Low frequency of BCL-2/J(H) translocation in peripheral blood lymphocytes of healthy Japanese individuals

Precursory or early lesions of follicular lymphoma: clinical features, pathology, and genetics

Follicular lymphoma (FL) is an indolent B-cell lymphoma with a germinal center (GC) B cell phenotype that typically harbors t(14;18)(q32;q21). t(14;18) juxtaposes IGH on 14q32 and BCL2 on 18q21, resulting in overexpression of the anti-apoptotic BCL2 protein. However, t(14;18) is also found in the peripheral blood or lymphoid nodes (LNs) of otherwise healthy individuals. Moreover, overt FL has several additional gene alterations involved in epigenetic modification, JAK/STAT signaling, immune modulation, and NF-κB signaling, indicating multi-step lymphomagenesis in FL. There are two early or precursory lesions of FL: t(14;18)-positive cells in the peripheral blood of otherwise healthy individuals and in situ follicular B-cell neoplasm (ISFN). t(14;18)-positive cells are found in 10%-50% of healthy populations, and their incidence and frequency increase with age. The detection of t(14;18) in peripheral blood is a predictive factor for an increased risk of overt FL development. In contrast, ISFN is a histopathologically recognizable precursory lesion, in which t(14;18)-positive cells are confined to the GC of otherwise reactive LNs. ISFN is usually detected incidentally, with an incidence ranging from 2.0% to 3.2%. Occasional ISFN cases have concurrent or metachronous clonally related overt FL or aggressive B-cell lymphoma of a GC phenotype. t(14;18)-positive cells in peripheral blood and isolated ISFN, by themselves, are asymptomatic with limited clinical significance; however, investigations of t(14;18)-positive precursory or early lesions offer meaningful insights into the pathogenesis of FL. This review summarizes the epidemiology, clinical features, pathology, and genetics of precursory or early lesions of FL.

Incidence, Clinicopathologic Features, and Genetics of in situ Follicular Neoplasia: A Comprehensive Screening Study in a Japanese Cohort

AIMS

In situ follicular neoplasia (ISFN) is a histologically recognisable neoplastic proliferation of follicular lymphoma (FL)-like B cells confined to the germinal centres. While some ISFNs are associated with overt FL, others are incidentally identified as isolated or pure forms in individuals without evidence of overt FL. The prevalence of incidentally found isolated ISFN is approximately 3% in Europe; however, no screening study has been conducted in Asia. To investigate the incidence and clinicopathologic characteristics of ISFNs in the Japanese population, we conducted histopathological screening of the lymph nodes (LNs) resected for solid tumours or inflammatory conditions.

METHODS AND RESULTS

We screened for ISFN in 5,700 LNs from 340 individuals using immunohistochemistry for BCL2 and identified seven ISFNs, with an incidence of 2.1%. The median age of the individuals with ISFN was 67 years, none of whom developed overt FL, with a median follow-up of 59 months. Next-generation sequencing was performed in five ISFNs, and ten variants in seven FL-associated genes were identified. The identified variants included HIST1H1E (2/5), ARID1A (2/5), KMT2D (1/5), CARD11 (1/5), BCL7A (1/5), CREBBP (1/5), and TNFRSF14 (1/5).

CONCLUSIONS

The incidence of isolated ISFN in the Japanese population is not significantly different from that in Europe, presumably reflecting the recent increase in FL in Japan. These incidentally found ISFNs have a low potential to transform into overt FL. Although mutations of FL-associated genes are already present in ISFNs, further molecular studies are needed to identify driver genes leading to the transformation of ISFN to overt FL.

Chromosomal translocation t(11;14) and p53 deletion induced by the CRISPR/Cas9 system in normal B cell-derived iPS cells

Multiple myeloma (MM) cells are derived from mature B cells based on immunoglobulin heavy chain (IgH) gene analysis. The onset of MM is often caused by a reciprocal chromosomal translocation (cTr) between chr 14 with IgH and chr 11 with CCND1. We propose that mature B cells gain potential to transform by reprograming, and then chromosomal aberrations cause the development of abnormal B cells as a myeloma-initiating cell during B cell redifferentiation. To study myeloma-initiating cells, we have already established normal B cell-derived induced pluripotent stem cells (BiPSCs). Here we established two BiPSCs with reciprocal cTr t(11;14) using the CRISPR/Cas9 system; the cleavage site were located in the IgH Eμ region of either the VDJ rearranged allele or non-rearranged allele of IgH and the 5'-upsteam region of the CCND1 (two types of BiPSC13 with t(11;14) and MIB2-6 with t(11;14)). Furthermore, p53 was deleted using the CRISPR/Cas9 system in BiPSC13 with t(11;14). These BiPSCs differentiated into hematopoietic progenitor cells (HPCs). However, unlike cord blood, those HPCs did not differentiated into B lymphocytes by co-culture with BM stromal cell. Therefore, further ingenuity is required to differentiate those BiPSCs-derived HPCs into B lymphocytes.

Identification of primary copy number variations reveal enrichment of Calcium, and MAPK pathways sensitizing secondary sites for autism

Background

Autism is a neurodevelopmental condition with genetic heterogeneity. It is characterized by difficulties in reciprocal social interactions with strong repetitive behaviors and stereotyped interests. Copy number variations (CNVs) are genomic structural variations altering the genomic structure either by duplication or deletion. De novo or inherited CNVs are found in 5–10% of autistic subjects with a size range of few kilobases to several megabases. CNVs predispose humans to various diseases by altering gene regulation, generation of chimeric genes, and disruption of the coding region or through position effect. Although, CNVs are not the initiating event in pathogenesis; additional preceding mutations might be essential for disease manifestation. The present study is aimed to identify the primary CNVs responsible for autism susceptibility in healthy cohorts to sensitize secondary-hits. In the current investigation, primary-hit autism gene CNVs are characterized in 1715 healthy cohorts of varying ethnicities across 12 populations using Affymetrix high-resolution array study. Thirty-eight individuals from twelve families residing in Karnataka, India, with the age group of 13–73 years are included for the comparative CNV analysis. The findings are validated against global 179 autism whole-exome sequence datasets derived from Simons Simplex Collection. These datasets are deposited at the Simons Foundation Autism Research Initiative (SFARI) database.

Results

The study revealed that 34.8% of the subjects carried 2% primary-hit CNV burden with 73 singleton-autism genes in different clusters. Of these, three conserved CNV breakpoints were identified with ARHGAP11B, DUSP22, and CHRNA7 as the target genes across 12 populations. Enrichment analysis of the population-specific autism genes revealed two signaling pathways—calcium and mitogen-activated protein kinases (MAPK) in the CNV identified regions. These impaired pathways affected the downstream cascades of neuronal function and physiology, leading to autism behavior. The pathway analysis of enriched genes unravelled complex protein interaction networks, which sensitized secondary sites for autism. Further, the identification of miRNA targets associated with autism gene CNVs added severity to the condition.

