The Effects of Dosage and Exposure Time on the Genomic Incorporation of 3'- Azido-2', 3'-Dideoxythymidine (AZT) in TK6 Cells, and the Role of AZT in DNA Methylation
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In 1987 the first anti-AIDs drug, 3'-azido-2', 3'-dideoxythymidine (AZT), was approved. Today AZT treatment includes persons with human immunodeficiency virus type 1 (HIV -1), of all ages and at all stages of the disease. One AZT treatment group is pregnant women, as AZT has been shown to significantly reduce the chance of vertical HIV -1 transmission. However AZT has recently been shown to produce tumors in the offspring of mice who are treated with it during the last third of pregnancy. In these studies, we assessed the incorporation of AZT into the genome of human lymphoblastoid (TK6) cells exposed to the drug for increasing amounts of time, and also in dose increments. Furthermore, we examined the role of AZT in DNA methylation. DNA was extracted with a non-organic extraction kit or phenol-chloroform technique. Genomic incorporation was determined via anti-AZT radioimmunoassay. Methylation was examined using restriction enzymes. F or cells exposed to AZT for increasing times, we found increasing genomic incorporation, but inconclusive methylation results. For the cells that were treated with increasing concentrations of AZT, we found more incorporation at the highest concentration. The methylation study of these cells showed a positive correlation between methylation and AZT incorporation. More AZT is thus incorporated into DNA with increased dosage and longer exposure. With increasing incorporation, AZT also induces increasing methylation. Careful examination of these effects in consideration of human treatments would seem appropriate.