By crossbreeding MALAT1 KO female mice with male mice with high incidence of mammary tumor (MMTV-PyMT mice), three filial generations were obtained (MMTV-PyMT Malat1+/+; MMTV-PyMT Malat1+/−; MMTV-PyMT Malat1−/− mice). This evidence concerns the gene MALAT1 and breast cancer.