PDGFB and neoplasm: Then, the bone marrow vascular niches provide fertile soil for an interaction between tumor cells and bone ECs, which promotes metastatic ability and supports disseminated tumor cell (DTC) reactivation.250,251 Specifically, type H capillaries along with PDGFR-β+ perivascular cells express high levels of PDGF-B, providing tissue-specific instructive vascular niches for long-term maintenance of HSCs and DTCs.252,253 In addition, blood flow decline within the niches is generally conducive to interactions between tumor cells and skeletal ECs, thus leading to macrometastasis.