AP-2β is a new mammary epithelial differentiation marker and its expression is preferentially retained and enhanced in lobular carcinoma in situ and invasive lobular breast cancer. In normal breast epithelium AP-2β is expressed in a scattered subpopulation of luminal cells. So far, these cells have not been further characterized. Co-expression of AP-2β protein and luminal epithelium markers (GATA3, CK8/18), hormone receptors [estrogen receptor (ER), androgen receptor (AR)] and candidate stem cells markers (CK5/14, CD44) were assessed by double-immunofluorescence staining in normal mammary gland epithelium. The subpopulation of AP-2β-positive mammary epithelial cells showed an almost complete, superimposable co-expression with GATA3 and a peculiar intense, ring-like appearing immunoreactivity for CK8/18. Confocal immunofluorescence microscopy revealed an apicobasal staining for CK8/18 in AP-2β-positive cells, which was not seen in in AP-2β-negative cells. Furthermore, AP-2β-positive displayed a partial co-expression with ER and AR, but lacked expression of candidate stem cell markers CK5/14 and CD44. In summary, AP-2β is a new luminal mammary epithelial differentiation marker, which is expressed in the GATA3-positive subpopulation of luminal epithelial cells. These AP-2β-positive/GATA3-positive cells also show a peculiar CK8/18-expression which may indicate a previously unknown functionally specialized mammary epithelial cell population.

AP-2β是一种新的乳腺上皮分化标志物，其表达在小叶原位癌和浸润性小叶乳腺癌中优先保留和增强。在正常乳腺上皮细胞中，AP-2β 在散在的管腔细胞亚群中表达。到目前为止，这些细胞还没有被进一步表征。AP-2β蛋白和管腔上皮标志物（GATA3、CK8/18）、激素受体[雌激素受体（ER）、雄激素受体（AR）]和候选干细胞标志物（CK5/14、CD44）的共表达通过以下方法评估正常乳腺上皮的双重免疫荧光染色。AP-2β 阳性乳腺上皮细胞亚群显示出与 GATA3 几乎完全的、可叠加的共表达和对 CK8/18 的特殊强烈、环状出现的免疫反应性。共聚焦免疫荧光显微镜显示 AP-2β 阳性细胞中 CK8/18 的顶端基底染色，这在 AP-2β 阴性细胞中未见。此外，AP-2β 阳性与 ER 和 AR 部分共表达，但缺乏候选干细胞标志物 CK5/14 和 CD44 的表达。综上所述，AP-2β是一种新的管腔乳腺上皮分化标志物，在管腔上皮细胞的GATA3阳性亚群中表达。这些 AP-2β 阳性/GATA3 阳性细胞也显示出特殊的 CK8/18 表达，这可能表明以前未知的功能特化乳腺上皮细胞群。但缺乏候选干细胞标志物CK5/14和CD44的表达。综上所述，AP-2β是一种新的管腔乳腺上皮分化标志物，在管腔上皮细胞的GATA3阳性亚群中表达。这些 AP-2β 阳性/GATA3 阳性细胞也显示出特殊的 CK8/18 表达，这可能表明以前未知的功能特化乳腺上皮细胞群。但缺乏候选干细胞标志物CK5/14和CD44的表达。综上所述，AP-2β是一种新的管腔乳腺上皮分化标志物，在管腔上皮细胞的GATA3阳性亚群中表达。这些 AP-2β 阳性/GATA3 阳性细胞也显示出特殊的 CK8/18 表达，这可能表明以前未知的功能特化乳腺上皮细胞群。