Expression of delta-like ligand 4 (Dll4) and markers of hypoxia in colon cancer.
BACKGROUND
Delta-like ligand 4 (Dll4) is a Notch ligand that is upregulated by hypoxia and vascular endothelial growth factor-A (VEGF-A) and is reported to have a role in tumor angiogenesis. Evidence from xenograft studies suggests that inhibiting Dll4-Notch signalling may overcome resistance to anti-VEGF therapy. The aim of this study was to characterise the expression of Dll4 in colon cancer and to assess whether it is associated with markers of hypoxia and prognosis.


METHODS
In all, 177 colon cancers were represented in tissue microarrays. Immunohistochemistry was performed using validated antibodies against Dll4, VEGF, hypoxia-inducible factor (HIF)-1alpha, HIF-2alpha, prolyl hydroxylase (PHD)1, PHD2, PHD3 and carbonic anhydrase 9 (CA9).


RESULTS
The expression of Dll4 was observed preferentially in the endothelium of 71% (125 out of 175) of colon cancers, but not in the endothelium adjacent to normal mucosa (none out of 107, P<0.0001). The expression of VEGF was significantly associated with HIF-2alpha (P<0.0001) and Dll4 (P=0.010). Only HIF-2alpha had a significant multivariate prognostic effect (hazard ratio 1.61, 95% confidence interval 1.01-2.57). Delta-like ligand 4 was also expressed by neoplastic cells, particularly neoplastic goblet cells.


CONCLUSIONS
Endothelial expression of Dll4 is not a prognostic factor, but is significantly associated with VEGF. Assessing endothelial Dll4 expression may be critical in predicting response to anti-VEGF therapies.
Nuffield Department of Clinical Laboratory Sciences, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK.
A M
AM
Jubb
H
H
Turley
H C
HC
Moeller
G
G
Steers
C
C
Han
J-L
JL
Li
R
R
Leek
E Y
EY
Tan
B
B
Singh
N J
NJ
Mortensen
I
I
Noguera-Troise
F
F
Pezzella
K C
KC
Gatter
G
G
Thurston
S B
SB
Fox
A L
AL
Harris
D048868:Adaptor Proteins, Signal Transducing; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis; D014408:Biomarkers, Tumor / Q000096:biosynthesis*; D002135:Calcium-Binding Proteins; D015687:Cell Hypoxia / Q000502:physiology; D003110:Colonic Neoplasms / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D005260:Female; D020397:Goblet Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis*; D008297:Male; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000473:pathology; D011379:Prognosis; D015996:Survival Rate; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis; D055815:Young Adult; D000099162:Endothelial PAS Domain-Containing Protein 1
D048868:Adaptor Proteins, Signal Transducing; D051792:Basic Helix-Loop-Helix Proteins; D014408:Biomarkers, Tumor; D002135:Calcium-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1; C424126:DLL4 protein, human