T-cell Enriching Therapy using combination of IL-12 gene electrotransfer and anti-PD-1 attenuates the resistance of anti-PD1 in preclinical metastatic cancer

Abstract

Abstract Immune checkpoint blockades, such as anti-PD-1, have demonstrated significant clinical benefits. However, both primary and acquired resistance has become major obstacles. Limited immune cell infiltration into tumors and expression of PD-1 are two reasons leading to resistance to PD-1 inhibition. Our laboratory has demonstrated that expression of plasmid IL-12 delivered intraumorally can increase immune cell infiltration as well as potentially increase levels of PD-1. In this current study, we used the intraperitoneal metastatic B16F10 tumor model and report that IL-12 gene electrotransfer (IL-12 GET) combined with anti-PD-1 induced long-lived CD8+PD-1− T cells. Strikingly, the effector cytolytic activity of CTLs was expanded and maintained for up to 60 days, indicating that these cells do not differentiate into a memory functional phenotype. In vivo imaging results, illuminate a lower flux signal in B16.F10 intraperitoneal metastases following the combination treatment. Simultaneously, the primary subcutaneous tumors are fully regressed in most of these mice (80%). Expression of CD44+ CD62L− on CD8 CTLs increased with time, suggesting that the memory response was induced at around 120 days. Depletion experiments revealed that CD8+ T cells and CD4+ T cells were required for tumor regression. Our results revealed that this treatment not only boosted CD3+ T-cell infiltration into tumor mass but also upregulated the production of proinflammatory cytokines such as IFN-γ as well as chemokines CXCL9, CXCL10 and CXCL11, promoting accumulation of T cells to the tumor microenvironment and enhancing the effector functions of infiltrated T cells and simultaneously, attenuate the resistant of immune checkpoint blockade of anti-PD1.