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  • 1
    Electronic Resource
    Electronic Resource
    The tumour-inhibiting potential of the progesterone antagonist Onapristone in the human mammary carcinoma T61 in nude mice (1992)
    Springer
    Journal of cancer research and clinical oncology 118 (1992), S. 187-189 
    Details
    ISSN: 1432-1335
    Keywords: Onapristone ; Progesterone antagonist ; T61 mammary carcinoma ; Progesterone receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The progesterone antagonist Onapristone proved to possess strong tumour-inhibiting activity in a panel of experimental mammary carcinomas. Its underlying mechanism of action is due to a progesterone-receptor-mediated induction of terminal differentiation and a specific blockade of the cell cycle and is also present in the absence of progesterone as was shown in the MXT mammary tumour. To prove this further, the tumour-inhibiting activity of Onapristone was investigated in the human postmenopausal T61 mammary tumour implanted in castrated male nude mice. Whereas Onapristone given alone had no effect on growth of established tumours, after stimulation of the relatively low progesterone receptor content of this tumour line with an oestrogen, Onapristone significantly inhibited tumour growth. Thus, we suggest that Onapristone exerts its antitumour action via progesterone receptors. As there is no endogenous progesterone in these mice, the tumour-inhibiting activity of Onapristone is not primarily due to a classical antihormonal effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410132
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The pure antiestrogen ICI 182780 is more effective in the induction of apoptosis and down regulation of BCL‐2 than tamoxifen in MCF‐7 cells (1999)
    Springer
    Breast cancer research and treatment 58 (1999), S. 87-97 
    Details
    ISSN: 1573-7217
    Keywords: antiestrogens ; apoptosis ; BCL‐2 ; breast cancer ; MCF‐7 ; tamoxifen ; ZM 182780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is increasing evidence that induction of apoptosis by antihormones is an important mechanism in regard to their growth inhibitory action on hormone dependent tumors. In this report we have compared the efficiency of tamoxifen (Tam) and the pure antiestrogen ICI 182780 (ZM) to induce apoptosis in the estrogen dependent breast cancer cell line MCF‐7. Clear evidence for induction of apoptosis could be demonstrated after treatment with both antiestrogens. Application of the pure antiestrogen ZM led to a significantly higher induction of apoptosis compared to the partial agonistic compound Tam. The ability of the two compounds to induce apoptosis correlated with their growth inhibitory action. On the molecular level administration of ZM led to a time dependent steady decrease of BCL‐2 mRNA and protein. Administration of Tam also initially decreased the expression of BCL‐2. In contrast to ZM treatment, BCL‐2 expression increased again after 8 h of incubation with Tam. After 96 h Tam treated cells expressed BCL‐2 levels nearly as high as untreated cells. In general, ZM decreased BCL‐2 levels more effectively than Tam. Our results demonstrate that ZM and Tam possess quantitative and qualitative differences in their ability to down regulate BCL‐2 expression. The higher ability of the pure antiestrogen to down regulate BCL‐2 expression may explain the superiority of the pure antiestrogen to induce apoptosis and to inhibit the growth of MCF‐7 cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006338123126
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    Paper (German National Licenses)
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