Mixed lineage leukemia, 11q23
Acute myelogenous leukemia (AML), Acute lymphoblastic leukemia (ALL), HOX gene
Fluorescence in situ Hybridization (FISH)
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
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)
Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; Insufficient number of cells
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.
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.