Antiestrogenic effects of all-trans-retinoic acid and 1,25-dihydroxyvitamin D3 in breast cancer cells occur at the estrogen response element level but through different molecular mechanisms

Abstract

Most breast tumors show estrogen-dependent growth and are thus susceptible to antiestrogenic therapy. MCF-7 cells, obtained from a human estrogen-dependent breast carcinoma, are widely used for studying the modulation of estrogenic responses by different effectors.

All-trans-retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (Vit D3) inhibited estrogen-induced growth of MCF-7 cells and their effect was potentiated by the classical antiestrogen, hydroxytamoxifen.

In MCF-7 cells, we found that RA and Vit D3 also inhibited estrogen-induced transcription; this was shown both for an endogenous gene (pS2) and for various exogenous transfected genes. Their inhibitory effect could not be reversed by increasing estradiol concentrations, showing that contrary to classical antiestrogens, they did not compete with estradiol to bind the estrogen receptor (ER).

Analysis of the inhibitory mechanisms indicates that RA and Vit D3 receptors can directly or indirectly impair the binding of ER to the estrogen responsive element.

The antagonist effect of RA would be found especially at DNA level since it seems to essentially involve an estrogen responsive element. The antagonist effect of Vit D3 would be found especially at the ER level since it seems to concern estrogen binding and dimerization domains of ER.

We conclude that the antiestrogenic effects of RA and Vit D3 are similar since they can, via their receptors, interfere with estrogenic action at the estrogen responsive element level but that they are not identical since different molecular mechanisms are involved.

About this publication.

See also:

- Official Web Site: The Di Bella Method;

- All-Trans-Retinoic Acid (ATRA - analogues and/or derivatives) - In vitro, review and in vivo publications;

- The Di Bella Method (A Fixed Part - All-Trans Retinoic Acid, Analogues and/or Derivatives - Approximately 60mg per day orally: 40mg per day Beta-Carotene/β-Carotene, 10mg per day ATRA and 10mg per day Axerophthol palmitate);

- Solution of retinoids in vitamin E in the Di Bella Method biological multitherapy;

- Vitamin D (analogues and/or derivatives) and cancer - In vitro, review and in vivo publications;

- The Di Bella Method (A Fixed Part - Dihydrotachysterol, Alfacalcidol, synthetic Vitamin D3);

- Evaluation of the safety and efficacy of the first-line treatment with somatostatin combined with melatonisn, retinoids, vitamin D3, and low doses of cyclophosphamide in 20 cases of breast cancer: a preliminary report;

- The Di Bella Method (DBM) improved survival, objective response and performance status in a retrospective observational clinical study on 122 cases of breast cancer;

- Complete objective response to biological therapy of plurifocal breast carcinoma.