The involvement of the candidate proto-oncogene NFKB2/lyt-10 in lymphoid malignancies

The Recent Research Progress of NF-κB Signaling on the Proliferation, Migration, Invasion, Immune Escape and Drug Resistance of Glioblastoma

Glioblastoma multiforme (GBM) is the most common and invasive primary central nervous system tumor in humans, accounting for approximately 45-50% of all primary brain tumors. How to conduct early diagnosis, targeted intervention, and prognostic evaluation of GBM, in order to improve the survival rate of glioblastoma patients, has always been an urgent clinical problem to be solved. Therefore, a deeper understanding of the molecular mechanisms underlying the occurrence and development of GBM is also needed. Like many other cancers, NF-κB signaling plays a crucial role in tumor growth and therapeutic resistance in GBM. However, the molecular mechanism underlying the high activity of NF-κB in GBM remains to be elucidated. This review aims to identify and summarize the NF-κB signaling involved in the recent pathogenesis of GBM, as well as basic therapy for GBM via NF-κB signaling.

Molecular pathogenesis of Cutaneous T cell Lymphoma: Role of chemokines, cytokines, and dysregulated signaling pathways

Cutaneous T cell lymphomas (CTCLs) are a heterogeneous group of lymphoproliferative neoplasms that exhibit a wide spectrum of immune-phenotypical, clinical, and histopathological features. The biology of CTCL is complex and remains elusive. In recent years, the application of next-generation sequencing (NGS) has evolved our understanding of the pathogenetic mechanisms, including genetic aberrations and epigenetic abnormalities that shape the mutational landscape of CTCL and represent one of the important pro-tumorigenic principles in CTCL initiation and progression. Still, identification of the major pathophysiological pathways including genetic and epigenetic components that mediate malignant clonal T cell expansion has not been achieved. This is of prime importance given the role of malignant T cell clones in fostering T helper 2 (Th2)-bias tumor microenvironment and fueling progressive immune dysregulation and tumor cell growth in CTCL patients, manifested by the secretion of Th2-associated cytokines and chemokines. Alterations in malignant cytokine and chemokine expression patterns orchestrate the inflammatory milieu and influence the migration dynamics of malignant clonal T cells. Here, we highlight recent insights about the molecular mechanisms of CTCL pathogenesis, emphasizing the role of cytokines, chemokines, and associated downstream signaling networks in driving immune defects, malignant transformation, and disease progression. In-depth characterization of the CTCL immunophenotype and tumoral microenvironment offers a facile opportunity to expand the therapeutic armamentarium of CTCL, an intractable malignant skin disease with poor prognosis and in dire need of curative treatment approaches.

Molecular and Genomic Landscape of Peripheral T-Cell Lymphoma

Peripheral T-cell lymphoma (PTCL) is an uncommon group of lymphoma covering a diverse spectrum of entities. Little was known regarding the molecular and genomic landscapes of these diseases until recently but the knowledge is still quite spotty with many rarer types of PTCL remain largely unexplored. In this chapter, the recent findings from gene expression profiling (GEP) studies, including profiling data on microRNA, where available, will be presented with emphasis on the implication on molecular diagnosis, prognostication, and the identification of new entities (PTCL-GATA3 and PTCL-TBX21) in the PTCL-NOS group. Recent studies using next-generation sequencing have unraveled the mutational landscape in a number of PTCL entities leading to a marked improvement in the understanding of their pathogenesis and biology. While many mutations are shared among PTCL entities, the frequency varies and certain mutations are quite unique to a specific entity. For example, TET2 is often mutated but this is particularly frequent (70-80%) in angioimmunoblastic T-cell lymphoma (AITL) and IDH2 R172 mutations appear to be unique for AITL. In general, chromatin modifiers and molecular components in the CD28/T-cell receptor signaling pathways are frequently mutated. The major findings will be summarized in this chapter correlating with GEP data and clinical features where appropriate. The mutational landscape of cutaneous T-cell lymphoma, specifically on mycosis fungoides and Sezary syndrome, will also be discussed.

