Abstract
Serum-free culture is a useful method for identifying the growth requirements of normal cells of human origin and comparing them to the re-quirements of transformed human cells. We examined differential growth requirements of serum factors (bovine serum albumin (BSA) and low density lipoprotein (LDL)) on normal (HEL), Co-60 gamma ray-transformed (CT-1) and 4-nitroquinoline 1-oxide-transformed (SUS M-1) human fibroblast cells in the absence of serum. A decreased requirement for serum was closely related to a decreased requirement for BSA in both types of transformed cells. The growth rate and saturation density of HEL and CT-1 cells grown in serum-free medium supplemented with the optimal concentrations of BSA were almost equal to the rates of cells grown in serum-supplemented medium. When BSA alone was added to the serum-free medium it did not support the continuous growth of SUSM-1 cells because of cellular detachment. An addition of LDL to serum-free cultures not only promoted the moderate growth of HEL cells, it promoted the continuous growth of SUSM-1 cells as well. In contrast, LDL was not required for the optimal growth of CT-1 cells. Transformed human cells specifically had reduced quantitative and qualitative growth requirements for one or more serum factors.
