Detection of CBFB/MYH11 transcripts in patients with inversion and other abnormalities of chromosome 16 at presentation and remission

Abstract

The pericentric inversion of chromosome 16 [inv(16)(p13q22)] and t(16;16)(p13;q22) are chromosomal rearrangements frequently associated with AML FAB type M4Eo resulting in the production of a fusion gene CBFB/MYH11. We studied 17 patients with a chromosome 16 abnormality (eight M4Eo, two M1, one M2, three M4 without abnormal eosinophils, three MDS) for the presence of CBFB/MYH11 transcripts using an RT-PCR technique. 10 AML patients with inv(16) tested RT-PCR positive (eight at presentation, one in remission, one in remission and relapse). Three of these patients were originally reported by cytogenetic analysis to have del(16q22) but the positive RT-PCR results prompted a cytogenetic re-examination, resulting in the correction of the reports to inv(16). We show that although inv(16) is closely associated with AML M4Eo, it can also be detected in cases of AML M4 without abnormal eosinophils. Three cases of MDS with inv(16) were also RT-PCR positive. Four patients with other chromosome 16 abnormalities were RT-PCR negative. Four AML patients with inv(16) were studied in remission. All were RT-PCR positive, including one patient in remission for 108 months and one 22 months post allogeneic bone marrow transplant. In the latter two remission patients, RT-PCR evaluation was positive in bone marrow (BM) but not in peripheral blood, suggesting that BM may be the more informative. We conclude that this technique is valuable in the accurate molecular classification of AML, particularly as treatment options may be influenced by such information. Though RT-PCR is highly sensitive in detecting CBFB/MYH11 fusion transcripts during remission, monitoring of minimal residual disease in patients with inv(16) remains to be established.

Detection and quantitation of the CBFβ/MYH11 transcripts associated with the inv(16) in presentation and follow-up samples from patients with AML

“…6 The sensitivity of the PCR test has allowed it to kaemia (AML). The levels of the leukaemia-specific transcripts be used to monitor residual disease following treatment, 4,6,7 are expressed as a ratio to a ubiquitously expressed mRNA species (Abl) which controls for RNA degradation. This techand PCR positivity has been found in patients in long-term nique has been applied to 75 consecutive patients presenting remission.…”

“…This techand PCR positivity has been found in patients in long-term nique has been applied to 75 consecutive patients presenting remission. 6,7 with either de novo AML or tMDS; 6/75 patients analysed wereIn a study of four patients with inversion (16) in patients in complete remission. …”

Assessment of minimal residual disease (MRD) in CBFbeta/MYH11-positive acute myeloid leukemias by qualitative and quantitative RT-PCR amplification of fusion transcripts

“…[8][9][10][11][12][13][14][15][16][17] Indeed, using highly sensitive two-step conventional RT-PCR assays, most authors found AML1/ETO transcripts in almost all patients in CR, even many years after the end of therapy, when they might reasonably be considered cured of their disease. [11][12][13] This latter finding called into question the role of the fusion gene as the unique mutational event involved in the leukemogenesis pathway.…”

True

“…One group detected the persistence of CBFB-MYH11 in long-term remission after allogeneic BMT using nested PCR. 173 In contrast, others have reported the disappearance of CBFB-MYH11 transcripts in patients with long-term follow-up. [174][175][176][177][178] It will be important to determine the clinical value of CBFB-MYH11 monitoring in larger series.…”