Abstract
Background: Ovarian cancer remains the most lethal gynaecologic tumour in the Western world. Stimulation of the immune system to consolidate response to chemotherapy can potentially be beneficial however so far none of the vaccination strategies have offered survival advantage. Thus identifying and targeting clinically relevant antigens for immunotherapy continues to be an important research strategy. We have evaluated Engrailed-2 (EN2) as a potential target for vaccine strategy. EN2 is a homeodomain-containing transcription factor with a multifunctional role in neural development. There is evidence that over-expression of EN2 protein maybe linked to tumour development. Methods: Ovarian cancer cell lines were analysed by FACS for EN2 cell surface expression. EN2 expression in ovarian cancer tissue arrays were done by immunohistochemistry. A serum analysis (ELISA) was done to evaluate the presence of antibodies to EN2 in ovarian cancer patients and age-matched controls. A set of potentially immunogenic HLA-A2 restricted epitopes from the EN2 protein was identified using a computer algorithm SYFPEITHI. These peptides have been tested on HLA-A2 positive ovarian cancer patients’ PBMC using an in vitro culture method. The specificity of these T cell lines was analysed against T2 target cells loaded with or without EN2 peptides Results: Cell surface expression of EN2 was observed in ovarian cancer cell lines OVCAR3, OV90, CaOV-3, ES-2 and SKOV-3 of which ES-2 and SKOV3 showed strong expression. EN2 was also present in approximately 80% of ovarian cancer tissues whereas EN-2 expression was very low (<10%) or absent in normal tissues. Out of the 67 ovarian cancer patients 20.9% (14/67) had antibodies against EN2 compared to 2.4% (1/42) of age-matched female controls. 4 of the identified EN2 epitopes were able to generate peptide specific cytotoxic T lymphocytes in the ovarian cancer patients tested. Conclusions: The over-expression and immunogenicity of EN2 in ovarian cancer makes it a credible antigen to exploit as a novel target for ovarian cancer immunotherapy. ž