Liposomal honokiol inhibits non-small cell lung cancer progression and enhances PD-1 blockade via suppressing M2 macrophages polarization

Background: Honokiol (HNK), a natural phenolic compound derived from Magnolia plants, exhibits therapeutic effects on various diseases, including cancer. The advent of immune checkpoint inhibitors (ICIs) has marked a breakthrough in non-small cell lung cancer (NSCLC) treatment. However, a significant subset of patients exhibits primary or acquired resistance to anti-PD-1/PD-L1 therapies, necessitating the development of novel combination strategies to enhance therapeutic efficacy and overcome resistance. Purpose: This study aimed to explore the anti-tumor efficacy of liposomal honokiol (Lipo-HNK) and elucidate the synergistic effects of Lipo-HNK and ICIs on NSCLC. Methods: The effects of Lipo-HNK on cell proliferation and apoptosis were assessed in human lung cancer cell lines H460 and A549, and mouse Lewis lung cancer cell line (LL2). A murine lung cancer model was established by injecting LL2 cells via the tail vein to evaluate the therapeutic effects of Lipo-HNK and ICIs. Tumor microenvironment features were characterized using immunofluorescence and flow cytometry. Primary macrophages were extracted from mouse bone marrow for mechanistic studies. High-throughput sequencing and bioinformatics analyses of Lipo-HNK-treated macrophages were conducted to identify key signaling pathways, which were subsequently confirmed by Western blotting and inhibitor blockade. Results: Lipo-HNK, with enhanced solubility and bioavailability, demonstrated potent cytotoxicity against NSCLC cell lines. In the murine lung cancer model, Lipo-HNK exhibited synergistic anti-cancer effects when combined with anti-PD-1 therapy. Immunofluorescence and flow cytometry analyses revealed that Lipo-HNK significantly reduced the infiltration of myeloid-derived suppressor cells (MDSCs) and M2 macrophages (CD206+). Macrophage depletion experiment showed the anti-tumor effects of Lipo-HNK was macrophage-dependent. M2 macrophages induced by tumor-conditioned medium (TCM) or interleukin-4 (IL-4) released immunosuppressive cytokines such as IL-10, Arg-1, and TGF-beta. RNA sequencing analyses showed that Lipo-HNK effectively inhibited the PI3K/Akt signaling pathway, blocking macrophage polarization to the M2 type. Furthermore, the combination of Lipo-HNK and anti-PD-1 therapy led to increased CD8+ T-cell infiltration and activation, enhancing the overall anti-tumor immune response. Conclusion: This study validated the anti-tumor efficacy of Lipo-HNK against NSCLC. Lipo-HNK reduced the infiltration of MDSCs and M2 macrophages by inhibiting the PI3K/Akt pathway and enhanced the therapeutic effects of ICIs. These findings provide evidence and new insights into Lipo-HNK as a promising anti-cancer drug for NSCLC treatment, highlighting its potential to overcome resistance to current ICI therapies.