Apoptosis of multiple myeloma cells induced by agonist monoclonal antibody against human CD28

The potentials of immune checkpoints for the treatment of blood malignancies

Immune checkpoints are the regulators of the immune system, which include stimulatory and inhibitory receptors. They play substantial roles in the maintenance of immune system homeostasis and the prevention of autoimmunity and cancer. In the current review, immune checkpoints roles are surveyed in the initiation, progression, and treatment of blood malignancies. The significant roles of immune checkpoints are discussed as clinical markers in the diagnosis and prognosis of a plethora of blood malignancies and also as potential targets for the treatment of these malignancies. It could be concluded that the regulation of immune checkpoints in various blood cancers can be employed as a novel strategy to obtain effective results in leukemia treatment and introduce immune checkpoint inhibitors as sufficient weapons against blood cancers in the future.

Tumor cell-associated immune checkpoint molecules - Drivers of malignancy and stemness

Inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor cells in different tumor types. It was thought that the main function of tumor cell-associated immune checkpoint molecules would be the modulation (down- or upregulation) of antitumor immune responses. In recent years, however, it has become clear that the expression of immune checkpoint molecules on tumor cells has important consequences on the biology of the tumor cells themselves. In particular, a causal relationship between the expression of these molecules and the acquisition of malignant traits has been demonstrated. Thus, immune checkpoint molecules have been shown to promote the epithelial-mesenchymal transition of tumor cells, the acquisition of tumor-initiating potential and resistance to apoptosis and antitumor drugs, as well as the propensity to disseminate and metastasize. Herein, we review this evidence, with a main focus on PD-L1, the most intensively investigated tumor cell-associated immune checkpoint molecule and for which most information is available. Then, we discuss more concisely other tumor cell-associated immune checkpoint molecules that have also been shown to induce the acquisition of malignant traits, such as PD-1, B7-H3, B7-H4, Tim-3, CD70, CD28, CD137, CD40 and CD47. Open questions in this field as well as some therapeutic approaches that can be derived from this knowledge, are also addressed.

Monoclonal antibody therapy in multiple myeloma

The therapeutic landscape of multiple myeloma (MM) has evolved spectacularly over the past decade with the discovery and validation of proteasome inhibitors and immunomodulatory agents as highly active agents, both in front-line therapy as well as in the relapse and maintenance settings. Although previous attempts to apply available monoclonal antibodies (Mabs) to the treatment of patients with MM has until recently been disappointing, novel targets specifically explored in the context of MM have recently lead to the first approvals of Mabs for the treatment of patients with MM. We have performed a literature search to identify preclinical targeting of MM, including in vitro and in vivo models using monoclonal antibodies, as well as clinical trials of monoclonal antibodies in patients with MM. Sources used were peer-reviewed publications, congress abstracts and on-line clinical trials data (such as clinicaltrials.gov). Several targets have been evaluated in preclinical models and a growing number of agents are being evaluated in clinical trials, as single agents or in combination and under various antibody formats. Two agents, targeting for the first time CD38 and SLAMF7, respectively, have recently been approved for the treatment of patients with MM. The recent approval of these two antibodies is expected to have a strong impact on treatment modalities and outcome in patients with MM, including both transplant eligible and elderly patients.

The prognostic impact of multiparameter flow cytometry immunophenotyping and cytogenetic aberrancies in patients with multiple myeloma

OBJECTIVES

The aim of this study was to evaluate the prognostic impact of immunophenotyping in patients with multiple myeloma (MM), as well as other markers of disease, such as serum hyaluronan and cytogenetic aberrancies.

METHODS

We have prospectively analyzed the prognostic impact of antigenic markers, assessed by multiparametric flow cytometry (MFC), in a series of newly diagnosed MM patients (n = 79).

RESULTS AND DISCUSSION

Our results show that the expression of CD44, CD45, and CD28 and the absence of CD117 were associated with a significantly shorter progression free-survival (PFS). Clinical characteristics were collected; Cytogenetic aberrancies were assessed in 40 patients. Multivariate survival analyses identified that the CD117(-), CD28(+), CD45(+), and the percentage of bone marrow plasma cells by MFC are survival predictor, along with the International Staging System stage. Interestingly, the CD117(-) patients were associated with chromosomal aberrancies, including del (17p), +1q21, and IgH translocations.

CONCLUSION

The incorporation of multiparameter flow cytometry immunophenotyping into the routine diagnostic evaluation of MM patients can help to identify patients at a high risk of progression.

