metallothionein and Leukemia--Myeloid

Zinc status is difficult to evaluate in humans. Metallothionein gene expression is transcriptionally regulated by dietary zinc and thus could serve as an assessment parameter based on zinc-dependent function. We used semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to establish that MT mRNA is increased in a human monocytic cell line by addition of zinc to the medium. To examine this response in human subjects, a dietary supplement of 50 mg zinc gluconate/d was given for 15 d. Monocytes were purified from venous blood using NycoPrep 1.068. Monocyte purity was determined by flow cytometry using fluorescent anti-human monocyte CD14 antibodies. Total monocyte RNA was extracted and converted to cDNA by reverse transcription. Competitive RT-PCR was used to analyze differences between cDNA levels that are proportional to MT mRNA levels in monocytes from zinc-supplemented and control subjects. RT-PCR oligonucleotide primers were designed to amplify both a 201 bp segment of the human MT cDNA and a 180 bp competitor cDNA template. The 180 bp competitor cDNA template was used for MT cDNA quantitation. The RT-PCR data show that there was a significant increase in monocyte MT mRNA in subjects within 6 d of zinc supplementation, which remained elevated at d 15 of supplementation. In contrast, plasma zinc was greater at d 6 of zinc supplementation, but by d 15 of supplementation, while still elevated, was close to control levels. These data suggest that monocyte MT mRNA levels respond to zinc supplementation and that the response could serve as a more useful assessment variable than plasma zinc for the measurement of zinc status in humans.

Topics: Adult; Analysis of Variance; Base Sequence; Blotting, Northern; Cell Separation; Cells, Cultured; DNA, Complementary; Electrophoresis, Polyacrylamide Gel; Flow Cytometry; Food, Fortified; Gene Expression Regulation; Gene Expression Regulation, Neoplastic; Humans; Leukemia, Myeloid; Male; Metallothionein; Monocytes; Polymerase Chain Reaction; RNA-Directed DNA Polymerase; RNA, Messenger; Tumor Cells, Cultured; Zinc

A 75-year-old man with chronic myelomonocytic leukemia was found to have a constitutional t(6;16)(q13;q22) translocation, as did his healthy daughter. Chromosomal in situ hybridization studies of the daughter's lymphocytes did not indicate translocation-mediated interruption of the metallothionein gene cluster, at 16q22, although this locus has been reported to be involved in the eosinophilic variant of acute myelomonocytic leukemia. Lymphocytes from the daughter and from the patient's brother (who had a normal karyotype), had no increased fragility at 16q22. The findings do not provide evidence for an association between the familial chromosome abnormality and this patient's leukemia.

Topics: Aged; Chromosomes, Human, Pair 16; Chromosomes, Human, Pair 6; Female; Genetic Markers; Humans; Karyotyping; Leukemia, Myeloid; Male; Metallothionein; Multigene Family; Nucleic Acid Hybridization; Pedigree; Translocation, Genetic