TP53 and ovarian carcinoma: On the other hand, p53 can conversely regulate Akt activity by promoting the transcription of the PIP3 inhibitor PTEN, enhancing p53 protein level and activation as well as negatively regulating the expression of PI3K.97,98 We have observed that Akt plays an important role in the regulation of PPM1D protein stability and enhancement of its content in response to DNA damage in ovarian carcinoma cells.