[Individualized precision medicine]

Spectacular advances have been made in personalized medicine , which has rapidly revolutionized our traditional understanding of disease diagnosis and treatment. Molecular testing of tissue and liquid samples using next generation sequencing has developed into a key technology in this scenario. It can be used for both the determination of biomarkers for diagnostic, prognostic and predictive purposes, as well as the possible improvement of treatment outcome through the use of targeted therapies and the avoidance of therapies in the event of special resistance situations. In addition to drugs that have already been approved, which among other things intervene in cellular DNA repair, many new drugs have been developed and are in clinical testing. Furthermore, new possibilities in molecular imaging have dramatically expanded our understanding of tumor spread and created new approaches for targeted therapies.

Label-free discrimination of extracellular vesicles from large lipoproteins

Extracellular vesicles (EVs) are increasingly gaining interest as biomarkers and therapeutics. Accurate sizing and quantification of EVs remain problematic, given their nanometre size range and small scattering cross-sections. This is compounded by the fact that common EV isolation methods result in co-isolation of particles with comparable features. Especially in blood plasma, similarly-sized lipoproteins outnumber EVs to a great extent. Recently, interferometric nanoparticle tracking analysis (iNTA) was introduced as a particle analysis method that enables determining the size and refractive index of nanoparticles with high sensitivity and precision. In this work, we apply iNTA to differentiate between EVs and lipoproteins, and compare its performance to conventional nanoparticle tracking analysis (NTA). We show that iNTA can accurately quantify EVs in artificial EV-lipoprotein mixtures and in plasma-derived EV samples of varying complexity. Conventional NTA could not report on EV numbers, as it was not able to distinguish EVs from lipoproteins. iNTA has the potential to become a new standard for label-free EV characterization in suspension.

Multi-Antigen Imaging Reveals Inflammatory DC, ADAM17 and Neprilysin as Effectors in Keloid Formation

Keloid is an aberrant scarring process of the skin, characterized by excessive extracellular matrix synthesis and deposition. The pathogenesis of this prevalent cutaneous disorder is not fully understood; however, a persistent inflammatory process is observed. To obtain more insight into this process, we analyzed lesional, perilesional and healthy tissue using multi-antigen-analysis (MAA) in conjunction with a data mining approach. Here, we demonstrate that monocyte-derived inflammatory dendritic cells (CD1a+, CD11c+, CD14+) and activated CD4+ T lymphocytes (CD45 RO+) dominated the immune infiltration in keloids while associating with fibroblasts. In perilesional tissue, precursor immune cells were dominant in the perivascular area, suggesting that they were attracted by an immune process, potentially in the lesional area. Supporting this hypothesis, only in keloid lesions, high levels of ADAM10/17 and Neprilysin (CD10) were observed in both fibroblasts and leukocytes. The spatial proximity of these two cell types, which could be confirmed by image analysis only in lesional tissue, could be a potential factor leading to the activation of fibroblasts. Our findings provide new insight into the pathogenesis of keloid formation and reveal metalloproteinases as a target for therapeutical intervention.

Evidence for liver and peripheral immune cells secreting tumor-suppressive extracellular vesicles in melanoma patients

Background

Before and after surgery melanoma patients harbor elevated levels of extracellular vesicles in plasma (pEV), suppressing tumor cell activity. However, due to technical reasons and lack of cell-specific biomarkers, their cellular origin remains obscure.

Methods

We mimicked the interaction of tumor cells with liver cells and PBMC in vitro, and compared newly secreted EV-associated miRNAs and protein factors with those detected in melanoma patient`s pEV.

Findings

Our results suggest that pEV from melanoma patients are secreted in part by residual or relapsing tumor cells, but also by liver and peripheral blood mononuclear cells (PBMC). Our approach identified factors that were seemingly associated either with tumor cell activity, or the counteracting immune system, including liver cells. Notably, the presence/absence of these factors correlated with the clinical stage and tumor relapse.

Interpretation

Our study may provide new insights into the innate immune defense against tumor cells and implies that residual tumor cells could be more active than previously thought. In addition we provide some preliminary evidence that pEV marker patterns could be used to predict cancer relapse.

