CXCR4 and neoplasm: To examine the effect of CXCR4 knockdown on the invasion pattern of GL26-Cit tumors, we implanted 1000 GL26-Cit-Sh2CXCR4 cells or control GL26-Cit-NT cells into the striatum of NSG mice (N= 4/group) and examined the initial course of tumor progression (Figure 4A).