Combining T-cell-based immunotherapy with venetoclax elicits synergistic cytotoxicity to B-cell lines in vitro

Combination of BCL-2 inhibitors and immunotherapy: a promising therapeutic strategy for hematological malignancies

The rapid development of high-throughput sequencing in recent years has facilitated great progress in the molecular-targeted therapy of hematological malignancies, including leukemia, lymphoma, and multiple myeloma. BCL-2 inhibitors are among the most important molecular-targeted agents. Immunotherapy for hematologic malignancy has rapidly increased in popularity in recent years and has been proven to improve the overall survival rate. However, few clinical studies have investigated combination therapy with BCL-2 inhibitors and immunotherapies, such as immune molecule-targeted drugs or immune cell adoptive therapy. In this review, we discuss the drug discovery process, current clinical application status, and resistance and tolerance issues associated with BCL-2 inhibitors. We emphasize their important role in regulating the immune system and propose that the combination of BCL-2 inhibitors with immunotherapy may be one of the most promising treatment methods for hematologic malignancies.

Harnessing the immune system in the treatment of cutaneous T cell lymphomas

Cutaneous T cell lymphomas are a rare subset of non-Hodgkin's lymphomas with predilection for the skin with immunosuppressive effects that drive morbidity and mortality. We are now appreciating that suppression of the immune system is an important step in the progression of disease. It should come as no surprise that therapies historically and currently being used to treat these cancers have immune modulating functions that impact disease outcomes. By understanding the immune effects of our therapies, we may better develop new agents that target the immune system and improve combinatorial treatment strategies to limit morbidity and mortality of these cancers. The immune modulating effect of therapeutic drugs in use and under development for cutaneous T cell lymphomas will be reviewed.

The BCL-2 Inhibitor Venetoclax Augments Immune Effector Function Mediated by Fas Ligand, TRAIL, and Perforin/Granzyme B, Resulting in Reduced Plasma Viremia and Decreased HIV Reservoir Size during Acute HIV Infection in a Humanized Mouse Model

The BCL-2 prosurvival protein is implicated in HIV persistence and is a potential therapeutic target for HIV eradication efforts. We now know that cells harboring HIV are preferentially enriched for high BCL-2 expression, enabling their survival, and that the BCL-2 inhibitor venetoclax promotes the death of actively replicating HIV-infected cells in vitro and ex vivo. Herein, we assess the effect of venetoclax on immune clearance of infected cells and show that BCL-2 inhibition significantly enhances target cell killing induced by Fas ligand, TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), and perforin/granzyme B and synergistically enhances autologous NK (natural killer) and CD8 cells' killing of target cells. In a humanized mouse model of acute HIV infection, venetoclax monotherapy significantly decreases plasma viremia and normalizes CD4:CD8 ratios, and results in more mice with undetectable provirus levels than control. In this model, treatment was associated with leukopenia, as has been described clinically in patients receiving venetoclax for other indications. These data confirm meaningful anti-HIV effects of venetoclax during HIV infection but suggest that venetoclax use should be combined with ART (antiretroviral therapy) to reduce toxicity. IMPORTANCE This study is the first to examine the applicability of BCL-2 inhibition in the setting of active HIV infection in vivo. Furthermore, this study demonstrates that venetoclax significantly enhances target cell killing induced by Fas ligand, TRAIL, and perforin/granzyme B and synergistically enhances autologous NK and CD8 cells' killing of target cells.

Prime, shock and kill: BCL-2 inhibition for HIV cure

While modern HIV therapy can effectively suppress viral replication, the persistence of the latent reservoir posits the greatest hurdle to complete cure. The "shock and kill" strategy is under investigation for HIV therapy, aiming to reactivate latent HIV, and subsequently eliminate it through anti-retroviral therapy and host immune function. However, thus far, studies have yielded suboptimal results, stemming from a combination of ineffective latency reversal and poor immune clearance. Concomitantly, studies have now revealed the importance of the BCL-2 anti-apoptotic protein as a critical mediator of infected cell survival, reservoir maintenance and immune evasion in HIV. Furthermore, BCL-2 inhibitors are now recognized for their anti-HIV effects in pre-clinical studies. This minireview aims to examine the intersection of BCL-2 inhibition and current shock and kill efforts, hoping to inform future studies which may ultimately yield a cure for HIV.

Strategies to overcome CAR-T cell resistance in clinical work: A single-institute experience

The emergence of chimeric antigen receptor (CAR) T cell therapy has shifted the paradigm of malignant tumor treatment, especially the advent of CD19-directed CAR-T cell therapy for the treatment of relapsed/refractory (R/R) B-cell malignancies. Although CAR-T cell therapy has promising effects, some patients are resistant to this treatment, leaving them with limited options. Therefore, strategies to overcome resistance to CAR-T cell therapy are needed. We retrospectively studied three R/R diffuse large B-cell lymphoma patients who were resistant to CAR-T cell therapy and whose disease was controlled after receiving pembrolizumab, 21D4 CAR-T cells, or ibrutinib and venetoclax. Some promising prevention and treatment strategies to overcome treatment resistance are also discussed.

