Enhanced invasiveness of tumour cells after host exposure to heavy metals.

The invasiveness of tumour cells to heavy metal-exposed host cells or tissues was investigated. Human fibrosarcoma cell invasion of heavy metal-treated fibroblast or endothelial cell was enhanced in a treatment-time-dependent manner although tumour cell attachment to host cells was not affected. This enhancement was correlated with an increase in metallothioneins in the cytosol of fibroblasts or endothelial cells. Mouse melanoma cell invasion of organ samples obtained from syngeneic mice who had been administered heavy metals was also enhanced. The results suggest that heavy metal-induced metallothioneins serve as a host-derived factor in malignant disease and closely relate to metastasis.