Bone Marrow Histopathological and Molecular Changes of Small B-Cell Lymphomas after Rituximab Therapy: Comparison with Clinical Response and Patients' Outcome

Immunohistochemical CD20-negative change in B-cell non-Hodgkin lymphomas after rituximab-containing therapy

CD20^- change after rituximab-containing therapy is considered one of the main reasons of rituximab resistance of B-cell non-Hodgkin lymphomas (B-NHLs). However, the clinicopathological characteristics of B-NHL with CD20^- change are not entirely understood. In this study, 252 B-NHL patients who were CD20⁺ at initial diagnosis, whose diseases relapsed or were refractory after rituximab-containing therapy, and who were re-biopsied between 2000 and 2018, were included. The median number of rituximab administration was 11 (range, 1-48). Completely negative (cCD20^-) and partially negative (pCD20^-) change of CD20 was observed in 49 (20%) and 16 (6%) cases, respectively. Among cCD20^- and pCD20^- cases, 74% and 62% of the cases changed to CD20^- at the second relapse or later, respectively. Overall survival was significantly shorter in cCD20^- follicular lymphoma (FL) cases than in CD20⁺ FL cases. Seven histopathological patterns, such as CD20^- change without histological change, histological transformation (HT) to CD20^- diffuse large B-cell lymphoma, and proliferation of plasmablastic/plasmacytoid tumor cells, were associated with CD20^- change. HT occurred more frequently in FLs with CD20^- change than in FLs continuously expressing CD20 (P < 0.0001), regardless of the timing of HT. Nine out of 25 cases (36%) showed regain or heterogeneous regain of CD20 expression. In conclusion, 20% and 6% of the 252 B-NHL cases show cCD20^- and pCD20^- changes with 7 histological patterns after rituximab-containing therapy. Because changes in morphology and CD20 expression after rituximab-containing therapy vary, and recovery of CD20 expression is not rare, careful follow-up and re-biopsy in B-NHL patients are recommended.

Involvement of NK Cells against Tumors and Parasites

Host resistance against pathogens depends on a complex interplay of innate and adaptive immune mechanisms. Acting as an early line of defence, the immune system includes activation of neutrophils, tissue macrophages, monocytes, dendritic cells, eosinophils and natural killer (NK) cells. NK cells are lymphoid cells that can be activated without previous stimulation and are therefore like macrophages in the first line of defence against tumor cells and a diverse range of pathogens. NK cells mediate significant activity and produce high levels of proinflammatory cytokines in response to infection. Their cytotoxicity production is induced principally by monocyte-, macrophage- and dendritic cell-derived cytokines, but their activation is also believed to be cytokine-mediated. Recognition of infection by NK cells is accomplished by numerous activating and inhibitory receptors on the NK cells’ surface that selectively trigger the cytolytic activity in a major histocompability complex-independent manner. NK cells have trypanocidal activity of fibroblast cells and mediate direct destruction of extracellular epimastigote and trypomastigote forms of T. cruzi and T. lewisi in vitro; moreover, they kill plasmodia-infected erythrocytes directly through cell-cell interaction. This review provides a more detailed analysis of how NK cells recognize and respond to parasites and how they mediate cytotoxicity against tumor cells. Also the unique role of NK cells in innate immunity to infection and the relationship between parasites and carcinogenesis are discussed.

Waldenström's macroglobulinemia: Two malignant clones in a monoclonal disease? Molecular background and clinical reflection

Waldenström's macroglobulinemia (WM) is a complex disease characterized by apparent morphological heterogeneity within the malignant clonal cells representing a continuum of small lymphocytes, plasmacytoid lymphocytes, and plasma cells. At the molecular level, the neoplastic B cell-derived clone has undergone somatic hypermutation, but not isotype switching, and retains the capability of plasmacytic differentiation. Although by classical definition, WM is formed by monoclonal expansion, long-lived clonal B lymphocytes are of heterogeneous origin. Even more, according to current opinion, plasma cells also conform certain population with pathogenic and clinical significance. In this article, we review the recent advances in the WM clonal architecture, briefly describe B-cell development during which the molecular changes lead to the malignant transformation and mainly focus on differences between two principal B-lineage clones, including analysis of their genome and transcriptome profiles, as well as immunophenotype features. We assume that the correct identification of a number of specific immunophenotypic molecular and expression alterations leading to proper aberrant clone detection can help to guide patient monitoring throughout treatment and successfully implement therapy strategies directed against both B- and plasma cell tumor WM clones.

