A single-centre, real-world study of BTK inhibitors for the initial treatment of MYD88mut /CD79Bmut diffuse large B-cell lymphoma

BACKGROUND

MCD (MYD88L265P /CD79Bmut ) diffuse large B-cell lymphoma has a poor prognosis. There is no published clinical research conclusion regarding zanubrutinib or orelabrutinib for the initial treatment of MCD DLBCL.

AIMS

This study aimed to analyse the efficacy and safety of Bruton's tyrosine kinase inhibitor (BTKi) (zanubrutinib or orelabrutinib) therapy for newly diagnosed DLBCL patients with MYD88mut and/or CD79Bmut .

MATERIALS AND METHODS

Twenty-three newly diagnosed DLBCL patients with MYD88mut and/or CD79Bmut from June 2020 to June 2022 received BTKi combined with rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) or rituximab + lenalidomide (R2 ). A control group of 17 patients with MYD88mut and/or CD79Bmut DLBCL who received the standard R-CHOP therapy was also assessed. We retrospectively analysed clinical characteristics, safety, overall response rate (ORR), complete response (CR) rate and progression-free survival (PFS) of the two groups.

RESULTS

The main clinical features were a high International Prognostic Index (IPI) score (≥3, 22/40, 55%) and a high rate of extranodal involvement (27/40,67.5%). Among the 23 DLBCL patients, 18 received BTKi + R-CHOP, and five elderly DLBCL patients were treated with BTKi + R2 . Compared with those in the control group (ORR 70.6%, CRR 52.9%, 1-year PFS rate 41.2%), improved ORR, CRR and PFS results were observed in the BTKi + R-CHOP group (100%, 94.4% and 88.9%, p = 0.019, 0.007, and 0.0001). In subgroup analyses based on genetic subtypes, cell origin, dual expression or IPI score, patients in the BTKi + R-CHOP group had better PFS than patients in the control group. In the BTKi + R-CHOP group, no significant difference was found in ORR, CRR and PFS based on subtype analysis, while BTKi-type subgroups exhibited statistically significant differences in 1-year PFS (p = 0.028). There were no significant differences in grade 3-4 haematological toxicity (p = 1) and grade 3-4 non-haematological toxicity (p = 0.49) between the BTKi + R-CHOP and R-CHOP treatment groups. In the BTKi + R2 group, the ORR was 100%, the CRR was 80%, and the 1-year PFS rate was 80%. The incidences of grade 3-4 haematologic toxicity and non-haematological toxicity were both 40%. No bleeding or cardiovascular events of grade 3 or higher occurred in any patients.

DISCUSSION

The efficacy of BTKi combined with R-CHOP was similar to previous reports, which was significantly better than R-CHOP alone. It is necessary to fully consider that 14 patients in the BTKi + R-CHOP group received a BTKi as maintenance therapy when evaluating efficacy. Meanwhile, the addition of a BTKi may improve the prognosis of non-GCB, DEL or high-IPI-score DLBCL patients with MYD88mut and/or CD79Bmut . In our study, five elderly DLBCL patients with MYD88mut and/or CD79Bmut were achieved better ORR, CRR, PFS than the historical data of R-miniCHOP treatment and Ibrutinib + R2 treatment. However, the efficacy and benefit of BTKis for this type of DLBCL need to be further analysed using a larger sample size.

CONCLUSION

This study suggests that newly diagnosed DLBCL patients with MYD88mut and/or CD79Bmut may benefit from BTKis according to real-world clinical data.

Mechanism of CD79A and CD79B Support for IgM+ B Cell Fitness through B Cell Receptor Surface Expression

The BCR consists of surface-bound Ig and a heterodimeric signaling unit comprised of CD79A and CD79B. Upon cognate Ag recognition, the receptor initiates important signals for B cell development and function. The receptor also conveys Ag-independent survival signals termed tonic signaling. Although the requirement of a CD79A/CD79B heterodimer for BCR complex assembly and surface expression is well established based on mice models, few studies have investigated this in human mature B cells. In this study, we found that human tonsillar B cells with high surface expression of IgM or IgG had potentiated BCR signaling compared with BCRlow cells, and high IgM expression in germinal center B cells was associated with reduced apoptosis. We explored the mechanism for IgM surface expression by CRISPR/Cas9-induced deletion of CD79A or CD79B in four B lymphoma cell lines. Deletion of either CD79 protein caused loss of surface IgM in all cell lines and reduced fitness in three. From two cell lines, we generated stable CD79A or CD79B knockout clones and demonstrated that loss of CD79A or CD79B caused a block in N-glycan maturation and accumulation of immature proteins, compatible with retention of BCR components in the endoplasmic reticulum. Rescue experiments with CD79B wild-type restored surface expression of CD79A and IgM with mature glycosylation, whereas a naturally occurring CD79B G137S mutant disrupting CD79A/CD79B heterodimerization did not. Our study highlights that CD79A and CD79B are required for surface IgM expression in human B cells and illuminates the importance of the IgM expression level for signaling and fitness.

Identification of 4-genes model in papillary renal cell tumor microenvironment based on comprehensive analysis

BACKGROUND

The tumor microenvironment acts a pivotal part in the occurrence and development of tumor. However, there are few studies on the microenvironment of papillary renal cell carcinoma (PRCC). Our study aims to explore prognostic genes related to tumor microenvironment in PRCC.

METHODS

PRCC expression profiles and clinical data were extracted from The Cancer Gene Atlas (TCGA) and Gene Expression Omnibus (GEO) database. Immune/stromal scores were performed utilizing the ESTIMATE algorithm. Three hundred fifty-seven samples were split into two groups on the basis of median immune/stromal score, and comparison of gene expression was conducted. Intersect genes were obtained by Venn diagrams. Hub genes were selected through protein-protein interaction (PPI) network construction, and relevant functional analysis was conducted by DAVID. We used Kaplan-Meier analysis to identify the correlations between genes and overall survival (OS) and progression-free survival (PFS). Univariate and multivariate cox regression analysis were employed to construct survival model. Cibersort was used to predict the immune cell composition of high and low risk group. Combined nomograms were built to predict PRCC prognosis. Immune properties of PRCC were validated by The Cancer Immunome Atlas (TCIA).

RESULTS

We found immune/stromal score was correlated with T pathological stages and PRCC subtypes. Nine hundred eighty-nine differentially expressed genes (DEGs) and 1169 DEGs were identified respectively on the basis of immune and stromal score. Venn diagrams indicated that 763 co-upregulated genes and 4 co-downregulated genes were identified. Kaplan-Meier analysis revealed that 120 genes were involved in tumor prognosis. Then PPI network analysis identified 22 hub genes, and four of which were significantly related to OS in patients with PRCC confirmed by cox regression analysis. Finally, we constructed a prognostic nomogram which combined with influence factors.

CONCLUSIONS

Four tumor microenvironment-related genes (CD79A, CXCL13, IL6 and CCL19) were identified as biomarkers for PRCC prognosis.

