Fig. 3

Elacestrant inhibits the growth of CDK4/6i-resistant breast cancer cell lines in vitro. a CellTiter-Glo assay of ER+ (wild-type and mutant) CDK4/6i-sensitive and CDK4/6i-resistant breast cancer cells treated with elacestrant at the indicated doses for 7 days. Relative EC₅₀ values were calculated by using a log(inhibitor) vs response curve fit. b Colony formation assay of ER+ (wild-type and mutant) CDK4/6i-sensitive and CDK4/6i-resistant breast cancer cells treated with elacestrant at the indicated dose for 3–5 weeks. c Western blot analysis of ER and downstream ER target genes (GREB1/PR) in the CDK4/6i-sensitive and CDK4/6i-resistant ESR1 wild-type and ESR1 mutant cell lines. CDK4/6i-sensitive, Palbo^R, Ribo^R, and Abema^R cells were treated with either control or elacestrant (300 nM). d qRT-PCR of PGR, TFF1, and GREB1 in palbociclib-sensitive and palbociclib-resistant cells treated with elacestrant at the specified doses