Combining CAR T cells and the Bcl-2 family apoptosis inhibitor ABT-737 for treating B-cell malignancy

TPGS nanoparticles co-loaded with ABT-737 and R848 for breast cancer therapy

The development of new effective drugs to treat breast cancer remains a huge challenge. ABT-737 can inhibit Bcl-2 proteins to promote apoptosis. Resiquimod (R848) is a TLR7/8 agonist that is effective in modulating the immunosuppressive microenvironment. In this study, a codelivery system (TPGS/ABT+R848 NPs) based on D-α-tocopheryl poly (ethylene glycol) 1000 succinate as a potential drug delivery vector to codelivery ABT-737 and R848 was investigated. The size of TPGS/ABT+R848 NPs was 102.5 nm, the drug loading of ABT-737 and R848 was 30.6 % and 12.5 %, and the entrapment efficiency was 84.2 % and 23.7 %, respectively. The nanoparticles showed no significant change in particle size over 14 days. R848 and ABT-737 were released in co-loaded nanoparticles in sequential order. In vitro anti-tumor experiments, the IC50 value of TPGS/ABT+R848 NPs was 0.30 μg·mL-1, 34 times lower than that of free ABT-737. Animal experiments also verified that TPGS/ABT+R848 NPs could enhance the anti-tumor activity, and the tumor weight inhibition rate was 75.3 %. This study demonstrated that TPGS NPs loaded with ABT-737 and R848 have superior combination tumor therapeutic effects, and the co-loaded preparation is conducive to anti-tumor efficacy. The TPGS/ABT+R848 NPs could be a promising platform against breast cancer.

Overcoming the challenges of primary resistance and relapse after CAR-T cell therapy

INTRODUCTION

While CAR T-cell therapy has led to remarkable responses in relapsed B-cell hematologic malignancies, only 50% of patients ultimately have a complete, sustained response. Understanding the mechanisms of resistance and relapse after CAR T-cell therapy is crucial to future development and improving outcomes.

AREAS COVERED

We review reasons for both primary resistance and relapse after CAR T-cell therapies. Reasons for primary failure include CAR T-cell manufacturing problems, suboptimal fitness of autologous T-cells themselves, and intrinsic features of the underlying cancer and tumor microenvironment. Relapse after initial response to CAR T-cell therapy may be antigen-positive, due to CAR T-cell exhaustion or limited persistence, or antigen-negative, due to antigen-modulation on the target cells. Finally, we discuss ongoing efforts to overcome resistance to CAR T-cell therapy with enhanced CAR constructs, manufacturing methods, alternate cell types, combinatorial strategies, and optimization of both pre-infusion conditioning regimens and post-infusion consolidative strategies.

EXPERT OPINION

There is a continued need for novel approaches to CAR T-cell therapy for both hematologic and solid malignancies to obtain sustained remissions. Opportunities for improvement include development of new targets, optimally combining existing CAR T-cell therapies, and defining the role for adjunctive immune modulators and stem cell transplant in enhancing long-term survival.

Advances in molecular targeted drugs in combination with CAR-T cell therapy for hematologic malignancies

Molecular targeted drugs and chimeric antigen receptor (CAR) T cell therapy represent specific biological treatments that have significantly improved the efficacy of treating hematologic malignancies. However, they face challenges such as drug resistance and recurrence after treatment. Combining molecular targeted drugs and CAR-T cells could regulate immunity, improve tumor microenvironment (TME), promote cell apoptosis, and enhance sensitivity to tumor cell killing. This approach might provide a dual coordinated attack on cancer cells, effectively eliminating minimal residual disease and overcoming therapy resistance. Moreover, molecular targeted drugs can directly or indirectly enhance the anti-tumor effect of CAR-T cells by inducing tumor target antigen expression, reversing CAR-T cell exhaustion, and reducing CAR-T cell associated toxic side effects. Therefore, combining molecular targeted drugs with CAR-T cells is a promising and novel tactic for treating hematologic malignancies. In this review article, we focus on analyzing the mechanism of therapy resistance and its reversal of CAR-T cell therapy resistance, as well as the synergistic mechanism, safety, and future challenges in CAR-T cell therapy in combination with molecular targeted drugs. We aim to explore the benefits of this combination therapy for patients with hematologic malignancies and provide a rationale for subsequent clinical studies.

CD19 occupancy with tafasitamab increases therapeutic index of CART19 cell therapy and diminishes severity of CRS

ABSTRACT

In the development of various strategies of anti-CD19 immunotherapy for the treatment of B-cell malignancies, it remains unclear whether CD19 monoclonal antibody therapy impairs subsequent CD19-targeted chimeric antigen receptor T-cell (CART19) therapy. We evaluated the potential interference between the CD19-targeting monoclonal antibody tafasitamab and CART19 treatment in preclinical models. Concomitant treatment with tafasitamab and CART19 showed major CD19 binding competition, which led to CART19 functional impairment. However, when CD19+ cell lines were pretreated with tafasitamab overnight and the unbound antibody was subsequently removed from the culture, CART19 function was not affected. In preclinical in vivo models, tafasitamab pretreatment demonstrated reduced incidence and severity of cytokine release syndrome and exhibited superior antitumor effects and overall survival compared with CART19 alone. This was associated with transient CD19 occupancy with tafasitamab, which in turn resulted in the inhibition of CART19 overactivation, leading to diminished CAR T apoptosis and pyroptosis of tumor cells.

Quantifying requirements for mitochondrial apoptosis in CAR T killing of cancer cells

Chimeric antigen receptor (CAR) T cell therapy is an FDA-approved treatment for several hematologic malignancies, yet not all patients respond to this treatment. While some resistance mechanisms have been identified, cell death pathways in target cancer cells remain underexplored. Impairing mitochondrial apoptosis via knockout of Bak and Bax, forced Bcl-2 and Bcl-XL expression, or caspase inhibition protected several tumor models from CAR T killing. However, impairing mitochondrial apoptosis in two liquid tumor cell lines did not protect target cells from CAR T killing. We found that whether a cell was Type I or Type II in response to death ligands explained the divergence of these results, so that mitochondrial apoptosis was dispensable for CART killing of cells that were Type I but not Type II. This suggests that the apoptotic signaling induced by CAR T cells bears important similarities to that induced by drugs. Combinations of drug and CAR T therapies will therefore require tailoring to the specific cell death pathways activated by CAR T cells in different types of cancer cells.

