Clinical Translation in Multiple Myeloma: From Bench to Bedside

IGH cytogenetic abnormalities can be detected in multiple myeloma by imaging flow cytometry

AIMS

Cytogenetic abnormalities involving the IGH gene are seen in up to 55% of patients with multiple myeloma. Current testing is performed manually by fluorescence in situ hybridisation (FISH) on purified plasma cells. We aimed to assess whether an automated imaging flow cytometric method that uses immunophenotypic cell identification, and does not require cell isolation, can identify IGH abnormalities.

METHODS

Aspirated bone marrow from 10 patients with multiple myeloma were studied. Plasma cells were identified by CD38 and CD138 coexpression and assessed with FISH probes for numerical or structural abnormalities of IGH. Thousands of cells were acquired on an imaging flow cytometer and numerical data and digital images were analysed.

RESULTS

Up to 30 000 cells were acquired and IGH chromosomal abnormalities were detected in 5 of the 10 marrow samples. FISH signal patterns seen included fused IGH signals for IGH/FGFR3 and IGH/MYEOV, indicating t(4;14) and t(11;14), respectively. In addition, three IGH signals were identified, indicating trisomy 14 or translocation with an alternate chromosome. The lowest limit of detection of an IGH abnormality was in 0.05% of all cells.

CONCLUSIONS

This automated high-throughput immuno-flowFISH method was able to identify translocations and trisomy involving the IGH gene in plasma cells in multiple myeloma. Thousands of cells were analysed and without prior cell isolation. The inclusion of positive plasma cell identification based on immunophenotype led to a lowest detection level of 0.05% marrow cells. This imaging flow cytometric FISH method offers the prospect of increased precision of detection of critical genetic lesions involving IGH and other chromosomal defects in multiple myeloma.

Diagnosis of Plasma Cell Dyscrasias and Monitoring of Minimal Residual Disease by Multiparametric Flow Cytometry

Plasma cell dyscrasia (PCD) is a heterogeneous disease that has seen a tremendous change in outcomes due to improved therapies. Over the past few decades, multiparametric flow cytometry has played an important role in the detection and monitoring of PCDs. Flow cytometry is a high-sensitivity assay for early detection of minimal residual disease (MRD) that correlates well with progression-free survival and overall survival. Before flow cytometry can be effectively implemented in the clinical setting, sample preparation, panel configuration, analysis, and gating strategies must be optimized to ensure accurate results. Current consensus methods and reporting guidelines for MRD testing are discussed.

International Myeloma Working Group consensus criteria for response and minimal residual disease assessment in multiple myeloma

Treatment of multiple myeloma has substantially changed over the past decade with the introduction of several classes of new effective drugs that have greatly improved the rates and depth of response. Response criteria in multiple myeloma were developed to use serum and urine assessment of monoclonal proteins and bone marrow assessment (which is relatively insensitive). Given the high rates of complete response seen in patients with multiple myeloma with new treatment approaches, new response categories need to be defined that can identify responses that are deeper than those conventionally defined as complete response. Recent attempts have focused on the identification of residual tumour cells in the bone marrow using flow cytometry or gene sequencing. Furthermore, sensitive imaging techniques can be used to detect the presence of residual disease outside of the bone marrow. Combining these new methods, the International Myeloma Working Group has defined new response categories of minimal residual disease negativity, with or without imaging-based absence of extramedullary disease, to allow uniform reporting within and outside clinical trials. In this Review, we clarify several aspects of disease response assessment, along with endpoints for clinical trials, and highlight future directions for disease response assessments.

The Role of Minimal Residual Disease Testing in Myeloma Treatment Selection and Drug Development: Current Value and Future Applications

Treatment of myeloma has benefited from the introduction of more effective and better tolerated agents, improvements in supportive care, better understanding of disease biology, revision of diagnostic criteria, and new sensitive and specific tools for disease prognostication and management. Assessment of minimal residual disease (MRD) in response to therapy is one of these tools, as longer progression-free survival (PFS) is seen consistently among patients who have achieved MRD negativity. Current therapies lead to unprecedented frequency and depth of response, and next-generation flow and sequencing methods to measure MRD in bone marrow are in use and being developed with sensitivities in the range of 10^-5 to 10^-6 cells. These technologies may be combined with functional imaging to detect MRD outside of bone marrow. Moreover, immune profiling methods are being developed to better understand the immune environment in myeloma and response to immunomodulatory agents while methods for molecular profiling of myeloma cells and circulating DNA in blood are also emerging. With the continued development and standardization of these methodologies, MRD has high potential for use in gaining new drug approvals in myeloma. The FDA has outlined two pathways by which MRD could be qualified as a surrogate endpoint for clinical studies directed at obtaining accelerated approval for new myeloma drugs. Most importantly, better understanding of MRD should also contribute to better treatment monitoring. Potentially, MRD status could be used as a prognostic factor for making treatment decisions and for informing timing of therapeutic interventions. Clin Cancer Res; 23(15); 3980-93. ©2017 AACR.