Tracing the dynamic expression of the Nfκb2 gene during inflammatory processes by in vivo bioluminescence imaging in transgenic mice

Nfκb2(p52/p100) plays essential roles in many chronic inflammatory diseases. Tracing the dynamic expression of Nfκb2 during different biological processes in vivo can provide valuable clues to understand the biological functions of this gene and develop anti-inflammatory drugs. In this study, B6-Tg(Nfκb2-luc)^Mlit transgenic mouse line, a mouse model in which the expression of firefly luciferase gene is under the control of a 14.6-kb mouse Nfκb2 promoter, was generated to monitor the expression of p52/p100 in vivo. Bioluminescence imaging was used for tracking the luciferase signal in living mice in a variety of inflammatory processes, including LPS-induced sepsis and inflammatory bowel disease (IBD). The data of in vivo bioluminescence imaging in this mouse model showed that luciferase activity coincided with the endogenous p52/p100 expression. Moreover, dexamethasone or aspirin, two routine anti-inflammatory drugs, could decrease the high-level expression of luciferase induced by LPS. Overall, our results suggest that the B6-Tg(Nfκb2-luc)^Mlit mice represent a valuable reporter mouse model not only to monitor the expression of p52/p100 in physiological or pathological processes but also to evaluate the effects of various anti-inflammatory drug treatments in vivo.

Analysis of NFKB2‑mediated regulation of mechanisms underlying the development of Hodgkin's lymphoma

Nuclear factor-κB (NF-κB) is widely involved in various lymphoid malignancies. However, its exact functional role and potential regulatory mechanisms in Hodgkin's lymphoma (HL) remains unclear. The present study aimed to investigate the regulatory mechanism of NF-κB in HL by analysis of a gene expression profile that was obtained from HL cells with or without NF-κB subunit 2 (NFKB2) knockdown. The GSE64234 dataset containing 6 HL cell line specimens transfected with small interfering (si)RNA against NFKB2 and 6 control specimens transfected with non-targeting siRNA sequences was downloaded from the Gene Expression Omnibus database. Based on these data, differentially expressed genes (DEGs) were screened for following data preprocessing. Functional enrichment analysis was subsequently conducted among the identified upregulated and downregulated DEGs. Additionally, a protein-protein interaction (PPI) network was constructed and module analyses were performed. Finally, microRNAs (miRNAs/miRs) targeting the identified DEGs were predicted for the construction of a miRNA-target regulatory network. A total of 253 DEGs were identified, consisting of 109 upregulated and 144 downregulated DEGs. Pathway enrichment analysis revealed that B-cell lymphoma 2-like 1 (BCL2L1) was significantly enriched in the NF-κB signaling pathway, and colony-stimulating factor 2 (CSF2) and BCL2L1 were enriched in the Jak-signal transducer and activator of transcription (STAT) signaling pathway. BCL2L1 and CSF2 were determined to be hub genes in the PPI network. A total of 6 miRNAs, including let-7a-5p, miR-9-5p, miR-155-5p, miR-135a-5p, miR-17-5p and miR-375, were identified in the miRNA-target regulatory network. The results of the present study indicated that NFKB2 may be involved in HL development through regulation of BCL2L1, CSF2, miR-135a-5p, miR-155-5p and miR-9-5p expression, as well as the modulation of Jak-STAT and NF-κB signaling pathways.

Genomic landscape of cutaneous T cell lymphoma

Cutaneous T cell lymphoma (CTCL) is a non-Hodgkin lymphoma of skin-homing T lymphocytes. We performed exome and whole genome DNA sequence and RNA sequencing on purified CTCL and matched normal cells. The results implicate mutations in 17 genes in CTCL pathogenesis, including genes involved in T cell activation and apoptosis, NFκB signaling, chromatin remodeling, and DNA damage response. CTCL is distinctive in that somatic copy number variants (SCNVs) comprise 92% of all driver mutations (mean of 11.8 pathogenic SCNVs vs. 1.0 somatic single nucleotide variants per CTCL). These findings have implications for novel therapeutics.

Balance between NF-κB p100 and p52 regulates T cell costimulation dependence

c-IAP1 and c-IAP2 are ubiquitin protein ligases (E3s) that repress noncanonical NF-κB activation. We have created mice that bear a mutation in c-IAP2 that inactivates its E3 activity and interferes, in a dominant-negative fashion, with c-IAP1 E3 activity (c-IAP2(H570A)). The immune response of these animals was explored by infecting them with the Th1-inducing parasite Toxoplasma gondii. Surprisingly, c-IAP2(H570A) mice succumbed because of T cell production of high levels of proinflammatory cytokines. Unlike naive wild-type (WT) cells, which require signals generated by the TCR and costimulatory receptors to become fully activated, naive c-IAP2(H570A) T cells proliferated and produced high levels of IL-2 and IFN-γ to stimulation via TCR alone. c-IAP2(H570A) T cells had constitutive noncanonical NF-κB activation, and IκB kinase inhibition reduced their proliferation to anti-TCR alone to WT levels but had no effect when costimulation via CD28 was provided. Notably, T cells from nfkb2(-/-) mice, which cannot generate the p52 component of noncanonical NF-κB, were also costimulation independent, consistent with the negative role of this unprocessed protein in canonical NF-κB activation. Whereas T cells from nfkb2(+/-) mice behaved like WT, coexpression of a single copy of c-IAP2(H570A) resulted in cleavage of p100, upregulation of p52, and T cell costimulation independence. Thus, p100 represses and p52 promotes costimulation, and the ratio regulates T cell dependence on costimulatory signals.

