HAS2调控HA异常潴留促进乳腺癌成团侵袭前缘细胞不完全EMT及获得干细胞性在侵袭转移中的作用及机制

Collective cell invasion is the first step in the deadly process of breast cancer metastasis. Recent evidence suggested that the border cells in collective invasion might be the invasion-initiating cells, which may display partial epithelial-mesenchymal transition (pEMT) phenotype in response to tumor microenvironment signals. However, the mechanisms involved are unknown. Cells in a pEMT phenotype were reported to be likely to gain “stemness” and behave operationally as cancer stem cells (CSCs). Therefore, cells in the border of invasion clusters may have both pEMT phenotype and CSCs markers. The border cell niches may be remodeled by the hyaluronan synthase 2 (HAS2) and aberrant hyaluronan (HA), which is the main component of the extracellular matrix (ECM), and therefore influencing tumor metastasis. Previous work from our laboratory showed that ①In 2-D collective migration assay, the border cells displayed high expression of HAS2 on their invasion edge, and expressed CSC markers(CD44+CD24-). ②HA is accumulated primarily at the breast tumor-invasive edge adjacent to the tumor stromal, which is associated with lymph node metastasis, whereas very little in the central parts of the tumors. ③Over expression of HAS2 using gene transfection induced changes in epithelial cell polarity. All results suggested that the HAS2/HA, located at the tumor-invasive edge, might play a crucial role in collective invasion. For the first time, this project try to understand the effects of HAS2/HA on the pEMT status and the stemness of the border cells in collective invasion, including two parts: ①To study the role of aberrant HA regulated by HAS2 in triggering the formation of pEMT phenotype and stemness of the border cells. ②To study the mechanisms involved. The project may provide a new insight to elucidate the mechanism of metastasis in breast cancer.

乳腺癌成团侵袭(collective invasion)是转移首要环节，是近年热点。新近报道侵袭前缘细胞与微环境相互作用发生不完全EMT(partial EMT, pEMT)，可能是启动成团侵袭的关键，机制未明。据报pEMT态细胞易受微环境影响而获得肿瘤干细胞CSC干性。推测成团侵袭前缘细胞可能兼具pEMT和CSC特性而促进侵袭。透明质酸HA与其合成酶HAS2是重塑微环境的重要成分，与转移相关。本课题前期发现①单层细胞成团迁移前缘高表达HAS2并呈现CSC特性②临床乳腺癌边缘HA异常潴留而内部较少③转染HAS2基因诱发细胞极性改变。提示特异位于瘤边缘的HAS2/HA可能与前缘细胞功能有关。因此本研究首次探讨HAS2/HA对成团侵袭前缘细胞的调控及机制。内容①阐明乳腺癌相关HAS2/HA在成团侵袭前缘细胞的pEMT形成及CSC特性获得中的调节作用②探讨相关分子机制。力从新视角揭示乳癌转移机制

乳腺癌成团侵袭(collective invasion)是转移首要环节，是近年热点。新近报道侵袭前缘细胞与微环境相互作用发生不完全EMT(partial EMT, pEMT)，可能是启动成团侵袭的关键，机制未明。本研究首次探讨了HAS2/HA对成团侵袭前缘细胞的调控及机制，初步阐明乳腺癌相关HAS2/HA在成团侵袭前缘细胞的pEMT形成及CSC特性获得中的调节作用及相关分子机制。结果发现①成团迁移前缘细胞高表达HAS2并呈现CSC特性②临床乳腺癌边缘HA异常潴留而内部较少③转染HAS2基因诱发细胞极性改变。提示特异位于瘤边缘的HAS2/HA可能与前缘细胞功能有关。进一步实验分析发现，HAS2调节管腔型乳腺癌细胞的恶性表型和侵袭性伪足的形成；证实HA的受体CD44特异性高表达在乳腺癌成团侵袭前缘的先导细胞表面，在调控乳腺癌“成团侵袭”形成中发挥关键作用；通过体内、外实验，初步探明了CD44high细胞在乳腺癌成团侵袭中的引领作用及其不完全EMT的分子表型特征；并且CD44表达高/低细胞之间可发生动态转变，且受微环境调控；但是CD44hi和CD44lo细胞亚群之间的动态转变可能与CSC-non-CSC之间的转变无关；随后发现，HAS2/HA/CD44通过与雌激素受体（ER）的相互协作激活PI3K通路，诱导管腔型乳腺癌细胞获得pEMT及干性特征。从新视角揭示了乳癌转移的分子机制。

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