Regulation of gene expression in inflammatory bowel disease and correlation with IBD drugs. Screening by DNA microarrays

Potential biomarkers for Crohn's disease (CD) and ulcerative colitis (UC) were identified from two sets of full thickness pathologic samples utilizing DermArray® and PharmArray® DNA microarrays relative to uninvolved (Un) colon or normal colon. Seven of the over‐expressed genes were verified using quantitative RT‐PCR (i.e., TMPT, FABP1, IFI27, LCN2, COL11A2, HXB, and metallothionein). By correlating gene expression profiles between inflammatory bowel disease (IBD) tissue samples and IBD drug‐treated cell cultures it might be possible to identify new candidate molecular target genes for IBD therapy and drug discovery. Potential biomarkers for CaCo2 cell cultures, which are routinely used as a GI tract surrogate model for in vitro pharmacokinetic studies, treated with azathioprine, 5‐aminosalicylic acid, metronidazole, and prednisone were also identified from another experiment. Metallothionein mRNA expression was found to be down‐regulated in azathioprine‐treated CaCo2 cells, and was coincidentally up‐regulated in the CD sample, thus resulting in an anti‐correlation. These results suggest that this new screening methodology is feasible, that metallothioneins might be biomarkers for azathioprine therapy in vivo in CD, and that azathioprine might mechanistically down‐regulate metallothionein gene expression. Correlations were also observed between IBD samples and either metronidazole‐ or 5‐aminosalicylic acid‐treated CaCo2 cells. Similar comparisons of disease tissue samples in vivo vs drug‐treated cell cultures in vitro might reveal new mechanistic insights concerning established or experimental drug therapies. This affordable in vitro methodology is promising for expanded studies of IBD and other diseases.