Cell fusion is not involved in the generation of giant cells in the Hodgkin-Reed Sternberg cell line L1236

CD30 induces Reed-Sternberg cell-like morphology and chromosomal instability in classic Hodgkin lymphoma cell lines

Classic Hodgkin lymphoma (cHL) is characterized by multinucleated cells called Reed-Sternberg (RS) cells and genetic complexity. Although CD30 also characterizes cHL cells, its biological roles are not fully understood. In this report, we examined the link between CD30 and these characteristics of cHL cells. CD30 stimulation increased multinucleated cells resembling RS cells. We found chromatin bridges, a cause of mitotic errors, among the nuclei of multinucleated cells. CD30 stimulation induced DNA double-strand breaks (DSBs) and chromosomal imbalances. RNA sequencing showed significant changes in the gene expression by CD30 stimulation. We found that CD30 stimulation increased intracellular reactive oxygen species (ROS), which induced DSBs and multinucleated cells with chromatin bridges. The PI3K pathway was responsible for CD30-mediated generation of multinucleated cells by ROS. These results suggest that CD30 involves generation of RS cell-like multinucleated cells and chromosomal instability through induction of DSBs by ROS, which subsequently induces chromatin bridges and mitotic error. The results link CD30 not only to the morphological features of cHL cells, but also to the genetic complexity, both of which are characteristic of cHL cells.

Apoptotic regulator BCL-2 blockade as a potential therapy in classical Hodgkin Lymphoma

The challenge in classical Hodgkin Lymphoma (cHL) management is the 30-40% of refractory/relapsed cases.

AIMS

The aim of this work was to determine whether NIK and BCL-2 could be useful as prognosis biomarkers in cHL. In addition, we evaluated BCL-2 as a directed-therapy in cHL cell lines using venetoclax.

MAIN METHODS

We evaluated NIK and BCL-2 expression in 112 untreated cHL patients' lymph-node biopsies by immunohistochemistry. cHL cell lines were treated with venetoclax alone or combined with vincristine or doxorubicin. Cell viability, metabolic activity and cell death were analyzed by trypan-blue exclusion method, MTS assay and FDA/IP staining respectively.

KEY FINDINGS

No correlation between NIK or BCL-2 expression and the majority of the clinical parameters was found. Patients with ≥60% BCL-2+ HRS-cells had a shorter disease-free survival (DFS) and overall survival (OS) (p = 0.002, p = 0.02 respectively). A decision tree analysis, in a 30 patients subgroup, showed that patients with <60% NIK+ HRS-cells but with ≥60% BCL-2+ HRS-cells had a worse outcome in terms of DFS and OS. These parameters performed better as prognosis indicators as compared to the diagnosis bone marrow status. Human cHL cell lines U-H01, KM-H2, L1236, SUPHD1, L540 showed sensitivity to venetoclax. The co-treatment effect of venetoclax and vincristine or doxorubicin on cell viability was diverse depending on the cell line evaluated.

SIGNIFICANCE

BCL-2 should be considered as a prognosis biomarker as well as a potential new therapeutic target in cHL. We report for the first time the cytotoxic effect of venetoclax in human cHL cell lines.

Reed-Sternberg cells form by abscission failure in the presence of functional Aurora B kinase

Large multinucleated Reed-Sternberg cells (RS) and large mononucleated Hodgkin cells (H) are traditionally considered to be the neoplastic population in classical Hodgkin lymphoma, (cHL) and postulated to promote the disease. However, the contribution of these larger cells to the progression of cHL remains debatable. We used established cHL cell lines and cHL cellular fractions composed of small mononucleated cells only or enriched in large RS/H cells to investigate RS/H cell origin and to characterize the cells which they derive from. We confirm that the small mononucleated cells give rise to RS/H cells, and we show that the latter proliferate significantly more slowly than the small cells. By using live-cell imaging, we demonstrate that binucleated RS cells are generated by failure of abscission when a few small cells attempt to divide. Finally, our results reveal that the small mononucleated cells are chromosomally unstable, but this is unlikely to be related to a malfunctioning chromosomal passenger protein complex. We propose that the small mononucleated cells, rather than the RS/H cells, are the main drivers of cHL.

