Role of protein kinase C-iota in transformed non-malignant RWPE-1 cells and androgen-independent prostate carcinoma DU-145 cells.
Prostate cancer is one of the leading causes of death among men in the USA.


OBJECTIVE
In this study, we investigated the role of atypical protein kinase C-iota (PKC-iota) in androgen independent prostate DU-145 carcinoma cellscompared to transformed non-malignant prostate RWPE-1 cells.


METHODS
Western blotting and immunoprecipitations demonstrated that PKC-iotaisassociated with cyclin-dependent kinase activating kinase (CAK/Cdk7) in RWPE-1 cells, but not in DU-145 cells.


RESULTS
Treatment of prostate RWPE-1 cells with PKC-iota silencing RNA (siRNA) decreased cell viability,cell-cycle accumulation at G2/M phase, and phosphorylation of Cdk7 and Cdk2. In addition, PKC-iota siRNA treatment caused less phosphorylation ofBad at ser-155, ser-136, and greater Bad/Bcl-xL heterodimerization, leading to apoptosis. In DU-145 cells, PKC-iota was anti-apoptotic and was required for cell survival. Treatment with PKC-iota siRNA blocked increase in cell number, and inhibited G1/S transition by accumulation of cells in G0/G1phase. In addition to cell-cycle arrest, both RWPE-1 and DU-145 cells underwent apoptosis due to mitochondrial dysfunction and apoptosis cascades, such as release of cytochrome c,activation of caspase-7, and poly (ADP-ribose)polymerase (PARP) cleavage.


CONCLUSIONS
Our results suggest that PKC-iota is required for cell survival in both transformed non-malignant prostate RWPE-1 cells and androgen-independent malignant prostate DU-145 cells, whereas suppressing PKC-iota lead to apoptosis in DU-145 prostate cells.
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Department of Chemistry, University of South Florida, Tampa, Florida, USA.
Acevedo-Duncan
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D017209:Apoptosis / Q000502:physiology; D002452:Cell Count; D002453:Cell Cycle / Q000502:physiology; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism / Q000502:physiology*; D008297:Male; D010766:Phosphorylation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011467:Prostate / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D051025:bcl-Associated Death Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism; D000095043:Cyclin-Dependent Kinase-Activating Kinase; D000099293:Protein Kinase C-lambda
D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D007527:Isoenzymes; D011065:Poly(ADP-ribose) Polymerases; D011493:Protein Kinase C; D034741:RNA, Small Interfering; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D000095043:Cyclin-Dependent Kinase-Activating Kinase; D000099293:Protein Kinase C-lambda; C494819:BAD protein, human; C494811:BCL2L1 protein, human; C000722416:CDK7 protein, human