Supplementary figure 1: A +B. Hierarchical clustering of microdissected stromal and epithelial (A) and FACS sorted endothelial, fibroblast, epithelial and leukocyte (B) cell populations using previously published non-epithelial derived gene list confirms purity of cell populations. C and D. PCA plot of data presented in top panels highlights clear stratification of samples based on cell lineage using this gene signature. E. Expression values for IFNG expression according to cell-of-origin confirms immune-derived nature of signal. Supplementary figure 2: Association of high PD-L1 expression with MSI subtype and high immune infiltrate. Supplementary figure 3: A. Dot and boxplots of PD-L1 mean gene expression values stratified by MSI status highlights significant association between PD-L1 transcription levels and MSI genotype. B. (Left) Hierarchical clustering of stage II/III CRC cohort based on expression profiles of CD274, CTLA4, LAG3 and IDO1. (Right) Significant upregulation of CD274, IDO1, CTLA4 and LAG3 genes in the PD-L1high subgroup. C. (Left) Dot plot and boxplot of IFNG expression levels stratified by PD-L1-subgroup. (Right) Significant upregulation of IFNG gene in the PD-L1high subgroup.
ARTICLE ABSTRACT
A recent phase II study of patients with metastatic colorectal carcinoma showed that mismatch repair gene status was predictive of clinical response to PD-1–targeting immune checkpoint blockade. Further examination revealed strong correlation between PD-L1 protein expression and microsatellite instability (MSI) in stage IV colorectal carcinoma, suggesting that the amount of PD-L1 protein expression could identify late-stage patients who might benefit from immunotherapy. To assess whether the clinical associations between PD-L1 gene expression and MSI identified in metastatic colorectal carcinoma are also present in stage II/III colorectal carcinoma, we used in silico analysis to elucidate the cell types expressing the PD-L1 gene. We found a statistically significant association of PD-L1 gene expression with MSI in early-stage colorectal carcinoma (P < 0.001) and show that, unlike in non–colorectal carcinoma tumors, PD-L1 is derived predominantly from the immune infiltrate. We demonstrate that PD-L1 gene expression has positive prognostic value in the adjuvant disease setting (PD-L1low vs. PD-L1high HR = 9.09; CI, 2.11–39.10). PD-L1 gene expression had predictive value, as patients with high PD-L1 expression appear to be harmed by standard-of-care treatment (HR = 4.95; CI, 1.10–22.35). Building on the promising results from the metastatic colorectal carcinoma PD-1–targeting trial, we provide compelling evidence that patients with PD-L1high/MSI/immunehigh stage II/III colorectal carcinoma should not receive standard chemotherapy. This conclusion supports the rationale to clinically evaluate this patient subgroup for PD-1 blockade treatment. Cancer Immunol Res; 4(7); 582–91. ©2016 AACR.