Generation and characterization of two novel monoclonal antibodies produced against human TLT-2 molecule

Trem-like transcript 2 (TLT-2), one of the TREM family members, which is expressed on B cells, T cells, and macrophages, plays a critical role in immune response mechanism. In this study, two novel mouse anti-human TLT-2 monoclonal antibodies (MAbs) were prepared using hybridoma technology and their immunological characteristics were determined. The results showed that the two MAbs (clones 10F5 and 8C10) were both IgG1 (κ) and bound specifically to human TLT-2. Furthermore, 10F5 and 8C10 seemed to recognize a different site (epitope) of TLT-2 by competition assay. MAb 10F5 was proven in Western blot analysis to specifically bind to denatured TLT-2 protein while both MAbs were proven in dot blot analyses and immunofluorescence to specifically bind to natural TLT-2 protein. In addition, crosslinking of TLT-2 with MAb 8C10 markedly blocked TLT-2 positive signal and T cell proliferation. Taken together, these two monoclonal antibodies might be of great value as tools for further exploration of the expression and function of TLT-2.

The CD28/B7 pathway: a novel regulator of plasma cell function

The CD28/B7 pathway is pivotal for the activation, optimal function, and regulation of T cell function. While the CD28 receptor and its ligands B7.1/B7.2 are also expressed on plasma cells, little is known of the role of the CD28/B7 pathway in plasma cell function. In this chapter we discuss the recent studies that have examined the role of CD28 expression on plasma cell function. Both stimulatory and inhibitory effects of CD28 on plasma cells have been reported. Based on our findings we propose that under homeostatic conditions the CD28/B7 interaction mediates regulation of plasma cell function whereas during inflammation this pathway can be perturbed to ramp up Ab production from existing plasma cells.

CD28-B7 interaction modulates short- and long-lived plasma cell function

The interaction of CD28, which is constitutively expressed on T cells, with B7.1/B7.2 expressed on APCs is critical for T cell activation. CD28 is also expressed on murine and human plasma cells but its function on these cells remains unclear. There are two types of plasma cells: short-lived ones that appear in the secondary lymphoid tissue shortly after Ag exposure, and long-lived plasma cells that mainly reside in the bone marrow. We demonstrate that CD28-deficient murine short- and long-lived plasma cells produce significantly higher levels of Abs than do their wild-type counterparts. This was owing to both increased frequencies of plasma cells as well as increased Ab production per plasma cell. Plasma cells also express the ligand for CD28, B7.1, and B7.2. Surprisingly, deficiency of B7.1 and B7.2 in B cells also led to higher Ab levels, analogous to Cd28(-/-) plasma cells. Collectively, our results suggest that the CD28-B7 interaction operates as a key modulator of plasma cell function.

Generation and characterization of four novel monoclonal antibodies against human programmed death-1 molecule

Programmed death-1 (PD-1, CD279), an inhibitory co-stimulatory molecule of the CD28 superfamily, plays a critical role in immune response. In this report, four novel mouse anti-human PD-1 monoclonal antibodies (MAbs) were prepared using hybridoma technology and immunological characteristics of the MAbs were determined. The results showed that all the MAbs (clones 9H1, 4B9, 8F5, and 1F8) were IgG1(kappa) and bound specifically to human PD-1. By mutual competition, we found that the antibodies recognized three different epitopes of PD-1 antigen and 9H1 MAb could block both PD-1/PD-L1 and PD-1/PD-L2 interaction. Cross-linking of PD-1 with MAb 9H1 markedly blocked PD-1 negative signal and promoted T cell proliferation. In addition, 4B9 and 9H1 MAbs were suitable for indirect ELISA detection. Thus, the MAbs against human PD-1 with high specificity and different activity would be useful for the further study of this molecule.

The negative co-signaling molecule b7-h4 is expressed by human bone marrow-derived mesenchymal stem cells and mediates its T-cell modulatory activity

Though experimental evidence shows that human bone marrow-derived mesenchymal stem cells (hBMSCs) are able to suppress T-cell activation and proliferation, the precise mechanisms are still not completely understood. Here, we investigated the role of the negative costimulatory molecule B7-H4 in the immunosuppressive effect of hBMSCs on T-cell activation. We showed that B7-H4 expresses abundantly on hBMSCs assessed by reverse transcription, immunofluorescence staining, and flow cytometric analysis. Further studies demonstrated that B7-H4 expressed on hBMSCs inhibits T-cell activation and proliferation via induction of cell cycle arrest and inhibition of NF-kappaB nuclear translocation. Blocking B7-H4 would decrease the secretion of transforming growth factor-beta1 (TGF-beta1) in the supernatant of activated T cells co-cultured with hBMSCs. Addition of neutralizing antibodies against B7-H4 significantly attenuated the inhibitory effects of hBMSCs on T-cells. Thus, our study established the novel role of B7-H4 molecule in the suppressive effect of hBMSCs on T-cell activation and proliferation. Taken together, these results highlight the complex role of hBMSCs in regulating the immune response, asserting the possibility of their therapeutic application in transplantation, the treatment of graft-versus-host disease (GVHD), and autoimmune diseases.

