A novel peptide targeting CCR7 inhibits tumor cell lymph node metastasis.

Lymph nodes are the most common metastasis sites for tumor cells, which are intimately linked to patient prognosis. It has been reported that cancer cells can upregulate CC Chemokine Receptor 7 (CCR7) expression and hijack its normal functions, enabling them to migrate along the gradient of CCL19 and CCL21 toward the lymph nodes and colonies as the initial stage of distant metastasis. In tumor patients, the metastatic tumor in the lymph nodes exhibited higher expression of CCR7, as well as inhibitory immune checkpoints PD-1, LAG-3, and TIM-3 compared to the primary tumors with the analysis of TCGA and GEO databases. Also, in mouse tumor model, tumor cells with elevated CCR7 expression were more susceptible to develop popliteal lymph node metastasis. Subsequently, we successfully identified a CCR7 binding peptide TC6 by phage display biopanning, which specifically blocks the interaction of CCR7/CCL19 and CCR7/CCL21. Further, the D-amino acids were introduced to substitute the N- and C-terminus of TC6 peptide to obtain the proteolysis-resistant TC6-D3 peptide, which decreased tumor cell migration in vitro via ERK1/2 pathway and inhibited tumor growth and lymph nodes metastasis in vivo, as well as effectively restored T cells cytotoxicity in both primary tumors and lymph nodes. In conclusion, CCR7 promoted tumor cell metastasis to lymph node and inhibited the anti-tumor immune responses in lymph nodes. Specific blockade of the CCR7 pathway with TC6-D3 peptide can significantly reduce lymph node tumor burden, promoting CD8(+) T cell infiltration in primary tumors, meanwhile, enhancing anti-tumor immune responses in lymph nodes.