Preclinical models of Waldenström's macroglobulinemia and drug resistance

Newer therapeutic strategies are emerging in Waldenström's Macroglobulinemia (WM), which has traditionally been an orphan disease diagnosis. Ibrutinib, a Bruton's tyrosine kinase (BTK) inhibitor was FDA-approved in 2015 as the first ever drug for the treatment of WM. This being a targeted therapy, has given rise to increased research into novel agents and pathways that can be exploited for clinical benefit in WM. In order to understand the underlying mechanisms of disease behavior as well as to test the benefit of various drugs, appropriate preclinical models are required. Historically there had been a lack of representative preclinical models in WM, but in recent years this has dramatically changed. This review highlights the currently available preclinical models and data regarding drug resistance pathways in WM. Knowledge from these will certainly help in paving the future course of treatment in this rare disorder which is indolent and yet, so far incurable.

Immunophenotyping of Waldenströms macroglobulinemia cell lines reveals distinct patterns of surface antigen expression: potential biological and therapeutic implications

Waldenströms macroglobulinemia (WM) is a subtype of Non-Hodgkin's lymphoma in which the tumor cell population is markedly heterogeneous, consisting of immunoglobulin-M secreting B-lymphocytes, plasmacytoid lymphocytes and plasma cells. Due to rarity of disease and scarcity of reliable preclinical models, many facets of WM molecular and phenotypic architecture remain incompletely understood. Currently, there are 3 human WM cell lines that are routinely used in experimental studies, namely, BCWM.1, MWCL-1 and RPCI-WM1. During establishment of RPCI-WM1, we observed loss of the CD19 and CD20 antigens, which are typically present on WM cells. Intrigued by this observation and in an effort to better define the immunophenotypic makeup of this cell line, we conducted a more comprehensive analysis for the presence or absence of other cell surface antigens that are present on the RPCI-WM1 model, as well as those on the two other WM cell lines, BCWM.1 and MWCL-1. We examined expression of 65 extracellular and 4 intracellular antigens, comprising B-cell, plasma cell, T-cell, NK-cell, myeloid and hematopoietic stem cell surface markers by flow cytometry analysis. RPCI-WM1 cells demonstrated decreased expression of CD19, CD20, and CD23 with enhanced expression of CD28, CD38 and CD184, antigens that were differentially expressed on BCWM.1 and MWCL-1 cells. Due to increased expression of CD184/CXCR4 and CD38, RPCI-WM1 represents a valuable model in which to study the effects anti-CXCR4 or anti-CD38 targeted therapies that are actively being developed for treatment of hematologic cancers. Overall, differences in surface antigen expression across the 3 cell lines may reflect the tumor clone population predominant in the index patients, from whom the cell lines were developed. Our analysis defines the utility of the most commonly employed WM cell lines as based on their immunophenotype profiles, highlighting unique differences that can be further studied for therapeutic exploit.

Novel and emerging targeted-based cancer therapy agents and methods

After several decades of uncovering the cancer features and following the improvement of therapeutic agents, however cancer remains as one of the major reasons of mortality. Chemotherapy is one of the main treatment options and has significantly improved the overall survival of cancer patients, but chemotherapeutic agents are highly toxic for normal cells. Therefore, there is a great unmet medical need to develop new therapeutic principles and agents. Targeted-based cancer therapy (TBCT) agents and methods have revolutionized the cancer treatment efficacy. Monoclonal antibodies (mAbs) and small molecule inhibitors (SMIs) are among the most effective agents of TBCT. These drugs have improved the prognosis and survival of cancer patients; however, the therapeutic resistance has subdued the effects. Several mechanisms lead to drug resistance such as mutations in the drug targets, activation of compensatory pathways, and intrinsic or acquired resistance of cancer stem cells. Therefore, new modalities, improving current generation of inhibitors and mAbs, and optimizing the combinational therapy regimens are necessary to decrease the current obstacles in front of TBCT. Moreover, the success of new TBCT agents such as mAbs, SMIs, and immunomodulatory agents has sparked further therapeutic modalities with novel targets to inhibit. Due to the lack of cumulative information describing different agents and methods of TBCT, this review focuses on the most important agents and methods of TBCT that are currently under investigation.

