Nanomedicine and cancer immunotherapy - targeting immunosuppressive cells.

The search for pharmacological strategies to reach and impact on immunosuppressive cells is, currently, one of the most exciting areas in cancer immunology and clinical oncology. In this context, it is increasingly accepted that the success of these therapies will largely depend on the availability of appropriate drug delivery strategies. Considering the critical role that nanotechnology plays in the development of these novel therapies, the main goal of this article is to provide an overview of the potential of nanomedicines targeted to immunosuppressive cells for the treatment of cancer. We present, first, a brief description of classical cancer immunotherapies based on therapeutic vaccination and monoclonal antibodies, with a special focus on the use of nanotechnologies and the targeting of immunological checkpoints. Second, we provide a thoughtful analysis of the possibilities to target the immunosuppressive cells, namely tumour-associated macrophages, myeloid-derived suppressor cells, tumour-associated neutrophils and regulatory T cells, at the tissue level (i.e. tumour, spleen, blood, lymph) and, also, at the cellular level. Finally, we wrap the article with a disclosure of strategies used to impair the generation, kill or re-educate these immunosuppressive cells, thus providing an up-to-date picture of the choices available for therapeutic intervention.