CLK1 and neoplasm: To further quantify the products, we performed quantitative real time RT-PCR using tumor samples from 168FARN and 4T1 for six candidate ASEs that displayed positive qualitative RT-PCR results: MED24 (alternative start from exon 20 in 4T1), CD44 (from 5′ to 3′ ends, first retained intron in 4T1), CD44 (intron inclusion between exons 9 and 10 in 4T1) and SRRT (intron inclusion between exons 5 and 6 and CLK1 - intron inclusion between exons 7 and 8 in 4T1).