BRAF V600E Mutation and Clonal Evolution in a Patient With Relapsed Refractory Myeloma With Plasmablastic Differentiation

Plasmablastic myeloma in Taiwan frequently presents with extramedullary and extranodal mass mimicking plasmablastic lymphoma

Plasmablastic myeloma (PBM) is a blastic morphologic variant of plasma cell myeloma with less favorable prognosis than those with non-blastic morphology. PBM is rare, without clear-cut definition and detailed clinicopathologic features in the literature. PBM may mimic plasmablastic lymphoma (PBL) as they share nearly identical morphology and immunophenotype. Using the criteria of ≥ 30% plasmablasts in tissue sections, we retrospectively recruited PBM cases and analyzed their clinical, imaging, and pathologic findings, with emphasis on extramedullary involvement. We performed immunohistochemistry, in situ hybridization for Epstein-Barr virus (EBER), and fluorescence in situ hybridization (FISH) for lymphoma- and myeloma-associated genetic alterations. Of the 25 recruited cases, 15 (60%) had extramedullary involvement, which occurred as initial presentation in nine cases. The most common extramedullary sites were soft tissue and/or skin (10/15, 67%), followed by pleural effusion, the lungs, and lymph nodes. Immunohistochemically, tumor cells expressed MYC (74%; 17/23), CD56 (56%; 14/25), and cyclin D1 (16%; 4/25), while CD117 was all negative (n = 25). Of the 20 cases stained with p53, four (20%) cases were diffusely positive, and the remaining 16 cases showed a heterogeneous pattern. EBER was negative in all 24 cases examined. Of the 13 cases examined with FISH, the genetic aberrations identified included del(13q14)(92%; 12/13), gain of chromosome 1q (90%; 9/10), loss of chromosome 1p (60%; 6/10), IGH-FGFR3 reciprocal translocation (23%; 3/13), rearranged MYC (15%; 2/13), and rearranged CCND1 (8%; 1/13), while there were no cases with TP53 deletion (n = 10) or rearrangement of BCL2 (n = 13) or BCL6 (n = 13). The prognosis was dismal regardless of the presence or absence of extramedullary involvement. In conclusion, PBM in Taiwan frequently presented as extramedullary and extranodal lesions, particularly in soft tissue and/or skin, mimicking PBL. FISH for targeted genetic alterations such as del(13q14), gain of chromosome 1q, loss of chromosome 1p, and IGH-FGFR3 might be helpful for the differential diagnoses. Larger studies are warranted to investigate the genetic alterations between PBM and PBL.

KRAS and RAS-MAPK Pathway Deregulation in Mature B Cell Lymphoproliferative Disorders

KRAS mutations account for the most frequent mutations in human cancers, and are generally correlated with disease aggressiveness, poor prognosis, and poor response to therapies. KRAS is required for adult hematopoiesis and plays a key role in B cell development and mature B cell proliferation and survival, proved to be critical for B cell receptor-induced ERK pathway activation. In mature B cell neoplasms, commonly seen in adults, KRAS and RAS-MAPK pathway aberrations occur in a relevant fraction of patients, reaching high recurrence in some specific subtypes like multiple myeloma and hairy cell leukemia. As inhibitors targeting the RAS-MAPK pathway are being developed and improved, it is of outmost importance to precisely identify all subgroups of patients that could potentially benefit from their use. Herein, we review the role of KRAS and RAS-MAPK signaling in malignant hematopoiesis, focusing on mature B cell lymphoproliferative disorders. We discuss KRAS and RAS-MAPK pathway aberrations describing type, incidence, mutual exclusion with other genetic abnormalities, and association with prognosis. We review the current therapeutic strategies applied in mature B cell neoplasms to counteract RAS-MAPK signaling in pre-clinical and clinical studies, including most promising combination therapies. We finally present an overview of genetically engineered mouse models bearing KRAS and RAS-MAPK pathway aberrations in the hematopoietic compartment, which are valuable tools in the understanding of cancer biology and etiology.

