CD27-triggering on primary plasma cell leukaemia cells has anti-apoptotic effects involving mitogen activated protein kinases

Multiparametric Flow Cytometry in the Evaluation of Plasma Cell Proliferative Disorders: Current Paradigms for Clinical Practice

Diagnosis of plasma cell proliferative disorders (PCPDs) is primarily based on the demonstration of monoclonal protein (M-Protein) in blood and/ or urine which often precedes clinical manifestations of the disease. The basic pathophysiology behind the M-protein presence is the proliferation of clonal plasma cells (PCs) in bone marrow or extramedullary sites and is assessed using cytomorphology and immunophenotyping. The role of multiparametric flow cytometry (MFC) for PC identification is technically the most valuable tool in this context as it characterizes as well as quantifies the clonal PCs based on differential expression of various immunophenotypic (IPT) markers. From a diagnostic perspective, MFC is critical in the definite identification of the clonal PCs and delineates benign and borderline entities at one end of the spectrum (MGUS, SMM) with lower clonal PC% and, malignant diseases at the other end (MM and PCL) with higher clonal PC fraction. The role of MFC in assessment of measurable residual disease (MRD) and monitoring of progression in MM and various PCPDs has been validated in multiple clinical studies and is probably one of the most promising tools for predicting treatment outcomes. Furthermore, MFC also plays a crucial role in disease prognostication based on specific IPT profiles. An additional role of MFC in the current clinical scenario is the evaluation of tumor microenvironment based on immune cell repertoire, which is reflecting encouraging results across. Thus, in the current review we concisely describe the role of MFC as a reliable and essential modality in PCPDs, from diagnosis to prediction of treatment outcome and disease monitoring.

Understanding the Bioactivity and Prognostic Implication of Commonly Used Surface Antigens in Multiple Myeloma

Multiple myeloma (MM) progression is dependent on its interaction with the bone marrow microenvironment and the immune system and is mediated by key surface antigens. Some antigens promote adhesion to the bone marrow matrix and stromal cells, while others are involved in intercellular interactions that result in differentiation of B-cells to plasma cells (PC). These interactions are also involved in malignant transformation of the normal PC to MM PC as well as disease progression. Here, we review selected surface antigens that are commonly used in the flow cytometry analysis of MM for identification of plasma cells (PC) and the discrimination between normal and malignant PC as well as prognostication. These include the markers: CD38, CD138, CD45, CD19, CD117, CD56, CD81, CD27, and CD28. Furthermore, we will discuss the novel marker CD24 and its involvement in MM. The bioactivity of each antigen is reviewed, as well as its expression on normal vs. malignant PC, prognostic implications, and therapeutic utility. Understanding the role of these specific surface antigens, as well as complex co-expressions of combinations of antigens, may allow for a more personalized prognostic monitoring and treatment of MM patients.

The CD70-CD27 axis in oncology: the new kids on the block

The immune checkpoint molecule CD70 and its receptor CD27 are aberrantly expressed in many hematological and solid malignancies. Dysregulation of the CD70-CD27 axis within the tumor and its microenvironment is associated with tumor progression and immunosuppression. This is in contrast to physiological conditions, where tightly controlled expression of CD70 and CD27 plays a role in co-stimulation in immune responses. In hematological malignancies, cancer cells co-express CD70 and CD27 promoting stemness, proliferation and survival of malignancy. In solid tumors, only expression of CD70 is present on the tumor cells which can facilitate immune evasion through CD27 expression in the tumor microenvironment. The discovery of these tumor promoting and immunosuppressive effects of the CD70-CD27 axis has unfolded a novel target in the field of oncology, CD70.

In this review, we thoroughly discuss current insights into expression patterns and the role of the CD70-CD27 axis in hematological and solid malignancies, its effect on the tumor microenvironment and (pre)clinical therapeutic strategies.

Accurate classification of plasma cell dyscrasias is achieved by combining artificial intelligence and flow cytometry

Monoclonal gammopathy of unknown significance (MGUS), smouldering multiple myeloma (SMM), and multiple myeloma (MM) are very common neoplasms. However, it is often difficult to distinguish between these entities. In the present study, we aimed to classify the most powerful markers that could improve diagnosis by multiparametric flow cytometry (MFC). The present study included 348 patients based on two independent cohorts. We first assessed how representative the data were in the discovery cohort (123 MM, 97 MGUS) and then analysed their respective plasma cell (PC) phenotype in order to obtain a set of correlations with a hypersphere visualisation. Cluster of differentiation (CD)27 and CD38 were differentially expressed in MGUS and MM (P < 0·001). We found by a gradient boosting machine method that the percentage of abnormal PCs and the ratio PC/CD117 positive precursors were the most influential parameters at diagnosis to distinguish MGUS and MM. Finally, we designed a decisional algorithm allowing a predictive classification ≥95% when PC dyscrasias were suspected, without any misclassification between MGUS and SMM. We validated this algorithm in an independent cohort of PC dyscrasias (n = 87 MM, n = 41 MGUS). This artificial intelligence model is freely available online as a diagnostic tool application website for all MFC centers worldwide (https://aihematology.shinyapps.io/PCdyscrasiasToolDg/).

A clinical perspective on plasma cell leukemia; current status and future directions

Primary plasma cell leukemia (pPCL) is an aggressive plasma cell disorder with a guarded prognosis. The diagnosis is confirmed when peripheral blood plasma cells (PCs) exceed 20% of white blood cells or 2000/μL. Emerging data demonstrates that patients with lower levels of circulating (PCs) have the same adverse prognosis, challenging the clinical disease definition, but supporting the adverse impact of circulating PCs. The cornerstone of treatment consists of combination therapy incorporating a proteasome inhibitor, an immunomodulatory agent, steroids, and/or anthracyclines and alkylators as part of more-intensive chemotherapy, followed by consolidative autologous hematopoietic cell transplantation in eligible patients and then maintenance therapy. Monoclonal antibodies are also currently being evaluated in this setting with a strong rationale for their use based on their activity in multiple myeloma (MM). Due to limited therapeutic studies specifically evaluating pPCL, patients with pPCL should be considered for clinical trials. In contrast to MM, the outcomes of patients with pPCL have only modestly improved with novel therapies, and secondary PCL arising from MM in particular is associated with a dismal outlook. Newer drug combinations, immunotherapy, and cellular therapy are under investigation, and these approaches hopefully will demonstrate efficacy to improve the prognosis of pPCL.

Plasma cell leukemia: consensus statement on diagnostic requirements, response criteria and treatment recommendations by the International Myeloma Working Group

Plasma cell leukemia (PCL) is a rare and aggressive variant of myeloma characterized by the presence of circulating plasma cells. It is classified as either primary PCL occurring at diagnosis or as secondary PCL in patients with relapsed/refractory myeloma. Primary PCL is a distinct clinic-pathological entity with different cytogenetic and molecular findings. The clinical course is aggressive with short remissions and survival duration. The diagnosis is based upon the percentage (≥ 20%) and absolute number (≥ 2 × 10(9)/l) of plasma cells in the peripheral blood. It is proposed that the thresholds for diagnosis be re-examined and consensus recommendations are made for diagnosis, as well as, response and progression criteria. Induction therapy needs to begin promptly and have high clinical activity leading to rapid disease control in an effort to minimize the risk of early death. Intensive chemotherapy regimens and bortezomib-based regimens are recommended followed by high-dose therapy with autologous stem cell transplantation if feasible. Allogeneic transplantation can be considered in younger patients. Prospective multicenter studies are required to provide revised definitions and better understanding of the pathogenesis of PCL.

The CD27 and CD70 costimulatory pathway inhibits effector function of T helper 17 cells and attenuates associated autoimmunity

T helper 17 (Th17) cells protect against infection but also promote inflammation and autoimmunity. Therefore, the factors that govern Th17 cell differentiation are of special interest. The CD27 and CD70 costimulatory pathway impeded Th17 effector cell differentiation and associated autoimmunity in a mouse model of multiple sclerosis. CD27 or CD70 deficiency exacerbated disease, whereas constitutive CD27 signaling strongly reduced disease incidence and severity. CD27 signaling did not impact master regulators of T helper cell lineage commitment but selectively repressed transcription of the key effector molecules interleukin-17 (IL-17) and the chemokine receptor CCR6 in differentiating Th17 cells. CD27 mediated this repression at least in part via the c-Jun N-terminal kinase (JNK) pathway that restrained IL-17 and CCR6 expression in differentiating Th17 cells. CD27 signaling also resulted in epigenetic silencing of the Il17a gene. Thus, CD27 costimulation via JNK signaling, transcriptional, and epigenetic effects suppresses Th17 effector cell function and associated pathological consequences.

E. coli-produced BMP-2 as a chemopreventive strategy for colon cancer: a proof-of-concept study

Colon cancer is a serious health problem, and novel preventive and therapeutical avenues are urgently called for. Delivery of proteins with anticancer activity through genetically modified bacteria provides an interesting, potentially specific, economic and effective approach here. Interestingly, bone morphogenetic protein 2 (BMP-2) is an important and powerful tumour suppressor in the colon and is thus an attractive candidate protein for delivery through genetically modified bacteria. It has not been shown, however, that BMP production in the bacterial context is effective on colon cancer cells. Here we demonstrate that transforming E. coli with a cDNA encoding an ileal-derived mature human BMP-2 induces effective apoptosis in an in vitro model system for colorectal cancer, whereas the maternal organism was not effective in this respect. Furthermore, these effects were sensitive to cotreatment with the BMP inhibitor Noggin. We propose that prevention and treatment of colorectal cancer using transgenic bacteria is feasible.

