Thalidomide, lenalidomide and bortezomib in the management of newly diagnosed multiple myeloma

Proteasome Subunits Differentially Control Myeloma Cell Viability and Proteasome Inhibitor Sensitivity

We generated eight multiple myeloma cell lines resistant to bortezomib; five acquired PSMB5 mutations. In 1,500 patients such mutations were rare clinically. To better understand disruption of proteasomes on multiple myeloma viability and drug sensitivity, we systematically deleted the major proteasome catalytic subunits. Multiple myeloma cells without PSMB5 were viable. Drug-resistant, PSMB5-mutated cell lines were resensitized to bortezomib by PSMB5 deletion, implying PSMB5 mutation is activating in its drug resistance function. In contrast, PSMB6 knockout was lethal to multiple myeloma cell lines. Depleting PSMB6 prevented splicing of the major catalytic subunits PSMB5, PSMB7, PSMB8, and PSMB10; however, PSMB6 engineered without splicing function or catalytic activity, also restored viability, inferring the contribution of PSMB6 to proteasome structure to be more important than functional activity. Supporting this, bortezomib sensitivity was restored in drug-resistant multiple myeloma cell lines by low level expression of mutated PSMB6 lacking splicing function. Loss of PSMB8 and PSMB9 was neither lethal nor restored bortezomib sensitivity. Significant codependency of PSMB5, PSMB6, and PSMB7 expression was observed. We demonstrated elevated levels of PSMB6 and 7, but not 8 and 9, in some, but not all, serial patient samples exposed to proteasome inhibitors. In summary, we show PSMB6 and PSMB7, but not PSMB5, to be essential for multiple myeloma cell survival, this dependency is structural and that upregulation or activating mutation of PSMB5, 6, and 7 confers proteasome inhibitor resistance, while depletion confers sensitivity. IMPLICATIONS: These findings support modulation of PSMB5, PSMB6, or PSMB7 expression as a new therapeutic strategy.

Therapeutic status and the prospect of CRISPR/Cas9 gene editing in multiple myeloma

In recent years, CRISPR/Cas9, a novel gene-editing technology, has shown considerable potential in the design of novel research methods and future options for treating multiple myeloma (MM). The use of CRISPR/Cas9 promises faster and more accurate identification and validation of target genes. In this review, we summarize the current research status of the application of CRISPR technology in MM, especially in detecting the expression of MM gene, exploring the mechanism of drug action, screening for drug-resistant genes, developing immunotherapy and screening for new drug targets. Given the tremendous progress that has been made, we believe that CRISPR/Cas9 possesses great potential in MM-related clinical practice.

Conventional Cytogenetics and Interphase Fluorescence In Situ Hybridization Results in Multiple Myeloma: A Turkey Laboratory Analysis of 381 Cases

Multiple myeloma (MM) is an uncontrolled proliferation of plasma cells and these cells play an important role in the immune system. In this research, we retrospectively analyzed cytogenetic abnormalities in 381 patients with MM. Conventional cytogenetic analysis was successful in 354 patients (92.9%). Chromosomal abnormalities were detected in 31.9% (113/354) and 45.8% (116/253) of patients screened with conventional cytogenetics and FISH, respectively. Of 113 patients with chromosomal abnormalities, 31 patients (27.4%) had hyperdiploid and 26 of 31 patients with hyperdiploidy had both numerical and structural anomalies. On the other hand, non-hyperdiploidy was observed in 62 patients (54.8%). The most common gains of chromosomes were 15, 9, 19 followed by 3, 5, 11, and 21. Whole chromosome losses were also frequent involving Y, 13 and 22 chromosomes. In our patients, 1q gain was determined in a total of 25 patients (22%), including 7 structural abnormalities and 19 unbalanced translocations causing complete or partial duplication of the long arm of chromosome 1. Although the breakpoints were different, t(1;5) balanced translocation and unbalanced translocations of t(1;2), t(1;3), t(1;7), t(1;16) and t(1;19) were observed twice. The most common structural abnormality was the deletion of the short arm of chromosome 13 (13q) or monosomy of chromosome 13 (-13) (24.1%, 61/253) in patients evaluated by FISH. Deletion involving chromosome 17p (del 17p) or monosomy of chromosome 17 (-17) were found in 31 (12.3%) patients. Translocations involving IgH regions were as follows: t(11;14)(q13;q32.33) in 22 (8.7%), t(4;14)(p16.3;q32.33) in 22 (8.7%) and t(14;16)(q32.33;q23.1) in 2 (0.8%) patients. In addition, t(14;17)(q32;q21) translocation was detected in a multiple myeloma patient for the first time in this study. There are a limited number of large study groups including both cytogenetic and FISH findings in MM patients. As the number of these studies increases, it is thought that new cytogenetic data can be guiding especially in clinical risk determination.

