Western blot analysis showed that phosphoinositide - dependent protein kinase 1, the upstream kinase that phosphorylates Akt, and several phosphatases (phosphatase and tensin homolog deleted on chromosome 10, protein phosphatase 1, and protein
phosphatase 2A), known as negative regulators of the PI3K / Akt signaling pathway, were unchanged upon VPA treatment (Supplemental Fig. 4E), indicating that VPA might act on Akt directly.