Based on our data pointing to critical involvement of mTOR signaling in TTLshort/high-risk leukemia, we addressed mTOR pathway activity by investigating phosphorylation of key signaling molecules: ribosomal protein S6 (S6), a downstream molecule which is phosphorylated by the ribosomal protein S6 kinase (p70S6K1) upon mTOR activation; and AKT, an upstream signaling kinase that is activated by phosphatidylinositol 3-kinase (PI3K) also mediating mTOR activation. Here, RPS6KB1 is linked to leukemia.