UHRF1 regulation of the Keap1-Nrf2 pathway in pancreatic cancer contributes to oncogenesis.
The cellular defence protein Nrf2 is a mediator of oncogenesis in pancreatic ductal adenocarcinoma (PDAC) and other cancers. However, the control of Nrf2 expression and activity in cancer is not fully understood. We previously reported the absence of Keap1, a pivotal regulator of Nrf2, in ∼70% of PDAC cases. Here we describe a novel mechanism whereby the epigenetic regulator UHRF1 suppresses Keap1 protein levels. UHRF1 expression was observed in 20% (5 of 25) of benign pancreatic ducts compared to 86% (114 of 132) of pancreatic tumours, and an inverse relationship between UHRF1 and Keap1 levels in PDAC tumours (n = 124) was apparent (p = 0.002). We also provide evidence that UHRF1-mediated regulation of the Nrf2 pathway contributes to the aggressive behaviour of PDAC. Depletion of UHRF1 from PDAC cells decreased growth and enhanced apoptosis and cell cycle arrest. UHRF1 depletion also led to reduced levels of Nrf2-regulated downstream proteins and was accompanied by heightened oxidative stress, in the form of lower glutathione levels and increased reactive oxygen species. Concomitant depletion of Keap1 and UHRF1 restored Nrf2 levels and reversed cell cycle arrest and the increase in reactive oxygen species. Mechanistically, depletion of UHRF1 reduced global and tumour suppressor promoter methylation in pancreatic cancer cell lines, and KEAP1 gene promoter methylation was reduced in one of three cell lines examined. Thus, methylation of the KEAP1 gene promoter may contribute to the suppression of Keap1 protein levels by UHRF1, although our data suggest that additional mechanisms need to be explored. Finally, we demonstrate that K-Ras drives UHRF1 expression, establishing a novel link between this oncogene and Nrf2-mediated cellular protection. Since UHRF1 over-expression occurs in other cancers, its ability to regulate the Keap1-Nrf2 pathway may be critically important to the malignant behaviour of these cancers.
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Wafa
W
Abu-Alainin
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Thompson
T
Gana
Roy Castle Lung Cancer Research Programme, Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Triantafillos
T
Liloglou
Department of Pharmacology and Therapeutics, University of Liverpool, UK.
Adedamola
A
Olayanju
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Lawrence N
LN
Barrera
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Robert
R
Ferguson
Department of Pathology, Royal Liverpool University Hospital, UK.
Fiona
F
Campbell
Department of Pathology, Royal Liverpool University Hospital, UK.
Timothy
T
Andrews
Department of Pharmacology and Therapeutics, University of Liverpool, UK.
Christopher
C
Goldring
Department of Pharmacology and Therapeutics, University of Liverpool, UK.
Neil
N
Kitteringham
Department of Pharmacology and Therapeutics, University of Liverpool, UK.
Brian K
BK
Park
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Taoufik
T
Nedjadi
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Michael C
MC
Schmid
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Joseph R
http://orcid.org/0000-0002-7410-9004
JR
Slupsky
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
William
W
Greenhalf
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
John P
JP
Neoptolemos
Department of Molecular and Clinical Cancer Medicine, University of Liverpool, UK.
Eithne
E
Costello
D022762:CCAAT-Enhancer-Binding Proteins / Q000172:deficiency / Q000502:physiology*; D063646:Carcinogenesis; D059447:Cell Cycle Checkpoints / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D019175:DNA Methylation / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D010190:Pancreatic Neoplasms / Q000209:etiology* / Q000473:pathology; D015398:Signal Transduction / Q000502:physiology; D047368:Tumor Burden; D014407:Tumor Cells, Cultured; D044767:Ubiquitin-Protein Ligases
D022762:CCAAT-Enhancer-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C406364:UHRF1 protein, human; D044767:Ubiquitin-Protein Ligases
DNA methylation; Keap1; Nrf2; UHRF1; pancreatic cancer