Pre‐clinical evaluation of probes to detect t(8;21) AML minimal residual disease by fluorescence in situ hybridization

Abstract

The 8;21 translocation in acute myeloid leukemia (AML) results in a consistent fusion transcript, AML1/ETO. Long-term clinical remission occurs in some patients despite incomplete eradication of AML1/ETO as demonstrated by RT-PCR, thus limiting the usefulness of this assay. An important future goal will be to determine if there is a level of minimal residual disease (MRD) in patients below which relapse is unlikely. For the detection of MRD, we have developed reagents for fluorescence in situ hybridization (FISH) that identify both derivative 8 and 21 chromosomes with a high analytical sensitivity. In t(8;21) AML cells, two fused signals were detected in addition to the normal 8 and 21 alleles. The sensitivity and specificity of this probe mixture were analyzed in cell lines and patient bone marrows. One and two randomly juxtaposed signals were observed in 2.4 and 0.04% of normal cells, respectively. However, these were easily differentiated from t(8;21) cells by the absence of signals from the normal alleles. Using as criteria the presence of two fused signals plus the normal alleles, we observed no false positives among 5,000 normal cells. The probe correctly identified 20/20 patients with t(8;21) AML and 10/10 non-t(8;21) patients. In cell dilution experiments, the analytical sensitivity of this reagent was equal to that of the X chromosome and Y chromosome alpha-satellite probes. These optimized probes should facilitate the quantitative assessment and study of MRD in t(8;21) AML.

i(Xq10) in female patients

“…Additional chromosome abnormalities were observed in 26/28 patients. i(X)(q10) has been demonstrated in six cases with RUNX1 / RUNX1T1 AML (Shiraishi et al, 1982;Minamihisamatsu et al, 1988;Tien et al, 1988;Kwong et al, 1993;Ma et al, 1997;Paskulin et al, 1998) , two cases with TCF3 / PBX1 ALL (Pui et al, 1990; Gindina T, table 1, #18) and one case with KMT2A / AFF1 (Arthur et al, 1982). Associated in combination with other isochromosomes in 4 patients (Dave et al, 2002;Adeyinka et al, 2007;Trcic et al, 2010;Pang et al, 2015), del(9q) in 3 patients (Tien et al, 1988;Han et al, 2002; Gindina T, table 1, #19) and extra chromosome 21 in 2 (Kearns et al, 2004;Pui et al, 1992).…”

“…Acute myeloid leukemia (AML): there were 8 patients with AML-M2, six of them had translocation t(8;21)(q22;q22) (Shiraishi et al, 1982;Minamihisamatsu et al, 1988;Tien et al, 1988;Kwong et al, 1993;Ma et al, 1997;Paskulin et al, 1998).…”