F ALK; FP ALK
2p23 rearrangement; EML4-ALK; Non small cell lung cancer
The FDA has approved Crizotinib (Xalkori) for treatment of patients with locally advanced or metastatic NSCLC that is ALK-positive. The ALK Break-Apart FISH Probe Kit detects rearrangement of the anaplastic lymphoma kinase (ALK) gene in NSCLC. Up to 5% of non-squamous NSCLC carry ALK gene rearrangements. Patients negative for EGFR mutations benefit minimally from chemotherapy and are resistant to TKI's. Crizotinib blocks certain kinases including those produced by abnormal ALK gene rearrangement.
A retrospective analysis by Shaw et al, published in Lancet Oncology, showed that ALK-positive NSCLC patients treated with Crizotinib did have improved, two-year survival compared with that of Crizotinib-naive controls.
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
10% neutral buffered formalin fixed paraffin embedded tissue
Whole blood and bone marrow, ship ambient
Fresh tissue, FNA or paraffin embedded tissue, 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; Improper fixative
FISH results indicate whether rearrangement is present or absent.
In a normal cell, two yellow (orange/green fused) signals will be seen.
In a cell with a translocation involving ALK, one orange and one green signal will be seen along with one yellow signal.
The LSI dual break-apart rearragement probe contains two differently labelled probes on either sides of the breakpoint of the ALK gene. ALK has multiple fusion partners including NPM in anaplastic large cell lymphoma and EML4 in non small cell lung cancer.
EML4/ALK fusions are the result of paracentric inversions involving the short arm of chromosome 2. The breakpoints of the inversions are within the EML4 locus (2p21) and the ALK locus (2p23).