title: Calreticulin, an endoplasmic reticulum-resident protein, is highly expressed and essential for cell proliferation and migration in oral squamous cell carcinoma.
abstract: OBJECTIVE
  Oral squamous cell carcinoma (OSCC) has emerged as one of the major malignant tumors of the head and neck cancers. However, the molecular mechanism behind tumorigenesis of OSCC is not fully understood. The aim of this study was to investigate the role of calreticulin (CRT), an endoplasmic reticulum-resident protein, in OSCC cells.
  
  
  METHODS
  Sixteen paired samples of tumor and non-cancerous matched tissue (NCMT), six OSCC cell lines and normal human oral keratinocytes (NHOKs), and oral tissue microarray were used to reveal the expression of CRT by Western blotting and immunohistochemistry. Later, shRNA-mediated stable knockdown of CRT in OSCC cells was generated. The knockdown cell line was used to analyze cell proliferation, colony formation, anchorage-independent growth and cell migration in vitro.
  
  
  RESULTS
  CRT was differentially expressed in fresh tumor samples and six OSCC cell lines but not adjacent NCMTs and NHOKs. In oral tissue microarray, we showed that there was positive CRT staining in the vast majority of tumor cases (99/103), in sharp contrast to that in NCMT cases (29/92) (p<0.001). Stable knockdown of CRT in oral cancer cells resulted in significantly reduced growth rate, colony-forming capacity and anchorage-independent growth. This may be attributed to the induction of G0/G1 cell cycle arrest when CRT was depleted in the cells. Both horizontal and vertical movements of the CRT-knockdown stable line were markedly impaired. The phosphorylation levels of focal adhesion kinase (FAK), paxillin and ERK1/2 and the activity of matrix metalloproteinase-2 and -9 (MMP-2 and MMP-9) were decreased in the CRT-knockdown cells. These results suggest that CRT can regulate oral cancer cell migration through activation of the FAK signaling pathway accompanied with proteolytic degradation of the extracellular matrix (ECM) by MMP-2 and MMP-9.
  
  
  CONCLUSIONS
  Together, this study has defined a novel biological role for CRT in oral cancer. CRT is a potential biomarker and may contribute to the malignant phenotypes of OSCC cells.
authors: Department of Oral and Maxillofacial Surgery, Chi-Mei Medical Center, Liouying, Taiwan.
authors: Wei-Fan
authors: WF
authors: Chiang
authors: Tzer-Zen
authors: TZ
authors: Hwang
authors: Tzyh-Chyuan
authors: TC
authors: Hour
authors: Lee-Hsin
authors: LH
authors: Wang
authors: Chien-Chih
authors: CC
authors: Chiu
authors: Hau-Ren
authors: HR
authors: Chen
authors: Yu-Jen
authors: YJ
authors: Wu
authors: Chih-Chun
authors: CC
authors: Wang
authors: Ling-Feng
authors: LF
authors: Wang
authors: Chen-Yu
authors: CY
authors: Chien
authors: Jen-Hao
authors: JH
authors: Chen
authors: Chao-Tien
authors: CT
authors: Hsu
authors: Jeff Yi-Fu
authors: JY
authors: Chen
mesh_terms: D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000378:metabolism*; D037282:Calreticulin / Q000378:metabolism* / Q000502:physiology; D002294:Carcinoma, Squamous Cell / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D017931:DNA Primers; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D009062:Mouth Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D009362:Neoplasm Metastasis; D060888:Real-Time Polymerase Chain Reaction; D046888:Tissue Array Analysis; D015854:Up-Regulation
chemical_list: D014408:Biomarkers, Tumor; D037282:Calreticulin; D017931:DNA Primers; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9