Growth rates of a human colon adenocarcinoma cell line are regulated by the milk protein alpha-lactalbumin.

The whey protein alpha-lactalbumin, derived from human milk, has been shown to inhibit proliferation of mammary epithelial cells and rat kidney cells. We have shown that bovine alpha-lactalbumin also has antiproliferative effects in human colon adenocarcinoma cell lines. During a 5-day dose-dependent growth study, bovine alpha-lactalbumin was added to Caco-2 or HT-29 monolayers in amounts from 5 to 35 microg/mL. Low concentrations of alpha-lactalbumin (10-25 microg/mL) stimulated growth during the first 3 to 4 days. After growing for 4 days, proliferation ceased and viable cell numbers decreased dramatically in the alpha-lactalbumin-treated cultures, suggesting a delayed initiation of apoptosis. This experiment demonstrates the acute bioactive effects of small concentrations of alpha-lactalbumin, compared with the high concentrations of other proteins in the media. These results suggest that alpha-lactalbumin in milk may promote health by inhibiting growth of potential cancer cells. Further studies will identify the role of calcium in the bioactivity of alpha-lactalbumin.