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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

2.0 mL (min. 1.0 mL) peripheral blood in sodium heparin preferred, EDTA accepted
1.0 mL (min. 0.5 mL) bone marrow in sodium heparin preferred, EDTA accepted
5 mm^3 fresh tissue or 3.0 mL (min. 2.0 mL) FNA in MPLN RPMI media

Specimen Stability
Peripheral blood and bone marrow stable at 18-25°C for 72 hours
Fresh tissue or FNA stable at 2-8°C for 72 hours
Storage & Handling

Whole blood and bone marrow, ship ambient
Fresh tissue or FNA ship in a Styrofoam container with a cool/refrigerated pack (Do not allow cool pack to directly contact sample)

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.