Cloning, purification and bioactivity assay of human CD28 single-chain antibody in Escherichia coli

Engineered single chain antibodies have become a powerful source of immunotherapy against a wide range of diseases. Here, we present the generation of human CD28 single-chain antibody gene (CD28-ScFv), which contained variable fragments of heavy chain and light chain (VH and VL) of the anti-CD28 antibody, and a linking peptide (Gly4Ser)3 inserted in the middle of VH and VL. The fused gene CD28-ScFv was successfully expressed in BL21 (DE3) cells and confirmed by western blotting assay. The molecular weight of CD28-ScFv was 43 kDa and the major fraction was expressed as an insoluble body. By dissolving the insoluble bodies, renaturing in vitro and purifying with a Ni-NTA affinity column, highly purified expression products of CD28-ScFv were obtained. This product could recognize and bind to CD28+ positive T cells. The proliferation capacity of peripheral blood T cells was increased by purified CD28-ScFv. In this study, we improved orthodox renaturing techniques by combining the dilution renaturation with phase gradient dialysis. With this new method, highly purified CD28-ScFv products were developed and biological activity of the products was similar to that of the mouse monoclonal anti-human CD28 antibody.

Prognostic Value of Immunophenotyping in Multiple Myeloma: A Study by the PETHEMA/GEM Cooperative Study Groups on Patients Uniformly Treated With High-Dose Therapy

Purpose

To analyze the prognostic impact of immunophenotyping in patients with multiple myeloma (MM).

Patients and Methods

We have prospectively analyzed the prognostic impact of antigenic markers, assessed by multiparametric flow cytometry, in a series of 685 newly diagnosed MM patients that were uniformly treated according to the GEM 2000 protocol.

Results

Our results show that expression of both CD19 and CD28 as well as the absence of CD117 were associated with a significantly shorter progression free-survival (PFS) and overall survival (OS). Interestingly, the CD28 expression correlated with t(14;16) and del(17p), while CD117-negative patients were associated with t(4;14) and del(13q). Simultaneous assessment of CD28 and CD117 antigens allowed stratification of patients with MM into three risk categories: poor risk (CD28 positive CD117 negative), intermediate (either both markers negative or both positive), and good risk (CD28 negative CD117 positive), with PFS rates of 30, 37, and 45 months, respectively (P = .01), and OS rates of 45, 68, and not reached, respectively (P = .0001).

Conclusion

To the best of our knowledge, this is the first prospective analysis in which the prognostic impact of a relatively high number of antigenic markers has been simultaneously analyzed in a large series of uniformly treated patients, showing that the expression of several antigens (particularly CD28 and CD117) on bone marrow plasma cells from patients with MM can help to identify patients at high risk of progression.

CD28-mediated regulation of multiple myeloma cell proliferation and survival

Although interactions with bone marrow stromal cells are essential for multiple myeloma (MM) cell survival, the specific molecular and cellular elements involved are largely unknown, due in large part to the complexity of the bone marrow microenvironment itself. The T-cell costimulatory receptor CD28 is also expressed on normal and malignant plasma cells, and CD28 expression in MM correlates significantly with poor prognosis and disease progression. In contrast to T cells, activation and function of CD28 in myeloma cells is largely undefined. We have found that direct activation of myeloma cell CD28 by anti-CD28 mAb alone induces activation of PI3K and NFkappaB, suppresses MM cell proliferation, and protects against serum starvation and dexamethasone (dex)-induced cell death. Coculture with dendritic cells (DCs) expressing the CD28 ligands CD80 and CD86 also elicits CD28-mediated effects on MM survival and proliferation, and DCs appear to preferentially localize within myeloma infiltrates in primary patient samples. Our findings suggest a previously undescribed myeloma/DC cell-cell interaction involving CD28 that may play an important role in myeloma cell survival within the bone marrow stroma. These data also point to CD28 as a potential therapeutic target in the treatment of MM.

Immunostimulatory monoclonal antibodies for cancer therapy

Increasing immune responses with immunostimulatory monoclonal antibodies (mAbs) directed to immune-receptor molecules is a new and exciting strategy in cancer therapy. This expanding class of agents functions on crucial receptors, either antagonizing those that suppress immune responses or activating others that amplify immune responses. Complications such as autoimmunity and systemic inflammation are problematic side effects associated with these agents. However, promising synergy has been observed in preclinical models using combinations of immunostimulatory antibodies and other immunotherapy strategies or conventional cancer therapies. Importantly, mAbs of this type have now entered clinical trials with encouraging initial results.