Palmitoylated Proteins on AML-Derived Extracellular Vesicles Promote Myeloid-Derived Suppressor Cell Differentiation via TLR2/Akt/mTOR Signaling

Acute myeloid leukemia (AML) represents the most common acute leukemia among adults. Despite recent progress in diagnosis and treatment, long-term outcome remains unsatisfactory. The success of allogeneic stem cell transplantation underscores the immunoresponsive nature of AML, creating the basis for further exploiting immunotherapies. However, emerging evidence suggests that AML, similar to other malignant entities, employs a variety of mechanisms to evade immunosurveillance. In light of this, T-cell inhibitory myeloid-derived suppressor cells (MDSC) are gaining interest as key facilitators of immunoescape. Accumulation of CD14⁺HLA-DR^low monocytic MDSCs has been described in newly diagnosed AML patients, and deciphering the underlying mechanisms could help to improve anti-AML immunity. Here, we report that conventional monocytes readily take-up AML-derived extracellular vesicles (EV) and subsequently undergo MDSC differentiation. They acquired an CD14⁺HLA-DR^low phenotype, expressed the immunomodulatory indoleamine-2,3-dioxygenase, and upregulated expression of genes characteristic for MDSCs, such as S100A8/9 and cEBPβ. The Akt/mTOR pathway played a critical role in the AML-EV-induced phenotypical and functional transition of monocytes. Generated MDSCs displayed a glycolytic switch, which rendered them more susceptible toward glycolytic inhibitors. Furthermore, palmitoylated proteins on the AML-EV surface activated Toll-like receptor 2 as the initiating event of Akt/mTOR-dependent induction of MDSC. Therefore, targeting protein palmitoylation in AML blasts could block MDSC accumulation to improve immune responses. SIGNIFICANCE: These findings indicate that targeting protein palmitoylation in AML could interfere with the leukemogenic potential and block MDSC accumulation to improve immunity.

Innate extracellular vesicles from melanoma patients suppress β-catenin in tumor cells by miRNA-34a

Upon tumor development, new extracellular vesicles appear in circulation. Our knowledge of their relative abundance, function, and overall impact on cancer development is still preliminary. Here, we demonstrate that plasma extracellular vesicles (pEVs) of non-tumor origin are persistently increased in untreated and post-excision melanoma patients, exhibiting strong suppressive effects on the proliferation of tumor cells. Plasma vesicle numbers, miRNAs, and protein levels were elevated two- to tenfold and detected many years after tumor resection. The vesicles revealed individual and clinical stage-specific miRNA profiles as well as active ADAM10. However, whereas pEV from patients preventing tumor relapse down-regulated β-catenin and blocked tumor cell proliferation in an miR-34a-dependent manner, pEV from metastatic patients lost this ability and stimulated β-catenin-mediated transcription. Cancer-induced pEV may constitute an innate immune mechanism suppressing tumor cell activity including that of residual cancer cells present after primary surgery.

Tyrosine phosphorylation directs TACE into extracellular vesicles via unconventional secretion

When studying how HIV-1 Nef can promote packaging of the proinflammatory transmembrane protease TACE (tumor necrosis factor-α converting enzyme) into extracellular vesicles (EVs) we have revealed a novel tyrosine kinase-regulated unconventional protein secretion (UPS) pathway for TACE. When TACE was expressed without its trafficking cofactor iRhom allosteric Hck activation by Nef triggered translocation of TACE into EVs. This process was insensitive to blocking of classical secretion by inhibiting endoplasmic reticulum (ER) to Golgi transport, and involved a distinct form of TACE devoid of normal glycosylation and incompletely processed for prodomain removal. Like most other examples of UPS this process was Golgi reassembly stacking protein (GRASP)-dependent but was not associated with ER stress. These data indicate that Hck-activated UPS provides an alternative pathway for TACE secretion that can bypass iRhom-dependent ER to Golgi transfer, and suggest that tyrosine phosphorylation might have a more general role in regulating UPS.

Extracellular vesicles from mature dendritic cells (DC) differentiate monocytes into immature DC

Mature dendritic cells (DC) secrete substantial amounts of vesicles that are primarily ingested by monocytes, leading to differentiation processes in these target cells towards monocyte-derived DC.

During inflammation, murine and human monocytes can develop into dendritic cells (DC), but this process is not entirely understood. Here, we demonstrate that extracellular vesicles (EV) secreted by mature human DC (maDC) differentiate peripheral monocytes into immature DC, expressing a unique marker pattern, including 6-sulfo LacNAc (slan), Zbtb46, CD64, and CD14. While EV from both maDC and immature DC differentiated monocytes similar to GM-CSF/IL-4 stimulation, only maDC-EV produced precursors, which upon maturation stimulus developed into T-cell–activating and IL-12p70–secreting maDC. Mechanistically, maDC-EV induced cell signaling through GM-CSF, which was abundant in EV as were IL-4 and other cytokines and chemokines. When injected into the mouse skin, murine maDC-EV attracted immune cells including monocytes that developed activation markers typical for inflammatory cells. Skin-injected EV also reached lymph nodes, causing a similar immune cell infiltration. We conclude that DC-derived EV likely serve to perpetuate an immune reaction and may contribute to chronic inflammation.

