Blocking Triggering Receptor Expressed on Myeloid Cells-1-Positive Tumor-Associated Macrophages Induced by Hypoxia Reverses Immunosuppression and Anti-Programmed Cell Death Ligand 1 Resistance in Liver Cancer.

Tumor-associated macrophages (TAMs) are recognized as antitumor suppressors, but how TAMs behave in the hypoxic environment of hepatocellular carcinoma (HCC) remains unclear. Here, we demonstrated that hypoxia inducible factor 1α induced increased expression of triggering receptor expressed on myeloid cells-1 (TREM-1) in TAMs, resulting in immunosuppression. Specifically, TREM-1-positive (TREM-1+ ) TAMs abundant at advanced stages of HCC progression indirectly impaired the cytotoxic functions of CD8+ T cells and induced CD8+ T-cells apoptosis. Biological and functional assays showed that TREM-1+ TAMs had higher expression of programmed cell death ligand 1 (PD-L1) under hypoxic environment. However, TREM-1+ TAMs could abrogate spontaneous and PD-L1-blockade-mediated antitumor effects in vivo, suggesting that TREM-1+ TAM-induced immunosuppression was dependent on a pathway separate from PD-L1/programmed cell death 1 axis. Moreover, TREM-1+ TAM-associated regulatory T cells (Tregs) were crucial for HCC resistance to anti-PD-L1 therapy. Mechanistically, TREM-1+ TAMs elevated chemokine (C-C motif) ligand 20 expression through the extracellular signal-regulated kinase/NF-κβ pathway in response to hypoxia and tumor metabolites leading to CCR6+ Foxp3+ Treg accumulation. Blocking the TREM-1 pathway could significantly inhibit tumor progression, reduce CCR6+ Foxp3+ Treg recruitment, and improve the therapeutic efficacy of PD-L1 blockade. Thus, these data demonstrated that CCR6+ Foxp3+ Treg recruitment was crucial for TREM-1+ TAM-mediated anti-PD-L1 resistance and immunosuppression in hypoxic tumor environment. Conclusion: This study highlighted that the hypoxic environment initiated the onset of tumor immunosuppression through TREM-1+ TAMs attracting CCR6+ Foxp3+ Tregs, and TREM-1+ TAMs endowed HCC with anti-PD-L1 therapy resistance.

Wu Q ，Zhou W ，Yin S ，Zhou Y ，Chen T ，Qian J ，Su R ，Hong L ，Lu H ，Zhang F ，Xie H ，Zhou L ，Zheng S ... -  《-》

Disruption of tumour-associated macrophage trafficking by the osteopontin-induced colony-stimulating factor-1 signalling sensitises hepatocellular carcinoma to anti-PD-L1 blockade.

In the tumour microenvironment, critical drivers of immune escape include the oncogenic activity of the tumour cell-intrinsic osteopontin (OPN), the expression of programmed death ligand 1 (PD-L1) and the expansion of tumour-associated macrophages (TAMs). We investigated the feasibility of targeting these pathways as a therapeutic option in hepatocellular carcinoma (HCC) mouse models. We analysed the number of tumour-infiltrating immune cells and the inflammatory immune profiles in chemically induced liver tumour isolated from wild-type and OPNknockout (KO) mice. In vitro cell cocultures were further conducted to investigate the crosstalk between TAMs and HCC cells mediated by OPN, colony stimulating factor-1 (CSF1) and CSF1 receptor (CSF1R). The in vivo efficacy of anti-PD-L1 and CSF1/CSF1R inhibition was evaluated in OPN overexpressing subcutaneous or orthotopic mouse model of HCC. The numbers of TAMs, as well as the expression levels of M2 macrophage markers and PD-L1 were significantly decreased, but the levels of cytokines produced by T-helper 1 (Th1) cells were upregulated in tumour tissues from OPN KO mice compared with that from the controls. In addition, we observed a positive association between the OPN and PD-L1 expression, and OPN expression and TAM infiltration in tumour tissues from patients with HCC. We further demonstrated that OPN facilitates chemotactic migration, and alternative activation of macrophages, and promotes the PD-L1 expression in HCC via activation of the CSF1-CSF1R pathway in macrophages. Combining anti-PD-L1 and CSF1R inhibition elicited potent antitumour activity and prolonged survival of OPNhigh tumour-bearing mice. Histological, flow cytometric and ELISA revealed increased CD8+ T cell infiltration, reduced TAMs and enhanced Th1/Th2 cytokine balance in multiple mouse models of HCC. OPN/CSF1/CSF1R axis plays a critical role in the immunosuppressive nature of the HCC microenvironment. Blocking CSF1/CSF1R prevents TAM trafficking and thereby enhances the efficacy of immune checkpoint inhibitors for the treatment of HCC.