Single-agent activity of phosphatidylinositol 3-kinase inhibition with copanlisib in patients with molecularly defined relapsed or refractory diffuse large B-cell lymphoma

Patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL) have adverse outcomes. We evaluated the efficacy and safety of the phosphatidylinositol 3-kinase inhibitor copanlisib in patients with relapsed/refractory DLBCL and assessed the relationship between efficacy and DLBCL cell of origin (COO; activated B-cell like [ABC] and germinal center B-cell like [GCB]) and other biomarkers. The primary endpoint was objective response rate (ORR) in DLBCL COO subgroups (ABC, GCB, and unclassifiable) and by CD79B mutational status (NCT02391116). Sixty-seven patients received copanlisib (ABC DLBCL, n = 19; GCB DLBCL, n = 30; unclassifiable, n = 3; missing, n = 15). The ORR was 19.4%; 31.6% and 13.3% in ABC and GCB DLBCL patients, respectively. ORR was 22.2%/20.0% for patients with/without CD79B mutations (wild type, n = 45; mutant, n = 9; missing, n = 13). Overall median progression-free survival and duration of response were 1.8 and 4.3 months, respectively. Adverse events included hypertension (40.3%), diarrhea (37.3%), and hyperglycemia (32.8%). Aberrations were detected in 338 genes, including BCL2 (53.7%) and MLL2 (53.7%). A 16-gene signature separating responders from nonresponders was identified. Copanlisib treatment demonstrated a manageable safety profile in patients with relapsed/refractory DLBCL and a numerically higher response rate in ABC vs. GCB DLBCL patients.

Regulation of B cell receptor-dependent NF-κB signaling by the tumor suppressor KLHL14

The KLHL14 gene acquires frequent inactivating mutations in mature B cell malignancies, especially in the MYD88L265P, CD79B mutant (MCD) genetic subtype of diffuse large B cell lymphoma (DLBCL), which relies on B cell receptor (BCR) signaling for survival. However, the pathogenic role of KLHL14 in DLBCL and its molecular function are largely unknown. Here, we report that KLHL14 is in close proximity to the BCR in the endoplasmic reticulum of MCD cell line models and promotes the turnover of immature glycoforms of BCR subunits, reducing total cellular BCR levels. Loss of KLHL14 confers relative resistance to the Bruton tyrosine kinase (BTK) inhibitor ibrutinib and promotes assembly of the MYD88-TLR9-BCR (My-T-BCR) supercomplex, which initiates prosurvival NF-κB activation. Consequently, KLHL14 inactivation allows MCD cells to maintain NF-κB signaling in the presence of ibrutinib. These findings reinforce the central role of My-T-BCR-dependent NF-κB signaling in MCD DLBCL and suggest that the genetic status of KLHL14 should be considered in clinical trials testing inhibitors of BTK and BCR signaling mediators in DLBCL.

Integrated transcriptomic correlation network analysis identifies COPD molecular determinants

Chronic obstructive pulmonary disease (COPD) is a complex and heterogeneous syndrome. Network-based analysis implemented by SWIM software can be exploited to identify key molecular switches - called "switch genes" - for the disease. Genes contributing to common biological processes or defining given cell types are usually co-regulated and co-expressed, forming expression network modules. Consistently, we found that the COPD correlation network built by SWIM consists of three well-characterized modules: one populated by switch genes, all up-regulated in COPD cases and related to the regulation of immune response, inflammatory response, and hypoxia (like TIMP1, HIF1A, SYK, LY96, BLNK and PRDX4); one populated by well-recognized immune signature genes, all up-regulated in COPD cases; one where the GWAS genes AGER and CAVIN1 are the most representative module genes, both down-regulated in COPD cases. Interestingly, 70% of AGER negative interactors are switch genes including PRDX4, whose activation strongly correlates with the activation of known COPD GWAS interactors SERPINE2, CD79A, and POUF2AF1. These results suggest that SWIM analysis can identify key network modules related to complex diseases like COPD.

B cell receptor accessory molecule CD79 gets involved in response against Streptococcus agalactiae infection and BCR signaling in Nile tilapia (Oreochromis niloticus)

CD79, composed of two distinct chains called CD79a and CD79b, is a transmembrane protein that forms a B cell antigen receptor with membrane immunoglobulin, and generates a signal following antigen recognition by the B cell receptor. In this study, the CD79a (OnCD79a) and CD79b (OnCD79b) were cloned and identified from Nile tilapia (Oreochromis niloticus). The cDNA of ORF for OnCD79a and OnCD79b are 669 and 627 bp, coding 222 and 208 amino acids, respectively. The deduced protein analysis showed that both CD79a andCD79b contain an immunoreceptor tyrosine-based activation motif in their intracellular tails that used to propagate a signal in a B cell. Expression analysis revealed that both CD79a and CD79b expressed at high levels in immune tissues, such as anterior kidney and spleen, and in IgM⁺ B cells. Upon Streptococcus agalactiae (S. agalactiae) infection, the expressions of OnCD79a and OnCD79b were significantly up-regulated in anterior kidney and spleen. The significant up-regulations of OnCD79a and OnCD79b were also detected in leukocytes after in vitro challenge with S. agalactiae. Further, stimulations of LPS and anti-OnIgM monoclonal antibody induced significant up-regulations of OnCD79a and OnCD79b in leukocytes. Taken together, the results of this study indicated that CD79 molecule, playing roles in BCR signaling, was likely to get involved in host defense against bacterial infection in Nile tilapia.

Continuous signaling of CD79b and CD19 is required for the fitness of Burkitt lymphoma B cells

Expression of the B-cell antigen receptor (BCR) is essential not only for the development but also for the maintenance of mature B cells. Similarly, many B-cell lymphomas, including Burkitt lymphoma (BL), require continuous BCR signaling for their tumor growth. This growth is driven by immunoreceptor tyrosine-based activation motif (ITAM) and PI3 kinase (PI3K) signaling. Here, we employ CRISPR/Cas9 to delete BCR and B-cell co-receptor genes in the human BL cell line Ramos. We find that Ramos B cells require the expression of the BCR signaling component Igβ (CD79b), and the co-receptor CD19, for their fitness and competitive growth in culture. Furthermore, we show that in the absence of any other BCR component, Igβ can be expressed on the B-cell surface, where it is found in close proximity to CD19 and signals in an ITAM-dependent manner. These data suggest that Igβ and CD19 are part of an alternative B-cell signaling module that use continuous ITAM/PI3K signaling to promote the survival of B lymphoma and normal B cells.

Dynamic EBF1 occupancy directs sequential epigenetic and transcriptional events in B-cell programming

B-cell fate determination requires the action of transcription factors that operate in a regulatory network to activate B-lineage genes and repress lineage-inappropriate genes. However, the dynamics and hierarchy of events in B-cell programming remain obscure. To uncouple the dynamics of transcription factor expression from functional consequences, we generated induction systems in developmentally arrested Ebf1-/- pre-pro-B cells to allow precise experimental control of EBF1 expression in the genomic context of progenitor cells. Consistent with the described role of EBF1 as a pioneer transcription factor, we show in a time-resolved analysis that EBF1 occupancy coincides with EBF1 expression and precedes the formation of chromatin accessibility. We observed dynamic patterns of EBF1 target gene expression and sequential up-regulation of transcription factors that expand the regulatory network at the pro-B-cell stage. A continuous EBF1 function was found to be required for Cd79a promoter activity and for the maintenance of an accessible chromatin domain that is permissive for binding of other transcription factors. Notably, transient EBF1 occupancy was detected at lineage-inappropriate genes prior to their silencing in pro-B cells. Thus, persistent and transient functions of EBF1 allow for an ordered sequence of epigenetic and transcriptional events in B-cell programming.

