Clinical parameters of the breast tumor samples. IDC invasive ductal carcinoma, ILC invasive lobular carcinoma. Figure S2. Expression of Flag-ERα36 in transiently transfected MDA-MB231 as detected by immunocytochemistry using an anti-Flag antibody. Figure S3. Analysis of potential correlation between the clinical parameters of the breast tumor samples and the expression of ERα46 isoform. A significant P value (indicated in red) was only found between ERα46 expression and HER-2 positive breast tumors. IDC invasive ductal carcinoma, ILC invasive Lobular Carcinoma. Figure S4. Results of the proteomic analysis of the ERα46 protein detected in tumor samples. A) Western blot with the SP1 antibody obtained after immunoprecipitation of ERα with HC20 antibody in two human tumors overexpressing the putative ERα46 isoform. B and C) Sequence coverage obtained from the peptides identified by proteomic analysis shown in bold red on ERα66 and on ERα46 isoforms M (methionine): putative translational start sites generating the ERα46 isoform. Figure S5. The stress-induced increase in LucF activity is reproducible in MCF7 cells (A) and is not due to the generation of mono-cistronic LucF transcripts via an internal promoter or cryptic splicing as observed in MDA-Lenti-AB exposed to two siRNAs-lucR (B and C). Figure S6. Modulation profiles of the interaction of ERα46 (red) and ERα66 (blue) with coregulators in A) Apo proteins and B) in response to E2 binding. C) Profile of EC50 values of 4-OH-tamoxifen- (red) and fulvestrant- (blue) induced modulation of ERα46 and ERα66 coregulators interaction when use in antagonists mode with 6.3 nM E2. Figure S7. List of primers used in the expression profiling of target genes. Figure S8. Fold-changes (FC) in gene expression± SEM in MDA-ERα46 and MDA-ERα66 cells in response to 4-h treatment with E2 (10–8 M). P values were determined by Mann-Whitney test. Significant P values are indicated in red. (PPTX 939 kb)