Zhu Y ，Yang J ，Xu D ，Gao XM ，Zhang Z ，Hsu JL ，Li CW ，Lim SO ，Sheng YY ，Zhang Y ，Li JH ，Luo Q ，Zheng Y ，Zhao Y ，Lu L ，Jia HL ，Hung MC ，Dong QZ ，Qin LX ... -  《-》

TGF-β1-Induced SOX18 Elevation Promotes Hepatocellular Carcinoma Progression and Metastasis Through Transcriptionally Upregulating PD-L1 and CXCL12.

Hepatocellular carcinoma (HCC) is characterized by an immune-suppressive microenvironment, which contributes to tumor progression, metastasis, and immunotherapy resistance. Identification of HCC-intrinsic factors regulating the immunosuppressive microenvironment is urgently needed. Here, we aimed to elucidate the role of SYR-Related High-Mobility Group Box 18 (SOX18) in inducing immunosuppression and to validate novel combination strategies for SOX18-mediated HCC progression and metastasis. The role of SOX18 in HCC was investigated in orthotopic allografts and diethylinitrosamine/carbon tetrachloride-induced spontaneous models by using murine cell lines, adeno-associated virus 8, and hepatocyte-specific knockin and knockout mice. The immune cellular composition in the HCC microenvironment was evaluated by flow cytometry and immunofluorescence. SOX18 overexpression promoted the infiltration of tumor-associated macrophages (TAMs) and regulatory T cells (Tregs) while diminishing cytotoxic T cells to facilitate HCC progression and metastasis in cell-derived allografts and chemically induced HCC models. Mechanistically, transforming growth factor-beta 1 (TGF-β1) upregulated SOX18 expression by activating the Smad2/3 complex. SOX18 transactivated chemokine (C-X-C motif) ligand 12 (CXCL12) and programmed death ligand 1 (PD-L1) to induce the immunosuppressive microenvironment. CXCL12 knockdown significantly attenuated SOX18-induced TAMs and Tregs accumulation and HCC dissemination. Antagonism of chemokine receptor 4 (CXCR4), the cognate receptor of CXCL12, or selective knockout of CXCR4 in TAMs or Tregs likewise abolished SOX18-mediated effects. TGFβR1 inhibitor Vactosertib or CXCR4 inhibitor AMD3100 in combination with anti-PD-L1 dramatically inhibited SOX18-mediated HCC progression and metastasis. SOX18 promoted the accumulation of immunosuppressive TAMs and Tregs in the microenvironment by transactivating CXCL12 and PD-L1. CXCR4 inhibitor or TGFβR1 inhibitor in synergy with anti-PD-L1 represented a promising combination strategy to suppress HCC progression and metastasis.

Chen J ，Feng W ，Sun M ，Huang W ，Wang G ，Chen X ，Yin Y ，Chen X ，Zhang B ，Nie Y ，Fan D ，Wu K ，Xia L ... -  《-》

Targeting the YB-1/PD-L1 Axis to Enhance Chemotherapy and Antitumor Immunity.

