Detection of K-ras point mutations in sputum from patients with adenocarcinoma of the lung by point-EXACCT.
OBJECTIVE
Kirsten ras (K-ras) point mutations are found in 30% to 56% of pulmonary adenocarcinomas by means of highly sensitive techniques. Recently, the Point-EXACCT (point mutation detection using exonuclease amplification coupled capture technique) method was described, which detected one cell with a mutation in 15,000 normal cells. The aim of this study was to examine whether K-ras point mutations could be found with this rapid method in the sputum of patients with adenocarcinoma of the lung.


METHODS
DNA from paraffin-embedded adenocarcinoma and corresponding sputum samples were analyzed for mutations of the K-ras gene. Twenty-eight biopsy specimens and 54 sputum samples of 22 patients were used for amplification and K-ras codon 12 point mutation detection.


RESULTS
In 11 of 22 patients (50%), a mutation in K-ras codon 12 was shown in the tumor sample. In five of 11 patients (45%) with a K-ras mutation in the tumor, the same type of mutation was identified in at least one sputum sample. A mutation could not be detected in any of the sputum samples from patients with a K-ras-negative tumor. Time between K-ras point mutation detection in sputum and clinical diagnosis of lung cancer varied from 1 month to almost 4 years. In two of the five patients with K-ras-positive sputum specimens, malignant cells were found with cytologic examination.


CONCLUSIONS
Point-EXACCT is suitable for the detection of K-ras point mutations in sputum samples of patients with adenocarcinoma of the lung. This approach may be an important adjunct to cytology in the early diagnosis of lung cancer.
Somers
V A
VA
Department of Pathology, Maastricht University, The Netherlands. vso@lpat.azm.nl
Pietersen
A M
AM
Theunissen
P H
PH
Thunnissen
F B
FB
D000230:Adenocarcinoma / Q000235:genetics*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003062:Codon; D004273:DNA, Neoplasm / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification; D005260:Female; D011905:Genes, ras; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D017354:Point Mutation; D013183:Sputum / Q000737:chemistry* / Q000166:cytology
D003062:Codon; D004273:DNA, Neoplasm