Chromosome abnormalities in peripheral blood lymphocytes from untreated Hodgkin's patients. A possible evidence for chromosome instability

A 2020 Vision Into Hodgkin Lymphoma Biology

Hodgkin lymphomas (HLs) are lymphoid neoplasms uniquely characterized by a paucity of neoplastic cells embedded in a supportive heterogenous cellular microenvironment. Although first described in the 19th century, systematic biological understanding of HLs has been hindered due to the challenges presented in studying the complex tumor microenvironment and scarce tumorigenic cells. Recent advances in single-cell isolation and characterization, sensitive mutational analytic tools, and multiplex immunohistochemical strategies have allowed further advances in understanding the development and progression of HL. Here we provide a current update on the chromosomal and mutational abnormalities seen in HL, the impact of Epstein-Barr virus infection on driving a subset of HLs, and the possibility of disease monitoring via high-sensitivity detection of genetic aberrations. We also discuss recent developments in understanding the intricate microenvironment through intercellular cross-talk, and describe novel potential biomarkers to aid in distinction of HL from other overlapping entities.

Chromosomal Instability in Hodgkin Lymphoma: An In-Depth Review and Perspectives

The study of Hodgkin lymphoma (HL), with its unique microenvironment and long-term follow-up, has provided exceptional insights into several areas of tumor biology. Findings in HL have not only improved our understanding of human carcinogenesis, but have also pioneered its translation into the clinics. HL is a successful paradigm of modern treatment strategies. Nonetheless, approximately 15–20% of patients with advanced stage HL still die following relapse or progressive disease and a similar proportion of patients are over-treated, leading to treatment-related late sequelae, including solid tumors and organ dysfunction. The malignant cells in HL are characterized by a highly altered genomic landscape with a wide spectrum of genomic alterations, including somatic mutations, copy number alterations, complex chromosomal rearrangements, and aneuploidy. Here, we review the chromosomal instability mechanisms in HL, starting with the cellular origin of neoplastic cells and the mechanisms supporting HL pathogenesis, focusing particularly on the role of the microenvironment, including the influence of viruses and macrophages on the induction of chromosomal instability in HL. We discuss the emerging possibilities to exploit these aberrations as prognostic biomarkers and guides for personalized patient management.

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.

Mitotic errors, aneuploidy and micronuclei in Hodgkin lymphoma pathogenesis

The Reed-Sternberg (RS) cell is the driving force behind Hodgkin lymphoma (HL), a unique malignancy in which the rare RS cell creates an inflammatory microenvironment that recruits a reactive tumor infiltrate. Well-known oncogenic factors such as nuclear factor kappa B (NFκB) signaling and Epstein-Barr virus infection are linked to HL pathogenesis but do not adequately explain the RS cell’s key pathologic features of multi-nucleation, abnormalities of centrosome function and number and aneuploidy. Chromosomal instability is also considered a key pathway in the origin of the RS cell, though the molecular mechanisms have largely been a “black box.” We demonstrated that the midbody kelch domain protein KLHDC8B protects against mitotic errors, centrosomal amplification and chromosomal instability. Here we discuss how the new findings linking KLHDC8B to mitotic integrity and faithful chromosomal segregation are providing mechanistic explanations for the origin of the RS cell and the molecular pathogenesis of chromosomal instability in HL.

The kelch protein KLHDC8B guards against mitotic errors, centrosomal amplification, and chromosomal instability

The malignant cell in classical Hodgkin lymphoma (HL) is the binucleated giant Reed-Sternberg cell. Chromosomal instability and mitotic errors may contribute to HL pathogenesis; one potential mitotic regulator is the kelch protein KLHDC8B, which localizes to the midbody, is expressed during mitosis, and is mutated in a subset of familial and sporadic HL. We report that disrupting KLHDC8B function in HeLa cells, B lymphoblasts, and fibroblasts leads to significant increases in multinucleation, multipolar mitoses, failed abscission, asymmetric segregation of daughter nuclei, formation of anucleated daughter cells, centrosomal amplification, and aneuploidy. We recapitulated the major pathologic features of the Reed-Sternberg cell and concluded that KLHDC8B is essential for mitotic integrity and maintenance of chromosomal stability. The significant impact of KLHDC8B implicates the central roles of mitotic regulation and chromosomal segregation in the pathogenesis of HL and provides a novel molecular mechanism for chromosomal instability in HL.

