Alemtuzumab induction of intracellular signaling and apoptosis in malignant B lymphocytes

Therapeutic Monoclonal Antibodies in Clinical Practice against Cancer

The importance of monoclonal antibodies in oncology has increased drastically following the discovery of Milstein and Kohler. Since the first approval of the monoclonal antibody, i.e. Rituximab in 1997 by the FDA, there was a decline in further applications but this number has significantly increased over the last three decades for various therapeutic applications due to the lesser side effects in comparison to the traditional chemotherapy methods. Presently, numerous monoclonal antibodies have been approved and many are in queue for approval as a strong therapeutic agent for treating hematologic malignancies and solid tumors. The main target checkpoints for the monoclonal antibodies against cancer cells include EGFR, VEGF, CD and tyrosine kinase which are overexpressed in malignant cells. Other immune checkpoints like CTLA-4, PD-1 and PD-1 receptors targeted by the recently developed antibodies increase the capability of the immune system in destroying the cancerous cells. Here, in this review, the mechanism of action, uses and target points of the approved mAbs against cancer have been summarized.

Cancer immunotherapy: dawn of the death of cancer?

Cancer is one of the proficient evaders of the immune system which claims millions of lives every year. Developing therapeutics against cancer is extremely challenging as cancer involves aberrations in self, most of which are not detected by the immune system. Conventional therapeutics like chemotherapy, radiotherapy are not only toxic but they significantly lower the quality of life. Immunotherapy, which gained momentum in the 20th century, is emerging as one of the alternatives to the conventional therapies and is relatively less harmful but more costly. This review explores the modern advances in an array of such therapies and try to compare them along with a limited analysis of concerns associated with them.

The immunological function of CD52 and its targeting in organ transplantation

INTRODUCTION

CD52 (Campath-1 antigen), a glycoprotein of 12 amino acids anchored to glycosylphosphatidylinositol, is widely expressed on the cell surface of immune cells, such as mature lymphocytes, natural killer cells (NK), eosinophils, neutrophils, monocytes/macrophages, and dendritic cells (DCs). The anti-CD52 mAb, alemtuzumab, was used widely in clinics for the treatment of patients such as organ transplantation. In the present manuscript, we will briefly summarize the immunological function of CD52 and discuss the application of anti-CD52 mAb in transplantation settings.

FINDINGS

We reviewed studies published until July 2016 to explore the role of CD52 in immune cell function and its implication in organ transplantation. We showed that ligation of cell surface CD52 molecules may offer costimulatory signals for T-cell activation and proliferation. However, soluble CD52 molecules will interact with the inhibitory sialic acid-binding immunoglobulin-like lectin 10 (Siglec10) to significantly inhibit T cell proliferation and activation. Although the physiological and pathological significances of CD52 molecules are still poorly understood, the anti-CD52 mAb, alemtuzumab, was used widely for the treatment of patients with chronic lymphocytic leukemia, autoimmune diseases as well as cell and organ transplantation in clinics.

CONCLUSION

Studies clearly showed that CD52 can modulate T-cell activation either by its intracellular signal pathways or by the interaction of soluble CD52 and Siglec-10 expressing on T cells. However, the regulatory functions of CD52 on other immune cell subpopulations in organ transplantation require to be studied in the near future.

Igf1 and Pacap rescue cerebellar granule neurons from apoptosis via a common transcriptional program

A shift of the delicate balance between apoptosis and survival-inducing signals determines the fate of neurons during the development of the central nervous system and its homeostasis throughout adulthood. Both pathways, promoting or protecting from apoptosis, trigger a transcriptional program. We conducted whole-genome expression profiling to decipher the transcriptional regulatory elements controlling the apoptotic/survival switch in cerebellar granule neurons following the induction of apoptosis by serum and potassium deprivation or their rescue by either insulin-like growth factor-1 (Igf1) or pituitary adenylyl cyclase-activating polypeptide (Pacap). Although depending on different upstream signaling pathways, the survival effects of Igf1 and Pacap converged into common transcriptional cascades, thus suggesting the existence of a general transcriptional program underlying neuronal survival.

Capture-stabilize approach for membrane protein SPR assays

Measuring the binding kinetics of antibodies to intact membrane proteins by surface plasmon resonance has been challenging largely because of the inherent difficulties in capturing membrane proteins on chip surfaces while retaining their native conformation. Here we describe a method in which His-tagged CXCR5, a GPCR, was purified and captured on a Biacore chip surface via the affinity tag. The captured receptor protein was then stabilized on the chip surface by limited cross-linking. The resulting chip surface retained ligand binding activity and was used for monoclonal antibody kinetics assays by a standard Biacore kinetics assay method with a simple low pH regeneration step. We demonstrate the advantages of this whole receptor assay when compared to available peptide-based binding assays. We further extended the application of the capture-stabilize approach to virus-like particles and demonstrated its utility analyzing antibodies against CD52, a GPI-anchored protein, in its native membrane environment. The results are the first demonstration of chemically stabilized chip surfaces for membrane protein SPR assays.

