Poster lunch (ID 46) Poster display session

144P - Immune cell dynamics induced by a single dose of pembrolizumab as revealed by single-cell RNA profiling (ID 585)

Presentation Number
144P
Lecture Time
12:15 - 12:15
Speakers
  • Hanne Vos (Leuven, Belgium)
Session Name
Poster lunch (ID 46)
Location
Exhibition area, MARITIM Hotel Berlin, Berlin, Germany
Date
03.05.2019
Time
12:15 - 13:00

Abstract

Background

To improve our understanding of the molecular mechanisms underlying response to immune checkpoint inhibition, we monitored dynamic changes within the tumour microenvironment exposed to immune checkpoint inhibition by single-cell RNA sequencing (scRNA-seq).

Methods

In a window-of-opportunity setting, fresh tumor tissue was collected from breast cancer patients before and 10 days after a single dose of 200 mg Pembrolizumab monotherapy. Hematoxylin-eosin (H&E) staining to determine tumor infiltrating lymphocytes (TILs) and scRNA-seq was performed on fixed and fresh tumor tissue, respectively. Single cell suspensions were subjected to 10X Genomics scRNA- and T-cell receptor-sequencing using the Chromium Single Cell 5’ kit on an Illumina NovaSeq. Expression matrices were generated using CellRanger and analyzed by Seurat. Dimensionality reduction was applied by PCA.

Results

Currently, 7 paired tumor samples have been analyzed. All were ER/PR-negative IDA, of which 3 were pre-treated with neo-adjuvant chemotherapy. On H&E slide, there were no notable differences in TILs comparing biopsies before versus after Pembro. By scRNA-seq, we did observe several prominent changes. First, there was a decrease in cancer cells versus an increase in immune cells after Pembro. Second, the increase in T-cells was due to an increased prevalence of exhausted CD4+ and CD8+ cytotoxic cells, as well as regulatory T-cells, which were all positive for PD1 expression. Cytolytic activity in these T-cell subpopulations also increased significantly, and this was accompanied by a specific increase in TCR clonotypes in these. Finally, in 3 out of 7 pairs such changes in T-cells were not detectable. In these post-treatment samples, a decrease in expression of MHC class 1 genes was observed specifically in cancer cells.

Conclusions

Our data suggest that scRNA-seq creates accurate maps of the tumor micro-environment and is capable of monitoring dynamic changes already induced by a single dose of immunotherapy. Particularly, in 4/7 patients changes in T-cells reactivity reminiscent of a clinical response to Pembrolizumab were noted. Other patients failed to display such reactivity presumably due to a failure in presenting neo-epitopes by MHC class 1 genes.

Clinical trial identification

NCT03197389.

Legal entity responsible for the study

University Hospitals Leuven.

Funding

Investigator initiated study MSD Kom op Tegen Kanker Fonds Nadine de Beauffort VIB VIB Grand Challenge.

Disclosure

All authors have declared no conflicts of interest.

Collapse