Anti-leukemia activity of human gamma delta T cells

Increased PD-1+Foxp3+ γδ T cells associate with poor overall survival for patients with acute myeloid leukemia

Problems

γδ T cells are essential for anti-leukemia function in immunotherapy, however, γδ T cells have different functional subsets, including regulatory cell subsets expressing the Foxp3. Whether they are correlated with immune-checkpoint mediated T cell immune dysfunction remains unknown in patients with acute myeloid leukemia (AML).

Methods

In this study, we used RNA-seq data from 167 patients in TCGA dataset to analyze the correlation between PD-1 and FOXP3 genes and these two genes' association with the prognosis of AML patients. The expression proportion of Foxp3⁺/PD-1⁺ cells in γδ T cells and two subgroups Vδ1 and Vδ2 T cells were performed by flow cytometry. The expression level of FOXP3 and PD-1 genes in γδ T cells were sorted from peripheral blood by MACS magnetic cell sorting technique were analyzed by quantitative real-time PCR.

Results

We found that PD-1 gene was positively correlated with FOXP3 gene and highly co-expressed PD-1 and FOXP3 genes were associated with poor overall survival (OS) from TCGA database. Then, we detected a skewed distribution of γδ T cells with increased Vδ1 and decreased Vδ2 T cell subsets in AML. Moreover, significantly higher percentages of PD-1⁺ γδ, Foxp3⁺ γδ, and PD-1⁺Foxp3⁺ γδ T cells were detected in de novo AML patients compared with healthy individuals. More importantly, AML patients containing higher PD-1⁺Foxp3⁺ γδ T cells had lower OS, which might be a potential therapeutic target for leukemia immunotherapy.

Conclusion

A significant increase in the PD-1⁺Foxp3⁺ γδ T cell subset in AML was associated with poor clinical outcome, which provides predictive value for the study of AML patients.

Translating Unconventional T Cells and Their Roles in Leukemia Antitumor Immunity

Recently, cell-mediated immune response in malignant neoplasms has become the focus in immunotherapy against cancer. However, in leukemia, most studies on the cytotoxic potential of T cells have concentrated only on T cells that recognize peptide antigens (Ag) presented by polymorphic molecules of the major histocompatibility complex (MHC). This ignores the great potential of unconventional T cell populations, which include gamma-delta T cells (γδ), natural killer T cells (NKT), and mucosal-associated invariant T cells (MAIT). Collectively, these T cell populations can recognize lipid antigens, specially modified peptides and small molecule metabolites, in addition to having several other advantages, which can provide more effective applications in cancer immunotherapy. In recent years, these cell populations have been associated with a repertoire of anti- or protumor responses and play important roles in the dynamics of solid tumors and hematological malignancies, thus, encouraging the development of new investigations in the area. This review focuses on the current knowledge regarding the role of unconventional T cell populations in the antitumor immune response in leukemia and discusses why further studies on the immunotherapeutic potential of these cells are needed.

γδ T cells and epigenetic drugs: A useful merger in cancer immunotherapy?

γδ T cell-based immunotherapeutic strategies in cancer patients are as yet of limited success. Drugs targeting epigenetic mechanisms including histone acetylation and DNA methylation trigger cell death in tumor cells but in addition have immunomodulatory activity. Here, we discuss the potential benefit of combining both strategies in cancer immunotherapy.

Human Vδ2 versus non-Vδ2 γδ T cells in antitumor immunity

The Vδ2 and non-Vδ2 (mainly Vδ1) subsets of human γδ T cells have distinct homing patterns and recognize different types of ligands, yet both exert potent antitumor effects. While the T-cell receptor of Vδ2 T cells primarily recognizes tumor cell-derived pyrophosphates, non-Vδ2 γδ T cells preferentially recognize stress-associated surface antigens. Here, we discuss the pros and cons of Vδ2 versus non-Vδ2 γδ T cells as tools for future immunotherapeutic interventions against cancer.

Trial Watch: Adoptive cell transfer for anticancer immunotherapy

Adoptive cell transfer (ACT) represents a prominent form of immunotherapy against malignant diseases. ACT is conceptually distinct from dendritic cell-based approaches (which de facto constitute cellular vaccines) and allogeneic transplantation (which can be employed for the therapy of hematopoietic tumors) as it involves the isolation of autologous lymphocytes exhibiting antitumor activity, their expansion/activation ex vivo and their reintroduction into the patient. Re-infusion is most often performed in the context of lymphodepleting regimens (to minimize immunosuppression by host cells) and combined with immunostimulatory interventions, such as the administration of Toll-like receptor agonists. Autologous cells that are suitable for ACT protocols can be isolated from tumor-infiltrating lymphocytes or generated by engineering their circulating counterparts for the expression of transgenic tumor-specific T-cell receptors. Importantly, lymphocytes can be genetically modified prior to re-infusion for increasing their persistence in vivo, boosting antitumor responses and minimizing side effects. Moreover, recent data indicate that exhausted antitumor T lymphocytes may be rejuvenated in vitro by exposing them to specific cytokine cocktails, a strategy that might considerably improve the clinical success of ACT. Following up the Trial Watch that we published on this topic in the third issue of OncoImmunology (May 2012), here we summarize the latest developments in ACT-related research, covering both high-impact studies that have been published during the last 13 months and clinical trials that have been initiated in the same period to assess the antineoplastic profile of this form of cellular immunotherapy.