Apoptosis: a Janus bifrons in T-cell immunotherapy

Immunotherapy has revolutionized the treatment of cancer. In particular, immune checkpoint blockade, bispecific antibodies, and adoptive T-cell transfer have yielded unprecedented clinical results in hematological malignancies and solid cancers. While T cell-based immunotherapies have multiple mechanisms of action, their ultimate goal is achieving apoptosis of cancer cells. Unsurprisingly, apoptosis evasion is a key feature of cancer biology. Therefore, enhancing cancer cells' sensitivity to apoptosis represents a key strategy to improve clinical outcomes in cancer immunotherapy. Indeed, cancer cells are characterized by several intrinsic mechanisms to resist apoptosis, in addition to features to promote apoptosis in T cells and evade therapy. However, apoptosis is double-faced: when it occurs in T cells, it represents a critical mechanism of failure for immunotherapies. This review will summarize the recent efforts to enhance T cell-based immunotherapies by increasing apoptosis susceptibility in cancer cells and discuss the role of apoptosis in modulating the survival of cytotoxic T lymphocytes in the tumor microenvironment and potential strategies to overcome this issue.

Emerging Therapeutic Approaches to Target the Dark Side of Senescent Cells: New Hopes to Treat Aging as a Disease and to Delay Age-Related Pathologies

Life expectancy has drastically increased over the last few decades worldwide, with important social and medical burdens and costs. To stay healthy longer and to avoid chronic disease have become essential issues. Organismal aging is a complex process that involves progressive destruction of tissue functionality and loss of regenerative capacity. One of the most important aging hallmarks is cellular senescence, which is a stable state of cell cycle arrest that occurs in response to cumulated cell stresses and damages. Cellular senescence is a physiological mechanism that has both beneficial and detrimental consequences. Senescence limits tumorigenesis, lifelong tissue damage, and is involved in different biological processes, such as morphogenesis, regeneration, and wound healing. However, in the elderly, senescent cells increasingly accumulate in several organs and secrete a combination of senescence associated factors, contributing to the development of various age-related diseases, including cancer. Several studies have revealed major molecular pathways controlling the senescent phenotype, as well as the ones regulating its interactions with the immune system. Attenuating the senescence-associated secretory phenotype (SASP) or eliminating senescent cells have emerged as attractive strategies aiming to reverse or delay the onset of aging diseases. Here, we review current senotherapies designed to suppress the deleterious effect of SASP by senomorphics or to selectively kill senescent cells by "senolytics" or by immune system-based approaches. These recent investigations are promising as radical new controls of aging pathologies and associated multimorbidities.

Small-Molecule Compounds Boost CAR-T Cell Therapy in Hematological Malignancies

OPINION STATEMENT

Although chimeric antigen receptor T cell immunotherapy has been successfully applied in patients with hematological malignancies, several obstacles still need to be overcome, such as high relapse rates and side effects. Overcoming the limitations of CAR-T cell therapy and boosting the efficacy of CAR-T cell therapy are urgent issues that must be addressed. The exploration of small-molecule compounds in combination with CAR-T cell therapies has achieved promising success in pre-clinical and clinical studies in recent years. Protein kinase inhibitors, demethylating drugs, HDAC inhibitors, PI3K inhibitors, immunomodulatory drugs, Akt inhibitors, mTOR inhibitors, and Bcl-2 inhibitors exhibited potential synergy in combination with CAR-T cell therapy. In this review, we will discuss the recent application of these combination therapies for improved outcomes of CAR-T cell therapy.

CARs and Drugs: Pharmacological Ways of Boosting CAR-T-Cell Therapy

The development of chimeric antigen receptor T cells (CAR-T cells) has marked a new era in cancer immunotherapy. Based on a multitude of durable complete remissions in patients with hematological malignancies, FDA and EMA approval was issued to several CAR products targeting lymphoid leukemias and lymphomas. Nevertheless, about 50% of patients treated with these approved CAR products experience relapse or refractory disease necessitating salvage strategies. Moreover, in the vast majority of patients suffering from solid tumors, CAR-T-cell infusions could not induce durable complete remissions so far. Crucial obstacles to CAR-T-cell therapy resulting in a priori CAR-T-cell refractory disease or relapse after initially successful CAR-T-cell therapy encompass antigen shutdown and CAR-T-cell dysfunctionality. Antigen shutdown predominately rationalizes disease relapse in hematological malignancies, and CAR-T-cell dysfunctionality is characterized by insufficient CAR-T-cell proliferation and cytotoxicity frequently observed in patients with solid tumors. Thus, strategies to surmount those obstacles are being developed with high urgency. In this review, we want to highlight different approaches to combine CAR-T cells with drugs, such as small molecules and antibodies, to pharmacologically boost CAR-T-cell therapy. In particular, we discuss how certain drugs may help to counteract antigen shutdown and CAR-T-cell dysfunctionality in both hematological malignancies and solid tumors.

Antigen-specific depletion of CD4+ T cells by CAR T cells reveals distinct roles of higher- and lower-affinity TCRs during autoimmunity

Both higher- and lower-affinity self-reactive CD4⁺ T cells are expanded in autoimmunity; however, their individual contribution to disease remains unclear. We addressed this question using peptide-MHCII chimeric antigen receptor (pMHCII-CAR) T cells to specifically deplete peptide-reactive T cells in mice. Integration of improvements in CAR engineering with TCR repertoire analysis was critical for interrogating in vivo the role of TCR affinity in autoimmunity. Our original MOG_35-55 pMHCII-CAR, which targeted only higher-affinity TCRs, could prevent the induction of experimental autoimmune encephalomyelitis (EAE). However, pMHCII-CAR enhancements to pMHCII stability, as well as increased survivability via overexpression of a dominant-negative Fas, were required to target lower-affinity MOG-specific T cells and reverse ongoing clinical EAE. Thus, these data suggest a model in which higher-affinity autoreactive T cells are required to provide the "activation energy" for initiating neuroinflammatory injury, but lower-affinity cells are sufficient to maintain ongoing disease.

Combination strategies to optimize the efficacy of chimeric antigen receptor T cell therapy in haematological malignancies

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the therapeutic landscape of haematological malignancies. However, resistance and relapse remain prominent limitations, and they are related to the limited persistence and efficacy of CAR T cells, downregulation or loss of tumour antigens, intrinsic resistance of tumours to death signalling, and immune suppressive microenvironment. Rational combined modality treatments are regarded as a promising strategy to further unlock the antitumor potential of CAR T cell therapy, which can be applied before CAR T cell infusion as a conditioning regimen or in ex vivo culture settings as well as concomitant with or after CAR T cell infusion. In this review, we summarize the combinatorial strategies, including chemotherapy, radiotherapy, haematopoietic stem cell transplantation, targeted therapies and other immunotherapies, in an effort to further enhance the effectiveness of this impressive therapy and benefit more patients.

