Anti-CEACAM5 monoclonal antibody, clone DMC-hsbo/21, JI5Gd

Carcinoembryonic antigen (CEA, ceacam5) is an important tumor-associated antigen with reported roles, e.g., in immunological defense, cell adhesion, cell survival and metastasis. Its overexpression in cancer cells is known to involve transcriptional activation of the CEA gene, but the underlying molecular details remain unclear. Here, we show that hypoxia and intracellular alkalinization, 2 factors commonly found in solid tumors, increase CEA protein expression in breast (MCF-7) and colorectal (CaCo-2 and HT-29) cancer cells. The increase was comparable (2-3-fold) to that observed in colorectal carcinomas in vivo. CEA promoter analyses further revealed that this upregulation involves a known binding site for HIF-1 transcription factor (5'-ACGTG-3') within one of the CEA promoter's positive regulatory elements (the FP1 site; the E-box). Accordingly, deletion or targeted mutagenesis of this motif rendered the CEA promoter unresponsive to hypoxia. Our chromatin immunoprecipitation data confirmed that endogenous HIF-1 alpha binds to the CEA promoter in hypoxic cells but not in normoxic cells. Moreover, overexpression of the hypoxia-inducible factor (HIF-1a) was sufficient to increase CEA protein expression in the cells. In contrast, c-Myc, which is known to bind to the overlapping E-box, did not potentiate HIF-1 alpha-induced CEA expression. CEA overexpression in vivo was also found to coincide with the expression of carbonic anhydrase IX, a well-known hypoxia marker. Collectively, these results define CEA as a hypoxia-inducible protein and suggest an important role for the tumor microenvironmental factors in CEA overexpression during tumorigenesis. (C) 2007 Wiley-Liss, Inc.

Background: CEACAM1, CEACAM5, and CEACAM6 represent 3 of the CEACAM (carcinoembryonic antigen-related cell adhesion molecule) subfamily members expressed on intestinal epithelial cells (IECs). Deficiency in their expression, as seen in inflammatory bowel disease (1131)), results in the lack of activation of CD8+ regulatory T cells in the mucosa. Since CEACAM expression was shown to be regulated by the transcription factor SOX9, we sought to determine whether the defect in CEACAM expression in IBD was related to aberrant SOX9 expression. Methods: IECs and lamina propria lymphocytes (LPLs) were freshly isolated from colonic tissues. T84 and HT29 16E cells were cocultured with LPLs. SOX9 and CEACAM subfamily member expression was assessed by real-time polymerase chain reaction (PCR), Western blot, immunohistochemistry, and immunofluorescence. Results: In Crohn's disease (CD) but not in ulcerative colitis (UC), a significant reduction in mRNA and protein expression for CEACAM1 and 5 was noted; in contrast, no difference in SOX9 mRNA expression was seen. However, nuclear SOX9 immunostaining was increased in CD IECs. Furthermore, SOX9 protein was reduced in the cytoplasm of LPL-stimulated T84 and HT29 16E cells, while CEACAM5 expression was increased. Conclusions: The defect in CEACAM family members in CD IECs appears to be related to the aberrant nuclear localization of SOX9. Changes in SOX9 expression in the CD mucosa relate to the local microenvironment and altered IEC:LPL crosstalk.