Effects of (+)-, (-)- and (+/-)-indenestrols A and B on microtubule distribution and cytotoxicity in Chinese hamster V79 cells.

We have reported that (+)-, (-)- and (+/-)-indenestrols A and B (IA and IB respectively) inhibit the polymerization of microtubule proteins isolated from porcine brain in vitro. In this study, the effects of (+)-, (-)- and (+/-)-IA and IB on the relative plating efficiency, chromosome number and cellular microtubular architecture of Chinese hamster V79 cells, detected with a fluorescent anti-tubulin antibody, were investigated. The results indicated that the effect of (+/-)-IA was similar to that of diethylstilbestrol and that of (+/-)-IB was greater than that of (+/-)-IA. We also determined the effects of the optically active IA and IB isomers and found that the rank order of cytotoxic activity of the IA and IB series was: (-)-IA > (+/-)-IA > (+)-IA and (+/-)-IB > or = (-)-IB > (+)-IB. Furthermore, we studied the intracellular disturbance of microtubule formation induced by these compounds and found that (-)-IA had by far the greatest disruptive effect.

Effects of diethylstilbestrol and its methyl ethers on aneuploidy induction and microtubule distribution in Chinese hamster V79 cells.

We previously reported that diethylstibestrol (DES) and its derivatives inhibit the in vitro polymerization of microtubule proteins isolated from porcine brain (Sato et al., 1987). We found that the presence of the free hydroxy group of DES was indispensable for the inhibition of microtubule assembly. In the present investigation, this structure-activity relationship was confirmed by the effects of DES and its methyl ethers on chromosome number and the cellular microtubule architecture of Chinese hamster V79 cells, revealed by fluorescent anti-tubulin antibody. DES induced tetra- and octa-ploidy and DES monomethyl ether induced only tetraploidy at a much slower rate, whereas DES dimethyl ether was found to be completely inactive. Furthermore, DES was more active than its monomethyl ether in disturbing microtubule formation within cells. These results support the initial assumption that polyploidy is largely a consequence of the disturbed assembly of microtubules.

Microtubule disruption induced by estradiol in estrogen receptor-positive and -negative human breast cancer cell lines.

Effects of estrogens on the cytoplasmic microtubule network were examined by the indirect immunofluorescence method using anti-beta-tubulin antibody. Estradiol, a naturally occurring estrogen, decreased the amount of cytoplasmic microtubule fibers during interphase in the human breast cancer cell lines MCF-7 and MDA-MB-231. Since MDA-MB-231 is an estrogen receptor-negative cell line, estradiol-induced microtubule disruption seems to be independent of estradiol binding to receptors. The effective concentration of estradiol required for induction of microtubule disruption in 50% of the cells (EC50) was 81 microM for MCF-7 cells and 82 microM for MDA-MB-231 cells. A synthetic estrogen, diethylstilbestrol, also induced a decrease in microtubule fibers, with an EC50 value of 48 microM for MCF-7 cells and 50 microM for MDA-MB-231 cells. When estrogen-treated and microtubule-depolymerized cells were washed and the medium was replaced with fresh, intracellular microtubule networks reappeared within 3 h. When MCF-7 cells were cultured for 4 days with estradiol (50 microM), cell growth was completely inhibited. However, estrone affected the microtubule network and cell proliferation only slightly. These results suggest that estradiol-induced microtubule disruption is closely related to its inhibitory effect on cell growth.

Effect of estradiol and ethynylestradiol on microtubule distribution in Chinese hamster V79 cells.

The effects of estradiol (E2) and ethynylestradiol (EE2) on the chromosome number and cellular microtubule architecture of Chinese hamster V79 cells were studied using fluorescent anti-tubulin antibody. Treatment with 20 microM E2 for 48 h induced only a small amount of tetraploid cells, but the normal microtubule network was disrupted completely by only 3 h of treatment. This data reveals that E2 has higher microtubule-disruptive activity than diethylstilbestrol in V79 cells.