Expression of cereblon protein assessed by immunohistochemicalstaining in myeloma cells is associated with superior response of thalidomide- and lenalidomide-based treatment, but not bortezomib-based treatment, in patients with multiple myeloma

The emerging role of targeted protein degradation to treat and study cancer

The evolution of cancer treatment has provided increasingly targeted strategies both in the upfront and relapsed disease settings. Small-molecule inhibitors and immunotherapy have risen to prominence with chimeric antigen receptor T-cells, checkpoint inhibitors, kinase inhibitors, and monoclonal antibody therapies being deployed across a range of solid organ and haematological malignancies. However, novel approaches are required to target transcription factors and oncogenic fusion proteins that are central to cancer biology and have generally eluded successful drug development. Thalidomide analogues causing protein degradation have been a cornerstone of treatment in multiple myeloma, but a lack of in-depth mechanistic understanding initially limited progress in the field. When the protein cereblon (CRBN) was found to mediate thalidomide analogues' action and CRBN's neo-targets were identified, existing and novel drug development accelerated, with applications outside multiple myeloma, including non-Hodgkin's lymphoma, myelodysplastic syndrome, and acute leukaemias. Critically, transcription factors were the first canonical targets described. In addition to broadening the application of protein-degrading drugs, resistance mechanisms are being overcome and targeted protein degradation is widening the scope of druggable proteins against which existing approaches have been ineffective. Examples of targeted protein degraders include molecular glues and proteolysis targeting chimeras (PROTACs): heterobifunctional molecules that bind to proteins of interest and cause proximity-induced ubiquitination and proteasomal degradation via a linked E3 ligase. Twenty years since their inception, PROTACs have begun progressing through clinical trials, with early success in targeting the oestrogen receptor and androgen receptor in breast and prostate cancer respectively. This review explores important developments in targeted protein degradation to both treat and study cancer. It also considers the potential advantages and challenges in the translational aspects of developing new treatments. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Targeting the ubiquitin pathway in lymphoid malignancies

Ubiquitination and related cellular processes control a variety of aspects in human cell biology, and defects in these processes contribute to multiple illnesses. In recent decades, our knowledge about the pathological role of ubiquitination in lymphoid cancers and therapeutic strategies to target the modified ubiquitination system has evolved tremendously. Here we review the altered signalling mechanisms mediated by the aberrant expression of cancer-associated E2s/E3s and deubiquitinating enzymes (DUBs), which result in the hyperactivation of oncoproteins or the frequently allied downregulation of tumour suppressors. We discuss recent highlights pertaining to the several different therapeutic interventions which are currently being evaluated to effectively block abnormal ubiquitin-proteasome pathway and the use of heterobifunctional molecules which recruit the ubiquitination system to degrade or stabilize non-cognate substrates. This review aids in comprehension of ubiquitination aberrance in lymphoid cancers and current targeting strategies and elicits further investigations to deeply understand the link between cellular ubiquitination and lymphoid pathogenesis as well as to ameliorate corresponding treatment interventions.

ETV4-Dependent Transcriptional Plasticity Maintains MYC Expression and Results in IMiD Resistance in Multiple Myeloma

Immunomodulatory drugs (IMiD) are a backbone therapy for multiple myeloma (MM). Despite their efficacy, most patients develop resistance, and the mechanisms are not fully defined. Here, we show that IMiD responses are directed by IMiD-dependent degradation of IKZF1 and IKZF3 that bind to enhancers necessary to sustain the expression of MYC and other myeloma oncogenes. IMiD treatment universally depleted chromatin-bound IKZF1, but eviction of P300 and BRD4 coactivators only occurred in IMiD-sensitive cells. IKZF1-bound enhancers overlapped other transcription factor binding motifs, including ETV4. Chromatin immunoprecipitation sequencing showed that ETV4 bound to the same enhancers as IKZF1, and ETV4 CRISPR/Cas9-mediated ablation resulted in sensitization of IMiD-resistant MM. ETV4 expression is associated with IMiD resistance in cell lines, poor prognosis in patients, and is upregulated at relapse. These data indicate that ETV4 alleviates IKZF1 and IKZF3 dependency in MM by maintaining oncogenic enhancer activity and identify transcriptional plasticity as a previously unrecognized mechanism of IMiD resistance.

SIGNIFICANCE

We show that IKZF1-bound enhancers are critical for IMiD efficacy and that the factor ETV4 can bind the same enhancers and substitute for IKZF1 and mediate IMiD resistance by maintaining MYC and other oncogenes. These data implicate transcription factor redundancy as a previously unrecognized mode of IMiD resistance in MM. See related article by Welsh, Barwick, et al., p. 34. See related commentary by Yun and Cleveland, p. 5. This article is featured in Selected Articles from This Issue, p. 4.

Induced protein degradation for therapeutics: past, present, and future

The concept of induced protein degradation by small molecules has emerged as a promising therapeutic strategy that is particularly effective in targeting proteins previously considered "undruggable." Thalidomide analogs, employed in the treatment of multiple myeloma, stand as prime examples. These compounds serve as molecular glues, redirecting the CRBN E3 ubiquitin ligase to degrade myeloma-dependency factors, IKZF1 and IKZF3. The clinical success of thalidomide analogs demonstrates the therapeutic potential of induced protein degradation. Beyond molecular glue degraders, several additional modalities to trigger protein degradation have been developed and are currently under clinical evaluation. These include heterobifunctional degraders, polymerization-induced degradation, ligand-dependent degradation of nuclear hormone receptors, disruption of protein interactions, and various other strategies. In this Review, we will provide a concise overview of various degradation modalities, their clinical applications, and potential future directions in the field of protein degradation.

Thalidomide Attenuates Mast Cell Activation by Upregulating SHP-1 Signaling and Interfering with the Action of CRBN

Allergy is a chronic inflammatory disease, and its incidence has increased worldwide in recent years. Thalidomide, which was initially used as an anti-emetic drug but was withdrawn due to its teratogenic effects, is now used to treat blood cancers. Although the anti-inflammatory and immunomodulatory properties of thalidomide have been reported, little is known about its influence on the mast cell-mediated allergic reaction. In the present study, we aimed to evaluate the anti-allergic activity of thalidomide and the underlying mechanism using mouse bone marrow-derived mast cells (BMMCs) and passive cutaneous anaphylaxis (PCA) mouse models. Thalidomide markedly decreased the degranulation and release of lipid mediators and cytokines in IgE/Ag-stimulated BMMCs, with concurrent inhibition of FcεRI-mediated positive signaling pathways including Syk and activation of negative signaling pathways including AMP-activated protein kinase (AMPK) and SH2 tyrosine phosphatase-1 (SHP-1). The knockdown of AMPK or SHP-1 with specific siRNA diminished the inhibitory effects of thalidomide on BMMC activation. By contrast, the knockdown of cereblon (CRBN), which is the primary target protein of thalidomide, augmented the effects of thalidomide. Thalidomide reduced the interactions of CRBN with Syk and AMPK promoted by FcεRI crosslinking, thereby relieving the suppression of AMPK signaling and suppressing Syk signaling. Furthermore, oral thalidomide treatment suppressed the PCA reaction in mice. In conclusion, thalidomide suppresses FcεRI-mediated mast cell activation by activating the AMPK and SHP-1 pathways and antagonizing the action of CRBN, indicating that it is a potential anti-allergic agent.

