Synthesis, structure-activity relationships, and RARgamma-ligand interactions of nitrogen heteroarotinoids

J Med Chem. 1999 Sep 9;42(18):3602-14. doi: 10.1021/jm9900974.

Abstract

Three heteroarotinoids containing a nitrogen atom in the first ring and a C-O linking group between the two aryl rings were synthesized and evaluated for RAR and RXR retinoid receptor transactivation, tumor cell growth inhibition, and transglutaminase (TGase) induction. Ethyl 4-(N,4,4-trimethyl-1,2,3,4-tetrahydroquinolinyl)benzoate (1) contained an N-CH(3) group and activated all retinoid receptors except for RARgamma. Inceasing the hydrophobicity around the rings with analogues ethyl 4-(N,4,4,7-tetramethyl-1,2,3, 4-tetrahydroquinolin-6-oyloxy)benzoate (2) [7-methyl group added] and ethyl 4-(4,4-dimethyl-N-isopropyl-1,2,3, 4-tetrahydroquinolin-6-oyloxy)benzoate (3) [NCH(CH(3))(2) group at C-4] increased the potency and specificity for RARalpha, RARbeta, and RXRalpha, compared to 1, but had little effect on RXRbeta and RXRgamma activation. Although 1 and 3 were unable to activate RARgamma, 2 did activate this receptor with efficacy and high potency equal to that of 9-cis-retinoic acid (9-c-RA). All three heteroarotinoids exhibited 5-8-fold greater specificities for RARbeta over RARalpha. In addition, esters 1-3 inhibited the growth of two cell lines each derived from cervix, vulvar, ovarian, and head/neck tumors with similar efficiencies to that of 9-c-RA through a mechanism independent of apoptosis. The vulvar cell lines were the most sensitive, and the ovarian lines were the least sensitive. Ester 2 was similar to 1 and 3 except that 2 was a much more potent growth inhibitor of the two vulvar cell lines, which is consistent with strong RARgamma activation by 2 (but not by 1 and 3) and the high levels of RARgamma expression in skin. All three heteroarotinoids induced production of TGase, a marker of retinoid activity in human erythroleukemic cells. Esters 2 and 3 were the more potent TGase activators than 1, in agreement with the stronger activation of the RAR receptors by 2 and 3. The biological activities of these agents, and the RARgamma potency of 2 in particular, demonstrate the promise of these compounds as pharmaceutics for cancer and skin disorders.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antineoplastic Agents / chemical synthesis
  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects
  • Cell Division / drug effects
  • Humans
  • Ligands
  • Models, Molecular
  • Quinolines / chemical synthesis*
  • Quinolines / pharmacology
  • Receptors, Retinoic Acid / metabolism*
  • Retinoic Acid Receptor gamma
  • Retinoid X Receptors
  • Retinoids / chemical synthesis*
  • Retinoids / pharmacology
  • Structure-Activity Relationship
  • Transcription Factors / metabolism
  • Transcriptional Activation / drug effects
  • Transglutaminases / genetics
  • Transglutaminases / metabolism
  • Tumor Cells, Cultured

Substances

  • Antineoplastic Agents
  • Ligands
  • Quinolines
  • Receptors, Retinoic Acid
  • Retinoid X Receptors
  • Retinoids
  • Transcription Factors
  • Transglutaminases