Homeobox Protein A5 (HOXA5)

HOXA5 was detectable in only one-third of the primary tumors, but in most of the remaining tumors, lack of HOXA5 expression strongly correlated with methylation of its promoter region, suggesting a causal role for methylation in the silencing of HOXA5 gene expression. These results suggested that HOXA5 expression is an important step in tumorigenesis.Cotransfection of a PGR+/ESR1+ or a PGR-/ESR1- breast cancer cell line with HOXA5, but not with HOXB5 or HOXB7, resulted in a 60-fold increase in PGR expression. Cotransfection with HOXB4, an upstream effector of HOXA5, enhanced expression up to 10-fold only in the receptor-negative cell line. Stepwise promoter analysis suggested that HOXA5 binds to a site at the 3-prime end of the PGR promoter region.