Conclusion

These findings contribute to an atlas of primary-hit genes to detect autism susceptibility in healthy cohorts, indicating their impact on secondary sites for manifestation.

Clinicopathological features of in situ follicular neoplasm and relations with follicular lymphoma in Japan

This study aims to investigate the clinicopathological features of in situ follicular neoplasm (ISFN) in Japan. ISFN is a rare condition formerly considered as an early precursor of follicular lymphoma (FL). This is a first original report of ISFN from Asian country. We reviewed 19 biopsy samples of ISFN. ISFNs were categorized into two groups: (1) ISFN, consisting of ISFN with strong positivity for BCL-2 immunohistochemical staining (IHC), and obvious translocation of BCL-2; and (2) ISFN-like FL, featuring cases without obvious translocation but having morphological features and characteristic IHC findings of ISFN. As control, we adopted obvious FL. For some cases showing coexisting ISFN and FL lesions in the same lymph node, we could conduct further clonality analysis for each lesion. Nine of the 19 cases of ISFN coexisted with FL or had a history of overt B- or T-cell lymphoma including FL. Statistical comparison among ISFN-like FL and FL showed no significant differences in pathological features. Molecular analysis suggested that ISFN lesion and FL lesion in the same lymph node each have a different clonality. ISFN coexists or associates with other overt lymphomas frequently.

Transformed follicular lymphoma

Follicular Lymphoma (FL) is the second most common type of non-Hodgkin lymphoma and is considered to be the prototype of indolent lymphomas. Histologic transformation into an aggressive lymphoma, which is expected to occur at a rate of 2 to 3% each year, is associated with rapid progression, treatment resistance, and poor prognosis. Recent modifications to the physiopathologic mechanism of transformed follicular lymphoma (t-FL) have been proposed, including genetic and epigenetic mechanisms as well as a role for the microenvironment. Although t-FL is considered a devastating complication, as it is associated with treatment-refractory disease and a dismal outcome, recent data in the rituximab era have suggested that not only is the prognosis less severe than reported in the previous literature but the risk of transformation is also lower. Thus, this study aimed to review the most recent research on t-FL in an attempt to better understand the clinical meaning of transformation from FL to diffuse large B cell lymphoma (DLBCL) and the impact of current treatment strategies on the curability of this intriguing subentity of lymphoma.

Presence of t(14;18) translocation in healthy individuals varies according to ethnic background in the Brazilian population

Several groups have demonstrated that healthy individuals can present the t(14;18) translocation. In this report, the presence of the translocation was examined in healthy blood donors in Brazil, a country considered an ethnic melting pot. The translocation was detected by nested PCR in 227 peripheral blood samples from individuals with different ethnic backgrounds. The t(14;18) translocation was found in 45 of 85 White individuals (52.94%); in 57 of 72 Black individuals (79.17%); and in 68 of 70 individuals (97.14%) of Japanese-descent. In conclusion, the frequency of the t(14;18) translocation in the Brazilian population varies according to the ethnic background.

Identifying the risk of producing aneuploids using meiotic recombination genes as biomarkers: A copy number variation approach

Background & objectives:

Aneuploids are the most common chromosomal abnormality in liveborns and are usually the result of non-disjunction (NDJ) in meiosis. Copy number variations (CNVs) are large structural variations affecting the human genome. CNVs influence critical genes involved in causing NDJ by altering their copy number which affects the clinical outcome. In this study influence of CNVs on critical meiotic recombination was examined using new computational technologies to assess their role in causing aneuploidy.

Methods:

This investigation was based on the analysis of 12 random normal populations consisting of 1714 individuals for aneuploid causing genes under CNV effect. To examine the effect of CNVs on genes causing aneuploidy, meiotic recombination genes were analyzed using EnrichR, WebGestalt and Ingenuity Pathway Analysis (IPA).

Results:

Forty three NDJ genes were found under CNV burden; IPA (Ingenuity Pathway Analysis) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis of CNV in meiotic recombination genes revealed a significant role of breast cancer gene 1, amyloid protein precursor, mitogen-activated protein kinase and nerve growth factor as key molecular players involved in causing aneuploidy. Interaction between these genes with other CNV-overlapping genes involved in cell cycle, recombination and meiosis might lead to increased incidences of aneuploidy.

Interpretation & conclusions:

The findings of this study implied that the effect of CNVs on normal genome contributed in amplifying the occurrences of chromosomal aneuploidies. The normal individuals consisting of variations in the susceptible genes causing aneuploids in the population remain undetected until the disorder genes express in the succeeding generations.

Prevalence of BCL-2/J(H) Translocation in Healthy African Americans

The translocation t(14;18)(q32;q21) (BCL-2/J(H)) is present in over 80 % of all follicular lymphomas and is detectable in peripheral blood lymphocytes (PBL) of healthy individuals. The prevalence of this translocation has not been studied in African Americans (AAs). Given the higher incidence of follicular lymphomas in whites compared to AAs in the United States (USA), we hypothesized that the translocation prevalence in the blood of AAs would be lower. DNA was isolated from PBL from blood samples collected from participants from FL. Polymerase chain reaction was performed on the BCL-2/J(H) major (MBC) and minor breakpoint cluster (mBC) regions. Eight of the 77 (10.4 %) blood samples from AA participants were positive for MBC (95 % CI, 4.6-19.5 %), and three (3.9 %) were positive for mBC (95 % CI, 0.81-10.97 %) of BCL-2/J(H), with a total of 11 (14.3 %) participants with positive samples (95 % CI, 7.35-24.13 %). In 167 white patient samples, 22 (13.2 %; 95 % CI, 8.44-19.26 %) were positive for MBC, and five (3.0 %; 95 % CI, 0.98-6.85 %) were positive for mBC, with a total of 25 (15 %) participants with positive samples (CI, 9.93-21.30 %). The prevalence of t(14;18)(q32;q21) is not significantly different among AAs and whites from the USA. The lower prevalence of follicular lymphomas in AAs compared with whites is likely a result of differences in secondary molecular alterations involved in follicular lymphoma development. This study is the first report of prevalence of t(14;18) in an AA cohort.