Inhibition of B Cell Receptor Signaling by Ibrutinib in Primary CNS Lymphoma

Primary CNS lymphoma (PCNSL) harbors mutations that reinforce B cell receptor (BCR) signaling. Ibrutinib, a Bruton's tyrosine kinase (BTK) inhibitor, targets BCR signaling and is particularly active in lymphomas with mutations altering the BCR subunit CD79B and MYD88. We performed a proof-of-concept phase Ib study of ibrutinib monotherapy followed by ibrutinib plus chemotherapy (DA-TEDDi-R). In 18 PCNSL patients, 94% showed tumor reductions with ibrutinib alone, including patients having PCNSL with CD79B and/or MYD88 mutations, and 86% of evaluable patients achieved complete remission with DA-TEDDi-R. Increased aspergillosis was observed with ibrutinib monotherapy and DA-TEDDi-R. Aspergillosis was linked to BTK-dependent fungal immunity in a murine model. PCNSL is highly dependent on BCR signaling, and ibrutinib appears to enhance the efficacy of chemotherapy.

Mutational status of EZH2 and CD79B hot spots in mature B-cell non-Hodgkin's lymphomas: novel CD79B variations have been revealed

OBJECTIVE

We aimed to determine the hot spot mutational frequencies of Enhancer of Zeste homolog 2 (EZH2) and cluster of differentiation 79B (CD79B) genes in a cohort of mature B-cell non-Hodgkin's lymphomas.

PATIENTS AND METHODS

DNA samples from formalin-fixed and paraffin embedded (FFPE) tissues from a total of 37 patients with mature B-cell non-Hodgkin lymphomas were included in the study. Molecular genetic analysis was performed by direct sequencing of the DNA samples.

RESULTS

We analyzed formaldehyde fixed-paraffin embedded (FFPE) tumor tissue samples from 17 female and 20 male patients with a median age of 63.7 years at the time of diagnosis. None of the patients had previously reported hot spot mutations in EZH2 and CD79B, but previously unreported single nucleotide variations of CD79B were present in nine patients. rs779833118 was the most frequent variation (7/37 patients, 18.9%). A non-synonymous variation rs757407417, which could have a potentially damaging outcome, was detected in two patients.

CONCLUSIONS

None of the patients had well-known hot spot mutations in EZH2 and CD79B. However, we detected novel CD79B variations in mature B-cell non-Hodgkin's lymphoma patients.

Down-regulation of B cell-related genes in peripheral blood leukocytes of Parkinson's disease patients with and without GBA mutations

Parkinson's disease (PD) is a common neurodegenerative disorder, caused by aging, genetic and environmental factors. Many genes and genetic loci have been implicated in autosomal dominant and recessive PD, among them SNCA, LRRK2, GBA, Parkin, DJ1 and PINK1. Mutations in the LRRK2 and GBA genes are especially common among PD patients of Ashkenazi-Jewish (AJ) origin, accounting for over a third of the patient population. We aimed to identify genes and cellular pathways that may be involved in GBA-associated PD. Whole genome expression analysis was performed using peripheral blood leukocytes (PBLs) of PD patients with mutations in the GBA gene (PD-GBA, n = 59) compared to healthy controls (n = 59). Significant expression changes were detected in 26 genes, most of them were down-regulated in patients and annotated to B cell or immune-related functions. The expression levels of five membrane-bound B cell genes (FCRL1, CD19, CD22, CD79A and CD180) were further analyzed in four distinct populations: (1) Healthy controls (n = 20), (2) PD-GBA (n = 20), (3) PD patients who do not carry LRRK2 or GBA mutations (PD-NC, n = 20), (4) Asymptomatic 1st degree family members, with (n = 15) or without (n = 15) GBA mutations. In qRT-PCR analysis, all five genes were down-regulated in patients (PD-GBA and PD-NC) compared to controls. These changes in expression were not observed when comparing family members who carry GBA mutations to non-carrier family members. Furthermore, these expression levels were disease-duration dependent: the most significant decreased expression occurred after the first two years of onset, and remained steady after 6 years. These results further support the involvement of B cell-related genes in PD and correlate the level of reduced expression to disease duration.

Conditional Expression of E2A-HLF Induces B-Cell Precursor Death and Myeloproliferative-Like Disease in Knock-In Mice

Chromosomal translocations are driver mutations of human cancers, particularly leukemias. They define disease subtypes and are used as prognostic markers, for minimal residual disease monitoring and therapeutic targets. Due to their low incidence, several translocations and their biological consequences remain poorly characterized. To address this, we engineered mouse strains that conditionally express E2A-HLF, a fusion oncogene from the translocation t(17;19) associated with 1% of pediatric B-cell precursor ALL. Conditional oncogene activation and expression were directed to the B-cell compartment by the Cre driver promoters CD19 or Mb1 (Igα, CD79a), or to the hematopoietic stem cell compartment by the Mx1 promoter. E2A-HLF expression in B-cell progenitors induced hyposplenia and lymphopenia, whereas expression in hematopoietic stem/progenitor cells was embryonic lethal. Increased cell death was detected in E2A-HLF expressing cells, suggesting the need for cooperating genetic events that suppress cell death for B-cell oncogenic transformation. E2A-HLF/Mb1.Cre aged mice developed a fatal myeloproliferative-like disorder with low frequency characterized by leukocytosis, anemia, hepatosplenomegaly and organ-infiltration by mature myelocytes. In conclusion, we have developed conditional E2A-HLF knock-in mice, which provide an experimental platform to study cooperating genetic events and further elucidate translational biology in cross-species comparative studies.

Anti-CD22 and anti-CD79B antibody drug conjugates are active in different molecular diffuse large B-cell lymphoma subtypes

Antibody drug conjugates (ADCs), in which cytotoxic drugs are linked to antibodies targeting antigens on tumor cells, represent promising novel agents for the treatment of malignant lymphomas. Pinatuzumab vedotin is an anti-CD22 ADC and polatuzumab vedotin an anti-CD79B ADC that are both linked to the microtubule-disrupting agent monomethyl auristatin E (MMAE). In the present study, we analyzed the activity of these agents in different molecular subtypes of diffuse large B-cell lymphoma (DLBCL) both in vitro and in early clinical trials. Both anti-CD22-MMAE and anti-CD79B-MMAE were highly active and induced cell death in the vast majority of activated B-cell-like (ABC) and germinal center B-cell-like (GCB) DLBCL cell lines. Similarly, both agents induced cytotoxicity in models with and without mutations in the signaling molecule CD79B. In line with these observations, relapsed and refractory DLBCL patients of both subtypes responded to these agents. Importantly, a strong correlation between CD22 and CD79B expression in vitro and in vivo was not detectable, indicating that patients should not be excluded from anti-CD22-MMAE or anti-CD79B-MMAE treatment because of low target expression. In summary, these studies suggest that pinatuzumab vedotin and polatuzumab vedotin are active agents for the treatment of patients with different subtypes of DLBCL.

Isoforms of the CD79 signal transduction component of the macropod B-cell receptor

B cell responses and their concomitant signal transduction pathways are not well understood in marsupial mammals, despite the availability of gene expression data for key immunoglobulin genes and for elements of the CD79a/CD79b heterodimer signalling complex for two model marsupials. Broader studies of factors that influence B cell responses are still hampered by a lack of species-specific reagents and there are few reports of other factors that influence gene expression such as the potential for splice variants in BCR components, which may influence immune signalling pathways. In this study, we characterise CD79a and CD79b genes in the endangered macropod marsupial, Onychogalea fraenata (the bridled nailtail wallaby) and show that domains and residues important for the structural and functional integrity of both monomers are conserved in this species, consistent with results previously reported for the closely-related macropod, Macropus eugenii (the tammar wallaby). We extend this work to report the detection of splice variants for CD79a and CD79b in wallaby species; three CD79a isoforms and one CD79b isoform. Of these, two CD79a isoforms and the CD79b isoform have not been reported in any other mammalian species.

