Objective 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.
Design 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.
Results 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.
Conclusions 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.
- hepatocellular carcinoma
- tumor microenvironment
- immune checkpoint blockade
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YZ, JY, DX, X-MG and ZZ contributed equally.
Contributors YZ, JY, DX, XM-G and ZZ designed and performed the experiments, analysed data and wrote the manuscript; JH, LL and HL-J revised the manuscript; JH-L, YY-S, QL and YZ performed experiments and analysed data; CW-L and SO-L participated in the discussion and data interpretation; YZ and YZ analysed data; LX-Q, QZ-D and MC-H designed and supervised the entire project, designed the experiments, analysed data and wrote the manuscript.
Funding This work was supported by the following: the National Key Research and Development Program of China (2017YFC1308604); the National Key Basic Research Program of China (2014CB542101 and 2013CB910500); National Natural Science Foundation of China (81772563, 81672820, 81372647 and 81672365); and China National Key Projects for Infectious Disease (2012ZX10002-012 and 2017ZX10203207).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Not required.
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