FOXL1 and in situ carcinoma: To further validate an association between MMTV CIS genes and mouse mammary tumor progression, three low frequency MMTV CIS genes (Phf19, Foxl1 and Sdc2) were selected for further study to determine whether their expression confers on mammary epithelial cells the capability for anchorage independent growth and/or invasion on mammary epithelial cells.