Since A549 and A767 cells use distinctly different receptor(s) combinations to mediate migratory responses of CXCL12 and CXCL11 (see additional files 2 and 4), these findings further imply that the occurrence of combined effects does not depend on the functional organization of the CXCL12- and CXCL11-systems in individual tumor cells. This evidence concerns the gene CXCL12 and neoplasm.