Real-time imaging reveals the single steps of brain metastasis formation

Area of Science:

• Oncology
• Neuroscience
• Cell Biology

Background:

• Brain metastasis is a frequent and often fatal complication of cancer.
• Understanding the in vivo dynamics of metastasis is crucial for developing effective therapies.

Purpose of the Study:

• To visualize and analyze the real-time, in vivo steps of brain metastasis formation.
• To investigate the differential mechanisms of metastasis and dormancy in melanoma and lung cancer.
• To evaluate the efficacy of vascular endothelial growth factor-A (VEGF-A) inhibition on metastasis progression.

Main Methods:

• Utilized multiphoton laser scanning microscopy for in vivo imaging of cancer cell behavior.
• Tracked individual metastasizing cancer cells in mouse brains over extended periods (minutes to months).
• Observed interactions between cancer cells and blood vessels, including arrest, extravasation, and perivascular growth.

Main Results:

• Identified essential steps: vascular arrest, extravasation, microvessel contact, and perivascular growth (vessel cooption for melanoma, angiogenesis for lung cancer).
• Observed tumor-type-specific differences in inefficient metastatic steps.
• Found that only single perivascular cancer cells exhibited long-term dormancy, with some showing continuous movement.
• VEGF-A inhibition successfully induced long-term dormancy in lung cancer micrometastases by blocking angiogenic growth.

Conclusions:

• Real-time in vivo imaging provides novel insights into brain metastasis establishment and evolution.
• Distinct mechanisms govern melanoma and lung cancer brain metastasis.
• Targeting VEGF-A is a potential strategy to induce dormancy and prevent the growth of lung cancer brain metastases.