Proteolysis-Targeting Chimeras Enhance T Cell Bispecific Antibody-Driven T Cell Activation and Effector Function through Increased MHC Class I Antigen Presentation in Cancer Cells
Vittoria Massafra, Sofia Tundo, Aline Dietzig, Axel Ducret, Christian Jost, Christian Klein, Roland E. Kontermann, Hendrik Knoetgen, Martin Steegmaier, Andrea Romagnani and Yvonne A. Nagel
The availability of Ags on the surface of tumor cells is crucial for the efficacy of cancer immunotherapeutic approaches using large molecules, such as T cell bispecific Abs (TCBs). Tumor Ags are processed through intracellular proteasomal protein degradation and are displayed as peptides on MHC class I (MHC I). Ag recognition through TCRs on the surface of CD8+ T cells can elicit a tumor-selective immune response. In this article, we show that proteolysis-targeting chimeras (PROTACs) that target bromo- and extraterminal domain proteins increase the abundance of the corresponding target-derived peptide Ags on MHC I in both liquid and solid tumor–derived human cell lines. This increase depends on the engagement of the E3 ligase to bromo- and extraterminal domain protein. Similarly, targeting of a doxycycline-inducible Wilms tumor 1 (WT1)-FKBP12F36V fusion protein, by a mutant-selective FKBP12F36V degrader, increases the presentation of WT1 Ags in human breast cancer cells. T cell–mediated response directed against cancer cells was tested on treatment with a TCR-like TCB, which was able to bridge human T cells to a WT1 peptide displayed on MHC I. FKBP12F36V degrader treatment increased the expression of early and late activation markers (CD69, CD25) in T cells; the secretion of granzyme β, IFN-γ, and TNF-α; and cancer cell killing in a tumor-T cell coculture model. This study supports harnessing targeted protein degradation in tumor cells, for modulation of T cell effector function, by investigating for the first time, to our knowledge, the potential of combining a degrader and a TCB in a cancer immunotherapy setting.