Targeting cereblon in hematologic malignancies

The protein cereblon (CRBN) is a substrate receptor of the cullin 4-really interesting new gene (RING) E3 ubiquitin ligase complex CRL4^CRBN. Targeting CRBN mediates selective protein ubiquitination and subsequent degradation via the proteasome. This review describes novel thalidomide analogs, immunomodulatory drugs, also known as CRBN E3 ubiquitin ligase modulators or molecular glues (avadomide, iberdomide, CC-885, CC-90009, BTX-1188, CC-92480, CC-99282, CFT7455, and CC-91633), and CRBN-based proteolysis targeting chimeras (PROTACs) with increased efficacy and potent activity for application in hematologic malignancies. Both types of CRBN-binding drugs, molecular glues, and PROTACs stimulate the interaction between CRBN and its neosubstrates, recruiting target disease-promoting proteins and the E3 ubiquitin ligase CRL4^CRBN. Proteins that are traditionally difficult to target (transcription factors and oncoproteins) can be polyubiquitinated and degraded in this way. The competition of CRBN neosubstrates with endogenous CRBN-interacting proteins and the pharmacology and rational combination therapies of and mechanisms of resistance to CRL4^CRBN modulators or CRBN-based PROTACs are described.

Tumor and microenvironmental mechanisms of resistance to immunomodulatory drugs in multiple myeloma

Resistance to immunomodulatory drugs (IMiDs®) is a major cause of treatment failure, disease relapse and ultimately poorer outcomes in multiple myeloma (MM). In order to optimally deploy IMiDs and their newer derivates CRBN E3 ligase modulators (CELMoDs®) into future myeloma therapeutic regimens, it is imperative to understand the mechanisms behind the inevitable emergence of IMiD resistance. IMiDs bind and modulate Cereblon (CRBN), the substrate receptor of the CUL4CRBN E3 ubiquitin ligase, to target novel substrate proteins for ubiquitination and degradation. Most important of these are IKZF1 and IKZF3, key MM survival transcription factors which sustain the expression of myeloma oncogenes IRF4 and MYC. IMiDs directly target MM cell proliferation, but also stimulate T/NK cell activation by their CRBN-mediated effects, and therefore enhance anti-MM immunity. Thus, their benefits in myeloma are directed against tumor and immune microenvironment - and in considering the mechanisms by which IMiD resistance emerges, both these effects must be appraised. CRBN-dependent mechanisms of IMiD resistance, including CRBN genetic aberrations, CRBN protein loss and CRBN-substrate binding defects, are beginning to be understood. However, only a proportion of IMiD-resistant cases are related to CRBN and therefore additional mechanisms, which are currently less well described, need to be sought. These include resistance within the immune microenvironment. Here we review the existing evidence on both tumor and immune microenvironment mechanisms of resistance to IMiDs, pose important questions for future study, and consider how knowledge regarding resistance mechanism may be utilized to guide treatment decision making in the clinic.

Phase 2 study of oral thalidomide-cyclophosphamide-dexamethasone for recurrent/refractory adult Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a clonal histiocytic neoplasm with various clinical manifestations and heterogeneous prognoses. No standard therapy is available for recurrent/refractory LCH patients. This single-center, single-arm, phase 2 study enrolled 32 patients diagnosed with recurrent/refractory LCH. The TCD regimen (thalidomide 100 mg daily, cyclophosphamide 300 mg/m² Day 1, 8, 15, and dexamethasone 40 mg Day 1, 8, 15, 22 every 4 weeks) was administered for 12 cycles and thalidomide alone as maintenance for 12 months. The primary endpoint was event-free survival (EFS). Events were defined as progression during or after TCD therapy or death from any cause. After a median follow-up of 22 months (range 5-24 months), no patient died of all causes. The overall response rate was 87.5%, including 18 patients (56.3%) achieving complete remission and 10 patients (31.3%) as partial remission. The estimated 24-month EFS was 64.0%. Patients with risk organ involvement had similar EFS compared to patients without risk organ involvement (P = 0.38). The common toxicities of TCD regimen include grade 1-2 neutropenia (18.8%), grade 1-2 constipation (12.5%), grade 1-2 tiredness (9.4%) and grade 2 peripheral neuropathy (12.5%). Oral thalidomide, cyclophosphamide and dexamethasone are effective and safe regimen for recurrent/refractory LCH patients, particularly for patients with risk organ involvement.

Novel Molecular Mechanism of Lenalidomide in Myeloid Malignancies Independent of Deletion of Chromosome 5q

Lenalidomide as well as other immunomodulatory drugs (IMiDs) have achieved clinical efficacies in certain sub-types of hematologic malignancies, such as multiple myeloma, lower-risk myelodysplastic syndromes (MDS) with a single deletion of chromosome 5q (del(5q)) and others. Despite superior clinical response to lenalidomide in hematologic malignancies, relapse and resistance remains a problem in IMiD-based therapy. The last ten years have witnessed the discovery of novel molecular mechanism of IMiD-based anti-tumor therapy. IMiDs bind human cereblon (CRBN), the substrate receptor of the CRL4 E3 ubiquitin ligase complex. Binding of CRBN with IMiDs leads to degradation of the Ikaros family zinc finger proteins 1 and 3 (IKZF1 and IKZF3) and casein kinase 1 alpha. We have found that lenalidomide-mediated degradation of IKZF1 leads to activation of the G protein-coupled receptor 68 (GPR68)/calcium/calpain pro-apoptotic pathway and inhibition of the regulator of calcineurin 1 (RCAN1)/calcineurin pro-survival pathway in MDS and acute myeloid leukemia (AML). Calcineurin inhibitor Cyclosporin-A potentiates the anti-leukemia activity of lenalidomide in MDS/AML with or without del(5q). These findings broaden the therapeutic potential of IMiDs. This review summarizes novel molecular mechanism of lenalidomide in myeloid malignancies, especially without del(5q), in the hope to highlight novel therapeutic targets.

Cereblon pathway biomarkers and immune profiles in patients with myeloma receiving post-ASCT lenalidomide maintenance (LEOPARD)

LEOPARD was a single arm, phase II study of lenalidomide (LEN) and alternate day prednisolone maintenance in patients with newly diagnosed multiple myeloma (MM) following autologous stem cell transplantation (ASCT). Sixty patients were enrolled. Estimated median potential follow-up was 44 m, median PFS was 38.3 m, median OS was not reached (landmark 36 m OS: 71.4%). Correlative immunohistochemistry performed on pre-ASCT trephines demonstrated high MM tumor cereblon (total/cytoplasmic) was associated with superior OS (p = .045, p = .031, respectively), whereas high c-Myc was associated with inferior PFS (p = .04). Patients with high cereblon (total/nuclear) were more likely to improve depth of response, whereas patients with high c-Myc were less likely, suggesting alternative/more effective post-ASCT strategies for patients with high c-Myc need identification. Peripheral blood immune profiling (mass cytometry) informed a more sustained response to LEN maintenance, demonstrating enrichment of activated/cytotoxic NK cells and cytotoxic T cells in patients with durable responses, contrasting with enrichment of B-regs in early relapsers.