Effect of wild type PTEN gene on proliferation and invasion of multiple myeloma

We explored the effect of the wild type PTEN gene on the proliferation, apoptosis and invasive ability of multiple myeloma (MM) cells from MM patients and RPMI 8226 cells (a human myeloma cell line), and the effect of the PTEN/focal adhesion kinase (FAK)/MMP signaling pathway on the invasion activity of RPMI 8226 cells. The proliferation of RPMI 8226 cells and purified myeloma cells from MM patients were markedly inhibited after these cells were transfected with recombinant adenovirus-PTEN vectors containing green fluorescent protein (Ad-PTEN-GFP). Maximum growth inhibition of RPMI 8226 cells and purified myeloma cells from MM patients by AD-PTEN-GFP was 42.01 and 24.75%, respectively. After transfection with PTEN-siRNA, the proliferation of RPMI 8226 cells was increased significantly compared with NS-siRNA transfected controls. The maximal survival rate was 141.55 +/- 8.34% in PTEN-siRNA transfected RPMI 8226 cells. Apoptosis of RPMI 8226 cells or purified myeloma cells from MM patients in the Ad-PTEN-GFP group was increased significantly when compared with that in the Ad-GFP (adenovirus vectors only expressing green fluorescent protein) group (p < 0.01). The cell cycle of RPMI 8226 cells was arrested at the G2/M phase. Furthermore, the number of cells that migrated through the matrigel and filter from the upper chamber to the lower chamber in the transwell assay in the Ad-GFP group was significantly larger than that in the Ad-PTEN-GFP group (52.65 +/- 7.39 vs. 23.50 +/- 6.12, p < 0.01). In the PTEN-siRNA group, the cell number (79.50 +/- 11.89) was significantly larger than that in the NS-siRNA group (47.17 +/- 7.76, p < 0.01). When RPMI 8226 cells were transfected with Ad-PTEN-GFP or NS-siRNA, the expression level of PTEN mRNA was up-regulated, and the expression levels of FAK, MMP-2 and MMP-9 mRNA were down-regulated significantly compared with that of the Ad-GFP group and the PTEN-siRNA group (p < 0.01, p < 0.05). The protein levels of FAK and p-FAK, MMP-2 and MMP-9 in RPMI 8226 cells which were transfected with Ad-PTEN-GFP decreased significantly, but increased significantly in PTEN-siRNA transfected RPMI 8226 cells (p < 0.01, p<0.05). These results indicated that wild type PTEN, which inhibited FAK, MMP-2, and MMP-9, could suppress the proliferation and invasion ability of multiple myeloma cells. Modulating the expression of PTEN may be a potential strategy for the treatment of multiple myeloma.

Extramedullary (EMP) relapse in unusual locations in multiple myeloma: Is there an association with precedent thalidomide administration and a correlation of special biological features with treatment and outcome?

Extramedullary relapse constitutes an uncommon manifestation of multiple myeloma (MM), characterized by highly malignant histology, special biological features, resistance to treatment and poor outcome. Its incidence has been increased during the last years, probably due to the introduction of novel strategies in the management of MM, including intensified treatment and immunomodulatory drugs. Here we report nine cases of extramedullary relapse of MM, presented in unusual locations, seven of which had previously been treated with thalidomide-containing regimens (TCR). Our aim was to explore the morphological, immunophenotypical, molecular and laboratory characteristics accompanying EMP-relapse and seek possible correlations with treatment and clinical outcome.

Response of primary plasma cell leukemia to the combination of bortezomib and dexamethasone: do specific cytogenetic and immunophenotypic characteristics influence treatment outcome?

Plasma cell leukemia (PCL) is a rare and aggressive form of plasma cell dyscrasias. Its special biological characteristics may play an important role in the poor outcome when treated with conventional therapy or even with stem cell transplantation. New treatment approaches based on the biology of this disease are mandatory. Here we present three cases of primary PCL with adverse cytogenetics (deletion 13q14 and translocation 4;14) and specific immunophenotypic features (CD27 antigen strong expression) in which excellent response and sustained remission was achieved with the combination of bortezomib and dexamethasone. The possible role of these biological characteristics is been analyzed.

