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The limitations of current cancer treatments have stimulated the application of nanotechnology to develop more effective and safer cancer therapies. Remarkable progress has been made in the development of nanomedicine to overcome issues associated with conventional cancer treatment, including low drug solubility, insufficient targeting, and drug resistance. The modulation of nanoparticles allows the improvement of drug pharmacokinetics, leading to improved targeting and reduced side effects. In addition, nanoparticles can be conjugated to ligands that specifically target cancer cells. Furthermore, strategies that exploit tumor characteristics to locally trigger drug release have shown to increase targeted drug delivery. However, although some clinical successes have been achieved, most nanomedicines fail to reach the clinic. Factors that hinder clinical translation vary from the complexity of design, incomplete understanding of biological mechanisms, and high demands during the manufacturing process. Clinical translation might be improved by combining knowledge from different disciplines such as cell biology, chemistry, and tumor pathophysiology. An increased understanding on how nanoparticle modifications affect biological systems is pivotal to improve design, eventually aiding development of more effective nanomedicines. This review summarizes the key successes that have been made in nanomedicine, including improved drug delivery and release by polymeric nanoparticles as well as the introduction of strategies that overcome drug resistance. In addition, the application of nanomedicine in immunotherapy is discussed, and several remaining challenges addressed.

Natural killer (NK) cell-based adoptive immunotherapy is an attractive adjuvant treatment option for patients with acute myeloid leukemia. Recently, we reported a clinical-grade, cytokine-based culture method for the generation of NK cells from umbilical cord blood (UCB) CD34⁺ hematopoietic progenitor cells with high yield, purity and in vitro functionality. The present study was designed to evaluate the in vivo anti-leukemic potential of UCB-NK cells generated with our GMP-compliant culture system in terms of biodistribution, survival and cytolytic activity following adoptive transfer in immunodeficient NOD/SCID/IL2Rg(null) mice. Using single photon emission computed tomography, we first demonstrated active migration of UCB-NK cells to bone marrow, spleen and liver within 24 h after infusion. Analysis of the chemokine receptor expression profile of UCB-NK cells matched in vivo findings. Particularly, a firm proportion of UCB-NK cells functionally expressed CXCR4, what could trigger BM homing in response to its ligand CXCL12. In addition, high expression of CXCR3 and CCR6 supported the capacity of UCB-NK cells to migrate to inflamed tissues via the CXCR3/CXCL10-11 and CCR6/CCL20 axis. Thereafter, we showed that low dose IL-15 mediates efficient survival, expansion and maturation of UCB-NK cells in vivo. Most importantly, we demonstrate that a single UCB-NK cell infusion combined with supportive IL-15 administration efficiently inhibited growth of human leukemia cells implanted in the femur of mice, resulting in significant prolongation of mice survival. These preclinical studies strongly support the therapeutic potential of ex vivo-generated UCB-NK cells in the treatment of myeloid leukemia after immunosuppressive chemotherapy.

The C-type lectin-like receptor CD161 is a well-established marker for human IL17-producing T cells, which have been implicated to contribute to the development of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-SCT). In this study, we analyzed CD161(+) T cell recovery, their functional properties and association with GVHD occurrence in allo-SCT recipients. While CD161(+)CD4(+) T cells steadily recovered, CD161(hi)CD8(+) T cell numbers declined during tapering of Cyclosporine A (CsA), which can be explained by their initial growth advantage over CD161(neg/low)CD8(+) T cells due to ABCB1-mediated CsA efflux. Interestingly, occurrence of acute and chronic GVHD was significantly correlated with decreased levels of circulating CD161(+)CD4(+) as well as CD161(hi)CD8(+) T cells. In addition, these subsets from transplanted patients secreted high levels of IFNγ and IL17. Moreover, we found that CCR6 co-expression by CD161(+) T cells mediated specific migration towards CCL20, which was expressed in GVHD biopsies. Finally, we demonstrated that CCR6(+) T cells indeed were present in these CCL20(+) GVHD-affected tissues. In conclusion, we showed that functional CD161(+)CCR6(+) co-expressing T cells disappear from the circulation and home to GVHD-affected tissue sites. These findings support the hypothesis that CCR6(+)CD161-expressing T cells may be involved in the immune pathology of GVHD following their CCL20-dependent recruitment into affected tissues.