Prediction Model for Cereblon Expression in Bone Marrow Plasma Cells Based on Blood Markers in Multiple Myeloma Patients

Background

Cereblon (CRBN) is a direct target of immunomodulatory drugs (IMiDs) and is known to be sensitive and responsive to IMiD therapy. We evaluated CRBN expression in bone marrow plasma cells and analyzed whether CRBN expression was associated with multiple myeloma prognosis. Lastly, we developed a nomogram model for predicting high CRBN expression based on clinically significant blood markers.

Methods

We evaluated 143 multiple myeloma patients (internal dataset) who underwent bone marrow examinations. For evaluating the prognostic ability of the nomogram model, two external cohorts (235 patients in external dataset 1 and 156 patients in external dataset 2) were analyzed. The expression of CRBN in bone marrow aspirate samples was evaluated using immunohistochemistry. High CRBN expression was defined as the study-defined H-score ≥6.

Results

In the high CRBN group, the median progression-free survival (PFS) and overall survival (OS) of patients receiving the IMiD-based therapy and non-IMiD therapy were 29 and 10 months for PFS, and NR (not reached) and 54 months for OS, respectively. IMiD-based therapy was significantly associated with better PFS and OS outcomes. High CRBN expression was independently predicted by female sex, high serum free-light chain (FLC) ratio, higher serum M-protein level, and higher β2-microglobulin level. Based on these results, we constructed a new nomogram model to predict high CRBN expression and the effectiveness of IMiD therapy in multiple myeloma.

Conclusion

This nomogram could improve the prognostic evaluation of myeloma patients exhibiting high CRBN expression treated with IMiD therapy and might help provide personalized treatment strategies to clinicians.

Cancer therapies based on targeted protein degradation - lessons learned with lenalidomide

For decades, anticancer targeted therapies have been designed to inhibit kinases or other enzyme classes and have profoundly benefited many patients. However, novel approaches are required to target transcription factors, scaffolding proteins and other proteins central to cancer biology that typically lack catalytic activity and have remained mostly recalcitrant to drug development. The selective degradation of target proteins is an attractive approach to expand the druggable proteome, and the selective oestrogen receptor degrader fulvestrant served as an early example of this concept. Following a long and tragic history in the clinic, the immunomodulatory imide drug (IMiD) thalidomide was discovered to exert its therapeutic activity via a novel and unexpected mechanism of action: targeting proteins to an E3 ubiquitin ligase for subsequent proteasomal degradation. This discovery has paralleled and directly catalysed myriad breakthroughs in drug development, leading to the rapid maturation of generalizable chemical platforms for the targeted degradation of previously undruggable proteins. Decades of clinical experience have established front-line roles for thalidomide analogues, including lenalidomide and pomalidomide, in the treatment of haematological malignancies. With a new generation of 'degrader' drugs currently in development, this experience provides crucial insights into class-wide features of degraders, including a unique pharmacology, mechanisms of resistance and emerging therapeutic opportunities. Herein, we review these past experiences and discuss their application in the clinical development of novel degrader therapies.

The CRBN, CUL4A and DDB1 Expression Predicts the Response to Immunomodulatory Drugs and Survival of Multiple Myeloma Patients

Immunomodulatory drugs (IMiDs) are effective in the treatment of multiple myeloma (MM), myelodysplastic syndrome with deletion of chromosome 5q and other haematological malignancies. Recent studies showed that IMiDs bind to cereblon (CRBN), a substrate receptor of the CRL4–CRBN complex, to induce the ubiquitination and degradation of IKZF1 and IKZF3 in MM cells, contributing to their anti-myeloma activity. We aimed to determine whether the CRL4–CRBN complex proteins’ expression predicts the prognosis of MM patients treated with IMiDs. Here, we evaluated the expression of CRL4–CRBN complex proteins and their downstream targets with immunohistochemistry (IHC) staining in 130 bone marrow samples from MM patients treated with thalidomide or lenalidomide-based regimens. We found that the expression of CRBN and CUL4A was associated with the superior IMiD-based treatment response (p = 0.007 and p = 0.007, respectively). Moreover, the CUL4A expression was associated with improved PFS (HR = 0.66, 95% CI 0.44–0.99; p = 0.046) and DDB1 expression showed a negative impact on OS both in the univariate (HR = 2.75, 95% CI 1.65–4.61; p = 0.001) and the multivariate (HR 3.67; 95% CI 1.79–7.49; p < 0.001) analysis. Overall, our data suggest that the expression of DDB1, CUL4A and CRBN assessed by IHC predicts the clinical course of MM patients and identifies patients with a high probability of responding to IMiD-based therapy.

Cereblon Enhancer Methylation and IMiD Resistance in Multiple Myeloma

Cereblon is the direct binding target of the immunomodulatory drugs that are commonly used to treat Multiple Myeloma, the second most frequent hematologic malignancy. Patients respond well to initial IMiD treatment but virtually all develop drug resistance over time with the underlying mechanisms poorly understood. We identified a yet undescribed DNA hypermethylation in an active intronic CRBN enhancer. Differential hypermethylation in this region was found increased in healthy plasma cells, but more pronounced in IMiD refractory MM. Methylation significantly correlated with decreased CRBN expression levels. DNTMi in vitro experiments induced CRBN enhancer demethylation and sensitizing effects on Lenalidomide treatment were observed in two MM cell lines. Thus, we provide first evidence that aberrant CRBN DNA methylation is a novel mechanism of IMiD resistance in Multiple Myeloma and may predict IMiD response prior treatment.

Cereblon expression is a prognostic marker in newly diagnosed POEMS syndrome treated with lenalidomide plus dexamethasone

POEMS syndrome is a rare plasma cell disorder. Lenalidomide has recently emerged as a therapeutic option for POEMS syndrome. Cereblon has been identified as the direct target of lenalidomide, and high cereblon expression is associated with better response and outcome to lenalidomide therapy in multiple myeloma patients. Here, we analyzed the predictive value of cereblon, IKZF1, and IKZF3 in CD138⁺ selected plasma cells from forty-one newly diagnosed POEMS syndrome patients treated with lenalidomide in combination with dexamethasone at both gene and protein levels. We found that patients with high cereblon expression tended to achieve better hematologic response compared to those with low expression (p = 0.024 for gene expression; p = 0.01 for protein expression). Multivariate Cox regression analysis revealed high cereblon mRNA expression as an independent prognostic marker for longer progression-free survival (hazard ratio 0.542; 95% CI 0.337-0.871; p = 0.011). In conclusion, our results emphasized the role of cereblon mRNA expression as a unique biomarker for predicting the clinical response and outcome of lenalidomide-based therapy in newly diagnosed POEMS syndrome patients.

