Comparison of serum dependency of transformed insect cell lines of different degrees of malignancy

The rate of growth of four malignantly transformed insect cell lines was correlated with their dependence on serum in the medium. Highly malignant lines, in terms of LT50for insects injected with the cells, were less affected in vitro by low levels of serum than were the lines that killed more slowly in vivo. The two most malignant lines could be adapted to growth in medium without serum, whereas the others could not.