PTEN and cancer: In these cancer patient cell lines, we did not observe any SL interaction between EXT1 and Notch1, or EXT1 and the Notch1 ubiquitin ligase encoding gene FBXW7. However, EXT1 and Notch1 do synthetically interact with several shared genes, including important oncogenes: KRAS, PTEN, BRCAC2, and MYC (fig.