On the origin of giant cells in Hodgkin lymphoma

Multinucleated giant tumor cells are frequently observed in tissue sections of lymphoma patients. In Hodgkin lymphoma (HL), these cells are pathognomonic for the disease and named Reed-Sternberg (RS) cells. Despite the well-described disease-promoting functions of RS cells, their development has remained obscure. We addressed this open question by continuous live cell imaging to observe the generation of RS cells. Single-cell tracking of HL cell lines revealed that RS cells develop from mononucleated progenitors that divide and subsequently re-fuse, before they grow and become multinucleated giant cells. Thus, RS cell generation is neither due to cell fusion of unrelated Hodgkin cells nor to endomitosis, as previously suggested. In the majority of cases, re-fusion of daughter cells was preceded by an incomplete cytokinesis, visualized by a persistent microtubule bridge connecting the cells. This surprising finding describes a novel mechanism for the formation of multinuclear giant cells with potential relevance beyond HL.

Aurora B kinase in Hodgkin lymphoma: immunohistochemical pattern of expression in neoplastic Hodgkin and Reed-Sternberg cells

Aurora B is a member of the chromosomal passenger complex, which is essential for proper completion of mitosis and cell division (cytokinesis). Inappropriate chromosomal segregation and cytokinesis due to deregulated expression of chromosome passenger proteins may lead to aneuploidy and cancer including lymphomas. According to our knowledge there are extremely limited studies investigating the immunohistochemical expression of Aurora B in tumor specimens of Hodgkin lymphoma. Our purpose was to characterize the expression of Aurora B in biopsies of Hodgkin lymphomas, and to evaluate the pattern of immunoreactivity in neoplastic Hodgkin and Reed-Sternberg cells (RS cells). We examined Aurora B immunoreactivity in paraffin sections of 15 samples of Hodgkin lymphomas, obtained from 15 patients, 8 men and 7 women. Ten were of nodular sclerosis type and five were of mixed cellularity. Our results showed immunoexpression of Aurora B in mononuclear lymphoid cells as well as in bi- and multinucleated RS cells. In addition, positive neoplastic cells in mitosis were observed, whereas a subpopulation without evidence of immunoreaction was also detected in each case. Taken together our results point to a possible association between Aurora B expression and mitotic deregulation in Hodgkin lymphoma, which may provide novel targets for treatment.

Incomplete cytokinesis and re-fusion of small mononucleated Hodgkin cells lead to giant multinucleated Reed-Sternberg cells

Multinucleated Reed-Sternberg (RS) cells are pathognomonic for classical Hodgkin lymphoma (HL), and their presence is essential for diagnosis. How these giant tumor cells develop is controversial, however. It has been postulated that RS cells arise from mononucleated Hodgkin cells via endomitosis. Conversely, continuous single-cell tracking of HL cell lines by long-term time-lapse microscopy has identified cell fusion as the main route of RS cell formation. In contrast to growth-induced formation of giant Hodgkin cells, fusion of small mononuclear cells followed by a size increase gives rise to giant RS cells. Of note, fusion of cells originating from the same ancestor, termed re-fusion, is seen nearly exclusively. In the majority of cases, re-fusion of daughter cells is preceded by incomplete cytokinesis, as demonstrated by microtubule bonds among the cells. We confirm at the level of individual tracked cells that giant Hodgkin and RS cells have little proliferative capacity, further supporting small mononuclear Hodgkin cells as the proliferative compartment of the HL tumor clone. In addition, sister cells show a shared propensity for re-fusion, providing evidence of early RS cell fate commitment. Thus, RS cell generation is related neither to cell fusion of unrelated Hodgkin cells nor to endomitosis, but rather is mediated by re-fusion of daughter cells that underwent mitosis. This surprising finding supports the existence of a unique mechanism for the generation of multinuclear RS cells that may have implications beyond HL, given that RS-like cells are frequently observed in several other lymphoproliferative diseases as well.

