Delayed mammary gland involution in MMTV-AKT1 transgenic mice.
AKT1/protein kinase Balpha is a protein-serine/threonine kinase that regulates multiple targets involved in cell survival and cell cycle progression in a variety of cell types including breast cancer cells. To explore the role of Akt1 in mammary gland function and tumorigenesis, transgenic mice were generated that express human AKT1 under the control of the MMTV promoter. Virgin transgenic mice did not exhibit a dominant phenotype, but upon cessation of lactation, a notable delay in involution occurred compared to age-matched non-transgenic mice. The delay in involution coincided with increased hyperplasia as evidenced by an increased number of binucleated epithelial cells and a marked elevation in cyclin D1 expression in mammary epithelium. The delayed involution phenotype corresponded to increased phosphorylation of Thr308 in AKT1 and Ser136 in BAD, but not phosphorylation of Ser21 in GSK-3alpha. There was no evidence of mammary dysplasia or neoplasia during the lifespan of multiparous transgenic mice. These data suggest that AKT1 is involved in cell survival in the lactating and involuting mammary gland, but that overexpression of AKT1 alone is insufficient to induce transformation.
Ackler
Scott
S
Department of Pharmacology, Georgetown University School of Medicine and Lombardi Cancer Center, Washington, DC 20007, USA.
Ahmad
Shakeel
S
Tobias
Christopher
C
Johnson
Michael D
MD
Glazer
Robert I
RI
D000818:Animals; D029681:Arabidopsis Proteins; D005260:Female; D007774:Lactation; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000473:pathology*; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000235:genetics*; D012016:Reference Values
D029681:Arabidopsis Proteins; D010940:Plant Proteins; D015221:Potassium Channels; C074500:AKT1 protein, Arabidopsis