IgG1 cytoplasmic tail is essential for cell surface expression in Igβ down-regulated cells

It has been shown that cytoplasmic tail of the IgG1 B cell receptors (BCRs) are essential for the induction of T-dependent immune responses. Also it has been revealed that unique tyrosine residue in the cytoplasmic tail of IgG2a has the potential of being phosphorylated at tyrosine and that this phosphorylation modulates BCR signaling. However, it still remains unclear whether such phosphorylation of IgG cytoplasmic tail is involved in the regulation of BCR surface expression. In order to approach the issue, we established and analyzed the cell lines which express wild-type or mutated forms of IgG1 BCR. As the result, we found that IgG1 BCR expressed normally on the surface of A20 B cell line independent of the cytoplasmic tail. In contrast, IgG1 BCR whose cytoplasmic tyrosine was replaced with glutamic acid which mimics phosphorylated tyrosine, was expressed most efficiently on the surface of non-B lineage cells and Igβ-down-regulated B cell lines. These results suggest that tyrosine residue in IgG cytoplasmic tail is playing a essential role for the efficient expression of IgG BCR on the cell surface when BCR associated signaling molecules, including Igβ, are down-regulated.

B-cell receptor signaling as a driver of lymphoma development and evolution

The B-cell receptor (BCR) is essential for normal B-cell development and maturation. In an increasing number of B-cell malignancies, BCR signaling is implicated as a pivotal pathway in tumorigenesis. Mechanisms of BCR activation are quite diverse and range from chronic antigenic drive by microbial or viral antigens to autostimulation of B-cells by self-antigens to activating mutations in intracellular components of the BCR pathway. Hepatitis C virus infection can lead to the development of splenic marginal zone lymphoma, while Helicobacter pylori infection is associated with the development of mucosa-associated lymphoid tissue lymphomas. In some of these cases, successful treatment of the infection removes the inciting antigen and results in resolution of the lymphoma. Chronic lymphocytic leukemia has been recognized for decades as a malignancy of auto-reactive B-cells and its clinical course is in part determined by the differential response of the malignant cells to BCR activation. In a number of B-cell malignancies, activating mutations in signal transduction components of the BCR pathway have been identified; prominent examples are activated B-cell-like (ABC) diffuse large B-cell lymphomas (DLBCL) that carry mutations in CD79B and CARD11 and display chronic active BCR signaling resulting in constitutive activation of the NF-κB pathway. Despite considerable heterogeneity in biology and clinical course, many mature B-cell malignancies are highly sensitive to kinase inhibitors that disrupt BCR signaling. Thus, targeted therapy through inhibition of BCR signaling is emerging as a new treatment paradigm for many B-cell malignancies. Here, we review the role of the BCR in the pathogenesis of B-cell malignancies and summarize clinical results of the emerging class of kinase inhibitors that target this pathway.

Genome wide SNP array identified multiple mechanisms of genetic changes in Waldenstrom macroglobulinemia

SNP array (SNPa) was developed to detect copy number alteration (CNA) and loss of heterozygosity (LOH) without copy number changes, CN-LOH. We aimed to identify novel genomic aberrations using SNPa in 31 WM with paired samples. Methylation status and mutation were analyzed on target genes. A total of 61 genetic aberrations were observed, 58 CNA (33 gains, 25 losses) in 58% of patients and CN-LOH in 6% of patients. The CNA were widely distributed throughout the genome, including 12 recurrent regions and identified new cryptic clonal chromosomal lesions that were mapped. Gene set expression analysis demonstrated a relationship between either deletion 6q or gain of chromosome 4 and alteration of gene expression profiling. We then studied methylation status and sought for mutations in altered regions on target genes. We observed methylation of DLEU7 on chromosome 13 in all patients (n = 12) with WM, and mutations of CD79B/CD79A genes (17q region), a key component of the BCR pathway, in 15% of cases. Most importantly, higher frequency of ≥3 CNA was observed in symptomatic WM. In conclusion, this study expands the view of the genomic complexity of WM, especially in symptomatic WM, including a potentially new mechanism of gene dysfunction, acquired uniparental disomy/CN-LOH. Finally, we have identified new potential target genes in WM, such as DLEU7 and CD79A/B.

B cell receptor accessory molecule CD79α: characterisation and expression analysis in a cartilaginous fish, the spiny dogfish (Squalus acanthias)

CD79α (also known as Igα) is a component of the B cell antigen receptor complex and plays an important role in B cell signalling. The CD79α protein is present on the surface of B cells throughout their life cycle, and is absent on all other healthy cells, making it a highly reliable marker for B cells in mammals. In this study the spiny dogfish (Squalus acanthias) CD79α (SaCD79α) is described and its expression studied under constitutive and stimulated conditions. The spiny dogfish CD79α cDNA contains an open reading frame of 618 bp, encoding a protein of 205 amino acids. Comparison of the SaCD79α gene with that of other species shows that the gross structure (number of exons, exon/intron boundaries, etc.) is highly conserved across phylogeny. Additionally, analysis of the 5' flanking region shows SaCD79α lacks a TATA box and possesses binding sites for multiple transcription factors implicated in its B cell-specific gene transcription in other species. Spiny dogfish CD79α is most highly expressed in immune tissues, such as spleen, epigonal and Leydig organ, and its transcript level significantly correlates with those of spiny dogfish immunoglobulin heavy chains. Additionally, CD79α transcription is up-regulated, to a small but significant degree, in peripheral blood cells following stimulation with pokeweed mitogen. These results strongly indicate that, as in mammals, spiny dogfish CD79α is expressed by shark B cells where it associates with surface-bound immunoglobulin to form a fully functional BCR, and thus may serve as a pan-B cell marker in future shark immunological studies.

Postnatal leptin promotes organ maturation and development in IUGR piglets

Babies with intra-uterine growth restriction (IUGR) are at increased risk for experiencing negative neonatal outcomes due to their general developmental delay. The present study aimed to investigate the effects of a short postnatal leptin supply on the growth, structure, and functionality of several organs at weaning. IUGR piglets were injected from day 0 to day 5 with either 0.5 mg/kg/d leptin (IUGRLep) or saline (IUGRSal) and euthanized at day 21. Their organs were collected, weighed, and sampled for histological, biochemical, and immunohistochemical analyses. Leptin induced an increase in body weight and the relative weights of the liver, spleen, pancreas, kidneys, and small intestine without any changes in triglycerides, glucose and cholesterol levels. Notable structural and functional changes occurred in the ovaries, pancreas, and secondary lymphoid organs. The ovaries of IUGRLep piglets contained less oogonia but more oocytes enclosed in primordial and growing follicles than the ovaries of IUGRSal piglets, and FOXO3A staining grade was higher in the germ cells of IUGRLep piglets. Within the exocrine parenchyma of the pancreas, IUGRLep piglets presented a high rate of apoptotic cells associated with a higher trypsin activity. In the spleen and the Peyer's patches, B lymphocyte follicles were much larger in IUGRLep piglets than in IUGRSal piglets. Moreover, IUGRLep piglets showed numerous CD79(+) cells in well-differentiated follicle structures, suggesting a more mature immune system. This study highlights a new role for leptin in general developmental processes and may provide new insight into IUGR pathology.