CRISPR Genome-Wide Screening Identifies Dependence on the Proteasome Subunit PSMC6 for Bortezomib Sensitivity in Multiple Myeloma

Bortezomib is highly effective in the treatment of multiple myeloma; however, emergent drug resistance is common. Consequently, we employed CRISPR targeting 19,052 human genes to identify unbiased targets that contribute to bortezomib resistance. Specifically, we engineered an RPMI8226 multiple myeloma cell line to express Cas9 infected by lentiviral vector CRISPR library and cultured derived cells in doses of bortezomib lethal to parental cells. Sequencing was performed on surviving cells to identify inactivated genes responsible for drug resistance. From two independent whole-genome screens, we selected 31 candidate genes and constructed a second CRISPR sgRNA library, specifically targeting each of these 31 genes with four sgRNAs. After secondary screening for bortezomib resistance, the top 20 "resistance" genes were selected for individual validation. Of these 20 targets, the proteasome regulatory subunit PSMC6 was the only gene validated to reproducibly confer bortezomib resistance. We confirmed that inhibition of chymotrypsin-like proteasome activity by bortezomib was significantly reduced in cells lacking PSMC6. We individually investigated other members of the PSMC group (PSMC1 to 5) and found that deficiency in each of those subunits also imparts bortezomib resistance. We found 36 mutations in 19S proteasome subunits out of 895 patients in the IA10 release of the CoMMpass study (https://themmrf.org). Our findings demonstrate that the PSMC6 subunit is the most prominent target required for bortezomib sensitivity in multiple myeloma cells and should be examined in drug-refractory populations. Mol Cancer Ther; 16(12); 2862-70. ©2017 AACR.

In search of the optimal platform for Post-Allogeneic SCT immunotherapy in relapsed multiple myeloma: a systematic review

Allogeneic stem cell transplantation (allo-SCT) has the potential to induce sustained remissions in patients with multiple myeloma (MM). Currently, allo-SCT is primarily performed in high-risk MM patients, most often in the setting of early relapse after first-line therapy with autologous SCT. However, the implementation of allo-SCT for MM is jeopardized by high treatment-related mortality (TRM) rates as well as high relapse rates. In this systematic review, we aimed to identify a safe allo-SCT strategy that has optimal 1-year results regarding mortality, relapse and severe GvHD, creating opportunities for post-transplantation strategies to maintain remissions in the high-risk group of relapsed MM patients. Eleven studies were included. Median PFS ranged from 5.2 to 36.8 months and OS was 13.0 to 63.0 months. The relapse related mortality at 1 year varied between 0 and 50% and TRM between 8 and 40%. Lowest GvHD incidences were reported for conditioning regimens with T-cell depletion using ATG or graft CD34+ selection. Similar strategies could lay the foundation for a post-transplant immune platform, this should be further evaluated in prospective clinical trials.

Siltuximab (CNTO 328) with lenalidomide, bortezomib and dexamethasone in newly-diagnosed, previously untreated multiple myeloma: an open-label phase I trial

The safety and efficacy of siltuximab (CNTO 328) was tested in combination with lenalidomide, bortezomib and dexamethasone (RVD) in patients with newly-diagnosed, previously untreated symptomatic multiple myeloma. Fourteen patients were enrolled in the study, eleven of whom qualified to receive therapy. A majority of patients (81.8%) completed the minimal number or more of the four required cycles, while two patients completed only three cycles. The maximum tolerated dose (MTD) of siltuximab with RVD was dose level −1 (siltuximab: 8.3 mg/kg; bortezomib: 1.3 mg/m²; lenalidomide: 25 mg; dexamethasone: 20 mg). Serious adverse events were grade 3 pneumonia and grade 4 thrombocytopenia, and no deaths occurred during the study or with follow-up (median follow-up 28.1 months). An overall response rate, after 3–4 cycles of therapy, of 90.9% (95% confidence interval (CI): 58.7%, 99.8%) (9.1% complete response (95% CI: 0.2%, 41.3%), 45.5% very good partial response (95% CI: 16.7%, 76.6%) and 36.4% partial response (95% CI: 10.9%, 69.2%)) was seen. Two patients withdrew consent, and nine patients (81.8%) opted for autologous stem cell transplantation.

Cereblon binding molecules in multiple myeloma

Immunomodulation is an established treatment strategy in multiple myeloma with thalidomide and its derivatives lenalidomide and pomalidomide as its FDA approved representatives. Just recently the method of action of these cereblon binding molecules was deciphered and results from large phase 3 trials confirmed the backbone function of this drug family in various combination therapies. This review details the to-date knowledge concerning mechanism of IMiD action, clinical applications and plausible escape mechanisms in which cells may become resistant/refractory to cereblon binding molecule based treatment.