Multinucleation followed by an acytokinetic cell division in myxofibrosarcoma with giant cell proliferation

Background

Multinucleated cells are frequently seen in association with a malignant neoplasm. Some of these multinucleated cells are considered to be neoplastic. The mechanism of neoplastic multinucleation remains unknown, but is considered to be induced by either cell-cell fusion or acytokinetic cell division. Myxofibrosarcoma consists of spindled and pleomorphic tumor cells and bizarre multinucleated giant cells. Some of these multinucleated cells are considered to be neoplastic.

Methods

We studied the mitotic activity of the multinucleated cells by Ki-67 immunohistochemistry, and the dynamics and differentiation by live-cell video microscopy in the two myxofibrosarcoma cell lines to determine whether the mechanism of multinucleation is cell-cell fusion or acytokinetic cell division

Results

A Ki-67 immunohistochemical analysis revealed a high positive rate of multinucleated cells, as well as mononuclear cells, and mitotic ability was shown in the multinucleated cells. In live-cell video microscopy, most of the multinucleated cells were induced via the process of acytokinetic cell division.

Conclusion

The current study indicates that a vulnerability of the cytoskeleton components, such as the contractile ring, causes multinucleation to occur from the telophase to the cytokinesis of the cell cycle.

The 3D nuclear organization of telomeres marks the transition from Hodgkin to Reed-Sternberg cells

To get an insight into the transition from mononuclear Hodgkin cells (H cells) to diagnostic multinuclear Reed-Sternberg cells (RS cells), we performed an analysis of the three-dimensional (3D) structure of the telomeres in the nuclei of the Hodgkin cell lines HDLM-2, L-428, L-1236 and lymph node biopsies of patients with Hodgkin's disease. Cellular localization of key proteins of the telomere-localized shelterin complex, the mitotic spindle and double-stranded DNA breaks was also analyzed. RS cells show significantly shorter and significantly fewer telomeres in relation to the total nuclear volume when compared with H cells; in particular, telomere-poor 'ghost' nuclei are often adjacent to one or two nuclei displaying huge telomeric aggregates. Shelterin proteins are mainly cytoplasmic in both H and RS cells, whereas double-stranded DNA breaks accumulate in the nuclei of RS cells. In RS cells, multipolar spindles prevent proper chromosome segregation. In conclusion, a process of nuclear disorganization seems to initiate in H cells and further progresses when the cells turn into RS cells and become end-stage tumor cells, unable to divide further because of telomere loss, shortening and aggregate formation, extensive DNA damage and aberrant mitotic spindles that may no longer sustain chromosome segregation. Our findings allow a mechanistic 3D understanding of the transition of H to RS cells.

Proliferative index and CD15 expression in pediatric classical Hodgkin lymphoma

BACKGROUND

This study was conducted to assess the clinical and prognostic significance of lack of CD15 expression, proliferative index (PI), and expression of tumor suppressor protein p53 in pediatric classical Hodgkin lymphoma (CHL).

PROCEDURE

Pre-treatment lymph node (LN) biopsies were studied by immunohistochemistry for immunophenotyping of the lymphoma and with Ki-67 (PI) and p53 antibodies. Expression of CD15 antigen on the Hodgkin and Reed-Sternberg (H-RS) cells, proliferation, and apoptosis parameters were correlated with clinical stage, response to chemotherapy alone, overall (OS) and failure-free survival (FFS).

