Our findings that the pharmacological inhibition and genetic suppression of Vav2 also inhibited the CCL2-mediated activation of Rac1 in human HNSCC cells in a CCR4-dependent manner, indicating that Vav2 plays a critical role in the activation of Rac1 in HNSCC cells treated with CCL2. The gene discussed is CCR4; the disease is head and neck squamous cell carcinoma.