title: CD24 associates with EGFR and supports EGF/EGFR signaling via RhoA in gastric cancer cells.
abstract: BACKGROUND
  CD24, a mucin-like membrane glycoprotein, plays a critical role in carcinogenesis, but its role in human gastric cancer and the underlying mechanism remains undefined.
  
  
  METHODS
  The contents of CD24 and epidermal growth factor receptor (EGFR) in gastric cancer cells (SGC-7901 and BGC-823) and non-malignant gastric epithelial cells (GES-1) were evaluated by Western blotting assay. Cellular EGFR staining was examined by immunofluorescence assay. Cell migration rate was measured by wound healing assay. The effects of depletion/overexperssion of CD24 on EGFR expression and activation of EGF/EGFR singaling pathways were evaluated by immunofluorescence, qPCR, Western blotting and flow cytometry techniques. RhoA activity was assessed by pulldown assay. CD24 and EGFR expression patterns in human gastric tumor samples were also investigated by immunohistochemistry staining.
  
  
  RESULTS
  CD24 was overexpressed in human gastric cancer cells. Ectopic expression of CD24 in gastric epithelial cells augmented the expression of EGFR, while knockdown of CD24 in gastric cancer cells decreased the level of EGFR and cell migration velocity. To further explore the mechanisms, we investigated the effect of CD24 expression on EGF/EGFR signaling. We noticed that this effect of CD24 on EGFR expression was dependent on promoting EGFR internalization and degradation. Lower ERK and Akt phosphorylations in response to EGF stimulation were observed in CD24-depleted cells. In addition, we noticed that the effect of CD24 on EGFR stability was mediated by RhoA activity in SGC-7901 gastric cancer cells. Analysis of gastric cancer specimens revealed a positive correlation between CD24 and EGFR levels and an association between CD24 expression and worse prognosis.
  
  
  CONCLUSIONS
  Thus, these findings suggest for the first time that CD24 regulates EGFR signaling by inhibiting EGFR internalization and degradation in a RhoA-dependent manner in gastric cancer cells.
authors.affiliation: Cancer Center, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, Jiangsu, China. dengwenjie2014@163.com.|Department of Physiology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. dengwenjie2014@163.com.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Deng
authors.affiliation: Cancer Center, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, Jiangsu, China. lgu@njmu.edu.cn.|Department of Physiology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. lgu@njmu.edu.cn.|Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. lgu@njmu.edu.cn.
authors.forename: Luo
authors.initials: L
authors.lastname: Gu
authors.affiliation: Department of Physiology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. lixiaojieshmily@126.com.
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Physiology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. zhjch@njmu.edu.cn.
authors.forename: Jianchao
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Cancer Center, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, Jiangsu, China. zeater87@126.com.|Department of Physiology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. zeater87@126.com.|Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. zeater87@126.com.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Physiology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. duanbiao1207@163.com.
authors.forename: Biao
authors.initials: B
authors.lastname: Duan
authors.affiliation: Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. olive930@163.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Cui
authors.affiliation: Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. cindydongjing@gmail.com.|Epidemiology and Biostatistics and Ministry of Education (MOE) Key Laboratory for Modern Toxicology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. cindydongjing@gmail.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Dong
authors.affiliation: Cancer Center, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, Jiangsu, China. dujun@njmu.edu.cn.|Department of Physiology, Nanjing Medical University, Nanjing, 210029, Jiangsu, China. dujun@njmu.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Du
mesh_terms: D051927:CD24 Antigen / Q000378:metabolism*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002465:Cell Movement; D015536:Down-Regulation; D004705:Endocytosis; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D059748:Proteolysis; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D051927:CD24 Antigen; C497889:CD24 protein, human; D034741:RNA, Small Interfering; C066737:RHOA protein, human; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D020742:rhoA GTP-Binding Protein
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