We further delved into the nucleotide contexts surrounding the 3′-splice site and found that mTOR activation promotes the skipping of the cassette exon that contains a strong, longer stretch of the poly-pyrimidine tract (−3 to −20 position) and a weak poly-pyrimidine tract with biased C at the −1 position in the alternative 3′-splice site in both Tsc1-/- MEFs and human cancer cells (Figure 1C). The gene discussed is TSC1; the disease is cancer.