Humoral immunotherapy of multiple myeloma: perspectives and perplexities

Immunotherapy Strategies Against Multiple Myeloma

Multiple myeloma is a monoclonal B-cell malignancy characterized by an accumulation of malignant plasma cells in the bone marrow, the presence of a monoclonal protein in the serum and/or urine, decreased normal immunoglobulin levels, and lytic bone disease. Patients with multiple myeloma benefit from combination therapy including novel therapeutic agents followed by autologous stem cell transplantation prolonged maintenance therapy. However, multiple myeloma remains incurable; most patients with multiple myeloma will eventually become resistant to chemotherapy, and progression or relapse of the disease is inevitable. Immunotherapy represents a novel therapeutic approach with few adverse effects and good targeting capability that might be a powerful pool to allow long-term control of minimal residual disease. This article reviews the literature evaluating 4 major immunotherapeutic approaches for multiple myeloma including cellular immunotherapy, humoral immunotherapy, radio immunotherapy, and immunomodulation.

How to Think About Risk in Myeloma

An integral part of myeloma therapy is risk stratification of newly diagnosed patients. This method involves a combination of staging and genetic risk assessment. Although survival has dramatically improved for patients with genetically defined, standard-risk myeloma, those with high-risk disease remain a therapeutic challenge. Current treatment approaches might include the use of combination therapy for induction and maintenance. Future approaches are expected to involve drugs that are "risk agnostic," such as monoclonal antibodies and immunotherapy.

Development of Novel Immunotherapies for Multiple Myeloma

Multiple myeloma (MM) is a disorder of terminally differentiated plasma cells characterized by clonal expansion in the bone marrow (BM). It is the second-most common hematologic malignancy. Despite significant advances in therapeutic strategies, MM remains a predominantly incurable disease emphasizing the need for the development of new treatment regimens. Immunotherapy is a promising treatment modality to circumvent challenges in the management of MM. Many novel immunotherapy strategies, such as adoptive cell therapy and monoclonal antibodies, are currently under investigation in clinical trials, with some already demonstrating a positive impact on patient survival. In this review, we will summarize the current standards of care and discuss major new approaches in immunotherapy for MM.

Novel agents and new therapeutic approaches for treatment of multiple myeloma

This review summarizes the therapeutic strategies and the drugs actually in development for the management of myeloma patients. Multiple myeloma is caused by the expansion of monoclonal plasma cells and secretion of M-protein (immunoglobulins, Bence Jones protein and free light chains). Multiple myeloma still remains an incurable disease with a high incidence rate in the elderly, despite the introduction of several new therapeutic agents (bortezomib, lenalidomide and thalidomide) which have changed its natural history. The high heterogeneity of this disease leads to large differences in clinical responses to treatments. Thus, the choice of the best treatment is a difficult issue. However, the introduction of new drugs has made it possible to achieve high response rates and good quality responses with long-term disease control. Interactions between tumor cells and their bone marrow microenvironment play a pivotal role in the development, maintenance, and progression of myeloma, inducing also drug resistance. These knowledges have improved treatment options, leading to the approval of new drugs which not only target the malignant cell itself, but also its microenvironment. These agents are in preclinical/early clinical evaluation and they appear to further improve disease control, but their use is still not approved outside of clinical trials.

Nuclear factor-κB is involved in the protocadherin-10-mediated pro-apoptotic effect in multiple myeloma

The gene encoding protocadherin-10 (PCDH10), a member of the cadherin superfamily, has been recently identified as a tumor suppressor gene (TSG). PCDH10 plays important roles in the apoptosis of tumor cells in some cancer types. However, the exact role of PCDH10 in multiple myeloma (MM) is largely unknown. Increasing evidence has suggested that the activation of nuclear factor-κB (NF-κB) is crucial for apoptosis in myeloma cells. In this study, we investigated the pro-apoptotic effect of PCDH10 on myeloma cells and whether this effect may involve inhibition of the NF-κB pathway. We report here, for the first time to the best of our knowledge, that PCDH10 markedly induces apoptosis of myeloma cells, accompanied by an increase in activated caspase-3 and poly-ADP‑ribose polymerase (PARP) levels, and inhibited expression of anti‑apoptotic proteins. We also demonstrate that PCDH10 inhibits the activation of NF-κB, by inhibiting the expression of the inhibitor of nuclear factor-κB (IκB) kinase subunits (IKKs) and the phosphorylation of IκBα. Moreover, the constitutive NF-κB DNA-binding activity and the expression of the NF-κB‑regulated proteins cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF) and intercellular adhesion molecule 1 (ICAM-1) were inhibited by PCDH10 in MM cells. These results suggest that PCDH10 induces myeloma cell apoptosis, probably by inhibiting the NF-κB pathway.

