CUX1: target of Akt signalling and mediator of resistance to apoptosis in pancreatic cancer.
OBJECTIVE
The transcription factor CUX1 is known as a regulator of cell differentiation and cell cycle progression. Previously, CUX1 was identified as a modulator of invasiveness in various cancers. Based on expression profiles suggesting a role for CUX1 in mediating chemoresistance, the aim of this study was to characterise the effect of CUX1 on apoptosis as well as its regulation by signalling pathways modulating drug resistance in pancreatic cancer.


METHODS
The effect of CUX1 on TRAIL- (tumour necrosis factor-related apoptosis-inducing ligand) and drug-induced apoptosis was analysed using overexpression and knock-down strategies. Regulation of CUX1 by phosphatidylinositol-3-kinase (PI3K)/Akt signalling was examined at the mRNA and protein level. The effect of CUX1 knock-down by nanoparticle-complexed small interfering RNA (siRNA) in vivo was analysed in a murine xenograft model. Furthermore, CUX1 RNA and protein expression was evaluated in human pancreatic cancer and adjacent normal tissues.


RESULTS
Knock-down of CUX1 resulted in significantly enhanced TRAIL- and drug-induced apoptosis, associated with increased PARP (poly ADP-ribose polymerase) cleavage and caspase activity. Vice versa, overexpression of CUX1 inhibited apoptosis. CUX1 expression was induced by activation of Akt/protein kinase B signalling, and decreased by PI3K inhibitors. The antiapoptotic effect of CUX1 was associated with upregulation of BCL2 and downregulation of tumour necrosis factor alpha. CUX1 was significantly overexpressed in pancreatic cancers, as analysed by in situ hybridisation and immunohistochemistry. In vivo, silencing of CUX1 by intratumourally administered polyethylenimine-complexed siRNA led to reduced tumour growth and increased apoptosis in pancreatic cancer xenografts.


CONCLUSIONS
CUX1 was identified as an important mediator of tumour cell survival in pancreatic cancer in vitro and in vivo.
Ripka
S
S
Department of Gastroenterology and Endocrinology, University Hospital, Philipps-University, Marburg, Germany.
Neesse
A
A
Riedel
J
J
Bug
E
E
Aigner
A
A
Poulsom
R
R
Fulda
S
S
Neoptolemos
J
J
Greenhalf
W
W
Barth
P
P
Gress
T M
TM
Michl
P
P
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053470:Caspases, Effector / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D015316:Genetic Therapy / Q000379:methods; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D009363:Neoplasm Proteins / Q000502:physiology; D009368:Neoplasm Transplantation; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology; D014157:Transcription Factors; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
C080632:CUX1 protein, human; D018398:Homeodomain Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014157:Transcription Factors; D011065:Poly(ADP-ribose) Polymerases; D051057:Proto-Oncogene Proteins c-akt; D053470:Caspases, Effector