PBA-Modified α-cyano-4-hydroxycinnamate and Gefitinib Liposomes for Macrophage Metabolic Reprogramming to Boost Antitumor Immunity

Objectives: Tumor cells produce and release significant amounts of lactic acid (LA) via glucose glycolysis, creating an acidic, high-LA tumor microenvironment. This microenvironment promotes the M2 polarization of tumor-associated macrophages (TAMs) and leads to immunosuppression. This study aims to reprogram TAM metabolism and boost antitumor immunity by synergistically reducing extracellular LA levels using a dual-liposome formulation strategy. Methods: We prepared phenylboronic acid (PBA)-modified α-cyano-4-hydroxycinnamate (CHC) liposomes (PBA-CHC-LIP) to target 4T1 tumor cells and inhibit monocarboxylate transporter 4 (MCT4), thereby suppressing LA efflux. Concurrently, gefitinib lactate (GFB-LA) was synthesized to construct high-loading gefitinib liposomes (GFB-LIP) via an active loading method. In vitro experiments were conducted using 4T1 and RAW264.7 cells, and in vivo experiments were performed using a 4T1 tumor-bearing mouse model to evaluate the synergistic effects of the combined therapy on LA efflux, cell apoptosis, macrophage polarization, and tumor progression. Results: PBA-CHC-LIP effectively targeted 4T1 cells and significantly inhibited LA efflux. GFB-LIP achieved an ideal drug loading of 5.3% and an encapsulation efficiency of 94%, promoting 4T1 cell apoptosis and further reducing LA production. The synergistic treatment significantly decreased LA concentrations in the tumor microenvironment both in vitro and in vivo, thereby inhibiting the M2 polarization of TAMs (evidenced by decreased CD206, IL-10, Arg-1, and TGF-β1) and enhancing the M1-TAM-mediated immune response (indicated by elevated IL-12, iNOS, and TNF-α). The combined therapy also effectively inhibited the growth of tumor volume and weight in vivo. Conclusions: The synergistic therapy of PBA-CHC-LIP and GFB-LIP successfully reduced LA levels in the tumor microenvironment and achieved the metabolic reprogramming of tumor-associated macrophages. This provides a novel and effective strategy for reshaping the tumor immune microenvironment and enhancing antitumor therapy.