Base-catalyzed isomerization of retinoic acid. Synthesis and differentiation-inducing activities of 14-alkylated all-trans-, 13-cis-, and 20,14-retro-retinoic acids.

Retinoic acid (1) is isomerized regioselectively by excess amounts of lithium diisopropylamide (LDA) to give 20,14-retro-retinoic acid (3). Alkylation of the intermediate dianion of retinoic acid gave 14-alkylated derivatives of 3. By isomerization of the alkylated retro isomers under basic conditions, several 14-alkyl-all-trans- and -13-cis-retinoic acids were synthesized.

Fluorescent probes for retinoic acid receptors: molecular measures for the ligand binding pocket.

Two fluorescent probes for nuclear retinoic acid receptors (RARs) have been developed, both containing a biologically active retinoid moiety and a fluorescent dansyl moiety, but differing in the length of the spacer arm connecting the two moieties. Both probes bind RARs at their retinoid-binding sites, revealing the usefulness of the compounds as fluorescent RAR probes. By measuring the specific increase of the probes' fluorescence intensity caused by the binding to RARs, the linearized length of the RAR's retinoid-binding pocket could be estimated.

Fluorescent and photoaffinity labeling probes for retinoic acid receptors.

A fluorescent probe for retinoid receptors (RARs) was designed and prepared. The probe consists of a retinoid moiety and a dansyl moiety, i.e.

Synthetic retinoids, retinobenzoic acids, Am80, Am580 and Ch55 regulate morphogenesis in chick limb bud.

The retinobenzoic acids Am80, Am580 and Ch55 are synthetic stable analogs of retinoic acid (RA), and show very strong differentiation-inducing activity in human myelogeneous leukemia cell line HL-60. To examine the effects of these synthetic retinoids on limb pattern formation, AG1-X2 beads containing these retinoids were applied to the anterior margin of stage 19-20 chick wing buds. By implanting the beads with 1 microgram/ml retinoids, normal wings were formed and extra digits 2 or 32 were rarely formed.

Retinobenzoic acids. 5. Retinoidal activities of compounds having a trimethylsilyl or trimethylgermyl group(s) in human promyelocytic leukemia cells HL-60.

The retinoidal activities of trimethylsilyl or trimethylgermyl-containing retinobenzoic acids are discussed on the basis of differentiation-inducing activity on human promyelocytic leukemia cells HL-60. Compounds with a trimethylsilyl or trimethylgermyl group at the meta position of the generic formula 2 have more potent activities than the corresponding retinobenzoic acids with a m-tert-butyl group. Compounds having two m-trimethylsilyl or -trimethylgermyl groups also have strong activities, and (E)-4-[3-[3,5-bis(trimethylsilyl)phenyl]-3-oxo-1-propenyl]benzoic acid (22, Ch55S) and (E)-4-[3-[3,5-bis(trimethylgermyl)phenyl]-3-oxo-1- propenyl]benzoic acid (35, Ch55G) are more active than retinoic acid by 1 order of magnitude.

Expression of retinoic acid receptor genes and the ligand-binding selectivity of retinoic acid receptors (RAR's).

Retinoids of a structurally new type, 4-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenylcarbamoyl)benzoic acid (Am80) and (E)-4-[3-(3,5-di-tert-butylphenyl)-3-oxo-1-propenyl]-benzoic acid (Ch55), were used for the investigation of retinoid receptors in some human cell lines. Previously, using these retinoids, we have established that HL-60 cells possess two retinoid receptors, RAR-alpha and RAR-beta. In this paper, we report coexpression of RAR-alpha- and RAR-beta-genes established by Northern analysis.

Retinobenzoic acids. 4. Conformation of aromatic amides with retinoidal activity. Importance of trans-amide structure for the activity.

N-Methylation of two retinoidal amide compounds, 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)carbamoyl]benz oic acid (3, Am80) and 4-[[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2- naphthalenyl)carbonyl]amino]benzoic acid (5, Am580), resulted in the disappearance of their potent differentiation-inducing activity on human promyelocytic leukemia cell line HL-60. Studies with 1H NMR and UV spectroscopy indicated that large conformational differences exist between the active secondary amides and the inactive N-methyl amides. From a comparison of the spectroscopic results of these amides with those of stilbene derivatives, the conformations of the active amides are expected to resemble that of (E)-stilbene, whereas the inactive amides resemble the Z isomer: 3 (Am80) and 5 (Am580) have a trans-amide bond and their whole structures are elongated, while the N-methylated compounds [4 (Am90) and 6 (Am590)] have a cis-amide bond, resulting in the folding of the two benzene rings.

The retinoic acid receptors alpha and beta are expressed in the human promyelocytic leukemia cell line HL-60.

The human promyelocytic leukemia cell line HL-60 can be induced to differentiate into granulocytes upon exposure to retinoids. Previously we have shown that extracts of undifferentiated HL-60 cells possess a specific retinoid-binding activity (RSBP-1) corresponding to an approximate 95 kilodalton (kDa) protein as determined by size-exclusion chromatography. We now extend these observations to reveal a second approximate 95 kDa retinoic acid-binding component (RSBP-2), which is separable from RSBP-1 using anion exchange chromatography.

Retinobenzoic acids. 3. Structure-activity relationships of retinoidal azobenzene-4-carboxylic acids and stilbene-4-carboxylic acids.

