For instance, a search for chemokine/chemokine receptor system in lung cancer showed that the interaction of CC-chemokine ligand 21 (CCL21) with its receptor CC-chemokine receptor 7 (CCR7) may help protect against tumor cell apoptosis through p-ERK-mediated increase of the Bcl-2/Bax ratio [29]. The gene discussed is CCL21; the disease is lung cancer.