Persistent genomic instability in peripheral blood lymphocytes from Hodgkin lymphoma survivors

Advances in cancer treatment have led to an increase in patient survival. However, exposure to genotoxic chemotherapeutic agents and ionizing radiation may induce persistent genetic damage in cancer survivors. In this study, we detected genomic instability in chromosomes of peripheral blood lymphocytes from Hodgkin lymphoma patients, 2-17 years after MOPP (nitrogen mustard, Oncovin, procarbazine, and prednisone) chemotherapy with or without radiotherapy. Samples were obtained from 11 healthy individuals, 5 pretreatment patients, and 20 posttreatment patients. Cytogenetic analysis with GTG banding was performed on 1,000 lymphocyte metaphases per donor to identify genomic instability, including numerical and structural chromosomal aberrations, at a resolution of 10 Mb across the entire genome. Our results showed that anticancer treatment did not induce significant differences in the frequency of aneuploidy among the three study groups. However, 1 of the 11 healthy individuals, and 13 of the 20 posttreatment patients had a high frequency of chromosomal breaks and gross chromosomal rearrangements. The types of aberrations observed were random and complex, consistent with persistent genomic instability that was induced by cancer treatment. Clonal expansion of cells with chromosomal lesions was observed in one posttreatment patient only. These findings show that anticancer treatments induce persistent genomic instability, but not aneuploidy. Chemotherapy may affect genes with a role in DNA damage surveillance or repair, which in turn allows the accumulation of nontargeted structural chromosomal damage in future generations of cells. This genomic instability may facilitate the development of second malignancies in Hodgkin lymphoma survivors.

Mutations in a gene encoding a midbody protein in binucleated Reed-Sternberg cells of Hodgkin lymphoma

Classical Hodgkin lymphoma (cHL) is a cancer in which malignant "Reed-Sternberg" cells comprise just a fraction of the bulk of the tumor and are characteristically binucleated. We recently identified a novel gene, KLHDC8B, which appears responsible for some familial cases of cHL. KLHDC8B encodes a midbody kelch protein expressed during cytokinesis. Deficiency of KLHDC8B leads to binucleated cells, implicating its involvement in Reed-Sternberg cell formation. Interestingly, other cancer genes, such as BRCA1 and BRCA2, also encode proteins locating to the midbody during cytokinesis, even though their participation in other pathways has received greater attention. Midbody components may be an overlooked source of tumor suppressor genes.

Spontaneous and radiation-induced chromosomal instability and persistence of chromosome aberrations after radiotherapy in lymphocytes from prostate cancer patients

The aim of the study was to compare the spontaneous and ex vivo radiation-induced chromosomal damage in lymphocytes of untreated prostate cancer patients and age-matched healthy donors, and to evaluate the chromosomal damage, induced by radiotherapy, and its persistence. Blood samples from 102 prostate cancer patients were obtained before radiotherapy to investigate the excess acentric fragments and dicentric chromosomes. In addition, in a subgroup of ten patients, simple exchanges in chromosomes 2 and 4 were evaluated by fluorescent in situ hybridization (FISH), before the onset of therapy, in the middle and at the end of therapy, and 1 year later. Data were compared to blood samples from ten age-matched healthy donors. We found that spontaneous yields of acentric chromosome fragments and simple exchanges were significantly increased in lymphocytes of patients before onset of therapy, indicating chromosomal instability in these patients. Ex vivo radiation-induced aberrations were not significantly increased, indicating proficient repair of radiation-induced DNA double-strand breaks in lymphocytes of these patients. As expected, the yields of dicentric and acentric chromosomes, and the partial yields of simple exchanges, were increased after the onset of therapy. Surprisingly, yields after 1 year were comparable to those directly after radiotherapy, indicating persistence of chromosomal instability over this time. Our results indicate that prostate cancer patients are characterized by increased spontaneous chromosomal instability. This instability seems to result from defects other than a deficient repair of radiation-induced DNA double-strand breaks. Radiotherapy-induced chromosomal damage persists 1 year after treatment.

The biology of Hodgkin's lymphoma

Hodgkin's lymphoma was first described in 1832. The aetiology of this lymphoma, however, remained enigmatic for a long time. Only within the past 10 years has the B-cell nature of the pathognomonic Hodgkin and Reed-Sternberg (HRS) cells been revealed, along with several recurrent genetic lesions. The pathogenetic role for Epstein-Barr virus infection has also been substantiated. HRS cells in classical Hodgkin's lymphoma have several characteristics that are unusual for lymphoid tumour cells, and the Hodgkin's lymphoma microenvironment is dominated by an extensive mixed, potentially inflammatory cellular infiltrate. Understanding the contribution of all of these changes to the pathogenesis of this disease is essential for the development of novel therapies.

