Targeting MS4A4A on tumour-associated macrophages restores CD8+ T-cell-mediated antitumour immunity.

Checkpoint immunotherapy unleashes T-cell control of tumours but is suppressed by immunosuppressive myeloid cells. The transmembrane protein MS4A4A is selectively highly expressed in tumour-associated macrophages (TAMs). Here, we aimed to reveal the role of MS4A4A+ TAMs in regulating the immune escape of tumour cells and to develop novel therapeutic strategies targeting TAMs to enhance the efficacy of immune checkpoint inhibitor (ICI) in colorectal cancer. The inhibitory effect of MS4A4A blockade alone or combined with ICI treatment on tumour growth was assessed using murine subcutaneous tumour or orthotopic transplanted models. The effect of MS4A4A blockade on the tumour immune microenvironment was assessed by flow cytometry and mass cytometry. RNA sequencing and western blot analysis were used to further explore the molecular mechanism by which MS4A4A promoted macrophages M2 polarisation. MS4A4A is selectively expressed by TAMs in different types of tumours, and was associated with adverse clinical outcome in patients with cancer. In vivo inhibition of MS4A4A and anti-MS4A4A monoclonal antibody treatment both curb tumour growth and improve the effect of ICI therapy. MS4A4A blockade treatment reshaped the tumour immune microenvironment, resulting in reducing the infiltration of M2-TAMs and exhausted T cells, and increasing the infiltration of effector CD8+ T cells. Anti-MS4A4A plus anti-programmed cell death protein 1 (PD-1) therapy remained effective in large, treatment-resistant tumours and could induce complete regression when further combined with radiotherapy. Mechanistically, MS4A4A promoted M2 polarisation of macrophages by activating PI3K/AKT pathway and JAK/STAT6 pathway. Targeting MS4A4A could enhance the ICI efficacy and represent a new anticancer immunotherapy.

Li Y ，Shen Z ，Chai Z ，Zhan Y ，Zhang Y ，Liu Z ，Liu Y ，Li Z ，Lin M ，Zhang Z ，Liu W ，Guan S ，Zhang J ，Qian J ，Ding Y ，Li G ，Fang Y ，Deng H ... -  《-》

Targeting MS4A4A: A novel pathway to improve immunotherapy responses in glioblastoma.

Glioblastoma (GBM) remains a challenging brain tumor to treat, with limited response to PD-1 immunotherapy due to tumor-associated macrophages (TAMs), specifically the M2 phenotype. This study explores the potential of MS4A4A (membrane spanning four domains, subfamily A, member 4A) inhibition in driving M2 macrophage polarization toward the M1 phenotype via the ferroptosis pathway to enhance the effectiveness of immunotherapy in GBM. Single-cell RNA sequencing and spatial transcriptomic analyses were employed to characterize M2 macrophages and MS4A4A expression in GBM. In vitro studies utilizing TAM cultures, flow cytometry, and western blot validations were conducted to assess the impact of MS4A4A on the tumor immune microenvironment and M2 macrophage polarization. In vivo models, including subcutaneous and orthotopic transplantation in mice, were utilized to evaluate the effects of MS4A4A knockout and combined immune checkpoint blockade (ICB) therapy on tumor growth and response to PD-1 immunotherapy. Distinct subsets of GBM-associated macrophages were identified, with spatial distribution in tumor tissue elucidated. In vivo experiments demonstrated that inhibiting MS4A4A and combining ICB therapy effectively inhibited tumor growth, reshaped the tumor immune microenvironment by reducing M2 TAM infiltration and enhancing CD8+ T-cell infiltration, ultimately leading to complete tumor eradication. MS4A4A inhibition shows promise in converting M2 macrophages to M1 phenotype via ferroptosis, decreasing M2-TAM infiltration, and enhancing GBM response to PD-1 immunotherapy. These findings offer a novel approach to developing more effective immunotherapeutic strategies for GBM.

Shao G ，Cui X ，Wang Y ，Luo S ，Li C ，Jiang Y ，Cai D ，Li N ，Li X ... -  《-》

TREM2(+) macrophages suppress CD8(+) T-cell infiltration after transarterial chemoembolisation in hepatocellular carcinoma.

