Inhibition of cell attachment by selenite.

Brief pre-exposure of HeLa cells to micromolar concentrations of selenite resulted in a dose-dependent decrease in the rate of their subsequent attachment to a solid matrix (tissue culture dish). Similar low concentrations of selenite also inhibited colony formation, but only when the cells were exposed prior to their attaching to the dish, not when they were exposed after attachment. This indicates that inhibition of cell proliferation by selenite requires exposure to higher concentrations for longer periods of time. In contrast, selenate, selenomethionine, selenocystine, and sulfite did not affect cell attachment, even at significantly higher concentrations. Thus, the inhibition of cell attachment is a specific effect of selenite. Selenite also inhibited the attachment of cells to bacteriological dishes coated with fibronectin, laminin, or collagen, proteins that are components of the extracellular matrix. There was no inhibition when the tissue culture dishes or the protein-coated dishes were pre-exposed to selenite. There was also no inhibition when the cells were exposed to selenite during the attachment process. Thus, pre-exposure of the cells to selenite was necessary for inhibition of attachment. Since cell attachment has been shown to be an important early step in tumor cell invasion and metastasis, these results suggest a novel mechanism of the anticarcinogenic effect of selenite: inhibition of the attachment of tumor cells to the extracellular matrix.