ABSTRACT
The retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (AHPN) is reported to have anticancer activity in vivo. Induction of cell cycle arrest and apoptosis in cancer cell lines refractory to standard retinoids suggests a retinoid-independent mechanism of action for AHPN. Conformational studies suggested that binding of AHPN does not induce an unusual conformation in retinoic acid receptor (RAR) gamma. The 3-chloro AHPN analogue MM11453 inhibited the growth of both retinoid-resistant (HL-60R leukemia, MDA-MB-231 breast, and H292 lung) and retinoid-sensitive (MCF-7 breast, LNCaP prostate, and H460 lung) cancer cell lines by inducing apoptosis at similar concentrations. Before apoptosis, MM11453 induced transcription factor TR3 expression and loss of mitochondrial membrane potential characteristic of apoptosis. MM11453 lacked the ability to significantly activate RARs and retinoid X receptor alpha to initiate (TREpal)(2)-tk-CAT reporter transcription. These results, differential proteolysis-sensitivity assays, and glutathione S-transferase-pulldown experiments demonstrate that, unlike AHPN or the natural or standard synthetic retinoids, MM11453 does not behave as a RAR or retinoid X receptor alpha transcriptional agonist. These studies strongly suggest that AHPN exerts its cell cycle arrest and apoptotic activity by a signaling pathway independent of retinoid receptor activation.
Subject(s)
Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Receptors, Retinoic Acid/genetics , Retinoids/pharmacology , Transcriptional Activation/drug effects , Antineoplastic Agents/chemistry , Antineoplastic Agents/metabolism , Cell Division/drug effects , DNA-Binding Proteins/biosynthesis , Growth Inhibitors/pharmacology , HL-60 Cells , HeLa Cells , Humans , Intracellular Membranes/drug effects , Intracellular Membranes/physiology , Jurkat Cells , Membrane Potentials/drug effects , Mitochondria/drug effects , Mitochondria/physiology , Molecular Conformation , Nuclear Receptor Subfamily 4, Group A, Member 1 , Protein Conformation , Proto-Oncogene Proteins c-bcl-2/biosynthesis , Proto-Oncogene Proteins c-bcl-2/genetics , Proto-Oncogene Proteins c-bcl-2/physiology , Receptors, Cytoplasmic and Nuclear , Receptors, Retinoic Acid/agonists , Receptors, Retinoic Acid/biosynthesis , Receptors, Retinoic Acid/metabolism , Receptors, Steroid , Retinoids/metabolism , Transcription Factors/biosynthesisABSTRACT
Aromatic retinoids having a meta-substituted aromatic ring bridge, such as 4-[3-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)phenyl]benzo ic acid and its 3,5-diaryl-substituted 4,5-dihydroisoxazole analogue, function as retinoid receptor panagonists by activating both retinoic acid and retinoid X receptors to induce gene transcription, and thereby provide novel scaffolds for retinoid drug development. Both classes of these ligand-inducible transcription factors are involved in mediating the inhibitory effects of retinoids on cancer cell growth.
Subject(s)
Benzoates/pharmacology , Heterocyclic Compounds/pharmacology , Naphthalenes/pharmacology , Receptors, Retinoic Acid/agonists , Transcription Factors/agonists , Benzoates/chemistry , Heterocyclic Compounds/chemistry , Humans , Naphthalenes/chemistry , Retinoid X Receptors , Tumor Cells, CulturedABSTRACT
Patterns of growth and regeneration in 2-, 4-, 8-, and 17-week-old murine dystrophic (129 ReJ dy/dy) extensor digitorum longus muscles have been determined. Necrosis and myofiber loss, hypertrophy, and regeneration result in a reduced population of myofibers whose diameter distribution is more extensive than that found in the extensor digitorum longus muscles of age-matched normal mice. At the onset of dystrophic symptoms (2 weeks postnatal), the ratio of myosatellite cell nuclei to the total sublaminal nuclear population (myonuclei + myosatellite cells) is similar to that found in 2-week-old control muscles. The frequency of finding myosatellite cells decreases with age in both control and dystrophic muscles. Myosatellite cells account for 11%, 6%, 5%, and 3% of the total sublaminal nuclear population in control muscle and 12%, 8%, 6%, and 5% of the total sublaminal nuclear population in dystrophic muscle at 2, 4, 8, and 17 weeks, respectively. No preferential association of myosatellite cells with myofibers of a particular diameter is found in control muscle or in the two youngest dystrophic groups. At 8 and 17 weeks, myosatellite cells are less frequently encountered on small-diameter, regenerating myofibers of dystrophic muscle, and they are preferentially associated with large diameter, hypertrophied myofibers. The labeling index of myosatellite cells decreases with age in both normal and dystrophic muscle. At all ages the myosatellite cell labeling index is higher in dystrophic muscle (23%, 7%, 5%, and 2% at 2, 4, 8, and 17 weeks, respectively) than in normal muscle (5%, less than 1% at 2 and 4 weeks, respectively), with no labeled myosatellite cells being found in 8- and 17-week-old normal muscles. It is suggested that the magnitude of the regenerative response of dystrophic murine muscle decreases with age and that this factor may be responsible for the inability of the regenerative response of dystrophic muscle to keep pace with the rapid muscle deterioration.
Subject(s)
Mice, Mutant Strains , Muscles/pathology , Muscular Dystrophy, Animal/pathology , Rodent Diseases/pathology , Animals , Cell Count/veterinary , Female , Mice , Microscopy, Electron , Muscles/cytology , Muscles/physiology , RegenerationABSTRACT
Three-dimensional reconstructions of "regenerating" myotubes in the "degeneration-regeneration" regions and in the "regenerative" foci of the extensor digitorum longus muscle of the C57BL6J/dy2J myopathic mutant mouse were made from spaced serial ultrathin section. Complex branching and recombination occurred, involving myotubes which for extensive regions along their length appeared to be independent. No accumulation of specialized organelles occurred at the branching site. Continuous branches displayed multiple discrete motor endplates.
