Inadequate validity and poor specificity of ERβ antibodies has been an issue in much of the literature on ERβ protein expression, highlighted by the finding that neither of the well-studied purported ERβ-positive cancer cell lines, MCF-7 (breast) and LNCaP (prostate), expressed any ERβ when using validated antibodies and independent mass spectrometry-based approaches43. Here, ESR2 is linked to cancer.