Blood, Vol. 92 No. 11 (December 1), 1998:
pp. 4336-4343
2
,5-Oligoadenylate-Antisense Chimeras Cause RNase L to Selectively
Degrade bcr/abl mRNA in Chronic Myelogenous Leukemia Cells
Avudaiappan Maran,
Cornelius F. Waller,
Jayashree M. Paranjape,
Guiying Li,
Wei Xiao,
Kerry Zhang,
Matt E. Kalaycio,
Ratan K. Maitra,
Alan E. Lichtin,
Wolfram Brugger,
Paul F. Torrence, and
Robert
H. Silverman
From the Department of Cancer Biology, The Lerner Research Institute,
and Department of Hematology and Oncology, Cleveland Clinic Foundation,
Cleveland, OH; Section on Biomedical Chemistry, National Institute of
Diabetes and Digestive and Kidney Diseases, National Institutes of
Health, Bethesda, MD.
We report an RNA targeting strategy, which selectively degrades
bcr/abl mRNA in chronic myelogenous leukemia (CML) cells. A
2
,5-tetraadenylate activator (2-5A) of RNase L was chemically linked
to oligonucleotide antisense directed against either the fusion site or
against the translation start sequence in bcr/abl mRNA. Selective
degradation of the targeted RNA sequences was demonstrated in assays
with purified RNase L and decreases of p210bcr/abl kinase
activity levels were obtained in the CML cell line, K562. Furthermore,
the 2-5A-antisense chimeras suppressed growth of K562, while having
substantially reduced effects on the promyelocytic leukemia cell line,
HL60. Findings were extended to primary CML cells isolated from bone
marrow of patients. The 2-5A-antisense treatments both suppressed
proliferation of the leukemia cells and selectively depleted levels of
bcr/abl mRNA without affecting levels of 
-actin mRNA, determined by
reverse transcriptase-polymerase chain reaction (RT-PCR). The
specificity of this approach was further shown with control
oligonucleotides, such as chimeras containing an inactive dimeric form
of 2-5A, antisense lacking 2-5A, or chimeras with altered sequences
including several mismatched nucleotides. The control oligonucleotides
had either reduced or no effect on CML cell growth and bcr/abl mRNA
levels. These findings show that CML cell growth can be selectively
suppressed by targeting bcr/abl mRNA with 2-5A-antisense for decay by
RNase L and suggest that these compounds should be further explored for
their potential as ex vivo purging agents of autologous hematopoietic
stem cell transplants from CML patients.