A single NFκB system for both canonical and non-canonical signaling

Two distinct nuclear factor κB (NFκB) signaling pathways have been described; the canonical pathway that mediates inflammatory responses, and the non-canonical pathway that is involved in immune cell differentiation and maturation and secondary lymphoid organogenesis. The former is dependent on the IκB kinase adaptor molecule NEMO, the latter is independent of it. Here, we review the molecular mechanisms of regulation in each signaling axis and attempt to relate the apparent regulatory logic to the physiological function. Further, we review the recent evidence for extensive cross-regulation between these two signaling axes and summarize them in a wiring diagram. These observations suggest that NEMO-dependent and -independent signaling should be viewed within the context of a single NFκB signaling system, which mediates signaling from both inflammatory and organogenic stimuli in an integrated manner. As in other regulatory biological systems, a systems approach including mathematical models that include quantitative and kinetic information will be necessary to characterize the network properties that mediate physiological function, and that may break down to cause or contribute to pathology.

Regions of acquired uniparental disomy at diagnosis of follicular lymphoma are associated with both overall survival and risk of transformation

Acquired homozygosity in the form of segmental acquired uniparental disomy (aUPD) has been described in follicular lymphoma (FL) and is usually due to mitotic recombination. SNP array analysis was performed with the use of the Affymetrix 10K 2.0 Gene-chip array on DNA from 185 diagnostic FL patients to assess the prognostic relevance of aUPD. Genetic abnormalities were detected in 118 (65%) of 182 patients. Number of abnormalities was predictive of outcome; more than 3 abnormalities was associated with inferior overall survival (OS; P < .03). Sites of recurrent aUPD were detected on 6p (n = 25), 16p (n = 22), 12q (n = 17), 1p36 (n = 14), 10q (n = 8), and 6q (n = 8). On multivariate analysis aUPD on 1p36 correlated with shorter OS (P = .05). aUPD on 16p was predictive of transformation (P = .03) and correlated with poorer progression-free survival (P = .02). aUPD is frequent at diagnosis of FL and affects probability of disease transformation and clinical outcome.

The role of NF-kappaB in lymphoid malignancies

Nuclear Factor kappaB (NF-kappaB) transcription factors are central regulators of lymphocyte proliferation, survival and development. Although normally subject to tight control, constitutive activation of NF-kappaB promotes inappropriate lymphocyte survival and proliferation, and is recognised as key pathological feature in various lymphoid malignancies. Inhibition of NF-kappaB may be an attractive therapeutic approach in these diseases. This review focuses on the mechanisms and functional consequences of NF-kappaB activation in lymphoid malignancies and potential therapeutic strategies for inhibition of NF-kappaB.

Rearranged NF-kappa B2 gene in an adult T-cell leukemia cell line

Adult T-cell leukemia (ATL) is an aggressive type of leukemia, originating from T-cells infected with human T-cell leukemia virus type 1. Accumulating evidence suggests the aberrant activation of NF-kappaB to be a causative factor mediating the abnormal proliferation of leukemic cells, thus resulting in the development of ATL. A rearranged NF-kappa B2/p100 gene was isolated from an ATL-derived cell line, which was generated by a chromosomal translocation. The isolated NF-kappa B2 mutant is fused with the with no (lysine) deficient protein kinase 1 gene, coding for a 58 kDa protein that retains the DNA binding Rel homology domain, but it lacks the entire ankyrin repeat inhibitory domain, thus suggesting its constitutive activation. This rearranged NF-kappa B2 gene product (p58) was localized in the nucleus, and formed a complex with NF-kappaB p65 or RelB. Moreover, a T-cell line expressing p58 increased the amount of an NF-kappa B2-inducible gene, NF-kappa B2/p100 by itself. These results suggest that such NF-kappa B2 gene rearrangement may therefore be a factor in the constitutive activation of NF-kappaB in ATL, and thereby playing a role in the ATL pathogenesis.

