Sialic acid-modified doxorubicin liposomes target tumor-related immune cells to relieve multiple inhibitions of CD8⁺ T cells

In different types of cancer treatments, cancer-specific T cells are required for effective anticancer immunity, which has a central role in cancer immunotherapy. However, due to the multiple inhibitions of CD8(+) T cells by tumor-related immune cells, CD8(+) T-cell mediated antitumor immunotherapy has not achieved breakthrough progress in the treatment of solid tumors. Receptors for sialic acid (SA) are highly expressed in tumor-associated immune cells, so SA-modified nanoparticles are a drug delivery nanoplatform using tumor-associated immune cells as vehicles. To relieve the multiple inhibitions of CD8(+) T cells by tumor-associated immune cells, we prepared SA-modified doxorubicin liposomes (SL-DOX, Scheme 1A). In our study, free SA decreased the toxicity of SL-DOX to tumor-associated immune cells. Compared with common liposomes, SL-DOX could inhibit tumor growth more effectively. It is worth noting that SL-DOX could not only kill tumor-related neutrophils and monocytes to relieve the multiple inhibitions of CD8(+) T cells but also induce immunogenic death of tumor cells to promote the infiltration and differentiation of CD8(+) T cells (Scheme 1B). Therefore, SL-DOX has potential value for the clinical therapeutic effect of CD8(+) T cells mediating anti-tumor immunotherapy.