Genetic lesions in MYC and STAT3 drive oncogenic transcription factor overexpression in plasmablastic lymphoma

The mutational profile of plasmablastic lymphoma has not been described. We performed a targeted, exonic next-generation sequencing analysis of 30 plasmablastic lymphoma cases with a Bcell lymphoma-dedicated panel and fluorescence in situ hybridization for the detection of MYC rearrangements. Complete phenotyping of the neoplastic and microenvironmental cell populations was also performed. We identified an enrichment in recurrent genetic events in MYC (69% with MYC translocation or amplification and three cases with missense point mutations), PRDM1/Blimp1 and STAT3 mutations. These gene mutations were more frequent in Epstein-Barr virus (EBV)-positive disease. Other genetic events included mutations in BRAF, EP300, BCR (CD79A and CD79B), NOTCH pathway (NOTCH2, NOTCH1 and SGK1) and MYD88pL265P. Immunohistochemical analysis showed consistent MYC expression, which was higher in cases with MYC rearrangements, together with phospho-STAT3 (Tyr705) overexpression in cases with STAT3 SH2 domain mutations. Microenvironmental cell populations were heterogeneous and unrelated to EBV, with enrichment of tumor-associated macrophages (TAM) and PD1-positive T cells. PD-L1 was expressed in all cases in the TAM population but only in the neoplastic cells in five cases (4 of 14 EBV-positive cases). HLA expression was absent in the majority of cases of plasmablastic lymphoma. In summary, the mutational profile of plasmablastic lymphoma is heterogeneous and related to EBV infection. Genetic events in MYC, STAT3 and PRDM1/Blimp1 are more frequent in EBV-positive disease. An enrichment in TAM and PD1 reactive T lymphocytes is found in the microenvironment of plasmablastic lymphoma and a fraction of the neoplastic cells express PD-L1.

Combination of Dabrafenib and Trametinib for the Treatment of Relapsed and Refractory Multiple Myeloma Harboring BRAF V600E Mutation

Multiple myeloma (MM) is an incurable plasma cell neoplasia characterized by relapsed and/or refractory (R/R) disease course, which poses a major therapeutic challenge. New therapies, including BRAF V600E mutation targeting, may become a new treatment option for R/R MM. In combination with mitogen-activated protein kinase inhibitors (MEKi), BRAF inhibitors (BRAFi) could provide better tailored clinical management, although experience in this field is lacking. To this date, there is only one case describing R/R MM treatment with BRAFi vemurafenib and MEKi cobimetinib. This is the first case presenting a R/R MM patient treated with BRAFi dabrafenib and MEKi trametinib.

Liquid biopsies for multiple myeloma in a time of precision medicine

Multiple myeloma (MM) is a challenging, progressive, and highly heterogeneous hematological malignancy. MM is characterized by multifocal proliferation of neoplastic plasma cells in the bone marrow (BM) and sometimes in extramedullary organs. Despite the availability of novel drugs and the longer median overall survival, some patients survive more than 10 years while others die rapidly. This heterogeneity is mainly driven by biological characteristics of MM cells, including genetic abnormalities. Disease progressions are mainly due to the inability of drugs to overcome refractory disease and inevitable drug-resistant relapse. In clinical practice, a bone marrow biopsy, mostly performed in one site, is still used to access the genetics of MM. However, BM biopsy use is limited by its invasive nature and by often not accurately reflecting the mutational profile of MM. Recent insights into the genetic landscape of MM provide a valuable opportunity to implement precision medicine approaches aiming to enable better patient profiling and selection of targeted therapies. In this review, we explore the use of the emerging field of liquid biopsies in myeloma patients considering current unmet medical needs, such as assessing the dynamic mutational landscape of myeloma, early predictors of treatment response, and a less invasive response monitoring.

Lymphoid Neoplasms With Plasmablastic Differentiation: A Comprehensive Review and Diagnostic Approaches

Plasmablastic neoplasms encompass several entities including plasmablastic lymphoma, plasmablastic plasmacytoma/multiple myeloma, primary effusion lymphoma and its extracavitary variant, anaplastic lymphoma kinase-positive large B-cell lymphoma, and Kaposi sarcoma-associated herpesvirus/human herpesvirus 8 (HHV8)-positive diffuse large B-cell lymphoma, not otherwise specified. Morphologically, the tumor cells are large with eccentrically located nuclei, prominent nucleoli, and basophilic/amphophilic cytoplasm. Immunophenotypically, the tumor cells express plasma cell-related antigens including CD38, CD138, interferon regulatory factor-4 (IRF4)/MUM1, PR domain zinc finger protein-1 (PRDM1), and/or X-box binding protein-1 (XBP1), with frequent loss of CD20. These tumors are diagnostically challenging for general pathologists due to their overlapping morphology and immunophenotype, and due to their rarity, and particularly so when clinical and radiologic information is insufficient. We also discuss HHV8-negative effusion-based lymphoma due to its overlapping features with primary effusion lymphoma. In this review, we focus on the useful diagnostic markers and pertinent molecular findings in these distinct entities and propose a practical diagnostic algorithm using anaplastic lymphoma kinase, HHV8, in situ hybridization for Epstein-Barr virus-encoded small RNA, immunoglobulin M, light chain stains, and clinicoradiologic criteria to avoid misdiagnosis. At the molecular level, MYC protein overexpression with or without MYC rearrangement and PRDM1-inactivating mutations or deletions are noted in a subset of such tumors, especially in plasmablastic lymphoma. Prognosis in these entities is dismal with conventional CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy. Therefore, novel target therapies, such as anti-CD30 agents, and/or immune blockade therapy, are potential treatment options in the future.

