A: Expression of the CHK2 mRNA is significantly decreased in A549 and H460 cells, but not in H69 and A2780 cells: Totally 20 μg RNA was used in each lane. The 18S and 28S rRNAs were used to normalize the loading of RNA sample in each lane. The probe was full-length CHK2 cDNA. B: Semi-quantitative RT-PCR analyses of the CHK2 mRNA expression in 11 non-small cell lung cancer cell lines. NHBE is a normal bronchial epithelial cell line. GAPDH was used to normalize the experimental conditions.