CXCR4 and neoplasm: We then used lentiviraus-CXCR-4-shRNA to silence CXCR-4 expression in Cal 27 (Figure 4B) and HN 30 (Supplemental Fig. 1B) cell lines and found that pDC-CM-mediated tumor cell proliferation was significantly inhibited in CXCR-4-silenced cells, as reflected by the CCK-8 (Figure 4C; Supplemental Fig. 1C) and colony formation (Figure 4D; Supplemental Fig. 1D) assays.