By hybridizing ERCC6L conditional knockout mice with MMTV-PyMT mice (a mouse model in which specific expression of polyomavirus middle T antigen (PyMT) driven by the mouse mammary virus MMTV could rapidly facilitate multifocal mammary tumor formation), it was found that ERCC6L deficiency can significantly inhibit the occurrence and development of mammary gland tumors. Here, ERCC6L is linked to breast cancer.