Tumor microenvironment remodeling via targeted depletion of M2-like tumor-associated macrophages for cancer immunotherapy.

M2-like tumor-associated macrophages (TAMs) typically exhibit numerous tumor-promoting properties. Reducing the abundance of M2-like TAMs would shed light on the relief of immunosuppressive tumor microenvironment (TME), activation of the host immune system, infiltration of CD8+ T cells into the TME and restoring the function of the infiltrating T cells, which collectively inhibits tumor growth. Therefore, targeted depletion of M2-like TAMs can be a promising immunotherapy approach. In this study, we rationally constructed an M2-like TAMs-targeted nanoliposome, which encapsulates zoledronic acid (ZA) in the core, loads hematoporphyrin monomethyl ether (HMME, a typical sonosensitizer) in the lipid bilayer, and modifies M2pep peptide (the targeting unit) on the surface (designated as M-H@lip-ZA). Our aim is to validate the effectiveness of M-H@lip-ZA nanoliposomes to remodel TME via targeted depletion of M2-like TAMs for cancer immunotherapy. Through the M2pep peptide, M-H@lip-ZA can be efficiently delivered to M2-like TAMs. In the meantime, reactive oxygen species (ROS) resulting from sonodynamic therapy (SDT), together with inner ZA that shows high affinity and cytotoxicity to TAMs, can effectively deplete M2-like TAMs and remodel TME (normalize tumor vasculatures, strengthen intertumoral perfusion, ease tumor hypoxia, increase immune-promoting cytokines and decrease immunosuppressive cytokines). The tumor growth can be effectively inhibited. This work proposed a new paradigm for cancer immunotherapy via targeted depletion of M2-like TAMs. STATEMENT OF SIGNIFICANCE: • M2-like TAMs-targeted nanoliposome (M-H@lip-ZA) was designed and prepared. • Sonodynamic therapy (SDT), together with zoledronic acid (ZA) that shows high affinity and cytotoxicity to tumor-associated macrophages (TAMs), can effectively deplete M2-like TAMs. Subsequently, immune-promoting tumor microenvironment (TME) can be formed, which includes normalized tumor vasculatures, enhanced intertumoral perfusion, relieved tumor hypoxia, increased immune-promoting cytokines, and decreased immunosuppressive cytokines. • The targeted depletion of M2-like TAMs is a promising cancer immunotherapy approach.

Cao Y ，Qiao B ，Chen Q ，Xie Z ，Dou X ，Xu L ，Ran H ，Zhang L ，Wang Z ... -  《-》

Targeted delivery of zoledronic acid through the sialic acid - Siglec axis for killing and reversal of M2 phenotypic tumor-associated macrophages - A promising cancer immunotherapy.

Immune checkpoint inhibitors (ICIs), like monoclonal antibodies of PD-1, CTLA-4, and their ligands, are effective only in some populations of patients with cancer, because the immunosuppressive state of the tumor microenvironment (TME) in some patients cannot be effectively reversed after ICI therapy. Sialic acid (SA) receptors in the Siglec family are highly expressed on the surface of tumor-associated macrophages (TAMs) and most have immunosuppressive effects. Therefore, targeting TAMs (the siglec axis) to reverse tumor immunosuppression may provide a new direction for the development of novel tumor immunotherapies. We designed a Zoledronic acid (ZA)-loaded liposome modified by a SA-octadecylamine conjugate (ZA-SL) to act as a novel nanomedicine delivery platform. This platform can efficiently deliver ZA to TAMs through the combination of SA and Siglec-1 and exerts specific cytotoxicity or phenotypic remodeling of M2-like TAMs depending on the drug concentration in TAMs. In vivo experiments showed that ZA-SL had good TAM targeting ability, and after treatment, the S180 tumors of mice were significantly inhibited, and the proportion of M1-like TAMs was significantly higher than that of M2-like TAMs with no significant adverse reactions in mice. Therefore, SA-modified ZA-loaded liposomes may provide a promising strategy for cancer immunotherapy.

Tang X ，Sui D ，Liu M ，Zhang H ，Liu M ，Wang S ，Zhao D ，Sun W ，Liu M ，Luo X ，Lai X ，Liu X ，Deng Y ，Song Y ... -  《-》

Tumor microenvironment remodeling and tumor therapy based on M2-like tumor associated macrophage-targeting nano-complexes.