Risk of follicular lymphoma associated with BCL2 translocations in peripheral blood

Many adults have circulating lymphocytes with the BCL2 gene translocation characteristic of follicular lymphoma. We therefore conducted a nested case-control study of incident lymphomas with peripheral blood obtained a median 4.9 years pre-diagnosis from the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Overall, 13 of 26 cases of lymphoma and 14 of 47 controls had BCL2 major breakpoint region (MBR) translocations in pre-diagnosis blood (odds ratio [OR] = 2.8). Nine cases had BCL2-MBR-positive tumors; eight of these nine had BCL2-MBR translocations in paired blood versus five of the 17 with BCL2-MBR-negative tumors (p = 0.01). Comparing both tumor types to controls, blood BCL2-MBR translocations had a strong, statistically significant association with BCL2-MBR-positive tumors (OR = 26), but not with BCL2-MBR-negative tumors (OR = 0.9). All eight BCL2-MBR-positive tumors with pre-diagnosis BCL2 translocations were clonally related to these circulating cells, based on similarity of recombination sequences. These data indicate that blood BCL2-MBR translocations represent lymphoma precursor clones with malignant potential.

Influence of reproductive history and exogenous hormone use on prevalence and frequency of circulating t(14;18)-positive cells in a population-based cross-sectional study

Purpose

The t(14;18) translocation might represent an intermediate step in the pathogenesis of follicular lymphoma (FL), one of the most common subtypes of non-Hodgkin lymphoma. Circulating t(14;18)-positive cells can also be detected in 30–60 % of healthy individuals at low frequencies. Some studies found a negative association between reproductive factors or use of menopausal hormone therapy (MHT) with FL. The objective of this study was to evaluate whether there is an association between number of frequencies, oral contraceptive (OC) use, menopausal status and MHT, and t(14;18) prevalence and frequency in a representative population analysis based on an epidemiologic study in the northeastern part of Germany.

Methods

The analysis is based on results of buffy coat samples from 1,981 women of the Study of Health in Pomerania (SHIP-0) and data obtained in standardized face-to-face interviews. For prevalence, odds ratios (OR) and 95 % confidence intervals (CI) were calculated using unconditional logistic regression. Frequency data were analyzed using negative binomial regression. The multivariable models included age, number of pregnancies, menopausal status (premenopausal, natural, medical/surgical menopause), OC use and MHT as a measure for exogenous hormone exposure use.

Results

We found no association between reproductive history and combined exogenous hormone use on the prevalence of circulating t(14;18)-positive cells. Modeling MHT and OC use separately in a sensitivity analysis, the MHT parameter yielded statistical significance [OR 1.37 (95 % CI 1.04;1.81)]. t(14;18) frequency was associated with use of OC [incidence rate ratio (IRR) for ever use 3.18 (95 % CI 1.54;6.54)], current use [IRR 3.86 (1.56;9.54)], >10 years use [IRR 3.93 (1.67;9.23)] and MHT [restricted to postmenopausal women; IRR 2.63 (95 % CI 1.01;6.85)] in bivariate age-adjusted analyses. In the multivariable model, medical/surgical menopause [IRR 2.46 (1.11;5.44)] and the category ever use of OC and MHT were statistically significant [IRR 2.41 (1.09;5.33)].

Conclusions

Exogenous hormone use might be a risk factor for t(14;18) frequency rather than for t(14;18) prevalence. Further research on healthy individuals carrying a t(14;18) translocation and possible risk factors for malignant lymphoma is necessary to determine the additional molecular or immunological events that have to occur to develop FL.

Electronic supplementary material

The online version of this article (doi:10.1007/s10552-015-0525-4) contains supplementary material, which is available to authorized users.

Chromosomal translocations among the healthy human population: implications in oncogenesis

Chromosomal translocations are characteristic features of many cancers, especially lymphoma and leukemia. However, recent reports suggest that many chromosomal translocations can be found in healthy individuals, although the significance of this observation is still not clear. In this review, we summarize recent studies on chromosomal translocations in healthy individuals carried out in different geographical areas of the world and discuss the relevance of the observation with respect to oncogenesis.

Assessment of BCL2/J(H) translocation in healthy individuals exposed to low-level radiation of 137CsCl in Goiânia, Goiás, Brazil

Healthy radio-exposed individuals who received low levels of Cesium-137 radiation during the accident that occurred in Goiânia in 1987, their families and controls were tested for the detection of t(14;18)-rearranged B cells in peripheral blood by using a highly sensitive, real-time quantitative PCR method. The chromosomal translocation t(14;18)(q32;q21) is characteristic of follicular lymphoma and is a frequent abnormality observed in other types of non-Hodgkin's lymphoma. This translocation leads to constitutive activation of the BCL2 oncogene by the enhancers of the immunoglobulin heavy-chain locus. In healthy individuals, the same translocation may also be found in a small fraction of peripheral blood lymphocytes, and positive cells might serve as an indicator for environmental exposure to carcinogens and possibly correlate with the cumulative risk of developing t(14;18)- positive non-Hodgkin's lymphoma. Twenty healthy radio-exposed individuals, 10 relatives and 10 non-exposed healthy individuals were tested for the detection of this translocation. Only 1 non-exposed individual was positive for the chromosomal translocation, and healthy radio-exposed individuals presented lower levels of cells bearing the BCL2/J(H) rearrangement when compared to the levels of the patients with follicular lymphoma before treatment. However, evaluation of more cells would be required to confirm the total absence of circulating cells bearing BCL2/J(H) rearrangement.

[Leukemia- and lymphoma-associated flow cytometric, cytogenetic, and molecular genetic aberrations in healthy individuals]

Most leukemia and lymphoma cases are characterized by specific flow cytometric, cytogenetic and molecular genetic aberrations, which can also be detected in healthy individuals in some cases. The authors review the literature concerning monoclonal B-cell lymphocytosis, and the occurrence of chromosomal translocations t(14;18) and t(11;14), NPM-ALK fusion gene, JAK2 V617F mutation, BCR-ABL1 fusion gene, ETV6-RUNX1(TEL-AML1), MLL-AF4 and PML-RARA fusion gene in healthy individuals. At present, we do not know the importance of these aberrations. From the authors review it is evident that this phenomenon has both theoretical and practical (diagnostic, prognostic, and therapeutic) significance.

Role of activation-induced cytidine deaminase in the progression of follicular lymphoma

Activation-induced cytidine deaminase (AID/AICDA) is required for somatic hypermutation and class-switch recombination of the immunoglobulin gene, and for c-myc translocation of germinal center-derived B-cell lymphoma. In the present study, we attempted to clarify the significance of AID associated with c-myc in the progression of follicular lymphoma (FL) using RT-PCR and quantitative real-time PCR. Tissues from the patients with grade 3 FL expressed relatively higher levels of c-myc and AID. The samples taken from a patient with FL who died within 2 years after the start of treatment showed either no or low expression of AID, despite expressing high levels of c-myc. In order to examine the role of AID expression in rapidly progressive FL, the full-length AID transcript was transfected into AID-negative cell lines established from different patients with rapidly progressive FL. This led to the establishment of AID-expressing transfectants with a low proliferation rate and a significantly increased incidence of G(0)/G(1) arrest compared with controls. Our results indicate that AID may act as a negative regulator of cell survival in FL when sufficient c-myc is expressed. Switch-off or low expression of AID after c-myc amplification may correlate with the clinical outcomes of FL.

