DETECTION OF CBFB MYH11 TRANSCRIPTS IN PATIENTS WITH INVERSION AND OTHER ABNORMALITIES OF CHROMOSOME-16 AT PRESENTATION AND REMISSION/

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 presen tation, one in remission, one in remission and relapse). Three of thes e patients were originally reported by cytogenetic analysis to have de l(16q22) but the positive RT-PCR results prompted a cytogenetic re-exa mination, resulting in the correction of the reports to inv(16). We sh ow that although inv(16) is closely associated with AML M4Eo, it can a lso be detected in cases of AML M4 without abnormal eosinophils. Three cases of MDS with inv(16) were also RT-PCR positive, Four patients wi th other chromosome 16 abnormalities were RT-PCR negative, Four AML pa tients with inv(16) were studied in remission. All were RT-PCR positiv e, including one patient in remission for 108 months and one 22 months post allogeneic bone marrow transplant. In the latter two remission p atients, 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 cla ssification of AML, particularly as treatment options may be influence d 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.