Cell experiment:

Briefly, cells (1×107/mL) are loaded with 1 μM FURA-2 at 37℃ in the dark for 30 minutes, washed twice, resuspended in phosphate-buffered saline (PBS) containing 1.26 mM CaCl2 at 106 cells/mL and then used for the experiments. Dual excitation, alternating at 340 nm and 380 nm, is provided by a spectrophotofluorometer equipped with 2 excitation monochromators, and emission is fixed at 480 nm. The temperature is set at 37℃±1℃. In some experiments, to eliminate extracellular calcium, cells preloaded with FURA-2 are resuspended in PBS without Ca2+, and 0.5 mM EGTA (ethylene glycol tetraacetic acid) is added to each sample prior to addition of the appropriate stimulus.

Animal experiment:

NB4 cells (3×106) are intraperitoneally inoculated in SCID mice (8 mice/group). ST1926 is dissolved in cremophor/ethanol 1:1 solution, and diluted 1:10 in PBS at the concentration of 50 mg/kg; the doses of 30 mg/kg and 40 mg/kg are then prepared by appropriate dilutions in the same vehicle. ATRA is dissolved in the dark in Cremophor EL and kept magnetically stirred; the solution is then diluted 1:10 in PBS at the final concentration of 40 mg/kg. Both compounds are administered intraperitoneally and orally twice per day for 3 weeks starting from the day after cell inoculation, in a volume of 10 mL/kg. During treatments body weight and lethality are registered.

Retinoid-related molecules are derivatives of retinoic acid and promising antileukemic agents with a mechanism of action different from that of other common chemotherapeutics. Adarotene is a novel atypical retinoid endowed with proapoptotic and antitumor activity.
In vitro: The novel atypical retinoid adarotene exhibited potent antiproliferative activity on a large panel of human tumor cells. It was found that although almost complete loss of ability to activate RARs, adarotene was performing as an effective apoptosis inducer and surprisingly produced DNA damage, which likely contributed to its proapoptotic activity [1].
In vivo: Following oral administration, adarotene was well tolerated and caused tumor growth inhibition in the ovarian carcinoma (A2780/DX) and the human melanoma (MeWo) exnographt in nude mice, supporting the therapeutic interest of this novel agent [1].
Clinical trial: Adarotene is currently only in the preclinical developlent stage and no clinical data are available.
Reference:
[1] Cincinelli R, Dallavalle S, Merlini L, Penco S, Pisano C, Carminati P, Giannini G, Vesci L, Gaetano C, Illy B, Zuco V, Supino R, Zunino F. A novel atypical retinoid endowed with proapoptotic and antitumor activity. J Med Chem. 2003;46(6):909-12.