CD44 and CD27 delineate B-precursor stages with different recombination status and with an uneven distribution in nonmalignant and malignant hematopoiesis

The expression of CD27 and CD44 correlate with the genotype of B-precursor acute lymphoblastic leukemia (ALL). Based on the expression of these antigens, we identified counterparts of TEL/AML1(pos) and TEL/AML1(neg) leukemic cells in nonmalignant bone marrow. Although CD27 is known as a marker of mature memory B cells, we recently showed that CD27 is also expressed by malignant and nonmalignant B precursors. Here, we show that CD27 and CD44 delineate stages of B-precursor development. Well-established differentiation markers showed that the developmental sequence starts from undetermined progenitors, expressing CD44. Upon B-lineage commitment, cells gain CD27 and lose CD44. The CD27(pos)CD44(neg) (CD27 single positive, 27SP) cells are the earliest stage within CD10(pos)CD19(pos) B precursors and express RAG-1 and TDT. These cells correspond to TEL/AML1(pos) ALL (1/4 pediatric B-precursor ALL). The development follows to CD27/CD44 double-positive (27/44DP) stage, 44SP stage and CD27/CD44 double-negative (27/44DN) stage. Before exit to periphery, CD44 is reexpressed. The 27/44DP cells are mostly large and profoundly suppress RAG-1. Despite their presumably high proliferation potential, 27/44DP cells rarely dominate in leukemia. At 44SP stage, which corresponds to TEL/AML1(neg) leukemias, RAG-1 is reexpressed and Ig light chain gene starts to be rearranged.

Low CD27 expression in plasma cell dyscrasias correlates with high-risk disease: an immunohistochemical analysis

Genome-wide expression studies using complementary DNA microarrays recently suggested a number of intriguing candidate genes for distinguishing plasma cell dyscrasias. Our objective was to test select markers using immunohistochemical analysis and a tissue microarray from paraffin-embedded bone marrow core biopsy specimens obtained from 8 patients with monoclonal gammopathy of undetermined significance, 17 with plasmacytoma, 160 with multiple myeloma, and 15 with plasma cell leukemia (PCL). We immunostained serial sections for CD138, CD27, CD56, p27, Ki-67, CD3, and CD20. Each core was scored in duplicate by observers blinded to phenotype and reported as the average percentage of CD138+ cells. The Mann-Whitney U test was used to determine significance between groups. PCL showed significantly less immunostaining for CD27 (P < .01) and p27 (P < .05) compared with plasmacytoma and multiple myeloma. Low CD27 expression also was associated with plasmacytoma progression to multiple myeloma (P <.05). Our results support the hypothesis that low CD27 expression correlates with high-risk disease, including primary PCL and decreased progression-free survival in solitary plasmacytoma.

Targeting signalling pathways for the treatment of multiple myeloma

Multiple myeloma (MM) is characterised by the expansion of monoclonal immunoglobulin-secreting plasma cells. Despite recent advances in systemic and supportive therapy, it remains incurable, with a median survival of about three years. Development of MM is a multistep process associated with an increasing frequency of chromosomal abnormalities and complex translocations, which induce mutations in several proto-oncogenes and tumour suppressor genes. Furthermore, differentiation, maintenance, expansion and drug resistance of MM cells are dependent on multiple growth factors, cytokines, and chemokines, secreted by tumour cells, bone marrow stromal cells, and non-haematopoietic organs; as well as on direct tumour cell-stromal cell contact. Therefore, signalling pathways initiated by both mutated genes in MM cells as well as signals originating in the bone marrow microenvironment represent potential targets for intervention. Close collaboration between basic researchers and clinicians will be required to further improve our knowledge of MM pathophysiologically in order to translate advances from the bench to the bedside and improve patient outcome.

B cell proliferation following CD40 stimulation results in the expression and activation of Src protein tyrosine kinase

Resting normal human B cells express negligible c-src mRNA or Src protein tyrosine kinase; however, upon induction of proliferation, these cells express high levels of both mRNA and protein and show a concomitant increase in tyrosine kinase activity of immunoprecipitated Src. Src expression was most pronounced upon stimulation with CD154, and to a lesser extent CD70, Staphylococcus aureus, Cowan strain I and phorbol ester, and correlated with the activation of the cells. Transfection of cDNA for human wild-type or kinase-dead Src into Raji B cells resulted in an increase and decrease, respectively, of the cell numbers in culture, showing a direct correlation of proliferation to the expression of Src that was corroborated using anti-sense oligodeoxynucleotides and chemical inhibitors. Furthermore, the human B cell lines, Namalwa, Daudi and Raji express low levels of Src but express very high levels of Src after stimulation with CD154 that showed a correlation with increased activation. This is the first report of Src detectable in normal B cells. The finding that Src expression is inducible and correlates with stimulation by CD154 and the proliferation of the B cells suggests that Src may play a specific role in normal and transformed B cell activation/proliferation pathways mediated primarily through CD40 stimulation.