Differential growth requirements of serum factors (bovine serum albumin and low density lipoprotein) for normal and transformed human cells in a serum-free culture.

Serum-free culture is a useful method for identifying the growth requirements of normal cells of human origin and comparing them to the requirements 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 (SUSM-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.