MOLECULAR AND CELLULAR INTERACTION OF THE DIFFERENTIATING ANTITUMOR AGENT DIMETHYLCROCETIN WITH NUCLEAR RETINOIC ACID RECEPTOR AS STUDIED BY NEAR-INFRARED AND VISIBLE SERS SPECTROSCOPY

Fourier transform (FT) Raman and surface enhanced Raman microspectrosc opy (SERS) were used as a vibrational probe for investigating, in vitr o and at the cellular level, the molecular interaction of dimethylcroc etin (DMCRT) with the retinoic acid nuclear receptor RAR-gamma, FT-SER S results obtained in vitro with silver colloids demonstrated that DMC RT interacts specifically with RAR-gamma. Comparison between the spect ra of DMCRT in HL60 cancer cells and the in vitro DMCRT-RAR gamma comp lex showed practically the same shift in wavenumber of the band at 121 0 cm(-1) and the same intensity ratios I-1541/l(1165) and I-1541/I-121 0. The similarity between the signal of DMCRT in K562 cells and in the free form is explained by either an absence of nuclear receptor or an absence of any interaction between the drug and receptor, These resul ts seem to indicate that carotenoids could possibly activate the nucle ar receptor in a similar manner to retinoids, (C) 1997 by John Wiley & Sons, Ltd.