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
Modifications around the dipeptide-mimetic core of a hydroxamic acid based matrix metalloproteinase inhibitor were studied. These variations incorporated a variety of natural, unnatural, and synthetic amino acids in addition to modifications of the P1' and P3' substituents. The results of this study indicate the following structural requirements: (1) Two key hydrogen bonds must be present between the enzyme and potent substrates. (2) Potent inhibitors must possess strong zinc-binding functionalities. (3) The potential importance of the hydrophobic group at position R3 as illustrated by its ability to impart greater relative potency against stromelysin when larger hydrophobic groups are used. (4) Requirements surrounding the nature of the amino acid appear to be more restrictive for stromelysin than for neutrophil collagenase, 72 kDa gelatinase, and 92 kDa gelatinase. These requirements may involve planar fused-ring aryl systems and possibly hydrogen-bonding capabilities.
