Ebp1 activates podoplanin expression and contributes to oral tumorigenesis

Abstract

Podoplanin is highly expressed in human cancers. However, mechanisms regulating podoplanin expression remain elusive. Here we show that podoplanin promotes tumorigenesis of oral squamous cell carcinoma (OSCC) and precancerous cells both in vitro and in vivo, and the ErbB3-binding protein-1 (Ebp1) can be activated in oral tumorigenesis and can serve as a transcriptional activator to drive podoplanin expression in the malignant progression. Most of the OSCC cell lines have no detectable podoplanin protein in low-density cultures. However, the protein becomes detectable in high-density cultures and is required for in-vivo tumor formation of OSCC and oral premalignancies. In a high-density culture condition, podoplanin expression can be triggered at both mRNA and protein levels. In this condition, we showed that Ebp1 is upregulated, translocated from the cytoplasm to the nucleus and binds to the podoplanin promoter to result in a dramatic increase of podoplanin mRNA and protein. Ebp1 downregulation significantly reduced podoplanin expression levels in OSCC cells with a decreased anchorage-dependent growth, invasion and wound healing. Conversely, Ebp1 overexpression enhanced these malignant features through podoplanin upregulation both in vitro and in vivo. In 81 patients with oral premalignant lesions, we found that Ebp1 expression is strongly related to OSCC development. We conclude that Ebp1 has a key role in the upregulation of podoplanin and may contribute to oral tumorigenesis.

Podoplanin promotes malignancy through a diversity of strategies

“…An intriguing observation of these studies was that PDPN not only promoted cell migration and invasiveness, but also behaved as an oncogenic protein by inducing a full tumorigenic and metastatic phenotype [17] . These data were confirmed by knockdown experiments in which downregulation of PDPN in human oral SCC cell lines drastically reduced tumor formation in nude mice [18,19] . An explanation for this behavior has come recently from proteomic profiling studies in which upregulation and downregulation of pro-oncogenic and tumor suppressor proteins, respectively, were observed upon PDPN expression in MDCK cells [19] .…”

A piRNA-like Small RNA Induces Chemoresistance to Cisplatin-Based Therapy by Inhibiting Apoptosis in Lung Squamous Cell Carcinoma

“…Cell transfection was performed as described previously 10, 29, 30. In brief, transfection experiments were performed by using Opti-MEM medium and Lipofectamine 3000 (Invitrogen) for DNA oligonucleotides or Lipofectamine RNAiMAX (Invitrogen) for RNA oligonucleotides according to the manufacturer’s instructions.…”

“…Cell viability and IC 50 were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT, Life Technologies) assay as performed previously,10, 29, 30 and IC 50 was defined as the drug concentration that was required for 50% inhibition.…”

“…Cell cycle and apoptosis analyses were performed as described previously 10, 29, 30. In brief, cell cycle distribution and fluorescein isothiocyanate (FITC) Annexin V/PI (BD Pharmingen) for the apoptosis assay were analyzed by flow cytometry (Becton Dickinson), and DNA content and percentage of apoptosis cells were analyzed on a FACScan flow cytometer in combination with BD lysis software (Becton Dickinson).…”

New Insights into the Role of Podoplanin in Epithelial–Mesenchymal Transition

“…A recent report by Mei et al (2014) suggests that the cell density is another mechanism for transcriptional regulation of podoplanin. These authors have shown that podoplanin promotes tumorigenesis in oral squamous cell carcinomas, and that this process is mediated by transcriptional up-regulation of podoplanin due to the nuclear import of ErbB3-binding protein 1 (Ebp1) under conditions of high cell density.…”