Figure 3. PI3K/mTOR pathway promotes survival in CD79B-mutant PCNSL.

A, Cartoon of the BCR/NFκB signaling axis. Genes harboring mutations in PCNSL are highlighted in red. B, Gene-set enrichment analysis (GSEA) of PCNSL biopsies shows enrichment of mTOR related gene sets in CD79B-mutated PCNSL. C, Activation of PI3K/mTOR in CD79B-mutant PCNSL. PCNSL tissue was stained with antibodies against 4EBP1 (T37/46) and S6 Ribosomal protein (S240/244). Tumors staining with both antibodies, labeled as “double positive”, were more common in CD79B-mutated PCNSL than in CD79B-wildtype PCNSL. (see bargraph on top ****: p<0.0001). The images below the bargraph show representative IHC images for a “double-positive” (left column) and “double-negative” (right column) PCNSL. D, BKM120, a pan-class I PI3K inhibitor, induces cell death in slice cultures from two CD79B-mutant PCNSL xenograft models. Shown are Western Blots of whole cell lysates after incubation for 24 hours with the indicated concentrations of BKM120. E, Combination of the PI3Kα-specific inhibitor BYL719 and the PI3Kδ-specific inhibitor Idelalisib, but neither inhibitor alone, induces cell death in a CD79B-mutant PCNSL cell line. F, The PI3Kα/δ specific inhibitor BAY 80-6946 induces cell death in PCNSL-MSK cells. G, Synergistic cell death induction by combination of ibrutnib and BAY 80-6946. H, Combination of ibrutnib and BAY 80-6946 is not associated with further NF-κB inhibition. n. oligo, oligonucleotides with the NF-κB binding domain are added and serve as a negative control for the assay. ***: p<0.001 I, Increased inhibition of the PI3K/mTOR pathway by combination of ibrutinib and BAY 80-6946; shown are Western Blots. J, Synergism between Ibrutinib and the dual mTOR inhibitor INK128 in PCNSL-MSK cells. ****: p<0.0001.