Leveraging biomaterials for cancer immunotherapy: targeting pattern recognition receptors

Cancer immunotherapy actuating patient's immune system to control cancer is redefining the field of cancer therapy today. Although targeting T cells has proven a technically successful treatment strategy for most cancer immunotherapies, only a limited subset of patients respond favorably to these interventions. Of late, there has been a surge of interest in investigating the relatively underexplored innate immune system as a possible tool for therapeutic intervention. Pattern recognition receptors (PRRs) mediate crucial roles in the functioning of the innate immune system, and endogenous or exogenous PRR agonists have been shown to effectively activate the immune system inside the tumor microenvironment, and this leads to subsequent innate and adaptive antitumor immune responses. Importantly, the innate immune response is required to be carefully regulated as unchecked immune response can contribute to deleterious consequences. Herein, we review recent progress in leveraging biomaterials as carriers of PRR agonists for cancer immunotherapy. Properly designed microformulations or nanoformulations, hydrogels, implants, and scaffolds can markedly enhance the immune activation efficacy of the PRR agonists, as well as reducing their side-effects, directing new potentials in cancer immunotherapy.