Background: Among the many immunosuppressive cells in the tumor microenvironment, tumor-associated-macrophages (TAMs) are well known to contribute to tumor development. TAMs can be conditioned (polarized) to transition between classical M1-like macrophages, or alternatively to M2-like macrophages. Both are regulated by signaling molecules in the microenvironment. M1-like TAMs can secrete classic inflammatory cytokines that kill tumors by promoting tumor cell necrosis and immune cell infiltration into the tumor microenvironment. In contrast, M2-like TAMs exhibit powerful tumor-promoting functions, including degradation of tumor extracellular matrix, destruction of basement membrane, promotion of angiogenesis, and recruitment of immunosuppressor cells, all of which further promote tumor progression and distal metastasis. Therefore, remodeling the tumor microenvironment by reversing the TAM phenotype will be favorable for tumor therapy, especially immunotherapy. Methods: PLGA nanoparticles encapsulating baicalin and melanoma antigen Hgp peptide fragment 25-33 were fabricated using the ultrasonic double-emulsion technique. The nanoparticles were further loaded with CpG fragments and used conjugated M2pep and α-pep peptides on their surfaces to produce novel nano-complexes. The capability to target M2-like TAMs and anti-tumor immunotherapy effects of nano-complexes were evaluated by flow cytometry and confocal microscopy in vitro. We also investigated the survival and histopathology of murine melanoma models administrated with different nanocomplexes. Improvements in the tumor microenvironment for immune attack of melanoma-bearing mice were also assessed. Results: The nano-complexes were effectively ingested by M2-like TAMs in vitro and in vivo, and the acidic lysosomal environment triggered the disintegration of polydopamine from the nanoparticle surface, which resulted in the release of the payloads. The released CpG played an important role in transforming the M2-like TAMs into the M1-like phenotype that further secreted inflammatory cytokines. The reversal of TAM released cytokines and gradually suppressed tumor angiogenesis, permitting the remodeling of the tumor microenvironment. Moreover, the activated TAMs also presented antigen to T cells, which further stimulated the antitumor immune response that inhibited tumor metastasis. Activated T cells released cytokines, which stimulated NK cell infiltration and directly resulted in killing tumor cells. The baicalin released by M1-like TAMs also killed tumor cells. Conclusion: The nano-complexes facilitated baicalin, antigen, and immunostimulant delivery to M2-like TAMs, which polarized and reversed the M2-like TAM phenotype and remodeled the tumor microenvironment to allow killing of tumor cells.

Han S ，Wang W ，Wang S ，Yang T ，Zhang G ，Wang D ，Ju R ，Lu Y ，Wang H ，Wang L ... -  《Theranostics》

Molecular-Targeted Immunotherapeutic Strategy for Melanoma via Dual-Targeting Nanoparticles Delivering Small Interfering RNA to Tumor-Associated Macrophages.

Qian Y ，Qiao S ，Dai Y ，Xu G ，Dai B ，Lu L ，Yu X ，Luo Q ，Zhang Z ... -  《-》

Blocking LTB(4) signaling-mediated TAMs recruitment by Rhizoma Coptidis sensitizes lung cancer to immunotherapy.

Immune checkpoint blockade (ICB) induces durable immune responses across a spectrum of advanced cancers and revolutionizes the oncology field. However, only a subset of patients achieves long-lasting clinical benefits. Tumor-associated macrophages (TAMs) usually secrete immunosuppressive cytokines and contribute to the failure of ICB therapy. Therefore, it is crucial to mechanically manipulate the abundance and function of TAMs in the tumor microenvironment (TME), which can offer a promising molecular basis to improve the clinical response efficacy of ICB in cancer patients. This study aims to investigate TAMs in the immunosuppressive microenvironment to identify new therapeutic targets, improve the ability to predict and guide responses to clinical immunotherapy, and develop new strategies for immunotherapy of lung tumors. Lewis lung carcinoma (LLC) xenograft-bearing mouse models were established to analyze the antitumor activity of Rhizoma Coptidis (RC) in vivo. A systems pharmacology strategy was used to predict the correlation between RC and M2 macrophages. The effect of RC on the abundance of M2 macrophages was analyzed by flow cytometry of murine samples. Western blot was performed to analyze the expression of Leukotriene A4 hydrolase (LTA4H) and LTB4 receptor 1 (BLT1) in harvested lung cancer tissues. The impact of blocking leukotriene B4 (LTB4) signaling by RC on the recruitment of M2 macrophages was assessed in vitro and in vivo. Transwell migration assays were conducted to clarify the inhibition of macrophage migration by blocking LTB4. Lta4h-/- mice were used to investigate the sensitivity of immunotherapy to lung cancer by blocking the LTB4 signaling. Here, we report that RC, an herbal medicine from the family Ranunculaceae, suppresses the recruitment and immunosuppressive function of TAMs, which in turn sensitizes lung cancer to ICB therapy. Firstly, a systems pharmacology strategy was proposed to identify combinatorial drugs for ICB therapy with a systems biology perspective of drug-target-pathway-TME phenotype. We predicted and verified that RC significantly inhibits tumor growth and the infiltration of M2-TAMs into TME of LLC tumor-bearing mice. Then, RC inhibits the recruitment of macrophages to the tumor TME via blocking LTB4 signaling, and suppresses the expression of immunosuppressive factors (IL-10, TGF-β and VEGF). As a result, RC enables CD8+ T cells to retain their proliferative and infiltrative abilities within the TME. Ultimately, these events promote cytotoxic T-cell-mediated clearance of tumor cells, which is further enhanced by the addition of anti-PD-L1 therapy. Furthermore, we employed LTA4H deficient mice (Lta4h-/- mice) to evaluate the antitumor efficiency, the results showed that the efficacy of immunotherapy was enhanced due to the synergistic effect of LTB4 signaling blockage and ICB inhibition, leading to remarkable inhibition of tumor growth in a mouse model of lung adenocarcinoma. Taken together, these findings suggest that RC enhances antitumor immunity, providing a rationale for combining RC with immunotherapies as a potential anti-cancer treatment strategy.

Yan J ，Zhu J ，Li X ，Yang R ，Xiao W ，Huang C ，Zheng C ... -  《-》