Apoptosis induced by a human milk protein

Area of Science:

• Biochemistry
• Immunology
• Cell Biology

Background:

• Human milk provides nutrients and antimicrobial factors for infant immunity.
• The potential for milk components to affect host cells has been largely unexplored.
• While studying bacterial adherence, researchers observed milk's cytotoxic effect on cancer cells.

Purpose of the Study:

• To identify milk components with bioactivity towards host cells.
• To characterize the cytotoxic agent and its mechanism of action.
• To explore the implications for mucosal immunity and potential therapeutic applications.

Main Methods:

• Investigated human milk's effect on bacterial adherence to a lung cancer cell line.
• Analyzed milk components responsible for observed cytotoxicity.
• Assessed the Ca(2+)-elevating and apoptosis-inducing properties of identified components.
• Tested the selective cytotoxic activity against various cell types (transformed, embryonic, lymphoid, mature epithelial).

Main Results:

• A specific form of milk protein, multimeric alpha-lactalbumin, was identified as cytotoxic.
• Multimeric alpha-lactalbumin potently elevates intracellular calcium and induces apoptosis.
• This protein demonstrated selective cytotoxicity, killing transformed, embryonic, and lymphoid cells while sparing mature epithelial cells.
• The mechanism of apoptosis induction in transformed epithelial cells was analyzed.

Conclusions:

• Human milk contains multimeric alpha-lactalbumin, a potent inducer of apoptosis with selective cytotoxic activity.
• This finding suggests a novel role for milk in mucosal immunity through the elimination of abnormal host cells.
• Further research into multimeric alpha-lactalbumin's mechanism could lead to the development of new anticancer therapies.