TY - JOUR
T1 - Lack of IRF-1 expression in acute promyelocytic leukemia and in a subset of acute myeloid leukemias with del(5)(q31)
AU - Green, W. B.
AU - Slovak, M. L.
AU - Chen, I. M.
AU - Pallavicini, M.
AU - Hecht, J. L.
AU - Willman, C. L.
N1 - Funding Information:
This work was supported by ACS Grant EDT-71, DHHS Grants NIH NCI CA32102 supporting the SWOG Leukemia Research and Cytogenetics Programs, and by Dedicated Health Research Funds from the State of New Mexico. M.L.S. is a member of the City of Hope Cancer Center Program and is supported in part by CA33572 and CA30206. The authors acknowledge the excellent technical expertise of L Ashley in performing the interphase FISH studies. We further acknowledge the Center for Molecular and Cellular Diagnostics laboratory personnel for molecular analysis of the t(15;17) breakpoints from all APL patient samples, J Fazio for technical assistance in RNA isolations and for making the internal standard RNA used for the RT-PCR assay, and M Crisell and C Snyder for contributing to the cloning of the IRF-1 splice junctions. The authors thank T Taniguchi and H Harada for kindly providing the pUChIRF-1 plasmid containing the IRF-1 cDNA from which the internal standard RNA was constructed, and M Lanotte for kindly providing the NB4 cell line.
PY - 1999
Y1 - 1999
N2 - One allele of interferon regulatory factor-1 (IRF-1), a transcriptional activator of genes critical for growth suppression, differentiation, and apoptosis, is usually deleted in acute myeloid leukemias (AML) and myelodysplasias (MDS) with deletion of chromosome 5q31. Accelerated exon skipping of IRF-1, resulting in transcripts lacking a translation initiation site, has been hypothesized as a means of functional inactivation of IRF-1 in AML/MDS. To test this hypothesis, we developed quantitative competitive RT-PCR assays to measure levels of full length and exon-skipped IRF-1 transcripts and measured IRF-1 proteins by Western blotting in a series of 45 samples of AML (13: -5/del5(q); 11: t(15;17); 7: t(8;21); and 7: inv(16)), normal blood and marrow, and myeloid cell lines. In contrast to AMLs with inv(16) or t(8;21), two AML samples with del(5q) had accelerated exon skipping and relatively low levels of full-length transcripts, while a third sample had very low transcript levels; IRF-1 proteins were not expressed and could not be induced by interferon gamma (IFNγ). An additional six AML cases with -5/del(5q) had moderate exon-skipping and lacked constitutive IRF-1 proteins; however IRF-1 proteins were IFNγ-inducible. Unexpectedly, all primary acute promyelocytic leukemia (APL) samples lacked IRF-1 protein and most exhibited accelerated exon skipping; furthermore, IRF-1 could not be induced by IFNγ or all-trans retinoic acid (ATRA) which both induce IRF-1 in the NB4 APL cell line. Thus, accelerated exon skipping results in a loss of IRF-1 expression and function that cannot be overcome by exposure to inducing agents in a subset of AML patients with -5/del(5q) and in APL.
AB - One allele of interferon regulatory factor-1 (IRF-1), a transcriptional activator of genes critical for growth suppression, differentiation, and apoptosis, is usually deleted in acute myeloid leukemias (AML) and myelodysplasias (MDS) with deletion of chromosome 5q31. Accelerated exon skipping of IRF-1, resulting in transcripts lacking a translation initiation site, has been hypothesized as a means of functional inactivation of IRF-1 in AML/MDS. To test this hypothesis, we developed quantitative competitive RT-PCR assays to measure levels of full length and exon-skipped IRF-1 transcripts and measured IRF-1 proteins by Western blotting in a series of 45 samples of AML (13: -5/del5(q); 11: t(15;17); 7: t(8;21); and 7: inv(16)), normal blood and marrow, and myeloid cell lines. In contrast to AMLs with inv(16) or t(8;21), two AML samples with del(5q) had accelerated exon skipping and relatively low levels of full-length transcripts, while a third sample had very low transcript levels; IRF-1 proteins were not expressed and could not be induced by interferon gamma (IFNγ). An additional six AML cases with -5/del(5q) had moderate exon-skipping and lacked constitutive IRF-1 proteins; however IRF-1 proteins were IFNγ-inducible. Unexpectedly, all primary acute promyelocytic leukemia (APL) samples lacked IRF-1 protein and most exhibited accelerated exon skipping; furthermore, IRF-1 could not be induced by IFNγ or all-trans retinoic acid (ATRA) which both induce IRF-1 in the NB4 APL cell line. Thus, accelerated exon skipping results in a loss of IRF-1 expression and function that cannot be overcome by exposure to inducing agents in a subset of AML patients with -5/del(5q) and in APL.
KW - Acute myeloid leukemia
KW - Acute promyelocytic leukemia
KW - Chromosome 5q
KW - Exon-skipping
KW - Interferon regulatory factor-1
KW - t(15;17)
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U2 - 10.1038/sj.leu.2401596
DO - 10.1038/sj.leu.2401596
M3 - Article
C2 - 10602416
AN - SCOPUS:0032733441
SN - 0887-6924
VL - 13
SP - 1960
EP - 1971
JO - Leukemia
JF - Leukemia
IS - 12
ER -