Chemokine receptor CCR4 and its ligands CCL17 and CCL22 are used as markers for the identification and/or staging of cancer. The level of CCR4, CCL17 and CCL22 are found to increase during malignant tumour progression. CCR4, CCL17 and CCL22 are used as markers for the stratification of cancer patients according to their suitability for treatment with anti-cancer agents. Information of diagnostic character is provided by measuring the level of one or more of CCR4, CCL17 and CCL22 present in a patient sample. Methods of treatment of cancer patients which agents that modulate the activity of CCR4, CCL17 and CCL22. Methods of screening for agents which modulate the biological activities of CCR4, CCL17 and CCL22 provide anti-cancer agents.