Persistent monotypic plasma cells with absence of neoplastic B cell component in a treated case of waldenström macroglobulinemia: a sign of residual disease?

Waldenström macroglobulinemia (WM) is a rare indolent variant of non- Hodgkin's lymphoma characterised by lymphoplasmacytic infiltration of bone marrow (BM) associated with a serum IgM paraprotein. The WHO classification states that the neoplastic cells of WM usually are positive for monotypic surface immunoglobulin light chain, IgM, CD19, and CD20 and are negative for CD5, CD10, and CD23. Serum monoclonal protein detection by serum protein electrophoresis and bone marrow aspirate and biopsy are required for WM diagnosis, monitoring and response assessment. Pathologist must dissuade themselves from making a hasty decision on calling a complete response in WM when neoplastic B cell component is absent. Evaluation of clonality of any residual plasma cells must be done in all cases of WM to evaluate the presence and extent of residual or persistent disease. Role of additional therapy targeted at these residual plasma cells in WM can be evaluated as tools for achieving complete remission. Herein, we present a case of WM with residual monotypic plasmacytosis in BM, without B lymphocytes after therapy.

Follow-up data of 10 patients with B-cell non-Hodgkin lymphoma with a CD20-negative phenotypic change after rituximab-containing therapy

Recently, a CD20-negative phenotypic change in CD20-positive B-cell non-Hodgkin lymphoma (B-NHL) after rituximab therapy was described. We report the follow-up data of 10 B-NHL patients showing this change after rituximab therapy. Ten patients (4 men and 6 women; median age, 57 y) with B-NHL who were initially CD20 positive and became CD20 negative after rituximab therapy were analyzed. Clinicopathologic features, including clinical course, CD20 expression, and histopathology, were examined. CD20 expression in lymphoma cells was evaluated using immunohistochemistry and/or flow cytometry. Histopathologically, diagnosis at initial presentation was follicular lymphoma (FL) in 7 patients; diffuse large B-cell lymphoma in 1; and chronic lymphocytic leukemia in 2. Six patients (60%, 3 FL, 1 diffuse large B-cell lymphoma, and 2 chronic lymphocytic leukemia patients) showed continuous CD20 negativity until 24 months after the phenotypic change. Three patients (30%) with FL regained CD20 expression within 1 to 7 months after detection of the CD20 change. Two patients (20%) with FL, including 1 who regained CD20 expression, showed heterogenous CD20 expression with a CD20-negative low-grade component and a CD20-positive large cell component. The overall response rate to therapy before the CD20-negative change was 70%. We reported the follow-up data of 10 B-NHL patients with a CD20-negative phenotypic change associated with rituximab-containing therapy. The most common histologic phenotypes were continuous CD20 negativity, recovery of CD20 expression within 7 months, and heterogenous CD20 expression. As the changes in morphology and CD20 expression after rituximab therapy vary widely, careful follow-up and rebiopsy are recommended.

Anti-CD20 monoclonal antibodies in chronic lymphocytic leukemia

INTRODUCTION

The last decade has witnesd immense progress in the treatment of chronic lymphocytic leukemia (CLL). Chemoimmunotherapy (CIT) combining rituximab and fludarabine with cyclophosphamide (FCR) in the frontline setting has clearly been shown to improve outcomes in patients with CLL. Building on the success achieved with rituximab, other anti-CD20 monoclonal antibodies (mAbs) are being investigated. Novel bioengineering techniques have helped in the development of anti-CD20 mAbs. One antibody, ofatumumab, was recently approved for the treatment of refractory CLL. A type II anti-CD20 mAb, GA-101 (obinutuzumab), is currently in clinical trials. This short review focuses on ongoing clinical trials of anti-CD20 mAbs in CLL.

AREAS COVERED

Literature search was performed using PubMed ( www.clinicaltrials.gov (till August 2012)), and recent American Society of Clinical Oncology (ASCO), American Society of Hematology (ASH), European Hematology association (EHA), International workshop on CLL (iwCLL) abstracts, using the primary search terms 'anti-CD20 monoclonal antibody' with/without CLL. Articles were chosen on the basis of relevance of anti-CD20 mAbs to CLL therapy.