Multiepitope tissue analysis reveals SPPL3-mediated ADAM10 activation as a key step in the transformation of melanocytes

The evolution of cancer is characterized by the appearance of specific mutations, but these mutations are translated into proteins that must cooperate to induce malignant transformation. Using a systemic approach with the multiepitope ligand cartography (MELC) technology, we analyzed protein expression profiles (PEPs) in nevi and BRAF^V600E-positive superficial spreading melanomas (SSMs) from patient tissues to identify key transformation events. The PEPs in nevi and SSMs differed predominantly in the abundance of specific antigens, but the PEPs of nevi- and melanoma-associated keratinocytes gradually changed during the transformation process. A stepwise change in PEP with similar properties occurred in keratinocytes cocultured with melanoma cells. Analysis of the individual steps indicated that activation of the metalloproteinase ADAM10 by signal peptide peptidase-like 3 (SPPL3) triggered by mutant BRAF^V600E was a critical transformation event. SPPL3-mediated ADAM10 activation involved the translocation of SPPL3 and ADAM10 into Rab4- or Rab27-positive endosomal compartments. This endosomal translocation, and hence ADAM10 activation, was inhibited by the presence of the tumor suppressor PTEN. Our findings suggest that systematic tissue antigen analysis could complement whole-genome approaches to provide more insight into cancer development.

Immunogenic and tolerogenic effects of the chimeric IL-2-diphtheria toxin cytocidal agent Ontak® on CD25+ cells

Ontak^®, a conjugate between IL-2 and a diphtheria toxin fragment, was recently investigated in cancer clinical trials aiming to kill CD25⁺ regulatory T cells (T_regs). We found that the activity of Ontak^® was more complex on T_regs and conventional T cells (T_convs) than anticipated, including a novel strong influence on dendritic cells (DCs).

HIV Nef, paxillin, and Pak1/2 regulate activation and secretion of TACE/ADAM10 proteases

The HIV Nef protein recruits the polycomb protein Eed and mimics an integrin receptor signal for reasons that are not entirely clear. Here we demonstrate that Nef and Eed complex with the integrin effector paxillin to recruit and activate TNFα converting enzyme (TACE alias ADAM 17) and its close relative ADAM10. The activated proteases cleaved proTNFα and were shuttled into extracellular vesicles (EVs). Peripheral blood mononuclear cells that ingested these EVs released TNFα. Analyzing the mechanism, we found that Pak2, an established host cell effector of Nef, phosphorylated paxillin on Ser272/274 to induce TACE-paxillin association and shuttling into EVs via lipid rafts. Conversely, Pak1 phosphorylated paxillin on Ser258, which inhibited TACE association and lipid raft transfer. Interestingly, melanoma cells used an identical mechanism to shuttle predominantly ADAM10 into EVs. We conclude that HIV-1 and cancer cells exploit a paxillin/integrin-controlled mechanism to release TACE/ADAM10-containing vesicles, ensuring better proliferation/growth conditions in their microenvironment.

Human dendritic cells efficiently phagocytose adenoviral oncolysate but require additional stimulation to mature

Oncolytic adenoviruses are emerging agents for treatment of cancer by tumor-restricted virus infection and cell lysis. Clinical trials have shown that oncolytic adenoviruses are well tolerated in patients but also that their antitumor activity needs improvement. A promising strategy toward this end is to trigger systemic and prolonged antitumor immunity by adenoviral oncolysis. Antitumor immune activation depends in large part on antigen presentation and T cell activation by dendritic cells (DCs). Thus, it is likely that the interaction of lysed tumor cells with DCs is a key determinant of such "oncolytic vaccination." Our study reveals that human DCs effectively phagocytose melanoma cells at late stages of oncolytic adenovirus infection, when the cells die showing preferentially features of necrotic cell death. Maturation, migration toward CCL19 and T cell stimulatory capacity of DCs, crucial steps for immune induction, were, however, not induced by phagocytosis of oncolysate, but could be triggered by a cytokine maturation cocktail. Therefore, oncolytic adenoviruses and adenoviral oncolysate did not block DC maturation, which is in contrast to reports for other oncolytic viruses. These results represent a rationale for inserting immunostimulatory genes into oncolytic adenovirus genomes to assure critical DC maturation. Indeed, we report here that adenoviral transduction of melanoma cells with CD40L during oncolysis triggers the maturation of human DCs with T cell stimulatory capacity similar to DCs matured by cytokines. We conclude that triggering and shaping DC-induced antitumor immunity by oncolytic adenoviruses "armed" with immunostimulatory genes holds promise for improving the therapeutic outcome of viral oncolysis in patients.

HIV-Nef and AIDS pathogenesis: are we barking up the wrong tree?