The immune landscape of hepatocellular carcinoma (HCC) following transarterial chemoembolisation (TACE) remains to be clarified. This study aimed to characterise the immune landscape following TACE and the underlying mechanism of HCC progression. Tumour samples from five patients with treatment-naive HCC and five patients who received TACE therapy were collected and subjected to single-cell RNA sequencing. Another 22 paired samples were validated using immunofluorescence staining and flow cytometry. To clarify the underlying mechanisms, in vitro co-culture experiments and two types of TREM2-KO/WT mouse models, namely, an HCC cell orthotopic injection model and a spontaneous HCC model, were used. A reduced number of CD8+ T cells and an increased number of tumour-associated macrophages (TAMs) were observed in the post-TACE microenvironment. TACE therapy reduced the cluster CD8_C4, which was highly enriched with tumour-specific CD8+ T cells of pre-exhausted phenotype. TREM2 was found to be highly expressed in TAMs following TACE, which was associated with a poor prognosis. TREM2+ TAMs secreted less CXCL9 but more galectin-1 than did TREM2- TAMs. Galectin-1 promoted PD-L1 overexpression in vessel endothelial cells, impeding CD8+ T cell recruitment. TREM2 deficiency also increased CD8+ T cell infiltration, which inhibited tumour growth in both in vivo HCC models. More importantly, TREM2 deficiency enhanced the therapeutic effect of anti-PD-L1 blockade. This study shows that TREM2+ TAMs play an important role in suppressing CD8+ T cells. TREM2 deficiency increased the therapeutic effect of anti-PD-L1 blockade by enhancing antitumour activity of CD8+ T cells. These findings explain the reasons for recurrence and progression after TACE and provide a new target for HCC immunotherapy after TACE. Studying the immune landscape in post-TACE HCC is important to uncover the mechanisms of HCC progression. By using scRNA sequencing and functional assays, we discovered that both the number and function of CD8+ T cells are compromised, whereas the number of TREM2+ TAMs is increased in post-TACE HCC, correlating with worse prognosis. Moreover, TREM2 deficiency dramatically increases CD8+ T cell infiltration and augments the therapeutic efficacy of anti-PD-L1 blockade. Mechanistically, TREM2+ TAMs display lower CXCL9 and increased Gal-1 secretion than do TREM2- TAMs, with Gal-1 mediating the overexpression of PD-L1 in vessel endothelial cells. These results suggest that TREM2 could be a novel immunotherapeutic target for patients treated with TACE in HCC. This provides an opportunity to break the plateau of limited therapeutic effect. This study has the value of understanding the tumour microenvironment of post-TACE HCC and thinking a new strategy of immunotherapy in the field of HCC. It is therefore of key impact for physicians, scientists and drug developers in the field of liver cancer and gastrointestinal oncology.

Tan J ，Fan W ，Liu T ，Zhu B ，Liu Y ，Wang S ，Wu J ，Liu J ，Zou F ，Wei J ，Liu L ，Zhang X ，Zhuang J ，Wang Y ，Lin H ，Huang X ，Chen S ，Kuang M ，Li J ... -  《-》

Targeting cancer-associated fibroblast-secreted WNT2 restores dendritic cell-mediated antitumour immunity.

Solid tumours respond poorly to immune checkpoint inhibitor (ICI) therapies. One major therapeutic obstacle is the immunosuppressive tumour microenvironment (TME). Cancer-associated fibroblasts (CAFs) are a key component of the TME and negatively regulate antitumour T-cell response. Here, we aimed to uncover the mechanism underlying CAFs-mediated tumour immune evasion and to develop novel therapeutic strategies targeting CAFs for enhancing ICI efficacy in oesophageal squamous cell carcinoma (OSCC) and colorectal cancer (CRC). Anti-WNT2 monoclonal antibody (mAb) was used to treat immunocompetent C57BL/6 mice bearing subcutaneously grafted mEC25 or CMT93 alone or combined with anti-programmed cell death protein 1 (PD-1), and the antitumour efficiency and immune response were assessed. CAFs-induced suppression of dendritic cell (DC)-differentiation and DC-mediated antitumour immunity were analysed by interfering with CAFs-derived WNT2, either by anti-WNT2 mAb or with short hairpin RNA-mediated knockdown. The molecular mechanism underlying CAFs-induced DC suppression was further explored by RNA-sequencing and western blot analyses. A negative correlation between WNT2+ CAFs and active CD8+ T cells was detected in primary OSCC tumours. Anti-WNT2 mAb significantly restored antitumour T-cell responses within tumours and enhanced the efficacy of anti-PD-1 by increasing active DC in both mouse OSCC and CRC syngeneic tumour models. Directly interfering with CAFs-derived WNT2 restored DC differentiation and DC-mediated antitumour T-cell responses. Mechanistic analyses further demonstrated that CAFs-secreted WNT2 suppresses the DC-mediated antitumour T-cell response via the SOCS3/p-JAK2/p-STAT3 signalling cascades. CAFs could suppress antitumour immunity through WNT2 secretion. Targeting WNT2 might enhance the ICI efficacy and represent a new anticancer immunotherapy.

Huang TX ，Tan XY ，Huang HS ，Li YT ，Liu BL ，Liu KS ，Chen X ，Chen Z ，Guan XY ，Zou C ，Fu L ... -  《-》

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 ... -  《-》