doi:10.1369/jhc.5A6881.2006
Volume 54 (8): 889-896, 2006 Copyright ©The Histochemical Society, Inc. Altered Expression of Ezrin in Esophageal Squamous Cell Carcinoma
Department of Biochemistry and Molecular Biology (HZ,HZ,YN,EL) and Department of Pathology (LX,XW,RZ,QL,ZS), Medical College of Shantou University, Shantou, Guangdong Province, People's Republic of China; Institute of Virology and Pharmacology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing, People's Republic of China (LX); and Department of Cardiothoracic Surgery, The First Affiliated Hospital of Shantou University, Shantou, Guangdong Province, People's Republic of China (DX) Correspondence to: Enmin Li, Department of Biochemistry and Molecular Biology, Medical College of Shantou University, 22 Xinling Road, Shantou City, Guangdong Province, P.R. China. E-mail: nmli{at}stu.edu.cn
Ezrin is a membranecytoskeletal linker belonging to the ezrinradixinmoesin (ERM) family and has been suggested to be involved in tumorigenesis. In this study we investigated ezrin expression pattern in normal esophageal mucosa and esophageal squamous cell carcinoma (ESCC) and the correlation with clinical characteristics. Immunohistochemical staining showed a tendency for ezrin to translocate from membrane to cytoplasm in the progression from normal epithelium to invasive carcinoma of the esophagus. By Western blot, we found that ezrin expression was downregulated in 13 ESCC specimens and upregulated in 36 others. Moreover, quantitative real-time RT-PCR demonstrated that ezrin mRNA level in normal esophageal mucosa was 3.60 ± 3.60 times that in ESCC (p<0.001). Proliferating cell nuclear antigen (PCNA) expression level was higher in ezrin downregulated group compared with that in ezrin upregulated group (p<0.05). However, there was no significant association between ezrin expression and clinical characteristics. The results suggested that the localization of ezrin by immunohistochemistry may be useful in the diagnosis of ESCC, and ezrin may play a suppressive role in the tumorgenesis of ESCC. (J Histochem Cytochem 54:889896, 2006)
Key Words: esophageal carcinoma ezrin immunohistochemistry real-time RT-PCR proliferating cell nuclear antigen
THE ACTIN-BASED CYTOSKELETON plays a crucial role in eukaryotic cell motility and maintenance of cell shape. Actin filaments must associate with the plasma membrane to regulate cell morphology as well as local membrane deformations. Ezrin is one of the proteins believed to crosslink the plasma membrane to actin filaments and to modulate this association (Turunen et al. 1994
Ezrin usually concentrates at actin-rich surface structures such as the apical domain of polarized cells (Bretscher et al. 1997
Except for the redistribution, the expression level of ezrin was also suggested to be associated with tumorigenesis as well as motility and invasive behavior of malignant cells. There are two different opinions about the role of ezrin in tumor progression. One opinion supported that ezrin was a suppressor with ezrin downregulated in some tumor cells (Tokunou et al. 2000
Our group previously proved ezrin was overexpressed in malignantly transformed esophageal epithelial cell line compared with immortalized phase cell line (Shen et al. 2003
Patients and Tissue Specimens Eighty nine paraffin sections including 40 ESCC, 42 normal esophageal mucosa, and 7 special paraffin sections of full-length mucosa layer from the distant margin to the cancer focus of the excised esophagus were obtained for immunohistochemical staining from the Clinical Pathology Department of the First Affiliated Hospital of Shantou University from 2001 to 2003. The sections of normal mucosa, which had been histologically evaluated by hematoxylin and eosin staining, were taken from the matched distal resected margin of ESCC samples. All specimens were fixed in 10% formaldehyde solution, embedded in paraffin blocks, and then cut into 4-µm-thick sections. Frozen ESCC tissues and adjacent normal esophageal mucosa tissues (taken as far as possible from neoplasia) were collected for Western blot and real-time RT-PCR from 49 patients with primary ESCC who underwent surgery in the Department of Cardiothoracic Surgery of the First Affiliated Hospital of Shantou University from 20032004. All samples were immediately frozen in liquid nitrogen following surgery and stored at 70C until RNA isolation. All tumors were confirmed as ESCC by the Clinical Pathology Department of the Hospital. All cases were classified according to the International Union Against Cancer TumorNodeMetastasis Classification, 5th ed. Evaluation of tumor differentiation was based on histological criteria of the guidelines of WHO Pathological Classification of Tumors. The study was approved by the Ethics Committee of the First Affiliated Hospital of Shantou University, and only patients who gave written informed consent were included. None of the patients had radiotherapy or chemotherapy prior to surgery.
