The metabolic reprogramming of tumors, characterized by dysregulated glycolysis and mitochondrial dysfunction, drives profound tumor microenvironmental remodeling that causes immune evasion and therapeutic resistance [1], [2], [3], [4]. The metabolic shift not only depletes oxygen and nutrients but also generates severe hypoxia, triggering the stabilization of hypoxia-inducible factor-1α (HIF-1α) [5], [6]. Accumulating evidence has demonstrated that HIF-1α can drive the overexpression of CD73, a key ectoenzyme in the adenosinergic pathway, which catalyzes the conversion of extracellular ATP into immunosuppressive ADO [7], [8], [9], [10]. ADO suppresses antitumor immunity by binding to A2A receptors on cytotoxic T cells and natural killer (NK) cells, impairing their effector functions, while simultaneously expanding regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), exacerbating the immunosuppressive tumor microenvironment [11], [12], [13], [14]. Paradoxically, conventional therapies such as radiotherapy (RT), while inducing DNA damage in cancer cells, also upregulate CD73 expression via DNA damage-ATR-Chk1-STAT3 signaling, signaling in surviving tumor cells, creating an ADO-rich milieu that drives tumor metastasis and recurrence and limits therapeutic efficacy [15], [16], [17]. The effect of RT mediated upregulation of immunosuppressive CD73 expression highlights the critical need to disrupt the CD73-adenosine axis to potentiate the efficacy of radioimmunotherapy.
Meanwhile, the dysregulated metabolism of solid tumors also leads to extracellular acidosis, characterized by lactate and proton accumulation [18], [19], [20]. Acidic pH (6.5–7.0) directly impairs the function of immune cells, including dendritic cell maturation and T cell receptor signaling, while promoting the polarization of tumor-associated macrophages (TAMs) toward an immunosuppressive M2 phenotype [21], [22], [23], [24]. Furthermore, acidosis stabilizes CD73 transcription by enhancing HIF-1α activity, synergizing with hypoxia to amplify adenosine production [25], [26], [27]. Conventional RT, though effective in localized tumor control, inadvertently aggravates acidosis by increasing glycolytic flux in radioresistant cells and disrupting vascular integrity, which further restricts oxygen diffusion and exacerbates hypoxia [28], [29]. To date, numerous acid-neutralizing strategies have been developed to mitigate extracellular acidosis [30], [31], including small-molecule inhibitors targeting lactate transporters (e.g., monocarboxylate transporters, MCTs) [32], [33] and proton channel proteins (e.g., V-ATPase) [34], [35], [36]. Furthermore, some nanoparticles capable of the “proton sponge” effect, including calcium carbonate (CaCO3) [37], [38], [39], [40] and manganese dioxide (MnO2) [41], [42] have been engineered to neutralize excess protons within tumor regions and have shown promise in restoring radiosensitivity. Considering that the tumor microenvironment undergoes dynamic remodeling, necessitates combinatorial modulation of metabolic reprogramming to achieve durable therapeutic outcomes.
Layered double hydroxide (LDH) nanosheets, a class of anionic clay materials, have emerged as a highly promising nanoplatform due to their unique features including versatile drug-loading capacity, acid-responsive biodegradability, as well as proton sponge effect [43], [44], [45]. In this work, we developed multifunctional Mn/Al layered double hydroxide nanosheets (LDH NSs) loaded with the CD73 inhibitor PSB-12379 (LDH@PSB) for simultaneous tumor acidosis neutralization and ADO blockade to enhance radioimmunotherapy. LDH@PSB exhibited pH-responsive degradation, efficiently releasing PSB-12379 and elevating tumor pH from ∼6.5 to ∼7.0. This alleviation of acidity enhanced radiation-induced apoptosis and immunogenic cell death, increasing extracellular ATP. Released PSB-12379 suppressed radiation-induced CD73 upregulation, blocking ATP hydrolysis into immunosuppressive ADO. Meanwhile, Mn2⁺ ions from LDH@PSB activated the cGAS-STING pathway, synergizing to relieve tumor immunosuppression and amplify antitumor immunity. In B16F10 and CT26 tumor models, LDH@PSB combined with radiotherapy significantly inhibited tumor growth and prolonged survival. Integration with anti-PD-1 therapy further triggered systemic abscopal effects, enhancing dendritic cell maturation, cytotoxic T cell infiltration, and reversing immunosuppression. This combination also induced durable antigen-specific immune response to inhibit distant tumor growth. Our strategy effectively overcomes radioresistance by disrupting the acidosis-ADO axis and activating STING signaling, offering a promising approach to potentiate radioimmunotherapy.