Tumor cell entry into the lymph node is controlled by CCL1 chemokine expressed by lymph node lymphatic sinuses

Area of Science:

• Oncology
• Immunology
• Cell Biology

Background:

• Lymphatic vessels are traditionally viewed as passive conduits for tumor cell metastasis.
• Tumor cell entry into lymph nodes is believed to be driven solely by lymph flow.

Purpose of the Study:

• To investigate the active mechanisms governing tumor cell entry into lymph nodes.
• To identify molecular players involved in regulating metastasis to lymph nodes.

Main Methods:

• Analysis of human and mouse tissues for CCL1 and CCR8 expression.
• In vitro migration assays using tumor cells and lymphatic endothelial cells (LECs).
• In vivo studies using a mouse metastasis model with CCR8 inhibition.

Main Results:

• CCL1 is present in lymph node lymphatic sinuses, and its receptor CCR8 is expressed by melanoma cells.
• Blocking CCL1 or CCR8 inhibited tumor cell migration to LECs; CCL1 promoted migration of CCR8(+) tumor cells.
• Inhibition of CCR8 significantly reduced lymph node metastasis in mice, arresting tumor cells before lymph node entry.

Conclusions:

• Lymph node lymphatic sinuses actively control tumor cell entry, requiring active migration.
• The CCL1-CCR8 signaling axis is a novel mechanism regulating metastasis to lymph nodes.
• LECs and the CCL1-CCR8 pathway represent a critical checkpoint for metastatic tumor cells entering lymph nodes.