Induction of Morphological Changes of Cells by Cyclic SUMMARY A culture line of mouse glioblastoma cells changed morphologically to differentiated astrocyte-like cells when cultured in medium with dibutyryl cyclic adenosine mono phosphate and theophylline. Morphological alteration

also reported (35). Previously, we reported the establishment of a culture line of mouse glioblastoma cells with tumorigenicity in mice (30). These cells were obtained from a transplantable tumor in vivo derived in turn from a tumor induced in the brain of a C57BL mouse by methylcholanthrene (32). These tumor cells showed biochemical markers of glia cells, like C type aldolase, which is specific to nerve tissue (1 8, 20) and glioma cells (17, 31, 40), and like S-lOO protein, which is specific to glia and glioma cells (1, 23). However, they did not show the morphology of normal mature glia cells either in vivo or in culture. In culture, they sometimes developed several short cytoplasmic processes, but usually they grew as flat cells without processes. Thus they cannot be identified as of glial origin from their morphology alone. This report describes the morphological alteration of these cultured mouse glio blastoma cells into cells like mature glia, induced by DBcAMP. The value of this type of culture system for studies on differentiation of glia cells is discussed.