Potentiation of the antitumor effect of tamoxifen by combination with the antiprogestin onapristone.

The present study was undertaken to investigate the antitumor effect of a combination of the antiestrogen tamoxifen (TAM) and either the antiprogestin onapristone (ON) or the progestogen megestrol acetate (MEG) in experimental mammary tumor models. Rats bearing DMBA- or NMU-induced mammary tumors were treated with ON or MEG either alone or in combination with TAM for four weeks. In the DMBA-tumor model, treatment with ON or TAM alone caused tumor remissions, whereas the combination of ON and TAM was almost as effective as ovariectomy (100% remission) and led to a remission of 86-100%. The combination of TAM and ON was distinctly more effective than that of TAM and MEG. A similar potentiation of the antitumor effect of TAM and ON was observed in the NMU-tumor model. In DMBA-tumors, the concentration of progesterone receptors was found to increase after treatment for three days with TAM and ON. In hosts bearing DMBA-tumors, treatment with the combination of TAM and ON caused a reduction in ovarian and uterine weights. In the same animals, the basal level of progesterone was decreased in spite of a slight increase in the LH level. These findings suggest that the high antitumor effect of the combination of TAM and ON compared to the corresponding monotherapies can be related not only to the interaction of antihormones and receptors, but also to the up-regulation of PR and to a decrease in progesterone production. These data clearly suggest the sense of a combination of TAM with an antiprogestin in breast cancer treatment.

Antiovulatory effect of a single injection of pure antiestrogen ZK 191703 at early stage of rat estrus cycle.

The effects of ZK 191703 (ZK), a pure antiestrogen, on ovulation, follicle development and peripheral hormone levels were investigated in rats with 4-day estrus cycle and gonadotropin-primed immature rats in comparison to tamoxifen (TAM)-treatment. In adult rats, a single s.c. injection of ZK (5 mg/kg) or TAM (5 mg/kg) at an early stage of the estrus cycle (diestrus 9:00) inhibited ovulation, and was associated with suppression of the surge of preovulatory LH, FSH and progesterone. In rats treated with ZK or TAM at a late stage of the estrus cycle (proestrus 9:00), no inhibitory effects on ovulation, the gonadotropin and progesterone surge were detected. ZK treatment at diestrus 9:00, in contrast to TAM, increased the baseline LH level. When immature rats were treated with antiestrogens in the earlier stage of follicular development, 6 and 30 h but not 48 h or later after injection of gonadotropin (PMSG), ovulation was attenuated, associated with a lowered progesterone level. Unruptured preovulatory follicles were found in most of the ovaries from anovulatory animals treated with ZK or TAM. Antiestrogens, ZK and TAM administered at an early phase of the estrus cycle delay the follicular development functionally and inhibit ovulation in rats and suppression of the preovulatory progesterone surge.

[(2-Phenylindol-3-yl)methylene]propanedinitriles inhibit the growth of breast cancer cells by cell cycle arrest in G(2)/M phase and apoptosis.

Cell cycle arrest of malignant cells is an important option for cancer treatment. In this study, we modified the structure of antimitotic 2-phenylindole-3-carbaldehydes by condensation with malononitrile. The resulting methylene propanedinitriles inhibited the growth of MDA-MB 231 and MCF-7 breast cancer cells with IC(50) values below 100 nM. Though they exhibited similar structure-activity relationships as the aldehydes, they did not inhibit tubulin polymerization but were capable of blocking the cell cycle in G(2)/M phase. The cell cycle arrest was accompanied by apoptosis as demonstrated by the activation of caspases 3 and 9. Since the new 2-phenylindole derivatives also inhibited the growth of transplanted MXT mouse mammary tumors, they are interesting candidates for further development.

Antimitotic activities of 2-phenylindole-3-carbaldehydes in human breast cancer cells.

Small molecules such as indoles are attractive as inhibitors of tubulin polymerization. Thus a number of 2-phenylindole-3-carbaldehydes with lipophilic substituents in both aromatic rings was synthesized and evaluated for antitumor activity in MDA-MB 231 and MCF-7 breast cancer cells. Some 5-alkylindole derivatives with a 4-methoxy group in the 2-phenyl ring strongly inhibit the growth of breast cancer cells with IC(50) values of 5-20nM. Their action can be rationalized by the cell cycle arrest in G(2)/M phase due to the inhibition of tubulin polymerization.

The xenoestrogen bisphenol A in the Hershberger assay: androgen receptor regulation and morphometrical reactions indicate no major effects.

We evaluated androgen-like effects of bisphenol A (BPA) using orchiectomized Wistar rats. Animals were treated p.o. either with vehicle or with 3, 50, 200, 500 mg/kgbw/day BPA (n=13) for 7 days. One group was treated s.c. with 1mg/kgbw/day testosterone propionate (TP). Flutamide (FL) (3mg/kgbw/day, p.o.) was used to antagonize androgen effects of the suprapharmacological dose (500 mg/kgbw/day) of BPA. Androgen-like effects of BPA on prostates and seminal vesicles were assessed by the Hershberger assay, densitometric analysis of androgen receptor (AR) immunoreactivity, cell proliferation-index and a morphometric analysis. Absolute weights of prostates and seminal vesicles were not increased by BPA, whereas the relative weights were increased at higher doses of BPA, most likely due to a decrease in body weight. Staining intensity for AR immunoreactivity was increased at low but not at higher doses of BPA in comparison to the orchiectomized rats. BPA at all doses tested did not cause an increase of the cell proliferation-index. Epithelial height and glandular luminal area were increased by low doses of BPA, whereas higher doses caused a decrease of these parameters. The data provide evidence that BPA does not exert major androgenic effects.

Androgen-dependent morphology of prostates and seminal vesicles in the Hershberger assay: evaluation of immunohistochemical and morphometric parameters.

The aim of this study was to evaluate androgen-like effects using immunohistochemical and morphometric methods. Therefore, orchiectomized Wistar rats (n > or = 13) were treated s.c. with 1 mg/kg bw/day testosterone propionate (TP) for 7 days and compared to orchiectomized rats without TP substitution (OX) and to an untreated intact control group. Sections obtained from prostates and seminal vesicles were stained with polyclonal and monoclonal antibodies against the androgen receptor (AR) and assessed densitometrically (intensity of the immunoreaction) and morphometrically (epithelial height, luminal area). TP caused an enhancement of staining intensity and an increase in organ weights, epithelial height and luminal area. The use of proliferation markers (PCNA, MIB-5) showed also a highly significant increase of immunoreactive cells in TP-substituted orchiectomized rats compared with the OX group. Based on the present data, the densitometric analysis of AR-immunoreactivity as well as the assessment of proliferation markers, epithelial height and luminal area proved to be sensitive parameters for the evaluation of androgen effects on prostates and seminal vesicles. In further studies these parameters will be used to test several industrial xenooestrogens as well as phytooestrogens on their possible androgenic capacity.