Decitabine-primed tandem CD19/CD22 CAR-T therapy in relapsed/refractory diffuse large B-cell lymphoma patients

Chimeric antigen receptor T cell (CAR-T) therapy has emerged as highly effective in relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL), but only about 40% patients have achieved sustained responses. Here, we conducted a phase II clinical trial testing efficacy and toxicities of CAR-T therapy in R/R non-Hodgkin’s lymphoma patients (NCT03196830). Among enrolled patients, 33 R/R DLBCL patients pretreated with DFC (decitabine, fludarabine plus cyclophosphamide) lymphodepletion chemotherapy and infused with tandem CD19-CD22 based CAR-T cells were drawn out for efficacy and toxicities of CAR-T therapy evaluation. With a median follow-up of 10.9(0.6-29.0) months, the best overall response and complete remission (CR) rates were 90.9% and 63.6%, respectively. The median progression-free survival (PFS) was 10.2 months and overall survival (OS) was undefined. The 2-year OS and PFS rates were 54.3% and 47.2%, respectively. No severe grade 4 cytokine release syndrome (CRS) was observed and grade 3 CRS was observed in only 7 patients; 3 patients developed mild immune effect or cell-associated neurotoxic syndrome. All toxicities were transient and reversible and no CAR-T-related mortality. Further subgroup analysis showed that achieving CR was an independent prognostic factor associated with favorable PFS and OS. The 2-year OS and PFS for patients who achieved CR within 3 months (undefined versus undefined P=0.021 and undefined versus undefined P=0.036) or during the follow-up period were significantly longer than those who did not (undefined versus 4.6 months P < 0.0001 and undefined versus 2.0months P<0.001). While severe CRS was also an independent prognostic factor but associated with inferior PFS and OS. The 2-year OS and PFS for patients with grade 3 CRS were significantly shorter than those with grade 0-2 CRS (4.1 months versus undefined P<0.0001 and 1.7 months versus undefined P=0.0002). This study indicated that CD19/CD22 dual-targeted CAR-T therapy under a decitabine-containing lymphodepletion regimen may be a safe, potent effective approach to R/R DLBCL patients.

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.

Site-Specific Considerations on Engineered T Cells for Malignant Gliomas

Immunotherapy has revolutionized cancer treatment. Despite the recent advances in immunotherapeutic approaches for several tumor entities, limited response has been observed in malignant gliomas, including glioblastoma (GBM). Conversely, one of the emerging immunotherapeutic modalities is chimeric antigen receptors (CAR) T cell therapy, which demonstrated promising clinical responses in other solid tumors. Current pre-clinical and interventional clinical studies suggest improved efficacy when CAR-T cells are delivered locoregionally, rather than intravenously. In this review, we summarize possible CAR-T cell administration routes including locoregional therapy, systemic administration with and without focused ultrasound, direct intra-arterial drug delivery and nanoparticle-enhanced delivery in glioma. Moreover, we discuss published as well as ongoing and planned clinical trials involving CAR-T cell therapy in malignant glioma. With increasing neoadjuvant and/or adjuvant combinatorial immunotherapeutic concepts and modalities with specific modes of action for malignant glioma, selection of administration routes becomes increasingly important.

Resistance against anti-CD19 and anti-BCMA CAR T cells: Recent advances and coping strategies

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Some patients may experience resistance to CD19 CAR T cell and BCMA CAR T cell therapies or relapse after treatment.

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Mechanisms of resistance to CAR T cell therapies may be related to CAR structure, T cell factors or tumor associated factors.

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The strategies to overcome the resistance would allow CD19 CAR T cells or BCMA CAR T cell to be applied with a broader perspective.

Chimeric antigen receptor T (CAR T) cell therapy is a new treatment paradigm that has revolutionized the treatment of CD19-positive B cell malignancies and BCMA-positive plasma cell malignancies. The response rates are highly impressive in comparison to historical cohorts, but the responses are not durable. The most recent results from pivotal trials show that current CAR T cell products fail to demonstrate optimal long-term disease control. Resistance to CAR T cells is related to CAR structure, T cell factors, tumor factors and the immunosuppressive microenvironment. Novel strategies are needed following failure with CAR T cell treatment. In this review, we discuss the resistance mechanisms to CAR T cell treatment according to disease and the emerging strategies to overcome resistance.

Relapsed/Refractory Mantle Cell Lymphoma: Beyond BTK Inhibitors

Mantle cell lymphoma (MCL) is a rare mature B-cell non-Hodgkin lymphoma (B-NHL) with historically poor outcomes. Virtually all patients will eventually experience refractory or relapsed (R/R) disease, with a virulent course of resistance and serial relapses, making treatment challenging. The available therapies for R/R MCL are not curative with conventional therapy, their goal being to palliate and prolong survival. A variety of agents approved for R/R MCL, including Bruton's tyrosine kinase inhibitors (BTKi), changed the treatment landscape of R/R MCL. In the pre-BTKi era, the median progression-free survival (PFS) in R/R disease was 4-9 months. With the introduction of ibrutinib, the median PFS improved to 13-14.6 months. Despite these impressive results, the duration of response is limited, and resistance to BTKi inevitably develops in a subset of patients. Outcomes after progression on BTKi are extremely poor, with a median overall survival (OS) of 6 to 10 months. Certain therapies, such as chimeric antigen receptor (CAR) T cells, have shown promising results after BTKi failure. The preferred combination and sequencing of therapies beyond BTKi remain unestablished and are currently being investigated. In this review, we describe the current evidence for the available treatment of R/R MCL after progression on BTKi.

Enhanced Chimeric Antigen Receptor T Cell Therapy through Co-Application of Synergistic Combination Partners

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable response rates and revolutionized the treatment of patients suffering from defined hematological malignancies. However, many patients still do not respond to this therapy or relapse after an initial remission, underscoring the need for improved efficacy. Insufficient in vivo activity, persistence, trafficking, and tumor infiltration of CAR T cells, as well as antigen escape and treatment-associated adverse events, limit the therapeutic success. Multiple strategies and approaches have been investigated to further improve CAR T cell therapy. Besides genetic modification of the CAR itself, the combination with other treatment modalities has the potential to improve this approach. In particular, combining CAR T cells with clinically approved compounds such as monoclonal antibodies and small molecule inhibitors might be a promising strategy. Combination partners could already be applied during the production process to influence the cellular composition and immunophenotype of the final CAR T cell product. Alternatively, simultaneous administration of clinically approved compounds with CAR T cells would be another feasible avenue. In this review, we will discuss current strategies to combine CAR T cells with compounds to overcome recent limitations and further enhance this promising cancer therapy, potentially broadening its application beyond hematology.

