The 24p3 gene is induced during involution of the mammary gland and induces apoptosis of mammary epithelial cells

To understand the molecular mechanism of mammary gland involution we identified involution-induced clones by differential screening of a mouse mammary gland cDNA library. Characterization of clones by sequencing and Northern analysis showed that expression of 24p3 was induced during involution of the mammary gland. RNA in situ hybridization showed that it was mainly expressed in the secretory epithelial cells surrounding the lumen of the mammary gland alveoli. Induction of 24p3 was also observed in apoptotic HC11 mammary epithelial cells under serum starvation. In these cells, dexamethasone increased 24p3 gene expression four-fold. Transient expression of 24p3 increased the percentage of apoptotic cells 3- to 4-fold over a period of 3 days after transfection. This study provides evidence that overexpression of 24p3 gene can induce apoptosis of mammary epithelial cells.