Differentiation of Dunn osteosarcoma cells in response to dibutyryl cyclic 3′,5′-adenosine monophosphate

We investigated the effects of dibutyryl cyclic adenosine 3′,5′-monophosphate (Bt₂cAMP) on the differentiation of Dunn osteosarcoma cells. Flow-cytometric analysis and DNA synthesis assay showed that Bt₂cAMP decreased the cell population in the S phase in a time- and dose-dependent manner. Also, the cells showed distinct morphological and functional alterations: the cell morphology changed to a fibroblast-like appearance with long and thin protoplasmic processes, the knobs or blebs on both the cell membrane and nuclear membrane disappeared and the intracellular alkaline phosphatase activity increased. Moreover, Bt₂cAMP-treated cells secreted a large quantity of fibronectin, which was deposited on the extended cell surface in the culture medium. Thus, Dunn osteosarcoma cells are differentiated morphologically and functionally by Bt₂cAMP, and might be transformed to benign precursor cells.