Characterization and Use of an Antibody Detecting the CBF
-SMMHC
Fusion Protein in inv(16)/t(16;16)-Associated Acute Myeloid Leukemias
David S. Viswanatha,
I.-Ming Chen,
Pu Paul Liu,
Marilyn L. Slovak,
Cathy Rankin,
David R. Head, and
Cheryl L. Willman
From the Department of Pathology and Cancer Center, University of New
Mexico School of Medicine, Albuquerque, NM; the National Human Genome
Research Institute, National Institutes of Health, Bethesda, MD; the
City of Hope National Medical Center, Duarte, CA; the Southwest
Oncology Group (SWOG) Statistical Center, Seattle, WA; and St Judes
Childrens Research Hospital, Memphis, TN.
The inv(16)(p13q22) and t(16;16)(p13;q22) cytogenetic abnormalities
occur commonly in acute myeloid leukemia (AML), typically associated
with French-American-British (FAB) AML-M4Eo subtype. Reverse
transcriptase-polymerase chain reaction (RT-PCR)
techniques have been recently developed to detect the presence of
several variants of the resultant CBFB-MYH11 fusion gene that
encodes a CBF
-smooth muscle myosin heavy chain (SMMHC) fusion
protein. We have now determined the clinical use of a polyclonal
antibody [anti-inv(16) Ab] directed against a junctional epitope of
the most common type of CBF-SMMHC fusion protein (type A), which is
present in 90% of inv(16)/t(16;16) AML cases. Using flow cytometry, reproducible methods were developed for detection of CBF-SMMHC proteins in permeabilized cells; flow cytometric results were then
correlated with cytogenetics and RT-PCR detection methods. In an
analysis of 42 leukemia cases with various cytogenetic abnormalities and several normal controls, the anti-inv(16) Ab specifically detected
all 23 cases that were cytogenetically positive for inv(16) or
t(16;16), including a single AML case that was RT-PCR-negative. In
addition to detecting all type A fusions, the anti-inv(16) Ab also
unexpectedly identified the type C and type D CBF-SMMHC fusion
proteins. Molecular characterization of one RT-PCR-positive and
Ab-positive t(16;16) case with a non-type A product showed a novel
previously unreported CBFB-MYH11 fusion (CBFB nt
455-MYH11 nt 1893). Flow cytometric results were analyzed using
the Kolmogorov-Smirnov statistic D-value and the median value for
positive samples was 0.65 (range, 0.35 to 0.77) versus 0.07 (range,
0.21 to 0.18) in the negative group (P < .0001). The
overall concordance between cytogenetics and RT-PCR was 97%, whereas
the concordance between flow cytometry and cytogenetics was 100%.
Thus, using the anti-inv(16) Ab, all cytogenetically positive and
RT-PCR-positive AML cases with inv(16) or t(16;16) could be rapidly
identified. This study demonstrates the use of this antibody as an
investigational tool in inv(16)/t(16;16) AML and suggests that the
development of such reagents may have potential clinical diagnostic
use.
Blood, Vol. 91 No. 6 (March 15), 1998:
pp. 1882-1890
© 1998 by The American Society of Hematology.
