Hematopoietic Progenitor Kinase 1 Is a Negative Regulator of Dendritic Cell Activation

Abstract

Hematopoietic progenitor kinase 1 (HPK1) is a hematopoietic cell-restricted member of the Ste20 kinases that acts as a negative regulator of T cell functions through the AP-1, NFAT, and NFκB pathways. Using HPK1-deficient (HPK1−/−) mice, we report in this study a novel role for HPK1 in dendritic cells (DCs). Specifically, we observed that matured HPK1−/− bone marrow-derived DCs (BMDCs) are superior to their wild-type (WT) counterpart in stimulating T cell proliferation in vivo and in vitro. Several characteristics of HPK1−/− BMDCs may account for this enhanced activity: Matured HPK1−/− BMDCs express higher levels of costimulatory molecules CD80, CD86, and I-Ab as well as produce more proinflammatory cytokines IL-12, IL-1β, TNF-α, and IL-6 than their WT littermates. The role of HPK1 as a proapoptotic molecule was assessed post activation with LPS, and results indicated that HPK1−/− BMDCs are significantly resistant to LPS-induced apoptosis. Our results led us to investigate the role of HPK1−/− BMDCs in tumor immunotherapy. Using a s.c. murine model of Lewis Lung Carcinoma, we found that HPK1−/− BMDCs eliminate established s.c. Lewis Lung Carcinoma more efficiently than their WT counterpart. Our data reveal a novel role for HPK1 as a negative regulator of DC functions, identifying its potential as a molecular target for DC-based immunotherapy against cancers.