Local immune response in bladder pain syndrome/interstitial cystitis ESSIC type 3C

INTRODUCTION AND HYPOTHESIS

Bladder pain syndrome/interstitial cystitis (BPS/IC) is identified based on subjective symptoms which lead to heterogeneous patient populations. Previous studies using gene expression arrays for BPS/IC with Hunner's lesions [European Society for the Study of Interstitial Cystitis (ESSIC) type 3C], a subtype of the condition discernible by cystoscopy, have revealed characteristic immune responses and urothelial abnormalities. This current study aimed to further characterize this subtype using a gene expression panel. We hypothesized that B-cell activation with high levels of urinary antibody concentration would be found.

METHODS

Cold-cup bladder biopsies, catheterized urine and blood were collected from 15 BPS/IC ESSIC type 3C patients, 11 non-inflammatory overactive bladder (OAB) patients and eight healthy controls. Gene expression in biopsies was quantified by real-time quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry was performed on bladder tissue and urinary immunoglobulins G and A were quantified by enzyme-linked immunosorbent assay. Statistical analyses included the Kruskal-Wallis test for non-parametric data and post hoc tests identified differences between groups.

RESULTS

High expression of T- and B-cell markers (CTLA4, CD20, CD79A, IGH@), low expression of urothelial markers (KRT20, UPK1B, UPK3A), focal lymphoid aggregates in the submucosa and high immunoglobulin concentration in urine were found exclusively in BPS/IC ESSIC type 3C patients. Results for OAB were in intermediate ranges between the other two groups and UPK1B even reached significantly lower expression when compared to healthy controls.

CONCLUSIONS

BPS/IC ESSIC type 3C is characterized by a local adaptive immune response with elevated urinary antibody concentrations. Quantification of urinary immunoglobulin levels could be used for a non-invasive diagnosis of BPS/IC ESSIC type 3C.

Resident lymphocytes in the epidermis and adnexal epithelia of normal dorsolateral thorax of alpacas

A small population of resident T-lymphocytes is present in the normal epidermis of skin from humans, mice, sheep, and cattle. The objective of this study was to determine the prevalence of lymphocytes, CD3+ cells (T-lymphocytes) and CD79a+ cells (B-lymphocytes and plasma cells), in the epidermis and adnexal epithelia of alpacas. Skin-biopsy specimens from the normal skin of the dorsolateral thorax of 31 alpacas were examined histologically and immunohistochemically for the presence of CD3+ cells and CD79a+ cells in the epidermis and adnexal epithelia. CD3+ T-lymphocytes, but not CD79a+ cells, were present in the epidermis and adnexal epithelia. Therefore, in the absence of other signs of inflammation, the presence of lymphocytes in these structures in skin-biopsy specimens should be considered normal.

VR09 cell line: an EBV-positive lymphoblastoid cell line with in vivo characteristics of diffuse large B cell lymphoma of activated B-cell type

BACKGROUND

small B-cell neoplasms can show plasmacytic differentiation and may potentially progress to aggressive lymphoma (DLBCL). Epstein-Barr virus (EBV) infection may cause the transformation of malignant cells in vitro.

DESIGN AND METHOD

we established VR09 cell line with plasmacytic differentiation, obtained from a case of atypical, non-CLL B-cell chronic lymphoproliferative disease with plasmacytic features. We used flow cytometry, immunohistochemistry, polymerase chain reaction, cytogenetic analysis and florescence in situ hybridization in the attempt at thoroughly characterizing the cell line. We showed VR09 tumorigenic potential in vivo, leading to the development of activated DLBCL with plasmacytic features.

RESULTS

VR09 cells displayed plasmacytic appearance and grew as spherical tumors when inoculated subcutaneously into immunodeficient Rag2(-/-) γ-chain(-/-) mice. VR09 cell line and tumors displayed the phenotype of activated stage of B cell maturation, with secretory differentiation (CD19+ CD20+ CD79a+ CD79b+/- CD138+ cyclin D1- Ki67 80% IgM+ IgD+ MUM1+ MNDA+ CD10- CD22+ CD23+ CD43+ K+, λ- Bcl2+ Bcl6-) and they presented episomal EBV genome, chromosome 12 trisomy, lack of c-MYC rearrangement and Myd88 gene mutation, presence of somatic hypermutation in the VH region, and wild-type p53.

CONCLUSION

This new EBV-positive cell line may be useful to further characterize in vivo activated DLBCL with plasmacytic features.

Early postnatal B cell ontogeny and antibody repertoire maturation in the opossum, Monodelphis domestica

Marsupials are a lineage of mammals noted for giving birth to highly altricial young, which complete much of their “fetal” development externally attached to a teat. Postnatal B cell ontogeny and diversity was investigated in a model marsupial species, the gray short-tailed opossum, Monodelphis domestica. The results support the initiation of B cell development late in gestation and progressing into the first two weeks of postnatal life. Transcription of CD79a and CD79b was detected in embryonic tissue prior to birth, while immunoglobulin heavy chain locus transcription was not detected until the first postnatal 24 hours. Transcription of the Ig light chains was not detected until postnatal day 7 at the earliest. The predicted timing of the earliest appearance of mature B cells and completion of gene rearrangements is consistent with previous analyses on the timing of endogenous antibody responses in newborn marsupials. The diversity of early B cell IgH chains is limited, as has been seen in fetal humans and mice, but lacks bias in the gene segments used to encode the variable domains. Newborn light chain diversity is, from the start, comparable to that of the adult, consistent with an earlier hypothesis that light chains contribute extensively to antibody diversity in this species.

Mutation analysis of NF-κB signal pathway-related genes in ocular MALT lymphoma

Constitutive nuclear factor-kappa B (NF-κB) activation has been reported in ocular adnexal lymphoma (OAL). TNFAIP3/A20 is a "global" inhibitor of NF-κB pathway. We have shown that OAL has preferential loss of the 6q23.3 region where TNFAIP3/A20 exist, which is suggested to involve in lymphomagenesis of OAL. The mechanisms causing NF-κB activity in OAL remain elusive. Recently, NF-κB canonical pathway genes including CARD11, CD79B and MYD88 were shown to be frequently mutated in diffuse large B-cell lymphomas. In this study, we analyzed the mutation status of these genes by direct sequencing in 24 OAL cases including 9 cases with loss of 6q23.3 previously identified by array comparative genomic hybridization. We showed that genetic alterations of these genes were not found in OAL, a finding differing from that of most B-cell lymphomas. Genetic or epigenetic alterations in other genes are likely to be relevant in pathogenesis of OAL case without A20 loss.

Syk is a dual-specificity kinase that self-regulates the signal output from the B-cell antigen receptor

Upon B-cell activation, the signaling subunits Ig-α and Ig-β of the B-cell antigen receptor become phosphorylated not only on tyrosines but also on serine residues. Using a specific antibody, we show that serine 197 (S197) in the cytoplasmic tail of Ig-α is phosphorylated upon B-cell antigen receptor activation, and that this modification inhibits the signal output of the B-cell antigen receptor. Surprisingly, we found that the well-known protein tyrosine kinase Syk (spleen tyrosine kinase) phosphorylates S197 on Ig-α, thus not only activating but also inhibiting signaling from the B-cell antigen receptor. This finding identifies Syk as a dual-specificity kinase and establishes a previously unexplored paradigm for the self-regulation of biological signaling processes.

