Figure 3.

S1P participates in regulating cancer‐related bone metastasis in bone marrow and tumour microenvironment. In tumour microenvironment, apoptotic tumour cell‐released S1P is responsible for the polarization of M2‐MΦs in a S1PR1‐dependent manner. IL‐4 and IL‐10 are formed by M2 macrophages, which are crucial for tumour cell evasion, whereas in bone marrow, metastasized tumour cells colonized to bone surface, and S1P (secreted by osteoblasts) promotes their proliferation depending on S1PR1 signalling