Immunohistochemical Staining As negative controls, one was prepared by substituting PBS for the primary antibody, and the other was applied using preimmune serum (1:1000). A metastatic breast carcinoma shown previously to have immunoreactivity was used as a positive control to confirm immunoreactivity in each series of experiments. Ezrin immunoreactivity was evaluated. Either membrane or cytoplasmic staining was considered positive. In each case, the intensity of membrane or cytoplasmic staining was scored as follows: no visible staining or appreciable staining in <5% of cells, 0; faint staining detected in >5% of cells, 1+; weak to moderate staining in >5% of cells, 2+; strong staining in >5% of cells, 3+. Cases classified as 0 were considered "negative," and those scored as 1+, 2+, or 3+ were considered "positive." All sections were evaluated independently by two investigators who had no prior knowledge of the patients' clinical information. When the opinions of the two evaluators were different, agreement was reached by careful discussion.
Western Blot Analysis
Preparation of Total RNA and Real-time RT-PCR
Statistical Analysis
Translocalization of Ezrin in the Progression of ESCC A significant difference of ezrin distribution was observed in normal esophageal mucosa and ESCC by antibody staining. Ezrin immunoreactivity was apparent in the cell membranes of 41/42 (97.6%) normal esophageal mucosa cases (Figures 1A and 1B). In contrast, ESCC samples showed mainly cytoplasmic staining in 31/40 (77.5%) or both membranous and cytoplasmic staining in 9/40 (22.5%). Of the 40 cases of ESCC, 9 were well differentiated and 31 were moderately differentiated, and ezrin was found to be mainly diffused in the cytoplasm in 29/31 (93.5%) moderately differentiated samples (Figure 1D), whereas it was preferentially localized both in the membranous region and in the cytoplasm in 7/9 (77.8%) well-differentiated ESCC (Figure 1C). A significant difference of ezrin distribution was found between well- and moderately differentiated groups (p<0.05). Results of these immunohistochemical examinations are summarized in Table 1 .
We also investigated ezrin distribution in the progression from normal epithelium to invasive carcinoma of the esophagus using seven special paraffin sections of full-length mucosa layer from the distant margin to the cancer focus of the excised esophagus. In addition to the normal epithelium (7/7) and invasive cancer of esophagus (7/7), these seven special paraffin sections contained esophageal lesions of simple hyperplasia (3/7), low-grade dysplasia (1/7), and carcinoma in situ (3/7). In normal epithelium, positive immunostaining was mainly apparent on the membrane in all cases (Figures 2A and 2B). For simple hyperplasia (2/3), positive signal was predominantly observed in both membrane and the cytoplasm of the basal layer and the spinous layer cells (Figure 2C). In low-grade dysplastic lesions and all carcinoma in situ and invasive cancers, most cells demonstrated only diffusely cytoplasmic staining (Figures 2D2F).
Ezrin Protein Level in ESCC and the Adjacent Normal Mucosa We performed Western blot to identify the expression level of ezrin in esophageal tissues by using the frozen stored ESCC and the adjacent normal epithelial tissues. The intensity ratio of ezrin to ß-actin was scored. Each specimen was evaluated by the ratio of the ezrin protein level in the tumor to that in the adjacent normal epithelial tissues (T/N ratio). Ezrin expression was upregulated (T/N ratio >1.0) in 13 (26.5%) cases and downregulated (T/N ratio <1.0) in 36 (73.5%) cases (Figure 3 and Figure 4 ).
Ezrin mRNA Level in ESCC and the Adjacent Normal Mucosa With real-time RT-PCR, the relative copy number of ezrin mRNA was evaluated by the ratio of the absolute copy number of ezrin mRNA to the copy number of ß-actin mRNA. The result demonstrated that ezrin mRNA level in normal esophageal mucosa was 3.60 ± 3.60 times that in ESCC (p<0.001).
Correlation between Level of Ezrin Protein and Cell Proliferation
Correlation between Clinical Characteristics and Level of Ezrin Protein in ESCC Correlation between ezrin protein expression and clinical characteristics such as pathologic grades, tumornodemetastasis, and stages was simultaneously investigated (Table 3 ). However, there was no significant association between ezrin expression and any of the clinical characteristics.
