To up-regulate ERβ1 mRNA in breast cancer cells, and to explore the inhibiting effect of raloxifene (RAL) on MDA-MB-231 cell which has the high expression of ERβ1.

We used HIV lentivirus containing ERβ1 gene to infect breast cancer cell line of MDA-MB-231, and established cell-line stably over-expressing ERβ1 gene. Fluorescence microscopy was used to show the transfected cells of which the eGFP was positive. Then we identified the ERβ1 gene expression on the levels of mRNA and protein by RT-PCR and Western blotting. All cell subtypes were cultured with increasing concentration of RAL (0, 1, 10 μmol/L) for 48 h, the difference of therapeutic effects among the MDA-MB-231/ERβ1, MDA-MB-231/eGFP and MDA-MB-231 were detected.

Fluorescence microscopy showed that more than 90% of transfected cells by the HIV lentivirus were green fluorescence positive. RT-PCR test showed that the levels of ERβ1 mRNA in MDA-MB-231/ERβ1 cells were increased 12.9 times respectively compared with parental cells (P<0.05). Western blotting showed that ERβ1 protein levels were also increased correspondingly. Cell experiment showed that high dose (10 μmol/L) of RAL inhibited proliferation of all MDA-MB-231 sub-lines, and the greater extent was observed when ERβ1 over-expressed (F=9.273, P=0.015).

The sensitivity to RAL for breast cancer cell of MDA-MB-231 can be increased by up-regulating ERβ1 level.