Tnfrsf4-expressing regulatory T cells promote immune escape of chronic myeloid leukemia stem cells
Magdalena Hinterbrandner, Viviana Rubino, Carina Stoll, Stefan Forster, Noah Schnüriger, Ramin Radpour, Gabriela M. Baerlocher, Adrian F. Ochsenbein, Carsten Riether
Magdalena Hinterbrandner, Viviana Rubino, Carina Stoll, Stefan Forster, Noah Schnüriger, Ramin Radpour, Gabriela M. Baerlocher, Adrian F. Ochsenbein, Carsten Riether
View: Text | PDF
Research Article Hematology Stem cells

Tnfrsf4-expressing regulatory T cells promote immune escape of chronic myeloid leukemia stem cells

Abstract

Leukemia stem cells (LSCs) promote the disease and seem resistant to therapy and immune control. Why LSCs are selectively resistant against elimination by CD8+ cytotoxic T cells (CTLs) is still unknown. In this study, we demonstrate that LSCs in chronic myeloid leukemia (CML) can be recognized and killed by CD8+ CTLs in vitro. However, Tregs, which preferentially localized close to CD8+ CTLs in CML BM, protected LSCs from MHC class I–dependent CD8+ CTL–mediated elimination in vivo. BM Tregs in CML were characterized by the selective expression of tumor necrosis factor receptor 4 (Tnfrsf4). Stimulation of Tnfrsf4 signaling did not deplete Tregs but reduced the capacity of Tregs to protect LSCs from CD8+ CTL–mediated killing. In the BM of newly diagnosed CML patients, TNFRSF4 mRNA levels were significantly increased and correlated with the expression of the Treg-restricted transcription factor FOXP3. Overall, these results identify Tregs as key regulators of immune escape of LSCs and TNFRSF4 as a potential target to reduce the function of Tregs and boost antileukemic immunity in CML.

Authors

Magdalena Hinterbrandner, Viviana Rubino, Carina Stoll, Stefan Forster, Noah Schnüriger, Ramin Radpour, Gabriela M. Baerlocher, Adrian F. Ochsenbein, Carsten Riether

×

Figure 5

BM Tregs in CML protect LSCs from CD8+ T cell–mediated eradication in vivo.

Options: View larger image (or click on image) Download as PowerPoint
BM Tregs in CML protect LSCs from CD8+ T cell–mediated eradication in vi...
(A) Experimental setup. BCR-ABL1-GFP–transduced LSKs were injected i.v. into nonirradiated Foxp3DTR recipients. At day 13, mice were randomized to PBS/DT and αCD8 mAb treatment (DT i.p. at days 13, 14, 19, and 20; αCD8 mAb at days 13 and 15 i.p.). (B–E) Spleen weight, absolute numbers of L-lin– cells, L–c-kithi cells, and LSCs in the BM of CML mice of all treatment groups 21 days after CML induction; 1-way ANOVAs followed by Tukey’s multiple comparison test. PBS, n = 3 mice; PBS + αCD8, n = 4 mice; DT, n = 5 mice; and DT + αCD8, n = 5 mice. (F) BM cells of primary CML mice (day 21) were injected i.v. into lethally irradiated secondary BL/6 recipients, and survival was monitored; log-rank test. PBS, n = 3 mice; PBS + αCD8, n = 4 mice; DT, n = 5 mice; and DT + αCD8, n = 5 mice. (G) LSCs were preincubated with CD8+ CTLs from naive or CML-bearing mice treated with PBS or DT overnight in a 1:1 ratio, followed by plating in methylcellulose. Myeloid CFU and replating capacity in vitro (n = 3 mice/group); 1-way ANOVA followed by Tukey’s post hoc test. (H–J) Perforin (Prf1), Granzyme A (GrzmA), and Granzyme B (GrzmB) mRNA expression levels in BM CD8+ CTLs measured by qPCR. Data are normalized to Gapdh (naive, n = 4 mice; CML, n = 5 mice; CML DT, n = 4 mice); 1-way ANOVA followed by Tukey’s post hoc test. Data are displayed as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001. Dotted line represents the time point experiment termination day 90.