh cells from 11 patients with APL, showed relatively equivalent degrees of sensitivity to both 9- cis RA and all-trans RA at concentrations ranging from 10(-6) to 10(-8) mol/L; however, no substantial cytodifferentiation was observed using either drug alone or in combination (10(-6) mol/L of each) in retinoid- resistant NB4 cells. Seven patients with APL who had previously relapsed from a remission induced by all-trans RA were treated with 9- cis RA at daily oral doses ranging from 30 to 230 mg/m2. Pharmacokinetic studies showed that the mean terminal plasma half-life of 9-cis RA (1.3 hours) changed very little after several weeks of dosing, although the mean change per dose level in area under the plasma concentration x time curves and peak plasma concentrations showed a decrease by 49% and 45%, respectively. Peak plasma concentrations equaled or exceeded concentrations that were effective against retinoid-sensitive cells in vitro. Despite these favorable pharmacokinetic results, only one of the seven patients achieved complete remission, corroborating in vitro studies of blasts from three of the nonresponders that showed a relatively equivalent degree of resistance to both retinoids. Our results suggest that while 9-cis RA may not induce its own catabolism to the same degree as all-trans RA, this feature does not appear to overcome clinically acquired resistance to all-trans RA in APL. Nonetheless, the drug can induce complete remissions in patients with APL and may be useful for extended therapy in other diseases. Future studies should address the use of lower doses in patients who have not previously received retinoid therapy.(ABSTRACT TRUNCATED AT 400 WORDS)     

全反式维甲酸对肝癌细胞HepG2的分化、侵袭迁移的影响

目的:探讨全反式维甲酸(ATRA)对肝癌细胞HepG2的诱导分化作用及侵袭迁移的影响.方法:MTT法测定ATRA对肝癌细胞HepG2的抑制作用;平皿集落形成法检测ATRA对HepG2细胞锚定依赖性生长作用;ELISA法检测ATRA作用前后HepG2 AFP分泌量的变化;RT-PCR检测ATRA对HepG2细胞MMP-9及Nanog的mRNA表达的影响;Western blot检测ATRA对HepG2细胞MMP-9及Nanog蛋白表达的影响;Transwell及划痕实验检测其对侵袭及迁移能力的影响.结果:MTT法显示ATRA抑制体外培养人肝癌细胞HepG2细胞生长,呈剂量和时间依赖性;ELISA显示ATRA诱导HepG2细胞分化和凋亡,使代表肝细胞恶变的AFP分泌量明显下降(P<0.05);平皿克隆形成实验结果表明未经ATRA处理的HepG2可形成克隆,但经ATRA刺激后,其形成克隆变小且数目明显减少;ATRA呈时间及浓度依赖性下调Nanog mRNA及蛋白的表达,并在24h呈浓度依赖性下调MMP-9 mRNA及蛋白表达;Transwell实验和划痕实验结果显示ATRA能抑制HepG2细胞的侵袭和迁移能力.结论...