CDKN2C and breast cancer: Because both p18+/- and p18-/- mice spontaneously develop luminal type mammary tumors 17, 27, and either haploid or complete loss of p18 rescues the proliferative defect of Gata3+/- MECs, we combined p18-/- and p18+/- mice as the p18mt group, and p18-/-;Gata3+/- and p18+/-;Gata3+/- mice as the p18mt;Gata3+/- group.