Follicular lymphoma in situ: clinical implications and comparisons with partial involvement by follicular lymphoma

Follicular lymphoma in situ (FLIS) was first described nearly a decade ago, but its clinical significance remains uncertain. We reevaluated our original series and more recently diagnosed cases to develop criteria for the distinction of FLIS from partial involvement by follicular lymphoma (PFL). A total of 34 cases of FLIS were identified, most often as an incidental finding in a reactive lymph node. Six of 34 patients had prior or concurrent FL, and 5 of 34 had FLIS composite with another lymphoma. Of patients with negative staging at diagnosis and available follow-up (21 patients), only one (5%) developed FL (follow-up: median, 41 months; range, 10-118 months). Follow-up was not available in 2 cases. Fluorescence in situ hybridization for BCL2 gene rearrangement was positive in all 17 cases tested. PFL patients were more likely to develop FL, diagnosed in 9 of 17 (53%) who were untreated. Six patients with PFL were treated with local radiation therapy (4) or rituximab (2) and remained with no evidence of disease. FLIS can be reliably distinguished from PFL and has a very low rate of progression to clinically significant FL. FLIS may represent the tissue counterpart of circulating t(14;18)-positive B cells.

Aberrant anaplastic lymphoma kinase activity induces a p53 and Rb-dependent senescence-like arrest in the absence of detectable p53 stabilization

Anaplastic Lymphoma Kinase (ALK) is a receptor tyrosine kinase aberrantly expressed in a variety of tumor types, most notably in Anaplastic Large Cell Lymphoma (ALCL) where a chromosomal translocation generates the oncogenic fusion protein, Nucleophosmin-ALK (NPM-ALK). Whilst much is known regarding the mechanism of transformation by NPM-ALK, the existence of cellular defence pathways to prevent this pathological process has not been investigated. Employing the highly tractable primary murine embryonic fibroblast (MEF) system we show that cellular transformation is not an inevitable consequence of NPM-ALK activity but is combated by p53 and Rb. Activation of p53 and/or Rb by NPM-ALK triggers a potent proliferative block with features reminiscent of senescence. While loss of p53 alone is sufficient to circumvent NPM-ALK-induced senescence and permit cellular transformation, sole loss of Rb permits continued proliferation but not transformation due to p53-imposed restraints. Furthermore, NPM-ALK attenuates p53 activity in an Rb and MDM2 dependent manner but this activity is not sufficient to bypass senescence. These data indicate that senescence may constitute an effective barrier to ALK-induced malignancies that ultimately must be overcome for tumor development.

The essential role of evasion from cell death in cancer

The link between evasion of apoptosis and the development of cellular hyperplasia and ultimately cancer is implicitly clear if one considers how many cells are produced each day and, hence, how many cells must die to make room for the new ones (reviewed in Raff, 1996). Furthermore, cells are frequently experiencing noxious stimuli that can cause lesions in their DNA and faults in DNA replication can occur during cellular proliferation. Such DNA damage needs to be repaired efficiently or cells with irreparable damage must be killed to prevent subsequent division of aberrant cells that may fuel tumorigenesis (reviewed in Weinberg, 2007). The detection of genetic lesions in human cancers that activate prosurvival genes or disable proapoptotic genes have provided the first evidence that defects in programmed cell death can cause cancer (Tagawa et al., 2005; Tsujimoto et al., 1984; Vaux, Cory, and Adams, 1988) and this concept was proven by studies with genetically modified mice (Egle et al., 2004b; Strasser et al., 1990a). It is therefore now widely accepted that evasion of apoptosis is a requirement for both neoplastic transformation and sustained growth of cancer cells (reviewed in Cory and Adams, 2002; Hanahan and Weinberg, 2000; Weinberg, 2007). Importantly, apoptosis is also a major contributor to anticancer therapy-induced killing of tumor cells (reviewed in Cory and Adams, 2002; Cragg et al., 2009). Consequently, a detailed understanding of apoptotic cell death will help to better comprehend the complexities of tumorigenesis and should assist with the development of improved targeted therapies for cancer based on the direct activation of the apoptotic machinery (reviewed in Lessene, Czabotar, and Colman, 2008).

Cytogenetic instability in childhood acute lymphoblastic leukemia survivors

Contemporary anticancer therapies have largely improved the outcome for children with cancer, especially for Acute Lymphoblastic Leukemia (ALL). Actually, between 78% and 85% of patients achieve complete remission and are alive after 5 years of therapy completion. However, as cure rates increase, new concerns about the late effects of genotoxic treatment emerge, being the risk of developing secondary neoplasias, the most serious life-threatening rising problem. In the present paper, we describe and review the cytogenetic findings in peripheral lymphocytes from ALL survivors, and discuss aspects associated to the occurrence of increased chromosome rearrangements in this growing cohort.

Genomic profiles in B cell lymphoma

Chromosome translocations found in B cell lymphomas generate typical genome profiles that are characteristic of each disease entity. The mechanisms of lymphomagenesis have been investigated with respect to the involvement of deregulated genes in tumor development, as characterized by the promotion of cell proliferation and the blockage of cell differentiation and anti-apoptosis. It is now well known that chromosome translocation alone does not induce tumor formation. New technology such as array CGH and expression profiling introduced as a result of the human genome project introduced a new paradigm from which to understand the molecular mechanisms of lymphoma development. Analyses with this new technology revealed that genome profiles of disease entities are characteristic and differ from disease to disease, although the genome profile of each patient with the same disease entity varies significantly given the recurrent genetic alterations frequently found. These apparent paradoxical findings are likely to be the cause of heterogeneity of the clinicopathological features associated with the same disease entity. Based on these findings, the future prospect and direction of lymphoma research will be discussed.

