Oestrogen receptor beta expression and depth of myometrial invasion in human endometrial cancer

We assessed the relative expression of oestrogen receptor (ER)alpha and oestrogen receptor (ER)beta mRNAs in 36 human endometrial cancers using a multiplex polymerase chain reaction (PCR). To determine whether or not the expression of ER subtypes in endometrial cancers is associated with clinicopathological parameters, we examined correlations between ER subtypes and age, tumour grade and depth of myometrial invasion. Using multiple regression analysis, myometrial invasion showed a significant correlation with ER-beta: ER-alpha ratio (r = 0.54, P = 0.0007). The ER-beta:ER-alpha ratio was high in advanced invasive carcinoma. Western blotting analysis showed that ER-beta proteins were highly expressed in comparison with ER-alpha proteins in endometrial cancer with severe myometrial invasion. Our results suggest that ER-beta is important in the progression of myometrial invasion.