Conventional Therapeutics in BPDCN Patients-Do They Still Have a Place in the Era of Targeted Therapies?

No benchmark treatment exists for blastic plasmacytoid dendritic cell neoplasm (BPDCN). Since the malignancy is chemo-sensitive, chemotherapy followed by hematopoietic stem cell transplantation remains an effective treatment. However, relapses frequently occur with the development of resistance. New options arising with the development of therapies targeting signaling pathways and epigenetic dysregulation have shown promising results. In this review, we focus on conventional therapies used to treat BPDCN and the novel therapeutic approaches that guide us toward the future management of BPDCN.

Venetoclax enhances NK cell killing sensitivity of AML cells through the NKG2D/NKG2DL activation pathway

BACKGROUND

Venetoclax, a selective B-cell lymphoma-2 (BCL2) inhibitor, has a potential therapeutic effect when combined with demethylating agents in the first-line setting of unfit elderly patients with acute myeloid leukaemia (AML); however, efficacy is still limited in refractory/recurrent AML. Therefore, exploration of a suitable novel treatment scheme is urgently needed.However, combining venetoclax with NK cell-based immunotherapy has not been studied.

METHODS

The cytotoxicity of NK cell combined with venetoclax was assessed in vitro using flow cytometry. Venetoclax-induced natural killer group 2 member D (NKG2D) ligand (NKG2DL) expression was detected by flow cytometry and western blotting. Mechanisms underlying venetoclax-induced NKG2DL expression were found by GSE127200 analysis and investigated using real-time PCR (Q-PCR) and western blotting.

RESULTS

Flow cytometric analysis showed that combining venetoclax with NK cells produced synergistic anti-leukaemia effects similar to those of venetoclax + azacitidine. Venetoclax could render AML cell lines and primary AML cells sensitive to NK cell killing by promoting NK cell degranulation, NK-AML cell recognition and NK cell secretion of interferon (IFN)-γ and granzyme B. The synergistic effect resulted from venetoclax-induced NKG2DL upregulation in AML cells and could be undermined by blocking NKG2D on NK cells. This finding suggests that venetoclax enhances NK cell killing activity by activating the NKG2D/NKG2DL ligand-receptor pathway. Furthermore, the nuclear factor-kappa-B (NFKB) signalling pathway was involved in venetoclax-induced NKG2DL upregulation.

CONCLUSIONS

Collectively, our data confirm that venetoclax combined with NK cells induces synergistic AML cell cytolysis and preliminarily revealed that venetoclax could selectively induce NKG2DLs on AML cells via NFKB signalling pathway.

Immune Dysfunctions and Immune-Based Therapeutic Interventions in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by a wide range of tumor-induced alterations, which affect both the innate and adaptive arms of the immune response, and accumulate during disease progression. In recent years, the development of targeted therapies, such as the B-cell receptor signaling inhibitors and the Bcl-2 protein inhibitor venetoclax, has dramatically changed the treatment landscape of CLL. Despite their remarkable anti-tumor activity, targeted agents have some limitations, which include the development of drug resistance mechanisms and the inferior efficacy observed in high-risk patients. Therefore, additional treatments are necessary to obtain deeper responses and overcome drug resistance. Allogeneic hematopoietic stem cell transplantation (HSCT), which exploits immune-mediated graft-versus-leukemia effect to eradicate tumor cells, currently represents the only potentially curative therapeutic option for CLL patients. However, due to its potential toxicities, HSCT can be offered only to a restricted number of younger and fit patients. The growing understanding of the complex interplay between tumor cells and the immune system, which is responsible for immune escape mechanisms and tumor progression, has paved the way for the development of novel immune-based strategies. Despite promising preclinical observations, results from pilot clinical studies exploring the safety and efficacy of novel immune-based therapies have been sometimes suboptimal in terms of long-term tumor control. Therefore, further advances to improve their efficacy are needed. In this context, possible approaches include an earlier timing of immunotherapy within the treatment sequencing, as well as the possibility to improve the efficacy of immunotherapeutic agents by administering them in combination with other anti-tumor drugs. In this review, we will provide a comprehensive overview of main immune defects affecting patients with CLL, also describing the complex networks leading to immune evasion and tumor progression. From the therapeutic standpoint, we will go through the evolution of immune-based therapeutic approaches over time, including i) agents with broad immunomodulatory effects, such as immunomodulatory drugs, ii) currently approved and next-generation monoclonal antibodies, and iii) immunotherapeutic strategies aiming at activating or administering immune effector cells specifically targeting leukemic cells (e.g. bi-or tri-specific antibodies, tumor vaccines, chimeric antigen receptor T cells, and checkpoint inhibitors).