title: Decreased levels of active SMAD2 correlate with poor prognosis in gastric cancer.
abstract: BACKGROUND
  TGF-β plays a dual role in the progression of human cancer. During the early stages of carcinogenesis, TGF-β functions as a tumor suppressor. During the late stages of tumor development, however, TGF-β can promote tumor growth and metastasis. A shift in Smad2/3 phosphorylation from the carboxy terminus to linker sites is a key event determining biological function of TGF-β in colorectal and hepatocellular carcinoma. In the present study, we investigated the potential role of differential Smad2/3 phosphorylation in gastric adenocarcinoma.
  
  
  METHODS
  Immunohistochemical staining with anti-P-Smad2/3C and P-Smad2/3L antibodies was performed on 130 paraffin-embedded gastric adenocarcinoma specimens. The relationship between P-Smad2/3C and P-Smad2/3L immunohistochemical score and clinicopathologic characteristics of patients was analyzed. Real time PCR was used to measure mRNA expression of Smad2 and Smad3 in cancer and surrounding non-tumor tissue.
  
  
  RESULTS
  No significant P-Smad2L and/or P-Smad3L positive staining was detected in the majority of specimens (positive staining in 18/130 samples). Positive P-Smad2/3L staining was not associated with a decrease in carboxyterminal phosphorylation staining. Loss of P-Smad2C remarkably correlated with depth of tumor infiltration and poor differentiation of cancer cells in patients with gastric cancer. No correlation was detectable between P-Smad3C and clinicopathologic characteristics of gastric adenocarcinoma. However, co-staining analysis revealed that P-Smad3C co-localised with α-SMA and collagen I in gastric cancer cells, indicating a potential link between P-Smad3C and epithelial-to-mesenchymal transition of cancer. Real time PCR demonstrated reduced mRNA expression of Smad2 in gastric cancer when compared with surrounding non-tumor tissue in 15/16 patients.
  
  
  CONCLUSIONS
  Loss of P-Smad2C tightly correlated with cancer invasion and poor differentiation in gastric cancer. Contrary to colorectal and hepatocellular carcinoma, canonical carboxy-terminal phosphorylation, but not linker phosphorylation, of Smad2 is critical for gastric cancer.
authors.affiliation: Department of General Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China. wu1jun@sina.com
authors.forename: Yijun
authors.initials: Y
authors.lastname: Wu
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.forename: Xinhui
authors.initials: X
authors.lastname: Zhou
authors.forename: Jiren
authors.initials: J
authors.lastname: Yu
authors.forename: Yunchuan
authors.initials: Y
authors.lastname: Mu
authors.forename: Stefan
authors.initials: S
authors.lastname: Munker
authors.forename: Chengfu
authors.initials: C
authors.lastname: Xu
authors.forename: Zhe
authors.initials: Z
authors.lastname: Shen
authors.forename: Roman
authors.initials: R
authors.lastname: Müllenbach
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Norbert
authors.initials: N
authors.lastname: Gretz
authors.forename: Derek
authors.initials: D
authors.lastname: Zieker
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Kouichi
authors.initials: K
authors.lastname: Matsuzaki
authors.forename: Youming
authors.initials: Y
authors.lastname: Li
authors.forename: Steven
authors.initials: S
authors.lastname: Dooley
authors.forename: Honglei
authors.initials: H
authors.lastname: Weng
mesh_terms: D000199:Actins / Q000032:analysis / Q000378:metabolism; D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000368:Aged; D024042:Collagen Type I / Q000032:analysis / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D011379:Prognosis; D051899:Smad2 Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D024042:Collagen Type I; D051899:Smad2 Protein; D051900:Smad3 Protein