Abstract
Simple Summary Conventional anti-cancer treatments for metastatic tumors include chemotherapy and radiation. These approaches can result in harmful side-effects and, in the vast majority of cases, are not curative. Recently, novel treatments have been developed in order to stimulate the host immune system to fight cancer. This type of therapeutic approach, called immunotherapy, has gained a lot of attention in recent years due to discoveries that have deciphered the immunosuppressive role of the tumor microenvironment and underpinning molecular signals. To enhance the delivery of therapeutic drugs to the tumor site, nanoparticle-based delivery systems can be used to reduce off-target effects, and to modulate immune cells present in the tumor microenvironment. This novel therapeutic approach can synergize with other immunotherapies such as immune checkpoint blockade inhibitors and adoptive cell therapy, by enhancing the infiltration of activated immune cells to the tumor site, and by limiting local immunosuppression. A number of novel cancer therapies have recently emerged that have rapidly moved from the bench to the clinic. Onco-immunotherapies, such as immune checkpoint blockade inhibitors and adoptive cell therapies, have revolutionized the field, since they provide a way to induce strong anti-tumor immune responses, which are able to fight cancer effectively. However, despite showing great efficacy in hematological and some solid tumors, unresponsiveness, development of therapy resistance and the development of serious adverse effects, limit their capacity to impact the vast majority of tumors. Nanoparticle-based delivery systems are versatile vehicles for a wide variety of molecular cargoes and provide an innovative strategy to improve conventional onco-immunotherapies. They can be finely tuned to release their contents in the tumor microenvironment, or to deliver combinations of adjuvants and antigens in the case of nanovaccines. In this review, we summarize the recent advancements in the field of nanobiotechnology, to remodel the tumor microenvironment and to enhance immunotherapies.