Prospective detection of codon 249 mutations in plasma of hepatocellular carcinoma patients

Abstract

A specific missense mutation in the p53 tumor gene at codon 249 has been reported in over 50% of hepatocellular carcinoma (HCC) tumors and in paired blood samples from areas of high dietary exposure to aflatoxin B₁, including Qidong, People's Republic of China. Using a combination of pre-digestion with HaeIII, PCR and mass spectrometry, the temporality of this mutation in plasma before and after the clinical diagnosis of HCC was examined. Sixteen liver cancer cases, diagnosed between 1997 and 2001, were selected from a prospective cohort of 1638 high-risk individuals in Qidong on the basis of available annual plasma samples spanning the years before and after diagnosis. The codon 249 mutation was detected in plasma samples obtained after diagnosis in seven of the 15 cases (46.7%) with PCR amplifiable DNA, which is in accord with the reported prevalence of this mutation in HCC. The persistent detection of this mutation in plasma collected annually following diagnosis was statistically significant (P = 0.024, two-tailed) in repetitive samples following diagnosis. Moreover, the mutation was detected in the plasma of four of eight cases positive at the time of diagnosis at least 1 year and in one case 5 years prior to diagnosis. Tracking of the marker in pre-diagnostic samples was borderline statistically significant (P = 0.066). None of the 18 healthy US control plasma samples had any detectable mutations. We have therefore found that pre-diagnosis biomarkers of specific p53 mutations can be measured in plasma and this suggests a paradigm for developing these markers for use in prevention and intervention trials.