Stemming from our previous finding that HLA-II expression in breast carcinoma tissues correlates with increased IFN-γ mRNA, reduced age at diagnosis and reduced ER levels [12] we questioned whether E2, in the absence or presence of its cognate receptor ERα, modulates HLA-DR expression in established ER− and ER+ BCCL, treated or not with IFN-γ for 96 hours. Here, ESR1 is linked to breast carcinoma.