Up-regulation of ERM/ETV5 correlates with the degree of myometrial infiltration in endometrioid endometrial carcinoma

Abstract

To elucidate alterations in gene expression in endometrioid endometrial carcinoma (EEC), differential gene expression profiling was previously described in both tumour and non-tumour contexts, and the up-regulation of the RUNX1/AML1 proto-oncogene in EEC was characterized. Among the set of genes found to be up-regulated significantly in EEC, the most relevant, ERM/ETV5, corresponds to the PEA3 subfamily and is a member of the Ets family of transcription factors that contain the Ets DNA-binding domain and are involved in matrix remodelling. In the present work, an attempt was made to characterize the expression of ERM/ETV5 in EEC throughout the process of tumourigenesis. Gene expression levels of ERM/ETV5 were quantified by real-time quantitative PCR (RT-Q-PCR) using a large panel of samples ranging from non-invasive IA to metastatic IIIA stages, and protein expression was characterized by tissue array immunohistochemistry (TMA). RT-Q-PCR validated ERM/ETV5 up-regulation in EEC and demonstrated a specific and significant increase restricted to those tumour stages associated with myometrial invasion. TMA showed that ERM/ETV5 up-regulation correlated mainly with the transition from atrophic endometrium to hyperplasia and carcinoma during tumour progression. Furthermore, ERM/ETV5 gene and protein expression levels were associated with low tumour grade. Finally, ERM/ETV5 up-regulation correlated with that of RUNX1/AML1. All of these results lead to the proposal of a co-operative role between ERM/ETV5 and RUNX1/AML1 during the early events of endometrial tumourigenesis, which may be associated with a switch to myometrial infiltration.