Emerging Therapeutic Strategies to Overcome Drug Resistance in Multiple Myeloma

Simple Summary

Multiple myeloma is a deadly blood cancer, but fortunately drug development has substantially prolonged the lifespan of patients to average more than a decade after diagnosis with optimal therapy. As a result, the population of patients living with multiple myeloma has grown considerably. Through its course, patients suffer repeated relapses for which they require new lines of treatment. Currently, the key drug classes for treatment are immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies. The goal of this review is to summarize the understanding of the problem of resistance to these drugs, which is ultimately responsible for patient fatality. In addition, we will focus on how new agents that are promising in clinical trials overcome resistance.

Abstract

Multiple myeloma is a malignant plasma cell neoplasm that remains incurable and is ultimately fatal when patients acquire multi-drug resistance. Thus, advancing our understanding of the mechanisms behind drug resistance in multi-relapsed patients is critical for developing better strategies to extend their lifespan. Here, we review the understanding of resistance to the three key drug classes approved for multiple myeloma treatment: immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies. We consider how the complex, heterogenous biology of multiple myeloma may influence the acquisition of drug resistance and reflect on the gaps in knowledge where additional research is needed to improve our treatment approaches. Fortunately, many agents are currently being evaluated preclinically and in clinical trials that have the potential to overcome or delay drug resistance, including next-generation immunomodulatory drugs and proteasome inhibitors, novel small molecule drugs, chimeric antigen receptor T cells, antibody-drug conjugates, and bispecific antibodies. For each class, we discuss the potential of these strategies to overcome resistance through modifying agents within each class or new classes without cross-resistance to currently available drugs.

The paradoxical pharmacological mechanisms of lenalidomide and bortezomib in the treatment of multiple myeloma

The combination of bortezomib (Velcade, PS-341) and lenalidomide (Revlimid) for the treatment of multiple myeloma was proved by USA Food and Drug Administration in 2006. Lenalidomide prevents the proliferation of multiple myeloma cells through binding to cereblon and promoting the ubiquitinational degradation of IKZF1 (Ikaros)/IKZF3 (Aiolos). However, the proteasome inhibitor bortezomib would inhibit the ubiquitinational degradation of IKZF1/IKZF3. How bortezomib could not block the antiproliferative effect of lenalidomide on multiple myeloma cells, which is the paradoxical pharmacological mechanisms in multiple myeloma. In this review, we summarized recent advances in molecular mechanisms underlying the combination of bortezomib and lenalidomide for the treatment multiple myeloma, discussed the paradoxical pharmacological mechanisms of lenalidomide and bortezomib in the treatment of multiple myeloma.

The impact of lenalidomide maintenance on second-line chemotherapy in transplant eligible patients with multiple myeloma

OBJECTIVES

To understand the impact of therapy sequencing on progression-free (PFS) and overall survival (OS) for the treatment of multiple myeloma (MM). The use of daily, low-dose, lenalidomide maintenance (LM) has raised concern for fostering resistance, preventing its use in the relapsed setting.

METHODS

We conducted a retrospective analysis of survival outcomes from the Canadian Myeloma Research Group Database. Patients were grouped based on receipt of LM after autologous stem cell transplant and receipt of lenalidomide in second-line therapy, 575 patients were included.

RESULTS

Patients treated with LM had statistically similar 2nd PFS when re-exposed to lenalidomide in second-line therapy compared to those receiving non-lenalidomide-containing regimens (10.2 vs 14.0 months, P =.53). This cohort also had the longest 2nd OS, 18 months longer than patients treated with LM who did not receive lenalidomide at relapse (55.3 vs 37 months, P =.004). Patients treated with LM also demonstrated deeper responses to second-line therapy than their non-LM counterparts.

CONCLUSION

Our data suggest that patients progressing on LM who receive lenalidomide-containing therapy at first relapse have comparable 2nd PFS and better 2nd OS compared to non-lenalidomide-containing second-line regimens. Identification of patients mostly likely to benefit from further lenalidomide-containing therapy is paramount.

The Impact of Beta-Catenin and glutathione-S-transferase Gene Polymorphisms on the Treatment Results and Survival of Multiple Myeloma Patients

Multiple myeloma (MM) is an incurable disease, however, novel therapeutic agents has significantly improved its prognosis. In this study we analyzed if polymorphisms in the genes of β-catenin and glutathione-S-transferase have affected the clinical course, treatment response and progression-free survival (PFS) of MM patients. Ninety-seven MM patients were involved who were administered immunomodulatory drug (Imid) or alkylating agent-based therapy. β-catenin (CTNNB1, rs4135385 A > G, rs4533622 A > C) and glutathione-S-transferase (GSTP1 105, GSTP1 114) gene polymorphisms were analyzed by Light SNiP assays. The distribution of CTNNB1 (rs4135385) AA, AG and GG genotypes were 48.4%, 47.4% and 4,1%, respectively. Patients with AA genotype were older than those who carried G allele (64.5 vs. 61.0 years of age, p < 0.05). Response to Imid-based therapies (p < 0.05) and PFS (p = 0.032) were significantly more favourable in the AA homozygous group. The other polymorphism (rs4533622) of β-catenin gene did not markedly influence these clinical parameters, although MM was diagnosed at significantly younger age in subjects with CC genotype compared to AG/AA combined genotypes (59.1 vs. 65.7 years, p = 0.015). When GSTP1 polymorphisms were investigated, no such significant associations were observed. Our results demonstrate that the polymorphism of β-catenin gene (rs4135385) may be an independent predictive factor in MM.

Mechanism of Action and Novel IMiD-Based Compounds and Combinations in Multiple Myeloma

Over the last 2 decades, thalidomide analogs have induced significant antimyeloma effects via immune-modulation, antiangiogenesis and antiproliferative effects. While the exact molecular mechanism of the targets or the mediators of thalidomide activity were not known, a seminal discovery of cereblon as a thalidomide-binding protein led to explaining the mechanistic basis of antimyeloma activity for this class of agents. Identification of the mechanisms of resistance for immunomodulatory agents (IMiDs), which will have significant clinical implications, remains poorly understood. Newer cereblon modulators with differential effects and improved increased efficacy in cell lines resistant to the current IMiDs are in development with encouraging preclinical data. In this review, we have summarized the mechanisms of action of IMiDs, clinical development, and potential mechanisms of resistance. We also describe novel IMiD-based combinations and the newer cereblon modulators as well.

