A new human acute monocytic leukemia cell line SHI-1 with t(6;11)(q27;q23), p53 gene alterations and high tumorigenicity in nude mice

Abstract

BACKGROUND AND OBJECTIVES: Human leukemia cell lines are of great value in leukemia research. Thus far 36 leukemia cell lines carrying the 11q23 translocation and MLL rearrangements, including two cell lines with t(6;11)(q27;q23) and an MLL-AF6 fusion gene have been described. We have established a new monocytic cell line with t(6;11), designated SHI-1, and herein describe its biological characteristics. DESIGN AND METHODS: Mononuclear cells isolated from the bone marrow of a patient with acute monocytic leukemia (AML-M5b) at relapse were inoculated and passaged by liquid culture. The biological features of the cell line were characterized by morphological assays, flow cytometry, cytogenetic analysis, reverse transcription polymerase chain reaction (RT-PCR), direct sequencing, fluorescence in situ hybridization (FISH), clonogenic culture, quantitative fluorescent PCR, zymography, short tandem repeating sequences-PCR (STR-PCR), multiplex-FISH (M-FISH), and tumorigenic capacity in nude mice. RESULTS: The SHI-1 cell line has been maintained in continuous culture without any external cytokines for three years. The morphology and immunoprofile of the cells show typical features of monocytic lineage. Karyotypic analysis demonstrated a t(6;11)(q27;q23) translocation accompanied by a deletion of 17p, which are the same abnormalities as were seen in the leukemia cells of this patient in relapse. The MLL-AF6 fusion transcript and the loss of one p53 allele were proven by chromosome painting, FISH and RT-PCR analysis in both SHI-1 cells and the primary leukemia cells. A point mutation of ATC-->ACC at codon 195 of exon 6 in another p53 allele was found by direct sequencing of DNA in SHI-1 cells as well as in the primary leukemia cells. Neither Epstein-Barr virus nor mycoplasma was detected in SHI-1 cells. Tumor masses were found in all sixteen mice 9-19 days after subcutaneous injection of SHI-1 cells. DNA fingerprinting confirmed the authenticity of the cell line. INTERPRETATION AND CONCLUSIONS: SHI-1 is a new monocytic leukemia cell line with the t(6;11) translocation, p53 gene alterations, and high tumorigenicity in nude mice. It could be a valuable tool in the study of leukemogenesis.