Differential expression of Hox A5 in human colon cancer cell differentiation: a quantitative study using real-time RT-PCR

Fifteen different homeobox genes were identified from normal colon mucosa, untreated COLO 205 and herbimycin A treated COLO 205 cells in a degenerate primer RT-PCR screen. Several of the homeobox genes, including Cdx-1, Cdx-2 , Pdx-1 and Hox A5, showed a trend toward differential expression in normal colon mucosa, and undifferentiated COLO 205 cells. Hox AS was recently sho wn to suppress growth and induce p53-dependent apoptosis. To determine if H ox A5 was differentially expressed in differentiation of colon epithelial c ells, we quantified Hox AS expression by real-time quantitative RT-PCR. Exp ression of Hox AS was 5.3- and 4.8-fold higher in normal colon mucosa compa red to COLO 205 and HT-29 cells, respectively, suggesting that Hox AS expre ssion was higher in differentiated compared to undifferentiated colon epith elial cells. To avoid the complexity of tissue specimens and the influence of individual variation in Hox AS expression, the effect of differentiation on Hox A5 expression was studied in COLO 205 cells treated with herbimycin A. The quantitative study showed that Hox A5 expression was increased when COLO 205 cells were induced to differentiate. The expression of Hox A5 was about 2-fold higher in the cells treated for 48 h compared to the untreate d poorly-differentiated cells. The present study shows that Hox AS may be i nvolved in intestinal cell differentiation, in addition to its role in apop tosis.