A novel mouse model for liver metastasis of prostate cancer reveals dynamic tumour‐immune cell communication

OBJECTIVES: In contrast to extensive studies on bone metastasis in advanced prostate cancer (PCa), liver metastasis has been under‐researched so far. In order to decipher molecular and cellular mechanisms underpinning liver metastasis of advanced PCa, we develop a rapid and immune sufficient mouse model for liver metastasis of PCa via orthotopic injection of organoids from PbCre(+); rb1(f/f);p53(f/f) mice. MATERIALS AND METHODS: PbCre(+);rb1(f/f);p53(f/f) and PbCre(+);pten(f/f);p53(f/f) mice were used to generate PCa organoid cultures in vitro. Immune sufficient liver metastasis models were established via orthotopic transplantation of organoids into the prostate of C57BL/6 mice. Immunofluorescent and immunohistochemical staining were performed to characterize the lineage profile in primary tumour and organoid‐derived tumour (ODT). The growth of niche‐labelling reporter infected ODT can be visualized by bioluminescent imaging system. Immune cells that communicated with tumour cells in the liver metastatic niche were determined by flow cytometry. RESULTS: A PCa liver metastasis model with full penetrance is established in immune‐intact mouse. This model reconstitutes the histological and lineage features of original tumours and reveals dynamic tumour‐immune cell communication in liver metastatic foci. Our results suggest that a lack of CD8(+) T cell and an enrichment of CD163(+) M2‐like macrophage as well as PD1(+)CD4(+) T cell contribute to an immuno‐suppressive microenvironment of PCa liver metastasis. CONCLUSIONS: Our model can be served as a reliable tool for analysis of the molecular pathogenesis and tumour‐immune cell crosstalk in liver metastasis of PCa, and might be used as a valuable in vivo model for therapy development.