Clayton Helen, Titley Ian, Vivanco Maria dM
The Breakthrough Toby Robins Breast Cancer Research Centre, UK.
Exp Cell Res. 2004 Jul 15;297(2):444-60. doi: 10.1016/j.yexcr.2004.03.029.
Estrogen is necessary for the full development of the mammary gland and it is also involved in breast cancer development. We set out to identify and characterise progenitor/stem cells in the human mammary gland and to explore the role of estrogen in their proliferation and differentiation. Three candidate stem cell populations were isolated: double positive (DP) cells co-expressed the luminal and myoepithelial markers, EMA and CALLA, respectively, whereas double negative (DN) cells did not express these cell surface markers; side population (SP) cells were characterised by their differential ability to efflux the dye Hoechst 33342. The ABC transporter, breast cancer resistance protein (BCRP) was more highly expressed in SP cells than in non-SP cells and a specific BCRP inhibitor, Ko143, reduced SP formation, suggesting that BCRP confers the SP phenotype in mammary epithelial cells, as has been demonstrated in other tissues. Interestingly, SP cells were double negative for the EMA and CALLA antigens and therefore represent a separate and distinct population to DP cells. Single cell multiplex RT-PCR indicated that the SP and DN cells do not express detectable levels of ERalpha or ERbeta, suggesting that estrogen is not involved in their proliferation. DP cells expressed ERalpha but at a lower level than differentiated luminal cells. These findings invoke a potential strategy for the breast stem/progenitor cells to ignore the mitogenic effects of estrogen. All three cell populations generated mixed colonies containing both luminal and myoepithelial cells from a single cell and therefore represent candidate multipotent stem cells. However, DN cells predominately generated luminal colonies and exhibited a much higher cloning efficiency than differentiated luminal cells. Further characterisation of these candidate progenitor/stem cells should contribute to a better understanding of normal mammary gland development and breast tumorigenesis.
雌激素对于乳腺的充分发育是必需的，并且它也参与乳腺癌的发展。我们着手鉴定和表征人乳腺中的祖细胞/干细胞，并探讨雌激素在其增殖和分化中的作用。分离出了三个候选干细胞群体：双阳性（DP）细胞分别共表达管腔和肌上皮标志物EMA和CALLA，而双阴性（DN）细胞不表达这些细胞表面标志物；侧群（SP）细胞的特征在于其排出染料Hoechst 33342的差异能力。ABC转运蛋白乳腺癌耐药蛋白（BCRP）在SP细胞中的表达高于非SP细胞，并且一种特异性BCRP抑制剂Ko143减少了SP的形成，这表明BCRP赋予乳腺上皮细胞SP表型，正如在其他组织中所证明的那样。有趣的是，SP细胞对于EMA和CALLA抗原呈双阴性，因此代表了一个与DP细胞不同的独立群体。单细胞多重RT-PCR表明SP和DN细胞不表达可检测水平的ERα或ERβ，这表明雌激素不参与它们的增殖。DP细胞表达ERα，但水平低于分化的管腔细胞。这些发现为乳腺干细胞/祖细胞忽略雌激素的促有丝分裂作用提出了一种潜在策略。所有这三个细胞群体都能从单个细胞产生包含管腔和肌上皮细胞的混合集落，因此代表候选多能干细胞。然而，DN细胞主要产生管腔集落，并且表现出比分化的管腔细胞高得多的克隆效率。对这些候选祖细胞/干细胞的进一步表征应有助于更好地理解正常乳腺发育和乳腺肿瘤发生。