Human sensitivity to PhIP: a novel marker for prostate cancer risk

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) has been implicated in the development of colon, prostate and mammary gland tumors in rats. In this study, we developed a modified in vitro mutagen sensitivity assay, with activated PhIP (N-OH-PhIP) as the challenge mutagen and chromosome aberrations as the endpoint, and applied it in a pilot prostate cancer case-control study of 81 cases and 84 age and ethnicity-matched controls. Our results showed significantly higher baseline breaks among the cases, mean+/-S.E.=1.86+/-0.23 versus 0.96+/-0.14 in controls; P=0.006. Individuals with high baseline breaks (dichotomized at the control median) had a 36% increased risk for PC (OR=1.36; 95% CI=1.08-1.72). In stratified analysis, high baseline breaks was associated in younger participants (< or = 60 years) with an OR of 1.71 (1.14-2.57) and in those with a positive family history of PC, an OR of 1.43 (0.97-2.11). PhIP treatment induced significantly higher breaks in cases, mean+/-S.E.=5.07+/-0.39 versus 3.83+/-0.24 in controls; P=0.05. Higher PhIP-induced breaks was associated with an overall 17% increased risk for PC (OR=1.17; 95% CI=1.03-1.33), a significantly increased risks (OR=1.19; 95% CI=1.00-1.41) among younger participants, non-smokers (OR=1.39, 1.03-1.88) and 1.20 (1.00-1.45) among those with no family history of PC. Results from this pilot study demonstrate differential sensitivity to PhIP among subgroups and therefore, this assay have potential as a susceptibility marker for prostate cancer risk.

Chromosomal aberrations in lymphocytes of healthy subjects and risk of cancer

There is evidence that increased frequency of chromosomal aberration (CA) in peripheral blood lymphocytes is a predictor of cancer, but further data are needed to better characterize CA as marker of cancer risk. From the archives of 15 laboratories we gathered cytogenetic records of 11,834 subjects who were free of cancer at the moment of blood drawing and who underwent cytogenetic examination for preventive purposes in the Czech Republic during 1975-2000. We linked these records to the national cancer registry, revealing a total of 485 cancer cases. Subjects were classified according to the percentiles of CA distribution within each laboratory as low (0-33rd percentile), medium (34-66th percentile), and high (66-100th percentile). Subjects were further classified by occupational exposure and by subclass of CA. We found a significant association between the overall cancer incidence and the presence of chromosome-type aberrations [relative risk (RR) for high vs. low CA level = 1.24; 95% confidence interval (CI), 1.03-1.50] but not chromatid-type aberrations. Stomach cancer showed a strong association with frequency of total CA (RR = 7.79; 95% CI, 1.01-60.0). The predictivity of CA observed in subjects exposed to various classes of carcinogens did not significantly differ from the group of nonexposed subjects. This study contributes to validation of CA as a predictive marker of cancer risk, in particular, of stomach cancer; the association between CA frequency and cancer risk might be limited to chromosome-type aberrations.

Chromosomal Instability in Peripheral Blood Lymphocytes and Risk of Prostate Cancer

Prostate cancer is an extremely complex disease, and it is likely that chromosomal instability is involved in the genetic mechanism of tumorigenesis. Several chromosomes have been labeled as "players" in the development of prostate cancer, among them chromosome 1 and X chromosome have been reported to harbor prostate cancer susceptibility loci. However, there is little information regarding the background levels of chromosome instability in these patients. In this pilot study, we examined spontaneous chromosome instability in short-term lymphocyte cultures from 126 study subjects, 61 prostate cancer patients, and 65 healthy controls. We evaluated chromosomal instability using a fluorescence in situ hybridization assay using two probes targeting specific regions on X chromosome and chromosome 1. Our results showed a significantly higher mean level of spontaneous breaks involving the X chromosome in patients compared with controls (mean +/- SE, 2.41 +/- 0.26 and 0.62 +/- 0.08, respectively; P < 0.001). Similarly, chromosome 1 spontaneous breaks were significantly higher among cases compared with controls (mean +/- SE, 1.95 +/- 0.24 and 1.09 +/- 0.16, respectively; P < 0.001). Using the median number of breaks in the controls as the cutoff value, we observed an odds ratio (95% confidence interval) of 15.53 (5.74 - 42.03; P < 0.001) for spontaneous X chromosome breaks and 3.71 (1.60 - 8.63; P < 0.001) for chromosome 1 breaks and risk of development of prostate cancer. In conclusion, our preliminary results show that spontaneous chromosome instability could be a risk factor for prostate cancer.

