Clonality, founder mutations, and field cancerization in human ulcerative colitis-associated neoplasia.
OBJECTIVE
The clonality of colitis-associated neoplasia has not been fully determined. One previous report showed polyclonal origins with subsequent monoclonal outgrowth. We aimed to assess the clonality and mutation burden of individual crypts in colitis-associated neoplasias to try to identify gatekeeping founder mutations, and explore the clonality of synchronous lesions to look for field effects.


METHODS
Individual crypts (range, 8-21 crypts) were microdissected from across 17 lesions from 10 patients. Individual crypt adenomatous polyposis coli (APC), p53, K-RAS, and 17p loss of heterozygosity mutation burden was established using polymerase chain reaction and sequencing analysis. Serial sections underwent immunostaining for p53, beta-catenin, and image cytometry to detect aneuploidy.


RESULTS
In most lesions an oncogenic mutation could be identified in all crypts across the lesion showing monoclonality. This founder mutation was a p53 lesion in the majority of neoplasms but 4 tumors had an initiating K-RAS mutation. Some nondysplastic crypts surrounding areas of dysplasia were found to contain clonal p53 mutations and in one case 3 clonal tumors arose from a patch of nondysplastic crypts containing a K-RAS mutation.


CONCLUSIONS
This study used mutation burden analysis of individual crypts across colitis-associated neoplasms to show lesion monoclonality. This study confirmed p53 mutation as initiating mutation in the majority of lesions, but also identified K-RAS activation as an alternative gatekeeping mutation. Local and segmental field cancerization was found by showing pro-oncogenic mutations in nondysplastic crypts surrounding neoplasms, although field changes are unlikely to involve the entire colon because widely separated tumors were genetically distinct.
Leedham
Simon J
SJ
Histopathology Unit, Cancer Research UK, London, United Kingdom. simon.leedham@cancer.org.uk
Graham
Trevor A
TA
Oukrif
Dahmane
D
McDonald
Stuart A C
SA
Rodriguez-Justo
Manuel
M
Harrison
Rebecca F
RF
Shepherd
Neil A
NA
Novelli
Marco R
MR
Jankowski
Janusz A Z
JA
Wright
Nicholas A
NA
D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics / Q000378:metabolism; D003093:Colitis, Ulcerative / Q000150:complications / Q000235:genetics* / Q000378:metabolism; D003106:Colon / Q000378:metabolism / Q000473:pathology; D003110:Colonic Neoplasms / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D018895:Microsatellite Repeats / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras); D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
D025601:Adenomatous Polyposis Coli Protein; C495270:CTNNB1 protein, human; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D051176:beta Catenin; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins