Primary Plasma Cell Leukemia: Clinical, Immunophenotypic, DNA Ploidy, and Cytogenetic Characteristics

Efficacy and Safety Analysis of VRD-PDCE in Treatment-Native Patients with Multiple Extramedullary Plasmacytomas or Plasma Cell Leukemia

The prognosis of multiple extramedullary plasmacytomas (MEP) and plasma cell leukemia (PCL) is extremely poor, with the median overall survival (OS) of only 8 months with standard chemotherapy. Innovative treatment approaches incorporating various strategies are required to improve outcome. From November 2019 to September 2021, a total of 12 newly diagnosed MEP or PCL patients were enrolled in our department. An intensive chemotherapy treatment as VRD-PDCE consisted of bortezomib, lenalidomide, dexamethasone plus cisplatin, pegylated liposomal doxorubicin, cyclophosphamide and etoposide was first proposed. Disease activity and toxicity were evaluated after each cycle. Of the patients receiving therapy achieved a rapid and sustained response, and the overall response rate (ORR) was up to 75%. Nine patients achieved partial response (PR) or better, the response was the best response and the median time to best response was 4 cycles. Median overall survival (OS) and progression-free survival (PFS) were 24 (5-30) months and 18 (2-23) months. The toxicities were acceptable and there was no treatment related mortality. Our intensive treatment showed encouraging results in terms of disease control and improving survival, VRD-PDCE may be a novel regimen which is feasible and generally well-tolerated in MEP or PCL patients.

Next generation flow for minimally-invasive blood characterization of MGUS and multiple myeloma at diagnosis based on circulating tumor plasma cells (CTPC)

Here, we investigated for the first time the frequency and number of circulating tumor plasma cells (CTPC) in peripheral blood (PB) of newly diagnosed patients with localized and systemic plasma cell neoplasms (PCN) using next-generation flow cytometry (NGF) and correlated our findings with the distinct diagnostic and prognostic categories of the disease. Overall, 508 samples from 264 newly diagnosed PCN patients, were studied. CTPC were detected in PB of all active multiple myeloma (MM; 100%), and smoldering MM (SMM) patients (100%), and in more than half (59%) monoclonal gammopathy of undetermined significance (MGUS) cases (p <0.0001); in contrast, CTPC were present in a small fraction of solitary plasmacytoma patients (18%). Higher numbers of CTPC in PB were associated with higher levels of BM infiltration and more adverse prognostic features, together with shorter time to progression from MGUS to MM (p <0.0001) and a shorter survival in MM patients with active disease requiring treatment (p ≤ 0.03). In summary, the presence of CTPC in PB as assessed by NGF at diagnosis, emerges as a hallmark of disseminated PCN, higher numbers of PB CTPC being strongly associated with a malignant disease behavior and a poorer outcome of both MGUS and MM.

Trends in survival of patients with primary plasma cell leukemia: a population-based analysis

Primary plasma cell leukemia (pPCL) is a rare malignancy with an aggressive course and poor outcome. There has been significant improvement in the survival of multiple myeloma patients over the past decade as a result of incorporating autologous stem cell transplantation (ASCT) and novel agents into treatment regimens. However, it is unknown whether these therapies have had a similar impact on the survival of patients with pPCL. We conducted an analysis of the Surveillance, Epidemiology, and End Results database to evaluate the trends in survival of 445 patients with pPCL between 1973 and 2009. The widespread availability of ASCT and use of novel agents in the upfront setting of multiple myeloma and pPCL began after 1995 and 2006, respectively. The median overall survival based on periods of diagnosis were 5, 6, 4, and 12 months for those diagnosed during 1973-1995, 1996-2000, 2001-2005, and 2006-2009, respectively (P = .001). Thus, the current study confirms the recent survival improvement in pPCL within a large US population that may be associated with the use of better therapeutic strategies.

The role of CD19 and CD27 in the diagnosis of multiple myeloma by flow cytometry: a new statistical model

We have developed a new statistical diagnostic model that examines the correlation between immunophenotype and clonality as detected by flow cytometry (FC) and histology, defining the diagnostic role of FC in multiple myeloma (MM). The 192 bone marrow samples from patients and control subjects were studied for routine diagnostic analysis of MM; a minimum of 100 plasma cells (PCs) were analyzed for each patient sample. A direct 7- or 8-color method was applied to study the immunophenotype of PCs, utilizing a FACSCanto II (BD Biosciences, San Jose, CA). Samples were labeled with fluorochrome-conjugated monoclonal antibodies (AmCyan, Pac Blue, fluorescein isothiocyanate, phycoerythrin [PE], PECy7, peridinin-chlorophyll protein, allophycocyanin [APC], and APC-Cy7) to the following antigens: CD138, CD81, CD200, CD221, CD45, CD38, CD28, CD19, CD27, CD117, CD38, CD33, CD20, CD56, CD10, and immunoglobulin κ and λ light chains. Among all antigens tested, CD19 and CD27, when applied to our model, resulted in optimal concordance with histology. This model defines the effective diagnostic role FC could have in MM and in the detection of minimal residual disease.