Toward personalized treatment in multiple myeloma based on molecular characteristics

To date, the choice of therapy for an individual multiple myeloma patient has been based on clinical factors such as age and comorbidities. The widespread evolution, validation, and clinical utilization of molecular technologies, such as fluorescence in situ hybridization and next-generation sequencing has enabled the identification of a number of prognostic and predictive biomarkers for progression-free survival, overall survival, and treatment response. In this review, we argue that in order to continue to improve myeloma patient outcomes incorporating such biomarkers into the routine diagnostic workup of patients will allow for the use of personalized, biologically based treatments.

Using Genome Sequence to Enable the Design of Medicines and Chemical Probes

Rapid progress in genome sequencing technology has put us firmly into a postgenomic era. A key challenge in biomedical research is harnessing genome sequence to fulfill the promise of personalized medicine. This Review describes how genome sequencing has enabled the identification of disease-causing biomolecules and how these data have been converted into chemical probes of function, preclinical lead modalities, and ultimately U.S. Food and Drug Administration (FDA)-approved drugs. In particular, we focus on the use of oligonucleotide-based modalities to target disease-causing RNAs; small molecules that target DNA, RNA, or protein; the rational repurposing of known therapeutic modalities; and the advantages of pharmacogenetics. Lastly, we discuss the remaining challenges and opportunities in the direct utilization of genome sequence to enable design of medicines.

Risk Stratification in Multiple Myeloma

There are many prognostic variables in multiple myeloma and the difficulty is in deciding which is truly significant. The widely used International Staging System (ISS) does not incorporate genetics, age, and other important variables in its risk stratification. Although it has its own limitations, the recently published Revised International Staging System (R-ISS) that was built upon the framework of ISS, is a more comprehensive and predictive tool for multiple myeloma patients and should be henceforth utilised. We will review the current prognostic variables and their significance in this paper.

Precision Medicine in Myeloma: Challenges in Defining an Actionable Approach

Recently, large sequencing studies have provided insights into the mutational landscape of multiple myeloma (MM), identifying actionable mutations and giving a precious opportunity for exploring new targeted therapies. The main goal of precision medicine, matching patients with the right drug, seems to be closer than ever. However, no targeted therapies in MM are approved yet. Several clinical trials testing targeted drugs and enrolling patients with MM are currently ongoing and will provide predictive biomarkers that might support clinical decision making. In this review, we evaluate the evidence supporting the implementation of precision medicine in MM and we discuss the challenges that should be dealt with in this imminent and promising new era.

New Targets and New Agents in High-Risk Multiple Myeloma

Advances in the treatment of multiple myeloma have resulted in dramatic improvements in outcomes for patients. The newly emerging profiling of mutations emerging as a consequence of large prospective sequencing studies such as the CoMMpass Study or other efforts from European investigators are not further helping to define the place and role for personalized medicine in myeloma. While mutations such as NRAS, KRAS, and BRAF do occur in myeloma, it is not clear that targeting them as a single drug strategy will result in meaningful responses or durations of response. Personalized medicine in multiple myeloma at this time likely entails the use of risk-based approaches for maintenance therapy, the use of current biology-based treatments such as proteasome inhibitors, and immunomodulatory agents, with an eye towards the use of mutation-specific treatments in the setting of minimal residual disease or in concert with biology-based treatments overall.

Vemurafenib in combination with cobimetinib in relapsed and refractory extramedullary multiple myeloma harboring the BRAF V600E mutation

BRAF mutations are present in a variety of cancers and cause constitutive activation of the Ras-Raf-MEK-ERK signaling pathway. In cutaneous malignant melanoma, combined treatment with BRAF and MEK inhibitors is associated with high response rates and has been shown to improve progression free as well as overall survival compared to BRAF inhibition alone. In multiple myeloma, BRAF mutations are detectable only in a minority of patients. Only few data are available regarding the clinical activity of BRAF inhibitors in BRAF-positive multiple myeloma patients, including some anecdotal reports on remarkable responses in individuals being resistant to all other available anti-myeloma treatment approaches. We here present the first report on the combination of vemurafenib and cobimetinib in a young patient with highly resistant and rapidly progressing multiple myeloma harboring the BRAF V600E mutation who achieved a rapid and sustained response to this combination therapy.