RESULTS

One hundred and twenty-one children with CHL were studied. Expression of Ki-67 and p53 in H-RS cells was seen in 100% and 89.9% of the cases, respectively. Loss of CD15 expression, seen in 12 (9.9%) cases, was significantly associated with p53 negativity and was an independent prognostic factor for poor OS and poor FFS. PI </= 74% was an independent prognostic factor for poor FFS.

CONCLUSIONS

Loss of CD15 expression in CHL might be related to p53 dysregulation. High PI in HL might reflect a high level of endomitosis within tumor cells, and could lead to higher sensitivity to chemotherapy. Low pre-treatment PI and lack of CD15 expression were found to be predictive factors for poor FFS in pediatric CHL.

Pathobiology of Classical Hodgkin Lymphoma

The World Health Organization has acknowledged the malignant nature of classical Hodgkin lymphoma (cHL), which encompasses four histological subtypes. The diagnosis of cHL is based on the detection of malignant Hodgkin and Reed-Sternberg cells (HRSC) confirmed by immunophenotyping and the detection of growth patterns specific to each histological subtype. The pathologic HRSC arise from germinal center or immediate postgerminal cells that lack detectable immunoglobulin/B-cell antigen receptor expression, with a consequent loss of B-cell identity; very few cHL cases are of T-cell origin. To escape apoptosis, which normally occurs in B cells with nonfunctioning antigen receptor machinery, HRSC develop concurrent antiapoptotic mechanisms by activation of nuclear factor-kappaB or are rescued by Epstein-Barr virus infection. HRSC are characterized by a variable and inconstant immunophenotype, with a remarkable loss of lineage-specific cell antigens and expression of antigens of other cell lineages. The master plan of B-cell identity in HRSC is disturbed not only at the immunoglobulin expression level, but also at the transcriptional factor level. HRSC are further characterized by profound cell cycle deregulation with futile replication, multinucleation and poly- and aneuploidy. Here, we review pathobiological aspects of cHL with respect to lymphomagenesis and routine diagnostics.

A notable phenomenon recapitulated. A fusion product of a murine lymphoma cell and a leukemia virus-neutralizing antibody-producer host plasma cell formed spontaneously and secreting the specific antibody continuously

In the mid-1960s the #620 cell passage line of a murine lymphoma-leukemia was developed at the Section of Clinical Tumor Virology and Immunology, Department of Medicine, The University of Texas M.D. Anderson Hospital in Houston, TX. The diploid lymphoma cells released a retrovirus and were antigenic in young adult Swiss (YAS) mice. Small lymphoma cell inocula were rejected with immunity acquired against large inocula of lymphoma cells. Tissue sections revealed the "starry sky" configurations. In one of the tissue cultures set up from lymphoma #620, a cell line consisting of large round poly- or tetraploid cells arose and was referred to as lymphoma cell line #818. The #818 cells grew in suspension cultures and in the form of large, lethal ascitic tumors in YAS mice. Diploid #620 lymphoma cells stained for retroviral antigens; #818 cells stained both for retroviral antigens and immunoglobulins. Fluids withdrawn from #818 cultures neutralized the leukemia virus in spleen focus assays. Immunoglobulin precipitated from #818 suspension culture fluids strongly and specifically neutralized the leukemia virus. The growth of #620 or #818 cells in YAS mice treated with rabbit anti-lymphoma cell immune sera was strongly inhibited but culture fluids of #818 cells showed weak and insignificant inhibition against leukemia-lymphoma #620 (in one experiment, unpublished). In two experiments #620 lymphoma cells were co-inoculated with immune spleen cells into the peritoneal cavities of YAS mice. The immune spleen cells derived from mice that rejected #620 cell inocula or were actively immunized with a photodynamically inactivated mouse leukemia virus vaccine. In the peritoneal cavities of mice co-inoculated with #620 cells and immune spleen cells, clones of large round cells emerged with tetra- or polyploid chromosomal modes. These cells stained for leukemia viral antigens and immunoglobulins. When passaged in YAS mice these cells induced lethal ascites tumors. It was concluded as early as in 1968-69 that an immune plasma cell can fuse with a lymphoma cell, if the lymphoma cell expresses retroviral antigens against which the plasma cell is producing a specific antibody. Some human lymphoma-leukemia cells express retroviral antigens and/or budding retroviral particles, whether due to the acquisition of new env sequences by incomplete resident endogenous retroviral genomes or due to the entry of exogenous retroviruses into lymphopoietic stem cells. In the Discussion illustrations are provided for the human cell line #778 established from a patient with "lymphosarcoma cell leukemia" in 1966. The malignant cells released unidentified retrovirus-like particles and fused with one another and with reactive lymphoid cells of the host. It should be investigated further if human lymphoma-leukemia cells could fuse with an immune plasma cell of the host and thus alter the clinical course of the disease.

