Investigating the mechanisms of CD44s splice isoform in breast cancer metastasis

研究CD44s剪接亚型在乳腺癌转移中的机制

基本信息

批准号：
9312590
负责人：
Chonghui Cheng
金额：
$ 30.12万
依托单位：
BAYLOR COLLEGE OF MEDICINE
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-02-04 至 2019-01-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9312590
关键词：
Alternative Splicing Animals Binding Breast Cancer Cell Breast Cancer Patient Breast Cancer Treatment Breast cancer metastasis CD44 Antigens CD44 gene Cancer Etiology Cell Survival Cell surface Cells Cessation of life Clinical Complex Couples Cues Data Development Developmental Process Epithelial Exclusion Exons Feedback Genetic Transcription Goals Growth Health Human Hyaluronic Acid Hyaluronic Acid Binding IGF1R gene Ligand Binding MAP Kinase Gene Malignant Neoplasms Mammary Neoplasms Mediating Membrane Microdomains Mesenchymal Metastatic breast cancer Molecular Neoplasm Metastasis Pathogenesis Patients Play Protein Family Protein Isoforms RNA Splicing Receptor Protein-Tyrosine Kinases Reporting Research Role Signal Transduction Specimen Testing Up-Regulation extracellular in vivo malignant breast neoplasm novel novel therapeutic intervention palmitoylation promoter receptor sensor small hairpin RNA transcription factor treatment strategy tumor

项目摘要

DESCRIPTION (provided by applicant): Tumor metastasis is the major cause of cancer-related death in most types of human cancers including breast cancer. The long-term goal of our research is to better understand molecular mechanisms of alternative splicing underlying breast cancer metastasis. In this project we propose to investigate the mechanisms of a positive feedback loop involving the CD44s splice isoform and Akt activation that is responsible for breast tumor metastasis. The cell surface molecule CD44 is comprised of a family of proteins that are generated by alternative splicing. Inclusion of different combinations of variable exons generates CD44v. Conversely, exclusion of all of the variable exons produces CD44s. CD44 can be viewed as a sensor for extracellular cues. By forming co-receptor complexes with receptor tyrosine kinases (RTKs) and their growth factors, CD44 augments growth factor-stimulated RTK signaling. Our previous studies showed that CD44v and CD44s act on different signaling cascades: CD44s activates Akt signaling that is critical for promoting cell survival, while CD44v, on the other hand, promotes Ras/MAPK signaling resulting in a cell proliferative state. We recently reported that the CD44s isoform plays an essential role in epithelial-mesenchymal transition (EMT), a developmental process that is abnormally activated in tumor metastasis. We also found that depletion of CD44 by shRNA inhibits breast tumor metastasis in animals and that CD44s expression is upregulated in high-grade patient breast tumor specimens. These results suggest a critical role for CD44s in breast cancer metastasis. Mechanistically, we have shown that CD44s potentiates Akt activation and promotes cell survival. We also found that CD44s-dependent Akt signaling upregulates hyaluronic acid synthase 2 (HAS2) expression. Importantly, the HAS2 product, hyaluronic acid (HA), is a ligand that binds to CD44 and facilitates CD44s- mediated Akt activation. These observations led us to hypothesize that a positive feedback loop couples CD44s and Akt signaling, resulting in sustained Akt activation and promoting breast cancer metastasis. To test our hypothesis we have developed the following specific aims: Aim 1, Determine the molecular mechanism by which CD44s activates Akt signaling. Aim 2, Examine how CD44s-dependent Akt activation promotes HAS2 expression in breast cancer cells. Aim 3, Investigate whether HA, product of HAS2, promotes CD44s-dependent Akt activation and examine the positive-feedback loop in clinical breast tumor metastasis. Successfully accomplishing this project will define a novel mechanism of a positive feedback loop that promotes breast tumor metastasis. Intervening this positive feedback loop could offer an exciting new therapeutic approach for the treatment of metastatic breast cancer.

描述（由申请人提供）：肿瘤转移是大多数类型的人类癌症（包括乳腺癌）中与癌症相关的死亡的主要原因。我们研究的长期目标是更好地了解乳腺癌转移中选择性剪接的分子机制。在这个项目中，我们建议研究涉及 CD44s 剪接亚型和 Akt 激活的正反馈循环机制，该循环负责乳腺肿瘤转移。细胞表面分子 CD44 由通过选择性剪接产生的蛋白质家族组成。包含可变外显子的不同组合会生成 CD44v。相反，排除所有可变外显子会产生 CD44。 CD44 可以被视为细胞外信号的传感器。通过与受体酪氨酸激酶 (RTK) 及其生长因子形成共受体复合物，CD44 增强了生长因子刺激的 RTK 信号传导。我们之前的研究表明，CD44v 和 CD44s 作用于不同的信号级联：CD44s 激活对促进细胞存活至关重要的 Akt 信号传导，而 CD44v 则促进 Ras/MAPK 信号传导，从而导致细胞增殖状态。我们最近报道，CD44s亚型在上皮间质转化（EMT）中发挥重要作用，EMT是肿瘤转移中异常激活的发育过程。我们还发现，shRNA 消除 CD44 可抑制动物乳腺肿瘤转移，并且高级别患者乳腺肿瘤标本中 CD44 表达上调。这些结果表明 CD44 在乳腺癌转移中发挥着关键作用。从机制上讲，我们已经证明 CD44 可以增强 Akt 激活并促进细胞存活。我们还发现 CD44s 依赖性 Akt 信号传导上调透明质酸合酶 2 (HAS2) 的表达。重要的是，HAS2 产物透明质酸 (HA) 是一种配体，可与 CD44 结合并促进 CD44 介导的 Akt 激活。这些观察结果使我们推测，正反馈环路耦合 CD44 和 Akt 信号传导，导致 Akt 持续激活并促进乳腺癌转移。为了检验我们的假设，我们制定了以下具体目标：目标 1，确定 CD44s 激活 Akt 信号传导的分子机制。目标 2，检查 CD44s 依赖性 Akt 激活如何促进乳腺癌细胞中的 HAS2 表达。目标 3，研究 HAS2 的产物 HA 是否促进 CD44s 依赖性 Akt 激活，并检查临床乳腺肿瘤转移中的正反馈环。成功完成该项目将定义一种促进乳腺肿瘤转移的正反馈循环的新机制。干预这种正反馈循环可以为治疗转移性乳腺癌提供令人兴奋的新治疗方法。