Carcinogenesis Advance Access published online on November 16, 2007
Carcinogenesis, doi:10.1093/carcin/bgm250
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REG I
Protein Mediates an Anti-apoptotic Effect of STAT3 Signaling in Gastric Cancer Cells

* Department of Surgical and Molecular Pathology, Dokkyo University School of Medicine, Tochigi
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan
Correspondence: Hirokazu Fukui, M.D., Ph.D., Department of Surgical and Molecular, Pathology, Dokkyo University School of Medicine, 880 Kitakobayshi, Mibu, Shimotsuga, Tochigi, 321-0293 Japan., Phone: +81-282-87-2130; FAX: +81-282-86-1681, E-mail: h-fukui{at}dokkyomed.ac.jp
Signal transducer and activator of transcription 3 (STAT3) signaling plays roles in inflammation-associated carcinogenesis. Regenerating gene (REG) I
protein, an interleukin (IL)-6-inducible gene, is suggested to be involved in the gastritis-gastric cancer sequence. We investigated involvement of IL-6/STAT3 signaling in REG I
protein expression, and examined whether REG I
protein mediates an anti-apoptotic effect of STAT3 signaling in gastric cancer cells. The effects of IL-6/STAT3 signaling on REG I
protein expression were examined using a STAT3 small interfering RNA (siRNA) system in gastric cancer cells. The element responsible for IL-6-induced REG I
promoter activation was determined by promoter deletion assay. The anti-apoptotic effects of STAT3 signaling and its induced-REG I
protein were examined by TUNEL and caspase assay in vitro. Human gastric cancer specimens were analyzed by immunohistochemistry for phosphorylated STAT3 (p-STAT3) and REG I
protein. IL-6 treatment enhanced the expression of REG I
protein through STAT3 activation in gastric cancer cells. The IL-6-responsive element was determined to lie in the sequence from –142 to –134 of the REG I
promoter region. REG I
protein mediated the anti-apoptotic effects of STAT3 signaling in gastric cancer cells by enhancing Akt activation, Bad phosphorylation and Bcl-xL expression. The expression of REG I
protein was significantly correlated with that of p-STAT3 in gastric cancer tissues. REG I
protein may play a pivotal role in anti-apoptosis in gastric tumorigenesis under STAT3 activation.
Grant Support: This work was supported in part by Grants-in-aid for Scientific Research 17590635 from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and Grants-in-aid for Research on Measures for Intractable Diseases, and Research on Advanced Medical Technology from the Ministry of Health, Labor, and Welfare, Japan.
Received July 31, 2007; revised October 3, 2007; accepted November 2, 2007.