Molecular spectrum of BRAF, NRAS and KRAS gene mutations in plasma cell dyscrasias: implication for MEK-ERK pathway activation

Multiple myeloma (MM) is a clinically and genetically heterogeneous plasma cell (PC) malignancy. Whole-exome sequencing has identified therapeutically targetable mutations such as those in the mitogen-activated protein kinase (MAPK) pathway, which are the most prevalent MM mutations. We used deep sequencing to screen 167 representative patients with PC dyscrasias [132 with MM, 24 with primary PC leukemia (pPCL) and 11 with secondary PC leukemia (sPCL)] for mutations in BRAF, NRAS and KRAS, which were respectively found in 12%, 23.9% and 29.3% of cases. Overall, the MAPK pathway was affected in 57.5% of the patients (63.6% of those with sPCL, 59.8% of those with MM, and 41.7% of those with pPCL). The majority of BRAF variants were comparably expressed at transcript level. Additionally, gene expression profiling indicated the MAPK pathway is activated in mutated patients. Finally, we found that vemurafenib inhibition of BRAF activation in mutated U266 cells affected the expression of genes known to be associated with MM. Our data confirm and extend previous published evidence that MAPK pathway activation is recurrent in myeloma; the finding that it is mediated by BRAF mutations in a significant fraction of patients has potentially immediate clinical implications.

MYEOV gene overexpression in primary plasma cell leukemia with t(11;14)(q13;q32)

Primary plasma cell leukemia (pPCL) is an uncommon form of plasma cell dyscrasia, and the most aggressive of the human monoclonal gammopathies. The t(11;14)(q13;q32) rearrangement is the most common alteration in pPCL, promoting cyclin D1 (CCND1) gene overexpression caused by its juxtaposition with the immunoglobulin heavy locus chromosome region. The myeloma overexpressed (MYEOV) gene maps very close to the CCND1 gene on chromosome 11, but its overexpression is rarely observed in multiple myeloma. The present study describes a case of pPCL with t(11;14) characterized by a breakpoint on der(11), unlike the one usually observed. Droplet digital polymerase chain reaction analysis revealed overexpression of CCND1 and MYEOV. To the best of our knowledge, MYEOV gene overexpression has never been previously described in pPCL.

Inferring mutational timing and reconstructing tumour evolutionary histories

Cancer evolution can be considered within a Darwinian framework. Both micro and macro-evolutionary theories can be applied to understand tumour progression and treatment failure. Owing to cancers' complexity and heterogeneity the rules of tumour evolution, such as the role of selection, remain incompletely understood. The timing of mutational events during tumour evolution presents diagnostic, prognostic and therapeutic opportunities. Here we review the current sampling and computational approaches for inferring mutational timing and the evidence from next generation sequencing-informed data on mutational timing across all tumour types. We discuss how this knowledge can be used to illuminate the genes and pathways that drive cancer initiation and relapse; and to support drug development and clinical trial design.

BRAF V600E mutation in early-stage multiple myeloma: good response to broad acting drugs and no relation to prognosis

In this study, we analyzed the prevalence and clone size of BRAF V600E mutation in 209 patients with multiple myeloma and related the results to clinical phenotype, response and survival. Biopsies were screened for BRAF V600E by allele-specific real-time PCR (AS-PCR). Positive results were confirmed by immunohistochemistry, Sanger sequencing and, in three patients from whom we had stored purified myeloma cells, whole-exome sequencing. Eleven patients (5.3%) were BRAF V600E mutation positive by AS-PCR and at least one other method. The fraction of mutated cells varied from 4 to 100%. BRAF V600E-positive patients had no characteristic clinical phenotype except for significantly higher levels of serum creatinine (125 versus 86 μmol/l) Seven of eleven patients responded with at least very good partial response to alkylators, immunomodulatory agents or proteasome inhibitors. Progression-free and overall survival were similar in patients with and without the mutation. By this integrated approach, we found that patients with BRAF V600E mutation responded very well to broad acting drugs and there was no relation to prognosis in early-stage myeloma. In particular, a large mutated cell fraction did not correlate with aggressive disease.