Alkyl-substituted azobenzene-4-carboxylic acids are potent differentiation inducers of human promyelocytic leukemia cell line HL-60 to mature granulocytes. Their structure-activity relationships are very similar to those of other retinoidal benzoic acids which are generally represented by 4 and named retinobenzoic acids. The structure-activity relationships of azobenzenecarboxylic acids can also be applied to the known retinoid TTNPB (3).

Retinobenzoic acids. 2. Structure-activity relationships of chalcone-4-carboxylic acids and flavone-4'-carboxylic acids.

The structure-activity relationships of (E)-chalcone-4-carboxylic acids, which are retinoidal benzoic acids represented by R-Ph-X-Ph-COOH (4, X = -COCH = CH-), are discussed on the basis of differentiation-inducing activity on human promyelocytic leukemia cells HL-60. The activity was increased by the substitution of a bulky alkyl group(s) (R), and among such compounds, (E)-4-[3-(3,5-di-tert-butylphenyl)-3-oxo-1-propenyl]benzoic acid (Ch55) and (E)-4-[3-oxo-3-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1 -propenyl]benzoic acid (Ch80) are several times more active than retinoic acid. Though the stable conformer of chalcone derivatives is linear (s-cis form), the conformationally restricted analogue 4-(6,7,8,9-tetrahydro-6,6,9,9-tetramethyl-4H-4-oxonaphtho[2,3-b]py ran-2-yl)benzoic acid (Fv80) is more active than Ch80.

Retinobenzoic acids. 1. Structure-activity relationships of aromatic amides with retinoidal activity.

Two types of aromatic amides, terephthalic monoanilides and (arylcarboxamido)benzoic acids, have been shown to possess potent retinoidal activities and can be classified as retinoids. The structure-activity relationships of these amides are discussed on the basis of differentiation-inducing activity on human promyelocytic leukemia cells HL-60. In generic formula 4 (X = NHCO or CONH), the necessary factors to elicit the retinoidal activities are a medium-sized alkyl group (isopropyl, tert-butyl, etc.

[Recent advances in retinoids studies].

Retinoids are defined as the compounds which elicit the specific biological responses through binding or activating the specific receptor(s). Retinoids modulate the cellular differentiation and proliferation in many types of cells. A series of retinoidal benzoic acids, named retinobenzoic acids, have potent activities on human promyelocytic leukemia cells, HL-60, and other assay systems.

Affinity gels for purification of retinoid-specific binding protein (RSBP).

Retinoids are defined as compounds which elicit specific biological effects such as control of cell growth and cell differentiation by binding to a specific receptor. Recently, we demonstrated the presence of a protein (RSBP) which satisfies the criteria for the retinoid receptor. For purification of RSBP, we prepared two types of affinity gels with retinoidal ligands (Gel-Am and Gel-Ch) based on synthetic retinobenzoic acids which possess very potent retinoidal activities.

Specific uptake of retinoids into human promyelocytic leukemia cells HL-60 by retinoid-specific binding protein: possibly the true retinoid receptor.

The uptake of all-trans-retinoic acid (RA) and two new retinoids [4-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenylcarbamoyl )benzoic acid (Am80) and (E)-4-[3-(3,5-di-tert-butylphenyl)-3-oxo-1-propenyl]benzoic acid (Ch55)] by HL-60 human promyelocytic leukemia cells was investigated. For the investigation, [3H]RA and [3H]Am80 with high specific radioactivities (more than 50 Ci/mmol) were used. [3H]Am80 was prepared by hydrogenolysis of the corresponding chlorinated derivative of Am80 with tritium gas.

Inhibition of ornithine decarboxylase induction by retinobenzoic acids in relation to their binding affinities to cellular retinoid-binding proteins.

Retinobenzoic acids induce differentiation of human promyelocytic leukemia cells (HL-60). Like retinoic acid, 14 retinobenzoic acids inhibited the induction of ornithine decarboxylase (ODC) by teleocidin in mouse skin. The mechanism(s) of inhibition of ODC induction by 7 retinobenzoic acids, Am 80, Am 81, Am 580, Am 590, Am 68, Sa 80, and Ch 55 was compared with those by all-trans-retinoic acid and the arotinoid compound 19.

New benzoic acid derivatives with retinoid activity: lack of direct correlation between biological activity and binding to cellular retinoic acid binding protein.

In this paper the biological activity of several newly synthesized benzoic acid derivatives of the Am- and Ch- series, which are structurally different from retinoic acid and arotinoids, was examined. These compounds inhibit squamous cell differentiation of rabbit tracheal epithelial cells in vitro as indicated by the inhibition of transglutaminase Type I and cholesterol 3-sulfate levels. In contrast to the inhibition of differentiation in rabbit tracheal cells, these compounds induce differentiation of mouse embryonal carcinoma F9 and human promyelocytic leukemia HL60 cells.

[Regulation of cell growth by retinoids and gene expression].

Retinoids are compounds that can elicit specific biological responses by virtue of their binding to and activating a specific receptor or a set of receptors. Retinoids produce various specific biological effects, including induction of terminal differentiation, regulation of cell proliferation, regulation of gene expression and regulation of the activity of specific enzymes in cells. In this article, the effects of retinoids on gene expression are reviewed.

Mechanism of action of retinoids.

In several recent reviews, we have suggested that the mechanism of action of retinoids in controlling cell differentiation is related to their effects on the expression of oncogenes and peptide growth factors. It is currently believed that oncogenes control metabolic pathways that involve peptide growth factors and their receptors, as well as postreceptor signaling mechanisms. Retinoids, therefore, have been valuable probes to study the function of oncogenes and peptide growth factors.