Expression of PTEN and phosphorylated Akt in human cholesteatoma epithelium

We found a reduced PTEN and an increased phosphorylated Akt (p-Akt) expression in cholesteatoma epithelium when compared with retro-auricular (RA) skin. The negative correlation between cholesteatoma PTEN and p-Akt may suggest that cellular survival mechanisms may be involved in cholesteatoma epithelial hyperplasia.

The tumor suppressor PTEN regulates the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway and modulates cell cycle progression and cell survival. We hypothesized that PTEN might be involved in this pathway mechanism in cholesteatoma.

Western blotting and immunohistochemistry were used to examine the expression of PTEN and p-Akt in 16 cases of cholesteatoma and paired cases of RA skin.

In cholesteatoma, p-Akt expression was significantly higher than in RA skin, whereas PTEN expression was significantly lower in cholesteatoma when compared with skin (p < 0.05). Immunohistochemical analysis showed that weak PTEN immunoreactivity was observed in the nuclei of cholesteatoma epithelium, whereas strong PTEN immunoreactivity was detected in the nuclei of skin. Also, strong p-Akt immunoreactivity was observed in the cytoplasm of cholesteatoma epithelium, whereas very weak or no p-Akt immunoreactivity was observed in the RA skin. Furthermore, we found that a significant inverse correlation exists between PTEN and p-Akt expression (r = -0.796).