Tu1134 The Intestinal Transcription Factors Intestine-Specific Homeobox (ISX), Hepatocyte Nuclear Factor 4a (HNF4a) and Caudal-Type Homeobox 2 (CDX2) Are All Expressed in Barrett's Metaplasia

Introduction Barrett’s metaplasia (BM) is the substitution of stratified squamous epithelium with intestinal-type columnar epithelium in the distal oesophagus. It is a condition with malignant potential and yet we do not have any satisfactory treatments to reverse it. The cellular and molecular mechanisms are poorly understood, although several transcription factors are implicated including CDX2. We examined expression of CDX2 along the gastrointestinal tract epithelium, as well as more novel transcription factors ISX and HNF4a. Methods Immunohistochemistry protocols were refined for all three transcription factors for formalin-fixed paraffin-embedded sections of forceps biopsies of human tissue from normal and Barrett’s oesophagus, and from the gastro-oesophageal junction, stomach, small and large bowel. Additionally, the oesophagi of 8 patients were biopsied; 5 with a normal oesophagus and 3 with BM, where biopsies were taken from both the mid-oesophagus and the BM segment. These biopsies were processed for RT-PCR to see whether the immunohistochemistry findings could be confirmed at mRNA level. Results Slide section immunohistochemistry demonstrates that ISX, HNF4a and CDX2 all express nuclear antibody staining in small and large bowel epithelium. ISX and HNF4a are additionally expressed in stomach mucosa epithelium. None of the transcription factors are seen in normal oesophagus aside from very sparse cells with ISX, but all three are demonstrated in BM. RT-PCR of all 3 transcription factors for all 8 patients from normal oesophagus samples was negative. All 3 BM samples were positive for HNF4a, and 2 of the BM samples were positive for ISX and CDX2. However, one BM sample was negative for both ISX and CDX2. Figure legend: Both plates demonstrate nuclear ISX (brown), left = ileum, right = Barrett’s metaplasia. Conclusion CDX2 has been intensively studied in BM, but we also show robust expression of ISX and HNF4a. ISX may be a novel key transcription factor in BM, and our findings suggest that the transcription factor profile in BM echoes that found in intestinal epithelium. Our theory is that HNF4a induction occurs earlier than CDX2 in the genesis of BM; it is possible this is an example of an intermediate stage in this process. Disclosure of Interest None Declared