A combination of LUT and I3C suppresses E2-induced breast cancercell growth and promotes ERα degradation. (A,B) LUT (30 μM) not I3C (40 μM) inhibited E2-induced MCF7 cell growth at 72 h. (C) Effect of the combination L30I40 on MCF7 cells ERE activity in both E2 containing (+E2) and E2 depletion (-E2) medium. (D) Erα,SIRT1, and Rbprotein levels were synergistically reduced by combination L30I40 after 48h in MCF7and T47Dcells. (E) Immunofluorescence of ERα in MCF7 in response to LUT30, I3C40, and the combination of L30I40, respectively. (F) Short time (120 min) treatment of combination L30I40 synergistically degrades ERα and SIRT1 protein in MCF7 cells with or without E2(1nM). (G) Proteasome inhibitor MG132 partially restored L30I40-reduced ERα and SIRT1 protein levels in MCF7 cells. MG132 10 μM was used to pre-treat MCF7 cells for 30 min ahead treatment using selective estrogen receptor degrader agent. * p < 0.05; ** p < 0.01.