Constitutive alternative NF-kappaB signaling promotes marginal zone B-cell development but disrupts the marginal sinus and induces HEV-like structures in the spleen

Nuclear factor-kappaB (NF-kappaB) plays a crucial role in B-cell and lymphoid organ development. Here, we studied the consequences of constitutive, signal-independent activation of the alternative NF-kappaB pathway for the splenic marginal zone (MZ). In contrast to nfkb2(-/-) mice, which lack both p100 and p52, mice that lack only the inhibitory p100 precursor but still express the p52 subunit of NF-kappaB2 (p100(-/-)) had markedly elevated MZ B-cell numbers. Both cell-intrinsic mechanisms and increased stromal expression of vascular cell adhesion molecule-1 (VCAM-1) contributed to the accumulation of MZ B cells in p100(-/-) spleens. While migration of p100(-/-) MZ B cells toward the lysophospholipid sphingosine-1 phosphate (S1P) was not affected, CXCL13-stimulated chemotaxis was impaired, correlating with reduced migration of MZ B cells into follicles in response to lipopolysaccharide (LPS). Strikingly, p100 deficiency resulted in the absence of a normal marginal sinus, strongly induced expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) and glycosylated cell adhesion molecule-1 (GlyCAM-1), and the formation of nonfunctional ectopic high endothelial venule (HEV)-like structures in the red pulp. Thus, constitutive activation of the alternative NF-kappaB pathway favors MZ B-cell development and accumulation but leads to a disorganized spleen microarchitecture.

Mutations in the NF-kappaB signaling pathway: implications for human disease

The nuclear factor-kappa B (NF-kappaB) signaling pathway is a multi-component pathway that regulates the expression of hundreds of genes that are involved in diverse and key cellular and organismal processes, including cell proliferation, cell survival, the cellular stress response, innate immunity and inflammation. Not surprisingly, mis-regulation of the NF-kappaB pathway, either by mutation or epigenetic mechanisms, is involved in many human and animal diseases, especially ones associated with chronic inflammation, immunodeficiency or cancer. This review describes human diseases in which mutations in the components of the core NF-kappaB signaling pathway have been implicated and discusses the molecular mechanisms by which these alterations in NF-kappaB signaling are likely to contribute to the disease pathology. These mutations can be germline or somatic and include gene amplification (e.g., REL), point mutations and deletions (REL, NFKB2, IKBA, CYLD, NEMO) and chromosomal translocations (BCL-3). In addition, human genetic diseases are briefly described wherein mutations affect protein modifiers or transducers of NF-kappaB signaling or disrupt NF-kappaB-binding sites in promoters/enhancers.

Activation of non-canonical NF-kappaB pathway mediated by STP-A11, an oncoprotein of Herpesvirus saimiri

Although Saimiri Transforming Protein (STP)-A11, an oncoprotein of Herpesvirus saimiri, has been known to activate NF-kappaB signaling pathway, the detailed mechanism has not been reported yet. We herein report that STP-A11 activates non-canonical NF-kappaB pathway, resulting in p100 processing to p52. In addition, translocation of p52 protein (NF-kappaB2) into the nucleus is observed by the expression of STP-A11. STP-A11-mediated processing of p100 to p52 protein requires proteosome-mediated proteolysis because MG132 treatment clearly blocked p52 production in spite of the expression of STP-A11. Analysis of STP-A11 mutants to activate NF-kappaB2 pathway discloses the requirement of TRAF6-binding site not Src-binding site for STP-A11-mediated NF-kappaB2 pathway. Blockage of STP-A11-mediated p52 production using siRNA against p52 enhanced a chemotherapeutic drug-mediated cell death, suggesting that p52 production induced by the expression of STP-A11 would contribute to cellular transformation, which results from a resistance to cell death.

The alternative NF-kappaB pathway from biochemistry to biology: pitfalls and promises for future drug development

The past two decades have led to a tremendous work on the transcription factor NF-kappaB and its molecular mechanisms of activation. The nuclear translocation of NF-kappaB is controlled by two main pathways: the classical and the alternative NF-kappaB pathways. The classical NF-kappaB pathway activates the IKK complex that controls the inducible degradation of most IkappaB family members that are IkappaBalpha, IkappaBbeta, IkappaBvarepsilon and p105. The alternative NF-kappaB pathway induces p100 processing and p52 generation through the activation of at least two kinases, which are NIK and IKKalpha. Genetic studies have shown that IKKgamma is dispensable for the alternative pathway, which suggests the existence of an alternative IKKalpha-containing complex. It is noteworthy that activation of particular p52 heterodimers like p52/RelB requires solely the alternative pathway while activation of p52/p65 or p52/c-Rel involves a "hybrid pathway". Among others, LTbetaR, BAFF-R, CD40 and RANK have the ability to induce the alternative pathway. The latter plays some roles in biological functions controlled by these receptors, which are the development of secondary lymphoid organs, the proliferation, survival and maturation of B cell, and the osteoclastogenesis. Exacerbated activation of the alternative pathway is potentially associated to a wide range of disorders like rheumatoid arthritis, ulcerative colitis or B cell lymphomas. Therefore, inhibitors of the alternative pathway could be valuable tools for the treatment of inflammatory disorders and cancers.

