Periostin: a potent chemotactic factor for recruiting tumor-associated macrophage

Glioblastoma (GBM) is the most common malignant primary brain tumor with a low five-year survival rate. Evidence from experimental and clinical studies indicates that glioma stem cells (GSCs) contribute to GBM tumor growth, therapeutic resistance and relapse (Bao et al., 2006; Gilbertson and Rich, 2007). GSCs are enriched in a unique microenvironment known as the perivascular niche. Interestingly, a large number of tumor-associated macrophages (TAMs) are also distributed in the perivascular niche, indicating that crosstalk between GSCs and TAMs may have a critical role in GBM tumor progression. TAMs are abundant in most solid tumors and contribute to tumor progression in several ways, such as promoting invasion, angiogenesis and immunosuppression; however, the molecular link between TAM recruitment and GSCs has remained generally unclear. Writing in Nature Cell Biology, Zhou et al. provide new insights into where and how TAMs are recruited and educated by GSCs in GBMs (Zhou et al., 2015) (Fig. 1).