'Off-the-shelf' allogeneic CAR T cells: development and challenges.

Autologous chimeric antigen receptor (CAR) T cells have changed the therapeutic landscape in haematological malignancies. Nevertheless, the use of allogeneic CAR T cells from donors has many potential advantages over autologous approaches, such as the immediate availability of cryopreserved batches for patient treatment, possible standardization of the CAR-T cell product, time for multiple cell modifications, redosing or combination of CAR T cells directed against different targets, and decreased cost using an industrialized process. However, allogeneic CAR T cells may cause life-threatening graft-versus-host disease and may be rapidly eliminated by the host immune system. The development of next-generation allogeneic CAR T cells to address these issues is an active area of research. In this Review, we analyse the different sources of T cells for optimal allogeneic CAR-T cell therapy and describe the different technological approaches, mainly based on gene editing, to produce allogeneic CAR T cells with limited potential for graft-versus-host disease. These improved allogeneic CAR-T cell products will pave the way for further breakthroughs in the treatment of cancer.

Pattern recognition receptors: immune targets to enhance cancer immunotherapy.

Durable tumor responses and significant levels of disease control rates have been described in more than 20 advanced/metastatic cancer types with B7-family immune checkpoint-targeted anti-CTLA-4, anti-PD-1, and anti-PD-L1 monoclonal antibodies. These results and the recent approvals of ipilimumab, pembrolizumab, nivolumab and atezolizumab are currently revolutionizing the way we envision the future of cancer care. However these clinical benefits are not observed in all cancer types and in every patient. Therefore, our clinical challenge is to identify therapeutic strategies which could overcome the primary and secondary resistances to these novel cancer immunotherapies. Pattern recognition receptors (PRRs) are other critical costimulatory molecules of immune cells, notably myeloid cells (macrophages and dendritic cells). They were initially described as sensors for 'danger signals' released by pathogens (e.g. viral DNA and bacterial proteins). We know now that PRRs can also be recruited and activated upon recognition of endogenous stress signals such as molecules released upon self-cell death (e.g. ATP and HMGB1). Natural endo/exogenous or synthetic PRRs agonists have notably the ability to activate phagocytosis and antigen presentation by myeloid cells residing in the tumor micro-environment. In pre-clinical models, these PRRs agonists have also been shown to overcome the resistance to T-cell targeted immune checkpoints anti-CTLA-4 and anti-PD-1/PD-L1. This manuscript reviews the current knowledge on this major family of immune receptors and the molecules targeting them which are currently in clinical development.

Radiosensitization by a novel Bcl-2 and Bcl-XL inhibitor S44563 in small-cell lung cancer.

Radiotherapy has a critical role in the treatment of small-cell lung cancer (SCLC). The effectiveness of radiation in SCLC remains limited as resistance results from defects in apoptosis. In the current study, we investigated whether using the Bcl-2/Bcl-XL inhibitor S44563 can enhance radiosensitivity of SCLC cells in vitro and in vivo. In vitro studies confirmed that S44563 caused SCLC cells to acquire hallmarks of apoptosis. S44563 markedly enhanced the sensitivity of SCLC cells to radiation, as determined by a clonogenic assay. The combination of S44563 and cisplatin-based chemo-radiation showed a significant tumor growth delay and increased overall survival in mouse xenograft models. This positive interaction was greater when S44563 was given after the completion of the radiation, which might be explained by the radiation-induced overexpression of anti-apoptotic proteins secondary to activation of the NF-κB pathway. These data underline the possibility of combining IR and Bcl-2/Bcl-XL inhibition in the treatment of SCLC as they underscore the importance of administering conventional and targeted therapies in an optimal sequence.

Thrombocytopenia induced by the histone deacetylase inhibitor abexinostat involves p53-dependent and -independent mechanisms.

Abexinostat is a pan histone deacetylase inhibitor (HDACi) that demonstrates efficacy in malignancy treatment. Like other HDACi, this drug induces a profound thrombocytopenia whose mechanism is only partially understood. We have analyzed its effect at doses reached in patient plasma on in vitro megakaryopoiesis derived from human CD34(+) cells. When added at day 0 in culture, abexinostat inhibited CFU-MK growth, megakaryocyte (MK) proliferation and differentiation. These effects required only a short incubation period. Decreased proliferation was due to induction of apoptosis and was not related to a defect in TPO/MPL/JAK2/STAT signaling. When added later (day 8), the compound induced a dose-dependent decrease (up to 10-fold) in proplatelet (PPT) formation. Gene profiling from MK revealed a silencing in the expression of DNA repair genes with a marked RAD51 decrease at protein level. DNA double-strand breaks were increased as attested by elevated γH2AX phosphorylation level. Moreover, ATM was phosphorylated leading to p53 stabilization and increased BAX and p21 expression. The use of a p53 shRNA rescued apoptosis, and only partially the defect in PPT formation. These results suggest that HDACi induces a thrombocytopenia by a p53-dependent mechanism along MK differentiation and a p53-dependent and -independent mechanism for PPT formation.

Phase II study of gemcitabine-dexamethasone with or without cisplatin in relapsed or refractory mantle cell lymphoma.

