Abstract
Proline-directed protein kinase FA (PDPK FA) was originally identified as the activating factor of type-1 protein phosphatase/glycogen synthase kinase-3a but has subsequently been demonstrated as a multisubstrate PDPK involved in the regulation of diverse cell functions. However, the systemic functional role of PDPK FA in human cancers remains largely unknown and is going to be the central theme of this thesis. The PDPK FA-specific antibody was firstly produced and characterized, which could efficiently and specifically immunoblot and immunoprecipitate PDPK FA from various human tissues and cells. By using this specific antibody, the expression of PDPK FA was found to be overexpressed many-fold in human cervical carcinoma tissues relative to normal control, suggesting an association of PDPK FA with human neoplastic disease. In human cervical carcinoma HeLa cells, it was further demonstrated that the activity of PDPK FA was duly controlled by protein overexpression and enhanced tyrosine phosphorylation, which is involved in the regulation of late mitosis. The observation was next extended to human prostate carcinoma cells. In order to further identify the functional role of PDPK FA in carcinoma cells, a specific PDPK FA antisense expression vector was constructed and transfected into human prostate carcinoma PC-3 cells. The stable antisense clones were selected and characterized, which exhibited cell growth retardation, impaired colony formation and loss of serum and anchorage-independent growth, demonstrating that specific antisense suppression of PDPK FA is sufficient to block proliferation and transformation of human prostate carcinoma cells. Moreover, specific antisense suppression of PDPK FA was also demonstrated to be sufficient to enhance chemosensitivity of various anticancer drugs and to potentiate apoptotic induction, demonstrating a primary essential role of PDPK FA in the regulation of proliferation, transformation, drug resistance and apoptosis of human cancer cells. In the final part of this thesis, the overexpression of PDPK FA was found to be systemically overexpressed in both tumors and lymphocytes of human cervical, prostate and breast cancer patients, suggesting a systemic role of PDPK FA in various human cancers. The results presented in this thesis may provide a hopeful clinic target for early cancer detection, prevention and treatment of various human cancers.