Regulation of expression of the cell adhesion receptors, integrins, by recombinant human interleukin‐1β in human osteosarcoma cells: Inhibition of cell proliferation and stimulation of alkaline phosphatase activity

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Abstract
Recombinant human interleukin-1β, a mediator of osteoblastic cell function, was found to regulate the expression of the cell adhesion receptors, integrins, on human osteosarcoma cells. Interleukin-1β (IL-1β) at picomolar concentrations, specifically elevated approximately six- to tenfold the expression of the β1 subunit and its associated α subunits, but not the related vitronectin receptor, within 20 hours. Integrin β1 messenger RNA levels were elevated within 6 hours and peaked to tenfold higher levels after 20 hours exposure to IL-1β in two human osteosarcoma cell lines. The increase in the cell-surface β1 integrins resulted in a stronger binding of the IL-1β-treated cells to fibronectin. Cell growth was also inhibited by IL-1β cell morphology was altered, and IL-1β-treated cells expressed an approximately two- to threefold higher alkaline phosphatase. This increase in alkaline phosphatase activity was found to be independent of the inhibition of cell proliferation. These data indicate that the β1 integrin family of cell surface receptors is a target for regulation by IL-1β which also regulates cell proliferation and the expression of the osteoblastic phenotype in human osteosarcoma cells.