Cereblon (CRBN) gene polymorphisms predict clinical response and progression-free survival in relapsed/refractory multiple myeloma patients treated with lenalidomide: a pharmacogenetic study from the IMMEnSE consortium

Cereblon (CRBN) is crucial for antiproliferative and immunomodulatory properties of immunomodulatory drugs. The objective of this study was to verify whether germline single nucleotide polymorphisms (SNPs) in the CRBN gene may influence response to lenalidomide in multiple myeloma (MM). Fourteen tagging SNPs covering the genetic variability in the CRBN gene region were genotyped in 167 Polish patients with refractory/relapsed MM treated with lenalidomide-based regimens. We found that carriers of minor alleles of two studied CRBN SNPs rs1714327G > C (OR = 0.26; 95% CI = 0.1-0.67; p = .0055, Bonferroni corrected p = .033) and rs1705814T > C (OR = 0.22; 95% CI = 0.07-0.65; p = .0063, Bonferroni corrected p = .037) were significantly associated with lower probability of achievement at least partial remission while treated with lenalidomide-based regimens, using the dominant inheritance model. Moreover, one of these SNPs, namely rs1705814T > C, was correlated with shorter progression-free survival (HR = 2.49; 95%CI = 1.31-4.74, p = .0054, Bonferroni corrected p = .033). It is suggested that selected germline CRBN allelic variants (rs1714327G > C and rs1705814T > C) affect lenalidomide efficacy in patients with relapsed/refractory MM.

Patterns of substrate affinity, competition, and degradation kinetics underlie biological activity of thalidomide analogs

Pharmacologic agents that modulate ubiquitin ligase activity to induce protein degradation are a major new class of therapeutic agents, active in a number of hematologic malignancies. However, we currently have a limited understanding of the determinants of activity of these agents and how resistance develops. We developed and used a novel quantitative, targeted mass spectrometry (MS) assay to determine the relative activities, kinetics, and cell-type specificity of thalidomide and 4 analogs, all but 1 of which are in clinical use or clinical trials for hematologic malignancies. Thalidomide analogs bind the CRL4CRBN ubiquitin ligase and induce degradation of particular proteins, but each of the molecules studied has distinct patterns of substrate specificity that likely underlie the clinical activity and toxicities of each drug. Our results demonstrate that the activity of molecules that induce protein degradation depends on the strength of ligase-substrate interaction in the presence of drug, the levels of the ubiquitin ligase, and the expression level of competing substrates. These findings highlight a novel mechanism of resistance to this class of drugs mediated by competition between substrates for access to a limiting pool of the ubiquitin ligase. We demonstrate that increased expression of a nonessential substrate can lead to decreased degradation of other substrates that are critical for antineoplastic activity of the drug, resulting in drug resistance. These studies provide general rules that govern drug-dependent substrate degradation and key differences between thalidomide analog activity in vitro and in vivo.

Identification of lenalidomide resistance pathways in myeloma and targeted resensitization using cereblon replacement, inhibition of STAT3 or targeting of IRF4

To understand immunomodulatory drug (IMiD) resistance in multiple myeloma (MM), we created isogenic human multiple myeloma cell lines (HMCLs) sensitive and resistant to lenalidomide, respectively. Four HMCLs were demonstrated to be resistant to all IMiDs including lenalidomide, pomalidomide, and CC-220, but not to Bortezomib. In three HMLCs (MM.1.SLenRes, KMS11LenRes and OPM2LenRes), CRBN abnormalities were found, including chromosomal deletion, point mutation, and low CRBN expression. The remaining HMCL, XG1LenRes, showed no changes in CRBN but exhibited CD147 upregulation and impaired IRF4 downregulation after lenalidomide treatment. Depletion of CD147 in XG1LenRes and three additional HMCLs had no significant impact on MM viability and lenalidomide response. Further analysis of XG1LenRes demonstrated increased IL6 expression and constitutive STAT3 activation. Inhibition of STAT3 with a selective compound (PB-1-102) re-sensitized XG1LenRes to lenalidomide. Since XG1LenRes harbors a truncated IRF4 that is not downregulated by lenalidomide, we targeted IRF4/MYC axis with a selective inhibitor of the bromodomain of CBP/EP300 (SGC-CBP30), which restored lenalidomide response in XG1LenRes. This strategy also appeared to be more broadly applicable as SGC-CBP30 could re-sensitize two resistant HMCLs with low but detectable CRBN expression to lenalidomide, suggesting that targeting CBP/E300 is a promising approach to restore IMiD sensitivity in MM with detectable CRBN expression.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

Cereblon gene expression and correlation with clinical outcomes in patients with relapsed/refractory multiple myeloma treated with pomalidomide: an analysis of STRATUS

We analyzed gene expression levels of CRBN, cMYC, IRF4, BLIMP1, and XBP1 in 224 patients with multiple myeloma treated with pomalidomide and low-dose dexamethasone in the STRATUS study (ClinicalTrials.gov: NCT01712789; EudraCT number: 2012-001888-78). Clinical responses were observed at all CRBN expression levels. A trend in progression-free survival (PFS; p = .038) and a potential trend in overall survival (OS; p = .059) favoring high CRBN expressers were observed; however, no notable difference in overall response rate (ORR) was observed. ORR (30%), median PFS (17.7 weeks), and median OS (52.3 weeks) in low-CRBN expressers were comparable to those in the STRATUS intent-to-treat population (ORR, 33%; median PFS, 20.0 weeks; median OS, 51.7 weeks). A trend in ORR (p = .050) favoring higher cMYC expressers was observed with no notable difference in PFS or OS. This analysis does not support exploring CRBN as a biomarker for selecting patients for pomalidomide therapy.

Polymorphisms in the promoter region of the CRBN gene as a predictive factor for the first-line CTD therapy in multiple myeloma patients

Cereblon is a primary molecular target for immunomodulatory drugs. The aim of this study was to evaluate the influence of selected clinical and molecular factors including single nucleotide polymorphisms (SNPs) in CRBN gene on the efficacy of first line CTD (cyclophosphamide, thalidomide, dexamethasone) chemotherapy in patients with multiple myeloma. Study group consisted of 68 patients. Analysis of CRBN gene SNPs (rs6768972, rs1672753) was performed using Real-Time PCR genotyping technique. Median progression free survival (PFS) was 15 months and overall survival (OS) 79 months. Factors associated with significantly shorter OS included ISS 3, kidney disease, weight loss, anemia, thrombocytopenia, hypoalbuminemia, elevated β2-microglobuline and CRP. The presence of t(4;14) was associated with significantly shorter PFS and OS. Both examined SNPs proved to be statistically significant, independent predictive factors of efficacy of the CTD chemotherapy. The presence of AA genotype (rs6768972) correlated with longer median PFS (18 vs 9 months; HR=0.49,95% CI: 0.26-0.91, p=0.0062). Conversely, in the carriers of CC genotype (rs1672753) significantly shorter median PFS was observed (4 vs 16 months; HR=3.93, 95% CI: 0.26-59.64, p=0.0321). In conclusion, SNPs of the CRBN gene may be useful in qualifying patients for treatment with regimens containing thalidomide.

