CXorf61 is a target for T cell based immunotherapy of triple-negative breast cancer

// Claudia Paret 1 , Petra Simon 2 , Kirsten Vormbrock 1 , Christian Bender 1 , Anne Kölsch 1 , Andrea Breitkreuz 2 , Özlem Yildiz 2 , Tana Omokoko 2 , Stefanie Hubich-Rau 3 , Christoph Hartmann 1, 3 , Sabine Häcker 1 , Meike Wagner 1, 3 , Diana Barea Roldan 3 , Abderaouf Selmi 1 , Özlem Türeci 1, * , Ugur Sahin 1, 2, 3, * 1 TRON gGmbH, Translational Oncology at the University Medical Center, Johannes Gutenberg-University Mainz, Germany 2 BioNTech Cell & Gene Therapies, An der Goldgrube 12, Mainz, Germany 3 Experimental Oncology, Dpt. of Medicine III, Johannes Gutenberg-University, Mainz, Germany * These authors have contributed equally to this work Correspondence to: Ugur Sahin, e-mail: ugur.sahin@tron-mainz.de Keywords: TNBC, CXorf61, CD8+ T cell epitope, T-cell receptor cloning, immunotherapy Received: May 24, 2015      Accepted: July 15, 2015      Published: July 29, 2015 ABSTRACT Triple-negative breast cancer (TNBC) is a high medical need disease with limited treatment options. CD8+ T cell-mediated immunotherapy may represent an attractive approach to address TNBC. The objectives of this study were to assess the expression of CXorf61 in TNBCs and healthy tissues and to evaluate its capability to induce T cell responses. We show by transcriptional profiling of a broad comprehensive set of normal human tissue that CXorf61 expression is strictly restricted to testis. 53% of TNBC patients express this antigen in at least 30% of their tumor cells. In CXorf61-negative breast cancer cell lines CXorf61 expression is activated by treatment with the hypomethylating agent 5-aza-2′-deoxycytidine. By vaccination of HLA-A*02-transgenic mice with CXorf61 encoding RNA we obtained high frequencies of CXorf61-specific T cells. Cloning and characterization of T cell receptors (TCRs) from responding T cells resulted in the identification of the two HLA-A*0201-restricted T cell epitopes CXorf61 66–74 and CXorf61 79–87 . Furthermore, by in vitro priming of human CD8+ T cells derived from a healthy donor recognizing CXorf61 66–74 we were able to induce a strong antigen-specific immune response and clone a human TCR recognizing this epitope. In summary, our data confirms this antigen as promising target for T cell based therapies.