Baseline and treatment-induced chromosomal abnormalities in peripheral blood lymphocytes of Hodgkin's lymphoma patients

PURPOSE

To study chromosomal abnormalities in 49 patients with Hodgkin's lymphoma (HL), before and after treatment and at several times during a 2-year period.

METHODS AND MATERIALS

Simple chromosomal aberrations (CAs) and complex chromosomal rearrangements (CCRs) were counted in peripheral lymphocytes by painting of chromosomes 1, 3, and 4 (fluorescence in situ hybridization). A control population was composed of 20 healthy donors and 69 untreated cancer patients who had undergone various radiologic scans.

RESULTS

A greater frequency (p < 10(-4)) of spontaneous cytogenetic abnormalities was observed in untreated HL patients compared with the control populations. CCRs were observed exclusively in the HL population (p < 10(-4)). Chemotherapy was associated with a significant increase in the frequency of CAs (p < 10(-4)), according to the chemotherapy regimen (p = 0.002). Immediately after radiotherapy, a significant increase (p < 10(-4)) was observed in CAs according to the size of the irradiation field. Conversely, the significant increases in the frequency of CCRs observed after treatment did not correlate with the chemotherapy regimens, radiotherapy dose, or size of the irradiation field. The evolution of CAs vs. CCRs over time was also dissociated: during the follow-up of these patients, a significant decrease was observed in the frequency of CAs at 6 months and 1 and 2 years. In contrast, after an initial decrease for up to 6 months after treatment, the frequency of CCRs remained constant for up to 2 years.

CONCLUSION

Increased cytogenetic abnormalities were observed in untreated HL patients compared with the control populations. The greater frequency of cytogenetic abnormalities persisted in some patients. The presence of CCRs supports the concept of a unique genetic environment in HL patients that persists in response to potentially noxious treatments.

Molecular biology of Hodgkin's lymphoma

Hodgkin's lymphoma (HL) is characterized by typical mononucleated Hodgkin and multinucleated Reed-Sternberg cells, which occur at low frequency in a mixed cellular infiltrate in the tumor tissue. Because of the rarity of these cells and their unusual immunophenotype, which is strikingly different from those of all normal hematopoietic cell types, the origin of these cells and their clonality have long been unclear. Single-cell studies of rearranged immunoglobulin genes showed that Hodgkin and Reed-Sternberg (HRS) cells represent clonal tumor-cell populations derived from germinal center B cells. In classical HL, the detection of obviously crippling immunoglobulin gene mutations in a fraction of the cases suggests that HRS cells may derive from germinal center B cells that have lost the capacity to be positively selected by antigen and that normally would have undergone apoptosis. In rare cases, HRS cells represent transformed T lymphocytes. The transforming events involved in malignant transformation of HRS cells are still largely unknown. Constitutive activation of the transcription factor NFkappaB, which can, for example, be induced through Epstein-Barr virus transformation of HRS cells or destructive somatic mutations of the inhibitor of NFkappaB, is likely to be a key event in HL pathogenesis. Significant progress has been made in our understanding of the cellular interactions in HL tissues, which are mainly mediated by a large variety of cytokines and chemokines.

No evidence of increased chromosomal aberrations and micronuclei in lymphocytes from nonfamilial thyroid cancer patients prior to radiotherapy

The relationship between the presence of high frequencies of chromosomal aberrations in peripheral lymphocytes and predisposition to cancer has been suggested for some cancer diseases. In nonfamilial thyroid cancer, the few reports available are equivocal. The aim of this study was to assess the possible chromosomal instability in peripheral blood lymphocytes from 22 patients suffering from nonfamilial thyroid cancer. For this purpose, 2 classic cytogenetic assays, the chromosomal aberrations assay and cytokinesis-blocked micronucleus assay, were chosen. The frequency of chromosomal aberrations excluding gaps (%) was 1.68 +/- 1.39 (mean value +/- SD) for the patients group versus 2.20 +/- 1.87 for the control group. The frequency of binucleated lymphocytes with micronuclei ( per thousand) was 5.41 +/- 3.51 (mean value +/- SD) for the patients group versus 5.37 +/- 3.21 for the control group. The results obtained revealed no significant differences between both groups. The present study reinforces the idea that constitutional chromosomal instability in peripheral blood lymphocytes is not visible in nonfamilial thyroid carcinomas.

