Opposite effects of antimicrotubule agents on c-myc oncogene expression depending on the cell lines used

We investigated the expression of c-myc in HT29-D4, HBL100 and Caco-2 cells treated with microtubule stabilising (paclitaxel) or depolymerising agents (Vinblastine, nocodazole). After induction by epidermal growth factor (EGF ), c-myc expression decreased in HT29-D4 cells treated with all the antimic rotubule agents. In HBL100 and Caco-2, when microtubules were stabilised wi th paclitaxel, c-myc expression also decreased. In contrast, its expression increased after treatment with depolymerising agents. In both cell lines, we also observed that depolymerising agents alone induced c-myc expression whilst paclitaxel had no effect. This mRNA induction was confirmed at the p rotein level. In HT29-D4, no Variation of c-myc expression was observed. Th en, we showed that the increase of mRNA level was due to activation of gene transcription. These results indicate that modulation of c-myc expression varied depending on the cell lines used and the type of antimicrotubule age nts. This work provides a potential link between the microtubular network a nd c-myc gene expression. (C) 2000 Elsevier Science Ltd. All rights reserve d.