IL6 and neoplasm: HPK-1 first came to attention as a negative regulator of T cell function, namely the signaling downstream of the TCR through the AP-1, NFAT, and NFκB pathways, and reduces the expression of costimulatory molecules CD80, CD86, I-Ab and proinflammatory cytokines IL-12, IL-1β, TNF-α, and IL-6 on DCs required for effective anti-tumor immunity (84–86).