Treatment with MTIs results in hypophosphorylated S6 in ALL. Splenocytes were harvested from mice treated with CCI-779 or control (vehicle). Immunoblot of phospho-S6 (ser235/236) of control and CCI-779 treated (top bands), total S6 (middle bands), and β-tubulin (bottom band; loading control) from 4 patient samples is depicted. We found a correlation between clinical response and biochemical response to CCI-779 in all samples. ALL cells from CCI-779-treated mice had 48% to more than 95% down-regulation of phospho-S6 compared to blasts from control mice.