In this report we showed the differences of ezrin expression at transcriptional and translational levels and ezrin subcellular localization in the progression from normal epithelium to invasive carcinoma of the esophagus. We also demonstrated that ezrin expression level inversely correlated with cell proliferation. From immunohistochemistry data, we found that ezrin had a tendency to translocate from membrane to cytoplasm in the malignant transformation progress of esophageal epithelium. In comparison to normal esophageal epithelium, which demonstrated a mainly membranous staining pattern, ezrin distribution in simple hyperplasia lesions extended to the cytoplasm. In case of low-grade dysplasia, carcinoma in situ, and invasive cancer, ezrin was prominently cytoplasmic diffuse. Furthermore, in most tumor cells, ezrin protein and mRNA levels were reduced.
According to previous studies of our group, ezrin was upregulated in the malignantly transformed esophageal epithelial cell line (Shen et al. 2003
Ezrin has been reported to be concentrated in actin-rich surface structures such as microvilli, membrane ruffles, and protrusions and can regulate the structure of the cortical cytoskeleton to control cell surface topography with subcellular redistribution (Bretscher et al. 1997
Ezrin was demonstrated overexpressing in some tumor tissues or cell lines and was required for metastasis (Khanna et al. 2004 Even though the mechanism of ezrin downregulation in tumor cells is not clear, it is almost certain that this aberrant expression of ezrin can be explained partly by a corresponding alteration on the mRNA level, as shown by real-time RT-PCR. Whether the reduced mRNA level in ESCC is owing to a decrease in the copy number of the gene or the upstream promoter region modulating ezrin transcription merits further studies.
Ezrin downregulation in tumor cells may have a significant role in tumorigenesis. Ezrin has been found to participate in the CD95-mediated apoptosis (Parlato et al. 2000 In conclusion, the redistribution of ezrin and reduced expression of ezrin both at mRNA and protein levels in ESCC suggest that the different ezrin staining patterns may be useful for the diagnosis of ESCC, and ezrin may play a suppressive role in the transformation and development of ESCC. Additional studies on a larger series of ESCC samples are warranted to confirm these findings, and further investigations are required to elucidate the mechanisms of translocation and downregulation of ezrin in ESCC.
This work was supported by the National Natural Science Foundation of China (No. 39900069, No. 30170428, No. 30370641, No. 30570849) and Guangdong Scientific Fund Key Items (No. 37788, No. 05104541). We thank DaAn Gene Co., Ltd. of Sun Yat-sen University for their kind assistance in real-time RT-PCR and Lijun Tan and Dawn Harp, University of Michigan, for their help in reviewing the paper. We thank Professor MingYao Wu, Department of Pathology, Medical College of Shantou University for his kind help in pathological image analysis.
1 These authors contributed equally to this work. Received for publication November 14, 2005; accepted March 10, 2006
Autero M, Heiska L, Ronnstrand L, Vaheri A, Gahmberg CG, Carpen O (2003) Ezrin is a substrate for Lck in T cells. FEBS Lett 535:8286[CrossRef][Medline] Bretscher A, Edwards K, Fehon RG (2002) ERM proteins and merlin: integrators at the cell cortex. Nat Rev Mol Cell Biol 3:586599[CrossRef][Medline] Bretscher A, Reczek D, Berryman M (1997) Ezrin: a protein requiring conformational activation to link microfilaments to the plasma membrane in the assembly of cell surface structures. J Cell Sci 110:30113018[Abstract] Elliott BE, Meens JA, SenGupta SK, Louvard D, Arpin M (2005) The membrane cytoskeletal crosslinker ezrin is required for metastasis of breast carcinoma cells. Breast Cancer Res 7:R365373[CrossRef][Medline] Gautreau A, Louvard D, Arpin M (2002) ERM proteins and NF2 tumor suppressor: the Yin and Yang of cortical actin organization and cell growth signaling. Curr Opin Cell Biol 14:104109[CrossRef][Medline] Geiger KD, Stoldt P, Schlote