Figure 4. Ivermectin or selamectin treatment increases ESR1 and PGR expression leading to restoration of tamoxifen and estrogen sensitivity in TNBC cells.

A, qPCR of ESR1 in MDA-MB-231 cells (SEL, P < 0.0001; IVM, P < 0.0001) and D3H2LN (SEL, P < 0.0001; IVM, P < 0.0001) following treatment with selamectin or ivermectin (5 days) as indicated.

B, MDA-MB-231 cells were treated with selamectin (5 days) and subjected to immunoblot analysis to determine expression of ERα protein. Expression of ERα in T47D breast cancer cells is shown as a positive control.

C, qPCR of PGR in MDA-MB-231 cells (SEL, P < 0.0001; IVM, P < 0.0001) and D3H2LN (SEL, P < 0.0001; IVM, P = 0.0021) following treatment with selamectin or ivermectin (5 days) as indicated.

D, MDA-MB-231 cells were pre-treated with selamectin (1µM) for 4 days. Cells were transfected with a luciferase reporter under the control of an estrogen response element, and further treated with selamectin or selamectin plus tamoxifen (Tam) in the presence of 17β-estradiol (E2) for 48 hours (E2 vs. Tam, P = 0.0056). Luciferase activity relative to renilla control (red) is shown.

E, MDA-MB-231 or D3H2LN cells were pre-treated with selamectin (1µM) for 4 days and then further treated with selamectin or selamectin plus Tam in the presence of E2 for 48 hours. Cell viability was determined by MTS tetrazolium assay (E2 vs. Tam: MDA-MB-231, P < 0.0001; D3H2LN, P < 0.0001).

Error bars represent mean ± SD. P, unpaired t-test.