A manganese-doped layered double hydroxide loaded with lactate oxidase and DNA repair inhibitors for synergistically enhanced tumor immunotherapy

Tumor immunotherapy has gained more and more attention in tumor treatment. However, the accumulation of lactic acid in tumor tissue inhibits the response of immune cells to form an immunosuppressive microenvironment (ISME). To reverse the ISME, an acid-responsive nanoplatform (termed as MLLN@HA) is reported for synergistically enhanced tumor immunotherapy. MLLN@HA is constructed by the co-loading of lactate oxidase (LOX) and DNA repair inhibitor (NU7441) in a manganese-doped layered double hydroxide (Mn-LDH), and then modified with hyaluronic acid (HA) for tumor-targeted delivery. After endocytosis by tumor cells, MLLN@HA decomposes and releases LOX, NU7441 and Mn 2+ ions in the acidic tumor microenvironment. The released LOX catalyzes the conversion of lactic acid into hydrogen peroxide (H 2 O 2 ), which not only alleviates the ISME, but also provides reactants for the Mn 2+ -mediated Fenton-like reaction to enhance chemodynamic therapy (CDT). Released NU7441 prevents CDT-induced DNA damage from being repaired, thereby increasing double-stranded DNA (dsDNA) fragments within tumor cells. Importantly, the released Mn 2+ ions enhance the sensitivity of cyclic GMP-AMP synthase (cGAS) to dsDNA fragments, and activate the stimulator of interferon genes (STING) to induce an anti-tumor immune response. Such an orchestrated immune-boosting strategy ultimately achieves effective tumor growth inhibition and prevents tumor lung metastasis. Statement of significance To improve the efficacy of tumor immunotherapy, an innovative acid-responsive MLLN@HA nanoplatform was developed for synergistically enhanced tumor immunotherapy. The MLLN@HA actively targets to tumor cells through the interaction of HA with CD44, and then degrades to release LOX, NU7441 and Mn 2+ ions in the acidic tumor microenvironment. The released LOX generates H 2 O 2 for the Mn 2+ -mediated Fenton reaction and reverses the ISME by consuming lactate. NU7441 prevents DNA damage repair, leading to an increased concentration of free DNA fragments, while Mn 2+ ions activate the cGAS-STING pathway, enhancing the systemic anti-tumor immune response. The orchestrated immune-boosting nanoplatform effectively inhibits tumor growth and lung metastasis, presenting a promising strategy for cancer treatment.