FLT3L-induced virtual memory CD8 T cells engage the immune system against tumors

Hsin-Fang Tu; Yu-Jui Kung; Ling Lim; Julia Tao; Ming-Hung Hu; Michelle Cheng; Deyin Xing; T C Wu; Chien-Fu Hung

doi:10.1186/s12929-024-01006-9

FLT3L-induced virtual memory CD8 T cells engage the immune system against tumors

J Biomed Sci. 2024 Jan 29;31(1):19. doi: 10.1186/s12929-024-01006-9.

Authors

Hsin-Fang Tu¹, Yu-Jui Kung², Ling Lim¹, Julia Tao³, Ming-Hung Hu¹, Michelle Cheng¹, Deyin Xing¹, T C Wu^{1

4

5

6}, Chien-Fu Hung^{7

8}

Affiliations

¹ Department of Pathology, Johns Hopkins University School of Medicine, 1550 Orleans Street, CRB II 307, Baltimore, MD, 21287, USA.
² Johns Hopkins University School of Medicine, Baltimore, MD, USA.
³ Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
⁴ Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
⁵ Department of Obstetrics and Gynecology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
⁶ Molecular Microbiology and Immunology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
⁷ Department of Pathology, Johns Hopkins University School of Medicine, 1550 Orleans Street, CRB II 307, Baltimore, MD, 21287, USA. chung2@jhmi.edu.
⁸ Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. chung2@jhmi.edu.

Abstract

Background: Previous research in FMS-like tyrosine kinase 3 ligands (FLT3L) has primarily focused on their potential to generate dendritic cells (DCs) from bone marrow progenitors, with a limited understanding of how these cells affect CD8 T cell function. In this study, we further investigated the in vivo role of FLT3L for the immunomodulatory capabilities of CD8 T cells.

Methods: Albumin-conjugated FLT3L (Alb-FLT3L) was generated and applied for translational medicine purposes; here it was used to treat naïve C57BL/6 and OT1 mice for CD8 T cell response analysis. Syngeneic B16ova and E.G7ova mouse models were employed for adoptive cell transfer to evaluate the effects of Alb-FLT3L preconditioning of CD8 T cells on tumor progression. To uncover the underlying mechanisms of Alb-FLT3L modulation, we conducted bulk RNA-seq analysis of the CD44^high CD8 T cells. STAT1-deficient mice were used to elucidate the functional roles of Alb-FLT3L in the modulation of T cells. Finally, antibody blockade of type one interferon signaling and in vitro coculture of plasmacytoid DCs (pDCs) with naive CD8 T cells was performed to determine the role of pDCs in mediating regulation of CD44^high CD8 T cells.

Results: CD44^high CD8 T cells were enhanced in C57BL/6 mice administrated with Alb-FLT3L. These CD8 T cells exhibited virtual memory features and had greater proliferative and effective functions. Notably, the adoptive transfer of CD44^high naïve CD8 T cells into C57BL/6 mice with B16ova tumors led to significant tumor regression. RNA-seq analysis of the CD44^high naïve CD8 T cells revealed FLT3L to induce CD44^high CD8 T cells in a JAK-STAT1 signaling pathway-dependent manner, as supported by results indicating a decreased ability of FLT3L to enhance CD8 T cell proliferation in STAT1-deficient mice as compared to wild-type control mice. Moreover, antibody blockade of type one interferon signaling restricted the generation of FLT3L-induced CD44^high CD8 T cells, while CD44 expression was able to be induced in naïve CD8 T cells cocultured with pDCs derived from FLT3L-treated mice. This suggests the crucial role of pDCs in mediating FLT3L regulation of CD44^high CD8 T cells.

Conclusions: These findings provide critical insight and support the therapeutic potential of Alb-FLT3L as an immune modulator in preconditioning of naïve CD8 T cells for cancer immunotherapy.

Keywords: Alb-FLT3L; CD44high CD8 T cells; Virtual memory CD8 T cells.

MeSH terms

Animals
CD8-Positive T-Lymphocytes*
Dendritic Cells
Interferons
Mice
Mice, Inbred C57BL
Neoplasms* / metabolism

Substances

Interferons
flt3 ligand protein

Abstract

MeSH terms

Substances

Grants and funding