CDKN1B and neoplasm: Akt is a serine/threonine kinase and phosphorylates a host of cellular proteins, including GSK3α, GSK3β, FoxO transcription factors, MDM2, BAD and p27KIP1 to facilitate survival and cell cycle entry.34 As a lipid phosphatase, PTEN has been proved to suppress the activity of Akt kinase and even further restrain tumor progression.