ABSTRACT
The in vivo frequency of mutants resulting from mutation at the hprt locus in human T-lymphocytes can be determined by a cloning assay. This assay quantifies the frequency of 6-thioguanine-resistant (TGr) T-cells through growth of colonies in 96-well microtiter dishes. The reproducibility of the TGr mutant frequency values has now been assessed in a longitudinal study of six individuals (three male, three female, aged 22-33 years) employing 4-5 blood samples over a 26-37 week time period. Cloning assays were performed with both fresh and cryopreserved cell samples. No significant differences were found among the mutant frequency values for multiple samples from each individual with both fresh and cryopreserved cell samples. These results demonstrate the reproducibility of this cloning assay for in vivo mutant frequency determinations in human T-lymphocytes.
Subject(s)
Hypoxanthine Phosphoribosyltransferase/genetics , Mutation , T-Lymphocytes/enzymology , Adult , Clone Cells , Female , Humans , Male , Mutagenicity TestsABSTRACT
Somatic cell mutation which occurs in vivo in humans can be determined by measurement of the frequency of the 6-thioguanine-resistant (TGr) T lymphocytes in samples of peripheral blood. This frequency can be determined by either a short-term autoradiographic methodology or a longer cell-cloning methodology. The advantage of the former is the relative simplicity of the assay, while the latter allows recovery of mutant clones for further characterization. This report presents results of a longitudinal study of cancer chemotherapy nurses and other health care personnel by use of the autoradiography assay. The use of this assay in human mutagenicity monitoring and the analysis of the TGr cell frequencies are discussed in terms of age effects and validation of 'elevated' frequencies by use of the clonal assay. This report then presents evidence that both assays yield similar TGr cell frequencies in two groups of 'normal adults'. The mean variant frequency (+/- S.D.) for 82 autoradiographic assays was 8.7 (+/- 6.1) X 10(-6), while the mean mutant frequency (+/- S.D.) for 115 clonal assays was 6.5 (+/- 4.8) X 10(-6). In addition, concurrent autoradiographic and clonal assays on 33 individuals yielded mean values (+/- S.D.) of 8.4 (+/- 8.5) X 10(-6) and 10.5 (+/- 6.3) X 10(-6), respectively.
Subject(s)
Antineoplastic Agents/adverse effects , Mutagens , Occupational Diseases/diagnosis , T-Lymphocytes/physiology , Age Factors , Autoradiography , Clone Cells/analysis , DNA/biosynthesis , Environmental Exposure , Health , Humans , Patient Care Team , Smoking/adverse effects , Thioguanine/pharmacologyABSTRACT
Previously reported large autopsy series have indicated that elderly patients who die of cancer are less likely to have metastatic disease than their younger counterparts. This observation could be explained if survival were shorter in the elderly population and patients died with smaller tumor burdens. The authors analyzed Medical Center Hospital of Vermont (MCHV) Tumor Registry data on primary lung cancer with respect to age. As in the reported autopsy series, at the time of diagnosis elderly patients were less likely to have metastatic disease. Further analysis was undertaken of the patients from this series who died and were autopsied at MCHV. Although the total numbers were small, survival was not shorter in the advanced age groups. The authors suggest that elderly patients have slower tumor growth and less metastatic disease, not because of earlier diagnosis and shorter survival, but because of senescent host factors that impede aggressive tumor growth and spread.
