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Detection of fusion transcripts generated by the inversion 16 chromosome in acute myelogenous leukemia
1Department of Hematology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Abstract:
Pericentric inversion of chromosome 16 [inv(16)(p13q22)] and the related t(16;16)(p13;q22) are seen in a subset of acute myelogenous leukemia (AML) phenotypically and prognostically differing from other cases. We have recently shown that inv(16) results in fusion of CBFB/PEBP2B, a gene encoded at 16q22 to MYH11, a smooth muscle myosin heavy chain gene encoded at 16p13. Chimeric transcripts consisting of upstream CBFB fused to downstream MYH11 coding sequences result from this fusion. In this study we have examined a series of 37 of these cases using reverse transcriptase-polymerase chain reaction (RT-PCR) to detect expression of a hybrid CBFB/MYH11 transcript. Chimeric cDNAs were detected in all but 1 of 37 leukemias with typical inv(16) or t(16;16). Such chimeric products were not seen in a case with inv(16)(p13q24) (ie, a variant q arm breakpoint) or any of 10 cases of AML without these chromosomal changes. Four different chimeric transcripts were found, representing differing fusion points within MYH11 spliced to position 495 of CBFB. Primer sets are described for efficient amplification of these different cDNA forms. Amplification of cDNA showed that all but 17 codons of the CBFB coding sequence are included in the abnormal transcripts. RT-PCR was shown to be highly sensitive and potentially useful for detection of leukemic cells during morphologic remission.
Insights
The study found that a specific chromosomal abnormality in acute myelogenous leukemia (AML) creates a hybrid CBFB/MYH11 transcript. This finding, detected by RT-PCR, could help identify leukemia cells during remission.
Area of Science:
- Hematology
- Molecular Biology
- Genetics
Background:
- Pericentric inversion of chromosome 16 [inv(16)(p13q22)] and t(16;16)(p13;q22) define a distinct subset of acute myelogenous leukemia (AML).
- These chromosomal changes lead to the fusion of the CBFB gene (16q22) with the MYH11 gene (16p13), creating chimeric transcripts.
Purpose of the Study:
- To detect the expression of hybrid CBFB/MYH11 transcripts in AML cases with inv(16) or t(16;16).
- To assess the utility of RT-PCR for identifying these specific leukemic cells.
Main Methods:
- Analysis of 37 AML cases with typical inv(16) or t(16;16) using reverse transcriptase-polymerase chain reaction (RT-PCR).
- Comparison with a variant inv(16) case and AML cases lacking these chromosomal changes.
- Characterization of different chimeric transcript forms and development of primer sets for amplification.
Main Results:
- Hybrid CBFB/MYH11 cDNAs were detected in 36 out of 37 AML cases with typical inv(16) or t(16;16).
- No chimeric products were found in a variant inv(16) case or in AML cases without these specific chromosomal alterations.
- Four distinct chimeric transcript variants were identified, with varying fusion points within MYH11 and inclusion of most of the CBFB coding sequence.
Conclusions:
- RT-PCR is a highly sensitive method for detecting CBFB/MYH11 chimeric transcripts in AML.
- This technique holds potential for the detection of minimal residual disease during morphologic remission in AML patients with inv(16) or t(16;16).