PLoS ONE (Jan 2012)

Decreased levels of active SMAD2 correlate with poor prognosis in gastric cancer.

  • Yijun Wu,
  • Qi Li,
  • Xinhui Zhou,
  • Jiren Yu,
  • Yunchuan Mu,
  • Stefan Munker,
  • Chengfu Xu,
  • Zhe Shen,
  • Roman Müllenbach,
  • Yan Liu,
  • Li Li,
  • Norbert Gretz,
  • Derek Zieker,
  • Jun Li,
  • Kouichi Matsuzaki,
  • Youming Li,
  • Steven Dooley,
  • Honglei Weng

DOI
https://doi.org/10.1371/journal.pone.0035684
Journal volume & issue
Vol. 7, no. 4
p. e35684

Abstract

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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. METHODOLOGY: 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. PRINCIPAL FINDINGS: 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.