Effect of human milk and epidermal growth factor on growth of human intestinal Caco-2 cells

BACKGROUND: Epidermal growth factor (EGF) in human milk has been thought to be mitogenic for cell growth. This study investigated the effects of human milk and EGF on the growth of human intestinal Caco-2 cells to determine whether the action occurred through regulation of the cell cycle or through c-jun expression.

METHODS: Cells were incubated with 5% human milk, 0.375 nmol/L EGF (relevant to EGF concentration in 5% human milk, 0.05 x EGF), 7.5 nmol/L EGF (1 x EGF), or 75 nmol/L EGF (10 x EGF). Cell numbers; cellular RNA, DNA, and protein concentrations; DNA content in the cell cycle, and expressions of c-Jun protein and mRNA were analyzed.

RESULTS: Cell numbers increased in the 1 x and 10 x EGF groups at 48 hours. Cellular RNA increased in the 5% human milk and 10 x EGF groups. DNA and protein contents increased in the 1 x and 10 x EGF groups. The 1 x and 10 x EGF groups increased DNA content in the G1 phase compared with the 5% human milk group at 24 hours. The greatest c-jun protein expression was 2.6, 1.4, 1.8, and 1.9 times the control, and the c-jun mRNA increased by 202%, 14%, 150%, and 181%, respectively, in the 5% human milk, 0.05 x, 1 x, and 10 x EGF groups.

CONCLUSIONS: In a dose-dependent manner, EGF stimulated intestinal growth in vitro, by increasing DNA content in the G1 phase and c-jun mRNA expression. However, low concentrations of human milk (5%) and its equivalent EGF did not affect cell growth.