Experimental study of cancer metastasis

: Chemotherapeutic assays, using nitrosoureas, performed on tumor bearing rats have shown a regression of local tumor, accompanied with an amplification of pulmonary metastases, demonstrating that the treatment of metastasis differs from the treatment of a local tumor. Cells organizing a tumor are heterogeneous for their drug resistance, and for a series of properties including their ability to form metastasis. Metastatic cells have to leave the tumoral tissue, to traverse biological barriers, to resist to immune system, to implant and growth in the target tissue. An experimental model has been used to characterize metastatic cells. Metastatic potential has been defined as the ability to invade lungs. Highly metastatic cloned cell lines, such as subline 6, were strongly stimulated to proliferate by EGF, expressed fibronectin, actively degraded the extracellular matrix, rapidly attached to endothelial vascular cells, and resisted to natural killer lymphocytes. Inversely, weakly metastatic lines, such as subline 8, were preferentially stimulated by FGF and EDGF, poorly expressed fibronectin, did not degrade extracellular matrix, slowly attached to vascular cells, and were killed by NK lymphocytes. Studies on a large series of clones showed a diversity between them, and that no one property was determinant. Modulation of these characters by growth factors, hormones and immune state of the host is discussed, and leads to conclude that the expression of metastatic potential of a tumor depends on genetically defined characters and also on influences excerted by the host.