Immunotherapy strategies for multiple myeloma: the present and the future

Growing knowledge of the complexities of the immune system have led to a better understanding of how it can be harnessed for the purpose of anticancer therapy. Moreover, recent success with immunotherapies for solid tumors, combined with novel therapeutic strategies against myeloma, heighten excitement at the prospect of improving clinical outcomes for myeloma by improving antitumor immunity. Increased understanding of myeloma tumor-associated antigens, availability of more potent vaccines, expanded immune-modulating therapies, development of agents that block immune-suppressive pathways, increased sophistication of adoptive cell therapy techniques and capitalization upon standard autologous transplant are all important standalone or combination strategies that might ultimately improve prognosis of patients with multiple myeloma.

Monoclonal antibody-based immunotherapy for multiple myeloma

Multiple myeloma (MM) is a life-threatening hematological malignancy. High-dose chemotherapy followed by autologous stem cell transplantation is a relatively effective treatment, but disease recurrence remains a major obstacle. Allogeneic transplantation may result in durable responses and cure due to antitumor immunity mediated by donor lymphocytes. However, morbidity and mortality related to graft-versus-host disease remain a challenge. Recent advances in understanding the interaction between the immune system of the patient and the malignant cells are influencing the design of clinically more efficient study protocols for MM. This review will focus on MM antigens and their specific antibodies. These monoclonal antibodies are an attractive therapeutic tool for MM humoral immunotherapy, with most promising preclinical results.

Novel strategies for immunotherapy in multiple myeloma: previous experience and future directions

Multiple myeloma (MM) is a life-threatening haematological malignancy for which standard therapy is inadequate. Autologous stem cell transplantation is a relatively effective treatment, but residual malignant sites may cause relapse. Allogeneic transplantation may result in durable responses due to antitumour immunity mediated by donor lymphocytes. However, morbidity and mortality related to graft-versus-host disease remain a challenge. Recent advances in understanding the interaction between the immune system of the patient and the malignant cells are influencing the design of clinically more efficient study protocols for MM. Cellular immunotherapy using specific antigen-presenting cells (APCs), to overcome aspects of immune incompetence in MM patients, has received great attention, and numerous clinical trials have evaluated the potential for dendritic cell (DC) vaccines as a novel immunotherapeutic approach. This paper will summarize the data investigating aspects of immunity concerning MM, immunotherapy for patients with MM, and strategies, on the way, to target the plasma cell more selectively. We also include the MM antigens and their specific antibodies that are of potential use for MM humoral immunotherapy, because they have demonstrated the most promising preclinical results.

P-selectin glycoprotein ligand regulates the interaction of multiple myeloma cells with the bone marrow microenvironment

Interactions between multiple myeloma (MM) cells and the BM microenvironment play a critical role in the pathogenesis of MM and in the development of drug resistance by MM cells. Selectins are involved in extravasation and homing of leukocytes to target organs. In the present study, we focused on adhesion dynamics that involve P-selectin glycoprotein ligand-1 (PSGL-1) on MM cells and its interaction with selectins in the BM microenvironment. We show that PSGL-1 is highly expressed on MM cells and regulates the adhesion and homing of MM cells to cells in the BM microenvironment in vitro and in vivo. This interaction involves both endothelial cells and BM stromal cells. Using loss-of-function studies and the small-molecule pan-selectin inhibitor GMI-1070, we show that PSGL-1 regulates the activation of integrins and downstream signaling. We also document that this interaction regulates MM-cell proliferation in coculture with BM microenvironmental cells and the development of drug resistance. Furthermore, inhibiting this interaction with GMI-1070 enhances the sensitization of MM cells to bortezomib in vitro and in vivo. These data highlight the critical contribution of PSGL-1 to the regulation of growth, dissemination, and drug resistance in MM in the context of the BM microenvironment.

Monoclonal antibodies in the treatment of multiple myeloma

Despite recent advances in treatment that have significantly improved overall survival, multiple myeloma (MM) remains incurable. Although rituximab, the first monoclonal antibody (MAb) evaluated in MM treatment, provided only very limited benefit, research is ongoing into a number of other MAbs directed against a variety of MM-related target antigens. Given the inherent immune dysfunction associated with MM, newer strategies that may enhance immune function in conjunction with antibodies may also provide a more fruitful clinical approach. Potential MAb targets in MM include growth factors and their receptors, other signalling molecules, and antigens expressed exclusively or predominantly on MM cells. MAb therapy involves a range of mechanisms, including antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, interference with receptor-ligand interactions, and MAb conjugation to radioisotopes or toxins. The antigens currently targeted in MM therapy are discussed, along with the development status of the corresponding MAb therapeutics. Elotuzumab, an anti-CS1 MAb, has recently achieved clinically meaningful responses when combined with lenalidomide or bortezomib in patients with relapsed and relapsed/refractory MM. Other MAbs are also showing early promise. More ongoing clinical research is required to identify optimal combination regimens and biomarkers that may help predict response to specific MAb-based combinations.