Wyss, Jacqueline; Dislich, Bastian; Kölzer, Viktor; Galván, José A.; Dawson, Heather; Hädrich, Marion; Inderbitzin, Daniel; Lugli, Alessandro; Zlobec, Inti; Berger, Martin D. (2019). Stromal PD-1/PD-L1 Expression Predicts Outcome in Colon Cancer Patients. Clinical colorectal cancer, 18(1), e20-e38. Elsevier 10.1016/j.clcc.2018.09.007
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INTRODUCTION
The programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) axis plays an important role in controlling immune suppression by down-regulating T effector cell activities, enabling tumor cells to escape from the host's antitumor immunsurveillance. While only a small part of colon cancer cells express PD-L1, we sought to evaluate the differential impact of stromal and epithelial PD-L1 expression of primary tumors and liver metastasis on overall survival (OS) in colon cancer patients.
PATIENTS AND METHODS
Using a next-generation tissue microarray approach, we assessed both epithelial and stromal PD-L1 expression levels in primary tumors (n = 279) and corresponding liver metastases (n = 14) of colon cancer patients. PD-L1 positivity was graded according to the percentage (0.1%-1%, > 1%, > 5%, > 50%) of tumor cells with membranous PD-L1 expression or as the percentage of positive stroma cells and associated inflammatory infiltrates. We also assessed the interplay between stromal PD-1/PD-L1 and both intratumoral and stromal CD8 count and their impact on outcome. The primary end point was OS.
RESULTS
Stromal PD-L1 and PD-1 expression were both associated with less aggressive tumor behavior in colon cancer patients, which translated into better OS and disease-free survival, respectively. Conversely, PD-L1 staining in the tumor cells was less frequent than stromal staining and was associated with features of aggressive tumor biology, although without impact on outcome. Interestingly, the PD-L1 staining pattern remained similar between primary tumors and corresponding liver metastases. Stromal PD-1 expression correlated significantly with stromal PD-L1 staining and both intratumoral and stromal CD8 expression.
CONCLUSION
Stromal PD-1/PD-L1 expression might serve as a prognostic marker in colon cancer patients.