After two decades of research the Nef protein of human immunodeficiency virus (HIV) remains a mysterious protein with an indisputable role in HIV pathogenesis. The ability to downregulate CD4 and major histocompatibility complex class I (MHC-I) was the first ascribed function of Nef and, whereas the number of downmodulated receptors by Nef is rising, so are the explanations for how their downregulation could contribute to HIV pathogenesis. At the same time there is increasing evidence that Nef not only induces endocytosis but also exocytosis, namely of cytokines and microvesicles that contain Nef itself. Because endocytosis and exocytosis are connected events, this is not surprising - and raises the intriguing possibility that HIV aims at secretion rather than ingestion. Have we therefore barked up the wrong tree over the past two decades? In this opinion article I argue that Nef-induced secretion is most probably the pathogenesis-relevant function behind this elusive viral effector.

Massive secretion by T cells is caused by HIV Nef in infected cells and by Nef transfer to bystander cells

The HIV Nef protein mediates endocytosis of surface receptors that correlates with disease progression, but the link between this Nef function and HIV pathogenesis is not clear. Here, we report that Nef-mediated activation of membrane trafficking is bidirectional, connecting endocytosis with exocytosis as occurs in activated T cells. Nef expression induced an extensive secretory activity in infected and, surprisingly, also in noninfected T cells, leading to the massive release of microvesicle clusters, a phenotype observed in vitro and in 36%-87% of primary CD4 T cells from HIV-infected individuals. Consistent with exocytosis in noninfected cells, Nef is transferred to bystander cells upon cell-to-cell contact and subsequently induces secretion in an Erk1/2-dependent manner. Thus, HIV Nef alters membrane dynamics, mimicking those of activated T cells and causing a transfer of infected cell signaling (TOS) to bystander cells. This mechanism may help explain the detrimental effect on bystander cells seen in HIV infection.

Novel (n)PKC kinases phosphorylate Nef for increased HIV transcription, replication and perinuclear targeting

The N-terminus of the human immunodeficiency virus (HIV) pathogenicity factor Nef associates with a protein complex (NAKC for Nef-associated kinase complex) that contains at least two kinases: the tyrosine kinase Lck and a serine kinase activity which was found to phosphorylate Lck and the Nef N-terminus. Here we show that this serine kinase activity is mediated by members of the novel Protein Kinase C (nPKC) subfamily, PKCdelta and theta. Association with the Nef N-terminus was sufficient to activate PKC leading to phosphorylation of Nef in vitro on a conserved serine residue at position 6. Mutation of serine 6 or coexpression of a transdominant negative PKC mutant significantly reduced Nef-stimulated HIV transcription and replication in resting PBMC. When analyzing the molecular mechanisms, we found that mutating serine 6 moderately affected myristoylation of Nef and its association with Pak2 activity, whereas CD4 downmodulation was not inhibited. More interestingly, this mutation abolished the typical perinuclear localization of Nef in T cells. We conclude that the activation of nPKCs by Nef is required to increase viral replication/infectivity and direct the subcellular localization of Nef.

[Disseminated cryptococcosis as inaugural manifestation of AIDS]

Disseminated cryptococcal disease is typically seen in patients with HIV infection. We report here the evolution of a patient with disseminated cryptococcosis whose treatment failed after ten weeks of induction therapy with amphotericin B. This case illustrates the importance of careful initial evaluation, and close clinical follow-up of these patients who are at risk of developing other opportunistic infections and drug-related complications.

HIV-1 Nef Mimics an Integrin Receptor Signal that Recruits the Polycomb Group Protein Eed to the Plasma Membrane

The Nef protein of human and simian immunodeficiency virus (HIV/SIV) is believed to interfere with T cell activation signals by forming a signaling complex at the plasma membrane. Composition and function of the complex are not fully understood. Here we report that Nef recruits the Polycomb Group (PcG) protein Eed, so far known as a nuclear factor and repressor of transcription, to the membrane of cells. The Nef-induced translocation of Eed led to a potent stimulation of Tat-dependent HIV transcription, implying that Eed removal from the nucleus is required for optimal Tat function. Similar to Nef action, activation of integrin receptors recruited Eed to the plasma membrane, also leading to enhanced Tat/Nef-mediated transcription. Our results suggest a link between membrane-associated activation processes and transcriptional derepression and demonstrate how HIV exploits this mechanism.

Live and let die: Nef functions beyond HIV replication

The viral Nef protein is important for the progression of the human and simian immunodeficiency virus (HIV/SIV) infection. So far, experimental evidence has suggested that Nef enhances viral replication and infectivity through a combination of different effects. Recent insights, however, indicate that its functions are more complex than previously anticipated. By targeting the T cell receptor, Nef may not only prime viral replication but, more importantly, ensure viral survival through distinct mechanisms of immune evasion and antiapoptosis.

