Insulin-like growth factor-I and transferrin mediate growth and survival of Chinese hamster ovary cells

The aim of this investigation was to elucidate the roles of insulin-like gr owth factor-I (IGF-I) and transferrin in the survival and proliferation of Chinese hamster ovary (CHO) cells upon withdrawal of serum. For this purpos e, we employed DNA analysis and now cytometry to compare CHO cell lines exp ressing either IGF-I alone or IGF-I and transferrin. The ability of cells t o cycle and the occurrence of apoptosis were monitored in these cells in se rum-free medium. These results indicate that IGF-I alone is able to maintai n the viability of CHO cells for an extended length of time in the absence of serum. Transferrin alone does not promote survival or proliferation. Onl y in the presence of both IGF-I and transferrin do cells survive and prolif erate. Therefore, in attached CHO cultures, IGF-I alone does not stimulate cell proliferation but is a requirement for growth in serum-free medium in cooperation with transferrin. We report on the dual role of IGF-I as a surv ival factor in CHO cells and its interlocking role with transferrin to stim ulate cell growth.