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MLL(KMT2A) 11q23 Gene Rearrangement by FISH

Test Code

F MLL

Test Synonyms

Mixed lineage leukemia, 11q23

Associations

Acute myelogenous leukemia (AML), Acute lymphoblastic leukemia (ALL), HOX gene

Methodology

Fluorescence in situ Hybridization (FISH)

Turnaround Time

3-5 days

Specimen Requirements

5mL peripheral blood in sodium heparin
3mL bone marrow in sodium heparin
Fixed cytogenetically prepared cells in sterile centrifuge tube with pellet visible in 3:1, Methanol:Acetic Acid

Specimen Stability
Blood and bone marrow = 4°C to 25°C, specimens are stable up to 72 hours
Fixed cell pellets are stable for years when stored at -28°C to 15°C
Storage & Handling

4°C to 25°C during transit, but specimens may be transported on refrigerated gel packs. Do not allow the gel pack to come in contact with the specimen. Do not freeze. Extreme temperatures should be avoided.

Causes for Rejection

Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; Insufficient number of cells

Reference Range

A normal cell is expected to show a two orange/green fusion signal pattern. In an abnormal cell, the expected pattern is one green/orange fusion signal, one orange signal, and one green signal.

Description

Mixed lineage leukemia (MLL) abnormalities are frequently found in infant leukemias and therapy-related leukemias.  The MLL gene encodes a DNA-binding protein that methylates histone H3 lysine 4 (H3K4), and positively regulates gene expression including multiple Hox genes. Leukemogenic MLL translocations encode MLL fusion proteins that have lost H3K4 methyltransferase activity. A key feature of MLL fusion proteins is their ability to efficiently transform hematopoietic cells into leukemia stem cells. The link between a chromatin modulator and leukemia stem cells provides support for epigenetic landscapes as an important part of leukemia and normal stem-cell development. FISH can detect this rearrangement in either interphase or metaphase cells.

References
  1. Faber J et al. (2007). Klin Padiatr. Nov-Dec; 219(6):306-11.
  2. Krivtsov AV et al. (2007). Nat Rev Cancer. Nov; 7(11):823-33.