The AML1 component consists of a 156kb probe, labelled in red, located centromeric to the AML1 (RUNX1) gene that spans the CLIC6 gene and a 169kb probe covering part of the AML1 (RUNX1) gene, including markers SHGC-87606 and D21S1921. The ETO (RUNX1T1) component, labelled in green, consists of a 151kb probe covering the centromeric part of the gene and the flanking region and a 194kb probe covering the telomeric part of the gene and the flanking region.
The RUNX1 (RUNX family transcription factor 1) gene at 21q22.1 is fused with the RUNX1T1 (RUNX1 partner transcriptional co-repressor 1) gene at Ensembl location 8q21.3, in the t(8;21)(q21.3;q22.1) translocation, found most commonly in patients with acute myeloid leukaemia (AML) FAB (French-American-British classification) type M2.
AML with a RUNX1::RUNX1T1 fusion resulting from a t(8;21)(q21.3;q22.1) translocation is a recognised disease entity according to the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia1. The translocation is observed in 10%-22% of patients with AML FAB type M2 and 5%-10% of AML cases overall, most commonly in children and young adults2 and is a good prognostic indicator3,4,5. The t(8;21) breakpoint mainly occurs in the intron between exons 5 and 6 just before the transactivation domain and fusion protein created contains the DNA-binding domain of RUNX1 fused to the transcription factor RUNX1T12.
In addition to the reciprocal t(8;21) translocation creating the RUNX1::RUNX1T1 fusion, variant translocations have also been reported. These variant rearrangements may be cryptic and easily overlooked by G-banding; however, FISH can indicate the presence of such rearrangements2.
Microscope image
The CytoCell® AML1/ETO (RUNX1/RUNX1T1) Translocation, Dual Fusion Probe is a qualitative, non-automated, fluorescence in situ hybridisation (FISH) test used to detect chromosomal rearrangements between the 21q22.1 region on chromosome 21 and the 8q21.3 region on chromosome 8 in Carnoy’s solution (3:1 methanol/acetic acid) fixed haematologically-derived cell suspensions from patients with confirmed or suspected acute myeloid leukaemia (AML).
This device is designed as an adjunct to other clinical and histopathological tests in recognised diagnostic and clinical care pathways, where knowledge of AML1::ETO (RUNX1::RUNX1T1) translocation status would be important for clinical management.
This device is designed to detect rearrangements with breakpoints in the region covered by the red and green clones in this probe set, which includes the AML1 and ETO (RUNX1 and RUNX1T1) regions. Breakpoints outside this region, or variant rearrangements wholly contained within this region, may not be detected with this device.
This device is not intended for: use as a stand-alone diagnostic, use as a companion diagnostic, prenatal testing, population-based screening, near-patient testing, or self-testing.
This device has not been validated for sample types, disease types, or purposes outside of those stated in the intended purpose.
It is intended as an adjunct to other diagnostic laboratory tests and therapeutic action should not be initiated on the basis of the FISH result alone.
Reporting and interpretation of FISH results should be performed by suitably qualified staff, consistent with professional standards of practice, and should take into consideration other relevant test results, clinical and diagnostic information.
This device is intended for laboratory professional use only.
Failure to adhere to the protocol may affect the performance and lead to false positive/negative results.
We have been working with CytoCell fish probes for 2 decades because of their excellent clarity and intensity regardless of the size of the probe. It is so clear and simple to detect. The available probes are created as a best solution for detection of most frequent rearrangements in routine diagnostic and has high hybridization rate. Also, we are very pleased with the choice of probes that perfectly meets the needs of our laboratory. Special impression left the fact that technical support is provided by the people who worked in the laboratory and who are close to the problems we face, so they have the appropriate solution.
Dr Marina Djurisic
Head of Laboratory of Medical Genetics, Mother and Child Health Care Institute of Serbia “Dr Vukan Cupic”, Belgrade, Serbia
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