Defining the CD44-STAT3 axis in the pathogenesis of triple-negative breast cancer

描述（由申请人提供）：三阴性乳腺癌（TNBC）不表达雌激素受体或孕激素受体或过表达人表皮生长因子相关2（HER 2），是临床上侵袭性肿瘤，特征为高转移率和预后不良。复发性TNBC被认为是由逃避化疗的细胞毒性作用的肿瘤起始细胞亚群介导的，其特征在于CD 44的细胞表面表达。TNBC细胞系中CD 44+细胞的高发生率，其中许多也具有转录因子STAT 3的组成性激活，表明CD 44不仅仅是肿瘤起始细胞的标志物，正如通常所认为的那样，而是直接参与调节STAT 3活性并促成这些细胞的不适当存活。我们已经证明，在TNBC细胞中，CD 44敲低降低STAT 3转录活性，但不降低STAT 3酪氨酸或丝氨酸磷酸化。CD 44敲低还增加了TNBC细胞对常规化疗剂的敏感性，支持了CD 44在这些肿瘤发病机制中的重要性。然而，CD 44调节TNBC中STAT 3活性的分子机制尚不清楚。 本研究提案的目标是：（1）阐明CD 44调节TNBC中STAT 3转录活性的信号通路，（2）确定CD 44在TNBC中STAT 3介导的基因调节中的功能，使用染色质免疫沉淀来分析CD 44在定义STAT 3基因组结合位点中的作用，并使用质谱来鉴定CD 44在STAT 3基因组结合位点上的功能。（3）剖析STAT 3抑制对CD 44+与CD 44- TNBC亚群的生物学的影响，使用BH 3谱来测量细胞引发凋亡。 该提案的完成将提供对CD 44-STAT 3轴在TNBC发病机制中的作用的见解，TNBC的侵袭性对有效治疗构成严重障碍。阐明CD 44表达如何有助于TNBC的侵袭性表型将扩展我们对STAT 3生物学的知识，并可能为具有高CD 44表达的肿瘤提供新的治疗方法。此外，对CD 44信号通路的进一步了解可能最终提供有关其他癌症表面标志物如何参与肿瘤发生的线索。

DESCRIPTION (provided by applicant): Triple-negative breast cancers (TNBCs), which do not express estrogen receptor or progesterone receptor or overexpress human epidermal growth factor-related 2 (HER2), are clinically aggressive tumors characterized by high rates of metastases and poor prognosis. Recurrent TNBC is thought to be mediated by a subpopulation of tumor-initiating cells that escape the cytotoxic effects of chemotherapy and are characterized by cell surface expression of CD44. The high incidence of CD44+ cells in TNBC cell lines, many of which also have constitutive activation of the transcription factor STAT3, suggests that CD44 is not merely a marker of tumor-initiating cells, as it is generally viewed, but rather directly involved in modulating STAT3 activity and contributing to the inappropriate survival of these cells. We have demonstrated that CD44 knockdown decreases STAT3 transcriptional activity but not STAT3 tyrosine or serine phosphorylation in TNBC cells. CD44 knockdown also increases TNBC cell sensitivity to conventional chemotherapeutic agents, supporting the importance of CD44 in the pathogenesis of these tumors. However, the molecular mechanism by which CD44 regulates STAT3 activity in TNBC is not yet understood. The goals of this research proposal are: (1) To elucidate the signaling pathway by which CD44 modulates STAT3 transcriptional activity in TNBC, (2) To determine the function of CD44 in STAT3-mediated gene regulation in TNBC, using chromatin immunoprecipitation to analyze the role of CD44 in defining STAT3 genomic binding sites and using mass spectrometry to identify the function of CD44 on STAT3-associated proteins, and (3) To dissect the effect of STAT3 inhibition on the biology of CD44+ versus CD44- TNBC subpopulations, using BH3 profiling to measure cell priming for apoptosis. The completion of this proposal will provide insights into the role of the CD44-STAT3 axis in the pathogenesis of TNBC whose aggressive nature presents serious obstacles to effective treatment. Elucidating how CD44 expression contributes to the aggressive phenotype of TNBC will expand our knowledge of STAT3 biology and may suggest novel therapeutic approaches for tumors with high CD44 expression. Furthermore, increased understanding of the CD44 signaling pathway may ultimately provide clues about how other cancer surface markers are involved in tumorigenesis.