Fig 1: PRR11 overexpression confers resistance to antiestrogens.a Lysates of MDA-MB-134VI and MDA-MB-175VII cells that had been transduced with pLX304-PRR11, -BRIP1, -TACO1, and -SMARCD2 were subjected to immunoblot analysis. b Low density monolayers of MDA-MB-134VI and MDA-MB-175VII pLX304-PRR11, -BRIP1, -TACO1, and -SMARCD2 cells were grown in estrogen-deprived condition. After 2 weeks, cell monolayers were stained with crystal violet and cell viability quantified as described in Methods. Data represent the mean ± SD of three replicates (two-tailed unpaired t-tests). c MCF7 LTED and HCC1428 LTED cells were transfected with PRR11 siRNAs. Low density monolayers of cells were treated ± 1 nM estrogen (E2) for 10 days. Cell monolayers were stained with crystal violet. Data represent the mean ± SD of three replicates (two-tailed unpaired t-tests). d, e MCF7 LTED and HCC1428 LTED cells were transduced with shRNA targeting the 3' UTR of PRR11 and then, re-transduced with pLX304-GFP or pLX304-PRR11. Cell lysates were subjected to immunoblot analysis (d). Upper and lower arrows indicate exogenous and endogenous PRR11, respectively. Low density monolayers of cells shown in d were grown in absence of E2 for 10 days (e). Data represent the mean ± SD of three replicates (two-tailed unpaired t-tests). f MCF7 cells stably expressing doxycycline-inducible-PRR11 shRNA and control shRNA were injected s.c. in the dorsum of athymic ovariectomized mice supplemented with a 14-day release 17ß-estradiol pellet. After 4 weeks, mice were randomized to treatment with 10 mg/kg doxycycline (i.p) for 4 weeks. Each data point represents the mean tumor volume in mm3 ± SD; n of mice per group are shown in parenthesis (two-tailed unpaired t-tests). g Fulvestrant sensitivity of ER+ breast cancer cell lines (n = 11, PRISM Repurposing 19Q3 dataset). Y-axis, drug sensitivity, represents relative barcode abundance following fulvestrant treatment (Pearson correlation). h, i Fulvestrant GR50 were calculated using the GR metrics calculator56 (http://www.grcalculator.org/grcalculator/). Cell numbers on days 0 and 6 were used as the input data. MDA-MB-134VI and MDA-MB-175VII cells were stably transduced with pLX302-LacZ (control) or pLX302-PRR11 (h). MCF7 FulvR cells were transfected with control or PRR11 siRNA (i). Data represent the mean ± SD of three replicates (two-tailed unpaired t-tests). Source data are provided as a Source data file.