Checkpoint Expression Pre And Post Chemoradiation In Operable Esophageal Cancer.

139Background: PD-L1 expression has been reported in 40% of gastroesophageal cancers, but little data exists with regards to expression of other immune checkpoints. Here, we examined baseline expression levels for multiple immune modulators in 31 resected esophageal adenocarcinomas (EAC) and investigated the change in expression levels post-chemoradiation. Methods: Slides were stained on a Ventana BenchMark ULTRA automated stainer for CTLA-4 (Santa Cruz Clone F-8, dilutions 1:100) and PD-L1 (Dako clone 22C3 prediluted). Tonsil tissue was used as a control for lymphocytes, and a provided tumor control was used for PD-L1. Positivity was classified as u003e 1%, and the stained cell type was recorded (lymphocytes or tumor). Additionally, laser capture microdissection was performed, and RNA was isolated and pre-amplified to determine expression levels of TIM-3, GITR, IDO-1, LAG-3, CD-137, OX-40, and KIR-3 using RT-PCR. Gene expression was calculated using the ΔΔ -Ct method, and intergroup comparisons were performe...