Overexpression of ER and VDR is not sufficient to make ER-negative MDA-MB231 breast cancer cells responsive to 1alpha-hydroxyvitamin D5.

Abstract

1alpha-hydroxyvitamin D(5) [1alpha(OH)D(5)] is an active vitamin D analog showing promising chemopreventive effect in breast carcinogenesis. We previously reported that estrogen receptor (ER)-positive breast cancer cells were sensitive, whereas ER-negative breast cancer cells were relatively resistant to their antiproliferative effects. In the present study, we used ER-negative MDA-MB231, ER-transfected MDA-MB231 (S30) and ER-positive BT474 cell lines to evaluate the possible association between ER status and cellular sensitivity to 1alpha(OH)D(5) treatment. Our results demonstrate that ER expression in ER-negative breast cancer cells (S30) did not increase the sensitivity to 1alpha(OH)D(5), whereas in ER-positive BT474 cells, the significant antiproliferative effect of 1alpha(OH)D(5) was correlated with the downregulation of ER and progesterone receptor expression. Further analysis indicated that both MDA-MB231 and S30 cells express low vitamin D receptor (VDR) at transcriptional level and protein level. However, transfection of VDR failed to restore the sensitivity to 1alpha(OH)D(5) in MDA-MB231 and S30 cells, although VDR direct target gene CYP24 was more responsive to 1alpha(OH)D(5) treatment in MDA-MB231 and S30 cells overexpressing VDR. In addition, nuclear receptor cofactors NCoR1 and SRC1 that could potentially affect VDR action were also low in both MDA-MB231 and S30 cells in comparison with ER-positive, vitamin D-sensitive BT474 cells. These results suggest that in addition to the increased ER and VDR expression, the intact VDR signaling machinery as present in ER-positive, vitamin D-sensitive cells is essential for the antiproliferative action of vitamin D, whereas the direct VDR target genes such as CYP24 can remain responsive to augmented VDR expression.

• Authors: Xinjian Peng, Pavan Jhaveri, Erum A Hussain-Hakimjee, Rajendra G Mehta
• Journal: Carcinogenesis (Carcinogenesis) Vol. 28 Issue 5 Pg. 1000-7 (May 2007) ISSN: 0143-3334 [Print] England
• PMID: 17130524 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• 1-hydroxyvitamin D5
• Hydroxycholecalciferols
• Receptors, Calcitriol
• Receptors, Estrogen
• Receptors, Progesterone

Topics

• Breast Neoplasms (genetics, metabolism)
• Cell Cycle
• Cell Proliferation
• Drug Resistance, Neoplasm
• Gene Expression
• Humans
• Hydroxycholecalciferols (pharmacology)
• Receptors, Calcitriol (genetics)
• Receptors, Estrogen (genetics)
• Receptors, Progesterone (genetics)
• Transfection
• Tumor Cells, Cultured