Diversity of genome profiles in malignant lymphoma

Characteristic chromosome translocations are associated with specific disease entities, and are known to play a pivotal role in lymphoma development. Chromosome translocation alone, however, is not sufficient to produce tumors. Factors including the microenvironment and epigenetic and genetic alterations other than chromosome translocations have been shown to play a role in lymphoma development. Follicular lymphoma cells proliferate in close contact with follicular dendritic cells. Mucosa-associated lymphoid tissue (MALT) lymphoma cells proliferate at the marginal zone area of reactive follicles which are formed by preceding chronic inflammation. The importance of genetic alterations other than chromosome translocation has been recognized since the introduction of array comparative genomic hybridization (array CGH). Variations in the genomic profile among patients with the same disease entity have been found by array CGH analyses. These variations indicate that multiple genetic pathways leading to the development of lymphomas may exist and hence result in the variable clinicopathological features observed.

Distinctive cell properties of B cells carrying the BCL2 translocation and their potential roles in the development of lymphoma of germinal center type

The BCL2/IGH translocation is a hallmark of follicular lymphoma and germinal center B-cell type diffuse large B-cell lymphoma. Although a strong determinant of these histological subtypes, this translocation is insufficient by itself for lymphomagenesis, so that other genetic alterations are required. To clarify how the BCL2 translocation contributes to the development of specific lymphoma subtypes, we used chimeric mouse models and a bone marrow transplantation system to examine the biological features of BCL2-overexpressing B cells. These cells showed a cell-autonomous differentiation preference for follicular B cells. Their cell cycle progression was enhanced in wild-type but not in Emu-BCL2 transgenic mice, indicating that the low proliferative activity of B cells in Emu-BCL2 transgenic mice is partly due to their specific microenvironment, which is caused by the abnormal B cells themselves. Moreover, in vitro experiments demonstrated that Emu-BCL2(+) B cells have reduced responsiveness to terminal differentiation stimulation. According to these results, we hypothesize that B cells that have undergone BCL2/IGH translocation might possibly be forced to localize in follicles, and accumulate genetic abnormalities by being subjected to recurrent stimulation. Our findings lead us to propose that B cells carrying the BCL2/IGH translocation comprise a distinctive cell population that leads to the development of germinal center B-cell type lymphoma.

Multiplex PCR for the detection of BCL-1/IGH and BCL-2/IGH gene rearrangements--clinical validation in a prospective study of blood and bone marrow in 258 patients with or suspected of non-Hodgkin's lymphoma

We have designed a multiplex PCR, which allows for fast and high throughput demonstration of the BCL-1/IGH and BCL-2/IGH fusion DNA observed primarily in mantle cell- and follicular non-Hodgkin's lymphoma (NHL). Blood (PB) and/or bone marrow (BM) from 258 patients suspected of NHL have prospectively been evaluated. Eleven patients (4%) were found t(11;14)+ and 37 patients (14%) t(14;18)+. Comparing these results to standard diagnostic methods of PB and/or BM identified PCR+ samples that were normal by morphology (BCL-1/IGH: 1/11; BCL-2/IGH: 17/37). Equally important, patients who were not clonal in PB and/or BM by flow cytometry were identified as PCR+ (BCL-1/IGH: 3/11; BCL-2/IGH: 23/37). We conclude that this multiplex approach allows for easy and sensitive molecular determination of molecular lesions in NHL, which have diagnostic and prognostic importance.

Chromosome instability in lymphocytes of children with coeliac disease

Undiagnosed individuals with celiac disease (CD) or those who do not comply with gluten-free diet (GFD) are at a higher risk of developing malignancies. A possible origin of chromosomal alteration in autoimmune reaction could be mistakes in the rearrangement of V(D)J of the IgH gene. Our aim was to verify whether higher genomic instability was found in coeliac individuals and whether GFD reduced it. As marker of genomic instability we analysed the frequency of 2 translocations, t(14;18) and t(11;14), in peripheral blood by nested PCR, in 37 patients with CD at diagnosis, 27 patients with CD after 2 years on GFD, and 36 control individuals. No significant differences were found.

MLL leukemia-associated rearrangements in peripheral blood lymphocytes from healthy individuals

Chromosomal translocations are characteristic of hematopoietic neoplasias and can lead to unregulated oncogene expression or the fusion of genes to yield novel functions. In recent years, different lymphoma/leukemia-associated rearrangements have been detected in healthy individuals. In this study, we used inverse PCR to screen peripheral lymphocytes from 100 healthy individuals for the presence of MLL (Mixed Lineage Leukemia) translocations. Forty-nine percent of the probands showed MLL rearrangements. Sequence analysis showed that these rearrangements were specific for MLL translocations that corresponded to t(4;11)(q21;q23) (66%) and t(9;11) (20%). However, RT-PCR failed to detect any expression of t(4;11)(q21;q23) in our population. We suggest that 11q23 rearrangements in peripheral lymphocytes from normal individuals may result from exposure to endogenous or exogenous DNA-damaging agents. In practical terms, the high susceptibility of the MLL gene to chemically-induced damage suggests that monitoring the aberrations associated with this gene in peripheral lymphocytes may be a sensitive assay for assessing genomic instability in individuals exposed to genotoxic stress.

Prevalence and frequency of circulating t(14;18)-MBR translocation carrying cells in healthy individuals

The t(14;18) translocation is a common genetic aberration that can be seen as an early step in pathogenesis of follicular lymphoma (FL). The significance of low level circulating t(14;18)-positive cells in healthy individuals as clonal lymphoma precursors or indicators of risk is still unclear. We determined the age dependent prevalence and frequency of BCL2/IgH rearrangements in 715 healthy individuals ranging from newborns to octo- and nonagenarians. These results were compared with number of circulating t(14;18)-positive cells in 108 FL patients at initial presentation. The overall prevalence of BCL2/IgH junctions in this large sample was 46% (327/715). However, there was a striking dependence upon age. Specifically, among individuals up to 10 years old, none had detectable circulating t(14;18)-positive cells. In the age groups representing 10-50 years old, we found a steady elevation in the prevalence of BCL2/IgH junctions up to a prevalence of 66%. Further increases of the prevalence in individuals older than 50 years were not seen. The mean frequency of BCL2/IgH junctions in healthy individuals > or =40 years (18-26 x 10(-6)) was significantly higher than in younger subjects (7-9 x 10(-6)). Four percent (31/715) of individuals carried more than one t(14;18)-positive cell per 25,000 peripheral blood mononuclear cells (PBMNCs). In comparison, 108 stage III/IV FL patients had a median number of circulating t(14;18)-positive malignant FL cells of about 9200/1 million PBMNCs (range 7-1,000,000). These findings will further improve the understanding of the relevance of t(14;18)-positive cells in healthy individuals as a risk marker toward the development into lymphoma precursors.

t(14;18) Translocations and risk of follicular lymphoma

The chromosomal translocation t(14;18)(q32;q21) is characteristic of follicular lymphoma and a frequent abnormality in other types of non-Hodgkin lymphoma (NHL). In healthy individuals, the same translocation may also be found in a small fraction of peripheral blood lymphocytes, the biological significance of which is beginning to be explored. Translocation prevalence and frequency are potential risk factors for developing NHL. Here, we review the published data and describe recent and ongoing work on this promising biomarker. We have a series of studies in four major areas: 1) t(14;18) prevalence and frequency in healthy individuals; 2) maturation of translocation-harboring cells; 3) effect of rituximab treatment on t(14;18) carriage; and 4) predictive and clonotypic relationship between t(14;18) and follicular lymphoma or other NHL. Further studies are warranted to increase understanding of this crucial molecular event in the development of hematopoietic malignancies. Potential applications include determination of elevated risk for lymphoma, early detection of disease, and identification of molecular targets for preventive interventions.