Baicalein Inhibits Proliferation of Myeloma U266 Cells by Downregulating IKZF1 and IKZF3

BACKGROUND Baicalein can suppress the growth of multiple tumors, including multiple myeloma (MM), but the exact mechanisms remains elusive. Here, we investigated the exact mechanisms of the anti-myeloma activity of baicalein. MATERIAL AND METHODS Proliferation and rates of apoptosis of myeloma U266 cells exposed to baicalein were detected. Microarray, polymerase chain reaction (PCR) assay, and Western blot analysis were applied to evaluate the mRNA and protein levels of associated molecules. Survival analysis of IKZF1 and IKZF3 was conducted as well. RESULTS Baicalein suppressed the growth and stimulated apoptosis of myeloma U266 cells in a dose- and time-dependent way. Baicalein increased mRNA level of CRBN, and further studies suggested that baicalein downregulated IKZF1 and IKZF3 on a post-transcriptional level. Although the differences did not reach statistical significance, IKZF1 and IKZF3 were associated with poor overall survival. CONCLUSIONS Our results suggest that baicalein suppresses the growth and promotes apoptosis of myeloma U266 cells through downregulating IKZF1 and IKZF3. Baicalein increased the expression of CRBN, which might exert a reversion effect on resistance of IMiDs. MM patients in IKZF1 and IKZF3 low-expression groups had better overall survival than those in IKZF1 and IKZF3 high-expression groups. Thus, the present results indicate that baicalein might be a therapeutic choice for targeting IKZF1 and IKZF3.

Immunomodulatory Drugs Exert Anti-Leukemia Effects in Acute Myeloid Leukemia by Direct and Immunostimulatory Activities

Immunomodulatory drugs (IMiDs) are anticancer drugs with immunomodulatory, anti-angiogenesis, anti-proliferative, and pro-apoptotic properties. IMiDs are currently used for the treatment of multiple myeloma, myelodysplastic syndrome, and B-cell lymphoma; however, little is known about efficacy in acute myeloid leukemia (AML). We proposed in this study to investigate the relevance of IMiDs therapy for AML treatment. We evaluated the effect of IMiDs on primary AML blasts (n = 24), and the impact in natural killer (NK) cell-mediated immunosurveillance of AML. Using primary AML cells and an immunodeficient mouse leukemia xenograft model, we showed that IMiDs induce AML cell death in vitro and impair leukemia progression in vivo. In addition, treatment of AML blasts with IMiDs resulted in enhanced allogeneic NK cell anti-leukemia reactivity. Treatment by pomalidomide of AML blasts enhanced lysis, degranulation, and cytokine production by primary allogeneic NK cells. Furthermore, the treatment with lenalidomide of patients with myeloid malignancies resulted in NK cell phenotypic changes similar to those observed in vitro. IMiDs increased CD56 and decreased NKp30, NKp46, and KIR2D expression on NK cells. Finally, AML blasts treatment with IMiDs induced phenotypic alterations including downregulation of HLA-class I. The effect of pomalidomide was not correlated with cereblon expression and A/G polymorphism in AML cells. Our data revealed, a yet unobserved, dual effects on AML affecting both AML survival and their sensitivity to NK immunotherapy using IMiDs. Our study encourages continuing investigation for the use of IMiDs in AML, especially in combination with conventional therapy or immunotherapy strategies.

Soluble PD-L1: A biomarker to predict progression of autologous transplantation in patients with multiple myeloma

Autologous hematopoietic stem cell transplantation (AuHSCT) is standard in treating eligible multiple myeloma (MM) patients. However, the outcome after treatment is highly variable. We used ELISA to analyze the levels of soluble PD-L1 (suPD-L1) in bone marrow (BM) plasma from 61 patients with MM at 100 days after AuHSCT. Patients were classified into high (H) and normal-to-low (NL) groups depending on their suPD-L1 levels. Among patients who had a very good partial response (VGPR) or better after AuHSCT, those in the H-group had a shorter response period (RpSCT) as well as shorter overall survival (OS) than those in the NL-group. Multivariate analyses confirmed that a high suPD-L1 level and high-risk cytogenetic abnormalities are independent factors for RpSCT. Our data suggest that suPD-L1 in the BM plasma of MM patients who have VGPR or better after AuHSCT could be used as a biomarker to predict outcome.

A novel nano-immunoassay method for quantification of proteins from CD138-purified myeloma cells: biological and clinical utility

Protein analysis in bone marrow samples from patients with multiple myeloma has been limited by the low concentration of proteins obtained after CD138⁺ cell selection. A novel approach based on capillary nano-immunoassay could make it possible to quantify dozens of proteins from each myeloma sample in an automated manner. Here we present a method for the accurate and robust quantification of the expression of multiple proteins extracted from CD138-purified multiple myeloma samples frozen in RLT Plus buffer, which is commonly used for nucleic acid preservation and isolation. Additionally, the biological and clinical value of this analysis for a panel of 12 proteins essential to the pathogenesis of multiple myeloma was evaluated in 63 patients with newly diagnosed multiple myeloma. The analysis of the prognostic impact of CRBN/Cereblon and IKZF1/Ikaros mRNA/protein showed that only the protein levels were able to predict progression-free survival of patients; mRNA levels were not associated with prognosis. Interestingly, high levels of Cereblon and Ikaros proteins were associated with longer progression-free survival only in patients who received immunomodulatory drugs and not in those treated with other drugs. In conclusion, the capillary nano-immunoassay platform provides a novel opportunity for automated quantification of the expression of more than 20 proteins in CD138⁺ primary multiple myeloma samples.

Dual inhibition of DNMTs and EZH2 can overcome both intrinsic and acquired resistance of myeloma cells to IMiDs in a cereblon-independent manner

Thalidomide and its derivatives, lenalidomide and pomalidomide (also known as IMiDs), have significantly changed the treatment landscape of multiple myeloma, and the recent discovery of cereblon (CRBN) as their direct biological target has led to a deeper understanding of their complex mechanism of action. In an effort to comprehend the precise mechanisms behind the development of IMiD resistance and examine whether it is potentially reversible, we established lenalidomide‐resistant (‐LR) and pomalidomide‐resistant (‐PR) human myeloma cell lines from two IMiD‐sensitive cell lines, OPM2 and NCI‐H929, by continuous culture in the presence of lenalidomide or pomalidomide for 4–6 months, until acquirement of stable resistance. By assessing genome‐wide DNA methylation and chromatin accessibility in these cell lines, we found that acquired IMiD resistance is associated with an increase in genome‐wide DNA methylation and an even greater reduction in chromatin accessibility. Transcriptome analysis confirmed that resistant cell lines are mainly characterized by a reduction in gene expression, identifying SMAD3 as a commonly downregulated gene in IMiD‐resistant cell lines. Moreover, we show that these changes are potentially reversible, as combination of 5‐azacytidine and EPZ‐6438 not only restored the observed accessibility changes and the expression of SMAD3, but also resensitized the resistant cells to both lenalidomide and pomalidomide. Interestingly, the resensitization process was independent of CRBN. Our data suggest that simultaneous inhibition of DNA methyl transferases and EZH2 leads to an extensive epigenetic reprogramming which allows myeloma cells to (re)gain sensitivity to IMiDs.

