INDUCTION OF APOPTOSIS BY RETINOIDS IN HUMAN CERVICAL-CARCINOMA CELL-LINES

Retinoids can inhibit the growth and modulate the differentiation of a variety of tumor cell types in vitro and in vivo. All-trans retinoic acid (ATRA) and N-(4-hydroxyphenyl)retinamide (4HPR) are currently being evaluated in clinical trials for their potential use in cancer chemoprevention and therapy. We compared the effects of these retinoids on 10 human cervical carcinoma cell lines. Four of the 10 cell lines showed dramatic morphological changes and the other 5 exhibited decreased cell density after treatment with 10 mu M 4HPR, whereas few changes were induced by 10 mu M ATRA. Cell rounding and detachment were also observed in four of the cell lines. An analysis of DNA from both detached and attached cells after retinoid treatment has demonstrated the formation of a DNA ladder after electrophoresis in agarose gels, which indicated that some of the cell lines had undergone apoptosis. Induction of DNA fragmentation by 4HPR but not by other retinoids (ATRA, 13-cis-RA, and 9-cis-RA) was further evidenced as early as 24 h after treatment by a quantitative assay based on the degradation of [H-3]-thymidine-labeled DNA. Ln addition, morphological changes of nuclei associated with apoptosis such as chromatin condensation were observed by propidium iodide staining of the nuclei after 4HPR treatment. These results demonstrate that 4HPR causes apoptosis in several cervical carcinoma cell lines and that it is more potent in this effect than ATRA or other RA isomers.