B7-H3 inhibits apoptosis of gastric cancer cell by interacting with Fibronectin

Anti-apoptosis has been widely accepted as a hallmark of malignancy. B7-H3, a type I transmembrane protein, plays a key role in anti-apoptosis and immune escape, but its regulation during cancer development remains unclear. To investigate how the effect of anti-apoptosis is regulated by B7-H3 in gastric cancer, we stably knocked down B7-H3 gene by shRNA in MGC-803 and MKN-45 cells. The correlation between B7-H3 and Fibronectin (FN) expression were investigated by bioinformatics in public data from TCGA (The Cancer Genome Atlas). Here, we reported that B7-H3 expression is positively correlated with FN in clinical gastric cancer samples, and B7-H3 promoted adhesion and inhibited apoptosis of gastric cancer cell through an FN-dependent pathway. Mechanistically, B7-H3 interacted with FN and subsequently activated PI3K/AKT signaling pathway, a critical mediator of oncogenic signaling. In addition, exogenous FN could inhibit the expression of pro-apoptosis-related proteins such as Caspase 3, Caspase 8, Caspase 9, Bax , p53, Apaf-1 and Cleaved PARP, and upregulated the levels of signal molecule p-PI3K, p-AKT and anti-apoptotic proteins Bcl-2 in B7-H3^high group, as compared with those in B7-H3^low group. In conclusion, we here for the first time revealed that B7-H3 inhibits apoptosis of gastric cancer cell through regulation of FN-mediated PI3K/AKT signaling pathways.

Pediatric multicellular tumor spheroid models illustrate a therapeutic potential by combining BH3 mimetics with Natural Killer (NK) cell-based immunotherapy

The induction of apoptosis is a direct way to eliminate tumor cells and improve cancer therapy. Apoptosis is tightly controlled by the balance of pro- and antiapoptotic Bcl-2 proteins. BH3 mimetics neutralize the antiapoptotic function of Bcl-2 proteins and are highly promising compounds inducing apoptosis in several cancer entities including pediatric malignancies. However, the clinical application of BH3 mimetics in solid tumors is impeded by the frequent resistance to single BH3 mimetics and the anticipated toxicity of high concentrations or combination treatments. One potential avenue to increase the potency of BH3 mimetics is the development of immune cell-based therapies to counteract the intrinsic apoptosis resistance of tumor cells and sensitize them to immune attack. Here, we describe spheroid cultures of pediatric cancer cells that can serve as models for drug testing. In these 3D models, we were able to demonstrate that activated allogeneic Natural Killer (NK) cells migrated into tumor spheroids and displayed cytotoxicity against a wide range of pediatric cancer spheroids, highlighting their potential as anti-tumor effector cells. Next, we investigated whether treatment of tumor spheroids with subtoxic concentrations of BH3 mimetics can increase the cytotoxicity of NK cells. Notably, the cytotoxic effects of NK cells were enhanced by the addition of BH3 mimetics. Treatment with either the Bcl-X_L inhibitor A1331852 or the Mcl-1 inhibitor S63845 increased the cytotoxicity of NK cells and reduced spheroid size, while the Bcl-2 inhibitor ABT-199 had no effect on NK cell-mediated killing. Taken together, this is the first study to describe the combination of BH3 mimetics targeting Bcl-X_L or Mcl-1 with NK cell-based immunotherapy, highlighting the potential of BH3 mimetics in immunotherapy.

Quantification of cell-free DNA for the analysis of CD19-CAR-T cells during lymphoma treatment

Chimeric antigen receptor (CAR)-T cells are increasingly used for the treatment of hematologic malignancies. Treatment success relies highly upon sufficient expansion of CAR-T effector cells. Accordingly, longitudinal quantification of CAR-T cells during therapy is clinically important. Techniques to quantify CAR-T cells in patient blood samples are based on flow cytometry and PCR. However, cellular kinetics of CAR-T cells are very complex and under current investigation. In this study, feasibility of CAR-T cell quantification by cell-free DNA (cfDNA) was analyzed. cfDNA isolated from 74 blood samples of 12 patients during lymphoma treatment with the anti-CD19 CAR-T cell product axicabtagene ciloleucel (axi-cel) were analyzed. Concentrations of cfDNA specific for the CAR-T gene construct (cfCAR-DNA) and a reference gene were quantified by a newly designed digital-droplet PCR (ddPCR) assay. Detection and quantification of cfCAR-DNA was feasible and reliable for all patients included. Relative quantification of cfCAR-DNA compared to a reference gene, suitable for genomic DNA analysis, was heterogeneous in treatment responders and non-responders. In contrast, parallel analyses of cfCAR-DNA and reference cfDNA in a patient-specific approach gave insight into active lymphoma killing and treatment responses. In summary, plasma cfDNA determination in lymphoma patients is a promising tool for future clinical decision making.

[Preliminary study on the effect of B7H3 interaction with fibronectin on apoptosis of human chronic myeloid leukemia cells]

Objective: To explore the effect of the interaction between B7H3 and fibronectin (FN) on the apoptosis of human chronic myeloid leukemia K562 cells. Methods: The expression of B7H3 molecules in K562 cells was detected using flow cytometry and B7H3 overexpressing cells were constructed. The interaction between B7H3 and FN was detected using the co-immunoprecipitation technology. After adding exogenous FN, cell experiments were performed to detect changes in adhesion and cell apoptosis. The changes in apoptosis-related proteins and PI3K/AKT signaling pathway were detected using Western blot. Results: The expression of B7H3 was low in K562, and the cell line K562 OE (overexpression) -B7H3 and the control cell line K562 NC (negative control) -B7H3 were obtained after lentivirus transfection. There is an interaction between B7H3 and FN (P=0.036) , and this interaction promoted cell adhesion (P<0.05) , inhibited cell apoptosis (P<0.05) , and activated the PI3K/AKT signaling pathway (P<0.05) . Conclusion: B7H3 interacts with FN to promote cell adhesion and may inhibit K562 cell apoptosis by activating the PI3K/AKT signaling pathway.

Genetic Events Inhibiting Apoptosis in Diffuse Large B Cell Lymphoma

Simple Summary

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL). Despite the genetic heterogeneity of the disease, most patients are initially treated with a combination of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), but relapse occurs in ~50% of patients. One of the hallmarks of DLBCL is the occurrence of genetic events that inhibit apoptosis, which contributes to disease development and resistance to therapy. These events can affect the intrinsic or extrinsic apoptotic pathways, or their modulators. Understanding the factors that contribute to inhibition of apoptosis in DLBCL is crucial in order to be able to develop targeted therapies and improve outcomes, particularly in relapsed and refractory DLBCL (rrDLBCL). This review provides a description of the genetic events inhibiting apoptosis in DLBCL, their contribution to lymphomagenesis and chemoresistance, and their implication for the future of DLBCL therapy.

