T cell recognition of breast cancer antigens

Recent studies are encouraging research of breast cancer immunogenicity to evaluate the applicability ofimmunotherapy as a treatment strategy. The epitope landscape in breast cancer is minimally described, thus it is necessary to identify T cell targets to develop immune mediated therapies.This project investigates four proteins commonly upregulated in breast cancer and thus probable tumor associated antigens (TAAs). Aromatase, prolactin, NEK3, and PIAS3 contribute to increase growth, survival, and motility of malignant cells. Aspiring to uncover novel epitopes for cytotoxic T cells, a reverse immunology approach is applied. Via in silico screening of the protein sequences, 415 peptides were predicted as HLA-A*0201 and HLA-B*0702 binders. Subsequent in vitro binding analysis in a MHC ELISA platform confirmed binding for 147 of the 415 predicted binders. The 147 peptides were evaluated for T cell recognition utilizing DNA barcode labeled MHC multimers to screen peripheral blood lymphocytes from breast cancer patients and healthy donor samples. Signif-icantly more TAA specific T cell responses were detected in breast cancer patients than healthy donors for both HLA-A*0201 (P < 0.0039) and HLA-B*0702 (P < 0.001) restricted peptides. Importantly, several of the identified responses were toward peptides that were predicted as poor or intermediate affinity binders. This is indicative of the importance of inclusion these in the search for epitopes within shared TAAs.Thus, the inspected proteins indeed contain targets for T cell reactivity. Further research will include functional testing of peptide specific T cell cultures to validate the peptides as true T cell epitopes through demonstration of intracellular processing and presentation at the cell surface.