EXPERT OPINION

Rituximab, the prototype anti-CD20 mAb, forms the core of CIT in CLL. The success of rituximab and ofatumumab has led investigators to evaluate other anti-CD20 mAbs in the treatment of CLL.

The pan-deacetylase inhibitor panobinostat modulates the expression of epithelial-mesenchymal transition markers in hepatocellular carcinoma models

Deacetylase inhibitors (DACis) represent a novel therapeutic option for human cancers by classically affecting proliferation or apoptosis. Since transdifferentiation and dedifferentiation play a key role in carcinogenesis, we investigated the epigenetic influence on the molecular differentiation status in human hepatocellular carcinoma (HCC) models. Markers of differentiation, including cytokeratin (Ck) 7, Ck8, Ck18, Ck19, Ck20, vimentin, sonic hedgehog homolog (SHH), smoothened (Smo), patched (Ptc), glioma-associated oncogene homolog 1 (Gli1), CD133, octamer-binding transcription factor 4 (Oct4) and β-catenin, were examined in the human HCC cell lines HepG2 and Hep3B in vitro and in vivo (xenograft model) using quantitative real-time PCR and immunohistochemistry following treatment with the pan-DACi panobinostat (LBH589). Compared to untreated controls, treated HepG2 xenografts, and to a lesser extent cell lines, demonstrated a significant increase of differentiation markers Ck7 and Ck19 (classical cholangiocellular type) and Ck8 and Ck18 (classical HCC type), and a decreased level of dedifferentiation markers vimentin (mesenchymal) and SHH/Ptc (embryonic), paralleled with a more membranous expression of β-catenin. These findings were dose-dependently correlated with tumor size, necrosis rate, microvessel density and mitosis/Ki-67-associated proliferation rate. Our results demonstrate that the differentiation status of human HCC cells is influenced by the pan-DACi panobinostat, indicating that this treatment may influence the epithelial-mesenchymal transition (EMT) status related to metastasis and aggressiveness.

Obinutuzumab for the treatment of lymphoproliferative disorders

INTRODUCTION

Targeted therapy against CD20 with the mAb rituximab has led to significant improvements in survival for patients with B-cell non-Hodgkin's lymphoma (NHL). Despite these improvements, many patients relapse and/or become refractory after rituximab-containing therapies and thus better therapies are required for NHL.

AREAS COVERED

Obinutuzumab is a novel, humanized, anti-CD20 mAb currently being investigated in Phase III studies in comparison to rituximab. An overview of obinutuzumab, its mechanisms of action and the results of pre-clinical and Phase I/II studies are presented.

EXPERT OPINION

Pre-clinical studies suggest that obinutuzumab is a more potent anti-CD20 mAb than Rituximab at inducing antibody-dependent cellular cytotoxicity (ADCC) and direct cell death (DCD). Obinutuzumab is safe and effective in CD20 + NHL and further study is warranted. Results of ongoing Phase III clinical trials comparing Obinutuzumab to Rituximab in different disease settings and with different chemotherapy regimens are eagerly awaited.

Residual monotypic plasma cells in patients with waldenstrom macroglobulinemia after therapy

Waldenström macroglobulinemia (WM) is currently defined as lymphoplasmacytic lymphoma involving bone marrow (BM) associated with a serum IgM paraprotein. WM is typically composed of small lymphocytes, plasmacytoid lymphocytes, and plasma cells in variable proportions, which can change after therapy. In this study, we assessed 41 WM cases that required chemotherapy, 39 showing persistent disease in restaging BM specimens. In 10 cases, there was persistent monotypic plasmacytosis in BM in the absence of demonstrable monotypic B cells. The monotypic plasma cells represented 0.5% to 46% of the cellularity and persisted 1 to 50 months after the last course of chemotherapy. The plasma cells were best quantified by immunohistochemical analysis on paraffin sections. We conclude that WM can persist as a pure plasma cell population after therapy. This finding has implications for the immunophenotypic assessment of WM after therapy and may explain persistent IgM paraproteinemia in patients with WM with no evidence of a clonal B-lymphocyte population.

