No abstract

The activation of cancer-associated fibroblasts (CAFs) is a key event in tumor progression, and alternative extracellular matrix (ECM) proteins derived from CAFs induce ECM remodeling and cancer cell invasion. Here we found that miR-200 s, which are generally downregulated in activated CAFs in breast cancer tissues and in normal fibroblasts (NFs) activated by breast cancer cells, are direct mediators of NF reprogramming into CAFs and of ECM remodeling. NFs with downregulated miR-200 s displayed the traits of activated CAFs, including accelerated migration and invasion. Ectopic expression of miR-200 s in CAFs at least partially restored the phenotypes of NFs. CAF activation may be governed by the targets of miR-200 s, Fli-1 and TCF12, which are responsible for cell development and differentiation; Fli-1 and TCF12 were obviously elevated in CAFs. Furthermore, miR-200 s and their targets influenced collagen contraction by CAFs. The upregulation of fibronectin and lysyl oxidase directly by miR-200 or indirectly through Fli-1 or TCF12 contributed to ECM remodeling, triggering the invasion and metastasis of breast cancer cells both in vitro and vivo. Thus, these data provide important and novel insights into breast CAF activation and ECM remodeling, which trigger tumor cell invasion.

SummaryCancer stem cells (CSCs) are a subpopulation of neoplastic cells with self‐renewal capacity and limitless proliferative potential as well as high invasion and migration capacity. These cells are commonly associated with epithelial‐mesenchymal transition (EMT), which is also critical for tumor metastasis. Recent studies illustrate a direct link between EMT and stemness of cancer cells. Long non‐coding RNAs (lncRNAs) have emerged as important new players in the regulation of multiple cellular processes in various diseases. To date, the role of lncRNAs in EMT‐associated CSC stemness acquisition and maintenance remains unclear. In this study, we discovered that a set of lncRNAs were dysregulated in Twist‐positive mammosphere cells using lncRNA microarray analysis. Multiple lncRNAs‐associated canonical signaling pathways were identified via bioinformatics analysis. Especially, the Shh‐GLI1 pathway associated lncRNA‐Hh, transcriptionally regulated by Twist, directly targets GAS1 to stimulate the activation of hedgehog signaling (Hh). The activated Hh increases GLI1 expression, and enhances the expression of SOX2 and OCT4 to play a regulatory role in CSC maintenance. Thus, the mammosphere‐formation efficiency (MFE) and the self‐renewal capacity in vitro, and oncogenicity in vivo in Twist‐positive breast cancer cells are elevated. lncRNA‐Hh silence in Twist‐positive breast cells attenuates the activated Shh‐GLI1 signaling and decreases the CSC‐associated SOX and OCT4 levels, thus reduces the MFE and tumorigenesis of transplanted tumor. Our results reveal that lncRNAs function as an important regulator endowing Twist‐induced EMT cells to gain the CSC‐like stemness properties. Stem Cells 2016;34:55–66

No abstract

Summary The ATM kinase plays a critical role in the maintenance of genetic stability. ATM is activated in response to DNA damage and is essential for cell cycle checkpoints. Here, we report that ATM is activated in mitosis in the absence of DNA damage. We demonstrate that mitotic ATM activation is dependent on the Aurora-B kinase and that Aurora-B phosphorylates ATM on serine 1403. This phosphorylation event is required for mitotic ATM activation. Further, we show that loss of ATM function results in shortened mitotic timing and a defective spindle checkpoint, and that abrogation of ATM Ser1403 phosphorylation leads to this spindle checkpoint defect. We also demonstrate that mitotically-activated ATM phosphorylates Bub1, a critical kinetochore protein, on Ser314. ATM-mediated Bub1 Ser314 phosphorylation is required for Bub1 activity and is essential for the activation of the spindle checkpoint. Collectively, our data highlight mechanisms of a critical function of ATM in mitosis.