Molecular single-cell analysis of the clonal relationship of small Epstein-Barr virus–infected cells and Epstein-Barr virus–harboring Hodgkin and Reed/Sternberg cells in Hodgkin disease

Epstein-Barr virus (EBV) can be detected in the tumor cells of approximately 40% of cases of classical Hodgkin disease (cHD). Clonality studies suggest that infection of the neoplastic Hodgkin and Reed/Sternberg (HRS) cells occurs before tumor clone expansion. In EBV-positive cases, variable numbers of EBER-positive small B cells are sometimes also observed that immunohistologically differ from the neoplastic cells by lack of CD30 and latent membrane protein 1 expression. To analyze the clonal relationship between these EBV+ cells and the HRS cells, single EBV-infected CD30− B cells, as well as HRS cells from 3 cases of EBV-positive cHD were micromanipulated, their immunoglobulin gene rearrangements amplified and then compared with each other. In 2 cases, all small EBV-infected cells were clonally unrelated to the HRS cells. In a third case, 2 of 29 small CD30− cells were found to carry HRS cell-specific rearrangements. Thus, small CD30−EBV-infected B cells in cHD belong to the HRS tumor clone rarely, if at all. In all cases, small clones unrelated to the HRS cell clones were identified among the small EBV+ CD30− cells. The vast majority of small EBV+ CD30− B cells was found to carry somatically mutated V region genes, indicating that in lymph nodes of patients with HD, like in the peripheral blood of healthy individuals, EBV persists in memory B cells.

Molecular single-cell analysis of the clonal relationship of small Epstein-Barr virus–infected cells and Epstein-Barr virus–harboring Hodgkin and Reed/Sternberg cells in Hodgkin disease

Epstein-Barr virus (EBV) can be detected in the tumor cells of approximately 40% of cases of classical Hodgkin disease (cHD). Clonality studies suggest that infection of the neoplastic Hodgkin and Reed/Sternberg (HRS) cells occurs before tumor clone expansion. In EBV-positive cases, variable numbers of EBER-positive small B cells are sometimes also observed that immunohistologically differ from the neoplastic cells by lack of CD30 and latent membrane protein 1 expression. To analyze the clonal relationship between these EBV+ cells and the HRS cells, single EBV-infected CD30− B cells, as well as HRS cells from 3 cases of EBV-positive cHD were micromanipulated, their immunoglobulin gene rearrangements amplified and then compared with each other. In 2 cases, all small EBV-infected cells were clonally unrelated to the HRS cells. In a third case, 2 of 29 small CD30− cells were found to carry HRS cell-specific rearrangements. Thus, small CD30−EBV-infected B cells in cHD belong to the HRS tumor clone rarely, if at all. In all cases, small clones unrelated to the HRS cell clones were identified among the small EBV+ CD30− cells. The vast majority of small EBV+ CD30− B cells was found to carry somatically mutated V region genes, indicating that in lymph nodes of patients with HD, like in the peripheral blood of healthy individuals, EBV persists in memory B cells.

Clonal deleterious mutations in the IkappaBalpha gene in the malignant cells in Hodgkin's lymphoma

Members of the nuclear factor (NF)-kappaB family of transcription factors play a crucial role in cellular activation, immune responses, and oncogenesis. In most cells, they are kept inactive in the cytosol by complex formation with members of the inhibitor of NF-kappaB (IkappaB) family, whose degradation activates NF-kappaB in response to diverse stimuli. In Hodgkin's lymphoma (HL), high constitutive nuclear activity of NF-kappaB is characteristic of the malignant Hodgkin and Reed-Sternberg (H/RS) cells, which occur at low number in a background of nonneoplastic inflammatory cells. In single H/RS cells micromanipulated from histological sections of HL, we detect clonal deleterious somatic mutations in the IkappaBalpha gene in two of three Epstein-Barr virus (EBV)-negative cases but not in two EBV-positive cases (in which a viral oncogene may account for NF-kappaB activation). There was no evidence for IkappaBalpha mutations in two non-HL entities or in normal germinal center B cells. This study establishes deleterious IkappaBalpha mutations as the first recurrent genetic defect found in H/RS cells, indicating a role of IkappaBalpha defects in the pathogenesis of HL and implying that IkappaBalpha is a tumor suppressor gene.

