High-dimensional single-cell analysis unveils distinct immune signatures of peripheral blood in patients with pancreatic ductal adenocarcinoma

Abstract

IntroductionPancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies with poor response to immune checkpoint inhibitors. The mechanism of such poor response is not completely understood.MethodsWe assessed T-cell receptor (TCR) repertoire and RNA expression at the single-cell level using high-dimensional sequencing of peripheral blood immune cells isolated from PDAC patients and from healthy human controls. We validated RNA-sequencing data by performing mass cytometry (CyTOF) and by measuring serum levels of multiple immune checkpoint proteins.ResultsWe found that proportions of T cells (CD45+CD3+) were decreased in PDAC patients compared to healthy controls, while proportion of myeloid cells was increased. The proportion of cytotoxic CD8+ T cells and the level of cytotoxicity per cell were increased in PDAC patients, with reduced TCR clonal diversity. We also found a significantly enriched S100A9+ monocyte population and an increased level of TIM-3 expression in immune cells of peripheral blood in PDAC patients. In addition, the serum level of soluble TIM-3 (sTIM-3) was significantly higher in PDAC patients compared to the non-PDAC participants and correlated with worse survival in two independent PDAC cohorts. Moreover, sTIM-3 exhibited a valuable role in diagnosis of PDAC, with sensitivity and specificity of about 80% in the training and validation groups, respectively. We further established an integrated model by combining sTIM-3 and carbohydrate antigen 19- 9 (CA19-9), which had an area under the curve of 0.974 and 0.992 in training and validation cohorts, respectively.ConclusionOur RNA-seq and proteomic results provide valuable insight for understanding the immune cell composition of peripheral blood of patients with PDAC.

Exploring the potential of the TCR repertoire as a tumor biomarker (Review)

“…However, contrasting with the findings in HCC, Cui et al ( 28 ) reported that the diversity of the circulating TCR repertoire in patients with cervical cancer (CC) was lower than that in healthy women and gradually decreased during tumor development. Similarly, the TCR repertoire diversity in the peripheral blood of patients with pancreatic ductal adenocarcinoma (PDAC) was shown to decline compared with that in healthy controls in a study performed by Pan et al ( 29 ) involving analysis of the inverse Simpson diversity index. The authors speculated that the reduced TCR repertoire diversity may be caused by the proliferation of CD8 + T cells.…”