Development of multiple myeloma in a patient with chronic hepatitis C: A case report and review of the literature

An association between chronic hepatitis C virus (HCV) infection and essential mixed cryoglobulinaemia and non-Hodgkin lymphoma (NHL) has been suggested. However, a causative role of HCV in these conditions has not been established. The authors report a case of a 50 year-old woman with chronic hepatitis C (CHC) who has been followed up since 1998 due to a high viral load, genotype 1b and moderately elevated liver function tests (LFTs). Laboratory data and liver biopsy revealed moderate activity (grade: 5/18, stage: 1/6). In April 1999, one-year interferon therapy was started. HCV-RNA became negative with normalization of LFTs. However, the patient relapsed during treatment. In September 2002, the patient was admitted for chronic back pain. A CT examination demonstrated degenerative changes. In March 2003, multiple myeloma was diagnosed (IgG-kappa, bone ma-rrow biopsy: 50% plasma cell infiltration). MRI revealed a compression fracture of the 5^th lumbar vertebral body and an abdominal mass in the right lower quadrant, infiltrating the canalis spinalis. Treatment with vincristine, adriamycin and dexamethasone (VAD) was started and bisphosphonate was administered regularly. In January 2004, after six cycles of VAD therapy, the multiple myeloma regressed. Thalidomide, as a second line trea-tment of refractory multiple myeloma (MM) was initiated, and followed by peginterferon-α2b and ribavirin against the HCV infection in June. In June 2005, LFTs returned to normal, while HCV-RNA was negative, demonstrating an end of treatment response. Although a pathogenic role of HCV infection in malignant lymphoproliferative disorders has not been established, NHL and possibly MM may develop in CHC patients, supporting a role of a complex follow-up in these patients.

Activation of NF-kappaB by HTLV-I and implications for cell transformation

T-cell transformation by the human T-cell leukemia virus type I (HTLV-I) involves deregulation of cellular transcription factors, including members of the NF-kappaB family. In normal T cells, NF-kappaB activation occurs transiently in response to immune stimuli, which is required for antigen-stimulated T-cell proliferation and survival. However, HTLV-I induces persistent activation of NF-kappaB, causing deregulated expression of a large array of cellular genes, which in turn contributes to the induction of T-cell transformation. The HTLV-I transforming protein Tax functions as an intracellular stimulator of IkappaB kinase (IKK), a cellular kinase mediating NF-kappaB activation by diverse stimuli. Tax physically interacts with IKK and renders this inducible kinase constitutively active. By assembling different Tax/IKK complexes, Tax targets the persistent activation of both canonical and noncanonical NF-kappaB signaling pathways. Whereas Tax plays a primary role in HTLV-I-mediated NF-kappaB activation, recent studies reveal that the IKK/NF-kappaB signaling pathway is also activated in freshly isolated adult T-cell leukemia (ATL) cells that often lack detectable Tax expression. The mechanism underlying this Tax-independent pathway of NF-kappaB activation remains poorly understood. Clarifying the precise nature and consequences of the constitutive NF-kappaB activation in ATL cells is important for developing rational therapeutic strategies for this T-cell malignancy.

Mechanism of processing of the NF-kappa B2 p100 precursor: identification of the specific polyubiquitin chain-anchoring lysine residue and analysis of the role of NEDD8-modification on the SCF(beta-TrCP) ubiquitin ligase

Processing of the NF-kappa B2 precursor p100 to the mature p52 subunit is regulated via a unique pathway. NF-kappa B-inducing kinase (NIK) induces I kappa B kinase alpha (IKK alpha)-mediated phosphorylation of specific serine residues in the C-terminal domain of p100, leading to recruitment of the SCF(beta-TrCP) ubiquitin ligase. We identified a single lysine residue, K855, that serves as the ubiquitin-anchoring residue required for signal-induced processing of p100. In a reconstituted system containing purified components, p100-K855R could not be ubiquitinated. In a crude extract and cells, only residual, signal-independent ubiquitination and processing were retained. Importantly, K855 is located in a site homologous to K22 that serves as an ubiquitination site in I kappa B alpha. This suggests a common recognition mechanism for the two molecules. In contrast, p105, the p100 homologue, lacks a similar Lys residue. We also demonstrate that the NEDD8 pathway is essential for the SCF(beta-TrCP) activity. In a reconstituted system, efficient ubiquitination of p100 required all three components of the pathway - E1, the UBC12 E2 and NEDD8. Experiments in reconstituted systems and in cells demonstrated that SCF(beta-TrCP), which contains a mutant Cul-1 that cannot be NEDDylated, cannot stimulate ubiquitination and processing. Similarly, dominant negative UBC12 inhibits, in a reversible manner, both ubiquitination and processing of p100.

