Department of Biochemistry, School of Medicine, Taipei Medical University, Taipei 110, Taiwan, Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan,
Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan, Graduate Institute of Oral Biology, School of Dentistry, College of Medicine, National Taiwan University, Taipei 106, Taiwan and.
Carcinogenesis. 2014 Nov;35(11):2425-35. doi: 10.1093/carcin/bgu139. Epub 2014 Jun 26.
Metastatic disease is the leading cause of cancer mortality. Identifying biomarkers and regulatory mechanisms is important toward developing diagnostic and therapeutic tools against metastatic cancer. In this study, we demonstrated that podocalyxin-like 1 (PODXL) is overexpressed in breast tumor cells and increased in lymph node metastatic cancer. Mechanistically, we found that the expression of PODXL was associated with cell motility and invasiveness. Suppression of PODXL in MDA-MB-231 cells reduced lamellipodia formation and focal adhesion kinase (FAK) and paxillin phosphorylation. PODXL knockdown reduced the formation of invadopodia, such as inhibiting the colocalization of F-actin with cortactin and suppressing phosphorylation of cortactin and neural Wiskott-Aldrich syndrome protein. Conversely, overexpression of PODXL in MCF7 cells induced F-actin/cortactin colocalization and enhanced invadopodia formation and activation. Invadopodia activity and tumor invasion in PODXL-knockdown cells are similar to that in cortactin-knockdown cells. We further found that the DTHL motif in PODXL is crucial for regulating cortactin phosphorylation and Rac1/Cdc42 activation. Inhibition of Rac1/Cdc42 impeded PODXL-mediated cortactin activation and FAK and paxillin phosphorylation. Moreover, inhibition of PODXL in MDA-MB-231 cells significantly suppressed tumor colonization in the lungs and distant metastases, similar to those in cortactin-knockdown cells. These findings show that overexpression of PODXL enhanced invadopodia formation and tumor metastasis by inducing Rac1/Cdc42/cortactin signaling network.
转移性疾病是癌症死亡的主要原因。鉴定生物标志物和调控机制对于开发针对转移性癌症的诊断和治疗工具非常重要。在这项研究中，我们证明了 Podocalyxin-like 1（PODXL）在乳腺癌细胞中过表达，并在淋巴结转移性癌症中增加。从机制上讲，我们发现 PODXL 的表达与细胞迁移和侵袭性有关。在 MDA-MB-231 细胞中抑制 PODXL 的表达会减少片状伪足的形成和粘着斑激酶（FAK）和桩蛋白的磷酸化。PODXL 的敲低会减少侵袭小体的形成，例如抑制 F- 肌动蛋白与桩蛋白的共定位，并抑制桩蛋白和神经 Wiskott-Aldrich 综合征蛋白的磷酸化。相反，在 MCF7 细胞中过表达 PODXL 会诱导 F- 肌动蛋白/桩蛋白共定位，并增强侵袭小体的形成和激活。PODXL 敲低细胞中的侵袭小体活性和肿瘤侵袭与桩蛋白敲低细胞相似。我们进一步发现 PODXL 中的 DTHL 基序对于调节桩蛋白的磷酸化和 Rac1/Cdc42 的激活至关重要。抑制 Rac1/Cdc42 会阻碍 PODXL 介导的桩蛋白激活以及 FAK 和桩蛋白的磷酸化。此外，在 MDA-MB-231 细胞中抑制 PODXL 会显著抑制肺和远处转移中的肿瘤定植，与桩蛋白敲低细胞相似。这些发现表明，PODXL 的过表达通过诱导 Rac1/Cdc42/桩蛋白信号网络增强侵袭小体的形成和肿瘤转移。