Genetic analysis of sorted Hodgkin and Reed-Sternberg cells using comparative genomic hybridization

Hodgkin and Reed-Sternberg (H and RS) cells are generally considered to be the neoplastic cells of Hodgkin's disease (HD); however, such cells are found only in a minority of HD lesions. Very few data have so far been published on the cytogenetic abnormalities in HD. An analysis of unknown genetic aberrations has only recently become possible through the use of comparative genomic hybridization (CGH), which is based on the competitive binding of tumor and control DNA to metaphase chromosomes. In order to exclude the reaction of non-tumor cells, we used 100 sorted H-RS cells as the tumor DNA, then 100 sorted reactive T cells or B cells as the control DNA. We obtained the amplified DNA, using degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR). In addition, to confirm whether or not the lymphocytes in the background were reactive, we performed CGH with 100 sorted B cells and 100 sorted T cells. CGH was thus performed on 9 HDs, including 6 cases of mixed-cellularity (MC) sub-type and 3 cases of nodular-sclerosis (NS) sub-type. CGH of the B and T cells showed no genetic changes in any cases. In contrast, CGH of H-RS cells revealed both gains and losses of DNA in all 9 cases, and multiple changes were also observed. In situ hybridization showed an Epstein-Barr-virus infection in 5 cases of MC; however, no definite relationship was observed between the EBV infection and genetic changes. The most commonly observed genetic aberrations were a loss on 16q11/21 in 6 cases, a gain on 1p13 in 5 cases, and a gain on 7q35/36 in 5 cases. The large number of chromosomal alterations in HD suggests, therefore, that an increased degree of genetic instability play a role in the formation of H-RS cells.

Chromosomal abnormalities in Hodgkin's disease are not restricted to Hodgkin/Reed-Sternberg cells

Hodgkin and Reed-Sternberg cells are considered to represent the malignant fraction in Hodgkin's disease. Several studies have shown that the Hodgkin and Reed-Sternberg cells are chromosomally abnormal, but genetic data about the morphologically normal cell population in Hodgkin's disease are very limited. This latter cell population has therefore been examined for chromosomal aberrations, using the in situ hybridization (ISH) procedure, making use of DNA probes for chromosomes 1, 7, 8, 9, 11, 12, 15, 17, and 18. Nuclei were isolated from freshly frozen (10 cases) and paraffin-embedded (16 cases) biopsy samples and 1000 nuclei per case were evaluated. The cases of Hodgkin's disease were compared with reactive lymph nodes, which show aberrant chromosome copy numbers in less than 1 per cent of the cells. Using strict scoring criteria, nuclei in the tumour were found to show an abnormal genotype, in the range of 1-12 per cent, with trisomies occurring most frequently. No characteristic numerical chromosome abnormality was observed. ISH on 4 microns thick paraffin sections of six cases of Hodgkin's disease revealed numerical aberrations for chromosome 1 in cells which appeared to be morphologically normal. The genomically abnormal nuclei did not differ in morphology or size from the nuclei of morphologically normal cells, but differed considerably in size when compared with the nuclei of Hodgkin/Reed-Sternberg cells after the ISH procedure. Three of these six cases revealed a population of apparently normal cells with an aberrant copy number which differed notably from the fraction observed in reactive lymph nodes. It is concluded, therefore, that a subset of morphologically normal cells, next to the Hodgkin/Reed-Sternberg cells, are chromosomally aberrant and may participate in the malignant cell fraction of Hodgkin's disease.

The origin of Hodgkin and Reed/Sternberg cells in Hodgkin's disease

One of the characteristic features of Hodgkin's disease (HD) is the presence of a small population of often bizarre-looking large mono- or multinucleated Hodgkin and Reed-Sternberg (HRS) cells within the affected tissue. Recent cytogenetic investigations, studies of Epstein-Barr virus (EBV) genomes present in HRS cells, and analyses of Ig gene rearrangements amplified from single, micromanipulated HRS cells show that these cells largely represent clonal populations. The finding of Ig gene rearrangements in HRS cells in most cases of HD identifies B cells as the precursors of HRS cells in most if not all cases. Furthermore, the presence and pattern of somatic mutations within the rearranged Ig genes show that HRS cells in classical (i.e. nodular sclerosis, mixed cellularity, and lymphocyte depletion HD) as well as lymphocyte predominant (LP) HD originate from germinal center (GC) B cells. Ongoing somatic mutation and evidence for selection link HRS cells from LP HD to a mutating, antigen-selected GC B cell. In classical HD, the finding of "crippling" mutations and lack of stringent selection for antigen receptor expression suggests that in this case HRS cells are derived from a compartment of GC B cells that were destined to die but escaped apoptosis by some transforming event. One candidate for the latter is EBV infection.

