Figure 1. PDL1-dependent and PDL-independent resistance to RT and anti-CTLA4.

A) Res 499 relapsed 3 weeks after RT + anti-CTLA4. B) Representative contour plot of in vivo PDL1 expression on melanoma cells (blue) and CD45⁺ immune cells (red) from Res 499 tumors implanted into IFNG^KO mice, or C) mice treated with anti-CSF1R. Percentages for boxed populations are indicated. D) Survival of untreated mice with Res 499 or Res 499 PDL1^KO tumors (far left) or mice treated with RT + anti-CTLA4 with or without anti-CSF1R or anti-PD1 (n=5–15). E) JB2, which is from a Res 499 PDL1^KO tumor, relapsed two months after therapy. F) Tumor growth in mice treated with or without RT + anti-CTLA4 (n=5). *** p < 0.001 vs Res 499 RT + anti-CTLA4. G) Predicted survival of metastatic melanoma patients treated with RT + anti-CTLA4 modeled by random survival forest using the combined IHC PDL1 intensity score on melanoma cells and macrophages. Estimates are based on out-of-bag samples. Error rate is 38.7 +/− 0.01% with n=13. H) Overall survival after starting anti-PD1 for patients initially treated with RT + anti-CTLA4 on a clinical trial. Progression, time of progression, and death after anti-PD1 are indicated. I) Relative expression of IFN and IFN receptor genes from whole tumor lysates. Mean (grey line) and first and third quartiles (dashed lines) of all genes on the microarray are indicated. Error bars are standard deviations. J) IFNG levels in the blood of mice bearing Res 499 tumors after RT + anti-CTLA4 (n=7). * p < 0.05. Unless indicated, error bars are S.E.M. of biological replicates. See also Figure S1.