Clinical value of R-spondins in triple-negative and metaplastic breast cancers

Background:

RSPO ligands, activators of the Wnt/β-catenin pathway, are overexpressed in different cancers. The objective of this study was to investigate the role of RSPOs in breast cancer (BC).

Methods:

Expression of RSPO and markers of various cancer pathways were measured in breast tumours and cell lines by qRT–PCR. The effect of RSPO on the Wnt/β-catenin pathway activity was determined by luciferase assay, western blotting, and qRT–PCR. The effect of RSPO2 inhibition on proliferation was determined by using RSPO2 siRNAs. The effect of IWR-1, an inhibitor of the Wnt/β-catenin pathway, was examined on the growth of an RSPO2-positive patient-derived xenograft (PDX) model of metaplastic triple-negative BC.

Results:

We detected RSPO2 and RSPO4 overexpression levels in BC, particularly in triple-negative BC (TNBC), metaplastic BC, and triple-negative cell lines. Various mechanisms could account for this overexpression: presence of fusion transcripts involving RSPO, and amplification or hypomethylation of RSPO genes. Patients with RSPO2-overexpressing tumours have a poorer metastasis-free survival (P=3.6 × 10⁻⁴). RSPO2 and RSPO4 stimulate Wnt/β-catenin pathway activity. Inhibition of RSPO expression in a TN cell line inhibits cell growth, and IWR-1 significantly inhibits the growth of an RSPO2-overexpressing PDX.

Conclusions:

RSPO overexpression could therefore be a new prognostic biomarker and therapeutic target for TNBC.

Do Transcriptomic Markers Provide Significant and Stable Information in Addition to Standard Markers, for the Prediction of Pathological Complete Response in Breast Cancer?

Background: The aim of this study was to investigate and quantify the contribution of transcriptomic markers, in addition to strong predictors such as oestrogen receptor status, to the prediction of pathological complete response (pCR) in locally advanced breast cancer.Patients: The RNA profiles were analyzed using U133 plus 2.0 Affymetrix. We included 189 patients out of 340 patients entered in a neoadjuvant chemotherapy trial for large operable and locally advanced breast cancer. After four cycles of epirubicin–cyclophosphamide, patients were randomly allocated to four cycles of docetaxel with or without celecoxib for patients with HER2-negative tumors, and docetaxel with or without trastuzumab for patients with HER2-positive tumors, respectively. Proportions of pCR in each group were equal to 0.12, 0.16, 0.15 and 0.24 respectively. Patients who received trastuzumab (N=36) were discard from our example, in order to deal with similar proportions of pCR.Methods: The whole sample was divided into a training set (N=81) and a validation set (N=72). Using the training set, two predictive models were built using multivariate logistic regression models. In the first model (M1), usual clinical and biological significant markers were included. In the second model (M2), in addition to the significant parameters of M1, significant transcriptomic variables were included. Diagnostics of both predictive models were assessed on the validation set through sensitivity and specificity estimates. Simulations were performed to investigate stability of model M2.Results: In M1, oestrogen receptor status and tumor size were found to have a strong predictive role in the prediction of pCR. In addition to these classical markers, genes belonging to biological pathways involved in proliferation and microtubule stabilization appeared to have a strong role in the prediction of pCR (model M2). Validation of M1 on the validation set provided 70% of sensitivity and 86% of specificity. Validation of M2 on the validation set yielded to a better sensitivity of 80% and a specificity of 81%. Using simulations, we showed that several different predictive models M2 yielded to similar performances on the validation set. Conclusion: Our study showed that transcriptomic markers provided significant information in addition to usual biological markers for the prediction of pCR. In addition, predictive model with both usual and transcriptomic markers may lead in an improvement of the classification performances. However, as illustrated by simulations, predictive models with both classical and transcriptomic markers are not exclusive. The contribution of transcriptomic data for the prediction of pCR is straightforward, but finding a stable predictive model remains a great challenge.Supported by PHRC AOM/2OO2/02117, Pfizer inc., Roche, sanofi-aventis.ISRCTN10059974

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2035.