T-bet, a T cell-associated transcription factor, is expressed in Hodgkin's lymphoma

T-bet, a T-box transcription factor, is expressed in CD4+ T lymphocytes committed to Th1 T-cell development and may participate in immunoglobulin class switching in B lymphocytes. T-bet is also expressed in a subset of T-cell lymphomas, particularly those that express other markers of Th1 T cell differentiation, and in a subset of B-cell non-Hodgkin's lymphomas. Because of the evidence that Hodgkin's lymphoma is a neoplasm of B cells, we examined cases of Hodgkin's lymphoma for T-bet expression by immunohistochemical staining and found that neoplastic cells in most cases of classic Hodgkin's lymphoma (33 of 37 cases, 89%), including nodular sclerosis type (17 of 21 cases, 81%) and mixed cellularity type (15 of 15, 100%), express T-bet. Neoplastic cells in most cases of nodular lymphocyte-predominant Hodgkin's lymphoma (15 of 18, 83%), a distinct clinical entity that differs from classic Hodgkin's lymphoma, also express T-bet. A Hodgkin's lymphoma-derived cell line, L1236, expresses T-bet by Western blot analysis as well as by immunohistochemical staining. In contrast, almost all cases of diffuse large B-cell lymphoma and most cases of anaplastic large cell lymphoma, neoplasms that may be confused with Hodgkin's lymphoma, are negative for T-bet. On that basis, T-bet should serve as a useful new marker for the diagnosis of Hodgkin's lymphoma. In addition, because T-bet expression is not detectable in the majority of reactive B cells, including germinal-center B cells, but is characteristically expressed by the neoplastic cells in Hodgkin's lymphoma, thought to be derived from germinal-center B cells, T-bet may play a role in Hodgkin's lymphoma oncogenesis.

A two-colour fluorescence assay for the measurement of syncytial fusion between trophoblast-derived cell lines

Syncytial fusion is a key event in implantation and placentation. Its regulation is only poorly understood. We present a cell-cell fusion assay based on staining of cells in two portions with a green and a red fluorescent cytoplasmic dye that become intracellularly mixed only after syncytial fusion. We quantified cell-cell fusion by fluorescence microscopy in choriocarcinoma cell lines BeWo, JAR and JEG3 and in some non-trophoblastic cell lines and found clear differences in fusion behaviour. Only BeWo cells fused with each other, while the other cell lines tested did not. BeWo cells also fused with all other cell lines tested. The efficiency of cell-cell fusion of BeWo cells was stimulated by forskolin. We tried to correlate messenger levels of syncytin and its receptor RDR with the fusion index of choriocarcinoma cells. BeWo and JAR cells contained readily detectable and forskolin-inducible levels of syncytin mRNA, whereas this messenger was barely detectable in JEG3 cells. RDR transcript levels were similar in all cell lines tested and were unaffected by forskolin treatment. The data suggests that the expression of syncytin and RDR messengers alone does not guarantee successful fusion. The fusion assay presented in this paper is a useful tool to study syncytial fusion in an accurate and quantitative way.

