Photocytotoxicity of the fluorescent nonsteroidal androgen receptor ligand TDPQ.

1,2,3,4-tetrahydro-2,2-dimethyl-6-(trifluoromethyl)-8-pyridono[5,6-g]quinoline (TDPQ), a selective nonsteroidal androgen receptor (AR) ligand, is a fluorescent compound. We characterized its spectral properties in comparison with the structural precursor carbostyril 151 (C151) and with its racemic structural isomer 4-ethyl-1,2,3,4-tetrahydro-6-(trifluoromethyl)-8-pyridino[5,6-g]quinoline (ETPQ). The absorption maximum in CH3CN of either TDPQ or ETPQ is 400 nm whereas that of C151 is 350 nm. The fluorescence lifetimes (tau) and quantum yields (phif) in CH3CN are typical of fluorescent dyes: TDPQ (4.2 ns, 0.8) and ETPQ (4.6 ns, 0.76). C151 showed lower tau and phif of 0.2 ns and 0.02, respectively. TDPQ can function as a fluorescent label at (sub)micromolar concentrations. We detected TDPQ fluorescence in human breast tumor cells using confocal microscopy. While the fluorescence maxima of the compounds were solvent insensitive, the phif for ETPQ decreased in aqueous solutions regardless of the presence of albumin or DNA. The phif of TDPQ was less affected. The quantum yield of singlet oxygen (1O2) photosensitization (phiso) by TDPQ and ETPQ was about 7% in CH3CN, sufficient to induce photocytotoxicity. TDPQ was photocytotoxic in AR-positive MDA-MB-453 breast cancer cells but not in AR-negative MDA-MB-231 cells. The combination of AR selectivity with photocytotoxicity makes TDPQ a promising candidate for selective targeting of AR-positive cells during photodynamic therapy.

Androgen receptor-mediated apoptosis is regulated by photoactivatable androgen receptor ligands.

We have studied nonsteroidal ligands of the human androgen receptor (hAR) and have shown elsewhere that when photoactivated by visible light they collide with O2 to yield singlet oxygens (1O2) in vitro. Here we report cell killing after brief light activation (405 nm) of 1,2,3,4-tetrahydro-2,2-dimethyl-6-(trifluoromethyl)-8-pyridono[5,6-g]quinoline (TDPQ) in human prostate tumor cells. TDPQ/AR complexes were required for the death response because AR-positive LNCaP cells were killed, whereas AR-negative PC-3 cells were resistant. Excess dihydrotestosterone (DHT) blocked the TDPQ effect when the two were added together; irradiation of cells containing DHT alone had no effect. When LNCaP AR expression was suppressed using small interfering oligonucleotides targeting AR, photocytotoxicity was diminished. Conversely, stable transfection of hAR into PC-3 cells made the cells photosensitive to TDPQ. Similar results were obtained using a structural isomer of TDPQ, and also the synthetic steroidal AR ligand R1881. Cell death occurred via apoptosis as demonstrated by annexin V immunostaining, nuclear condensation, and caspase inhibition. Death involved oxidative stress, because it was prevented by addition of the antioxidant ascorbic acid during photoactivation. Detection of elevated levels of 8-hydroxy-2'-deoxyguanosine in nuclei of irradiated cells indicated oxidative DNA damage. Apoptosis spread into adjacent nonirradiated cells by direct cell-cell contacts, indicative of a bystander effect. Other photoactivatable ligands are described, implying a general method for ablation of cells bearing specific nuclear hormone receptors.

5-benzylidene-1,2-dihydrochromeno[3,4-f]quinolines as selective progesterone receptor modulators.

A series of 5-benylidene-1,2-dihydrochromeno[3,4-f]quinolines (4) were synthesized and tested in bioassays to evaluate their progestational activities, receptor- and tissue-selectivity profiles as selective progesterone receptor modulators (SPRMs). Most of the new analogues exhibited as highly potent progestins with more than 100-fold receptor selectivity over other steroid hormone receptors and LG120920 (7b) demonstrated tissue selectivity toward uterus and vagina versus breasts in a rodent model after oral administration.

Synthesis and biological activity of 5-methylidene 1,2-dihydrochromeno[3,4-f]quinoline derivatives as progesterone receptor modulators.

A series of 5-methylidene 1,2-dihydrochromeno[3,4-f]quinoline derivatives were synthesized and tested in biological assays to evaluate scope and limitations of the nonsteroidal SPRM pharmacophore (3). A number of orally available highly potent nonsteroidal modulators were identified by modification of the substituents at 5-methylidene position.