B cell receptor accessory molecules in the channel catfish, Ictalurus punctatus

B cell receptor (BCR) accessory molecules CD79a and CD79b homologs were identified in the channel catfish, Ictalurus punctatus. Both are found as single copy genes that encode proteins containing a signal peptide, an extracellular immunoglobulin domain, a transmembrane region and a cytoplasmic tail containing an immune-receptor tyrosine-dased activation motif (ITAM). IpCD79a and IpCD79b transcripts correlate well with IgM message expression. They are highly expressed in peripheral blood leukocytes (PBL) enriched in membrane (m) IgM+ cells and catfish clonal B cell lines, but not in catfish clonal T cells, indicating that IpCD79a and IpCD79b expression is B cell restricted. Studies using catfish clonal B cells (3B11) transfected with constructs encoding epitope-tagged IpCD79a and IpCD79b revealed that IpCD79a was expressed as a 45 kDa protein and IpCD79b was expressed as a 32 kDa protein. Furthermore, co-immunoprecipitations of epitope-tagged CD79 proteins demonstrate that these molecules are non-covalently associated with mIgM. These data correlate with some of the previous immunoprecipitation data demonstrating that catfish mIgM associates with proteins of 45 and 32 kDa.

MHC class II structural requirements for the association with Igalpha/beta, and signaling of calcium mobilization and cell death

Emerging evidence indicates that in addition to their well-characterized role in antigen presentation, MHC II molecules transmit signals that induce death of APCs. Appropriately timed APC death is important for prevention of autoimmunity. Though the exact mechanism of MHC II-mediated cell death signaling is unknown, the response appears independent of caspase activation and does not involve Fas-FasL interaction. Here we investigated MHC II structural requirements for mediation of cell death signaling in a murine B cell lymphoma. We found that neither the transmembrane spanning regions nor the cytoplasmic tails of MHC II, which are required for MHC II-mediated cAMP production and PKC activation, are required for the death response. However, mutations in the connecting peptide region of MHC II alpha chain (alphaCP), but not the beta chain (betaCP), resulted in significant impairment of the death response. The alphaCP mutant was also unable to mediate calcium mobilization responses, and did not associate with Igalpha/beta. Knock-down of Igbeta by shRNA eliminated the MHC II-mediated calcium response but not cell death. We propose that MHC II mediates cell death signaling via association with an undefined cell surface protein(s), whose interaction is partially dependent on alphaCP region.

Cutting edge: a hypomorphic mutation in Igbeta (CD79b) in a patient with immunodeficiency and a leaky defect in B cell development

Although null mutations in Igalpha have been identified in patients with defects in B cell development, no mutations in Igbeta have been reported. We recently identified a patient with a homozygous amino acid substitution in Igbeta, a glycine to serine at codon 137, adjacent to the cysteine required for the disulfide bond between Igalpha and Igbeta. This patient has a small percentage of surface IgM(dim) B cells in the peripheral circulation (0.08% compared with 5-20% in healthy controls). Using expression vectors in 293T cells or Jurkat T cells, we show that the mutant Igbeta can form disulfide-linked complexes and bring the mu H chain to the cell surface as part of the BCR but is inefficient at both tasks. The results show that minor changes in the ability of the Igalpha/Igbeta complex to bring the BCR to the cell surface have profound effects on B cell development.

Mutations of the Igbeta gene cause agammaglobulinemia in man

Agammaglobulinemia is a rare primary immunodeficiency characterized by an early block of B cell development in the bone marrow, resulting in the absence of peripheral B cells and low/absent immunoglobulin serum levels. So far, mutations in Btk, mu heavy chain, surrogate light chain, Igalpha, and B cell linker have been found in 85-90% of patients with agammaglobulinemia. We report on the first patient with agammaglobulinemia caused by a homozygous nonsense mutation in Igbeta, which is a transmembrane protein that associates with Igalpha as part of the preBCR complex. Transfection experiments using Drosophila melanogaster S2 Schneider cells showed that the mutant Igbeta is no longer able to associate with Igalpha, and that assembly of the BCR complex on the cell surface is abrogated. The essential role of Igbeta for human B cell development was further demonstrated by immunofluorescence analysis of the patient's bone marrow, which showed a complete block of B cell development at the pro-B to preB transition. These results indicate that mutations in Igbeta can cause agammaglobulinemia in man.

Igbeta(CD79b) mRNA expression in chronic lymphocytic leukaemia cells correlates with immunoglobulin heavy chain gene mutational status but does not serve as an independent predictor of clinical severity

The etiology of chronic lymphocytic leukemia (CLL) is poorly understood and its course is highly variable. Somatic hypermutation (SHM) of the immunoglobulin heavy chain (IgV(H)) gene and ZAP70 protein expression have been reported as prognostic indicators. However, these assays are not widely available and their concordance is imperfect. Thus a need exists to identify additional molecular determinants of CLL. The Igbeta (CD79b) subunit of the B cell antigen receptor is essential for B lymphocyte function. Defects in Igbeta expression are implicated in CLL pathogenesis. We have analyzed Igbeta mRNA expression in CLL cells in 40 consecutive patient samples. About 75% of the samples showed the expected decrease of Igbeta surface staining. Igbeta mRNA levels covered a wider range, did not correlate with Igbeta surface staining, but clearly distinguished the normal and CLL lymphocyte populations. Remarkably, Igbeta mRNA levels correlated strongly with SHM; Igbeta mRNA levels in CLL cells were significantly higher in patients with an unmutated IgV(H) gene when compared with those in whom IgV(H) was hypermutated (P = 0.008). In contrast, no correlation was observed between Igbeta mRNA levels and ZAP70 expression. Multiple parameters abstracted from chart reviews were used to estimate severity of CLL in each case. While severity correlated strongly with ZAP70 staining, and to a lesser extent with SHM status, there was no correlation with Igbeta mRNA levels. These data establish a strong linkage between Igbeta mRNA expression and SHM in CLL and highlight the complex relationships between biochemical parameters and clinical status in this disease.

Role of the extracellular and transmembrane domain of Ig-alpha/beta in assembly of the B cell antigen receptor (BCR)

The B cell antigen receptor (BCR) is expressed on the surface of B-lymphocytes where it binds antigen and transmits signals that regulate B cell activation, growth and differentiation. The BCR is composed of membrane IgM (mIgM) and two signaling proteins, Ig-alpha and Ig-beta. If either of the signaling proteins is not expressed, the incomplete mIgM-containing BCR will not traffic to the cell surface. Our hypothesis is that specific protein:protein interactions between both the extracellular and transmembrane (TM) regions of Ig-alpha and Ig-beta are necessary for receptor assembly, cell surface expression and effective signaling to support the proper development of B cells. While previous work has shown the importance of the TM region in BCR assembly, this study indicates that a heterodimer of the extracellular domains of Ig-alpha and Ig-beta are also required for proper association with mIgM. Cell lines expressing mutated Ig-alpha proteins that did not heterodimerize with Ig-beta in the extracellular and TM domains were unable to properly assemble the BCR. Conversely, an Ig-alpha mutant with an Ig-beta cytoplasmic tail (Cbeta (alpha/alpha/beta)) was able to assemble with the rest of the BCR, in particular with Ig-beta, and traffic to the cell surface. Thus, both the extracellular and TM regions of the Ig-alpha/Ig-beta must be properly associated in order for the BCR to assemble.

