Distribution of tumor-infiltrating-T-lymphocytes and possible tumor-escape mechanisms avoiding immune cell attack in locally advanced adenocarcinomas of the esophagus

Abstract

Introduction: The inflammatory microenvironment has emerged as one of the focuses of cancer research. Little is known about the immune environment in esophageal adenocarcinoma (EAC) and possible tumor-escape mechanisms to avoid immune cell attack.

Patients and methods: We measured T cell inflammation (CD3, CD8) in the microenvironment using a standardized software-based evaluation algorithm considering different predefined tumor areas as well as expression of MHC class 1 and PD-L1 on 75 analyzable primarily resected and locally advanced (≥ pT2) EACs. We correlated these findings statistically with clinical data.

Results: Patients with high amounts of T cell infiltration in their tumor center showed a significant survival benefit of 41.4 months compared to 16.3 months in T cell poor tumors (p = 0.025), although CD3 fails to serve as an independent prognostic marker in multivariate analysis. For the invasion zone, a correlation between number of T-cells and overall survival was not detectable. Loss of MHC1 protein expression on tumor cells was seen in 32% and PD-L1 expression using the combined positive score (CPS) in 21.2%. Most likely due to small numbers of cases, both markers are not prognostically relevant, even though PD-L1 expression correlates with advanced tumor stages.

Discussion: Our analyses reveal an outstanding, though not statistically independent, prognostic relevance of T-cell-rich inflammation in our group of EACs, in particular driven by the tumor center. For the first time, we describe that the inner part of the invasion zone in EACs shows significantly fewer T-cells than other tumor segments and is prognostically irrelevant. We also demonstrate that the loss of antigen presenting ability via MHC1 downregulation by the carcinoma cells is a common escape mechanism in EACs. Future work will need to show whether tumors with MHC class 1 loss respond less well to immunotherapy.

Keywords: Adenocarcinoma of the esophagus; Computer applications software; Inflammation; MHC1; PD-L1.

Fig. 1

Density of T-cells considering different tumor areas. Variation of the total number of T-cells (a), the cumulative area of (b) and the density of T-cells (c) in the in outer and inner infiltration margin and tumor center

Fig. 2

Overall-survival (Kaplan–Meier) depending on the T cell localization within the tumor. Compared overall survival of patients considering the T cell inflammation (high and low) at the outer invasive margin (a), inner invasive margin (b) and tumor center (c)

Fig. 3

Computer-based evaluation considering the tumor center and the invasion zone (divided into a 50 μm wide inner zone and a 300 μm wide outer zone) with regard to their T cell content (magnification × 200). a: Two different tumors with high density of CD3 positive T-cells (black dots) separated in tumor center (1), tumor inner invasive margin (arrow 2: area between red and blue line; 50 µm) and outer invasive margin (arrow 3: area between blue and yellow line; 300 µm). b Two different tumors with low density of CD3 positive T-cells (just very few black dots) separated in tumor center (1) and tumor invasive margin (arrow 2: area between red and blue line; 50 µm) and outer invasive margin (arrow 3: area between blue and yellow line; 300 µm)

Fig. 4

Immunohistochemical detection of PD-L1 and MHC1. A + B: PD-L1 strongly positive (a) and with low expression (b) using the Combined Positive Score (CPS 100) (magnification × 200). Black arrows show PD-L1 tumor cells positive (a) and negative (b). Orange arrows show PD-L1 positive inflammatory cells. C + D: MHC1 loss (c) and preserved expression (d) (magnification × 200). Black arrows show tumor cells with complete loss of MHC1 protein (c) and preserved nuclear staining (d). Orange arrows show internal positive control of MHC1 positive inflammatory cells