In situ validation of an intestinal stem cell signature in colorectal cancer.
OBJECTIVE
Wnt/Tcf, Lgr5, Ascl2 and/or Bmi1 signalling is believed to define the mouse intestinal stem cell niche(s) from which adenomas arise. The aim of this study was to determine the relevance of these putative intestinal stem cell markers to human colorectal cancer.


METHODS
19 putative intestinal stem cell markers, including Ascl2 and Lgr5, were identified from published data and an evaluation of a human colorectal gene expression database. Associations between these genes were assessed by isotopic in situ hybridisation (ISH) in 57 colorectal adenocarcinomas. Multiplex fluorescent ISH and chromogenic non-isotopic ISH were performed to confirm expression patterns. The prognostic significance of Lgr5 was assessed in 891 colorectal adenocarcinomas.


RESULTS
Ascl2 and Lgr5 were expressed in 85% and 74% of cancers respectively, and expression was positively correlated (p=0.003). Expression of Bmi1 was observed in 47% of cancers but was very weak in 98% of cases with expression. Both Ascl2 and/or Lgr5 were positively correlated with the majority of genes in the signature but neither was correlated with Cdk6, Gpx2, Olfm4 or Tnfrsf19. Lgr5 did not have prognostic significance.


CONCLUSIONS
These data suggest that 74-85% of colorectal cancers express a Lgr5/Ascl2 associated signature and support the hypothesis that they derive from Lgr5(+)/Ascl2(+) crypt stem cells, not Bmi1(+) stem cells. However, Olfm4 was not found to be a useful marker of Lgr5(+) cells in normal colon or tumours. In this large series, Lgr5 expression is not associated with increased tumour aggressiveness, as might be expected from a cancer stem cell marker.
Department of Pathology, Stanford University Medical Center, Stanford, California, USA.
Jennifer L
JL
Ziskin
Debra
D
Dunlap
Murat
M
Yaylaoglu
Imola K
IK
Fodor
William F
WF
Forrest
Rajesh
R
Patel
Nianfeng
N
Ge
Gordon G
GG
Hutchins
James K
JK
Pine
Philip
P
Quirke
Hartmut
H
Koeppen
Adrian M
AM
Jubb
D000230:Adenocarcinoma / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D030541:Databases, Genetic; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D052138:Genes, Neoplasm; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D011379:Prognosis; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism*
D051792:Basic Helix-Loop-Helix Proteins; D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D043562:Receptors, G-Protein-Coupled; C065501:ASCL2 protein, human; C116884:LGR5 protein, human