CXCR4 and lung cancer: However, since in adherent cell lines only a small percentage of cells expressed CXCR4 (median value 1.2%; min 0.7%, max 4.8%), we speculated that in lung cancer spheroids, highly enriched for CXCR4+ cells (median value 7.5%; min 2%, max 31.6%), treatment with peptide R might result in a more marked effect.