Enhanced cytotoxic CD8+ T cell (CTL) antigen recognition by LCK activation

Abstract

Abstract The anti-tumor response of cytotoxic T cells requires detection of tumor-derived antigenic peptide-MHC complex (pMHC) by the T cell antigen receptor (TCR). Strategies that boost TCR signaling caused by weak pMHC could augment the recognition of poorly immunogenic tumors by T cells. Because LCK kinase phosphorylates the TCR complex and the recruited ZAP-70 kinase, increased LCK activity has been shown to increase TCR signaling in naïve T cells. Our previous study demonstrated that a small molecule inhibitor of CSK kinase, a negative regulator of LCK, increased LCK kinase activity and sensitized naïve T cells such that they became activated by weak antigens ex vivo. Our goal was to determine whether CD8+ cytotoxic T cells (CTL) could also be sensitized to detect weak antigens, and evaluate whether their capacity to recognize and kill cancer cells could be augmented. Because the Nur77-GFP reporter system responds to TCR-mediated signaling, we used it to determine that LCK activation sensitized OT-1 TCR transgenic CTLs to detect weak (low affinity) antigens displayed by splenocytes. We also observed increased phosphorylation of ZAP-70 and other signaling mediators upon TCR stimulation. We will next evaluate whether CTL-mediated effector functions can be enhanced by monitoring killing of MC38 cancer cells that display a weak antigen. Our findings will inform whether LCK kinase can be targeted to improve the recognition of cancer by T cells.