Age-dependent prevalence and frequency of circulating t(14;18)-positive cells in the peripheral blood of healthy individuals

Circulating t(14;18)-positive cells were detected by quantitative real-time polymerase chain reaction on DNA isolated from peripheral blood mononuclear cells (PBMNCs) from 644 healthy individuals between <1 and 91 years of age. In all, 45% of all samples (287/644) were positive, and 40% of the positive samples (114/287) contained more than one positive clone. The prevalence of t(14;18)-positive cells showed a strong correlation with age. A total of 36 cord blood samples and 48 PBMNCs from children <10 years were negative. The prevalence of circulating positive cells increased from the second to fifth decade of life from 20% to 66% and remained stable thereafter. Also the median frequency of circulating t(14;18)-positive cells as well as the prevalence of multiple clones showed an increase with age. In all, 4% (24/644) of all blood samples contained >1 positive cell in 25,000 cells, a finding restricted to healthy individuals >40 years. These results are discussed in relation to the low incidence of follicular lymphoma.

Distribution of t(14;18)-positive, putative lymphoma precursor cells among B-cell subsets in healthy individuals

The t(14;18)(q32;q21) is the characteristic chromosomal translocation of follicular lymphoma (FL). Highly sensitive polymerase chain reaction (PCR) techniques can also detect t(14;18)-sequences in the blood and lymphoid tissues of healthy individuals (HI). The aim of this study was to determine the immunophenotypic markers of t(14;18)-positive cells in HI and to relate these features to lymphocyte maturation. B cells from 10 subjects with t(14;18)-positive and three subjects with t(14;18)-negative peripheral blood mononuclear cells (PBMC) were fluorescence-activated cell sorted for antigen-naïve (CD27(-)), immunoglobulin M (IgM) memory (IgM(+)CD27(+)) and switched memory (IgM(-) CD27(+)) cells. t(14;18)-recombinations were detected by quantitative PCR. Among PBMC-positive subjects, t(14;18)-frequency was significantly higher in IgM memory (median: 380/10(6)) than in antigen-naïve (median: 16/10(6)) or switched memory (median: 5/10(6)) B cells. All PBMC-negative subjects nevertheless had detectable t(14;18) in sorted B cells; levels were lower than in PBMC-positive subjects, but had the same relative predominance. These results suggest that t(14;18) is generated during early B-cell development in the bone marrow and that affected cells may mature and expand in germinal centres. t(14;18)-frequency was highest in IgM memory cells, a B-cell subset that shares immunophenotypic similarities with FL. The significance of these cells as lymphoma precursors or indicators of lymphoma risk remains to be established.

Cells carrying nonlymphoma-associated bcl-2/IgH rearrangements (NLABR) are phenotypically related to follicular lymphoma and can establish as long-term persisting clonal populations

OBJECTIVE

Nonlymphoma-associated bcl-2/IgH rearrangements (NLABRs) are frequently amplified by PCR in blood of lymphoma-free subjects (LFS), but the temporal kinetics and phenotypic nature of NLABR-positive cells are unknown. To address these issues we prospectively monitored a panel of NLABR-positive LFS.

METHODS

LFS have been studied by nested PCR, real-time PCR, and DNA sequencing. Cell selection studies were also performed to define the nature of NLABR-bearing clones.

RESULTS

Of 125 donors, 16 (12.8%) were found to be bcl-2/IgH positive and were monitored at least every 6 months for a median time of 22 months (range 6-50). In half of the subjects the same NLABR detected initially was again reamplified at follow-up thrice or more. In 5, the same NLABR was constantly amplified in every follow-up sample. With a median follow-up of 22 months (range 9-50), no stable disappearance of a recurrent clone has been so far recorded. Real-time PCR indicated that persistent NLABR-positive clones are stable over time in the same subject. Cell separation studies indicate that NLABRs belong to CD19+, CD5-, CD23-, CD10+/- cells.

CONCLUSIONS

Our results indicate that NLABR-positive clones are persistent populations phenotypically related to follicular lymphoma (FL). This suggests the existence of a FL-related clonal expansion of undetermined significance, which might be either a premalignant or a nonmalignant counterpart of FL.

The bcl-2/IgH rearrangement in a population of 204 healthy individuals: Occurrence, age and gender distribution, breakpoints, and detection method validity

This study assessed prevalence, frequency, age and gender distribution and breakpoint locations, and detection method validity for the bcl-2/IgH rearrangement in 204 healthy individuals. For this purpose, both classic two-step, nested, semi-quantitative PCR as well as a newly established sequence-specific, hybridization probe-based real-time quantitative PCR (RQ-PCR) were employed and tested for their sensitivity and specificity for detecting t(14;18) positive cells in healthy blood donors. Interestingly, almost a quarter (24%; 39/204) of all healthy individuals carried the translocation, confirming data of one large prior report [Summers KE, Goff LK, Wilson AG, Gupta RK, Lister TA, Fitzgibbon J. Frequency of the Bcl-2/IgH rearrangement in normal individuals: implications for the monitoring of disease in patients with follicular lymphoma. J Clin Oncol 2001;19(2):420-4]. Regarding presence as well as frequency of the translocation, no correlation to age (mean frequency 2.0:10(4), with a median of <l:10(4), for <40 years, and mean frequency 1.9:10(4), with a median of <l:10(4) for individuals>or=40 years) nor gender was detected. Comparing the two PCR approaches, a 95.1% concordance (194/204) regarding t(14;18) detection was determined for nested and RQ-PCR, with nested PCR being slightly more sensitive (reproducible detection limit l:10(5) cells versus 1:10(4); maximum detection limit l:10(6) versus 1:10(5)). Sequence analysis confirmed individual breakpoints for all samples analyzed (29/29), indicating detection validity for both PCR approaches and ruling out contamination. The breakpoint location distribution pattern appeared to be comparable to the pattern seen with follicular lymphoma (FL) patient collectives. In conclusion, clonal bcl-2/IgH rearrangements are indeed a very frequent observation in healthy individuals, and appear to be independent of age and gender in regard to presence and frequency. This represents a conflicting finding in context of potential biological significance, and presents a potential disruptive factor for minimal residual disease (MRD) monitoring in FL patients. Prospective future trials will have to clarify the biological significance of this important observation.

