Modulation of presentation and cross-presentation of low affinity cancer neoepitopes by Tapasin 4118

Abstract Description Neoepitopes are generated from tumor-specific mutations and can make tumors potential targets for the immune system. We and others have reported that a significant proportion of neoepitopes which elicit CD8+ T cell mediated tumor control in vivo (such as Ccdc85cMUT in the Meth A sarcoma and PLK1MUT in MC38-FABF colon carcinoma) bind MHC I with low to extremely low affinities (IC50 of 500- 50,000 nM). Tapasin (Tpn) is a critical proofreader in the peptide loading complex and facilitates preferential loading of peptides with a higher affinity for MHC I. Here, we have utilized Tpn-/- Meth A and MC38-FABF tumor cells, Tpn-/- mice, Tpn-neutralizing siRNAs and anti-Tpn antibodies to investigate the role of Tpn in defining the neoepitope repertoire on tumor cells and their cross-presentation by dendritic cells (DC). We have created Tpn-/- Meth A and MC38-FABF cell lines using CRISPR/Cas9 to characterize the quantity of the low affinity Ccdc85cMUT and high affinity PDPRMUT in Meth A and the low affinity PLK1MUT and high affinity JUPMUT in MC38-FABF. By using DC from Tpn+/+ and Tpn-/- mice, we will analyse the role of Tpn in cross-presentation of apoptotic Tpn+/+ or Tpn-/- Meth A or MC38-FABF cells as well as the defined low and high affinity neoepitopes using mass spectrometry and cognate CD8+ T cell stimulation. Finally, the influence of Tpn on immunogenicity of tumor cells shall be studied by examining the kinetics of tumor growth of Tpn+/+ and Tpn-/- tumor cells in Tpn+/+ mice. Funding Sources Neag Cancer Immunology Translational Program Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)