CXCL12 and central nervous system cancer: As shown in Figure 4B, glioma cell lines did not express CXCR3, CXCR4, CXCR6, CX3CR1, but high levels of CXCR7, which is a receptor for CXCL11 and CXCL12 and can mediate G-protein independent signals via arrestin (Odemis et al., 2012).