Serum signaling factors and spheroids

Normal epithelial cells grow as a sheet-like structure. Upon malignant tran sformation, epithelial cells grow as multicell aggregates. Adopted in tissu e culture, most tumor cells revert to adherent monolayer. In tissue culture , as early as 1958, anchorage-independent multicellular spheroid cancer cel ls have been shown to revert to adherent monolayer in response to extracell ular serum signaling factors. Such serum signaling factors have not yet bee n characterized. Recent studies reveal that the conversion of adherent mono layer to multicellular spheroids is also mediated by serum signaling factor s such as carcinoembryonal antigen, inlerferon-gamma, insulin-like growth f actor-II, heregulin beta1 and plasmin. The reports provide a new approach t o investigate the regulatory system of tumor cell growth pattern as well as the effect of the change in growth pattern on various cellular functions. (C) 2000 Published by Elsevier Science Ireland Ltd.