Cytogenetics and molecular cytogenetics in Hodgkin's disease

For about 20 years we have known from cytogenetic studies that there is a clonal cell population in Hodgkin's disease. Most karyotypes are complexly aberrant and chromosome numbers typically lie in the hyperploid range. Some chromosome regions seem to be preferentially involved, but a chromosome aberration specific for Hodgkin's disease has not yet been determined. Although the existence of a clonal cell population is evident from these cytogenetic studies, there is still an ongoing debate, whether in all cases the pathognomonic Hodgkin and Reed-Sternberg cells belong to one single aberrant clone and thus represent a monoclonal proliferation. This article reviews the current knowledge on cytogenetics in Hodgkin's disease. Moreover, our recent data from simultaneous immunophenotyping and interphase cytogenetics (FICTION) are introduced into the passionate discussion on the monoclonality of the Hodgkin and Reed-Sternberg cells.

The role of Epstein-Barr virus in the pathogenesis of Hodgkin's disease

Hodgkin's disease represents a phenotypically and genotypically heterogeneous lymphoma of CD30-positive tumour cells. Infection of the putative tumour cell population with Epstein-Barr virus (EBV) represents the most common genetic abnormality detectable in HD, yet the role of EBV in the pathogenesis of HD is only poorly understood. In virus-associated HD cases, monoclonal EBV genomes are detectable in all Hodgkin and Reed-Sternberg (HRS) cells, indicating that EBV infection takes place before expansion of the HRS cell population and, by implication, supporting the concept of a monoclonal origin of HRS cells. EBV infection does not define a distinct subgroup of HD but is detectable in different histotypes and in HRS cells expressing lymphocyte differentiation antigens of different cell lineages. Through the EBV-encoded protein, LMP1, the virus may superimpose an activated phenotype on genotypically immature lymphocytes. EBV-induced modulation of the cytokine expression pattern of HRS cells may contribute to the local inhibition of EBV-specific immunity observed in EBV-positive cases.

Hodgkin's disease with monoclonal and polyclonal populations of Reed-Sternberg cells

BACKGROUND

There is strong evidence that Reed-Sternberg cells have a lymphoid phenotype, but clonally rearranged genes for B-cell and T-cell antigen receptors have not been demonstrable in tumor tissue from most patients with Hodgkin's disease. To elucidate this issue, we assayed single Reed-Sternberg cells from 12 patients with classic Hodgkin's disease of a B-cell immunophenotype to detect rearranged immunoglobulin variable-region heavy-chain (VH) genes.

METHODS

We isolated single Reed-Sternberg cells from frozen sections that had been immunostained for CD30. The rearranged VH genes of these cells were amplified by the polymerase chain reaction and analyzed by gel electrophoresis and nucleotide sequencing.

RESULTS

In all 12 patients, the Reed-Sternberg cells studied contained rearranged VH genes. Three patterns were observed: in three patients the rearrangements in each patient were identical, in six patients all the rearrangements were unrelated and unique, and in three patients both identical and unrelated rearrangements were detected. Apparently somatic mutations of VH genes were present in some Reed-Sternberg cells but absent in others.

CONCLUSIONS

Reed-Sternberg cells with B-cell phenotypes have rearranged VH genes; therefore, these cells arise from B cells. The pattern of VH gene mutations suggests that Reed-Sternberg cells can correspond to either immunologically naive or memory B cells. In half our patients the population of Reed-Sternberg cells was polyclonal; in the other half, monoclonal or mixed cell populations were found. Correlation with the clinical stage suggests that polyclonal Hodgkin's disease can present as a widespread lymphoma.

Peripheral blood chromosome aberrations in MDS

The frequency of non-clonal structural and numerical chromosome aberrations in peripheral blood lymphocytes of 51 patients with MDS and 37 age-matched hematologically normal subjects is assessed. The frequency of aneuploid cells (p less than 0.001) and of structural aberrations (p less than 0.005) was significantly higher in MDS patients than in normal subjects, but showed no relationship with FAB type or with the presence of clonal karyotype abnormalities in the bone marrow. Exchange configurations were only observed in MDS patients (27.5%). The data also suggest that there may be an association between high peripheral blood aberration levels and rapidly progressive disease. This may indicate increased mutagen sensitivity and have implications for treatment.

