Screening for EML4-ALK fusion genes in Chinese male never-smokers with NSCLC. (A) DNA gel electrophoresis showing the expression of EML4-ALK fusion genes (top panel) and ABL controls (bottom panel) by one-step real time RT-PCR in Chinese male never-smokers. One sample is shown for each detected fusion variant (V1, V2, V3a, V4a, and V5a) as indicated below the case numbers. NC, negative case; M, DNA ladder. (B) The frequency of different EML4-ALK variants. (C) ALK Break Apart FISH analysis showing ALK inversion in an EML4-ALK-negative (ALK-, left) and –positive (ALK+, right) carcinoma tissue. The inversion is indicated by two separated red and green fluorescent dots that are used to label two probes targeting the sequences flanking the breaking point. One such example is indicated by a pair of arrows in ALK + image.