Growth vs. DNA strand breaks in Hodgkin's disease: impaired proliferative ability of Hodgkin and Reed-Sternberg cells

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.

Hodgkin lymphoma: an update on its biology with new insights into classification

In the past few years, there has been a greater understanding of the spectrum and biology of Hodgkin lymphoma (HL). In standard texts, HL is classified as 2 distinct entities, namely nodular lymphocyte-predominant HL and classical HL (CHL). However, recent evidence suggests that CHL is not a single disease. Although the mixed cellularity and lymphocyte-depleted subtypes might be part of a biologic continuum, the nodular sclerosis subtype has a distinct epidemiology, clinical presentation, and histology. Nodular sclerosis HL might also be related to primary mediastinal B-cell lymphoma and mediastinal gray-zone lymphomas. We present an update on the pathobiology of HL and discuss these biologic and clinical differences in this review.

Expression of cyclooxygenase-2 in Hodgkin's lymphoma: its role in cell proliferation and angiogenesis

Although many studies have revealed the association between cyclooxygenase-2 (COX-2) and carcinogenesis, the association between COX-2 and Hodgkin's lymphoma (HL) remains unknown. We examined the immunohistochemical expression of COX-2, p53, bcl-2, and Ki-67 in 33 patients with HL, and counted microvessels stained with CD34. Hodgkin and Reed - Sternberg (HRS) cells with COX-2 expression were scored as 0 = no staining; 1 = <25% of cells staining; 2 = 25-49%; 3 = 50-75%; and 4 = > or =75%. COX-2 expression was observed in 15 cases of classical HL. Nevertheless, neither accumulation of p53 nor bcl-2 expression was associated with COX-2 expression. The percentage of Ki-67 positive-HRS cells and microvessel density in COX-2 score groups 2-4 were significantly higher than those in score group 0, respectively. We show that COX-2 expression is associated with cell proliferation and angiogenesis in HL. These findings suggest that COX-2 may be a target for therapy in HL.

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.

The Hodgkin and Reed/Sternberg cell

Hodgkin and Reed/Sternberg (HRS) cells are the hallmark cells of Hodgkin's lymphoma (HL). They are large, often multinucleated with a peculiar morphology and an unusual immunophenotype, that does not resemble any normal cell in the body. Despite their rarity in HL tissues, HRS cells are the clonal tumour cells of HL. HRS cells in nearly all cases of HL derive from B cells, and only rarely from T cells. Notably, the pattern of somatic mutations in their rearranged immunoglobulin V genes suggests that they are derived from pre-apoptotic germinal center B cells. The pathogenesis of HL is still largely unresolved, but it is now clear that aberrant activation of several signalling pathways (such as the NFkappaB pathway) is of key importance for HRS cell survival. HRS or HRS-like cells are also found in several other diseases, e.g. as rare intermingled cells in some non-Hodgkin lymphomas and in infectious mononucleosis.

Aberrant expression of cell cycle regulators in Hodgkin and Reed-Sternberg cells of classical Hodgkin's lymphoma

The characteristic Hodgkin and Reed-Sternberg cells of classical Hodgkin's lymphoma, although highly positive for proliferation markers, do not accumulate to excessive cell numbers. These cells are characterized by abortive mitotic cycles, leading to multinucleation or cell death in mitosis. We have previously described high expression of G1-phase cyclins in classical Hodgkin's lymphoma, which could explain the high percentage of cells staining for proliferation markers. To further our understanding of proliferation control in classical Hodgkin's lymphoma, we extended our immunohistochemical analysis to the main S-phase cyclin, cyclin A, and its regulators p21CIP1 and p27KIP1. Expression of proliferating cell nuclear antigen (PCNA) was used as an additional marker for cells being in either S- or G2-phase. In 47% (112/239) of classical Hodgkin's lymphoma cases p21CIP1 was detected within a mean frequency of 15% positive Hodgkin's and Reed-Sternberg cells per case. Similarly, 47% (116/249) of the cases stained positively for p27KIP1 with a mean frequency of expression in Hodgkin's and Reed-Sternberg cells of 12%. In contrast, 90% of the cells in all 246 evaluable classical Hodgkin's lymphoma cases were positive for PCNA. In addition, 98% of Hodgkin's and Reed-Sternberg cells in 99% (250/253) of the cases stained strongly positive for cyclin A. These findings further corroborate the hypothesis that Hodgkin and Reed-Sternberg cells exhibit a disturbed cell cycle with an abnormally short or even absent G1-phase. In contrast to other tumors, expression of PCNA or cyclin A had no prognostic value for patient survival.

Proliferation profile of classical Hodgkin's lymphomas. Increased expression of the protein cyclin D2 in Hodgkin's and Reed-Sternberg cells

There is accumulating evidence that Hodgkin's and Reed-Sternberg cells of classical Hodgkin's lymphomas (cHL) display multiple and concurrent alterations in different pathways and checkpoints of the cell cycle. However, the expression of cyclin D2 and its relation to other major cell cycle proteins has not been analyzed in cHL. The aim of the present study was to assess expression of cyclin D2, Ki67, cyclin A, cyclin B1, cyclin D1, cyclin D3, cyclin E, p53, Rb, p16 and p27 proteins in order to gain further insight into the proliferation profile of cHL. Overexpression of cyclin D2 in Hodgkin's and Reed-Sternberg cells was detected in 64/89 (72%) cases of cHL. This finding, in view of recent in vitro data showing that constitutive activation of nuclear factor (NF)-kB could upregulate cyclin D2 expression in part via signal transducer and activator of transcription (STAT)-5a, suggests that induction of cyclin D2 expression may support the proliferation of Hodgkin's and Reed-Sternberg cells. In addition, the present study showed that (1) increased p27 expression status was significantly correlated with higher levels of cyclin A expression (P=0.048) and (2) increased p53 expression status was significantly correlated with higher levels of cyclin A (P<0.001) and cyclin B1 (P=0.040) expression. The association between increased p27 and p53 expression status and higher expression levels of G2/M cyclins suggests that the impairment of the growth inhibitory activity of the p27 and p53 tumor suppressor pathways may promote the proliferation of Hodgkin's and Reed-Sternberg cells.

High-throughput tissue microarray analysis of G1-cyclin alterations in classical Hodgkin's lymphoma indicates overexpression of cyclin E1

Deregulation of G1-cyclins (CCN) plays a key role in the pathogenesis of many human malignancies, including non-Hodgkin's lymphomas (NHLs). In contrast to NHL, little is known about phenotypic and genotypic changes in the regulation of the cell cycle in classical Hodgkin's lymphoma (cHL). To facilitate analysis of aberrant gene expression in cHL, a lymphoma tissue microarray (TMA) containing 752 cores of 330 different cHL samples was constructed. Direct comparison of Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) expression in Hodgkin's and Reed-Sternberg (HRS) cells on conventional full sections with the corresponding duplicate/triplicate tumour cores on the TMA showed a concordance of 100%, indicating that cHL-TMA is a reliable and representative method for evaluating gene expression profiles in situ. Using TMA technology, protein expression and gene amplification of different G1-CCNs in cHL were analysed. Among the G1-CCNs analysed, cyclin E (CCNE) was expressed in 212/253 cases (84%). In most of the individual tumours, over 75% of the HRS cells stained positive for CCNE, suggesting that CCNE is overexpressed in cHL. This overexpression was not due to CCNE gene amplification, as judged by fluorescence in situ hybridization, and did not correlate with EBV infection, as assessed by the expression of LMP-1. Thus, the overexpression of CCNE could be caused by profound changes in HRS cell-cycle regulation that could contribute to the malignant phenotype.

Cell kinetics and cell cycle regulation in lymphomas

The proliferative indices of non-Hodgkin's lymphomas are useful prognostic indicators and provide information independent of other histological and clinical variables. However, proliferative indices alone do not suffice to characterise cell growth. A high cell production rate may be compensated, almost or fully, by a high cell deletion rate. A re-evaluation of parameters of cell kinetics in view of our increasing knowledge of the molecular pathways of cell cycle control may provide more prognostic information for the management of patients with malignant lymphomas.

Hodgkin's lymphoma: the pathologist's viewpoint

Despite its well known histological and clinical features, Hodgkin's lymphoma (HL) has recently been the object of intense research activity, leading to a better understanding of its phenotype, molecular characteristics, histogenesis, and possible mechanisms of lymphomagenesis. There is complete consensus on the B cell derivation of the tumour in most cases, and on the relevance of Epstein-Barr virus infection and defective cytokinesis in at least a proportion of patients. The REAL/WHO classification recognises a basic distinction between lymphocyte predominance HL (LP-HL) and classic HL (CHL), reflecting the differences in clinical presentation and behaviour, morphology, phenotype, and molecular features. CHL has been classified into four subtypes: lymphocyte rich, nodular sclerosing, with mixed cellularity, and lymphocyte depleted. The borders between CHL and anaplastic large cell lymphoma have become sharper, whereas those between LP-HL and T cell rich B cell lymphoma remain ill defined. Treatments adjusted to the pathobiological characteristics of the tumour in at risk patients have been proposed and are on the way to being applied.