Regulation of NF-kappaB2/p100 processing by its nuclear shuttling

Processing of the NF-kappaB2 precursor protein p100 to generate p52 is an important step of NF-kappaB regulation. This proteolytic event is tightly regulated by sequences located at the C-terminal portion of p100. Constitutive processing of p100 occurs in certain lymphoma cells due to the loss of its C-terminal regulatory domain, although the underlying mechanisms remain unknown. We show here that the constitutive processing of C-terminal truncation mutants of p100 is associated with their active nuclear translocation. Deletion of the C-terminal death domain of p100 triggers a low, but significant, level of nuclear translocation and processing. Disruption of the ankyrin-repeat domain of p100 further enhances its nuclear shuttling activity, which is again associated with elevated level of processing. More importantly, mutation of the nuclear localization signal (NLS) of p100 abolishes its processing, and this defect can be rescued by fusion of a heterologous NLS to the amino- or carboxyl-terminus of the p100 mutant. These results suggest that nuclear shuttling is a mechanism regulating the processing of NF-kappaB2/p100.

Refined physical map of the human PAX2/HOX11/NFKB2 cancer gene region at 10q24 and relocalization of the HPV6AI1 viral integration site to 14q13.3-q21.1

BACKGROUND

Chromosome band 10q24 is a gene-rich domain and host to a number of cancer, developmental, and neurological genes. Recurring translocations, deletions and mutations involving this chromosome band have been observed in different human cancers and other disease conditions, but the precise identification of breakpoint sites, and detailed characterization of the genetic basis and mechanisms which underlie many of these rearrangements has yet to be resolved. Towards this end it is vital to establish a definitive genetic map of this region, which to date has shown considerable volatility through time in published works of scientific journals, within different builds of the same international genomic database, and across the differently constructed databases.

RESULTS

Using a combination of chromosome and interphase fluorescent in situ hybridization (FISH), BAC end-sequencing and genomic database analysis we present a physical map showing that the order and chromosomal orientation of selected genes within 10q24 is CEN-CYP2C9-PAX2-HOX11-NFKB2-TEL. Our analysis has resolved the orientation of an otherwise dynamically evolving assembly of larger contigs upstream of this region, and in so doing verifies the order and orientation of a further 9 cancer-related genes and GOT1. This study further shows that the previously reported human papillomavirus type 6a DNA integration site HPV6AI1 does not map to 10q24, but that it maps at the interface of chromosome bands 14q13.3-q21.1.

CONCLUSIONS

This revised map will allow more precise localization of chromosome rearrangements involving chromosome band 10q24, and will serve as a useful baseline to better understand the molecular aetiology of chromosomal instability in this region. In particular, the relocation of HPV6AI1 is important to report because this HPV6a integration site, originally isolated from a tonsillar carcinoma, was shown to be rearranged in other HPV6a-related malignancies, including 2 of 25 genital condylomas, and 2 of 7 head and neck tumors tested. Our finding shifts the focus of this genomic interest from 10q24 to the chromosome 14 site.

NF-?B activation in human prostate cancer: Important mediator or epiphenomenon?

The NF-kappaB family of transcription factors has been shown to be constitutively activated in various human malignancies, including leukemias, lymphomas, and a number of solid tumors. NF-kappaB is hypothesized to contribute to development and/or progression of malignancy by regulating the expression of genes involved in cell growth and proliferation, anti-apoptosis, angiogenesis, and metastasis. Prostate cancer cells have been reported to have constitutive NF-kappaB activity due to increased activity of the IkappaB kinase complex. Furthermore, an inverse correlation between androgen receptor (AR) status and NF-kappaB activity was observed in prostate cancer cell lines. NF-kappaB may promote cell growth and proliferation in prostate cancer cells by regulating expression of genes such as c-myc, cyclin D1, and IL-6. NF-kappaB may also inhibit apoptosis in prostate cancer cells through activation of expression of anti-apoptotic genes, such as Bcl-2, although pro-apoptotic activity of NF-kappaB has also been reported. NF-kappaB-mediated expression of genes involved in angiogenesis (IL-8, VEGF), and invasion and metastasis (MMP9, uPA, uPA receptor) may further contribute to the progression of prostate cancer. Constitutive NF-kappaB activity has also been demonstrated in primary prostate cancer tissue samples and suggested to have prognostic importance for a subset of primary tumors. The limited number of samples analyzed in those studies and the relative lack of NF-kappaB target genes identified in RNA expression microarray analyses of prostate cancer cells suggest that further studies will be required in order to determine if NF-kappaB actually plays a role in human prostate cancer development, and/or progression, and to characterize its potential as a therapeutic target.

