Epidemiological studies show a strong link between
postmenopausal hormone replacement therapy and decreased incidence of
colorectal cancer. The
colon cancer cell line, COLO 205, develops sensitivity to 17beta-oestradiol (E(2)) in apoptosis assays with increasing passage number (>40), and we hypothesised that genes selectively regulated in multiply passaged cells were likely to be important in E(2)-related apoptosis. Gene array analysis was used to compare the patterns of genes up- or down-regulated in E(2)-sensitive and -insensitive cells. For some genes, changes in
mRNA expression were confirmed by
protein expression analyses. Changes found in response to E(2) in multiply passaged cells, but not minimally passaged cells, included induction of
growth arrest and DNA damage-inducible protein 153 (GADD153), and repression of Kirsten-Ras 2B (K-Ras-2B),
metastasis inhibition factor NM23 and
vascular endothelial growth factor. A second group of genes was regulated with E(2) exposure in both cell types, and is unlikely to be critically involved in E(2)-associated apoptosis. These included up-regulation of
butyrate response factor 1 (BRF1) and down-regulation of c-jun and the
breast cancer associated ring domain gene known as BARD1. By comparing control arrays from the two cell populations,
cAMP-response element-binding protein (CBP), which is associated with
steroid receptor-dependent target gene transcription and the
oncoprotein,
tyrosine kinase-T3 (TRK-T3), were up-regulated whereas
retinoic acid receptor alpha (RARalpha) was down-regulated in multiply passaged cells. This study provides evidence for selective regulation of genes in
colon cancer cells by E(2), indicates which of those regulated are likely to be involved in induced apoptosis, and suggests genes likely to be responsible for facilitation.