Antigenic modulation and rituximab resistance

Several types of B-cell lymphoma have been successfully treated with rituximab, and approval by the US Food and Drug Administration for use of rituximab in the treatment of rheumatoid arthritis has increased interest in targeting CD20 on B cells for other indications. Although large amounts of rituximab can be infused into humans with no apparent dose-limiting toxicity, recent evidence suggests that the body's effector mechanisms, including complement-mediated cytotoxicity and natural killer (NK) cell-mediated killing, can be saturated or exhausted at high burdens of rituximab-opsonized B cells. One of the consequences of this saturation phenomenon is that the opsonized B cells are instead processed by a different pathway mediated by FcgammaR on effector cells. In this alternative pathway, both rituximab and CD20 are removed ("shaved") from the B cells and are taken up by monocytes/macrophages. This process, formerly called antigenic modulation, appears to occur in several compartments in the body and may play a key role in the development of resistance to rituximab therapy.

Down-regulation of CD20 expression in B-cell lymphoma cells after treatment with rituximab-containing combination chemotherapies: its prevalence and clinical significance

Although rituximab is a key molecular targeting drug for CD20-positive B-cell lymphomas, resistance to rituximab has recently been recognized as a considerable problem. Here, we report that a CD20-negative phenotypic change after chemotherapies with rituximab occurs in a certain number of CD20-positive B-cell lymphoma patients. For 5 years, 124 patients with B-cell malignancies were treated with rituximab-containing chemotherapies in Nagoya University Hospital. Relapse or progression was confirmed in 36 patients (29.0%), and a rebiopsy was performed in 19 patients. Of those 19, 5 (26.3%; diffuse large B-cell lymphoma [DLBCL], 3 cases; DLBCL transformed from follicular lymphoma, 2 cases) indicated CD20 protein-negative transformation. Despite salvage chemotherapies without rituximab, all 5 patients died within 1 year of the CD20-negative transformation. Quantitative reverse-transcription-polymerase chain reaction (RT-PCR) showed that CD20 mRNA expression was significantly lower in CD20-negative cells than in CD20-positive cells obtained from the same patient. Interestingly, when CD20-negative cells were treated with 5-aza-2'-deoxycytidine in vitro, the expression of CD20 mRNA was stimulated within 3 days, resulting in the restoration of both cell surface expression of the CD20 protein and rituximab sensitivity. These findings suggest that some epigenetic mechanisms may be partly related to the down-regulation of CD20 expression after rituximab treatment.

Histological and immunophenotypic changes in 59 cases of B-cell non-Hodgkin's lymphoma after rituximab therapy

Rituximab is a chimeric monoclonal antibody that recognizes the CD20 antigen. It has been used to treat B-cell non-Hodgkin lymphoma (B-NHL), but recently rituximab resistance has been a cause for concern. We examined histological and immunohistochemical changes in 59 patients with B-NHL after rituximab therapy. The patients comprised 32 men and 27 women with a median age of 59 years. Pre-rituximab specimens comprised 34 follicular lymphomas (FL), 11 diffuse large B-cell lymphomas (DLBCL), 10 mantle cell lymphomas, two marginal zone B-cell lymphomas (MZBCL), and two chronic lymphocytic leukemias (CLL). CD20 expression in lymphoma cells was evaluated by immunohistochemistry or flow cytometry. Post-rituximab materials were taken a median of 6 months (4 days to 59 months) after rituximab therapy. Sixteen cases (27%) showed loss of CD20 expression with four histological patterns: pattern 1, no remarkable histological change (FL, 5; DLBCL, 3; and CLL, 2); pattern 2, proliferation of plasmacytoid cells (FL, 2; DLBCL, 1; and MZBCL, 1); pattern 3, transformation to classical Hodgkin's lymphoma (FL, 1); and pattern 4, transformation to anaplastic large cell lymphoma-like undifferentiated lymphoma (FL, 1). Loss of CD20 was unrelated to the interval of biopsies, treatment regimen, clinical response, and frequency of rituximab administration. Loss of CD20 within 1 month of rituximab therapy (3/14, 21%) and regain of CD20 (2/7, 29%) were not frequent. CD20-positive relapse with transformation occurred most frequently in cases of early relapse. In conclusion, B-NHL showed various histological and immunophenotypic changes after rituximab therapy, including not only CD20 loss but also proliferation of plasmacytoid cells or transformation to special subtypes of lymphoma.