Anaplastic lymphoma kinase (ALK) rearrangements, which
are generally associated with pulmonary adenocarcinomas
in female non-smokers, occur in approximately 5% of
patients with non-small cell lung cancer (NSCLC). ALK
rearrangements mostly result from the fusion of the
echinoderm microtubule-associated protein-like 4 (EML4)
with ALK at chromosome 2p23. Fusion of ALK kinase
with EML4 or other fusion partners, such as TFG or
KIF5B, leads to constitutive activation of ALK kinase
[39,42]. Patients with EML4-ALK fusion-positive NSCLC, who were treated with the small-molecule kinase inhibitor
Crizotinib, showed a response rate of 50-60% [8]. 2011 was
the first time that the US FDA simultaneously approved a
novel anti-cancer drug (Crizotinib, Pfizer) and its companion FISH detection kit (ALK FISH probe kit, Abbott
Molecular), which highlighted the critical role of the FISH
assay in guiding ALK-targeted therapy [8,9]. Because ALK
rearrangements are reportedly mutually exclusive with
EGFR/KRAS mutations [43], ALK FISH testing is generally
recommended for patients with wild-type EGFR/KRAS
non-squamous NSCLC