BACKGROUND: While cyclooxygenase-2 (COX-2) is not normally expressed by epithelial cells lining the human colon, COX-2 protein is aberrantly overexpressed in premalignant adenomatous polyps and carcinomas of the human colon. On the other hand, Cdx2 has been identified as a colonic tumor-suppressor gene, besides its role in cell differentiation. However, the relationship between CDX2 attenuation and COX-2 overexpression in colorectal carcinoma has not been established. Here, we investigated the mechanistic link between CDX2 downregulation and COX-2 upregulation. METHODS: Gene expression was examined by immunoblotting, reverse transcription-polymerase chain reaction, and promoter analysis. Promoter transactivation was quantified by using a luciferase construct. DNA binding of nuclear factor-kappaB (NF-kappaB) was examined by electromobility shift analysis. RESULTS: CDX2 decreased expression of COX-2 mRNA and protein at the transcriptional level in the human colon cancer Caco-2 cell line. Though p50/p65 NF-kappaB translocated into nucleus in the presence of CDX2, CDX2 interacted with p50/p65 NF-kappaB and impeded the formation of an NF-kappaB-DNA complex, required for promotion of Cox-2 transcription. CONCLUSION: The results indicate that CDX2 inhibits transcription of Cox-2 by interfering with the binding of NF-kappaB on the NF-kappaB binding site.
BACKGROUND: While cyclooxygenase-2 (COX-2) is not normally expressed by epithelial cells lining the human colon, COX-2 protein is aberrantly overexpressed in premalignant adenomatous polyps and carcinomas of the human colon. On the other hand, Cdx2 has been identified as a colonic tumor-suppressor gene, besides its role in cell differentiation. However, the relationship between CDX2 attenuation and COX-2 overexpression in colorectal carcinoma has not been established. Here, we investigated the mechanistic link between CDX2 downregulation and COX-2 upregulation. METHODS: Gene expression was examined by immunoblotting, reverse transcription-polymerase chain reaction, and promoter analysis. Promoter transactivation was quantified by using a luciferase construct. DNA binding of nuclear factor-kappaB (NF-kappaB) was examined by electromobility shift analysis. RESULTS:CDX2 decreased expression of COX-2 mRNA and protein at the transcriptional level in the humancolon cancer Caco-2 cell line. Though p50/p65 NF-kappaB translocated into nucleus in the presence of CDX2, CDX2 interacted with p50/p65 NF-kappaB and impeded the formation of an NF-kappaB-DNA complex, required for promotion of Cox-2 transcription. CONCLUSION: The results indicate that CDX2 inhibits transcription of Cox-2 by interfering with the binding of NF-kappaB on the NF-kappaB binding site.
Authors: G V Mallo; P Soubeyran; J C Lissitzky; F André; C Farnarier; J Marvaldi; J C Dagorn; J L Iovanna Journal: J Biol Chem Date: 1998-05-29 Impact factor: 5.157
Authors: Y Beazer-Barclay; D B Levy; A R Moser; W F Dove; S R Hamilton; B Vogelstein; K W Kinzler Journal: Carcinogenesis Date: 1996-08 Impact factor: 4.944
Authors: Jianping Kong; Hong Sai; Mary Ann S Crissey; Nirag Jhala; Gary W Falk; Gregory G Ginsberg; Julian A Abrams; Hiroshi Nakagawa; Kenneth Wang; Anil K Rustgi; Timothy C Wang; John P Lynch Journal: Oncotarget Date: 2015-10-20