Abstract: Objective To investigate the effects of three generations of tretinoids on the apoptosis of and caspase expressions in human cutaneous squamous cell carcinoma cell line SCL-1. Methods SCL-1 cells were cultured in vitro in the presence of three tretinoins, namely all-trans retinoic acid （ATRA）, acitretin and tazarotene at a concentration of 1 × 10-5 mol/L. On day 1, 3, 5, MTT assay and ELISA were used to detect the cell proliferation and apoptosis of these SCL-1 cells respectively; on day 3, flow cytometry with Annexin V/PI was applied to analyze the cell cycle and early apoptosis, Western blot to measure the protein expressions of caspase-8 and caspase-9 in these cells. Results The growth of SCL-1 cells could be inhibited by ATRA, acitretin or tazarotene of 1 × 10-5 mol/L in a time-dependent manner （all P < 0.01）. All the three tretinoids could induce the cell apoptosis of SCL-1 cells （P < 0.01）, arrest them in G1-phase, and activate caspase-8 and caspase-9 （F = 35.50, 25.79, respectively, both P < 0.01）. Of the three tretinoins, acitretin exerted the strongest effect on all the parameters tested. Conclusions Tretinoins can inhibit the growth and induce the apoptosis of cutaneous squamous carcinoma cells, which may be mediated through Fas- and mitochondria-way.

Key words: retinoids, apoptosis, carcinoma, squamous cell