Cancer immunotherapy has become an attractive strategy among different therapeutic modalities over the past few years and has showed great success in the clinic. However, there are many outstanding challenges hindering the current immunotherapies. In my PhD thesis, I aimed to developing bioengineering approaches for engineering innate and adaptive immunity for enhanced cancer immunotherapy. These projects include three major aspects as follows:
Activating cGAS-STING pathway using a manganese-incorporated nanocluster. Targeting the stimulator of interferon genes (STING) pathway with cyclic dinucleotides (CDNs), the natural STING agonists, is a promising immunotherapeutic strategy to boost anticancer immunity. The therapeutic benefits of targeting STING pathway have been demonstrated in many preclinical tumor models. However, the clinical application of natural CDNs as therapeutics is greatly hindered by their intrinsic properties, including negative charges, small molecular weight, and high susceptibility to enzymatic degradation. To overcome these limitations, I developed a manganese-based nanocluster (MnP-PEG) as a new STING agonist. Free manganese ions were released once MnP-PEG nanoclusters were endocytosed, and these ions directly activated the cyclic GMP-AMP synthase (cGAS) and augmented cyclic GMP-AMP (cGAMP)-STING binding affinity. MnP-PEG nanocluster, as a monotherapy or in combination with a checkpoint blockade antibody, resulted in significant tumor regression in the subcutaneous B16F10 murine melanoma model without overt toxicities.
Enhancing T cell function by scavenging potassium ions within the tumor microenvironment. The tumor microenvironment is known to strongly suppress T cells for their anticancer activities. Among various immune-suppressive mechanisms, the elevation of extracellular potassium (K+) ions released by tumor cell necrosis causes profound suppression of T cell effector function, limiting the tumor regression efficiency of cancer immunotherapy. To address this issue, I utilized sodium zirconium cyclosilicate (ZS-9) as a K+ ion scavenger to relieve the suppression of T cell effector function mediated by excessive K+ ions. When ZS-9 was embedded into a PLGA-PEG-PLGA copolymer-based hydrogel, this system showed good tumor inhibition ability and the promise as a new strategy for cancer immunotherapy.
Inhibiting tumor growth with combination of IL-10/Fc and 4-1BB agonist. One of the major limiting factors for T cell-based immunotherapy is T cell exhaustion, which is characterized by low cytokine production, cytotoxicity, and compromised proliferative capacity. Interleukin-10/Fc fusion protein (IL-10/Fc) has been shown to selectively reinvigorate terminally exhausted CD8+ tumor infiltrating lymphocytes, the direct killers of tumor cells. However, the use of IL-10/Fc alone did not achieve optimal antitumor efficiency, and combining it with adoptive T cell transfer or checkpoint inhibitors was necessary. Intratumoral injection also hindered its further application. To this end, I aimed to develop an IL-10/Fc and 4-1BB agonist based bispecific antibody. While the bispecific antibody could significantly target terminally exhausted CD8+ T cells and promote their proliferation, its antitumor efficacy was limited. However, a combination treatment with IL-10/Fc and 4-1BB agonist showed a synergic effect in eradicating established solid tumors, which was a surprising outcome.