MicroC(3): an ex vivo microfluidic cis-coculture assay to test chemosensitivity and resistance of patient multiple myeloma cells

Chemosensitivity and resistance assays (CSRAs) aim to direct therapies based upon ex vivo responses of patient tumor cells to chemotherapeutic drugs. However, successful CSRAs are yet to be developed. Here, we exposed primary CD138(+) multiple myeloma (MM) cells to bortezomib, a clinical proteasome inhibitor, in microfluidic-cis-coculture (MicroC(3)) incorporating the patient's own CD138(-) tumor-companion mononuclear cells to integrate some of the patients' own tumor microenvironment components in the CSRA design. Statistical clustering techniques segregated MicroC(3) responses into two groups which correctly identified all seventeen patients as either clinically responsive or non-responsive to bortezomib-containing therapies. In contrast, when the same patient MM samples were analyzed in the absence of the CD138(-) cells (monoculture), the tumor cell responses did not segregate into clinical response clusters. Thus, MicroC(3) identified bortezomib-therapy MM patient responses making it a viable CSRA candidate toward enabling personalized therapy.

SCFβ-TRCP regulates osteoclastogenesis via promoting CYLD ubiquitination

CYLD negatively regulates the NF-κB signaling pathway and osteoclast differentiation largely through antagonizing TNF receptor-associated factor (TRAF)-mediated K63-linkage polyubiquitination in osteoclast precursor cells. CYLD activity is controlled by IκB kinase (IKK), but the molecular mechanism(s) governing CYLD protein stability remains largely undefined. Here, we report that SCF^β-TRCP regulates the ubiquitination and degradation of CYLD, a process dependent on prior phosphorylation of CYLD at Ser432/Ser436 by IKK. Furthermore, depletion of β-TRCP induced CYLD accumulation and TRAF6 deubiquitination in osteoclast precursor cells, leading to suppression of RANKL-induced osteoclast differentiation. Therefore, these data pinpoint the IKK/β-TRCP/CYLD signaling pathway as an important modulator of osteoclastogenesis.

Early or delayed transplantation for multiple myeloma in the era of novel therapy: does one size fit all?

For the last 20 years, high-dose therapy with autologous stem cell transplantation (ASCT) for multiple myeloma has been considered a standard frontline treatment for younger patients with adequate organ function. With the introduction of novel agents, specifically thalidomide, bortezomib, and lenalidomide, the role of ASCT has changed in several ways. First, novel agents have been incorporated successfully as induction regimens, increasing the response rate before ASCT, and are now being used as part of both consolidation and maintenance with the goal of extending progression-free and overall survival. These approaches have shown considerable promise with significant improvements in outcome. Furthermore, the efficacy of novel therapeutics has also led to the investigation of these agents upfront without the immediate application of ASCT, and compelling preliminary results have been reported. Next-generation novel agents and the use of monoclonal antibodies have raised the possibility of not only successful salvage strategies to facilitate delayed transplantation for younger patients, but also the prospect of an nontransplantation approach achieving the same outcome. Moreover, this could be achieved without incurring acute toxicity or long-term complications that are inherent to high-dose alkylation, and melphalan exposure in particular. At present, the role of ASCT has therefore become an area of debate: should it be used upfront in all eligible patients, or should it be used as a salvage treatment at the time of progression for patients achieving a high quality of response with initial therapy? There is a clear need to derive a consensus that is useful for clinicians considering both protocol-directed and non-protocol-directed options for their patients. Participation in ongoing prospective randomized trials is considered vital. While preliminary randomized data from studies in Europe favor early ASCT with novel agents, differences in both agents and the combinations used, as well as limited information on overall survival and benefit for specific patient subsets, suggest that one size does not fit all. Specifically, the optimal approach to treatment of younger patients eligible for ASCT remains a key area for further research. A rigid approach to its use outside of a clinical study is difficult to justify and participation in prospective studies should be a priority.

Early or delayed transplantation for multiple myeloma in the era of novel therapy: does one size fit all?

For the last 20 years, high-dose therapy with autologous stem cell transplantation (ASCT) for multiple myeloma has been considered a standard frontline treatment for younger patients with adequate organ function. With the introduction of novel agents, specifically thalidomide, bortezomib, and lenalidomide, the role of ASCT has changed in several ways. First, novel agents have been incorporated successfully as induction regimens, increasing the response rate before ASCT, and are now being used as part of both consolidation and maintenance with the goal of extending progression-free and overall survival. These approaches have shown considerable promise with significant improvements in outcome. Furthermore, the efficacy of novel therapeutics has also led to the investigation of these agents upfront without the immediate application of ASCT, and compelling preliminary results have been reported. Next-generation novel agents and the use of monoclonal antibodies have raised the possibility of not only successful salvage strategies to facilitate delayed transplantation for younger patients, but also the prospect of an nontransplantation approach achieving the same outcome. Moreover, this could be achieved without incurring acute toxicity or long-term complications that are inherent to high-dose alkylation, and melphalan exposure in particular. At present, the role of ASCT has therefore become an area of debate: should it be used upfront in all eligible patients, or should it be used as a salvage treatment at the time of progression for patients achieving a high quality of response with initial therapy? There is a clear need to derive a consensus that is useful for clinicians considering both protocol-directed and non-protocol-directed options for their patients. Participation in ongoing prospective randomized trials is considered vital. While preliminary randomized data from studies in Europe favor early ASCT with novel agents, differences in both agents and the combinations used, as well as limited information on overall survival and benefit for specific patient subsets, suggest that one size does not fit all. Specifically, the optimal approach to treatment of younger patients eligible for ASCT remains a key area for further research. A rigid approach to its use outside of a clinical study is difficult to justify and participation in prospective studies should be a priority.