Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan; Genomics Research Center, Academia Sinica, Taipei, Taiwan; Institute of Stem Cell and Translational Cancer Research, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan.
Stem Cells. 2014 Aug;32(8):2048-60. doi: 10.1002/stem.1735.
Overexpression of SH2-containing-5'-inositol phosphatase-2 (SHIP2) correlates with poor survival in breast cancer. However, its role in breast cancer stem cells (BCSCs) remains unclear. Here, we showed that the percentage of SHIP2(+) cells was positively correlated with that of CD24(-) CD44(+) cells in 60 breast cancer specimens. Among 20 estrogen receptor (ER)-negative samples, 17 had greater SHIP2 expression in CD24(-) CD44(+) subpopulation than the remaining subpopulation. Data mining of microarray analysis of 295 breast tumors showed a significant correlation of higher SHIP2 expression with distant metastasis. Examination of patient-derived mouse xenografts revealed that SHIP2 protein and its tyrosine 1135 phosphorylation were significantly higher in BCSCs, identified as CD24(-) CD44(+) or aldehyde dehydrogenase (ALDH(+)), than non-BCSCs. SHIP2 silencing or inhibitor of SHIP2 phosphatase significantly decreased mammosphere-forming efficiency, ALDH(+) subpopulation in vitro and tumorigenicity of BCSCs in vivo. Overexpression of SHIP2 enhanced the expression of epithelial-mesenchymal transition markers including vimentin (VIM), which was mainly expressed in ER-negative breast cancer cells with higher level in mammospheres than monolayer culture. Ablation of c-Jun N-terminal kinase 1 (JNK1), JNK2, or VIM diminished the increased ALDH(+) population and tumorigenicity, induced by SHIP2 overexpression. BCSCs displayed greater expression of phospho-JNK than non-BCSCs and silencing of JNK suppressed SHIP2-mediated upregulation of VIM. Furthermore, SHIP2 overexpression enhanced Akt activation, but Akt inhibition failed to influence SHIP2-induced phospho-JNK/VIM upregulation. In conclusion, SHIP2 plays a key role in BCSCs of ER-negative breast cancers through activation of Akt and JNK with upregulation of VIM and may serve as a target for therapy directed at BCSCs.
SHIP2 表达与乳腺癌不良预后相关。然而，SHIP2 在乳腺癌干细胞（BCSCs）中的作用尚不清楚。我们发现，在 60 例乳腺癌标本中，SHIP2(+)细胞的比例与 CD24(-) CD44(+)细胞的比例呈正相关。在 20 例雌激素受体（ER）阴性样本中，17 例 CD24(-) CD44(+)亚群中 SHIP2 的表达高于其余亚群。对 295 例乳腺癌的基因芯片分析数据挖掘表明，SHIP2 表达较高与远处转移显著相关。对患者来源的小鼠异种移植的检查表明，SHIP2 蛋白及其酪氨酸 1135 磷酸化在 BCSC 中，即 CD24(-) CD44(+)或醛脱氢酶（ALDH(+)），明显高于非 BCSC。SHIP2 沉默或 SHIP2 磷酸酶抑制剂显著降低了体外乳腺癌球体形成效率、ALDH(+)亚群和体内 BCSC 的致瘤性。SHIP2 的过表达增强了上皮-间充质转化标志物的表达，包括波形蛋白（VIM），VIM 主要在 ER 阴性乳腺癌细胞中表达，在球体培养中比单层培养中的表达更高。JNK1、JNK2 或 VIM 的缺失减少了 SHIP2 过表达引起的 ALDH(+)细胞群增加和致瘤性，而 JNK 的沉默则抑制了 SHIP2 介导的 VIM 上调。此外，BCSCs 显示出比非 BCSC 更高的磷酸化 JNK 表达，JNK 的沉默抑制了 SHIP2 诱导的 VIM 上调。总之，SHIP2 通过激活 Akt 和 JNK 以及上调 VIM 在 ER 阴性乳腺癌的 BCSC 中发挥关键作用，可能成为针对 BCSC 的治疗靶点。
