Diversity of EML4-ALK fusion variants in non-small cell lung cancer

Objective To investigate the fusion sequence complexity of EML4-ALK in non-small cell lung cancer (NSCLC) patients, and the potential mutation in tyrosine kinase (TK) domain of ALK gene. Methods In routine practice，a novel echinoderm microtubule-associated protein-like4 and anaplastic lymphoma kinase (EML4-ALK) V3c variant was detected by rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR)-sequencing technology in a patient with NSCLC.The further consecutive 39 cases（total of 40 cases）were screened by use of reverse transcription（RT）-PCR for EML4-ALK fusion.Positive PCR products were purified and cloned into T vectors, transformed into DH5a germ cells and colony picked up and sequenced for sequence complexity analysis.Tyrosine kinase domain of ALK was amplified by RT-PCR and sequenced. Results Three out of 40 cases had EML4-ALK fusion.One case had six novel variants of EML4-ALK co-existing, termed as V3c(64.6%)，V3d(25.0%)，V3e(2.1%)，V3f(4.2%)，V3g(2.1%)and V3h(2.1%) variants, whereas without common V3a and V3b variants. In other two positive cases, one was V1 variant, another was concurrent V2, V3a and V3b variants.No mutations were detected in the TK domain of EML4-ALK in any case. Conclusions Several EML-ALK variants could co-exist in a given lung cancer tissue, which suggest that the diversity and sequence complexity of EML4-ALK fusion are exist.Attentions should be paid to screen all the variants in clinic to improve the pick-up rate.(Chin J Lab Med, 2012,35:593-597) Key words: Lung neoplasms; Carcinoma，non-small-cell lung; Oncogene proteins，fusion; Protein-tyrosine kinases; Polymerase chain reaction; Mutation