Abstract

Diffuse large B cell lymphoma (DLBCL) is curable with chemoimmunotherapy in ~65% of patients. One of the hallmarks of the pathogenesis and resistance to therapy in DLBCL is inhibition of apoptosis, which allows malignant cells to survive and acquire further alterations. Inhibition of apoptosis can be the result of genetic events inhibiting the intrinsic or extrinsic apoptotic pathways, as well as their modulators, such as the inhibitor of apoptosis proteins, P53, and components of the NF-kB pathway. Mechanisms of dysregulation include upregulation of anti-apoptotic proteins and downregulation of pro-apoptotic proteins via point mutations, amplifications, deletions, translocations, and influences of other proteins. Understanding the factors contributing to resistance to apoptosis in DLBCL is crucial in order to be able to develop targeted therapies that could improve outcomes by restoring apoptosis in malignant cells. This review describes the genetic events inhibiting apoptosis in DLBCL, provides a perspective of their interactions in lymphomagenesis, and discusses their implication for the future of DLBCL therapy.

Pharmacologic Control of CAR T Cells

Chimeric antigen receptor (CAR) therapy is a promising modality for the treatment of advanced cancers that are otherwise incurable. During the last decade, different centers worldwide have tested the anti-CD19 CAR T cells and shown clinical benefits in the treatment of B cell tumors. However, despite these encouraging results, CAR treatment has also been found to lead to serious side effects and capricious response profiles in patients. In addition, the CD19 CAR success has been difficult to reproduce for other types of malignancy. The appearance of resistant tumor variants, the lack of antigen specificity, and the occurrence of severe adverse effects due to over-stimulation of the therapeutic cells have been identified as the major impediments. This has motivated a growing interest in developing strategies to overcome these hurdles through CAR control. Among them, the combination of small molecules and approved drugs with CAR T cells has been investigated. These have been exploited to induce a synergistic anti-cancer effect but also to control the presence of the CAR T cells or tune the therapeutic activity. In the present review, we discuss opportunistic and rational approaches involving drugs featuring anti-cancer efficacy and CAR-adjustable effect.

Targeting macrophages in cancer immunotherapy

Immunotherapy is regarded as the most promising treatment for cancers. Various cancer immunotherapies, including adoptive cellular immunotherapy, tumor vaccines, antibodies, immune checkpoint inhibitors, and small-molecule inhibitors, have achieved certain successes. In this review, we summarize the role of macrophages in current immunotherapies and the advantages of targeting macrophages. To better understand and make better use of this type of cell, their development and differentiation characteristics, categories, typical markers, and functions were collated at the beginning of the review. Therapeutic strategies based on or combined with macrophages have the potential to improve the treatment efficacy of cancer therapies.

Pre-sensitization of Malignant B Cells Through Venetoclax Significantly Improves the Cytotoxic Efficacy of CD19.CAR-T Cells

Chimeric antigen receptor (CAR) T cell therapy has shown promising responses in patients with refractory or relapsed aggressive B-cell malignancies that are resistant to conventional chemotherapy or stem cell transplantation. A potentially combinatorial therapeutic strategy may be the inhibition of anti-apoptotic Bcl-2 family proteins, overexpressed in most cancer cells. In this study we investigated the combination of 3rd-generation CD19.CAR-T cells and the BH3 mimetics venetoclax, a Bcl-2 inhibitor, or S63845, a Mcl-1 inhibitor, under three different treatment conditions: pre-sensitization of cancer cells with BH3 mimetics followed by CAR-T cell treatment, simultaneous combination therapy, and the administration of BH3 mimetics after CAR-T cell treatment. Our results showed that administration of CAR-T cells and BH3 mimetics had a significant effect on the quantity and quality of CD19.CAR-T cells. The administration of BH3 mimetics prior to CAR-T cell therapy exerted an enhanced cytotoxic efficacy by upregulating the CD19 expression and pro-apoptotic proteins in highly sensitive tumor cells, and thereby improving both CD19.CAR-T cell cytotoxicity and persistence. In simultaneous and post-treatment approaches, however, the quantity of CAR-T cells was adversely affected. Our findings indicate pre-sensitization of highly sensitive tumor cells with BH3 mimetics could enhance the cytotoxic efficacy of CAR-T cell treatment.

RNA-electroporated T cells for cancer immunotherapy

Adoptive T cell therapy has proven effective against hematologic malignancies and demonstrated efficacy against a variety of solid tumors in preclinical studies and clinical trials. Nonetheless, antitumor responses against solid tumors remain modest, highlighting the need to enhance the effectiveness of this therapy. Genetic modification of T cells with RNA has been explored to enhance T-cell antigen specificity, effector function, and migration to tumor sites, thereby potentiating antitumor immunity. This review describes the rationale for RNA-electroporated T cell modifications and provides an overview of their applications in preclinical and clinical investigations for the treatment of hematologic malignancies and solid tumors.

Complete remission in refractory acute lymphoblastic leukemia using blinatumomab after failure of response to CD-19 chimeric antigen receptor T-cell therapy

The T-cell engager monoclonal antibody, blinatumomab, is a potential therapeutic strategy for refractory B acute lymphoblastic leukemia after failure of CD 19 chimeric antigen receptor T-cell therapy.

Chimeric antigen receptor therapy in hematological malignancies: antigenic targets and their clinical research progress

Chimeric antigen receptor (CAR)-based immunotherapy has achieved dramatic success in the treatment of B cell malignancies, based on the summary of current research data, and has shown good potential in early phase cancer clinical trials. Modified constructs are being optimized to recognize and destroy tumor cells more effectively. By targeting the proper B-lineage-specific antigens such as CD19 and CD20, adoptive immunotherapy has demonstrated promising clinical results and already plays a role in the treatment of several lymphoid malignancies, which highlights the importance of target selection for other CAR therapies. The high efficacy of CAR-T cells has resulted in the approval of anti-CD19-directed CAR-T cells for the treatment of B cell malignancies. In this review, we focus on the basic structure and current clinical application of CAR-T cells, detail the research progress of CAR-T for different antigenic targets in hematological malignancies, and further discuss the current barriers and proposed solutions, investigating the possible mechanisms of recurrence of CAR-T cell therapy. A summary of the paper is also given to overview as the prospects for this therapy.