HCV-associated B cell clonalities in the liver do not carry the t(14;18) chromosomal translocation

Infection with HCV can be associated with B-cell non-Hodgkin lymphoma. Polymerase chain reaction (PCR) amplification assays for Bcl-2/IgH rearrangement were performed on nucleic acids extracted from portal tract inflammatory infiltrates, isolated with laser capture microdissection (LCM), from liver biopsy sections of 16 hepatitis C virus (HCV)-infected patients with and without extrahepatic B cell-related disorders. Results were compared with total DNA extracted from core liver biopsy specimens and from peripheral blood mononuclear cells (PBMCs). We failed to demonstrate specific Bcl-2/IgH amplicons either in liver tissue or in PBMCs in all patients of the current series. Multiple PCR assays for variable diversity joining (VDJ) IgH gene rearrangements were also performed in the liver compartment. Selective amplification compatible with mono or oligoclonal B cell clonotypes was demonstrated in 80% (6/8) and 25% (2/8) of patients with and without clinical evidence of B-cell disorders. V(H)1 and V(H)3 were the most represented V(H) families. In situ expression of Bcl-2 protein was carried out by immunohistochemistry on liver biopsy sections. Bcl-2 protein was detected in 2 (12.5%) patients who did not associate extrahepatic disorders. In conclusion, current data support the concept that production of IgH gene rearrangements is not associated with Bcl-2/IgH chromosomal translocation in hepatic compartment. Liver overexpression of Bcl-2 protein may occur in at least a minor proportion of HCV-infected patients.

Chromosomal aberrations in follicular non-Hodgkin lymphomas of Japanese patients, detected with comparative genomic hybridization and polymerase chain reaction analysis

The t(14;18)(q32.3;q21), hallmark of follicular lymphoma (FL), is less frequently observed in Asian patients than in Westerners. Little is known about additional chromosomal aberrations in Asian FL patients. We applied comparative genomic hybridization (CGH) to screen for genomic imbalances in 32 biopsy samples from 23 Japanese patients with nodal FL. The t(14;18) was assessed with polymerase chain reaction (PCR) using primers for the major (MBR), 3'MBR, minor (mcr), 5'mcr, and intermediate breakpoint cluster regions (icr). In 17 of 23 patients, CGH analyses detected genomic imbalances. Gains frequently affected chromosomes 18p (6 of 23), X (5 of 23), 5 (4 of 23), 12 (4 of 23), 2 (3 of 23), and 16 (3 of 23). The only recurrent loss affected chromosome 6q (2 of 23). A t(14;18) was detected in 13 of 23 patients (56.5%). Breakpoints were located in the MBR (10 patients), in the 3'MBR, in the mcr, and in the icr (1 patient each). The frequency of aberrations detected by CGH as well as relapse-free survival were not distinctly different between patients with and without a t(14;18). In summary, no significant difference in the overall frequency of aberrations compared with Westerners was found. Despite the extended primer set used, the frequency of PCR-detected t(14;18) remained low. Additional studies are required to assess the reasons for geographic variation in FL.

The implication of follicular lymphoma patients receiving allogeneic stem cell transplantation from donors carrying t(14;18)-positive cells

We performed real-time quantitative polymerase chain reaction (RQ-PCR) in peripheral blood (PB) and/or bone marrow (BM) samples collected pre- and post transplant from 23 recipient-donor pairs receiving allogeneic stem cell transplantation (allo-SCT) for follicular lymphoma (FL). Of 23 donors, 11 had a PB and/or BM sample positive for t(14;18) (BCL2/IGH fusion) at low levels (<one t(14;18) cell in 10K total cells). Recipients from donors with (n=11) and those without (n=12) detectable t(14:18) cells were similar in age, sex, and disease status pretransplant. No differences in the incidence of graft-versus-host-disease (GVHD), delayed engraftment, relapse rate, disease-free survival and overall survival were identified between the groups. Two recipients without detectable t(14;18) cells pre-transplant showed detectable t(14;18) cells at 2 and 11 years after receiving grafts from donors with t(14:18) cells. Neither patient developed FL 1.5 and 2 years after the emergence of t(14;18) cells. Although the sample size is relatively small, our findings suggest that individuals carrying t(14;18) cells may not be excluded as donors given the lack of an association of t(14;18) detected in donors with adverse clinical outcome. It may be necessary to screen for the donor's t(14;18) status before using t(14;18) for monitoring minimal residual disease by RQ-PCR to exclude the possibility of confounding donor's t(14;18) clone.

Genetic and epigenetic factors involved in B-cell lymphomagenesis

Malignant lymphomas have been classified by the WHO into disease categories based not only on histological features, but also on cell surface markers, cytogenetic and clinical features. It is known that chromosome translocation plays an important role in lymphoma development, but it is not entirely clear yet why a given type of chromosome translocation is associated with a specific type of lymphoma. This review deals with molecular mechanisms of B-cell lymphoma development in association with chromosome translocations. The outcome of chromosome translocations can be categorized into three factors: enhancement of proliferation, inhibition of differentiation and anti-apoptotic activity. It is well known that chromosome translocation by itself cannot cause cells to become malignant because it is only one of the growth advantages leading to malignancy, while additional genetic and epigenetic alterations are required for cells to become fully malignant. Mucosa-associated lymphoid tissue (MALT) lymphomas of the stomach are unique in that a majority can be cured by Helicobacter pylori eradication, although 20 to 30% remain resistant. Others as well as we have demonstrated that the presence of the API2-MALT1 chimeric gene correlates well with resistance to H. pylori eradication treatment. These characteristics have led to the speculation that the classification of MALT lymphoma falls somewhere between tumor and inflammation. Although MALT lymphoma seems to have unique features in comparison with other types of B-cell lymphomas, it shares common molecular mechanisms with B-cell lymphoma development.

Detection of bone marrow infiltration of lymphoma cells by fluorescence in situ hybridization

BACKGROUND

It is sometimes difficult to detect the bone marrow infiltration of lymphoma cells, because lymphoma cells are not distinguishable from normal lymphocytes due to the similarity of their phenotype.

METHODS

Bone marrow involvement of 17 samples of 15 patients with follicular lymphoma, whose lymphoma cells were confirmed to harbor the translocation of chromosome14q32, were examined by microscopic analysis of bone marrow smear and biopsy, flow cytometorical analysis (FCM), chromosomal analysis of G-banding and fluorescence in situ hybridization (FISH). FISH was performed using a probe, which detects the split of IGH gene on 14q32.