Genome-wide allelic state analysis on flow-sorted tumor fractions provides an accurate measure of chromosomal aberrations

Chromosomal aberrations are a common characteristic of cancer and are associated with copy number abnormalities and loss of heterozygosity (LOH). Tumor heterogeneity, low tumor cell percentage, and lack of knowledge of the DNA content impair the identification of these alterations especially in aneuploid tumors. To accurately detect allelic changes in carcinomas, we combined flow-sorting and single nucleotide polymorphism arrays. Cells derived from archival cervical and colon cancers were flow-sorted based on differential vimentin and keratin expression and DNA content and analyzed on single nucleotide polymorphism arrays. A new algorithm, the lesser allele intensity ratio, was used to generate a molecular measure of chromosomal aberrations for each case. Flow-sorting significantly improved the detection of copy number abnormalities; 31.8% showed an increase in amplitude and 23.2% were missed in the unsorted fraction, whereas 15.9% were detected but interpreted differently. Integration of the DNA index in the analysis enabled the identification of the allelic state of chromosomal aberrations, such as LOH ([A]), copy-neutral LOH ([AA]), balanced amplifications ([AABB]), and allelic imbalances ([AAB] or [AAAB], etc.). Chromosomal segments were sharply defined. Fluorescence in situ hybridization copy numbers, as well as the high similarity between the DNA index and the allelic state index, which is the average of the allelic states across the genome, validated the method. This new approach provides an individual molecular measure of chromosomal aberrations and will likely have repercussions for preoperative molecular staging, classification, and prognostic profiling of tumors, particularly for heterogeneous aneuploid tumors, and allows the study of the underlying molecular genetic mechanisms and clonal evolution of tumor subpopulations.

Cooperation between heparin-binding EGF-like growth factor and interleukin-6 in promoting the growth of human myeloma cells

Interleukin-6 (IL-6) is a major survival and proliferation factor of human malignant plasma cells and IL-6 dependent myeloma cell lines can be obtained from patients with terminal disease. We show here that mutated diphtheria toxin, a specific inhibitor of heparin-binding epidermal growth factor-like growth factor (HB-EGF), blocked the IL-6-induced growth of two myeloma cell lines (XG-1 and XG-14) and did not significantly affect that of two other cell lines (XG-6 and XG-13). The IL-6 mediated growth of myeloma cells was also inhibited by antibodies to ErbB1, a receptor for HB-EGF. The XG-1 and XG-14 cell lines that are sensitive to HB-EGF inhibitors overexpressed HB-EGF and EGF receptor (ErbB1) genes. They also overexpressed CD9, a tetraspanin that binds to the heparin-binding domain of HB-EGF and is critical for promoting ErbB1 activation by HB-EGF. The XG-6 and XG-13 myeloma cells that were not significantly sensitive to HB-EGF antagonists, poorly expressed HB-EGF, ErbB1 and CD9 genes or proteins. We demonstrated that recombinant HB-EGF supported the long-term growth of myeloma cells, as did IL-6. The myeloma cell growth factor activity of HB-EGF was completely inhited by antibodies to ErbB1, but also by antibodies to gp130 IL-6 transducer or to IL-6. These data indicate that in the XG-1 and XG-14 IL-6-dependent myeloma cell lines, the CD9/HB-EGF/erbB1 and the IL-6/IL-6R/gp130 pathways cooperate synergistically to trigger myeloma cell growth. They suggest that inhibitors of the EGF receptor or HB-EGF may be useful for inducing myeloma cell apoptosis in patients with multiple myeloma.

Molecular features responsible for the absence of immunoglobulin heavy chain protein synthesis in an IgH− subgroup of multiple myeloma

This study involved 12 patients with multiple myeloma (MM), in whom malignant plasma cells did not contain immunoglobulin heavy chain (IgH) protein chains. Southern blot analysis revealed monoallelic Jh gene rearrangements in 10 patients, biallelic rearrangement in 1 patient, and biallelic deletion of the Jh and Cμ regions in 1 patient. Heteroduplex polymerase chain reaction analysis enabled the identification and sequencing of 9 clonal Jhgene rearrangements. Only 4 of the joinings were complete Vh-(D)-Jhrearrangements, including 3 in-frame rearrangements with evidence of somatic hypermutation. Five rearrangements concerned incomplete Dh-Jh joinings, mainly associated with deletion of the other allele. Curiously, in at least 1 of these 5 cases the second allele seemed to be in germline configuration, whereas the in-frame Vκ-Jκgene rearrangements contained somatic mutations. The configuration of the IGH genes was further investigated by use of Ch probes. In 5 patients the rearrangements in the Jh and Ch regions were not concordant, probably caused by illegitimate IGH class switch recombination (chromosomal translocations to 14q32.3). These data indicate that in many IgH− MM patients illegitimateIGH class switch rearrangement or illegitimate deletion of the functional Vh-(Dh)-Jhallele are responsible for IgH negativity. For example, the exclusive presence ofDh-Jhrearrangements in combination with mutated IGK genes can only be explained in terms of normal B-cell development, if the second (functional) IGH allele is deleted, which was probably the case in most patients. Therefore, defects at the DNA level are responsible for the lack of IgH protein production in most IgH− MM patients.