Development-dependent expression of cyclin D3 in precursor T-cell lymphoblastic leukemia/lymphoma

In contrast to the clear oncogenic role of cyclins D1 and D2, cyclin D3 is suggested to have a role in the initiation and/or maintenance of differentiation in a lineage-associated manner in addition to its basic role in proliferation. Recently, it has been reported that in cyclin D3-deficient mice, normal expansion of T lymphocytes is impaired because of maturation arrest at the double-negative thymocyte stage, suggesting a crucial role for cyclin D3 in early T-cell development. Therefore, cyclin D3 expression was examined in 36 human precursor T-lymphoblastic leukemia/lymphomas (T-LBLL), a neoplastic counterpart of T cells at the early developmental stages of differentiation. Using a standard panel of differentiation markers, all T-LBLL were categorized into four stages according to differentiation: progenitor, double-negative, double-positive, and single-positive stages. Cyclin D3 expression was initiated at the boundary between double-negative and double-positive stages, and was sustained in the single-positive stage. T-cell receptor was expressed simultaneously with cyclin D3, whereas CD79a expression was specific in the double-negative stage, and thus it was inversely correlated with that of cyclin D3. Taken together with the crucial and non-redundant role in T-cell development in mice, this molecule is suggested to play an important role in human T-cell development.

The transcription factor GABP is a critical regulator of B lymphocyte development

GA binding protein (GABP) is a ubiquitously expressed Ets-family transcription factor that critically regulates the expression of the interleukin-7 receptor alpha chain (IL-7Ralpha) in T cells, whereas it is dispensable for IL-7Ralpha expression in fetal liver B cells. Here we showed that deficiency of GABPalpha, the DNA-binding subunit of GABP, resulted in profoundly defective B cell development and a compromised humoral immune response, in addition to thymic developmental defects. Furthermore, the expression of Pax5 and Pax5 target genes such as Cd79a was greatly diminished in GABPalpha-deficient B cell progenitors, pro-B, and mature B cells. GABP could bind to the regulatory regions of Pax5 and Cd79a in vivo. Thus, GABP is a key regulator of B cell development, maturation, and function.

The Ig-alpha ITAM is required for efficient differentiation but not proliferation of pre-B cells

Signals from the pre-B cell receptor (pre-BCR) mediated by the cytoplasmic tails of Ig-alpha/Ig-beta are essential for developing B cells. To analyze the role of Ig-alpha ITAM and non-ITAM tyrosines in pre-BCR signaling, we reconstituted individual tyrosine mutants of Ig-alpha in src homology 2 domain-containing leukocyte protein of 65 kDa (SLP-65)/Ig-alpha double-deficient pre-B cells. We show that the Ig-alpha mutants led to comparable pre-BCR expression on the cell surface, while the pre-BCR-induced tyrosine phosphorylation was different. We further show that the reconstitution of Ig-alpha and the resulting pre-BCR expression led to enrichment of the pre-BCR-expressing cells in vitro irrespective of the introduced Ig-alpha mutation. We show that, even though the enrichment rate increased by lowering the IL-7 concentration, residual amounts of IL-7 were required for optimal enrichment. Our results indicate that surface IL-7 receptor expression is modulated by the pre-BCR, thereby increasing the IL-7 sensitivity of the respective cells. In contrast to the comparable pre-B cell proliferation, however, the Ig-alpha mutants differed in their capacity to induce calcium flux and activate efficient pre-B cell differentiation. Together, our data suggest that ITAM tyrosines and Y204 are required for efficient pre-B cell differentiation but not proliferation.

Follicular lymphoma frequently originates in the salivary gland

The aim of the present study was to examine the clinicopathological presentations of follicular lymphomas (FL) of the salivary glands, as compared to mucosa-associated lymphoid tissue (MALT) lymphomas. A total of 27 primary salivary gland lymphomas were examined: 6 FL (five, grade 1; one, grade 2); 19 MALT lymphomas; and two diffuse large B-cell lymphomas. The FL patients ranged in age from 24 to 73 years, with a mean of 49 years, which was younger than that of MALT patients (mean: 64 years; P < 0.05). Four of the six FL arose from the submandibular gland, which was the origin of only five out of a total of 19 MALT lymphomas. One FL patient was in clinical stage (CS) IE, two in CS IIE, and two in CS III and IV. As regards the MALT lymphoma patients, 13 (68%) were in CS IE and five (26%) in CS IIE. None of the FL patients had clinical diagnosis of autoimmune disease but eight MALT lymphoma patients had autoimmune disease. The present study found a relatively high incidence of FL in the salivary glands. The observed differences in age of onset, background of autoimmune disease, and lesion site suggests that the pathogenesis of FL may differ from that of MALT lymphoma.

Genomic suppression of murine B29/Ig-β promoter-driven transgenes

Immunoglobulin beta (Ig-beta) is a critical signal transducer of precursor B cell and B cell receptors. B29, the gene coding for Ig-beta, is switched on in progenitor B cells and expressed until the terminal stage of antibody-producing plasma cells. Although several cis-acting elements and transcription factors required for B29 expression have been characterized in cell lines, the in vivo significance of individual motifs located in the 1.2-kb promoter region remained unclear. To address whether this region drives B lineage-specific expression in mice as efficiently as in transfected cell lines, we established transgenic animals carrying the B29 promoter fused to either enhanced green fluorescent protein (EGFP) or the precursor B cell receptor component lambda5. Surprisingly, only minimal levels of B29-derived transcripts were produced in B lymphoid tissues of several independent transgenic lines, and the respective proteins were below the detection limit. In addition, transgenic transcripts were found in testis, kidney and brain. Hence, the 1.2-kb-sized B29 promoter does not define a strong, B lineage-restricted expression unit when randomly integrated into the genome and passed through the murine germ line. Therefore, yet unidentified genomic locus control elements are required to efficiently drive B29 expression in B lymphocytes.

Locus control region transcription plays an active role in long-range gene activation

Activation of eukaryotic genes often relies on remote chromatin determinants. How these determinants function remains poorly understood. The hGH gene is activated by a 5'-remote locus control region (LCR). Pituitary-specific DNase I hypersensitive site I (HSI), the dominant hGH LCR element, is separated from the hGH-N promoter by a 14.5 kb span that encompasses the B-lymphocyte-specific CD79b gene. Here, we describe a domain of noncoding Pol II transcription in pituitary somatotropes that includes the hGH LCR and adjacent CD79b locus. This entire "LCR domain of transcription" is HSI [corrected] dependent and terminates 3' to CD79b, leaving a gap in transcription between this domain and the target hGH-N promoter. Insertion of a Pol II terminator within the LCR blocks CD79b transcription and represses hGH-N expression. These data document an essential role for LCR transcription in long-range control, link "bystander"CD79b transcription to this process, and support a unique model for locus activation.

Tissue-specific chromatin modifications at a multigene locus generate asymmetric transcriptional interactions

Random assortment within mammalian genomes juxtaposes genes with distinct expression profiles. This organization, along with the prevalence of long-range regulatory controls, generates a potential for aberrant transcriptional interactions. The human CD79b/GH locus contains six tightly linked genes with three mutually exclusive tissue specificities and interdigitated control elements. One consequence of this compact organization is that the pituitary cell-specific transcriptional events that activate hGH-N also trigger ectopic activation of CD79b. However, the B-cell-specific events that activate CD79b do not trigger reciprocal activation of hGH-N. Here we utilized DNase I hypersensitive site mapping, chromatin immunoprecipitation, and transgenic models to explore the basis for this asymmetric relationship. The results reveal tissue-specific patterns of chromatin structures and transcriptional controls at the CD79b/GH locus in B cells distinct from those in the pituitary gland and placenta. These three unique transcriptional environments suggest a set of corresponding gene expression pathways and transcriptional interactions that are likely to be found juxtaposed at multiple sites within the eukaryotic genome.

