Retinoic acid induced death of ovarian carcinoma cells correlates with c-myc stimulation.

In the ovarian adenocarcinoma subline N.I, all-trans retinoic acid (ATRA) induced substantial cell death. This response was elicited only at decreased serum levels. Exposure of N.I cells to increasing concentrations of ATRA was accompanied by a considerable up-regulation of c-myc transcript levels that correlated with the rate of cell killing, which itself was an active process as judged by sustained transcriptional expression. ATRA-triggered rounding and detaching of single cells from the substratum was accompanied by degradation of genomic DNA. We show that the N.I model cell line, which is otherwise highly ATRA-resistant, can undergo an ATRA-triggered suicide program when serum is limited. The accompanying c-myc up-regulation seems to be mediated by retinoic-acid-receptor-independent pathways involving membrane-associated phospholipases instead, because manoalide partly suppressed c-myc induction by ATRA but left constitutive c-myc expression unaffected.