A lysosome-targeted DNA nanodevice selectively targets macrophages to attenuate tumors

Activating CD8+ T cells by antigen cross-presentation is remarkably effective at eliminating tumors. Although this function is traditionally attributed to dendritic cells, tumor-associated macrophages (TAMs) can also cross-present antigens. TAMs are the most abundant tumor-infiltrating leukocyte. Yet, TAMs have not been leveraged to activate CD8+ T cells because mechanisms that modulate their ability to cross-present antigens are incompletely understood. Here we show that TAMs harbor hyperactive cysteine protease activity in their lysosomes which impedes antigen cross-presentation, thereby preventing CD8+ T cell activation. We developed a DNA nanodevice (E64-DNA) targeted to lysosomes of TAMs in mice. E64-DNA inhibits the population of cysteine proteases present specifically inside lysosomes of TAMs, improves their ability to cross-present antigens, and attenuates tumor growth via CD8+ T cells. When combined with cyclophosphamide, E64-DNA showed sustained tumor regression in a triple-negative-breast-cancer model. Our studies demonstrate that DNA nanodevices can be targeted with organelle-level precision to reprogram macrophages and achieve immunomodulation in vivo.