Aberrant expression of ID2, a suppressor of B-cell-specific gene expression, in Hodgkin's lymphoma

The global loss of B-cell-specific gene expression is a distinctive feature of the Hodgkin-Reed/Sternberg (HRS) cells of classical Hodgkin's lymphoma (HL). The reasons for this loss remained largely unknown as transcription factors with pleiotropic effects on B-cell-specific gene expression, namely E2A, EBF, and PAX5, are present in primary HRS cells. We show here that ID2, which can inactivate E2A and perhaps PAX5, is not detectable in normal B cells but is strongly and uniformly expressed in HRS cells of all cases of classical HL. Recurrent chromosomal gains of the ID2 gene might contribute to this aberrant expression. Co-immunoprecipitation of E2A with ID2 from HRS-derived cell lines together with the high amount of ID2 relative to the B-cell transcription factors E2A and PAX5 in HRS-derived cell lines and primary HRS cells indicated that aberrant ID2 expression contributes significantly to the loss of the B-cell-specific gene expression in HRS cells. ID2 was also expressed in lymphocyte-predominance HL, mediastinal large B-cell, diffuse large B-cell, and Burkitt's lymphoma, where lower amounts of ID2 relative to E2A and PAX5 compared with HRS cells might prevent a global down-regulation of B-cell-specific genes and ID2 may contribute to lymphomagenesis in other ways.

Testing gene function early in the B cell lineage in mb1-cre mice

The mb1 gene encodes the Ig-alpha signaling subunit of the B cell antigen receptor and is expressed exclusively in B cells beginning at the very early pro-B cell stage in the bone marrow. We examine here the efficacy of the mb1 gene as a host locus for cre recombinase expression in B cells. We show that by integrating a humanized cre recombinase into the mb1 locus we obtain extraordinarily efficient recombination of loxP sites in the B cell lineage. The results from a variety of reporter genes including the splicing factor SRp20 and the DNA methylase Dnmt1 suggest that mb1-cre is probably the best model so far described for pan-B cell-specific cre expression. The availability of a mouse line with efficient cre-mediated recombination at an early developmental stage in the B lineage provides an opportunity to study the role of various genes specifically in B cell development and function.

Activation of the chicken Ig-beta locus by the collaboration of scattered regulatory regions through changes in chromatin structure

A total of 10 B-lymphocyte-specific DNase I hypersensitive sites located in the chicken Ig-β locus were divided into four regions and combinations of deletions of these regions were carried out. A decrease in transcription of the Ig-β gene to <3% was demonstrated in cells with deletions in all four regions. The Ig-β chromatin was resistant to DNase I digestion in these cells. Thus, the collaboration is shown to convert the Ig-β chromatin from the condensed state to a relaxed state. H3 and H4 acetylation decreased to <8% but H3K4 hypermethylation was observed at the Ig-β promoter and exon 3. The collaboration of four regions had virtually no effect on CG hypomethylation in the region upstream the transcriptional start site. Accordingly, neither the DNase I general sensitive state in the Ig-β chromatin nor hyperacetylation of H3 and H4 histones in the promoter proximal region causes H3K4 di-methylation or CG hypomethylation in the promoter. From these analyses, a chromatin situation was found in which both an active state, such as enhanced H3K4 methylation, or CG hypomethylation, and an inactive state, such as DNase I resistance in the Ig-β chromatin or hypoacetylation of H3 and H4 histones in the Ig-β locus, coexist.

B29 gene silencing in pituitary cells is regulated by its 3' enhancer

B cell-specific B29 (Igbeta, CD79b) genes in rat, mouse, and human are situated between the 5' growth hormone (GH) locus control region and the 3' GH gene cluster. The entire GH genomic region is DNase 1 hypersensitive in GH-expressing pituitary cells, which predicts an "open" chromatin configuration, and yet B29 is not expressed. The B29 promoter and enhancers exhibit histone deacetylation in pituitary cells, but histone deacetylase inhibition failed to activate B29 expression. The B29 promoter and a 3' enhancer showed local dense DNA methylation in both pituitary and non-lymphoid cells consistent with gene silencing. However, DNA methyltransferase inhibition did not activate B29 expression either. B29 promoter constructs were minimally activated in transfected pituitary cells. Co-transfection of the B cell-specific octamer transcriptional co-activator Bob1 with the B29 promoter construct resulted in high level promoter activity in pituitary cells comparable to B29 promoter activity in transfected B cells. Unexpectedly, inclusion of the B29 3' enhancer in B29 promoter constructs strongly inhibited B29 transcriptional activity even when pituitary cells were co-transfected with Bob1. Both Oct-1 and Pit-1 bind the B29 3' enhancer in in vitro electrophoretic mobility shift assay and in in vivo chromatin immunoprecipitation analyses. These data indicate that the GH locus-embedded, tissue-specific B29 gene is silenced in GH-expressing pituitary cells by epigenetic mechanisms, the lack of a B cell-specific transcription factor, and likely by the B29 3' enhancer acting as a powerful silencer in a context and tissue-specific manner.

[Biological characteristics of hyperleukocytic acute leukemia]

The study was to investigate the biological characteristics of hyperleucocyte acute leukemia (HAL) and its clinical significance. Immunophenotyping was performed in 48 HAL patients and 73 NHAL patients by three-color flow cytometry analysis using CD45/SSC gating, meanwhile the cytogenetic analysis was performed in 74 patients. The results showed that as compared with NHAL group, HAL group had lower proportion of eryth-lineage in bone marrow (P < 0.05); in AML, the CD14 expression of HAL group was apparently higher than that of NHAL group (P < 0.05); in ALL, HAL group had higher expression of CD8 and lower expression of CD22, cCD79a compared with NHAL group (P < 0.05); the two groups had no significant difference in expression of special lineage antigens and overlapping lineage antigens (P > 0.05). The CR rate of HAL group was lower than that of NHAL group. It is concluded that bone marrow inhibition of HAL group is more severe than that of NHAL group. In AML, monocytic leukemia is easier to become into HAL than other leukemias. In ALL, T-lineage antigens of HAL group are more easily expressed than those of NHAL group; the leukemia cells of HAL group are naiver than those of NHAL group, meanwhile the prognosis of HAL is poor.

Advanced Granulomatous Lesions in Mycobacterium bovis-infected Cattle are Associated with Increased Expression of Type I Procollagen, γδ (WC1+) T Cells and CD 68+ Cells

The pathognomonic characteristic of tuberculosis (TB) is the formation of a tuberculous granuloma. The objective of this study was to classify lymph node granulomas from experimentally infected calves into different histopathological stages and characterize them further by studying cell types and markers of fibrosis associated with each of the stages. Four stages of granuloma were identified and mRNA and protein expression for cell markers, cytokines and pro-fibrotic markers were studied by immunohistochemistry (IHC) and in-situ hybridization (ISH). In advanced stage granulomas, there was an increase in the expression of TGF-beta, and of type I procollagen as demonstrated by IHC and ISH. As the granulomas advanced, there were fewer CD3+T cells and they tended to be more prominent towards the periphery of the lesions, with a steady increase in the number of CD68+ cells and gammadelta (WC1+) T cells. Granuloma classification and application of cell cytokine markers will assist in improving understanding of the pathogenesis of bovine TB and may help to identify the immunopathology of active disease versus contained or inactive disease. Such disease correlates may help to inform the development of improved diagnostic methods and support vaccine development programmes.