Her2 modulates Cdk5-dependent AR activation and cell proliferation in human prostate cancer

• Main Authors: Fu-Ning Hsu, 許馥甯
• Other Authors: 林赫
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/81226432934029357912

碩士 === 國立中興大學 === 生命科學系所 === 95 === Cyclin-dependent kinase 5 (Cdk5) is a unique member of Cdk family without involving cell cycle regulation. The functions of Cdk5 and its neuron-specific activator p35 were extensively explored in both neuronal development and neurodegenerative disease in recent decades. However, the roles of Cdk5 are still unclear in human cancers and need to be further investigated. Our results demonstrated that expression of Cdk5 and p35 protein was present in LNCaP cells (human prostate cancer cell line) which harbored expression of androgen receptor (AR). AR is a ligand-dependent nuclear transcription factor that mediates prostate cancer cell proliferation. The triple complex of Cdk5, AR, and p35 was first identified by immunoprecipitation and immunocytochemistry. Under the treatment of R1881 (synthetic androgen), we found that the levels of phosphorylation of AR Ser81 site and AR protein were increased by overexpression of Cdk5 or p35. In addition, phosphorylation (S81), protein stability and nuclear translocation of AR were all affected by the specific Cdk5 activity inhibitor (roscovitine). Moreover, Cdk5 inhibition decreased both expression and secretion of AR downstream gene, prostate-specific antigen (PSA). The up-to-date research of prostate cancer indicated that Her2-ErbB3 provided signals to regulate AR activation except through PI3k/Akt pathway. The biochemical interactions among Her2-ErbB3 and Cdk5-p35 were first identified by immunoprecipitation. The Tyr15 phosphorylation of Cdk5 was indicated to represent its rising activity. The Tyr15 phosphorylation of Cdk5 and AR protein stability were declined by the specific Her2 activity inhibitor (AG825). In addition to AR, STAT3 was another transcription factor enthusiastically discussed in human cancer cells. Cdk5 was reported to be a kinase corresponding to Ser727 phosphorylation of STAT3. The interaction among STAT3, Cdk5 and p35 was also recognized by immunoprecipitation. The level of STAT3 Ser727 phosphorylation was paralleled to Cdk5 protein expression. Besides, the Her2 activity-dependent interaction between STAT3 and Cdk5 was determined by immunoprecipitation. Furthermore, the HRG-induced LNCaP cell growth was significantly blocked by roscovitine, which indicating that HRG modulated cell growth through Cdk5 activity. Taken together with these results, Her2-ErbB3 might play important roles in regulating AR/STAT3 functions and prostate cancer cell proliferation through Cdk5 activity, and Her2-Cdk5-AR/STAT3 axis might be potential therapeutic targets to prostate cancer.