Expression of PDK1 in malignant pheochromocytoma as a new promising potential therapeutic target.

PURPOSE: Phosphoinositide-dependent kinase 1 (PDK1) is highly expressed in many solid tumors. And several studies have demonstrated that PDK1 has been an emerging and promising target for anti-cancer therapies. However, the role of PDK1 has not been studied so far in malignant pheochromocytoma (PCC). METHODS: In this study, immunohistochemical staining was performed to investigate the protein level of PDK1 in 63 PCC tissue samples, of which 49 were benign and 14 were malignant. In addition, we evaluated the effect of inhibition of PDK1 with siRNA on cell growth, apoptosis and invasive capacity in PC12 cells and identified the underlying mechanisms. RESULTS: We found that PDK1 was overexpressed in malignant PCC tissues, and knockdown of PDK1 with siRNA significantly inhibited cell proliferation, increased apoptosis induction, and attenuated cell migration and invasive capacity in PC12 cells. We also showed that knockdown of PDK1 significantly reduced the phosphorylation of Akt at threonine 308 (p-Akt T308) but did not alter the serine phosphorylation of Akt on the S473 site (p-Akt S473). Furthermore, we found that the p-Akt expression was noticeably decreased after knockdown of PDK1, but the t-Akt expression did not show a significant decrease. CONCLUSION: We have demonstrated for the first time that PDK1 is overexpressed in human malignant PCC and plays an important role in the malignant biological behaviors of PC12 cell. Specifically, we have revealed that knockdown of PDK1 could attenuate activation of the Akt signaling. These data suggest that PDK1 could be a new promising potential therapeutic target in human cancer treatment for malignant PCC.