Authors' Affiliations: Marlene and Stewart Greenebaum National Cancer Institute Cancer Center; Program in Molecular Medicine; and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland.
Cancer Res. 2014 Feb 15;74(4):1250-60. doi: 10.1158/0008-5472.CAN-13-1778. Epub 2013 Dec 26.
Cancer stem-like cells (CSC) and circulating tumor cells (CTC) have related properties associated with distant metastasis, but the mechanisms through which CSCs promote metastasis are unclear. In this study, we report that breast cancer cell lines with more stem-like properties display higher levels of microtentacles (McTN), a type of tubulin-based protrusion of the plasma cell membrane that forms on detached or suspended cells and aid in cell reattachment. We hypothesized that CSCs with large numbers of McTNs would more efficiently attach to distant tissues, promoting metastatic efficiency. The naturally occurring stem-like subpopulation of the human mammary epithelial (HMLE) cell line presents increased McTNs compared with its isogenic non-stem-like subpopulation. This increase was supported by elevated α-tubulin detyrosination and vimentin protein levels and organization. Increased McTNs in stem-like HMLEs promoted a faster initial reattachment of suspended cells that was inhibited by the tubulin-directed drug, colchicine, confirming a functional role for McTNs in stem cell reattachment. Moreover, live-cell confocal microscopy showed that McTNs persist in breast stem cell mammospheres as flexible, motile protrusions on the surface of the mammosphere. Although exposed to the environment, they also function as extensions between adjacent cells along cell-cell junctions. We found that treatment with the breast CSC-targeting compound curcumin rapidly extinguished McTN in breast CSC, preventing reattachment from suspension. Together, our results support a model in which breast CSCs with cytoskeletal alterations that promote McTNs can mediate attachment and metastasis but might be targeted by curcumin as an antimetastatic strategy.
癌症干细胞样细胞 (CSC) 和循环肿瘤细胞 (CTC) 具有与远处转移相关的特性，但 CSC 促进转移的机制尚不清楚。在这项研究中，我们报告具有更多干细胞样特性的乳腺癌细胞系显示出更高水平的微刺突 (McTN)，这是一种细胞浆膜的基于微管蛋白的突起，在分离或悬浮的细胞上形成，并有助于细胞重新附着。我们假设具有大量 McTN 的 CSC 将更有效地附着到远处的组织，从而提高转移效率。人乳腺上皮 (HMLE) 细胞系的天然存在的干细胞样亚群与同源的非干细胞样亚群相比，具有更多的 McTN。这种增加得到了α-微管蛋白去酪氨酸化和波形蛋白蛋白水平和组织的支持。HMLE 干细胞样细胞中 McTN 的增加促进了悬浮细胞更快的初始重新附着，这一过程被微管定向药物秋水仙碱抑制，证实了 McTN 在干细胞重新附着中的功能作用。此外，活细胞共聚焦显微镜显示，McTN 在乳腺干细胞球体中作为球体表面上灵活、可移动的突起持续存在。尽管暴露在环境中，它们也作为细胞-细胞连接沿细胞-细胞连接的延伸物发挥作用。我们发现，用针对乳腺癌干细胞的化合物姜黄素处理会迅速消除乳腺癌干细胞中的 McTN，从而阻止悬浮细胞的重新附着。总之，我们的结果支持这样一种模型，即促进 McTN 的乳腺癌 CSC 的细胞骨架改变可以介导附着和转移，但可能被姜黄素作为一种抗转移策略所靶向。
