CDKN2A and breast cancer: It was interesting to note that unlike tumors from the MMTV-tTA TetO-KrasG12D model, the claudin-low mammary cancers in the EF1-tTA-based model consistently showed transcriptional repression of the Cdkn2a locus, the resulting lack of the p19Arf and p16Ink4a protein expression, and, in some cases, additional sporadic mutations in Trp53 (Suppl.