Mouse Monoclonal Antibodies Generated from Full Length Human Cereblon: Detection of Cereblon Protein in Patients with Multiple Myeloma

Immunomodulatory drugs (IMiDs) are profoundly active compounds in the treatment of patients with multiple myeloma (MM). However, despite the fact that treatment with IMiDs has dramatically improved survival for patients with MM, the majority of MM patients develop IMiDs resistance over time. We have found that expression of functional cereblon is required for IMiDs' action. In addition, it has been reported that cells expressing high levels of cereblon are resistant to proteasome inhibitor, implying that patients with high levels of cereblon should be resistant to proteasome inhibitor. If the above conclusions are correct, cereblon could be considered as a biomarker to determine which standard regimens should be used to treat patients with MM. Unfortunately, the conclusions mentioned above have not been clinically confirmed. In order to confirm these conclusions, we have generated three highly specific mouse monoclonal antibodies (mAbs) against full-length human cereblon. These mAbs can be used to do western blot, immunoprecipitation and immunohistochemistry staining. In addition, their epitopes have been precisely determined and the peptides covering their epitopes completely blocked the antibody binding to cereblon in western blot analysis or in immunohistochemistry staining of MM patients' specimens.

Immunohistochemical expression of cereblon and MUM1 as potential predictive markers of response to lenalidomide in extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma)

Lenalidomide is an active agent for the treatment of MALT lymphoma. Recently, high expression levels of cereblon (CRBN) and MUM1 have been associated with better response rates in multiple myeloma treated with lenalidomide. However, there are no data on CRBN and MUM1 expression in MALT lymphoma. In the current study, we have systematically investigated a potential correlation of CRBN/MUM1 immunohistochemical expression and response to lenalidomide-based therapy in a series of 46 patients with MALT lymphoma treated at the Medical University Vienna 2009 to 2014. In total, 28% (13/46) of biopsy specimens derived from gastric tissues, while 72% (33/46) originated from extragastric MALT lymphoma. In terms of CRBN, 54% showed high expression (CRBN+, ≥50% positive cells); the remaining 46% were classified as low expression (CRBN-). In contrast to other reports, there was a non-significant trend towards worse response rates in CRBN+ (68% versus 86%, P = 0.161). Relapse rates (P = 0.592) and PFS (P = 0.306) did not differ between CRBN+/CRBN-, but all 3 patients progressing on lenalidomide were CRBN+ and both patients completely lacking CRBN expression responded to treatment. Concerning MUM1, 62% were MUM1-negative (MUM1-) and 38% positive (MUM1+). There was no difference in response to lenalidomide by MUM1-status (MUM1+ 71% versus MUM1- 79%, P = 0.546) and also relapse rates (P = 0.828) and PFS (P = 0.681) did not differ. Interestingly, a subgroup analysis of gastric lymphoma revealed a significantly better PFS for CRBN- and MUM1- patients, respectively (both P < 0.05). To conclude, there was no significant difference in response to lenalidomide between patients with low or high expression of CRBN/MUM1 in a general population of MALT lymphoma, and immunohistochemical CRBN/MUM1 assessment cannot be recommended in the clinical routine.

Cereblon: A Protein Crucial to the Multiple Functions of Immunomodulatory Drugs as well as Cell Metabolism and Disease Generation

It is well known that cereblon is a key protein in autosomal recessive nonsyndromic mental retardation. Studies have reported that it has an intermediary role in helping immunomodulatory drugs perform their immunomodulatory and tumoricidal effects. In addition, cereblon also regulates the expression, assembly, and activities of other special proteins related to cell proliferation and metabolism, resulting in the occurrence and development of metabolic diseases. This review details the multiple functions of cereblon and the underlying mechanisms. We also put forward some unsolved problems, including the intrinsic mechanism of cereblon function and the possible regulatory mechanisms of its expression.

A Dual Color Immunohistochemistry Assay for Measurement of Cereblon in Multiple Myeloma Patient Samples

Supplemental Digital Content is available in the text.

Clinical interest in the measurement of Cereblon (CRBN), the primary target of the IMiDs immunomodulatory drugs lenalidomide and pomalidomide, has been fueled by its essential requirement for antitumor or immunomodulatory activity of both drugs in multiple myeloma (MM). However, limited analyses of clinical samples for CRBN gene expression or protein levels have utilized unvalidated reagents and assays, raising uncertainty about the interpretation of these results. We previously described a highly specific rabbit monoclonal antibody CRBN65 against 65-76 AA of human Cereblon. Here we describe a validated dual color bright-field Cereblon/CD138 immunohistochemical (IHC) assay utilizing CRBN65 and a commercial mouse monoclonal CD138 antibody. Sensitivity and specificity of the assay was determined and assay precision was shown for both cytoplasmic and nuclear Cereblon in MM bone marrow samples with coefficient of variation values of 5% and 2%, respectively. The dual IHC assay was effective for detecting a continuous range of Cereblon levels in 22 MM patient bone marrow core biopsies and aspirate clots, as shown by average cytoplasmic H-scores ranging from 63 to 267 and nuclear H-scores ranging from 17 to 250. Interpathologist comparison of MM sample H-scores by 3 pathologists demonstrated good concordance (R²=0.73). This dual assay demonstrated superior Cereblon IHC measurement in MM samples compared with the single IHC assay using a published commercial rabbit polyclonal Cereblon antibody and could be used to explore the potential utility of Cereblon as a biomarker in the clinic.

IKAROS expression in distinct bone marrow cell populations as a candidate biomarker for outcome with lenalidomide-dexamethasone therapy in multiple myeloma

Immunomodulatory drugs (IMiDs) are a cornerstone in the treatment of multiple myeloma (MM), but specific markers to predict outcome are still missing. Recent work pointed to a prognostic role for IMiD target genes (e.g. CRBN). Moreover, indirect activity of IMiDs on immune cells correlated with outcome, raising the possibility that cell populations in the bone marrow (BM) microenvironment could serve as biomarkers. We therefore analysed gene expression levels of six IMiD target genes in whole BM samples of 44 myeloma patients treated with lenalidomide-dexamethasone. Expression of CRBN (R = 0.30, P = .05), IKZF1 (R = 0.31, P = .04), IRF4 (R = 0.38, P = .01), MCT-1 (R = 0.30, P = .05), and CD147 (R = 0.38, P = .01), but not IKZF3 (R = -0.15, P = .34), was significantly associated with response. Interestingly, IKZF1 expression was elevated in BM environmental cells and thus selected for further investigation by multicolor flow cytometry. High IKAROS protein levels in total BM mononuclear cells (median OS 83.4 vs. 32.2 months, P = .02), CD19⁺ B cells (median OS 71.1 vs. 32.2 months, P = .05), CD3⁺ CD8⁺ T cells (median OS 83.4 vs 19.0 months, P = .008) as well as monocytes (median OS 53.9 vs 18.0 months, P = .009) were associated with superior overall survival (OS). In contrast, IKAROS protein expression in MM cells was not predictive for OS. Our data therefore corroborate the central role of immune cells for the clinical activity of IMiDs and built the groundwork for prospective analysis of IKAROS protein levels in distinct cell populations as a potential biomarker for IMiD based therapies.