HIV-1 Nef associated PAK and PI3-kinases stimulate Akt-independent Bad-phosphorylation to induce anti-apoptotic signals

A highly conserved signaling property of Nef proteins encoded by human or simian immunodeficiency virus is the binding and activation of a PAK kinase whose function is unclear. Here we show that Nef-mediated p21-activated kinase (PAK) activation involves phosphatidylinositol 3-kinase, which acts upstream of PAK and is bound and activated by Nef similar to the manner of Polyoma virus middle T antigen. The Nef-associated phosphatidylinositol-3-PAK complex phosphorylated the pro-apoptotic Bad protein without involving the protein kinase B-Akt kinase, which is generally believed to inactivate Bad by serine phosphorylation. Consequently, Nef, but not a Nef mutant incapable of activating PAK, blocked apoptosis in T cells induced by serum starvation or HIV replication. Nef anti-apoptotic effects are likely a crucial mechanism for viral replication in the host and thus in AIDS pathogenesis.

A natural variability in the proline-rich motif of Nef modulates HIV-1 replication in primary T cells

In the infected host, the Nef protein of HIV/SIV is required for high viral loads and thus disease progression. Recent evidence indicates that Nef enhances replication in the T cell compartment after the virus is transmitted from dendritic cells (DC). The underlying mechanism, however, is not clear. Here, we report that a natural variability in the proline-rich motif (R71T) profoundly modulated Nef-stimulated viral replication in primary T cells of immature dendritic cell/T cell cocultures. Whereas both Nef variants (R/T-Nef) downregulated CD4, only the isoform supporting viral replication (R-Nef) efficiently interacted with signaling molecules of the T cell receptor (TCR) environment and stimulated cellular activation. Structural analysis suggested that the R to T conversion induces conformational changes, altering the flexibility of the loop containing the PxxP motif and hence its ability to bind cellular partners. Our report suggests that functionally and conformationally distinct Nef isoforms modulate HIV replication on the interaction level with the TCR-signaling environment once the virus enters the T cell compartment.

Nef from human immunodeficiency virus type 1(F12) inhibits viral production and infectivity

Human immunodeficiency virus type 1(F12) (HIV-1(F12)) interferes with the replication of other strains of HIV. Its accessory protein, Nef, is sufficient for this phenotype, where the production and infectivity of HIV are impaired significantly. The analysis of three rare mutations in this Nef protein revealed that these effects could be separated genetically. Moreover, the defect in virus production correlated with the lack of processing of the p55(Gag) precursor in the presence of Nef from HIV-1(F12). Importantly, the introduction of one of these mutations (E177G) into Nef from HIV-1(NL4-3) also created a dominant-negative Nef protein. Effects of Nef from HIV-1(F12) on virus production and Gag processing correlated with its altered subcellular distribution. Moreover, the association with two new cellular proteins with molecular masses of 74 and 75 kDa, which do not interact with other Nef proteins, correlated with the decreased virion infectivity. The identification of a dominant-negative protein for the production and infectivity of HIV suggests that Nef plays an active role at this stage of the viral replicative cycle.

Dynamic Nef and Nef dynamics: how structure could explain the complex activities of this small HIV protein

The Nef protein of the human immunodeficiency virus is as important for disease progression as it is perplexing in its plethora of target molecules and functions. In this article, it is proposed that the complex biology of Nef is regulated through conformational changes of the protein that are triggered by cellular location and specific interactions as Nef traffics through the infected cell.

Common germinal-center B-cell origin of the malignant cells in two composite lymphomas, involving classical Hodgkin's disease and either follicular lymphoma or B-CLL

BACKGROUND

Classical Hodgkin's disease (HD) and B-cell non-Hodgkin lymphoma (NHL) occasionally occur in the same patient. Such composite lymphomas represent interesting models to study the pathogenesis of B-cell lymphomas and the relationship between HD and B-cell NHL.

MATERIALS AND METHODS

We analyzed two composite lymphomas (a combination of classical HD with follicular lymphoma [FL] and a combination of classical HD with B-cell chronic lymphocytic leukemia [B-CLL]) by micromanipulation of single cells from tissue sections and amplification of immunoglobulin V region genes for the clonal relationship of the tumor cells.

RESULTS

In both cases, clonally related variable (V) genes with both shared as well as distinct somatic mutations were obtained from the two lymphomas, showing that in each of the cases the distinct tumor cells were members of a common germinal center (GC) B-cell clone. FL cells from two different lymph nodes of patient 1 showed a similar mutation pattern, suggesting that infiltration of these lymph nodes by tumor cells was not restricted to a particular FL cell or subclone. In the FL, a single cell was identified with a mutation signature indicating that premalignant cells can persist in the tissue.

CONCLUSIONS

The cases presented here further underline the close relationship between HD and B-cell NHL and the role of the GC in lymphomagenesis. Whereas the latter was already suggested for FL and HD, the present study indicates that also in the B-CLL subset characterized by mutated Ig genes, important steps in malignant transformation happen in the GC, and that HRS cells can derive from CD5-positive B cells.

Direct in vitro binding of full-length human immunodeficiency virus type 1 Nef protein to CD4 cytoplasmic domain

The Nef protein of the simian and human immunodeficiency viruses is known to directly bind and downregulate the CD4 receptor. Although the molecular mechanism is well understood, direct binding of Nef and CD4 is difficult to demonstrate and is believed to be of low affinity. Applying nuclear magnetic resonance and fluorescence spectroscopy, we biophysically reevaluated the CD4-Nef complex and found the dissociation constant to be in the submicromolar range. We conclude that additional, so far disregarded residues in the N terminus of Nef are important for interaction with CD4.

Functional and structural defects in HIV type 1 nef genes derived from pediatric long-term survivors

DNA sequences and three distinct in vitro functions of Nef were evaluated in a group of seven perinatally infected children. nef gene sequences obtained before and after virus culture showed that one of the five non-/slow progressors harbored a virus with large deletions. nef genes from the remaining four children were full length but contained discrete changes at a higher frequency than the rapid progressors. In functional studies, 40 of 44 Nef proteins derived from the whole study group were capable of binding the cellular serine kinase p62, indicating that this function is well conserved among naturally occurring viruses. In contrast, representative Nef proteins derived from the long-term non-/slow progressors were found to be defective or far less capable of enhancing viral replication and/or viral infectivity in herpesvirus saimiri-transformed human T cells and peripheral blood mononuclear cells. On reversion of highly prevalent point mutations in the defective proteins, viral replication could be restored to wild-type levels. Our results suggest that nef genes derived from pediatric long-term nonprogressors have gross deletions in isolated cases but a higher prevalence of discrete changes that may impair Nef function in primary T cell assays, but not all functions reported for Nef.

CD34/QBEND10 immunostaining in bone marrow biopsies: an additional parameter for the diagnosis and classification of myelodysplastic syndromes

CD34/QBEND10 immunostaining has been assessed in 150 bone marrow biopsies (BMB) including 91 myelodysplastic syndromes (MDS), 16 MDS-related AML, 25 reactive BMB, and 18 cases where RA could neither be established nor ruled out. All cases were reviewed and classified according to the clinical and morphological FAB criteria. The percentage of CD34-positive (CD34 +) hematopoietic cells and the number of clusters of CD34+ cells in 10 HPF were determined. In most cases the CD34+ cell count was similar to the blast percentage determined morphologically. In RA, however, not only typical blasts but also less immature hemopoietic cells lying morphologically between blasts and promyelocytes were stained with CD34. The CD34+ cell count and cluster values were significantly higher in RA than in BMB with reactive changes (p<0.0001 for both), in RAEB than in RA (p=0.0006 and p=0.0189, respectively), in RAEBt than in RAEB (p=0.0001 and p=0.0038), and in MDS-AML than in RAEBt (p<0.0001 and p=0.0007). Presence of CD34+ cell clusters in RA correlated with increased risk of progression of the disease. We conclude that CD34 immunostaining in BMB is a useful tool for distinguishing RA from other anemias, assessing blast percentage in MDS cases, classifying them according to FAB, and following their evolution.

Rare occurrence of classical Hodgkin's disease as a T cell lymphoma

Recent work identified Hodgkin and Reed-Sternberg (H/RS) cells in classical Hodgkin's disease (cHD) as clonal progeny of mature B cells. Therefore, it is generally assumed that cHD homogenously represents a B cell lymphoma. In a subset of cHD, however, H/RS cells expressing T cell-associated proteins may be candidates for alternative lineage derivation. Single H/RS cells with cytotoxic T cell phenotype were micromanipulated from three cases of cHD and analyzed by single cell polymerase chain reaction for immunoglobulin heavy (IgH) and light chain (IgL) gene rearrangements, T cell receptor (TCR)-beta gene rearrangements, and germline configuration of the IgH and TCR-beta loci. H/RS cells from two cases of cHD harbored clonal, somatically mutated Ig gene rearrangements, whereas TCR-beta loci were in germline configuration. In contrast, H/RS cells from an additional case harbored clonal TCR-beta variable/diversity/joining (VDJ) and DJ gene rearrangements, whereas the IgH locus was in germline configuration on both alleles. Thus, in two cases of cHD with H/RS cells expressing cytotoxic T cell molecules, the tumor cells are derived from mature B cells that aberrantly express T cell markers. In a third case, however, H/RS cells were derived from a T cell, demonstrating that cHD can also occur as a T cell lymphoma.

Frequent methylation silencing of p15(INK4b) (MTS2) and p16(INK4a) (MTS1) in B-cell and T-cell lymphomas

The methylation status of p15(INK4b) (MTS2), p16(INK4a) (MTS1) and p14(ARF) (p16beta) was analyzed in 56 lymphomas by restriction-enzyme related polymerase chain reaction (PCR) (REP), methylation-specific PCR (MSP), and bisulfite genomic sequencing (BGS). Methylation of the p15 and p16 genes was detected, respectively, in 64% and 32% of the B-cell lymphomas, in 44% and 22% of the T-cell lymphomas, and in none of the 5 reactive lymph nodes analyzed. Both p15 and p16 genes were methylated more often in the high-grade (78% and 50%, respectively) than in the low-grade B-cell lymphomas (55% and 21%, respectively). For 5 cases, mapping of the methylated CpGs of the p16 promoter region confirmed the results of REP and MSP. In addition, a large variation in the methylation patterns of p16 exon 1 was observed, not only from one lymphoma to another, but also within a given tumor. Methylation of p15 and p16 was associated with an absence of gene expression, as assessed by reverse transcription-PCR. The p14 gene was unmethylated and normally expressed in all 56 tumors. We found no mutations of p15, p16, or p14 in any of the 56 lymphomas. Our results suggest a role for p15 and p16 gene methylation during lymphomagenesis and a possible association between p15 and p16 inactivation and aggressive transformation in B-cell and T-cell lymphomas.

Induction of Fas ligand expression by HIV involves the interaction of Nef with the T cell receptor zeta chain

During HIV/SIV infection, there is widespread programmed cell death in infected and, perhaps more importantly, uninfected cells. Much of this apoptosis is mediated by Fas-Fas ligand (FasL) interactions. Previously we demonstrated in macaques that induction of FasL expression and apoptotic cell death of both CD4(+) and CD8(+) T cells by SIV is dependent on a functional nef gene. However, the molecular mechanism whereby HIV-1 induces the expression of FasL remained poorly understood. Here we report a direct association of HIV-1 Nef with the zeta chain of the T cell receptor (TCR) complex and the requirement of both proteins for HIV-mediated upregulation of FasL. Expression of FasL through Nef depended upon the integrity of the immunoreceptor tyrosine-based activation motifs (ITAMs) of the TCR zeta chain. Conformation for the importance of zeta for Nef-mediated signaling in T cells came from an independent finding. A single ITAM motif of zeta but not CD3epsilon was both required and sufficient to promote activation and binding of the Nef-associated kinase (NAK/p62). Our data imply that Nef can form a signaling complex with the TCR, which bypasses the requirement of antigen to initiate T cell activation and subsequently upregulation of FasL expression. Thus, our study may provide critical insights into the molecular mechanism whereby the HIV-1 accessory protein Nef contributes to the pathogenesis of HIV.

Chromosomal abnormalities in renal cell neoplasms associated with acquired renal cystic disease. A series studied by comparative genomic hybridization and fluorescence in situ hybridization

Sporadic renal cell carcinomas (RCCs) display different chromosomal abnormalities according to their morphology; gains of chromosomes 7 and 17 and loss of Y are commonly observed in papillary lesions, whereas loss of 3p sequences and multiple losses of specific chromosomes are found in non-papillary and chromophobe cell carcinomas, respectively. Acquired renal cystic disease (ARCD) is associated with an increased incidence of renal cell tumours, especially papillary lesions. The aim of this study was to examine a series of ARCD-related tumours for chromosomal abnormalities and to compare the findings with those abnormalities commonly observed in sporadic RCCs. Nine tumours from four patients with ARCD were examined using comparative genomic hybridization (CGH) and interphase cytogenetics. Gain of chromosomes 7 and 17 was observed in all four papillary lesions and loss of Y in three. In addition, gain of chromosome 16 was observed in three papillary tumours. Three chromophobe RCCs originating from the same kidney showed different genomic profiles; two had no abnormalities, whereas one showed loss of chromosome 17p. Two non-papillary RCCs failed to show chromosome 3p alterations. In conclusion, renal cell tumours developing in ARCD may show chromosomal abnormalities both similar to and different from those seen in sporadic tumours.

Prognostic value of follicular dendritic cells in nodular sclerosing Hodgkin's disease

AIMS

In nodular sclerosing Hodgkin's disease (NSHD), the prognostic relevance of the histopathological grading in two subtypes NSI (low-grade) and NSII (high-grade) remains controversial. Analysis of follicular dendritic cells (FDC) may provide new prognostic parameters.

METHODS AND RESULTS

Tumours from 59 patients with NSHD were studied. Mean follow-up time was 8 years. Forty-one cases were classified as NSI and 18 as NSII. FDC were immunostained with the paraffin-resistant monoclonal antibodies CD21 and CNA.42. We distinguished three patterns in the neoplastic tissue: FDC1, the presence of well-defined follicle-like structures (n = 20); FDC2, the presence of largely destroyed FDC networks (n = 25); and FDC3, no or a few isolated FDC (n = 14). The three groups differed clearly regarding the frequency of relapse and the survival. The longest survival was seen in the FDC1 group, the shortest in the FDC3 group, the FDC2 group being intermediate (P = 0.0025). FDC status was a discriminating prognostic factor for all patients, and within various age and stage categories. Combining the FDC status and the NSI-NSII grading defined the best survival group as FDC1-NSI.

CONCLUSIONS

Assessment of FDC pattern, associated with histological subtyping, brings valuable data for predicting survival and outcome in NSHD.

The N-terminus of Nef from HIV-1/SIV associates with a protein complex containing Lck and a serine kinase

The Nef protein of human and primate lentiviruses is a key factor in HIV/SIV pathogenesis. Here we report that Nef associates with two different kinases, forming a multiprotein complex at the far N-terminus of the viral protein. One of the kinases was identified as Lck, whereas the second protein was found to be a serine kinase that phosphorylated Nef and Lck in vitro and could be discriminated from the serine kinase identified previously. The Nef-associated kinase complex (NAKC) was demonstrated in COS cells, in HIV-infected cells, and in vitro using recombinant Lck and Nef proteins. Deletion of a short amphipathic alpha-helix in the N-terminus, which was found to be conserved in all Nef proteins, inhibited association of the NAKC and significantly reduced virion infectivity.

Follicular dendritic cells in bone marrow lymphoproliferative diseases: an immunohistochemical study including a new paraffin-resistant monoclonal antibody, DR53

Two-hundred and twenty-one bone marrow biopsies with lymphoid infiltrates were studied histologically and immunohistochemically, to assess the incidence and the pattern of follicular dendritic cells. Three monoclonal antibodies selective for follicular dendritic cells were used: CD21, CD35 and DR53, all reactive on paraffin-embedded material. Follicular dendritic cells were present in two of 38 benign lymphoid aggregates, 92 of 134 low grade B-cell lymphomas (45 of 62 lymphocytic, 16 of 27 lymphoplasmacytoid, 0 of six hairy cell leukaemias, five of six centrocytic, 19 of 21 centroblastic-centrocytic, seven of 12 low grade NOS), one of 23 high grade B-cell lymphomas, 0 of 10 T-cell lymphomas, 0 of three Hodgkin's disease and four of 13 suspicious infiltrates. Follicular dendritic cells were found in lymphomatous involvement with nodular, patchy and massive growth pattern, but not in interstitial ones. They formed follicle-like networks, whose number and size were directly correlated to the tumour mass. The origin and frequency distribution of follicular dendritic cells in bone marrow biopsy lymphomas is discussed and the diagnostic relevance of follicular dendritic cell immunostaining in routine bone marrow biopsy lymphoid infiltrates is assessed.

A conserved domain and membrane targeting of Nef from HIV and SIV are required for association with a cellular serine kinase activity

Among the primate lentiviruses (human immunodeficiency virus (HIV) -1, HIV-2, and simian immunodeficiency virus (SIV), the nef gene is highly conserved and encodes a myristylated protein of approximately 27 kDa (HIV-1) or approximately 34 kDa (HIV-2, SIV). Previously, we found Nef expressed either as a CD8-Nef fusion protein or as a native protein in virally infected T cell lines associates with a cellular serine kinase. This kinase activity phosphorylated two proteins of 62 and 72 kDa that coimmunoprecipitate with Nef in in vitro kinase assays. Using transient expression, various Nef alleles and mutants have been analyzed for association with the cellular kinase activity. The ability of Nef to associate with the kinase activity is conserved among several alleles of HIV-1 as well as SIVmac239 and is observed in non-lymphoid cell lines of simian and murine origins. Two separate regions of HIV-1SF2 Nef are critical for the associated kinase activity. One domain overlaps with a central highly conserved region found in all primate lentivirus nef genes and has been provisionally mapped to amino acids 45-127. Because membrane localization of Nef is important for the associated cellular kinase activity, the second domain represents a membrane targeting signal. Moreover, point mutations within the central region that abrogate the Nef-associated kinase activity in HIV-1SF2 Nef have the same effect when introduced into SIVmac239open Nef.

HIV-1 Nef leads to inhibition or activation of T cells depending on its intracellular localization

Nef of primate lentiviruses is required for viremia and progression to AIDS in monkeys. Negative, positive, and no effects of Nef have also been reported on viral replication in cells. To reconcile these observations, we expressed a hybrid CD8-Nef protein in Jurkat cells. Two opposite phenotypes were found, which depended on the intracellular localization of Nef. Expressed in the cytoplasm or on the cell surface, the chimera inhibited or activated early signaling events from the T cell antigen receptor. Activated Jurkat cells died by apoptosis, and only cells with mutated nef genes expressing truncated Nefs survived, which rendered Nef nonfunctional. These mutations paralleled those in other viral strains passaged in vitro. Not only do these positional effects of Nef reconcile diverse phenotypes of Nef and suggest a role for its N-terminal myristylation, but they also explain effects of Nef in HIV infection and progression to AIDS.