title: Protein kinase C epsilon is a predictive biomarker of aggressive breast cancer and a validated target for RNA interference anticancer therapy.
abstract: Tumor metastasis is the major cause of morbidity and mortality in patients with breast cancer. It is critical to identify metastasis enabling genes and understand how they are responsible for inducing specific aspects of the metastatic phenotype to allow for improved clinical detection and management. Protein kinase C epsilon (PKC epsilon), a member of a family of serine/threonine protein kinases, is a transforming oncogene that has been reported to be involved in cell invasion and motility. In this study, we investigated the role of PKC epsilon in breast cancer development and progression. High-density tissue microarray analysis showed that PKC epsilon protein was detected in 73.6% (106 of 144) of primary tumors from invasive ductal breast cancer patients. Increasing PKC epsilon staining intensity was associated with high histologic grade (P = 0.0206), positive Her2/neu receptor status (P = 0.0419), and negative estrogen (P = 0.0026) and progesterone receptor status (P = 0.0008). Kaplan-Meier analyses showed that PKC epsilon was significantly associated with poorer disease-free and overall survival (log-rank, P = 0.0478 and P = 0.0414, respectively). RNA interference of PKC epsilon in MDA-MB231 cells, an aggressive breast cancer cell line with elevated PKC epsilon levels, resulted in a cell phenotype that was significantly less proliferative, invasive, and motile than the parental or the control RNA interference transfectants. Moreover, in vivo tumor growth of small interfering RNA-PKC epsilon MDA-MB231 clones was retarded by a striking 87% (P < 0.05) and incidence of lung metastases was inhibited by 83% (P < 0.02). PKC epsilon-deficient clones were found to have lower RhoC GTPase protein levels and activation. Taken together, these results revealed that PKC epsilon plays a critical and causative role in promoting an aggressive metastatic breast cancer phenotype and as a target for anticancer therapy.
authors.affiliation: Department of Internal Medicine, Division of Hematology and Oncology, University of Michigan Health System, Ann Arbor, Michigan 48109, USA. qpan@med.umich.edu
authors.forename: Quintin
authors.initials: Q
authors.lastname: Pan
authors.forename: Li Wei
authors.initials: LW
authors.lastname: Bao
authors.forename: Celina G
authors.initials: CG
authors.lastname: Kleer
authors.forename: Michael S
authors.initials: MS
authors.lastname: Sabel
authors.forename: Kent A
authors.initials: KA
authors.lastname: Griffith
authors.forename: Theodoros N
authors.initials: TN
authors.lastname: Teknos
authors.forename: Sofia D
authors.initials: SD
authors.lastname: Merajver
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000628:therapy; D018270:Carcinoma, Ductal, Breast / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000628:therapy; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D011237:Predictive Value of Tests; D051744:Protein Kinase C-epsilon / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D023041:Xenograft Model Antitumor Assays; D018631:ras Proteins; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D000075024:rhoC GTP-Binding Protein
chemical_list: D014408:Biomarkers, Tumor; D034741:RNA, Small Interfering; D051744:Protein Kinase C-epsilon; C066690:RHOC protein, human; C512911:Rhoc protein, mouse; D018631:ras Proteins; D020741:rho GTP-Binding Proteins; D000075024:rhoC GTP-Binding Protein