A genomic and transcriptomic approach to distinguish primary and metastatic ovary tumors

e22150

Background: Distinction of primary ovarian tumors from metastatic tumors involving the ovary is in some cases challenging for final pathologic diagnosis and for treatment with efficient chemotherapy Methods: We gathered from our biobank 16 pairs of breast/ovarian tumors for some of which the diagnosis was uncertain. We investigated the possibility to improve diagnosis using genomic and transcriptomic tools. The pangenomic profiles of 16 pairs of primary breast carcinoma and ovary tumors (primary tumors or metastases from breast carcinoma) from the same patients were analyzed using the Affymetrix GeneChip Mapping 50K (XbaI) SNP arrays. The data were normalized with ITALICS algorithm. We analyzed the transcriptome of the paired samples using Affymetrix U133plus2 arrays. The data were normalized with GCRMA algorithm and a hierarchical clustering of these samples was performed, together with a dataset of primary and secondary ovary tumors. Results: Primary infiltrating lobular carcinoma (ILC) was observed in 6 patients, infiltrating ductal carcinoma (IDC) in 7 patients, 1 patient had one ILC and one IDC, 1 patient had a mixed IDC+ILC and 1 patient an undifferentiated cancer. All patients received adequate loco-regional and systemic therapies. Median time to diagnosis of ovarian tumor was 54 months. Ovarian tumors were considered as primary in 7 patients, and metastatic in 9 patients, and diagnosis was ambiguous in 4 of them. Four patients developed extra-abdominal metastases. Median survival from breast cancer diagnosis was 78 months, and from ovarian tumor diagnosis was 29 months. CGH array: In 12 pairs, the comparison of genomic profiles one with each other, confirmed the pathological characteristics of the tumors. In 4 cases, the genomic profiles established clearly the status of the ovary tumor whereas the pathological analysis did not. Transcriptome: The status established by the transcriptomic analysis was for each sample in total agreement with the status established by the genomic analysis. Conclusions: We clearly established in this training series that CGH array analysis could help to discriminate between primary and secondary ovarian tumors from breast cancer. Transcriptomic data confirmed these results. Further validation data are warranted.

No significant financial relationships to disclose.

Identification of three-genomic regions prognostic signature in small node-negative breast carcinomas

Abstract #1081

Background: The purpose of this study was to identify a genomic signature of early metastatic recurrence, in order to predict accurately breast carcinomas clinical outcome and to select patients with node negative and small tumor size (<3cm) who would benefit from adjuvant chemotherapy.
 Patients and methods: Using genome-wide BAC-PAC Genomic Comparative Hybridization (CGH) array (1kb), we analyzed a training set of 78 patients. All patients had invasive ductal carcinomas and were initially treated by surgery and radiotherapy, without chemotherapy. The validation was performed on an independent test set of 90 patients. The training and tests sets were composed of respectively 53 and 58 patients disease-free survivors at 60 months (good prognosis group), and by 25 and 32 patients with distant metastatic recurrence before 48 months (poor prognosis group). In the training set, a signature was established as a logistic multivariate model of regions containing contiguous BAC clones with statistically different ratios and median frequencies of gains and losses between the poor and the good prognosis groups. This signature was then validated using the independent test set to evaluate its accuracy to classify T0T1T2N0 patients according to their outcome.
 Results: The training test identified a prognostic signature defined by 3 genomic regions, located on the 2p (38.3 to 40.9Mb), 3p (32 to 80.3Mb), and 8q (78.8 to 128.9Mb) chromosomes. In the test set, 90% of patients of favourable outcome were ER +ve and 88% were PR +ve, compared to 62% and 55% in the poor outcome group, respectively. In the test set, our signature was highly informative to identify patients that developed distant metastases before 48 months: the rate of patients well classified was 0.74, CI (95%): [0.64; 0.83], with a specificity of 95%, CI (95%): [86%; 99%]. On Kaplan-Meier analysis, the poor-prognosis genomic signature group of patients had a RR of 3.5 of metastatic relapse (log rank test p<0.001).
 Conclusions: Our signature, validated on an independent series of small T0T1T2N0 and on a majority of ER/PR positive tumors, may provide a robust and accurate tool to identify, in addition to classical parameters, patients who would benefit from adjuvant medical treatments. The comparison of this genomic signature with RNA based signatures and clinico-pathological parameters, is currently being investigated.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1081.