Expression of the ALK protein by anaplastic large-cell lymphomas correlates with high proliferative activity

A variable fraction of anaplastic large-cell lymphomas (ALCLs) exhibits a t(2;5)(p23;q35) translocation that results in expression of the chimeric hyperphosphorylated protein NPM-ALK (p80). Tumor cells expressing NPM-ALK exhibit markedly enhanced proliferative activity, but comparative cellular kinetic studies on ALK(+) (ALK lymphomas) and ALK(-) lymphomas are lacking. The present study showed that ALK(+) lymphomas, detected with the monoclonal antibody ALKc (n = 17), had significantly higher average values for the proliferation-associated parameters mitotic index, ana/telophase index, growth index (x x mitotic index - apoptotic index, assuming x = 3), percentages of Ki-67(+) cells and fraction of cells expressing cyclin A or B or the cell cycle-regulatory protein p34(cdc2) than did ALK(-) ALCLs (n = 15). Whether this intense proliferative activity contributes to the good response to chemotherapy and favorable outcome of ALK(+) ALCLs remains to be assessed in a larger series of patients. Our findings support the notion that ALK(+) and ALK(-) ALCLs are 2 distinct disease entities.

Expression of p34(cdc2) and cyclins A and B compared to other proliferative features of non-Hodgkin's lymphomas: a multivariate cluster analysis

In view of recent knowledge on proteins regulating the cell cycle, we re-evaluated proliferative features of 98 diffusely growing non-Hodgkin's lymphomas. The combined use of 5 proliferation-associated variables (mitotic indices and percentages of Ki-67(+), p34(cdc2+), cyclin A(+) and cyclin B(+) cells) and their entry into a multivariate cluster analysis separated, without overlaps, the entire cohort into 3 groups (clusters) with (1) low, (2) intermediate and (3) high proliferative activity. Conversely, bivariate plots exposed considerable cluster overlaps. Multivariate stepwise discriminant analysis of all cases revealed a decreasing order of discriminant power for % Ki-67(+) cells > % p34(cdc2+) cells > mitotic index > % cyclin A(+) cells > % cyclin B(+) cells. The combined use of 2 variables only, mitotic index and % p34(cdc2+) cells, allowed a clear-cut separation of clusters 2 and 3. In bivariate plots, correlations were best between % Ki-67(+) cells and % cyclin A(+) cells and between mitotic indices and % cyclin B(+) cells. Except for chronic lymphocytic leukemias, immunocytomas and marginal zone lymphomas (all in cluster 1), individual lymphoma entities were distributed among at least 2 clusters. There was, however, a marked preponderance of mantle cell lymphomas and diffuse follicular center lymphomas in cluster 1 and of diffuse large B-cell lymphomas and peripheral T-cell lymphomas in cluster 2. Anaplastic large-cell lymphomas predominated in cluster 3 and responded best to therapy.

Apoptotic index as a prognostic factor in Hodgkin's disease

Hodgkin's disease (HD) is an unusual malignant neoplasm, mainly because of the rarity of tumor cells in the diseased tissues, but also due to a relatively favorable response to treatment. In a previous study, we have shown a variable degree of apoptosis in lymph nodes from HD patients. We now looked for clinicopathological correlations of apoptosis with special emphasis on the prognosis in this disease. A retrospective study of 92 patients was carried out, using in situ end labelling of DNA fragments and an apoptosis detection kit. An apoptotic index (Al) was calculated in each case, as the percentage of apoptotic Hodgkin-Reed-Sternberg cells out of the total number of tumor cells in 10 selected high power fields. An association between a high Al and advanced stages was noted. A Kaplan-Meier analysis showed a negative correlation between Al and survival (p=0.05). In a multivariable analysis adjusting for Ann Arbor stage, a high Al carried a 3.27 fold risk of dying of HD (OR=3.27; Cl=0.89-11.94). However, in our limited cohort of HD patients, Al was not an independent prognostic factor. The results of this study confirm the important role played by apoptosis in HD and suggest that the apoptotic index is probably a negative prognostic marker in this disease. Its assessment in patients with HD may provide a new, important clinical tool.