Single-agent gemcitabine has shown encouraging results in patients with mantle cell lymphoma (MCL). This phase II study further explored the potential of a gemcitabine-based regimen in patients with relapsed or refractory MCL. Patients <70 years old received the PDG regimen: gemcitabine (1000 mg/m(2), days 1 and 8), dexamethasone (40 mg/m(2), days 1-4), and cisplatin (100 mg/m(2), day 1). Patients >/=70 years of age received dexamethasone and gemcitabine only (DG regimen). Thirty patients (12 in the DG group, 18 in the PDG group) with a median age 66.5 years (range, 47-81) received a median of six cycles in both groups. The overall response rate was 36.4% [95% confidence interval (CI), 15.2% to 64.6%] with the DG regimen and 44.4% (95% CI 24.6% to 66.3%) with the PDG regimen. The median progression-free survival was 3 months (95% CI 0.0-7.9) in the DG group and 8.5 months (95% CI 4.8-12.2) in the PDG group. With a median follow-up of 38.8 months, 13 patients (including 11 given PDG) are still alive. DG was well tolerated, and thrombocytopenia was the most prevalent toxicity in patients receiving PDG. Both regimens deserve to be further investigated as a backbone for combination chemotherapy in patients with MCL.

A high proportion of donor CD4+ T cells expressing the lymph node-homing chemokine receptor CCR7 increases incidence and severity of acute graft-versus-host disease in patients undergoing allogeneic stem cell transplantation for hematological malignancy.

CC-chemokine receptor 7 (CCR7), a chemokine receptor required for transmigration into lymphoid organs, is only expressed by naive and central memory T cells. T cells with a capacity of homing into lymphoid organs can initiate acute graft-versus-host disease (GVHD) in mice and respond vigorously in vitro to alloantigens in humans, but their impact on clinical outcomes is unknown. We evaluated prospectively the distribution of naive, central memory and CCR7neg memory T-cell subsets in 39 bone marrow and 23 granulocyte colony-stimulating factor-mobilized peripheral blood stem cell allografts and investigated their impact on patient outcomes. Ranges of the relative proportions of CCR7+ cells within CD4+ and CD8+ T-cell populations were broad, but did not differ between the two sources of allografts. By multivariate analysis, high percentage of donor-derived CD4+CCR7+ T cells (>73.5%) significantly correlated with incidence, earliness of onset and severity of acute GVHD, conferring the highest adjusted hazard ratio (HR=3.9; 95% confidence interval 1.4-10.8; P=0.008) without interfering in other clinical events, especially chronic GVHD and relapse. Determination of the percentage of CD4+CCR7+ T cells in the graft provides a predictive indicator of acute GVHD. Partial depletion of this subset may reduce the risk of acute GVHD while preserving immunotherapeutic effects.

[Hodgkin's disease and Epstein-Barr virus]. / Maladie de Hodgkin et virus d'Epstein-Barr: physiopathologie et perspectives thérapeutiques.

Epstein-Barr virus (EBV) seems to use B cell normal differentiation pathways to establish and maintain a persistent infection. This process is effectively controlled by the immune system through the action of EBV-specific T lymphocytes, so that the lifelong chronic infection is free of complications for most individuals. EBV is, however, associated with several malignancies. 30-50% of Hodgkin's lymphomas (HL) are EBV-associated. In EBV-positive HL, the virus is localized to the tumor cells and is clonal. HL is characterized by a type II form of latency with viral antigen expression limited to EBNA1, LMP1 and LMP2. EBV-positive HL is more frequent in childhood, in older patients and in mixed cellularity cases. EBV association may represent a poor prognosis factor in the elderly. The true contribution of EBV to the pathogenesis of HL remains uncertain, but EBV may provide to abnormal B cells survival signals protecting them from apoptosis. Finally, whatever the role that EBV plays in tumor development, the presence of viral antigens in the malignant cells may represent a target for new therapeutic strategies.

Donor lymphocyte infusion to treat relapse after allogeneic bone marrow transplantation for myelodysplastic syndrome.

Donor lymphocyte infusion has become established as a salvage therapy for patients with hematological disorders relapsing after allogeneic bone marrow transplantation (BMT). The role of donor lymphocyte infusion for patients with myelodysplastic syndrome (MDS) remains to be established. Between July 1993 and October 2001, 14 patients with MDS relapsing after allogeneic BMT received DLI as salvage therapy. At the time of BMT, one patient had RA, nine had RAEB, of whom three were in CR after induction-type chemotherapy, two had RAEB-T, one had CMML and one had AML. Donors were HLA-matched siblings (n=12), HLA-matched other relative (n=1) and unrelated (n=1). At the time of relapse, the median marrow blast count was 9%. The median CD3+ cell dose administered was 6.3 x 10(7)/kg. With a median follow-up of 49 months, six patients were alive, of whom two were in CR after DLI alone and remained disease-free, two were in CR after a second BMT and two had active disease. Eight patients died of disease progression. Although DLI alone seems to be effective in a small number of patients with MDS, other treatment strategies, including prior debulking chemotherapy, deserve investigation.

Expression of a human endogenous retrovirus, HERV-K, in the blood cells of leukemia patients.

Human endogenous retroviral sequences (HERVs) are believed to be possible pathogenic agents in carcinogenesis. HERV-K is the most biologically active form, since members of this family have intact open reading frames for the gag, pol or env genes. Antibody response against HERV-K peptides has been reported in leukemia patients, suggesting a possible overexpression of this sequence in leukemic cells. Using real-time quantitative RT-PCR (TaqMan), we found that in six of the eight leukemia samples we collected, transcriptional activity of HERV-K10-like gag gene was 5- to 10-fold higher than in normal peripheral blood mononuclear cells (PBMCs) or mononuclear cells from cord blood. The overexpression was marked enough to be detected by Northern blot. In addition, there was no significant variation of HERV-K expression in normal PBMCs after exposure to different factors (PHA, gamma irradiation, 5-azacytidine) that potentially modulate HERV expression. This suggests that HERV-K relative overexpression in leukemia samples might be specifically associated with tumor development. The origin of these transcriptional variations is therefore worth being investigated further.