Identification of genes regulated during osteoblastic differentiation by genome-wide expression analysis of mouse calvaria primary osteoblasts in vitro

Although several independent studies of gene expression patterns during osteoblast differentiation in cultures from calvaria and other in vitro models have been reported, only a small portion of the mRNAs expressed in osteoblasts have been characterized. We have previously analyzed the behavior of several known markers in osteoblasts, using Affymetrix GeneChip murine probe arrays (27,000 genes). In the present study we report larger groups of transcripts displaying significant expression modulation during the culture of osteoblasts isolated from mice calvaria. The expression profiles of 601 such regulated genes, classified in distinct functional families, are presented and analyzed here. Although some of these genes have previously been shown to play important roles in bone biology, the large majority of them have never been demonstrated to be regulated during osteoblast differentiation. Despite the fact that the precise involvement of these genes in osteoblast differentiation and function needs to be evaluated, the data presented herein will aid in the identification of genes that play a significant role in osteoblasts. This will provide a better understanding of the regulation of osteoblast differentiation and maturation.

Behavior of osteoblast, adipocyte, and myoblast markers in genome-wide expression analysis of mouse calvaria primary osteoblasts in vitro

Several genes, such as alkaline phosphatase, osteocalcin, and Cbfa1/Osf2, are known to be regulated during osteoblastic differentiation and are commonly used as "osteoblast markers" for in vitro or in vivo studies. The number of these genes is very limited, however, and it is of major interest to identify new genes that are activated or repressed during the process of osteoblast differentiation and bone formation as well as to extend the available information on gene families relevant to this particular differentiation pathway. To identify such genes, we have implemented a genome-wide analysis by determining changes in expression levels of 27,000 genes during in vitro differentiation of primary osteoblasts isolated from mouse calvaria. This study focuses on the description of the analytical and filtering process applied; on the transcriptional analysis of well-established "bone," "adipocyte," and "muscle" pathway markers; and on a description of the regulation profiles for genes recently described in the Skeletal Gene Database. We also demonstrate that new array technologies constitute reliable and powerful tools to monitor the transcription of genes involved in osteoblastic differentiation, allowing a more integrated vision of the biological pathways regulated during osteoblast commitment, differentiation, and function.

LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development

In humans, low peak bone mass is a significant risk factor for osteoporosis. We report that LRP5, encoding the low-density lipoprotein receptor-related protein 5, affects bone mass accrual during growth. Mutations in LRP5 cause the autosomal recessive disorder osteoporosis-pseudoglioma syndrome (OPPG). We find that OPPG carriers have reduced bone mass when compared to age- and gender-matched controls. We demonstrate LRP5 expression by osteoblasts in situ and show that LRP5 can transduce Wnt signaling in vitro via the canonical pathway. We further show that a mutant-secreted form of LRP5 can reduce bone thickness in mouse calvarial explant cultures. These data indicate that Wnt-mediated signaling via LRP5 affects bone accrual during growth and is important for the establishment of peak bone mass.

1-(5-oxohexyl)-3,7-Dimethylxanthine, a phosphodiesterase inhibitor, activates MAPK cascades and promotes osteoblast differentiation by a mechanism independent of PKA activation (pentoxifylline promotes osteoblast differentiation)

We have investigated the effect of 1-(5-oxohexyl)-3,7-dimethylxanthine or pentoxifylline (PeTx), a nonselective phosphodiesterase inhibitor, on osteoblastic differentiation in vitro by using two mesenchymal cell lines, C3H10T1/2 and C2C12, which are able to acquire the osteoblastic phenotype in the presence of bone morphogenetic protein-2 (BMP-2). PeTx induced the osteoblastic markers, osteocalcin and Osf2/Cbfa1, in C3H10T1/2 and C2C12 cells and enhanced BMP-2-induced expression of osteocalcin, Osf2/Cbfa1, and alkaline phosphatase. This activity was partially attributed to the fact that PeTx is able to enhance BMP-2-induced Smad1 transcriptional activity. Although PeTx clearly stimulates PKA in these cells, neither pretreatment of cells with the PKA inhibitor H89 nor transfection with the specific PKA inhibitor PKI prevented the induction or enhancement of osteoblast markers by PeTx, demonstrating that these effects were independent of PKA activation. On the other hand, PeTx induced the activation of ERK1/2 and p38 kinase pathways independently of the activation of PKA. Selective inhibitors of these MAPK cascades prevented the induction of osteoblastic markers in cells treated with PeTx, suggesting that the activation of these two pathways plays a role in the effect of PeTx on osteoblastic differentiation.

