The SV40 T-antigen induces premature apoptotic mammary gland involution during late pregnancy in transgenic mice.

Transgenic animals of the line 8 contain the WAP-SV-T transgene. Females of this line synthesise the SV40 T-antigen in mammary gland epithelial cells during pregnancy and the lactation period. All females are 'milk-less' and the offspring have to be nursed by foster mothers. The reason for this phenomenon is a premature apoptosis during late pregnancy. Nontheless a significant number of mammary epithelial cells escape apoptosis and all transgenic females devlop breast cancer after the first lactation period.