Current and future immunotherapeutic approaches to multiple myeloma therapy

SUMMARY 

Multiple myeloma (MM) is a hematologic malignancy associated with heterogeneous treatment and survival outcomes due in part to the ability of MM to evade and suppress the immune system. Research has focused on finding ways to modulate and enhance immunity while targeting the bone marrow microenvironment. Contemporary therapies include immunomodulatory drugs, proteasome inhibitors and autologous and allogeneic stem cell transplant and have improved outcomes for patients with MM. Future therapies, including monoclonal antibodies, chimeric antigen receptor cells and MM vaccines, show promise to further improved outcomes, particularly when used in combination with existing therapies. This review covers the mechanism of action of currently available and future therapies and explores ways in which treatment may be more specifically directed in the future.

Mechanisms of tumor escape from immune system: role of mesenchymal stromal cells

Tumor microenvironment represents the site where the tumor tries to survive and escape from immune system-mediated recognition. Indeed, to proliferate tumor cells can divert the immune response inducing the generation of myeloid derived suppressor cells and regulatory T cells which can limit the efficiency of effector antitumor lymphocytes in eliminating neoplastic cells. Many components of the tumor microenvironment can serve as a double sword for the tumor and the host. Several types of fibroblast-like cells, which herein we define mesenchymal stromal cells (MSC), secrete extracellular matrix components and surrounding the tumor mass can limit the expansion of the tumor. On the other hand, MSC can interfere with the immune recognition of tumor cells producing immunoregulatory cytokines as transforming growth factor (TGF)ß, releasing soluble ligands of the activating receptors expressed on cytolytic effector cells as decoy molecules, affecting the correct interaction among lymphocytes and tumor cells. MSC can also serve as target for the same anti-tumor effector lymphocytes or simply impede the interaction between these lymphocytes and neoplastic cells. Thus, several evidences point out the role of MSC, both in epithelial solid tumors and hematological malignancies, in regulating tumor cell growth and immune response. Herein, we review these evidences and suggest that MSC can be a suitable target for a more efficient anti-tumor therapy.

Interferon-γ-induced upregulation of immunoproteasome subunit assembly overcomes bortezomib resistance in human hematological cell lines

Background

Despite encouraging results with the proteasome inhibitor bortezomib in the treatment of hematologic malignancies, emergence of resistance can limit its efficacy, hence calling for novel strategies to overcome bortezomib-resistance. We previously showed that bortezomib-resistant human leukemia cell lines expressed significantly lower levels of immunoproteasome at the expense of constitutive proteasomes, which harbored point mutations in exon 2 of the PSMB5 gene encoding the β5 subunit. Here we investigated whether up-regulation of immunoproteasomes by exposure to interferon-γ restores sensitivity to bortezomib in myeloma and leukemia cell lines with acquired resistance to bortezomib.

Methods

RPMI-8226 myeloma, THP1 monocytic/macrophage and CCRF-CEM (T) parental cells and sub lines with acquired resistance to bortezomib were exposed to Interferon-γ for 24-48 h where after the effects on proteasome subunit expression and activity were measured, next to sensitivity measurements to proteasome inhibitors bortezomib, carfilzomib, and the immunoproteasome selective inhibitor ONX 0914. At last, siRNA knockdown experiments of β5i and β1i were performed to identify the contribution of these subunits to sensitivity to proteasome inhibition. Statistical significance of the differences were determined using the Mann-Whitney U test.

Results

Interferon-γ exposure markedly increased immunoproteasome subunit mRNA to a significantly higher level in bortezomib-resistant cells (up to 30-fold, 10-fold, and 6-fold, in β1i, β5i, and β2i, respectively) than in parental cells. These increases were paralleled by elevated immunoproteasome protein levels and catalytic activity, as well as HLA class-I. Moreover, interferon-γ exposure reinforced sensitization of bortezomib-resistant tumor cells to bortezomib and carfilzomib, but most prominently to ONX 0914, as confirmed by cell growth inhibition studies, proteasome inhibitor-induced apoptosis, activation of PARP cleavage and accumulation of polyubiquitinated proteins. This sensitization was abrogated by siRNA silencing of β5i but not by β1i silencing, prior to pulse exposure to interferon-γ.

Conclusion

Downregulation of β5i subunit expression is a major determinant in acquisition of bortezomib-resistance and enhancement of its proteasomal assembly after induction by interferon-γ facilitates restoration of sensitivity in bortezomib-resistant leukemia cells towards bortezomib and next generation (immuno) proteasome inhibitors.