Monoclonal Antibodies in Cancer Therapy: Mechanisms, Successes and Limitations

Rituximab was the first chemotherapeutic monoclonal antibody (CmAb) approved for clinical use in cancer therapeutics in 1997 and has significantly improved the clinical outcomes in non-Hodgkin's lymphoma. Since then, numerous CmAbs have been developed and approved for the treatment of various haematologic and solid human cancers. In this review, the classification, efficacy and significantly reduced toxicity of CmAbs available for use in the United States of America are presented. Finally, the limitations of CmAbs and future considerations are explored.

Impact of alemtuzumab treatment on the survival and function of human regulatory T cells in vitro

Alemtuzumab is a humanized monoclonal antibody specific for the CD52 protein present at high levels on the surface of B and T lymphocytes. In clinical trials, alemtuzumab has shown a clinical benefit superior to that of interferon-β in relapsing-remitting multiple sclerosis patients. Treatment with alemtuzumab leads to the depletion of circulating lymphocytes followed by a repopulation process characterized by alterations in the number, proportions and properties of lymphocyte subsets. Of particular interest, an increase in the percentage of T cells with a regulatory phenotype (Treg cells) has been observed in multiple sclerosis patients after alemtuzumab. Since Treg cells play an important role in the control of autoimmune responses, the effect of alemtuzumab on Treg cells was further studied in vitro. Alemtuzumab effectively mediated complement-dependent cytolysis of human T lymphocytes and the remaining population was enriched in T cells with a regulatory phenotype. The alemtuzumab-exposed T cells displayed functional regulatory characteristics including anergy to stimulation with allogeneic dendritic cells and ability to suppress the allogeneic response of autologous T cells. Consistent with the observed increase in Treg cell frequency, the CD25(hi) T-cell population was necessary for the suppressive activity of alemtuzumab-exposed T cells. The mechanism of this suppression was found to be dependent on both cell-cell contact and interleukin-2 consumption. These findings suggest that an alemtuzumab-mediated increase in the proportion of Treg cells may play a role in promoting the long-term efficacy of alemtuzumab in patients with multiple sclerosis.

The role of chemotherapy in managing chronic lymphocytic leukemia: optimizing combinations with targeted therapy

For many years, alkylating agents were the standard treatment for chronic lymphocytic leukemia (CLL). The advent of purine analogs improved response rates, but not overall survival, and although the monoclonal antibody rituximab is generally active against B-cell malignancies, it has demonstrated limited benefits as monotherapy for the treatment of CLL. However, specific combinations of chemotherapy, antibodies and targeted therapies have demonstrated additive or synergistic activity in CLL cells and deliver substantial clinical benefits. A greater understanding of the actions of chemotherapies and targeted agents on cellular pathways will advance the development of rationally designed combinations corresponding to individual patients' disease profiles.

Rituximab inhibits Kv1.3 channels in human B lymphoma cells via activation of FcγRIIB receptors

Kv1.3 channels play an important role in modulating lymphocyte proliferation and apoptosis. We hypothesized that Kv1.3 channels in B lymphocytes might be regulated by rituximab, an antibody to CD20, a drug for treatments of B-cell lymphomas and autoimmune diseases. Using both whole-cell and cell-attached patch-clamp techniques, we found that rituximab inhibited Kv1.3 channels in Daudi human B lymphoma cells by promoting the channel inactivation at a concentration which was much greater than that required for activation of CD20. The effect of rituximab on Kv1.3 channels was abolished after selective blockade of FcγRIIB receptors with anti-FcγRIIB antibody. Western blot experiments showed that Daudi B cells expressed both Kv1.3 channel and the low affinity Fc receptor, FcγRIIB, which could be activated by the Fc region of rituximab. In contrast, normal lymphocytes expressed less Kv1.3 channels with faster inactivation. Confocal microscopy and flow cytometry data showed that rituximab induced apoptosis of Daudi B cells and that the effect was attenuated by blockade of FcγRIIB receptors and partially mimicked by inhibition of Kv1.3 channels. These results suggest that in addition to previously described complement-dependent cytotoxicity, rituximab also induces apoptosis of malignant B lymphocyte by stimulating FcγRIIB receptors and inhibiting Kv1.3 channels.