Increasing expression of hypoxia-inducible proteins in the Barrett's metaplasia-dysplasia-adenocarcinoma sequence

Abstract

Hypoxia-associated markers are involved in the progression of several malignancies, but are relatively unstudied in Barrett's carcinogenesis. Our aim was to assess the immunohistochemical expression of hypoxia-inducible factor (HIF)-1alpha, HIF-2alpha, erythropoietin (Epo), Epo receptor (Epo-R), Glut-1 and vascular endothelial growth factor (VEGF) along with Ki67/MIB-1 in the Barrett's metaplasia-dysplasia-adenocarcinoma sequence. Endoscopic biopsies of normal squamous epithelium (NSE) (n=20), columnar-lined oesophagus (CLO) (n=15), CLO with intestinal metaplasia (n=20), dysplasia (n=17) and Barrett's type adenocarcinoma (n=20) were obtained. Immunohistochemistry was performed on the paraffin-embedded tissue. A score was calculated for each marker (range 0-300) by multiplying intensity (none 0, weak 1, moderate 2, strong 3) by percentage of expression (range 0-100). Significant increases in the expression of HIF-2alpha (P=0.014), VEGF (P<0.0001), Epo-R (P<0.0001) and Ki67 (P<0.0001) were found as tissue progressed from NSE to adenocarcinoma. HIF-2alpha was expressed late in the sequence and was only seen in dysplasia and adenocarcinoma. High HIF-2alpha expression was seen in 12 out of 20 Barrett's type adenocarcinoma. The late expression of HIF-2alpha in the Barrett's carcinogenesis sequence and its high expression in adenocarcinoma suggest that it is worth further investigation as a marker of disease progression and therapeutic target.

Figure 1

Representative photomicrographs of HIF-1α, HIF-2α, Epo and Epo-R in Barrett's metaplasia–dysplasia–adenocarcinoma sequence. NSE=normal squamous epithelium; CLO=columnar-lined oesophagus; IM, intestinal metaplasia; Dys=dysplasia; Adeno=adenocarcinoma.

Figure 2

Box and whisker plots of each immunohistochemical marker in the Barrett's sequence. The box represents the 25–75 quartile with a median line. The whiskers extend to minimum and maximum values, but exclude outlying and far out values. Individual data points are also shown. NSE=normal squamous epithelium; NCM=normal gastric cardia mucosa; CLO=columnar-lined oesophagus; IM=intestinal metaplasia; Dys=dysplasia; Adeno=adenocarcinoma.

Figure 3

Comparison of the expression of HIF-2α, VEGF, Ki67 and Epo-R in normal squamous epithelium compared with adjacent columnar-lined oesophagus (CLO), intestinal metaplasia (IM), dysplasia (Dys) and adenocarcinoma (Adeno). A total of 40 biopsies were studied.