RESUMEN
BACKGROUND: Testing for mutant K-ras in stool has been proposed for the detection of pancreatic and colorectal cancer (CRC). Different analytical techniques have been developed, but studies of this biomarker in the general population are lacking. We investigated the prevalence and potential determinants of mutant K-ras in stool in a large sample of unselected older adults and assessed the association with colonoscopic findings. METHODS: In stool samples from 875 older adults (age range 50-75 years) participating in a large-scale population-based cohort study, we used mutant-enriched PCR and allele-specific hybridization reaction to analyze mutations in codons 12 and 13 of the K-ras gene. We assessed the association between mutant K-ras in stool and risk factors for gastrointestinal cancer sites, exocrine pancreatic insufficiency determined by fecal pancreas elastase 1, and colonoscopic findings. RESULTS: The overall prevalence of mutant K-ras in stool was 8% (95% confidence interval 6%-10%). There was a tentative association between increased fecal pancreas elastase 1 and mutant K-ras in stool (P = 0.09). Patients with advanced colorectal neoplasia diagnosed within 2 years after stool collection (24 with advanced adenomas, 7 with CRC) all tested negative. CONCLUSION: The proposed assay identifies mutant K-ras in stool at a higher prevalence than has been reported for other analytical techniques. Our findings do not support the use of this assay for CRC screening, but its potential use for early detection of pancreatic cancer (in combination with other markers) requires further investigation.
Asunto(s)
ADN/análisis , Heces/química , Genes ras , Adenoma/diagnóstico , Adenoma/genética , Anciano , Alelos , Estudios de Cohortes , Colonoscopía , Neoplasias Colorrectales/diagnóstico , Neoplasias Colorrectales/genética , Femenino , Predisposición Genética a la Enfermedad , Humanos , Masculino , Persona de Mediana Edad , Mutación , Hibridación de Ácido Nucleico , Elastasa Pancreática/análisis , Reacción en Cadena de la Polimerasa , RiesgoRESUMEN
Aggrecanase activities of ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) proteinases were measured with a recombinant aggrecan fragment and two monoclonal antibodies. Recombinant human aggrecan interglobular domain was first incubated in the presence of ADAMTS enzymes. The aggrecan peptide with the N-terminal sequence ARGSVIL released upon hydrolysis was then quantified in an enzyme-linked immunosorbent assay (ELISA) with an anti-neoepitope antibody specific for the N-terminal ARGSVIL sequence and a second anti-aggrecan peptide antibody. For higher sensitivity of the assay, P1-P5 residues of the aggrecanase site within the aggrecan substrate were changed by in vitro mutagenesis. Specific activities of recombinant truncated ADAMTS1 and ADAMTS4 estimated with authentic aggrecan interglobular domain amounted to 2.4 +/- 0.4 and 21.7 +/- 9.5 nmoles hydrolyzed substrate/min.mg, respectively. The values were 10.3 +/- 5.1 and 151.5 +/- 93.5 nmoles/min.mg for hydrolysis of the modified substrate. The aggrecanase activity assay can be used for (1) kinetic characterization of aggrecanase activities of human and animal ADAMTS, (2) screening of inhibitors for aggrecan hydrolyzing ADAMTS, and (3) estimation of aggrecanase activities in biological samples.