DPC-4 (Smad-4) and K-ras gene mutations in biliary tract epithelium in children with anomalous pancreaticobiliary ductal union.
OBJECTIVE
Recent studies have found that anomalous pancreaticobiliary ductal union (APBDU) is a substantial risk factor for biliary tract cancer at a younger age. DPC-4 (Smad-4) is a new tumor suppressor gene frequently inactivated in pancreatic and bile duct adenocarcinoma. To clarify carcinogenesis in APBDU, the authors investigated possible DPC-4 and K-ras mutations in 35 pediatric patients.


METHODS
DNA was extracted from biliary tract epithelial cells, which were resected surgically and histologically purified using microdissection. Polymerase chain reaction (PCR) primers were designed specifically for exons 8-11 of DPC-4 (18q21.1) and exons 1-2 of the K-ras oncogene (12p12.1). DNA sequences were determined using the direct DyeDeoxy Terminator Cycle method.


RESULTS
Of 35 children, 30 had wild-type DPC-4 and K-ras genes. K-ras mutations were detected in 5 patients, 4 of whom showed epithelial hyperplasia or metaplasia. In a 12-year-old girl with adenocarcinoma arising from a choledochal cyst, K-ras and DPC-4 (homozygous deletion) mutations were identified simultaneously.


CONCLUSIONS
These results suggest that carcinogenesis in the biliary tract epithelium in APBDU is accompanied by multistep genetic mutational events; K-ras gene mutation occurs early in epithelial hyperplasia or metaplasia, whereas inactivation of the DPC-4 gene accumulates late in the progression of biliary tract adenocarcinoma.
Shimotake
Takashi
T
Division of Surgery, Children's Research Hospital, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Aoi
Shigeyoshi
S
Tomiyama
Hideki
H
Iwai
Naomi
N
D000230:Adenocarcinoma / Q000235:genetics; D001659:Biliary Tract / Q000002:abnormalities*; D001661:Biliary Tract Neoplasms / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D002648:Child; D000013:Congenital Abnormalities / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004848:Epithelium; D005260:Female; D017353:Gene Deletion; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D010183:Pancreatic Ducts / Q000002:abnormalities*; D017354:Point Mutation; D017422:Sequence Analysis, DNA; D051901:Smad4 Protein; D015534:Trans-Activators / Q000235:genetics*
D004268:DNA-Binding Proteins; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D015534:Trans-Activators