To demonstrate the on-target effect of a PI3K/mTOR inhibitor, the phosphorylation of PI3K/mTOR signaling proteins Akt (Ser473), mTOR (Ser2448), S6 (Ser240), and 4EBP1 (Thr37/46) was shown by western blot to decrease in TFE3-fusion RCC cell lines after treatment with 100nM NVP-BGT226 (Fig. 3A; Supplementary Figure S4A). Here, TFE3 is linked to renal cell carcinoma.