Challenges and Opportunities for High-grade B-Cell Lymphoma With MYC and BCL2 and/or BCL6 Rearrangement (Double-hit Lymphoma)

The most common subtype of non-Hodgkin lymphoma, diffuse large B-cell lymphoma, is cured in approximately two thirds of patients after initial therapy. The remaining one-third of patients who suffer relapse or become refractory have very poor survival outcomes despite salvage chemotherapy with or without stem cell transplantation. A considerable proportion of relapsed or refractory large B cells belong to the WHO subtype known as high-grade B-cell lymphoma with rearrangement of MYC and BCL2 and/or BCL6, also known as double-hit lymphoma (DHL). Most DHL patients present with Ann Arbor's stage III/IV, a comparatively higher rate of extranodal involvement including bone marrow and central nervous system infiltration, high levels of lactate dehydrogenase, and an elevated Ki67 expression in the tumor cells. Newer therapeutic approaches, including targeted therapy against BCL2, MYC, or other associated pathways, are needed. In addition, recent therapies that harness the immune system, such as checkpoint inhibitors and chimeric antigen receptor T-cell therapy, are changing the paradigm of treatment for non-Hodgkin lymphoma and could impact the outcome of DHL.

Drug therapy for double-hit lymphoma

Double-hit lymphoma (DHL) is a rare type of aggressive B-cell lymphoma defined as a high-grade B-cell lymphoma (HGBCL) with the presence of MYC, BCL2 and/or BCL6 rearrangements. Patients usually present with rapidly progressive and advanced stage of disease and, commonly, with extranodal involvement. Typically, patients become refractory to standard R-CHOP, and more aggressive regimens such as DA-EPOCH-R, R-hyperCVAD or CODOX-R regimens are typically needed. MYC is considered an “undruggable” mutation. Recent evidence suggests that pathogenic mechanisms associated with MYC could be potential targets. In this review, we also discuss the role of hematopoietic stem cell transplantation (HCT) and chimeric antigen receptor (CAR) T-cell therapy in DHL. We also discuss the role of potential novel agents such as BCL2 inhibitors, checkpoint inhibitors, bromodomain and extraterminal (BET) family inhibitors, Pi3K inhibitors, and others.

Understanding the Mechanisms of Resistance to CAR T-Cell Therapy in Malignancies

Taking advantage of the immune system to exert an antitumor effect is currently a novel approach in cancer therapy. Adoptive transfer of T cells engineered to express chimeric antigen receptors (CARs) targeting a desired antigen has shown extraordinary antitumor activity, especially in refractory and relapsed B-cell malignancies. The most representative in this respect, as well as the most successful example, is CD19 CAR T-cell therapy in B-cell acute lymphoblastic leukemia (B-ALL). However, with the widespread use of CAR T-cell therapy, problems of resistance and relapse are starting to be considered. This review provides a comprehensive picture of the mechanisms of resistance to CAR T-cell therapy from three aspects, namely, CAR T-cell factors, tumor factors, and tumor microenvironment factors, offering insights for improving CAR T-cell therapy.

A good response of refractory mantel cell lymphoma to haploidentical CAR T cell therapy after failure of autologous CAR T cell therapy

Background

The aggressive form of Mantle cell non-hodgkin B cell lymphoma (MCL) has a dismal prognosis. Dual targeting BTK and BCL2 with ibrutinib and venetoclax has improved outcomes in MCL patients who were predicted not to respond to conventional therapy, but it is unlikely to be curative. Chimeric antigen receptor-modified T (CAR T) cells exhibit very effective function in elimination of relapsed/refractory B-cell lymphoid malignancies, we investigated their use in a patient with relapsed MCL.

Case presentation

Here, we report a case of a refractory MCL in a patient who had relapsed after conventional chemotherapy and autologous CAR T cell therapy. The patient received multiple molecularly targeted therapies, including targeting BTK and BCL2, and haplo-identical CAR T (haplo-CAR T) cells from her daughter without previous allo-hematopoietic stem cell transplantation. Haplo-CAR T cells could effectively proliferate in vivo and had a clinically significant antitumor activity without serious side effects. The patient achieved a partial remission, with minimal residual disease.

Conclusions

This case suggests that haplo-CAR T cell therapy can be effective in controlling lymphoma that failed to respond to autologous CAR T cell therapy and overcome limitation of autologous CAR T cells, thus may be one possible regimen before the era of off-the-shelf “universal” CAR T cell therapy.

Trial registration

ChiCTR-OPN-16008526. http://www.chictr.org.cn/showproj.aspx?proj=13798; ChiCTR1800019385. http://www.chictr.org.cn/showproj.aspx?proj=32805; ChiCTR1800019449. http://www.chictr.org.cn/showproj.aspx?proj=32778.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0529-9) contains supplementary material, which is available to authorized users.

Manipulating the tumor microenvironment by adoptive cell transfer of CAR T-cells

T-cells expressing synthetic chimeric antigen receptors (CARs) have revolutionized immuno-oncology and highlighted the use of adoptive cell transfer, for the treatment of cancer. The phenomenal clinical success obtained in the treatment of hematological malignancies with CAR T-cells has not been reproduced in the treatment of solid tumors, mainly due to the suppressive and hostile tumor microenvironment (TME). This review will address the immunosuppressive features of the TME, which include the stroma, cytokine and chemokine milieu, suppressive regulatory cells and hypoxic conditions, which can all pose formidable barriers for the effective anti-tumor function of CAR T-cells. Some of the novel next generation CARs that have been developed and tested against the TME, will be discussed, to highlight the status of current research in CAR T-cell therapy for solid tumors.

Targeting immuno-metabolism to improve anti-cancer therapies

The immunology community has made significant strides in recent years in using the immune system to target and eliminate cancer. Therapies such as hematopoietic stem cell transplantation (HSCT) are the standard of care treatment for several malignancies, while therapies incorporating chimeric antigen receptor (CAR) T cells or checkpoint molecule blockade have been revolutionary. However, these approaches are not optimal for all cancers and in some cases, have failed outright. The greatest obstacle to making these therapies more effective may be rooted in one of the most basic concepts of cell biology, metabolism. Research over the last decade has revealed that T cell proliferation and differentiation is intimately linked to robust changes in metabolic activity, delineation of which may provide ways to manipulate the immuno-oncologic responses to our advantage. Here, we provide a basic overview of T cell metabolism, discuss what is known about metabolic regulation of T cells during allogeneic HSCT, point to evidence on the importance of T cell metabolism during CAR T cell and solid tumor therapies, and speculate about the role for compounds that might have dual-action on both immune cells and tumor cells simultaneously.