S9, a 19 S proteasome subunit interacting with ubiquitinated NF-kappaB2/p100

Proteasome-mediated processing of the nfkappab2 gene product p100 is a regulated event that generates the NF-kappaB subunit p52. This event can be induced through p100 phosphorylation by a signaling pathway involving the nuclear factor-kappaB-inducing kinase (NIK). The C-terminal region of p100, which contains its phosphorylation site and a death domain, plays a pivotal role in regulating the processing of p100. To understand the biochemical mechanism of p100 processing, we searched for cellular factors interacting with the C-terminal regulatory region of p100 using the yeast two-hybrid system. This led to the identification of S9, a non-ATPase subunit of the 19 S proteasome with no known functions. Interestingly, the S9/p100 interaction could be induced by NIK but not by a catalytically inactive NIK mutant. This inducible molecular interaction required p100 ubiquitination and was dependent on the intact death domain. We further demonstrated that the death domain is essential for NIK-induced post-translational processing of p100, thus providing a functional link between the S9 binding and the processing of p100. Finally, we provide genetic evidence for the essential role of S9 in the inducible processing of p100.

New genes involved in cancer identified by retroviral tagging

Retroviral insertional mutagenesis in BXH2 and AKXD mice induces a high incidence of myeloid leukemia and B- and T-cell lymphoma, respectively. The retroviral integration sites (RISs) in these tumors thus provide powerful genetic tags for the discovery of genes involved in cancer. Here we report the first large-scale use of retroviral tagging for cancer gene discovery in the post-genome era. Using high throughput inverse PCR, we cloned and analyzed the sequences of 884 RISs from a tumor panel composed primarily of B-cell lymphomas. We then compared these sequences, and another 415 RIS sequences previously cloned from BXH2 myeloid leukemias and from a few AKXD lymphomas, against the recently assembled mouse genome sequence. These studies identified 152 loci that are targets of retroviral integration in more than one tumor (common retroviral integration sites, CISs) and therefore likely to encode a cancer gene. Thirty-six CISs encode genes that are known or predicted to be genes involved in human cancer or their homologs, whereas others encode candidate genes that have not yet been examined for a role in human cancer. Our studies demonstrate the power of retroviral tagging for cancer gene discovery in the post-genome era and indicate a largely unrecognized complexity in mouse and presumably human cancer.

RelB cellular regulation and transcriptional activity are regulated by p100

RelB mediates the constitutive nuclear pool of NF-kappaB transcriptional activity in myeloid and lymphoid cells, which is believed to be secondary to its weak interaction with the classical NF-kappaB inhibitor proteins, the IkappaBs. In other cell types, RelB is located in the cytosol, thus suggesting that RelB is also regulated by an inhibitory protein(s). In this study, it is demonstrated that RelB is associated in the cytosol with p100 but not with IkappaBalpha, IkappaBbeta, IkappaBepsilon, nor p105. Its cytosolic control is not affected by stimuli that lead to RelA nuclear translocation, and RelB nuclear localization is prevented by p100, but not by p105 or IkappaBalpha. Structure function analysis p100-RelB interactions indicates that p100 amino acids 623-900 are required for effective interaction and repression of nuclear translocation and RelB driven NF-kappaB-dependent transcription. Moreover, this carboxyl-portion of p100 contains a nuclear export signal(s), which is required for effective retrieval of RelB from the nucleus. Finally, overexpression of NF-kappaB-inducing kinase, a kinase that has recently been shown to induce p100 processing, possibly through IKKalpha activation, causes nuclear translocation of RelB protein. Thus, these studies indicate that p100 is a bone fide inhibitor of RelB and that this transcription factor may be regulated by NF-kappaB-inducing kinase and/or IKKalpha.

Transcriptional regulatory effects of lymphoma-associated NFKB2/lyt10 protooncogenes

