A new myeloblastic leukemia cell line with double minute chromosomes. Induction of methotrexate resistance and dihydrofolate reductase gene amplification

Niigata University School of Medicine, First Department of Internal Medicine, Niigata, Japan; Department of Medicine, Chubu National Hospital, Obu, Japan; Department of Hygiene and Oncology, Kyoto Prefectural University of Medicine, Kyoto, Japan
Leukemia Research (Impact Factor: 2.69). 02/1992; DOI: 10.1016/0145-2126(92)90059-G

ABSTRACT To test the relationship between DMs and drug resistance in newly established AML cell lines, KY821, and its clone KY821A3, the latter had lost DMs during cloning, were cultured in increasing concentrations of MTX, KY821 became resistant against 2 × 10−4 M MTX, whereas KY821A3 did against 2 × 10−5 M MTX in a same period. Enhanced enzyme activities of DHFR were correspondent to the increased DMs numbers and DHFR gene amplification in both resistant clones. The amplified DHFR gene was located on DMs by in situ hybridization. These data indicated that the presence of DMs in KY821 would facilitate the acquisition of drug resistance.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: Molecular change of the deoxycytidine kinase (dCK) gene in a 1-beta-D-arabinofuranosylcytosine-resistant human leukemic cell line (KY-Ra) was investigated. KY-Ra showed the same restriction pattern of genomic DNA and the same nucleotide sequences of the dCK gene as the parental cell line. However, the amount of deoxycytidine kinase mRNA was markedly decreased in KY-Ra compared to the parental cell line. This is the first report showing that the down regulation of dCK gene expression may be affected by a different mechanism than mutation.
    Leukemia and Lymphoma 12/1994; 15(5-6):503-5. · 2.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The p53 gene is currently considered to function as a tumor-suppressor gene in various human malignancies. In hematologic malignancies, alterations in the p53 gene have been shown in some human leukemias and lymphomas. Although mutations in the p53 gene are infrequent in acute myelogenous leukemia (AML) patients, we show in this report that alterations in the p53 gene are frequent in myeloid leukemia cell lines. We studied alterations of the p53 gene in nine human myeloid leukemia cell lines by reverse transcriptase-polymerase chain reaction (RT-PCR), single-strand conformation polymorphism (SSCP) analysis, and direct sequencing. Expression of the p53 gene was not detected at all by RT-PCR in two of the nine cell lines. In these two cell lines, Southern blot analysis showed gross rearrangements and deletions in both of the p53 alleles. Six of the nine cell lines were found to express only mutant p53 mRNA by RT-PCR/SSCP analysis and direct sequencing, and wild-type p53 mRNA was not detected. Two of the mutant p53 mRNAs were shown to be products of abnormal splicing events induced by intronic point mutations. Taken together, eight of nine human myeloid leukemia cell lines expressed no or an undetectable amount of wild-type p53 mRNA. Three of the eight cell lines were growth factor-dependent. Our results suggest that inactivation of the p53 gene may be a common feature in myeloid leukemia cell lines and may play an important role in the establishment of these cell lines.
    Blood 06/1992; 79(9):2378-83. · 9.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The studies described below were carried out to analyze the damage induced by DNA active drugs to episomal (Epstein-Barr virus, EBV) DNA in the Raji Burkitt's lymphoma cell line. This work: (i) applies pulsed-field gel electrophoresis (PFGE) techniques to quantify DNA damage on a large (approximately 180 kbp), circular target, (ii) investigates the DNA strand-scission behavior of different classes of drugs on the EBV episome, and (iii) compares EBV episomal damage to that generated in genomic DNA in the Raji cell line. Cells were treated with ionizing radiation to induce random strand scission, and the migration of topological forms of EBV was measured using PFGE. DNA damage induced in the episome by DNA active drugs was then assayed. Three drugs, acting by different types of DNA interactive mechanisms, were used: bleomycin, an intercalative DNA strand-scission agent; and amsacrine (mAMSA) and teniposide (VM26), intercalative and nonintercalative topoisomerase II active drugs, respectively. Rad equivalency of damage was determined by comparing the drug-induced change in percentage of Forms I and III to that generated by ionizing radiation. Additionally, single- and double-strand scission induced in genomic (total cellular) DNA by X-rays, bleomycin, amsacrine, and teniposide were assayed by high-sensitivity alkaline and neutral filter elution techniques. We demonstrate that pulsed-field gel electrophoresis is a useful technique for measuring form conversion in large episomal DNA. While all three drugs effect both episomal and genomic DNA strand scission, bleomycin appears to preferentially damage the EBV episome. The topoisomerase II active drugs mAMSA and VM26 show no evidence of episome-directed damage in this system and, in fact, damage genomic DNA at somewhat higher rates.
    Analytical Biochemistry 08/1994; 220(1):103-14. · 2.31 Impact Factor