Alternative splicing of RAC1 in lung cancer. (A) The RAC1b isoform, which includes exon 3b, is preferentially up-regulated in all three lung tumors in our study. (B) Up-regulation of the RAC1b isoform is confirmed by exon array data from an independent data set (GSE16534). Each dot represents a tissue sample. To account for differences in the expression of total RAC1, we calculated the difference between the exon 3b expression and total RAC1 expression, and compared the differences between normal and tumor samples. The analysis showed that RAC1b is significantly up-regulated in tumors (P = 0.00026, Student's t-test). (C) Cell lines sensitive to PD-0325901 have significantly higher expression of the RAC1b isoform (P = 0.019, Student's t-test), while no difference in RAC1 total expression was observed between resistant and sensitive cell lines. Each dot represents one cell line. The boxes in the box-and-whisker plots represent the interquartile range between the first and third quartiles; the dashed lines (whiskers) extend to the most extreme data points which are no more than 1.5 times the interquartile range from the box.
