BACKGROUND: Tumor cells that shed into stool are attractive targets for molecular screening and early detection of colon or pancreatic malignancies. We developed a diagnostic test to screen for 10 of the most common mutations of codons 12 and 13 of the K-ras gene by hybridization to a new biochip array. METHODS: DNA was isolated from 26 stool samples by column-based extraction from 9 cell lines. Peptide nucleic acid (PNA)-mediated PCR clamping was used for mutant-specific amplification. We used a biochip, consisting of a small plastic support with covalently immobilized 13mer oligonucleotides. The read out of the biochip was done by confocal time-resolved laser scanning. Hybridization, scanning, and data evaluation could be performed in <2 h. RESULTS: Approximately 80 ng of DNA was obtained from 200-mg stool samples. No inhibition of the PCR by remaining impurities from stool was observed. Mutation detection was possible in 1000-fold excess of wild-type sequence. Discrimination ratios between the mutations were >19 as demonstrated by hybridization with tumor cell line DNA. Stool samples (n = 26) were analyzed in parallel with PNA-PCR, restriction assay for K-ras codon 12 mutations, sequencing, and hybridization to the biochip. Nine mutations were found by hybridization, all confirmed by sequencing. PNA-PCR alone leads to an overestimation of mutations because suppression of the wild type is not effective enough with high concentrations of wild-type DNA. The restriction assay found only four mutations. CONCLUSIONS: The K-ras biochip is well suited for fast mutation detection from stool in colorectal cancer screening.
BACKGROUND:Tumor cells that shed into stool are attractive targets for molecular screening and early detection of colon or pancreatic malignancies. We developed a diagnostic test to screen for 10 of the most common mutations of codons 12 and 13 of the K-ras gene by hybridization to a new biochip array. METHODS: DNA was isolated from 26 stool samples by column-based extraction from 9 cell lines. Peptide nucleic acid (PNA)-mediated PCR clamping was used for mutant-specific amplification. We used a biochip, consisting of a small plastic support with covalently immobilized 13mer oligonucleotides. The read out of the biochip was done by confocal time-resolved laser scanning. Hybridization, scanning, and data evaluation could be performed in <2 h. RESULTS: Approximately 80 ng of DNA was obtained from 200-mg stool samples. No inhibition of the PCR by remaining impurities from stool was observed. Mutation detection was possible in 1000-fold excess of wild-type sequence. Discrimination ratios between the mutations were >19 as demonstrated by hybridization with tumor cell line DNA. Stool samples (n = 26) were analyzed in parallel with PNA-PCR, restriction assay for K-ras codon 12 mutations, sequencing, and hybridization to the biochip. Nine mutations were found by hybridization, all confirmed by sequencing. PNA-PCR alone leads to an overestimation of mutations because suppression of the wild type is not effective enough with high concentrations of wild-type DNA. The restriction assay found only four mutations. CONCLUSIONS: The K-ras biochip is well suited for fast mutation detection from stool in colorectal cancer screening.
Authors: Susan E Cottrell; Jürgen Distler; Nancy S Goodman; Suzanne H Mooney; Antje Kluth; Alexander Olek; Ina Schwope; Reimo Tetzner; Heike Ziebarth; Kurt Berlin Journal: Nucleic Acids Res Date: 2004-01-13 Impact factor: 16.971
Authors: Christoph Ausch; Veronika Buxhofer-Ausch; Christian Oberkanins; Barbara Holzer; Michael Minai-Pour; Stephan Jahn; Nadia Dandachi; Robert Zeillinger; Gernot Kriegshäuser Journal: J Mol Diagn Date: 2009-10-01 Impact factor: 5.568