QUANTIFICATION OF T(14-18) IN THE LYMPHOCYTES OF HEALTHY ADULT HUMANSAS A POSSIBLE BIOMARKER FOR ENVIRONMENTAL EXPOSURES TO CARCINOGENS

A t(14;18) chromosomal translocation is found in similar to 85% of fol licular lymphomas by both cytogenetic and molecular analyses, This rea rrangement deregulates expression of the bcl-2 proto-oncogene by trans location into the immunoglobulin heavy chain locus and is probably med iated by illegitimate V(D)J recombination, We have developed a quantit ative nested PCR method for detecting this event in lymphocytes of hea lthy individuals, Genomic DNA is purified from peripheral blood lympho cytes, and 2.5 mu g (representing 4x10(5) cells) are amplified with tr anslocation-specific primers under conditions in which a single copy, if present, will give a detectable PCR product, Multiple replicates ar e analyzed for each individual, and Poisson statistics are then used t o estimate the translocation mutant frequency, We have examined lympho cyte DNA from 34 healthy individuals by this assay and found the frequ ency of cells with t(14;18) to range from < 0.8-96 x 10(-7), The molec ular nature of the translocations has been investigated by determining the DNA sequence at the translocation junctions, In several individua ls, multiple isolates of the same translocation event mere recovered, indicating that the cell with the original translocation had undergone clonal expansion, In addition, multiple independent translocations we re shown to occur within an individual. Since this translocation appea rs to be one step in the progression of a normal cell to a cancer cell , this assay may have utility as an effects biomarker for environmenta l carcinogen exposure.