A novel KIF5B-ALK variant in nonsmall cell lung cancer

The anaplastic lymphoma kinase (ALK) gene is involved frequently in chromosomal translocations, resulting in fusion genes with different partners found in various lymphoproliferative conditions. It was recently reported in nonsmall cell lung cancer (NSCLC) that the fusion protein encoded by echinoderm microtubule-associated protein-like 4-ALK (EML4-ALK) fusion gene conferred oncogenic properties. The objective of the current study was to identify other possible ALK fusion genes in NSCLC.

Immunohistochemical analysis was used to screen for aberrant ALK expression in primary NSCLC. The authors used 5' rapid amplification of complementary DNA ends to screen for potential, novel 5' fusion partners of ALK other than EML4-ALK. Reverse transcriptase-polymerase chain reaction and fluorescence in situ hybridization analyses were used to confirm the identity of 5' fusion partners. The genomic breakpoint was verified using genomic sequencing. Overexpression of the novel ALK fusion gene and variants 3a and 3b of EML4-ALK was performed to assess downstream signaling and functional effects.

The authors identified a novel gene resulting from the fusion of kinesin family member 5B (KIF5B) exon 15 to ALK exon 20 in a primary lung adenocarcinoma. Western blot analysis of clinical tumor tissues revealed the expression of a protein whose size correlated with that of the predicted KIF5B-ALK. Overexpression of KIF5B-ALK in mammalian cells led to the activation of signal transducer and activator of transcription 3 and protein kinase B and to enhanced cell proliferation, migration, and invasion.

The discovery of the novel KIF5B-ALK variant further consolidated the role of aberrant ALK signaling in lung carcinogenesis.