Immunomodulation as a therapeutic strategy in the treatment of multiple myeloma

Growth and survival of multiple myeloma (MM) cells depend on intrinsic, cell-autonomous parameters, such as the genetic lesions harboured by the MM cells, as well as extracellular, cell-non-autonomous factors, including the interaction between MM cells and bone-marrow stromal cells and the suppression of the host's anticancer immune responses. Thalidomide and the immunomodulatory agents lenalidomide and pomalidomide have pleiotropic effects on MM cells and their microenvironment, including promotion of direct mechanisms of MM-cell apoptosis, as well as indirect mechanisms mediated by perturbation of cell adhesion, modulation of cytokine production, and inhibition of tumor-associated angiogenesis. The immunomodulatory properties of these agents are mediated by effects on T-cell proliferation and function, stimulation of natural killer cells, and inhibition of regulatory T cells. Thalidomide and lenalidomide have established roles in the treatment of patients with newly diagnosed MM and those with relapsed/refractory disease. Pomalidomide is currently being evaluated in clinical trials, and preliminary clinical data suggest that it is active in patients with MM that is refractory to lenalidomide and bortezomib treatment. This article provides an overview of the current and potential future roles of immunomodulation in the management of MM, and how improved anticancer immune responses may improve treatment outcomes.

Pomalidomide: a novel drug to treat relapsed and refractory multiple myeloma

Multiple myeloma remains an incurable disease despite the introduction of the immunomodulatory drugs (IMiDs) thalidomide and lenalidomide and the proteasome inhibitor bortezomib that have improved the outcome of patients with both newly diagnosed and relapsed/refractory disease. However, patients who relapse after treatment with these agents or are refractory to them represent an unmet need and highlight the necessity for the development of novel anti-myeloma agents. Pomalidomide is an IMiD, structurally related to thalidomide, with enhanced antiangiogenic, antineoplastic, and anti-inflammatory properties and exhibiting potent anti-myeloma activity in vitro and in vivo. Pomalidomide has shown remarkable activity in patients who were refractory to both bortezomib and lenalidomide in Phase II and III studies. This paper reviews the chemistry and mechanisms of action of pomalidomide as well as all the available data from clinical trials on pomalidomide use in patients with refractory/relapsed multiple myeloma.

Lenalidomide (Revlimid), bortezomib (Velcade) and dexamethasone for heavily pretreated relapsed or refractory multiple myeloma

The combination of lenalidomide, bortezomib and dexamethasone (RVD) has shown excellent efficacy in patients with relapsed or refractory multiple myeloma (RRMM). The aim of our study was to assess the efficacy and toxicity profile of RVD for patients with advanced RRMM. We retrospectively reviewed the records of all patients with RRMM treated with RVD between March 2009 and December 2011. Thirty patients received ≥ 1 full cycle of RVD. Primary endpoints were overall response rate (ORR), progression-free survival (PFS) and overall survival (OS). After a median of 5 cycles (1-16), a very good partial response (VGPR) was seen in 10%, partial response (PR) in 36.7% and stable disease (SD) in 13.3% (ORR of 46.7%). Disease progression occurred in 21 patients at a median of 3 months (range 1.41-4.59). Eight patients (26%) experienced grade 3/4 adverse events, including anemia, neutropenia, muscle weakness and pneumonia. No patient experienced worsening peripheral neuropathy. Although RVD has been previously shown to be effective in RRMM, the ORR and PFS we observed were affected by very advanced disease status and heavy prior exposure to novel agents. Nevertheless, six of these patients with RRMM experienced a benefit of ≥ 6 months, suggesting synergism of this immunomodulatory derivative/proteasome inhibitor combination and/or re-establishment of drug sensitivity by an emergent myeloma clone.

Patterns of relapse and progression in multiple myeloma patients after auto-SCT: implications for patients' monitoring after transplantation

Auto-SCT (ASCT) is widely used in first-line treatment of multiple myeloma (MM). However, most patients eventually relapse or have progression of disease (R/POD). Although precise knowledge of R/POD patterns would be important to generate evidence-based surveillance recommendations after ASCT, such data is limited in the literature, especially after introduction of the free light chain assay (FLCA). This retrospective study examined the patterns of R/POD after first-line ASCT in 273 patients, using established criteria. At the time of R/POD, only 2% of patients had no associated serological evidence of R/POD. A total of 85% had asymptomatic R/POD, first detected by serological testing, whereas 15% had symptomatic R/POD with aggressive disease, early R/POD and short survival, with poor cytogenetics and younger age identified as risk factors. Although occult skeletal lesions were found in 40% of asymptomatic patients tested following serological R/POD, yearly skeletal surveys and urine testing were poor at heralding R/POD. We found a consistent association between paraprotein types at diagnosis and R/POD, allowing informed recommendations for appropriate serological monitoring and propose a new needed criterion using FLCA for patients relapsing by FLC only. Our findings provide important evidence-based recommendations that strengthen current monitoring guidelines after first-line ASCT in MM.