The frequency of translocations after treatment for Hodgkin's disease

We studied the frequency of translocations in peripheral blood lymphocytes of patients with Hodgkin's disease to determine the extent of chromosome changes induced by radiation or radiation and chemotherapy. Comparisons were made to patients with second cancers to determine if this population is more susceptible to the effects of treatment. Group one included six patients with newly diagnosed Hodgkin's disease who were treated with radiation only. Group two included Hodgkin's disease patients who were treated 12-24 years previously and have been continuously free of disease. Five of these patients were treated with radiation only and five patients received radiation and mechlorethaminehydrochloride, oncovin, procarbazine, prednisone (MOPP) chemotherapy for six cycles. Group three included three patients who developed a second cancer after successful treatment for Hodgkin's disease. Two of these patients had a sarcoma within the radiation field and one had breast cancer. Metaphase spreads were obtained from cultured lymphocytes and hybridized with a chromosome 4 specific probe. After fluorescein staining, approximately 1000 metaphases were scored per patient. In group one only one patient in six demonstrated translocations in chromosome 4 before treatment for a mean frequency of .0009. After treatment the frequency of translocations increased to a mean of .016 (p = .036) (range .006-.034). Group two patients treated with radiation only had a mean translocation frequency of .012 (range .004-.022) in comparison to the radiation/mechlorethaminehydrochloride, oncovin, procarbazine, prednisone chemotherapy treated patients who demonstrated a mean frequency of .016 (p = .425) (range .0009-.023). The third group of second cancer patients showed inconsistent translocation frequencies of .002, .020, and .035. Of these patients, the one who demonstrated the greatest frequency of translocations (.035) was treated with mechlorethaminehydrochloride, oncovin, procarbazine, prednisone/adriamycin, bleomycin, vinblastine, decadron) and radiation. Our data demonstrates a statistically significant increase in translocations detected after radiation. When compared to combined modality therapy a greater mean frequency of translocations is observed over radiation alone; however, this was not statistically significant. In the three patients who developed second cancers in our series we saw no consistent increase in translocation frequency compared to Hodgkin's disease patients who did not develop a second cancer.

Chromosomal instability in breast cancer patients

We have carried out cytogenetic studies, using the G-banding technique, in peripheral blood lymphocytes of 10 patients affected by breast carcinoma. The frequency of aberrant metaphases (7.36%) is significantly different from that of our laboratory controls (3.76% of aberrant metaphases) but not from that detected in patients suffering from bladder cancer (10.64%) and Hodgkin's disease (11.03%), two conditions that have previously been described as chromosomally unstable. Our results suggest that breast carcinoma patients show a degree of chromosomal instability that could be related to a predisposition to neoplastic disease.

Cytogenetic study of a nodular hyperplasia of the thyroid after irradiation for Hodgkin's disease

We describe cytogenetics of a case of nodular hyperplasia of the thyroid with papillary microcarcinoma following radiotherapy for Hodgkin's disease. The chromosomal pattern found was very heterogeneous with a clonal abnormality of chromosome 10, among others. Together with some recent data from the literature, this finding may point to an important role of chromosome 10 abnormalities in the pathogenesis of benign and malignant thyroid neoplasms.

Chromosome instability in bladder carcinoma patients

The relationship between the presence of a high frequency of chromosome aberrations and a predisposition to cancer has been well established in the so-called chromosome instability syndromes. Chromosome instability is also present in a variety of patients affected by cancer, and sometimes in their healthy relatives. We present a cytogenetic study carried out in lymphocytes from 13 untreated bladder carcinoma patients (only four of them had a history of occupational exposure to mutagens). Percentages of aberrant metaphases were significantly higher in cancer patients than in controls. Of the total number of chromosome aberrations in cancer patients, 67.16% corresponded to major structural chromosome abnormalities, while 25.37% were gaps or breaks. Numerical abnormalities represented 7.46% of the total. The bands more frequently involved in chromosome rearrangements were 5q31 and 1q32. Our results tentatively indicate that a significant proportion of patients with bladder carcinoma may have an underlying inherent chromosome instability. An age effect cannot be excluded, but we did not find significant differences between patients over 50 years of age and patients under 50 years of age.

Cytogenetic effects of radiotherapy: frequency and types of chromosome aberrations

The frequency and types of chromosome aberrations induced by ionizing radiation in cancer patients were evaluated in 24 cases studied just before and immediately after radiotherapy. The incidence of aberrant metaphases prior to treatment was 9.98% and increased significantly after treatment to 32.8%. The frequency of chromosome aberrations before radiotherapy was, with the exception of the cases of breast cancer and seminoma, significantly higher than that in our laboratory controls. A comparison of chromosome abnormalities observed before and after treatment indicated that dicentric translocations, rings, and reciprocal translocations increased by a factor of 23, 13, and 11, respectively, after radiotherapy. Ionizing radiation produces more asymmetrical than symmetrical chromosome aberrations and more two-break than one-break anomalies.