SIX1 and neoplasm: Interestingly, it was predicted that the promoter region of PI3K (p110α) contains putative Six1 binding sites, suggesting that Six1 may play a regulatory role on PI3K. However, we found that transfecting myoblasts with pEGFP-duSix1 in combination with LY294002 treatment did not change the expression of PI3K and Akt. Furthermore, the PI3K/Akt pathway is mainly negatively regulated by many other anti-oncogenes, such as PTEN (Choi et al., 2002), CTMP (Mairaet al, 2001) and PHLPP (Gao et al, 2005), to inhibit tumor cell proliferation.