Development of a curative therapeutic vaccine (TheraVac) for the treatment of large established tumors

Abstract

Harnessing immune system to treat cancer requires simultaneous generation of tumor-specific CTLs and curtailment of tumor immunosuppressive environment. Here, we developed an immunotherapeutic regimen capable of eliminating large established mouse tumors using HMGN1, a DC-activating TLR4 agonist capable of inducing anti-tumor immunity. Intratumoral delivery of HMGN1 with low dose of Cytoxan that acts as a functional checkpoint inhibitor cured mice bearing small (diameter ~ 0.5 cm), but not large (diameter ~ 1.0 cm) CT26 tumors. Screening for activators capable of synergizing with HMGN1 in activating DC identified R848. Intratumoral delivery of HMGN1 and R848 plus Cytoxan eradicated large established CT26 tumors. The resultant tumor-free mice were resistant to subsequent challenge with CT26, indicating the generation of CT26-specific protective immunity. This immunotherapeutic regimen caused homing of tumor-infiltrating DC to draining lymph nodes and increased infiltration of T cells into tumor tissues. Cytoxan in this regimen could be replaced by anti-CTLA4) or anti-PD-L1. Importantly, this immunotherapeutic regimen was also curative for large established mouse Renca and EG7 tumors. Thus, we have developed a curative therapeutic vaccination regimen dubbed ‘TheraVac’ consisting of HMGN1 and R848 plus a checkpoint inhibitor, that can, without using exogenous tumor-associated antigen(s), eliminate various large tumors and induce tumor-specific immunity.