Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
Stem Cells. 2011 Jan;29(1):32-45. doi: 10.1002/stem.563.
Cancer stem cells (CSCs) are proposed to initiate cancer and propagate metastasis. Breast CSCs identified by aldehyde dehydrogenase (ALDH) activity are highly tumorigenic in xenograft models. However, in patient breast tumor immunohistological studies, where CSCs are identified by expression of ALDH isoform ALDH1A1, CSC prevalence is not correlative with metastasis, raising some doubt as to the role of CSCs in cancer. We characterized the expression of all 19 ALDH isoforms in patient breast tumor CSCs and breast cancer cell lines by total genome microarray expression analysis, immunofluorescence protein expression studies, and quantitative polymerase chain reaction. These studies revealed that ALDH activity of patient breast tumor CSCs and cell lines correlates best with expression of another isoform, ALDH1A3, not ALDH1A1. We performed shRNA knockdown experiments of the various ALDH isoforms and found that only ALDH1A3 knockdown uniformly reduced ALDH activity of breast cancer cells. Immunohistological studies with fixed patient breast tumor samples revealed that ALDH1A3 expression in patient breast tumors correlates significantly with tumor grade, metastasis, and cancer stage. Our results, therefore, identify ALDH1A3 as a novel CSC marker with potential clinical prognostic applicability, and demonstrate a clear correlation between CSC prevalence and the development of metastatic breast cancer.
癌症干细胞（CSCs）被认为是引发癌症和促进转移的根源。通过醛脱氢酶（ALDH）活性鉴定的乳腺癌干细胞在异种移植模型中具有高度致瘤性。然而，在患者乳腺癌肿瘤免疫组织化学研究中，通过 ALDH 同工型 ALDH1A1 的表达来鉴定 CSCs 时，CSC 的流行率与转移并不相关，这引发了对 CSCs 在癌症中作用的一些质疑。我们通过全基因组微阵列表达分析、免疫荧光蛋白表达研究和定量聚合酶链反应，对患者乳腺癌 CSCs 和乳腺癌细胞系中所有 19 种 ALDH 同工型的表达进行了特征描述。这些研究表明，患者乳腺癌 CSCs 和细胞系的 ALDH 活性与另一种同工型 ALDH1A3 的表达相关性最好，而不是 ALDH1A1。我们对各种 ALDH 同工型进行了 shRNA 敲低实验，发现只有 ALDH1A3 敲低能均匀地降低乳腺癌细胞的 ALDH 活性。对固定的患者乳腺癌肿瘤样本进行免疫组织化学研究表明，患者乳腺癌中 ALDH1A3 的表达与肿瘤分级、转移和癌症分期显著相关。因此，我们的研究结果确定 ALDH1A3 为一种具有潜在临床预后应用价值的新型 CSC 标志物，并证实了 CSC 流行率与转移性乳腺癌发展之间的明确相关性。
