Engineering T Cell Trafficking and Function for Enhanced Cancer Immunotherapy

In the past decades, breakthroughs in cancer immunotherapy have led to unprecedented clinical responses in patients with advanced-stage cancers that would otherwise be fatal. However, treatment of many solid organ malignancies with highly immunosuppressive tumor microenvironment (TME) remains challenging. Tumors develop a number of mechanisms to prevent effector T-cells from reaching tumors and to suppress their function. T-cell infiltration into solid tumor, a key limiting factor for efficacious cancer immunotherapy, has been demonstrated to be associated with good clinical outcomes in various cancer immunotherapies. Safe and effective strategies to improve T-cell infiltration and augment T-cell expansion and function in solid tumors are highly desired to enhance the clinical response rate of cancer immunotherapies in the treatment of solid tumors. Disruption of chemotaxis of lymphocytes is likely a main contributing factor for effector T-cell exclusion; chemokines are known to play a critical role in orchestrating T-cell trafficking and tumor infiltration. Here, we developed a TME-responsive nanogel (NG) based on a novel carrier-free delivery strategy to effectively and specifically co-deliver T-cell recruiting chemokines and immunostimulatory cytokines in order to enhance infiltration and function of effector T-cells in solid tumors. In the preliminary studies, a chemokine (e.g. CCL19) and a cytokine (IL-2) were chemically co-crosslinked with a redox responsive linker to form the binary protein nanogels (BNGs). These BNGs had exceptionally high loading capacity of cytokines and chemokines and controlled size. BNGs released native cytokine/chemokine proteins in response to increased reduction which is one of the biochemical characteristics of TME, and thus enabled tumor-specific delivery of the incorporated cytokines and chemokines. In vitro chemotaxis assays showed that the released chemokines from BNG possessed the similar chemotactic ability in recruiting activated T-cells. Preliminary in vivo study in subcutaneous B16F10 mouse melanoma in C57BL/6 mice showed that intratumorally administration of BNG enhanced T-cell infiltration and improved immunosuppressive TME compared to free cytokines or chemokines at equivalent doses. In future, we first plan to further improve the controlled formulation of chemokine NG by complexing chemokines with anionic polysaccharides and stabilizing chemokines with non-functional proteins/polymers or recombinantly expressing chemokine-Fc fusion. Then, we plan to enhance the potency of NG for T-cell infiltration and function by delivery combinational chemokines and by activating LTβR signaling with LIGHT delivery. Furthermore, to improve the tumor-targeting effect of NG, we will synthesize cross-linkers in response to different characteristics of TME, prolong the half-life of NG for increased tumor targeting and hijack tumor-related immune cells. Finally, we will try to overcome the immunosuppression in TME by combining NG with checkpoint blockade or adoptive T-cell immunotherapies.