Overexpression of HOMER2 predicts better outcome in low-grade endometrioid endometrial adenocarcinoma

We have previously shown that HOMER2 (Homer scaffolding protein 2), a protein coding gene, was highly expressed in low grade (LG) endometrioid adenocarcinoma (EAC) of the uterus. The role of HOMER2 in endometrial cancer (EC) is widely unknown; therefore, the aim of this study was to determine the expression and the predictive value of HOMER2 protein expression in series of patients with EC. HOMER2 protein expression was detected on paraffin-embedded tissues from 336 cases using immunohistochemistry (IHC). Tumours were categorised in two groups; group 1 (EAC, FIGO grade 1 and 2; n = 191) and group 2 (all other subtypes including grade 3 EAC; n = 145). Statistical analysis was performed to evaluate associations between HOMER2 protein expression and pathological parameters (histological type, grade, stage, lymphovascular invasion, myometrial depth of invasion) and patient outcome [progression-free survival (PFS) and cancer-specific survival (CSS)]. HOMER2 was significantly overexpressed in group 1 compared to group 2 cancers (67% versus 30%; p < 0.001) and with low tumour grade (p < 0.001). In group 1, HOMER2 overexpression was an independent prognostic factor for improved CSS (adjusted-hazard ratio 0.28; 95% confidence interval 0.08-0.96; p = 0.042). HOMER2 expression was not associated with survival in group 2 (p > 0.05). This is the first study of HOMER2 protein expression in EC. We speculate that HOMER2 may be involved in tumourigenesis of endometrioid uterine tumours and suggest that HOMER2 should be studied further for potential clinical and therapeutic applications.