Quantitation of aberrant interlocus T-cell receptor rearrangements in mouse thymocytes and the effect of the herbicide 2,4-dichlorophenoxyacetic acid.
Small studies in human populations have suggested a correlation between the frequency of errors in antigen receptor gene assembly and lymphoid malignancy risk. In particular, agricultural workers exposed to pesticides have both an increased risk for lymphoma and an increased frequency of errors in antigen receptor gene assembly. In order to further investigate the potential of such errors to serve as a mechanistically based biomarker of lymphoid cancer risk, we have developed a sensitive PCR assay for quantifying errors of V(D)J recombination in the thymocytes of mice. This assay measures interlocus rearrangements between two T-cell receptor loci, V-gamma and J-beta, located on chromosomes 13 and 6, respectively. The baseline frequency in four strains of mice was determined at several ages (2-8 weeks of age) and was found to be stable at approximately 1.5 x 10(-5) per thymocyte. Strain AKR, which has a high susceptibility to T-cell lymphomas, did not show an elevated frequency of aberrant V(D)J events. We used this assay to examine the effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on the frequency of these events. Female B6C3F1 mice, 27 days of age, were exposed to 2,4-D by gavage at doses of 0, 3, 10, 30, and 100 mg/kg/day for 4 successive days and sacrificed on day 5. Thymus DNA was isolated and examined for illegitimate V(D)J recombination-mediated gene rearrangements. In addition, pregnant mice were exposed to 2,4-D and thymocytes from the offspring examined at 2 weeks of age. No significant increase in aberrant V(D)J rearrangements was found, indicating that under these conditions 2,4-D does not appear to effect this important mechanism of carcinogenesis.
Knapp
Geremy W
GW
Environmental Carcinogenesis Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
Setzer
R Woodrow
RW
Fuscoe
James C
JC
D015084:2,4-Dichlorophenoxyacetic Acid / Q000633:toxicity*; D000818:Animals; D001483:Base Sequence; D005260:Female; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor / Q000187:drug effects* / Q000235:genetics; D015334:Gene Rearrangement, gamma-Chain T-Cell Antigen Receptor / Q000187:drug effects* / Q000235:genetics; D005819:Genetic Markers; D006540:Herbicides / Q000633:toxicity*; D007133:Immunoglobulin Joining Region / Q000187:drug effects / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000187:drug effects / Q000235:genetics; D008297:Male; D018811:Maternal Exposure; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D011247:Pregnancy; D011948:Receptors, Antigen, T-Cell / Q000235:genetics; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000187:drug effects* / Q000235:genetics*; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects*
D005819:Genetic Markers; D006540:Herbicides; D007133:Immunoglobulin Joining Region; D007135:Immunoglobulin Variable Region; D011948:Receptors, Antigen, T-Cell; D015084:2,4-Dichlorophenoxyacetic Acid