Approaches to augment CAR T-cell therapy by targeting the apoptotic machinery

Chimaeric antigen receptor (CAR) T-cells have shown impressive results in patients with B-cell leukaemia. Yet, in patients with lymphoma durable responses are still rare and heavy preconditioning required. Apoptosis resistance is considered a hallmark of cancer, often conveyed by a halted apoptosis signalling. Tumours regularly skew the balance of the components of the apoptotic machinery either through up-regulating anti-apoptotic proteins or silencing pro-apoptotic ones. Malignant B-cells frequently up-regulate anti-apoptotic B-cell lymphoma 2 (Bcl-2) family proteins leading to therapy resistance. CAR T-cells kill tumour cells via apoptosis induction and their efficacy may be affected by the level of Bcl-2 family proteins. Hence, there is an interesting possibility to increase the effect of CAR T-cell therapy by combining it with apoptosis inhibitor blockade agents. Compounds that inhibit Bcl-2, B-cell lymphoma extra large (Bcl-xL) and Bcl-2-like protein 2 (Bcl-w), can restore execution of apoptosis in tumour cells or sensitize them to other apoptosis-dependent treatments. Hence, there is a great interest to combine such agents with CAR T-cell therapy to potentiate the effect of CAR T-cell killing. This review will focus on the potential of targeting the apoptotic machinery to sensitize tumour cells to CAR T-cell killing.

In Vitro Pre-Clinical Validation of Suicide Gene Modified Anti-CD33 Redirected Chimeric Antigen Receptor T-Cells for Acute Myeloid Leukemia

Background

Approximately fifty percent of patients with acute myeloid leukemia can be cured with current therapeutic strategies which include, standard dose chemotherapy for patients at standard risk of relapse as assessed by cytogenetic and molecular analysis, or high-dose chemotherapy with allogeneic hematopoietic stem cell transplant for high-risk patients. Despite allogeneic hematopoietic stem cell transplant about 25% of patients still succumb to disease relapse, therefore, novel strategies are needed to improve the outcome of patients with acute myeloid leukemia.

Methods and findings

We developed an immunotherapeutic strategy targeting the CD33 myeloid antigen, expressed in ~ 85–90% of patients with acute myeloid leukemia, using chimeric antigen receptor redirected T-cells. Considering that administration of CAR T-cells has been associated with cytokine release syndrome and other potential off-tumor effects in patients, safety measures were here investigated and reported. We genetically modified human activated T-cells from healthy donors or patients with acute myeloid leukemia with retroviral supernatant encoding the inducible Caspase9 suicide gene, a ΔCD19 selectable marker, and a humanized third generation chimeric antigen receptor recognizing human CD33. ΔCD19 selected inducible Caspase9-CAR.CD33 T-cells had a 75±3.8% (average ± standard error of the mean) chimeric antigen receptor expression, were able to specifically lyse CD33⁺ targets in vitro, including freshly isolated leukemic blasts from patients, produce significant amount of tumor-necrosis-factor-alpha and interferon-gamma, express the CD107a degranulation marker, and proliferate upon antigen specific stimulation. Challenging ΔCD19 selected inducible Caspase9-CAR.CD33 T-cells with programmed-death-ligand-1 enriched leukemia blasts resulted in significant killing like observed for the programmed-death-ligand-1 negative leukemic blasts fraction. Since the administration of 10 nanomolar of a non-therapeutic dimerizer to activate the suicide gene resulted in the elimination of only 76.4±2.0% gene modified cells in vitro, we found that co-administration of the dimerizer with either the BCL-2 inhibitor ABT-199, the pan-BCL inhibitor ABT-737, or mafosfamide, resulted in an additive effect up to complete cell elimination.

Conclusions

This strategy could be investigated for the safety of CAR T-cell applications, and targeting CD33 could be used as a ‘bridge” therapy for patients coming to allogeneic hematopoietic stem cell transplant, as anti-leukemia activity from infusing CAR.CD33 T-cells has been demonstrated in an ongoing clinical trial. Albeit never performed in the clinical setting, our future plan is to investigate the utility of iC9-CAR.CD33 T-cells as part of the conditioning therapy for an allogeneic hematopoietic stem cell transplant for acute myeloid leukemia, together with other myelosuppressive agents, whilst the activation of the inducible Caspase9 suicide gene would grant elimination of the infused gene modified T-cells prior to stem cell infusion to reduce the risk of engraftment failure as the CD33 is also expressed on a proportion of the donor stem cell graft.

Norcantharidin combined with ABT-737 for hepatocellular carcinoma: Therapeutic effects and molecular mechanisms

AIM: To study the therapeutic effect of norcantharidin (NCTD) combined with ABT-737 on hepatocellular carcinoma cells and the molecular mechanism.

METHODS: Two hepatocellular carcinoma (HCC) cell lines, HepG2 and SMMC-7721, were selected. ABT-737 and NCTD were allocated into groups to be used alone or in combination. HepG2 and SMMC-7721 cells were cultured in vitro. Liver cancer cells in the logarithmic phase of growth were vaccinated and cultured to the cell wall stage; these cells were treated for 48 h with different concentrations of NCTD, or ABT-737, or NCTD combined with ABT-737. The cell proliferation inhibition rate was detected by methyl thiazolyl tetrazolium. The expression of Mcl in HCC cells was detected by Western Blotting, and the cells in each group after treatment had apoptosis detected by flow cytometry. The proliferation inhibition rate, the expression of Mcl-1 in cells and the apoptosis inducing effect of treatment were observed in each group, and the effect of NCTD on ABT-737 in the treatment of HCC and its mechanism of action were analyzed.

RESULTS: As the concentration of NCTD increased, the cell proliferation inhibition rate gradually decreased; and the treatment effect of ABT-737 1-3 μm combined with NCTD on cell proliferation inhibition was stronger than that of ABT-737 alone. The difference was statistically significant (P < 0.05). In observing the expression of Mcl-1 in cells after the treatment of different concentrations of NCTD, this was partially inhibited after treatment with NCTD 15 μm, and the expression of Mcl-1 was almost undetectable after treatment with NCTD 30 μm and 60 μm. The effect on inducing apoptosis with the treatment of ABT-737 or NCTD alone for 48 h was lower than that of the control group. The difference was not statistically significant (P > 0.05). The effect on inducing apoptosis in HepG2 and SMMC-7721 cells with the treatment of ABT-737 combined with NCTD for 48 h was greater than that of ABT-737 or NCTD alone. The difference was statistically significant (P < 0.05).

CONCLUSION: NCTD combined with ABT-737 has a positive role in the treatment of HCC, and it has great value in clinical research.