Cellular kinetic differences between Hodgkin's and anaplastic large cell lymphomas: relation to the expression of p34cdc2 and cyclin B-1

Our study was designed to compare cellular kinetic parameters of classical Hodgkin's disease (HD) with those of anaplastic large cell lymphomas (ALCL-C, common type; and ALCL-HL, Hodgkin's like), with a particular focus on the G2/M transition. These disorders share some phenotypic properties, e.g., CD30 positivity of putative neoplastic cells. The percentages of cells expressing p34cdc2 (p34) and cyclin B-1 (cyclin-B), which form a complex (maturation/mitosis promoting factor, MPF) regulating the G2-M phases of the cell cycle, were also registered. Highly significant differences between HD and ALCL-C were recognized: a) in HD, evidence for abortive mitosis (i.e., difficulty to proceed beyond the metaphase stage) and consequent multinucleation and/or deletion of CD30+ cells was prominent, in contrast to ALCL-C. This was associated with a markedly lower fraction of large atypical cells (LAC) expressing cyclin-B in the cytoplasm and the nucleus (C + N) in HD than in ALCL-C; b) the extent of multinucleation of CD30+ cells in HD, but not in ALCL-C, was correlated with the %p34+ LAC; c) the proportions of LAC expressing p34 and/or cyclin-B (C) were positively related to the percentages of cyclin-B (C + N)+ LAC in ALCL-C but not in HD; d) in HD, in contrast to ALCL-C, the size of the fraction of cyclin-B (C + N)+ LAC did not correlate with the ana/telophase indices (ATI, reflecting successful completion of mitosis) and the magnitude of cell loss; e) in ALCL-C, the percentages of p34+ LAC were positively correlated with ATI or the degree of CD30+ cell deletion, but inversely in HD. With regard to all parameters mentioned above, ALCL-HL tended to take an intermediate position between HD and ALCL-C, but sided more with the latter. In conclusion, our present results suggest a derangement of MPF kinetics and functions that is more profound in HD than in ALCL-C.

Cell kinetics, morphology, and molecular IgVH gene rearrangements in Hodgkin's disease

The present study dealt with the question of whether any cellular kinetic patterns correlate with clonal rearrangement of the IgVH gene as revealed by polymerase chain reaction on DNA extracted from lymph nodes with classical Hodgkin's disease (HD) and/or from single CD30+ cells (Hodgkin [H] and Reed-Sternberg [RS] cells). In 15/4 cases with H-RS cells of B or Null phenotype, signs of such monoclonality could be detected (group I) but not in the others (group II). CD30+/H-RS cells in group I differed slightly but significantly from those in group II in that they a) exhibited a larger fraction of cells attaining the anaphase/telophase stage of mitosis, and b) produced relatively more mononucleated cells (H) at the expense of multinucleated (RS) cells. In addition, reactive lymphoid cell (CD30-) infiltrates were considerably less dense in group I that in group II. These findings suggest that the cytokinesis of H-RS cells in group I was moderately more efficient than in group II. However, signs of monoclonality were not associated with the normalization of the mitotic process, which also proved to be disturbed in group I.

Nucleoli and AgNORs in Hodgkin's disease

AIM

To evaluate the morphofunctional characteristics of lymph node cells from patients with Hodgkin's disease by measuring silver stained nucleolar organiser regions (AgNORs).

METHODS

Nucleoli in Hodgkin's and Reed-Sternberg (HRS) cells, lymphocytes and prolymphocytes were investigated in cytological smears and histological sections of lymph nodes from 32 patients with Hodgkin's disease, and from 34 patients with reactive lymphadenopathy. According to the Rye histological classification of Hodgkin's disease, three cases were the lymphocyte predominant (LP) type, 14 the nodular sclerosing (NS) type, and 15 the mixed cellularity (MC) type. The investigation was done before treatment, by means of a one step silver staining method. In each case, 50 to 100 HRS cells, lymphocytes, and prolymphocytes were evaluated to determine the mean numbers of nucleoli and AgNORs per nucleus. The nonparametric Wilcoxon Mann-Whitney test was used to compare the groups.

RESULTS

The mean numbers of nucleoli and AgNORs were higher in lymphocytes and prolymphocytes compared with those from reactive lymph nodes used as controls. Numbers of nucleoli and AgNORs were higher (not significant) in the NS type of Hodgkin's disease than in the MC type. There was a significant increase in numbers of nucleoli in HRS cells, and their AgNOR counts were increased. The greatest number of nucleoli in HRS cells was found in the NS type. Furthermore, the nucleolar activity of HRS cells was greater in the NS type compared with the MC type (50.2 (SEM 3.9) v 37.7 (2.9) AgNORs per nucleus (p = 0.025)). Comparative analysis of cytological and histological samples showed that the AgNOR score was significantly higher in touch imprints than in tissue sections with tumours of the same histological type.

CONCLUSIONS

Assessment of cell activity in Hodgkin's disease patients by silver staining is more convenient and informative in lymph node imprints than in histological sections. The highest expression of interphase ribosomal RNA cistrons found in NS HRS cells is probably explained by their high proliferative activity and elevated production of transforming growth factor 1 which is known to be the most potent cytokine present in the NS subtype of Hodgkin's disease.