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Published on: November 28, 2015
TNBC-derived Gal3BP/Gal3 complex induces immunosuppression through CD45 receptor
Annat Raiter1, Julia Lipovetsky2, Asaf Stenbac1
1Felsenstein Medical Research Center, Tel Aviv University, Faculty of Medicine, Petach Tikva, Israel.
Abstract:
A preliminary study investigating immunotherapy strategies for aggressive triple negative breast cancer (TNBC) revealed an overexpression of genes involved in the release of extracellular vesicles (EVs). Proteins expressed by EVs play a role in reprogramming the tumor microenvironment and impeding effective responses to immunotherapy. Galectin 3 (Gal3), found in the extracellular space of breast cancer cells, downregulates T-cell receptor expression. Gal3 binds to several receptors, including CD45, which is required for T-cell receptor activation. Previously, we reported a novel tumor escape mechanism, whereby TNBC cells suppress immune cells through CD45 intracellular signals. The objective of this study was to determine the potential association of Gal3 with TNBC-secreted EVs induction of immunosuppression via the CD45 signaling pathway. EVs were isolated from MDA-MB-231 cells and the plasma of patients with TNBC. Mass spectrometry revealed the presence of Gal3 binding protein (Gal3BP) in the isolated small EVs, which interacted with TNBC secreted Gal3. Gal3BP and Gal3 form a complex that induces a significant increase in T-regulatory cells in peripheral blood mononuclear cells (PBMCs). This increase correlates with a significant increase in suppressive interleukins 10 and 35. Blocking the CD45 receptor in PBMCs cultured with tumor-derived EVs impeded the immunosuppression exerted by the Gal3BP/Gal3 complex. This led to an increase in IFN-γ and the activation of CD4, CD8 and CD56 effector cells. This study suggests a tumor escape mechanism that may contribute to the development of a different immunotherapy strategy that complements current therapies used for TNBC.
Insights
Triple negative breast cancer (TNBC) uses extracellular vesicles (EVs) with Galectin 3 (Gal3) to suppress immune cells. Blocking the CD45 pathway with EVs and Gal3BP reversed this immunosuppression, offering new immunotherapy targets.
Area of Science:
- Oncology
- Immunology
- Cell Biology
Background:
- Triple negative breast cancer (TNBC) is aggressive and often resistant to immunotherapy.
- Extracellular vesicles (EVs) secreted by TNBC cells can reprogram the tumor microenvironment and hinder immune responses.
- Galectin 3 (Gal3), found in breast cancer cells, downregulates T-cell receptor expression by binding to receptors like CD45.
Purpose of the Study:
- To investigate the association between Gal3, TNBC-secreted EVs, and immunosuppression via the CD45 signaling pathway.
- To elucidate a novel tumor escape mechanism in TNBC.
Main Methods:
- Isolation of EVs from TNBC cell lines (MDA-MB-231) and patient plasma.
- Mass spectrometry to identify proteins within EVs.
- Co-culture of peripheral blood mononuclear cells (PBMCs) with tumor-derived EVs and Gal3BP/Gal3 complex.
- Blocking the CD45 receptor in co-cultured PBMCs.
Main Results:
- TNBC-secreted EVs contain Gal3 binding protein (Gal3BP) that interacts with Gal3.
- The Gal3BP/Gal3 complex significantly increases T-regulatory cells and suppressive interleukins (IL-10, IL-35) in PBMCs.
- Blocking CD45 on PBMCs reversed EV-mediated immunosuppression, increasing IFN-γ and activating CD4, CD8, and CD56 effector cells.
Conclusions:
- TNBC utilizes a Gal3BP/Gal3 complex within EVs to induce immunosuppression through the CD45 pathway.
- This mechanism represents a novel tumor escape strategy for TNBC.
- Targeting this pathway could lead to new immunotherapy strategies for TNBC.
