Shiraishi Akira, Tachi Kana, Essid Nesrine, Tsuboi Ikki, Nagano Masumi, Kato Toshiki, Yamashita Toshiharu, Bando Hiroko, Hara Hisato, Ohneda Osamu
Department of Regenerative Medicine and Stem Cell Biology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Department of Breast-Thyroid-Endocrine Surgery, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Cancer Sci. 2017 Mar;108(3):362-372. doi: 10.1111/cas.13147. Epub 2017 Feb 23.
Stable breast cancer cell (BCC) lines are valuable tools for the identification of breast cancer stem cell (BCSC) phenotypes that develop in response to several stimuli as well as for studying the basic mechanisms associated with the initiation and maintenance of BCSCs. However, the characteristics of individual, BCC-derived BCSCs varies and these cells show distinct phenotypes depending on the different BCSC markers used for their isolation. Aldehyde dehydrogenase (ALDH) activity is just such a recognized biomarker of BCSCs with a CD44 /CD24 phenotype. We isolated BCSCs with high ALDH activity (CD44 /CD24 /Aldefluor ) from a primary culture of human breast cancer tissue and observed that the cells had stem cell properties compared to BCSCs with no ALDH activity (CD44 /CD24 /Aldefluor ). Moreover, we found Aldefluor BCSCs had a greater hypoxic response and subsequent induction of HIF-1α expression compared to the Aldefluor BCSCs. We also found that knocking down HIF-1α, but not HIF-2α, in Aldefluor BCSCs led to a significant reduction of the stem cell properties through a decrease in the mRNA levels of genes associated with the epithelial-mesenchymal transition. Indeed, HIF-1α overexpression in Aldefluor BCSCs led to Slug and Snail mRNA increase and the associated repression of E-cadherin and increase in Vimentin. Of note, prolonged hypoxic stimulation promoted the phenotypic changes of Aldefluor BCSCs including ALDH activity, tumorigenesis and metastasis, suggesting that hypoxia in the tumor environment may influence BCSC fate and breast cancer clinical outcomes.
稳定的乳腺癌细胞（BCC）系是用于鉴定乳腺癌干细胞（BCSC）表型的宝贵工具，这些表型会因多种刺激而产生，同时也有助于研究与BCSC启动和维持相关的基本机制。然而，源自单个BCC的BCSC的特征各不相同，并且这些细胞根据用于分离它们的不同BCSC标记物而表现出不同的表型。醛脱氢酶（ALDH）活性就是这样一种公认的具有CD44 / CD24表型的BCSC生物标志物。我们从人乳腺癌组织的原代培养物中分离出具有高ALDH活性（CD44 / CD24 / Aldefluor）的BCSC，并观察到与无ALDH活性的BCSC（CD44 / CD24 / Aldefluor）相比，这些细胞具有干细胞特性。此外，我们发现与非Aldefluor BCSC相比，Aldefluor BCSC具有更强的低氧反应以及随后HIF-1α表达的诱导。我们还发现，在Aldefluor BCSC中敲低HIF-1α而非HIF-2α会导致通过与上皮-间质转化相关基因的mRNA水平降低而使干细胞特性显著降低。事实上，在Aldefluor BCSC中过表达HIF-1α会导致Slug和Snail mRNA增加，并伴随E-钙黏蛋白的抑制和波形蛋白的增加。值得注意的是，长时间的低氧刺激促进了Aldefluor BCSC的表型变化，包括ALDH活性、肿瘤发生和转移，这表明肿瘤环境中的低氧可能影响BCSC的命运和乳腺癌的临床结局。
