A novel Biomarker in epithelial ovarian cancer

BACKGROUND: Epithelial ovarian cancer is a common malignancy, with no clinically approved diagnostic biomarker. Engrailed-2 (EN2) is a homeodomain-containing transcription factor, essential during embryological neural development, which is dysregulated in several cancer types. We evaluated the expression of EN2 in Epithelial ovarian cancer, and reviewed its role as a biomarker. METHODS We evaluated 8 Epithelial ovarian cancer cell lines, along with >100 surgical specimens from the Royal Surrey County Hospital (2009-2014). In total, 108 tumours and 5 normal tissue specimens were collected. En2 mRNA was evaluated by semi-quantitative RT-PCR. Histological sub-type, and platinum-sensitive/-resistant status were compared. Protein expression was assessed in cell lines (immunofluorescence), and in >150 tumours (immunohistochemistry). RESULTS En2 mRNA expression was elevated in serous ovarian tumours compared with normal ovary (p<0.001), particularly in high-grade serous ovarian cancer (p<0.0001) and in platinum-resistant tumours (p=0.0232). Median Overall Survival and Progression-free Survival were reduced with high En2 expression (OS=28 vs 42 months, p=0.0329; PFS=8 vs 27 months; p=0.0004). Positive cytoplasmic EN2 staining was demonstrated in 78% of Epithelial ovarian cancers, with absence in normal ovary. EN2 positive high-grade serous ovarian cancer patients had a shorter PFS (10 vs 17.5 months; p=0.0103). CONCLUSION The EN2 transcription factor is a novel ovarian cancer biomarker. It demonstrates prognostic value, correlating with worse Overall Survival and Progression-free Survival. It is hoped that further work will validate its use as a biomarker, and provide insight into the role of EN2 in the development, progression and spread of ovarian cancer.