RESULTS

The positivity of FISH was highest among these methods and FISH was able to detect the bone marrow involvement in one case who was defined as negative by bone marrow biopsy.

CONCLUSIONS

FISH can be used for detection of bone marrow involvement of malignant lymphoma that carries chromosomal rearrangement involving 14q32.

Recurrence of Bcl-2/IgH polymerase chain reaction positivity following a prolonged molecular remission can be unrelated to the original follicular lymphoma clone

OBJECTIVE

The aim of this study was to evaluate whether reappearance of polymerase chain reaction (PCR) positivity for the Bcl-2/IgH translocation following a phase of molecular remission in autografted follicular lymphoma (FL) patients is always associated with reappearance of the original neoplastic clone.

PATIENTS AND METHODS

The molecular follow-up of 119 autografted Bcl-2/IgH positive patients was evaluated by nested PCR. In case of molecular recurrence, direct sequencing of involved rearrangements has been performed both at diagnosis and at the time of recurrence. The two sequences then were compared in terms of breakpoints, N insertions, and JH usage.

RESULTS

Seventy-five patients achieving molecular remission were identified in our patient sample (63%). Of these patients, eight (10.6%) experienced molecular recurrence. Direct sequencing of the Bcl-2/IgH translocation performed at diagnosis and recurrence showed identical rearrangements in six subjects and unrelated rearrangements in two. As opposed to most true molecular relapses, unrelated rearrangements always occurred several years after transplantation. To date, the two subjects carrying unrelated rearrangements show no signs of active lymphoproliferative disease.

CONCLUSIONS

This report is the first evidence that Bcl-2/IgH rearrangements unrelated to the original tumor clone can lead to false-positive results during the molecular follow-up of autografted FL patients. Based on these results, we recommend confirmation by direct sequencing, at least for patients experiencing molecular relapse 2 or more years after the end of treatment. This will be particularly important for patients enrolled in clinical trials that schedule additional treatment in case of molecular evidence of persistent disease activity.

Measurement of SIL-TAL1 fusion gene transcripts associated with human T-cell lymphocytic leukemia by real-time reverse transcriptase-PCR

TAL1 disruption at 1p32 [del(1p)] is a common rearrangement in the development of T-cell acute lymphocytic leukemia (T-ALL). The del(1p) are usually interstitial 90kb deletions placing TAL1 under control of the SCL interrupting locus (SIL) gene forming the SIL-TAL1 fusion product. A reverse transcriptase real-time PCR assay to quantify SIL-TAL1 fusion genes is described. A SIL-TAL1 fusion gene RNA transcript was built that permitted absolute standard curves to be generated. Sensitivity of the RT-PCR assay was determined to be 10 cells (CEM cell line) in 10(6) human lymphocytes. Peripheral blood lymphocytes from 10 healthy adults and 10 neonates were assayed. None of the samples showed any SIL-TAL1 expression. However, when lymphocytes from three adults were cultured in vitro the SIL-TAL1 transcript was detectable in the RNA isolates. No RAG2 expression was detected in these expanded samples, suggesting that the clones bearing the SIL-TAL1 fusion gene may have existed at low levels prior to the ex vivo expansion.

Chromosomal translocation t(14;18) in healthy individuals

The t(14;18)-translocation can frequently detected in the peripheral blood and tissue samples from healthy individuals. If the sensitivity of the assay used for the detection is high enough in almost all healthy individuals one or multiple cell clones carrying the t(14;18)-translocation can be found with a frequency of 1-100 rearranged cells in 10(6) normal cells. The frequency of these cells seems to be increased with age and smoking habits measured in pack years. The prevalence in Asian (Japanese) individuals appears to be lower than in Caucasians. It has been postulated that this translocation is a primary event for the subsequent development of a follicular lymphoma.

BCL-2/JH translocation in peripheral blood lymphocytes of unexposed individuals: lack of seasonal variations in frequency and molecular features

BCL-2/J(H) rearrangement has been proposed as a biomarker for evaluating the genotoxicity of occupational and environmental exposures. Available data on time-related modification of this rearrangement in peripheral blood lymphocytes in unexposed healthy individuals is scarce. We investigated the characteristics of BCL-2/J(H) rearrangements in 33 adults unexposed to genotoxins at 2 seasonal time points: winter and spring. BCL-2/J(H) rearrangement was detected in 79% of individuals (detection limit = 8.48 x 10(-8)). Its frequency ranged from <1 to 40 translocations per million lymphocytes with a significant (p = 0.04) positive correlation with age. No significant modifications of BCL-2/J(H) rearrangement frequency or in the number of clones harboring this rearrangement were observed according the 2 time points. No obvious influence of season-related environmental factors on frequency or molecular features of BCL-2/J(H) rearrangements was found in this population suggesting that this would not be a confounding factor.

PCR-detectable nonneoplastic Bcl-2/IgH rearrangements are common in normal subjects and cancer patients at diagnosis but rare in subjects treated with chemotherapy

PURPOSE

To assess whether nonneoplastic Bcl-2/IgH rearrangements act as a confounding factor in the setting of minimal residual disease analysis by evaluating their incidence in a panel of lymphoma-free subjects, including cancer-free donors and chemotherapy-naive and chemotherapy-treated cancer patients.

PATIENTS AND METHODS

A total of 501 nonlymphoma subjects have been assessed: 258 cancer-free patients and 243 patients with malignancies other than lymphoma, 112 of whom were chemotherapy-naive. Patients were primarily assessed by nested polymerase chain reaction (PCR), followed by real-time quantitative PCR if they scored positive. In addition, six initially PCR-positive cancer-free donors were prospectively reassessed by qualitative and quantitative PCR after 30 and 60 days.

RESULTS

The overall incidence of Bcl-2/IgH positivity was 9.6%, with a median number of 11 rearrangements per 1,000,000 diploid genomes (range, 0 to 2,845 rearrangements), as assessed by real-time PCR. The incidence was similar in healthy subjects and cancer patients at diagnosis (12% and 12.5%; P = not significant). In contrast, the incidence of this translocation was only 2.3% in chemotherapy-treated patients (P <.001). In addition, three initially PCR-positive cancer-free donors showed persistence of their rearrangements when assessed after 30 and 60 days.

CONCLUSION

The low incidence of nonneoplastic Bcl-2/IgH rearrangements following chemotherapy provides further evidence of the prognostic role of persistent PCR-positivity in the posttreatment molecular follow-up of follicular lymphoma patients.