Klingbeil Pamela, Marhaba Rachid, Jung Thorsten, Kirmse Robert, Ludwig Thomas, Zöller Margot
Department of Tumor Progression and Immune Defense, University Hospital of Surgery, University of Heidelberg, Heidelberg, Germany.
Mol Cancer Res. 2009 Feb;7(2):168-79. doi: 10.1158/1541-7786.MCR-08-0207. Epub 2009 Feb 10.
CD44 designates a large family of proteins with a considerable structural and functional diversity, which are generated from one gene by alternative splicing. As such, the overexpression of CD44 variant isoform (CD44v) has been causally related to the metastatic spread of cancer cells. To study the underlying mechanism, stable knockdown clones with deletion of exon v7 containing CD44 isoforms (CD44v(kd)) of the highly metastatic rat adenocarcinoma line BSp73ASML (ASML(wt)) were established. ASML-CD44v(kd) clones hardly form lung metastases after intrafootpad application and the metastatic load in lymph nodes is significantly reduced. Rescuing, albeit at a reduced level, CD44v expression in ASML-CD44v(kd) cells (ASML-CD44v(rsc)) restores the metastatic potential. The following major differences in ASML(wt), ASML-CD44v(kd), and ASML-CD44v(rsc) clones were observed: (a) ASML(wt) cells produce and assemble a matrix in a CD44v-dependent manner, which supports integrin-mediated adhesion and favors survival. This feature is lost in the ASML-CD44v(kd) cells. (b) CD44v cross-linking initiates phosphatidylinositol 3-kinase/Akt activation in ASML(wt) cells. Accordingly, apoptosis resistance is strikingly reduced in ASML-CD44v(kd) cells. The capacity to generate an adhesive matrix but not apoptosis resistance is restored in ASML-CD44v(rsc) cells. These data argue for a 2-fold effect of CD44v on metastasis formation: CD44v-mediated matrix formation is crucial for the settlement and growth at a secondary site, whereas apoptosis resistance supports the efficacy of metastasis formation.
CD44指的是一个蛋白质大家族，其结构和功能具有相当大的多样性，这些蛋白质由一个基因通过可变剪接产生。因此，CD44变异体同工型（CD44v）的过表达与癌细胞的转移扩散存在因果关系。为了研究其潜在机制，我们建立了稳定敲低克隆，这些克隆缺失了高转移性大鼠腺癌细胞系BSp73ASML（ASML(wt)）中包含CD44同工型（CD44v）的外显子v7。在足垫内注射后，ASML-CD44v(kd)克隆几乎不形成肺转移，并且淋巴结中的转移负荷显著降低。在ASML-CD44v(kd)细胞（ASML-CD44v(rsc)）中恢复CD44v的表达（尽管水平有所降低）可恢复其转移潜能。我们观察到ASML(wt)、ASML-CD44v(kd)和ASML-CD44v(rsc)克隆存在以下主要差异：（a）ASML(wt)细胞以CD44v依赖的方式产生并组装基质，该基质支持整合素介导的黏附并有利于存活。这一特征在ASML-CD44v(kd)细胞中丧失。（b）CD44v交联在ASML(wt)细胞中启动磷脂酰肌醇3激酶/Akt激活。因此，ASML-CD44v(kd)细胞中的抗凋亡能力显著降低。ASML-CD44v(rsc)细胞恢复了产生黏附基质的能力，但未恢复抗凋亡能力。这些数据表明CD44v对转移形成有双重作用：CD44v介导的基质形成对于在次要部位的定植和生长至关重要，而抗凋亡能力则支持转移形成的效率。
