Functional visualization of NK cell-mediated killing of metastatic single tumor cells

Area of Science:

• Immunology
• Cancer Biology
• Microscopy

Background:

• Natural killer (NK) cells are crucial for limiting metastatic spread by targeting tumor cells in the lungs.
• The mechanisms by which cancers evade NK cell-mediated destruction to establish metastatic lesions remain poorly understood.

Purpose of the Study:

• To investigate how tumor cells evade NK cell immune surveillance in the lung during early metastasis.
• To quantitatively analyze the dynamic interactions between NK cells and tumor cells in vivo.

Main Methods:

• Utilized ultra-sensitive bioluminescence imaging and intravital two-photon microscopy.
• Employed genetically encoded biosensors to monitor NK cell activity and tumor cell interactions.
• Quantified NK-tumor cell encounters, tumor cell death, and NK cell ERK activation over time.

Main Results:

• NK cells effectively eliminated disseminated tumor cells within the first 24 hours of arrival in the lung.
• After 24 hours, NK cell-mediated tumor cell killing decreased significantly, with nearly all interactions resulting in tumor cell survival.
• A marked decrease in NK cell ERK activation upon tumor cell encounter correlated with the downregulation of the CD155 ligand on tumor cells.

Conclusions:

• Tumor cells evade NK cell immune surveillance within 24 hours of lung metastasis.
• Downregulation of the CD155 ligand is a key mechanism for tumor cell escape from NK cell-mediated killing.
• This study reveals critical parameters of NK cell immune surveillance in the lung during early metastatic processes.