C-terminal truncations of the NFKB2 p100 gene product have been observed in a number of cases of human cutaneous T cell lymphomas, as well as human B-cell lymphomas and myelomas. The contribution of these alterations to lymphomagenesis is not understood; however, truncation at amino acid 666 to generate 80 - 85 kD proteins in the HUT78 cell line is associated with addition of a short (serine-alanine-serine) fusion at the 3' end of p80HT, as well as with increased expression of NFKB2 mRNA. We therefore examined the effects of p80HT on the regulation of NFKB2 expression, as well as the properties of a series of other tumor-associated, and site directed mutations of NFKB2. While p80HT had not itself acquired novel transcriptional activation properties with respect to the NFKB2 P1 or P2 promoters or the IL-6 kappaB promoter, p80HT had lost the potent inhibitory (IkappaB-like) activity associated with the wild-type, p100 gene product. Loss of the inhibitory property depended on the SAS residues in the fusion protein, direct truncation at aa666 was fully inhibitory, as was a substitution of three alanines for the SAS residues. The presence of as few as two C-terminal ankyrin motifs was sufficient for inhibition of NF-kappaB-mediated transcriptional activation. Assays of a series of additional lymphoma-associated NF-kappaB-2 truncation suggested that the C-terminal truncation associated with these proteins was also associated with a loss of the IkappaB-like activities of p100 NF-kappaB-2, for at least some NF-kappaB target promoters. Thus, the loss of IkappaB-like activity of lymphoma-associated NFKB2 mutations may play an important role in the genesis of a subset of human lymphomas.

The generation of nfkb2 p52: mechanism and efficiency

nfkb2 encodes two members of the NF-kappa B/Rel family of proteins: p52 and p100. The p100 polypeptide has been proposed to serve as a precursor of p52, which corresponds to the N-terminal half of p100. While p52 functions as a Rel transcription factor, the larger p100 protein acts as a cytoplasmic inhibitor of select NF-kappa B/Rel transcription factor complexes. Because of their distinct functions, we have studied the biochemical basis for the production of these two nfkb2-derived gene products. Like the p50 product of the nfkb1 gene, p52 is principally generated in a cotranslational manner involving proteolytic processing by the proteasome. The generation of p52 is dependent on a glycine-rich region (GRR) located upstream of the p52 C-terminus, and repositioning of this GRR alters the location of proteasome processing. In most cells, small amounts of p52 are produced relative to the levels of p100, unlike the usually balanced production of nfkb1-derived p50 and p105. Using p100/p105 chimeras containing different segments of the nfkb1 and nfkb2 genes, we have found that diminished p52 processing is a property conferred by peptide sequences located downstream of the GRR, flanking the site of p52 processing.

Sequence of 10q24 locus surrounding the HOX11 oncogene reveals a new gene HUG1 expressed in a T-ALL cell line

HOX11 is a gene encoding a homeobox protein which is found to be deregulated in T-cell acute lymphoblastic leukaemia (T-ALL). As a basis for studying the mechanism of deregulation of HOX11 expression in leukaemia, the locus containing the HOX11 proto-oncogene at 10q24 was cloned from a genomic P1 Artificial Chromosome (PAC) library. The PAC clone with an insert size of 120kb was isolated and mapped by restriction analysis. A series of contiguous subclones were then obtained which span 20kb surrounding the HOX11 gene. These subclones were used to sequence across the entire 20kb region to the 3' boundary of the PAC insert. This work provides for the first time the full intron and 5' non-coding sequences of the HOX11 gene which will aid the identification of novel transcriptional control elements which may be involved in silencing HOX11 expression in normal cells. The sequence information was also used to search for novel large open reading frames (ORFs). One such ORF (1.1kb) would encode a protein of at least 39kDa. This basic protein (pI, 12.5) would be very proline rich and could potentially encode a novel transcription factor. In order to establish if this ORF corresponds to a bona fide transcribed gene, RT-PCR analysis was performed. The mRNA for this protein is expressed in the T-ALL cell line Jurkat and has been designated HUG1, for HOX11 Upstream Gene.

Mice deficient in nuclear factor (NF)-kappa B/p52 present with defects in humoral responses, germinal center reactions, and splenic microarchitecture

p52 is a subunit of nuclear factor (NF)-kappa B transcription factors, most closely related to p50. Previously, we have shown that p52, but not p50 homodimers can form transactivating complexes when associated with Bcl-3, an unusual member of the I kappa B family. To determine nonredundant physiologic roles of p52, we generated mice deficient in p52. Null mutant mice were impaired in their ability to generate antibodies to T-dependent antigens, consistent with an absence of B cell follicles and follicular dendritic cell networks in secondary lymphoid organs, and an inability to form germinal centers. Furthermore, the splenic marginal zone was disrupted. These phenotypes are largely overlapping with those observed in Bcl-3 knockout animals, but distinct from those of p50 knockouts, supporting the notion of a physiologically relevant complex of p52 homodimers and Bcl-3. Adoptive transfer experiments further suggest that such a complex may be critical in accessory cell functions during antigen-specific immune reactions. Possible roles of p52 and Bcl-3 are discussed that may underlie the oncogenic potential of these proteins, as evidenced by recurrent chromosomal translocations of their genes in lymphoid tumors.