Killing Two Cells with One Stone: Pharmacologic BCL-2 Family Targeting for Cancer Cell Death and Immune Modulation

A crucial component of regulating organismal homeostasis is maintaining proper cell number and eliminating damaged or potentially malignant cells. Apoptosis, or programed cell death, is the mechanism responsible for this equilibrium. The intrinsic apoptotic pathway is also especially important in the development and maintenance of the immune system. Apoptosis is essential for proper positive and negative selection during B- and T-cell development and for efficient contraction of expanded lymphocytes following an immune response. Tight regulation of the apoptotic pathway is critical, as excessive cell death can lead to immunodeficiency while apoptotic resistance can lead to aberrant lymphoproliferation and autoimmune disease. Dysregulation of cell death is implicated in a wide range of hematological malignancies, and targeting various components of the apoptotic machinery in these cases is an attractive chemotherapeutic strategy. A wide array of compounds has been developed with the purpose of reactivating the intrinsic apoptotic pathway. These compounds, termed BH3 mimetics are garnering considerable attention as they gain greater clinical oncologic significance. As their use expands, it will be imperative to understand the effects these compounds have on immune homeostasis. Uncovering their potential immunomodulatory activity may allow for administration of BH3 mimetics for direct tumor cell killing as well as novel therapies for a wide range of immune-based directives. This review will summarize the major proteins involved in the intrinsic apoptotic pathway and define their roles in normal immune development and disease. Clinical and preclinical BH3 mimetics are described within the context of what is currently known about their ability to affect immune function. Prospects for future antitumor immune amplification and immune modulation are then proposed.

Novel immunotherapies in lymphoid malignancies

The success of the anti-CD20 monoclonal antibody rituximab in the treatment of lymphoid malignancies provided proof-of-principle for exploiting the immune system therapeutically. Since the FDA approval of rituximab in 1997, several novel strategies that harness the ability of T cells to target cancer cells have emerged. Reflecting on the promising clinical efficacy of these novel immunotherapy approaches, the FDA has recently granted 'breakthrough' designation to three novel treatments with distinct mechanisms. First, chimeric antigen receptor (CAR)-T-cell therapy is promising for the treatment of adult and paediatric relapsed and/or refractory acute lymphoblastic leukaemia (ALL). Second, blinatumomab, a bispecific T-cell engager (BiTE(®)) antibody, is now approved for the treatment of adults with Philadelphia-chromosome-negative relapsed and/or refractory B-precursor ALL. Finally, the monoclonal antibody nivolumab, which targets the PD-1 immune-checkpoint receptor with high affinity, is used for the treatment of Hodgkin lymphoma following treatment failure with autologous-stem-cell transplantation and brentuximab vedotin. Herein, we review the background and development of these three distinct immunotherapy platforms, address the scientific advances in understanding the mechanism of action of each therapy, and assess the current clinical knowledge of their efficacy and safety. We also discuss future strategies to improve these immunotherapies through enhanced engineering, biomarker selection, and mechanism-based combination regimens.

Mesothelin-Targeted CARs: Driving T Cells to Solid Tumors

Chimeric antigen receptors (CAR) are synthetic receptors that target T cells to cell-surface antigens and augment T-cell function and persistence. Mesothelin is a cell-surface antigen implicated in tumor invasion, which is highly expressed in mesothelioma and lung, pancreas, breast, ovarian, and other cancers. Its low-level expression in mesothelia, however, commands thoughtful therapeutic interventions. Encouragingly, recent clinical trials evaluating active immunization or immunoconjugates in patients with pancreatic adenocarcinoma or mesothelioma have shown responses without toxicity. Altogether, these findings and preclinical CAR therapy models using either systemic or regional T-cell delivery argue favorably for mesothelin CAR therapy in multiple solid tumors.

SIGNIFICANCE

Recent success obtained with adoptive transfer of CAR T cells targeting CD19 in patients with refractory hematologic malignancies has generated much enthusiasm for T-cell engineering and raises the prospect of implementing similar strategies for solid tumors. Mesothelin is expressed in a wide range and a high percentage of solid tumors, which we review here in detail. Mesothelin CAR therapy has the potential to treat multiple solid malignancies.

Alternative Treatments For Melanoma: Targeting BCL-2 Family Members to De-Bulk and Kill Cancer Stem Cells

For the first time new treatments in melanoma have produced significant responses in advanced diseases, but 30-90% of melanoma patients do not respond or eventually relapse after the initial response to the current treatments. The resistance of these melanomas is likely due to tumor heterogeneity, which may be explained by models such as the stochastic, hierarchical, and phenotype-switching models. This review will discuss the recent advancements in targeting BCL-2 family members for cancer treatments, and how this approach can be applied as an alternative option to combat melanoma, and overcome melanoma relapse or resistance in current treatment regimens.

CD28z CARs and armored CARs

CD19-targeted chimeric antigen receptor (CAR) T cells are currently being tested in the clinic with very promising outcomes. However, limitations to CAR T cell therapy exist. These include lack of efficacy against some tumors, specific targeting of tumor cells without affecting normal tissue and retaining activity within the suppressive tumor microenvironment. Whereas promising clinical trials are in progress, preclinical development is focused on optimizing CAR design, to generate "armored CAR T cells," which are protected from the inhibitory tumor microenvironment. Studies investigating the expression of cytokine transgenes, combination therapy with small molecule inhibitors, or monoclonal antibodies, are aimed at improving the antitumor efficacy of CAR T cell therapy. Other strategies aimed at improving CAR T cell therapy include using dual CARs and chemokine receptors to more specifically target tumor cells. This review will describe the current clinical data and some novel armored CAR T cell approaches for improving antitumor efficacy therapy.

Adoptive immunotherapy for cancer

Recent clinical success has underscored the potential for immunotherapy based on the adoptive cell transfer (ACT) of engineered T lymphocytes to mediate dramatic, potent, and durable clinical responses. This success has led to the broader evaluation of engineered T-lymphocyte-based adoptive cell therapy to treat a broad range of malignancies. In this review, we summarize concepts, successes, and challenges for the broader development of this promising field, focusing principally on lessons gleaned from immunological principles and clinical thought. We present ACT in the context of integrating T-cell and tumor biology and the broader systemic immune response.

Trial Watch: Adoptive cell transfer for anticancer immunotherapy

The expression "adoptive cell transfer" (ACT) is commonly employed to indicate an immunotherapeutic regimen involving the isolation of autologous blood-borne or tumor-infiltrating lymphocytes, their selection/expansion/activation ex vivo, and their reinfusion into the patient, most often in the context of lymphodepleting pre-conditioning and in combination with immunostimulatory treatments. Optionally, the cellular material for ACT is genetically manipulated before expansion to (1) target specific tumor-associated antigens; (2) endogenously express immunostimulatory molecules; and/or (3) persist for long periods upon reinfusion. Consistent efforts have been dedicated at the amelioration of this immunotherapeutic regimen throughout the past decade, resulting in the establishment of ever more efficient and safer ACT protocols. Accordingly, the number of clinical trials testing ACT in oncological indications does not cease to increase. In this Trial Watch, we summarize recent developments in this exciting area of research, covering both high-impact studies that have been published during the last 12 months and clinical trials that have been launched in the same period to evaluate the safety and therapeutic potential of ACT in cancer patients.