Ligand-dependent Notch signaling is involved in tumor initiation and tumor maintenance in pancreatic cancer.
OBJECTIVE
Aberrant activation of the Notch signaling pathway is commonly observed in human pancreatic cancer, although the mechanism(s) for this activation has not been elucidated.


METHODS
A panel of 20 human pancreatic cancer cell lines was profiled for the expression of Notch pathway-related ligands, receptors, and target genes. Disruption of intracellular Notch signaling, either genetically by RNA interference targeting NOTCH1 or pharmacologically by means of the gamma-secretase inhibitor GSI-18, was used for assessing requirement of Notch signaling in pancreatic cancer initiation and maintenance.


RESULTS
Striking overexpression of Notch ligand transcripts was detectable in the vast majority of pancreatic cancer cell lines, most prominently JAGGED2 (18 of 20 cases, 90%) and DLL4 (10 of 20 cases, 50%). In two cell lines, genomic amplification of the DLL3 locus was observed, mirrored by overexpression of DLL3 transcripts. In contrast, coding region mutations of NOTCH1 or NOTCH2 were not observed. Genetic and pharmacologic inhibition of Notch signaling mitigated anchorage-independent growth in pancreatic cancer cells, confirming that sustained Notch activation is a requirement for pancreatic cancer maintenance. Further, transient pretreatment of pancreatic cancer cells with GSI-18 resulted in depletion in the proportion of tumor-initiating aldehyde dehydrogenase-expressing subpopulation and was associated with inhibition of colony formation in vitro and xenograft engraftment in vivo, underscoring a requirement for the Notch-dependent aldehyde dehydrogenase-expressing cells in pancreatic cancer initiation.


CONCLUSIONS
Our studies confirm that Notch activation is almost always ligand dependent in pancreatic cancer, and inhibition of Notch signaling is a promising therapeutic strategy in this malignancy.
Mullendore
Michael E
ME
Department of Pathology, The Sol Goldman Pancreatic Cancer Research Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Koorstra
Jan-Bart
JB
Li
Yue-Ming
YM
Offerhaus
G Johan
GJ
Fan
Xing
X
Henderson
Clark M
CM
Matsui
William
W
Eberhart
Charles G
CG
Maitra
Anirban
A
Feldmann
Georg
G
D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005784:Gene Amplification; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D000072101:Jagged-2 Protein; D008024:Ligands; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010190:Pancreatic Neoplasms / Q000209:etiology / Q000235:genetics / Q000378:metabolism*; D051881:Receptor, Notch1 / Q000235:genetics; D051883:Receptor, Notch2 / Q000235:genetics; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction
C496666:DLL3 protein, human; D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; C490504:JAG2 protein, human; D000072101:Jagged-2 Protein; D008024:Ligands; D008565:Membrane Proteins; C497761:NOTCH1 protein, human; C497764:NOTCH2 protein, human; D051881:Receptor, Notch1; D051883:Receptor, Notch2; D051880:Receptors, Notch; D000444:Aldehyde Dehydrogenase; D053829:Amyloid Precursor Protein Secretases