W, Derouiche A (2000) Ezrin immunoreactivity is associated with increasing malignancy of astrocytic tumors but is absent in oligodendrogliomas. Am J Pathol 157:17851793 Guan XQ, Wang CJ, Li YY (2002) Effects of ezrin on differentiation and adhesion of hepatocellular carcinoma. Ai Zheng 21:281284[Medline] Hiscox S, Jiang WG (1999) Ezrin regulates cell-cell and cell-matrix adhesion, a possible role with E-cadherin/ß-catenin. J Cell Sci 112:30813090[Abstract] Huang T, You Y, Spoor MS, Richer EJ, Kudva VV, Paige RC, Seiler MP, et al. (2003) Foxj1 is required for apical localization of ezrin in airway epithelial cells. J Cell Sci 116:49354945 Hunter KW (2004) Ezrin, a key component in tumor metastasis. Trends Mol Med 10:201204[CrossRef][Medline] Ilmonen S, Vaheri A, Asko-Seljavaara S, Carpen O (2005) Ezrin in primary cutaneous melanoma. Mod Pathol 18:503510[CrossRef][Medline] Khanna C, Wan X, Bose S, Cassaday R, Olomu O, Mendoza A, Yeung C, et al. (2004) The membrane-cytoskeleton linker ezrin is necessary for osteosarcoma metastasis. Nat Med 10:182186[CrossRef][Medline] Kimos MC, Wang S, Borkowski A, Yang GY, Yang CS, Perry K, Olaru A, et al. (2004) Esophagin and proliferating cell nuclear antigen (PCNA) are biomarkers of human esophageal neoplastic progression. Int J Cancer 111:415417[CrossRef][Medline] Louvet-Vallée S (2000) ERM proteins: from cellular architecture to cell signaling. Biol Cell 92:305316[CrossRef][Medline] Lozupone F, Lugini L, Matarrese P, Luciani F, Federici C, Iessi E, Margutti P, et al. (2004) Identification and relevance of the CD95-binding domain in the N-terminal region of ezrin. J Biol Chem 279:91999207 Moilanen J, Lassus H, Leminen A, Vaheri A, Butzow R, Carpen O (2003) Ezrin immunoreactivity in relation to survival in serous ovarian carcinoma patients. Gynecol Oncol 90:273281[CrossRef][Medline] Parlato S, Giammarioli AM, Logozzi M, Lozupone F, Matarrese P, Luciani F, Falchi M, et al. (2000) CD95 (APO-1/Fas) linkage to the actin cytoskeleton through ezrin in human T lymphocytes: a novel regulatory mechanism of the CD95 apoptotic pathway. EMBO J 19:51235134[CrossRef][Medline] Roy C, Martin M, Mangeat P (1997) A dual involvement of the amino-terminal domain of ezrin in F- and G-actin binding. J Biol Chem 272:2008820095 Saotome I, Curto M, McClatchey AI (2004) Ezrin is essential for epithelial organization and villus morphogenesis in the developing intestine. Dev Cell 6:855864[CrossRef][Medline] Shen ZY, Chen MH, Shen J, Cai WJ, Zeng Y (2002) Progressive transformation of immortalized esophageal epithelial cells. World J Gastroenterol 8:976981[Medline] Shen ZY, Xu LY, Chen MH, Li EM, Li JT, Wu XY, Zeng Y (2003) Upregulated expression of ezrin and invasive phenotype in malignantly transformed esophageal epithelial cells. World J Gastroenterol 9:11821186[Medline] Srivastava J, Elliott BE, Louvard D, Arpin M (2005) Src-dependent ezrin phosphorylation in adhesion-mediated signaling. Mol Biol Cell 16:14811490 Tokunou M, Niki T, Saitoh Y, Imamura H, Sakamoto M, Hirohashi S (2000) Altered expression of the ERM proteins in lung adenocarcinoma. Lab Invest 80:16431650[Medline] Turunen O, Wahlstrom T, Vaheri A (1994) Ezrin has a COOH-terminal actin-binding site that is conserved in the ezrin protein family. J Cell Biol 126:14451453 Tynninen O, Carpen O, Jaaskelainen J, Paavonen T, Paetau A (2004) Ezrin expression in tissue microarray of primary and recurrent gliomas. Neuropathol Appl Neurobiol 30:472477[CrossRef][Medline] Weng WH, Ahlen J, Astrom K, Lui WO, Larsson C (2005) Prognostic impact of immunohistochemical expression of ezrin in highly malignant soft tissue sarcomas. Clin Cancer Res 11:61986204 Yang HS, Hinds PW (2003) Increased ezrin expression and activation by CDK5 coincident with acquisition of the senescent phenotype. Mol Cell 11:11631176[CrossRef][Medline] Yu Y, Khan J, Khanna C, Helman L, Meltzer PS, Merlino G (2004) Expression profiling identifies the cytoskeletal organizer ezrin and the developmental homeoprotein Six-1 as key metastatic regulators. Nat Med 10:175181[CrossRef][Medline]
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||