Figure 6. Combination of MTOR and CDK4/6 inhibition leads to durable disease control in PDX models:

(A) The indicated PDX models were randomized for treatment with vehicle, palbociclib, or palbociclib+TAK228 when tumor volume reached ~200 mm³. Tumors were treated and tumor volume was monitored every 48 hours. Data shows the mean and standard error of the mean. Greater than n=5 tumors mice were treated for each condition. For multiple PDX models the effect of combination was significant relative to palbociclib alone (*p<0.05, **p<0.01, ***p<0.001). (B) The 99 PDX model was treated with vehicle, palbociclib, or palbociclib+TAK228 for 21 days. Tumor volume was measured beyond the cessation of treatment (indicated by the dashed line). (C) Progression free survival (where progression represented a 50% increase in tumor volume) was determined for all tumors that were treated (control, n=99; palbociclib, n=113; palbociclib+TAK228, n=111). The combination of palbociclib and TAK228 resulted in improved progression free survival that was significant as determined by log-rank statistical analysis. (D) Gene expression analysis from independent PDX models treated with palbociclib or palbociclib and TAK228 showing transcript levels of CCND1, CCNE1 and CCNA2. The log-fold change is shown relative to vehicle control (**p<0.001). (E) The average fold change in Ki67 and average change in tumor volume is shown for palbociclib or palbociclib and TAK228. The same PDX model is connected by the line, demonstrating the per-model effect of the combination relative to single agent palbociclib. (F) Heatmaps show the relative log-fold change of the indicated genes with palbociclib alone vs. palbociclib+TAK228. (G) Heatmaps of relative levels of the indicated kinases recovered by MIB-mass spectrometry in vehicle control, palbociclib and palbociclib with TAK228 treated tumors from the 519 PDX model. (H) Schematic of the network between CDK4/6 inhibition, MTOR and the expression of cyclins associated with intrinsic resistance.