Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, 750 07, Uppsala, Sweden,
Cell Biol Toxicol. 2015 Apr;31(2):111-20. doi: 10.1007/s10565-015-9298-5. Epub 2015 Mar 20.
Breast cancer resistance protein (Bcrp/Abcg2) and multidrug transporter 1 (Mdr1/Abcb1) are efflux proteins located in the apical membrane of mammary epithelial cells (MEC). Bcrp is induced in MEC during gestation and lactation, while Mdr1 is down-regulated during lactation. Numerous drugs and toxic compounds are known to be actively secreted into milk by Bcrp, but most chemicals have not been investigated in this respect, emphasizing the need for functional Bcrp studies in an established cell line with secreting mammary epithelial cells. The present study was undertaken to examine expressions of Bcrp and Mdr1 in mammary epithelial HC11 cells, derived from a mid-gestational murine mammary gland. In addition, Bcrp function was assessed by transport experiments with mitoxantrone (MX) in undifferentiated HC11 cells, in HC11 cells subjected to Bcrp RNA interference (RNAi), as well as in HC11 cells stimulated to differentiate by treatment with lactogenic hormones. Differentiated HC11 cells organized into alveolar-resembling structures and gene expression of the major milk protein β-casein was induced, whereas undifferentiated cells formed monolayers with lower β-casein expression. Bcrp and Mdr1 gene and protein were expressed in both undifferentiated and differentiated HC11 cells. Differentiation of HC11 cells resulted in increased Bcrp protein expression, while Mdr1 gene and protein expressions were reduced. The Bcrp inhibitor elacridar (GF120918) reduced secretion and increased accumulation of MX in both undifferentiated and differentiated HC11 cells. Silencing of the Bcrp gene caused an increased accumulation of MX. The results indicate that the HC11 cell model provides a promising tool to investigate transport of potential Bcrp substrates in mammary epithelial cells.
乳腺癌耐药蛋白（Bcrp/Abcg2）和多药转运蛋白 1（Mdr1/Abcb1）是位于乳腺上皮细胞（MEC）顶膜的外排蛋白。Bcrp 在妊娠和哺乳期的 MEC 中被诱导，而 Mdr1 在哺乳期时被下调。许多药物和有毒化合物已知被 Bcrp 主动分泌到乳汁中，但大多数化学物质在这方面尚未被研究，这强调了在具有分泌乳腺上皮细胞的已建立细胞系中进行功能性 Bcrp 研究的必要性。本研究旨在检查乳腺上皮细胞 HC11 中 Bcrp 和 Mdr1 的表达，HC11 细胞来源于中期妊娠的鼠乳腺。此外，通过未分化的 HC11 细胞、经 Bcrp RNA 干扰（RNAi）处理的 HC11 细胞以及用生乳激素处理刺激分化的 HC11 细胞中的米托蒽醌（MX）转运实验评估了 Bcrp 的功能。分化的 HC11 细胞组织成类似肺泡的结构，并诱导主要乳蛋白β-酪蛋白的基因表达，而未分化的细胞形成单层，β-酪蛋白表达较低。Bcrp 和 Mdr1 基因和蛋白在未分化和分化的 HC11 细胞中均有表达。HC11 细胞的分化导致 Bcrp 蛋白表达增加，而 Mdr1 基因和蛋白表达减少。Bcrp 抑制剂埃拉西达（GF120918）减少了未分化和分化的 HC11 细胞中 MX 的分泌并增加了其积累。Bcrp 基因的沉默导致 MX 积累增加。结果表明，HC11 细胞模型为研究乳腺上皮细胞中潜在 Bcrp 底物的转运提供了一个有前途的工具。
