Expression of ALK mRNA in Chinese male never-smokers with NSCLC. The expression level of ALK mRNA in each carcinoma (total 95 specimens) was determined by one-step real time RT-PCR using primers specific to the ALK TK domain and presented as the intensity normalized to the housekeeping gene ABL. While ALK mRNA is not expressed or expressed at very low levels in EML4-ALK negative carcinomas, it is aberrantly expressed in all EML4-ALK positive samples. The mean intensities are displayed in the inserted bar graph for both EML4-ALK negative or positive patients, showing a significant difference in the expression levels of the two groups. Values are means ± SEM in the insert. p value was determined by student t test.