Tumor cells can escape immune destruction in tumor chemoresistance, but the mechanism for this phenomenon remains unclear. Y-box binding protein 1 (YB-1), which is upregulated in chemoresistant tumor cells, plays a role in the acquisition of multidrug resistance. Here, we demonstrate that chemotherapy induced an immunosuppressive microenvironment in the tumor and induced immune evasion through YB-1-mediated programmed death-1 ligand 1 (PD-L1) upregulation. Examination of the YB-1 protein and mRNA showed an increase in YB-1 expression in hepatocellular carcinoma (HCC). High YB-1 expression negatively correlated with the overall survival of HCC patients. YB-1 expression positively correlated with PD-L1, and YB-1 induced PD-L1 expression by binding a PD-L1 promoter motif. YB-1 expression was upregulated in chemoresistant HCC cells, and YB-1 knockdown reversed chemoresistance via T-cell activation in the tumor microenvironment due to blocked PD-L1 expression. We also found that inhibition of the tumor immunosuppressive environment and immune evasion was accompanied by proliferation of functional cytotoxic CD8+ T cells and inhibition of myeloid-derived suppressor cells and regulatory T cells in the tumor environment. Our data indicate that targeting the YB-1 signaling axis, which simultaneously reverses both tumor immune evasion and multidrug resistance, may improve the antitumor response. This finding suggests a treatment modality against tumor chemoresistance.

Tao Z ，Ruan H ，Sun L ，Kuang D ，Song Y ，Wang Q ，Wang T ，Hao Y ，Chen K ... -  《-》

IL-6 promotes PD-L1 expression in monocytes and macrophages by decreasing protein tyrosine phosphatase receptor type O expression in human hepatocellular carcinoma.

We have previously discovered a relationship between the low expression of protein tyrosine phosphatase, receptor type O (PTPRO) in tumor-infiltrating T cells and immunosuppression. The aim of the present study was to investigate the relationship between decreased PTPRO and increased programmed death ligand 1 (PD-L1) in both the peripheral monocytes and tumor-infiltrating macrophages of human hepatocellular carcinoma (HCC). The expression and correlation of all the indices were explored in monocytes and tumor-infiltrating macrophages within both human and mice HCC. The mechanic regulations were studied by using both in vitro and in vivo studies. We found a significant decrease in PTPRO in HCC peripheral monocytes that was associated with increased PD-L1 expression in peripheral monocytes and tumor-associated macrophages (TAMs) in HCC. Monocyte PD-L1 and PTPRO therefore could serve as valuable prognostic indicators for post-surgery patients with HCC and were associated with increased T-cell exhaustion (Tim3+T cells). A depletion of PTPRO promoted PD-L1 secretion in both monocytes and macrophages through the JAK2/STAT1 and JAK2/STAT3/c-MYC pathways. Increased IL-6 expression was associated with activation of JAK2/STAT3/c-MYC and with decreased PTPRO expression through the STAT3/c-MYC/miR-25-3 p axis. Monocytes and TAMs showed significantly increased miR-25-3 p expression, which could target the 3' untranslated region of PTPRO. The miR-25-3 p expression positively correlated with serum IL-6 levels, but inversely correlated with PTPRO in HCC monocytes. IL-6/STAT3/c-MYC activation enhanced in vitro miR-25-3 p transcription and decreased PTPRO, while further promoting PD-L1 secretion. Adoptive cell transfer of c-MYC/miR-25-3 p-modified monocytes promoted tumor growth by downregulating PTPRO and causing a PD-L1-induced immunosuppression in an orthotopic tumor transplantation model. Increased serum IL-6 downregulated PTPRO expression in HCC monocytes and macrophages by activating STAT3/c-MYC/miR-25-3 p and by further enhancing PD-L1 expression through JAK2/STAT1 and JAK2/STAT3/c-MYC signaling.

Zhang W ，Liu Y ，Yan Z ，Yang H ，Sun W ，Yao Y ，Chen Y ，Jiang R ... -  《Journal for ImmunoTherapy of Cancer》