- Mika Shapiro1,
- Yair Herishanu2,*,
- Ben-Zion Katz2,
- Nili Dezorella2,
- Clare Sun3,
- Sigi Kay1,
- Aaron Polliack4,
- Irit Avivi5,
- Adrian Wiestner3 and
- Chava Perry1
- 1 Tel Aviv Sourasky Medical Center, Tel Aviv, Israel;
- 2 Tel-Aviv Sourasky Medical Center and Sackler Faculty of Medicine,Tel-Aviv University,Tel Aviv,Israel;
- 3 National Heart, Blood, Lung Inst, National Cancer Institute, National Inst. of Health, Bethesda, USA;
- 4 Hadassah University Hospital, Jerusalem, Israel;
- 5 Tel-Aviv Sourasky Medical Center and Sackler Faculty of Medicine,Tel-Aviv University,Tel-Aviv,Israel
- ↵* Corresponding author; email:
A novel therapeutic approach in cancer, attempting to stimulate host anti-tumor immunity, involves blocking of immune checkpoints. LAG3 is an immune checkpoint receptor expressed on activated/exhausted T-cells. When engaged by MHC class II molecules, LAG3 negatively regulates T-cell function thereby contributing to tumor escape. Intriguingly, a soluble LAG3 variant activates both immune and malignant MHC class II-presenting cells. In this study, we examined the role of LAG3 in the pathogenesis of chronic lymphocytic leukemia, an MHC class II-presenting malignancy, and show that chronic lymphocytic leukemia cells express and secrete LAG3. High levels of surface and soluble LAG3 were associated with the unmutated immunoglobulin variable heavy chain leukemic subtype and a shorter median time from diagnosis to first treatment. Utilizing a mechanism mediated through MHC class II engagement, recombinant soluble LAG3-Ig fusion protein, LAG3-Fc, activated chronic lymphocytic leukemia cells, induced anti-apoptotic pathways and protected the cells from spontaneous apoptosis, effects mediated by SYK, BTK and MAPK signaling. Moreover, LAG3 blocking antibody enhanced in vitro T cell activation. Our data suggest that soluble LAG3, promotes leukemia cell activation and anti-apoptotic effects, through its engagement with MHC class II. Furthermore, MHC class II-presenting chronic lymphocytic leukemia cells may affect LAG3-presenting T cells and impose immune exhaustion on their microenvironment hence; blocking LAG3-MHC class II interactions is a potential therapeutic target in chronic lymphocytic leukemia.
- Received May 8, 2016.
- Accepted January 25, 2017.
- Copyright © 2017, Ferrata Storti Foundation