Overexpression of ER and VDR is not sufficient to make ER-negative MDA-MB231 breast cancer cells responsive to 1alpha-hydroxyvitamin D5.
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.
Peng
Xinjian
X
IIT Research Institute, Chicago, IL 60616, USA.
Jhaveri
Pavan
P
Hussain-Hakimjee
Erum A
EA
Mehta
Rajendra G
RG
D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D002453:Cell Cycle; D049109:Cell Proliferation; D019008:Drug Resistance, Neoplasm; D015870:Gene Expression; D006801:Humans; D006887:Hydroxycholecalciferols / Q000494:pharmacology*; D018167:Receptors, Calcitriol / Q000235:genetics*; D011960:Receptors, Estrogen / Q000235:genetics*; D011980:Receptors, Progesterone / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured
C103958:1-hydroxyvitamin D5; D006887:Hydroxycholecalciferols; D018167:Receptors, Calcitriol; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone