Autocrine and paracrine loops between cancer cells and macrophages promote lymph node metastasis via CCR4/CCL22 in head and neck squamous cell carcinoma

Lymph node metastasis is a poor prognostic factor for patients with head and neck squamous cell carcinoma (HNSCC). However, its molecular mechanism has not yet been fully understood. In our study, we investigated the expression of CCR4 and its ligand CCL22 in the HNSCC tumor microenvironment and found that the CCR4/CCL22 axis was involved in lymph node metastasis of HNSCC. CCR4 was expressed in 20 of 31 (64.5%) human tongue cancer tissues, and its expression was significantly correlated with lymph node metastasis (p < 0.01) and lymphatic invasion (p < 0.05). CCR4 was expressed in three of five human HNSCC cell lines tested. CCR4⁺ HNSCC cells, but not CCR4^- cells, showed enhanced migration toward CCL22, indicating that functional CCR4 was expressed in HNSCC cell lines. CCL22 was also expressed in cancer cells (48.4% of tongue cancer tissues) or CD206⁺ M2-like macrophages infiltrated in tumors and draining lymph nodes. CCL22 produced by cancer cells or CD206^high M2-like macrophages increased the cell motility of CCR4⁺ HNSCC cells in vitro in an autocrine or paracrine manner. In the mouse SCCVII in vivo model, CCR4⁺ cancer cells, but not CCR4 ^- cells, metastasized to lymph nodes which contained CCL22 producing M2-like macrophages. These results demonstrate that lymph node metastasis of CCR4⁺ HNSCC is promoted by CCL22 in an autocrine or M2-like macrophage-dependent paracrine manner. Therefore, the CCR4/CCL22 axis may be an attractive target for the development of diagnostic and therapeutic strategies for patients with HNSCC.