Endoreduplication in conjunction with tumor progression in an aneuploid laryngeal squamous cell carcinoma

We report the case of a 58-year-old man who presented with a squamous cell carcinoma pT1a G2 of the left vocal cord. Six months after histologically verified complete resection, the patient experienced an endolaryngeal and extralaryngeal local recurrence pT4 pN2b G2. We applied DNA flow cytometry (FCM) and comparative genomic hybridization (CGH) on both primary and recurrent tumor. The primary tumor and the endolaryngeal compartment of the relapse was an aneuploid cell clone with a FCM DNA index of 1.42 and 1.44, respectively. The extralaryngeal compartment showed a shift featuring a DNA index of 2.78. In the primary tumor and in both compartments of the recurrence there was an identical pattern of complex chromosomal imbalances as detected in CGH (CGH karyotype: rev ish enh [8q24.2-q24.3, 10q26.1-q26.3, 11q24-q25, 12q24.2-q23.33,X], dim [4q, 13q14.3-q31], amp[1p36.1-p36.2]). Hence, the recurrence was not associated with further gains and losses of chromosomal material. However, in the anterior part of the recurrence, the aneuploid tumor cell genome had completely doubled, obviously due to endoreduplication. Immunohistochemical analysis of several cell-cycle regulators revealed altered expression of checkpoint proteins, pointing to a complex disturbance in cell-cycle regulation.

Genetic instability in Hodgkin's lymphoma

Genetic instability is a characteristic feature of the malignant Hodgkin and Reed-Sternberg (HRS) cells in classical Hodgkin's lymphoma and the lymphocytic and histiocytic (L&H) cells in lymphocyte predominant Hodgkin's lymphoma. Genetic instability can be classified into four major categories: distinct DNA mutations (microsatellite instability); numerical aberrations (chromosomal instability); structural aberrations (translocation instability); and gains and losses of chromosomal regions. In Hodgkin's lymphoma (HL), HRS cells and L&H cells show somatically mutated clonally rearranged immunoglobulin genes, thus characterizing these cells genetically as germinal center B cells. These cells furthermore show mutations of oncogenes and tumor suppressor genes in some cases (p53, IkappaBalpha, CD95/Fas). They do not, however, display microsatellite instability, as they have a proficient mismatch repair machinery. In contrast, HRS and L&H cells frequently harbor recurrent but not specific numerical and structural aberrations as detected by classical cytogenetics and fluorescence in situ hybridization analysis. Results from molecular genetic studies using comparative genomic hybridization and allelotyping (LOH) indicate typical genetic patterns in HL with gains and losses of distinct chromosomal regions. In some instances, candidate genes possibly involved in the malignant transformation of HRS cells and L&H cells have been characterized (JAK2, c-REL, MDM2). In summary, using molecular genetics it might be possible in the near future to elucidate some of the complex genetic instabilities observed in HL.

Biology of Hodgkin's lymphoma

Significant progress has been made in recent years in our understanding of the cellular origin of Hodgkin and Reed-Sternberg (HRS) cells in Hodgkin's lymphoma (HL). It is now clear that in most instances HRS cells represent clonal populations of transformed germinal centre (GC) B cells. While the tumour cells in the lymphocyte predominant type of the disease resemble mutating and antigen-selected GC B cells, there is evidence that HRS cells in classical HL originate from pre-apoptotic GC B cells. HRS cells of the recently defined novel subtype lymphocyte-rich classical HL moleculary resemble HRS cells of the other types of classical HL, but there appear to be phenotypic differences. In rare cases, HRS cells derive from T cells. In contrast to previous speculations, cell fusion apparently does not play a role in the generation of the tumour clone. By gene expression profiling of HL cell lines, it became evident that HRS cells have lost most of the B cell-typical gene expression program, which may explain why these cells can persist without B cell receptor expression and which suggests that at least one of the transforming events involved in HL pathogenesis affects a master regulator of cell lineage identity.