, Volume 167, Issue 3–4, pp 134–144

Identification of human milk α-lactalbumin as a cell growth inhibitor

  • M. P. Thompson
  • H. M. FarrellJr.
  • Sanjeeva Mohanam
  • Sue Liu
  • W. R. Kidwell
  • M. P. Bansal
  • R. G. Cook
  • D. Medina
  • Claire E. Kotts
  • Mozeena Bano

DOI: 10.1007/BF01403376

Cite this article as:
Thompson, M.P., Farrell, H.M., Mohanam, S. et al. Protoplasma (1992) 167: 134. doi:10.1007/BF01403376


A growth inhibitory protein, mammary inhibitory activity (MIA), was purified to apparent homogeneity from human milk. At concentrations of 5 to 10 ng/ml, the factor inhibited the growth of mammary epithelial cells by 30–80% and also inhibited the growth of normal rat kidney cells. Whereas the cell division of normal human mammary epithelium in primary culture was inhibited by MIA, cell division by fibroblasts from the same tissues was unresponsive. Inhibition was dose and time dependent and readily reversed when MIA was removed. MIA also inhibited growth in culture for three cell lines. The growth inhibitory protein migrated as a 14 kDa protein under reducing conditions on polyacrylamide gels in the presence of sodium dodecyl sulfate. The apparent isoelectric point was pI 5.0. The amino acid composition of MIA resembled that of α-lactalbumin, and sequence analysis of the N-terminal region comprising residues 1–24 and an isolated peptide were identical with the N-terminal and residues 66–81 of human α-lactalbumin. In addition, MIA was active in the lactose synthase system. The results strongly suggest that MIA and α-lactalbumin are identical proteins. Consistent with these results, α-lactalbumin preparations from several mammalian species, including human, goat, cow and camel, were all found to be growth inhibitory for cultured mammary epithelial cells. The inhibitory activity associated with human α-lactalbumin was destroyed by digestion with pepsin or chymotrypsin, by carboxymethylation of cysteine, or by cleavage of methionine 90 following cyanogen bromide treatment. The results raise the possibility that during lactation α-lactalbumin, a product of mammary cell differentiation, could be a physiologically relevant feed-back inhibitor of mammary cell growth and perhaps of other cell types as well.


Milk protein Mammary cells Cell growth Inhibition 



mammary inhibitory activity


mammary derived growth inhibitor


alpha lactalbumin


human α-lactalbumin


normal rat kidney


improved minimal essential medium


Dulbecco's modified Eagles medium


fetal calf serum


epidermal growth factor


transforming growth factor β


cyanogen bromide


sodium dodecyl sulfate




non-denaturing polyacrylamide gel electrophoresis


trichloroacetic acid


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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • M. P. Thompson
    • 8
  • H. M. FarrellJr.
    • 8
  • Sanjeeva Mohanam
    • 1
  • Sue Liu
    • 2
  • W. R. Kidwell
    • 3
  • M. P. Bansal
    • 4
  • R. G. Cook
    • 5
  • D. Medina
    • 4
  • Claire E. Kotts
    • 6
  • Mozeena Bano
    • 7
  1. 1.Cancer Biology Division, School of Biological SicencesMadurai Kamaraj UniversityMaduraiIndia
  2. 2.Surgery Branch, National Cancer InstituteNIHBethesda
  3. 3.Cellco Advanced Bioreactors, Inc.Kensington
  4. 4.Department of Cell BiologyBaylor College of MedicineHouston
  5. 5.Howard Hughes Medical Institute and Department of Microbiology and ImmunologyBaylor College of MedicineHouston
  6. 6.Department of Medicinal and Analytical ChemistryGenentech Inc.South San Francisco
  7. 7.Lombardi Cancer Research CenterGeorgetown UniversityWashington, D.C.
  8. 8.ARS, Eastern Regional Research CenterUSDAPhiladelphiaUSA

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