Cereblon and IRF4 Variants Affect Risk and Response to Treatment in Multiple Myeloma

Multiple myeloma (MM) is a plasma-cell malignancy derived from an early precursor of the B-cell lineage characterised by bone-marrow infiltration, lytic bone lesions, and the presence of a monoclonal protein in serum and/or urine. Interferon regulatory factor 4 (IRF4) is a critical transcriptional regulator in B-cell development and function that is required during immune response for lymphocyte activation and the generation of immunoglobulin-secreting plasma cells. Immunomodulatory drugs, derivatives of thalidomide, are commonly used in therapy against MM. They are known to target a protein called cereblon (CRBN); however, the exact mechanism remains unknown. The present study aimed to assess the association of two (rs12203592 and rs872071) polymorphisms within the IRF4 gene and two (rs711613 and rs1045433) in the CRBN gene with MM susceptibility, progression, and response to treatment. For this purpose, 144 MM patients and 126 healthy individuals were genotyped for the IRF4 and CRBN alleles. The presence of the IRF4 (rs872071) G allele was more frequently detected in patients than healthy individuals (OR 1.78; P = 0.034), and this relationship was especially pronounced in women (OR 2.83; P = 0.012). The CRBN (rs711613) A allele-carriers were better responders to the treatment (P = 0.012), in particular to thalidomide including therapy (P = 0.023). These results underline the prognostic significance of the IRF4 and CRBN polymorphisms in patients with MM.

The role and mechanism of CRL4 E3 ubiquitin ligase in cancer and its potential therapy implications

CRLs (Cullin-RING E3 ubiquitin ligases) are the largest E3 ligase family in eukaryotes, which ubiquitinate a wide range of substrates involved in cell cycle regulation, signal transduction, transcriptional regulation, DNA damage response, genomic integrity, tumor suppression and embryonic development. CRL4 E3 ubiquitin ligase, as one member of CRLs family, consists of a RING finger domain protein, cullin4 (CUL4) scaffold protein and DDB1–CUL4 associated substrate receptors. The CUL4 subfamily includes two members, CUL4A and CUL4B, which share extensively sequence identity and functional redundancy. Aberrant expression of CUL4 has been found in a majority of tumors. Given the significance of CUL4 in cancer, understanding its detailed aspects of pathogenesis of human malignancy would have significant value for the treatment of cancer. Here, the work provides an overview to address the role of CRL4 E3 ubiquitin ligase in cancer development and progression, and discuss the possible mechanisms of CRL4 ligase involving in many cellular processes associated with tumor. Finally, we discuss its potential value in cancer therapy.

Cereblon in health and disease

Cereblon (CRBN) is a substrate receptor of the E3 ubiquitin ligase complex that has been linked to autosomal recessive non-syndromic mental retardation. Several key findings suggest diverse roles of CRBN, including its regulation of the large-conductance calcium- and voltage-activated potassium (BKCa) channels, regulation of thalidomide-binding proteins, and mediation of lenalidomide treatment in multiple myeloma. Recent studies also indicate that CRBN is involved in energy metabolism and negatively regulates AMP-activated protein kinase signaling. Mice with genetic depletion of CRBN are resistant to various stress conditions including a high-fat diet, endoplasmic reticulum stress, ischemia/reperfusion injury, and alcohol-related liver damage. In this review, we discuss the various roles of CRBN in human health and disease and suggest avenues for further research to enhance our basic knowledge and clinical application of CRBN.

Modulation of cereblon levels by anti-myeloma agents

The use of thalidomide derivatives (IMIDs) has improved multiple myeloma prognosis, through an unknown mechanism of action. Recently one molecular target, the cereblon (CRBN) protein, has been identified. CRBN acts by binding to DDB1-CUL4-ROC1 forming a ubiquitin ligase multiprotein complex. We have generated antibodies to different regions of CRBN protein, and analyzed the biological consequences of augmenting or decreasing CRBN levels. CRBN was expressed in all the myeloma cell lines tested, independently of their sensitivity to IMIDs, and the CRBN-DDB1-CUL4 complex was efficiently formed. At the molecular level, long-term treatment with IMIDs induced a slight decrease in CRBN levels and a reduction in the CRBN-DDB1-CUL4 complex. Interestingly, treatment with other anti-myeloma drugs downregulated cellular contents of CRBN, and in a much faster fashion. These results suggest that CRBN is an important mediator of the cellular response to IMIDs, but also critical in the maintenance of cell viability and/or proliferation.

Prognostic indicators of lenalidomide for multiple myeloma: consensus and controversy

The long-term outcome of multiple myeloma (MM) has been greatly improved through new agents, one being lenalidomide (LEN). Based upon the findings of in vitro experiments, its mode of action against MM occurs through a combination of direct tumoricidal effects on myeloma cells, modulatory effects on tumor immunity and tumor microenvironment-regulatory effects. However, it has not been clearly defined whether the clinical response and long-term outcome of MM with LEN treatment truly reflect the mechanisms of action of LEN proposed by in vitro studies. To ascertain what is known and what remains to be elucidated with LEN, we review the current literature on the mode of action of LEN in association with myeloma pathophysiology, and discuss the prognostic indicators in the treatment of MM with LEN.

Clinical and pharmacodynamic analysis of pomalidomide dosing strategies in myeloma: impact of immune activation and cereblon targets

In preclinical studies, pomalidomide mediated both direct antitumor effects and immune activation by binding cereblon. However, the impact of drug-induced immune activation and cereblon/ikaros in antitumor effects of pomalidomide in vivo is unknown. Here we evaluated the clinical and pharmacodynamic effects of continuous or intermittent dosing strategies of pomalidomide/dexamethasone in lenalidomide-refractory myeloma in a randomized trial. Intermittent dosing led to greater tumor reduction at the cost of more frequent adverse events. Both cohorts experienced similar event-free and overall survival. Both regimens led to a distinct pattern but similar degree of mid-cycle immune activation, manifested as increased expression of cytokines and lytic genes in T and natural killer (NK) cells. Pomalidomide induced poly-functional T-cell activation, with increased proportion of coinhibitory receptor BTLA(+) T cells and Tim-3(+) NK cells. Baseline levels of ikaros and aiolos protein in tumor cells did not correlate with response or survival. Pomalidomide led to rapid decline in Ikaros in T and NK cells in vivo, and therapy-induced activation of CD8(+) T cells correlated with clinical response. These data demonstrate that pomalidomide leads to strong and rapid immunomodulatory effects involving both innate and adaptive immunity, even in heavily pretreated multiple myeloma, which correlates with clinical antitumor effects. This trial was registered at www.clinicaltrials.gov as #NCT01319422.