Vessel invasion by tumour cells. An ultrastructural study

Area of Science:

• Oncology
• Cell Biology
• Pathology

Background:

• Tumor cell intravasation is a critical step in metastasis.
• The mechanisms of fibrosarcoma cells breaching intact endothelium are not fully understood.

Purpose of the Study:

• To elucidate the ultrastructural mechanisms of fibrosarcoma cell invasion through peri-tumoral hepatic veins.
• To describe the immediate interactions between invading tumor cells and blood components.

Main Methods:

• Transmission electron microscopy was used to examine fibrosarcoma cells invading liver veins in syngeneic mice.
• Detailed ultrastructural analysis focused on tumor cell-endothelial cell interactions and subsequent blood cell responses.

Main Results:

• Fibrosarcoma cells degraded the endothelial basement membrane.
• Tumor cells entered the bloodstream by opening endothelial cell junctions or causing endothelial cell disintegration.
• Platelets and polymorphonuclear leukocytes (neutrophils and eosinophils) adhered to invading tumor cells.
• Polymorphonuclear leukocytes showed signs of degranulation and membrane damage upon contact with tumor cells.
• Some polymorphonuclear leukocytes were engulfed by tumor cells, while others appeared to penetrate tumor cell cytoplasm.

Conclusions:

• Fibrosarcoma cells utilize multiple mechanisms to breach intact vascular endothelium.
• Immediate interactions with platelets and leukocytes suggest complex host responses to tumor cell invasion.
• These findings provide insights into the early stages of cancer cell dissemination.