Establishment and Characterization of a Novel Human Myeloid Leukemia Cell Line, AMU-AML1, Carrying t(12;22)(p13;q11) with No Fusion of MN1-TEL

Abstract 4375

Leukemia cell lines are ubiquitous powerful research tools that are available to many investigators. In balanced chromosomal aberration in leukemia, a chimeric fusion gene formed by genes existing on breakpoints is frequently related to leukemogenesis. Cytogenetic abnormalities of chromosome band 12p13 are detected non-randomly in various hematological malignancies and usually involved TEL, which encodes a protein of the ETS transcription factor family. Chromosome band 22q11-12 is one of partners of translocation 12p13 and t(12;22)(p13;q11-12) results in fusion of TEL and MN1 or in just the partial inactivation of TEL. It is important to analyze precisely the breakpoint in a non-random translocation such as t(12;22)(p13;q11-12) and in addition it contributes to the better understanding of the molecular pathogenesis of leukemogenesis.

In this study, we established a novel human myeloid leukemia cell line, AMU-AML1, having t(12;22) from a patient with acute myeloid leukemia with multilineage dysplasia and analyzed its characters. Mononuclear cells were isolated by Ficoll-Hypaque sedimentation from patient's bone marrow before initiation of chemotherapy and cultured in RPMI 1640 supplemented with 10% heat-inactivated fetal bovine serum (FBS). After 3 months, cell proliferation became continuous. The cell line, named AMU-AML1, was established. In AMU-AML1, the following pathogens were negative for EBV, CMV, HBV, HCV, HIV-1, HTLV-1 and mycoplasma. A doubling time of AMU-AML1 cells was about 96 hours. Proliferation of the cells was stimulated by rhG-CSF (10 ng/ml), rhGM-CSF (10 ng/ml), M-CSF (50 ng/ml), rhIL-3 (10 ng/ml) and rhSCF (100 ng/ml) but not by IL-5 (10 ng/ml), rhIL-6 (10 ng/ml), and rhEPO (5 U/ml). AMU-AML1 was positive for CD13, CD33, CD117 and HLA-DR, negative for CD3, CD4, CD8 and CD56 by flow cytometry analysis. G-banding combined with SKY analysis of AMU-AML1 cells showed single structural abnormality; 46, XY, t(12;22)(p13;q11.2). Double-color FISH using PAC/BAC clones listed in NCBI website and array CGH analyses indicated that the breakpoint in 12p13 was within TEL or telomeric to TEL and it of 22q11 was centromeric to MN1. A chimeric MN1-TEL transcript and fusion protein of MN1-TEL could not be detected by RT-PCR and western blot analysis. The wild type of MN1 protein was strongly expressed in AMU-AML1 compared with other leukemic cell lines with t(12;22), MUTZ-3 and UCSD/AML1.

Our data suggest that AMU-AML1 had a t(12;22)(p13;q11.2) without fusion of MN1-TEL and the expression level of MN1 protein was relatively high, which might have some effects on leukemogenesis. In conclusion, AMU-AML1 is a useful cell line to analyze the biological consequences of the leukemic cells with t(12;22)(p13;q11.2) but no fusion of MN1-TEL.