Opposite effects of bone morphogenetic protein-2 and transforming growth factor-beta1 on osteoblast differentiation

Several members of the transforming growth factor-beta (TGF-beta) superfamily have been demonstrated to play regulatory roles in osteoblast differentiation and maturation, but the mechanisms by which they act on different cells at different developmental stages remain largely unknown. We studied the effects of TGF-beta1 and bone morphogenetic protein-2 (BMP-2) on the differentiation/maturation of osteoblasts using the murine cell lines MC3T3-E1 and C3H10T1/2. BMP-2 induced or enhanced the expression of the osteoblast differentiation markers alkaline phosphatase (ALP) and osteocalcin (OC) in both cells. In contrast, TGF-beta1 was not only unable to induce these markers, but it dramatically inhibited BMP-2-mediated OC gene expression and ALP activity. In addition, TGF-beta1 inhibited the ability of BMP-2 to induce MC3T3-E1 mineralization. TGF-beta1 did not sensibly modify the increase of Osf2/Cbfa1 gene expression mediated by BMP-2, thus demonstrating that the inhibitory effect of TGF-beta1 on osteoblast differentiation/maturation mediated by BMP-2 was independent of Osf2/Cbfa1 gene expression. Finally, it is shown that TGF-beta1 does not affect BMP-2-induced Smad1 transcriptional activity in the mesenchymal pluripotent cells studied herein. Our data indicate that in vitro BMP-2 and TGF-beta1 exert opposite effects on osteoblast differentiation and maturation.

Sonic hedgehog increases the commitment of pluripotent mesenchymal cells into the osteoblastic lineage and abolishes adipocytic differentiation

The proteins of the hedgehog (Hh) family regulate various aspects of development. Recently, members of this family have been shown to regulate skeletal formation in vertebrates and to control both chondrocyte and osteoblast differentiation. In the present study, we analyzed the effect of Sonic hedgehog (Shh) on the osteoblastic and adipocytic commitment/differentiation. Recombinant N-terminal Shh (N-Shh) significantly increased the percentage of both the pluripotent mesenchymal cell lines C3H10T1/2 and ST2 and calvaria cells responding to bone morphogenetic protein 2 (BMP-2), in terms of osteoblast commitment as assessed by measuring alkaline phosphatase (ALP) activity. This synergistic effect was mediated, at least partly, through the positive modulation of the transcriptional output of BMPs via Smad signaling. Furthermore, N-Shh was found to abolish adipocytic differentiation of C3H10T1/2 cells both in the presence or absence of BMP-2. A short treatment with N-Shh was sufficient to dramatically reduce the levels of the adipocytic-related transcription factors C/EBPα and PPARγ in both C3H10T1/2 and calvaria cell cultures. Given the inverse relationship between marrow adipocytes and osteoblasts with aging, agonists of the Hh signaling pathway might constitute potential drugs for preventing and/or treating osteopenic disorders.

Activation of mitogen-activated protein kinase cascades is involved in regulation of bone morphogenetic protein-2-induced osteoblast differentiation in pluripotent C2C12 cells

Bone morphogenetic protein (BMP)-2, a member of the transforming growth factor-beta (TGF-beta) superfamily, is able to induce osteoblastic differentiation of C2C12 cells. Both Smad and mitogen-activated protein kinase (MAPK) pathways are essential components of the TGF-beta superfamily signaling machinery. Although Smads have been demonstrated to participate in the BMP-2-induced osteoblastic differentiation of C2C12 cells, the role of MAPK has not been addressed. This report shows that BMP-2 activates ERK and p38, but not JNK, in C2C12 cells. Pretreatment of cells with the p38 inhibitor, SB203580, dramatically reduced BMP-2-induced expression of the osteoblast markers alkaline phosphatase (ALP) and osteocalcin (OC). Nevertheless, overexpression of MKK3, a protein kinase that phosphorylates and activates p38, failed to induce ALP or OC expression in the absence of BMP-2, indicating that p38 activation is necessary but not sufficient for the acquisition of the osteoblast phenotype by these cells. Although ALP induction was increased slightly in the presence of PD-98059, a selective inhibitor of the ERK cascade, this compound significantly inhibited both steady-state and BMP-2-induced OC RNA levels. Our results indicate that p38 and ERK cascades play a crucial role in the osteoblast differentiation of C2C12 cells mediated by BMP-2.

Smad7 inhibits the survival nuclear factor kappaB and potentiates apoptosis in epithelial cells

In this study, we examined the effect of the stable expression of Smad7 in two different cell lines on apoptosis induced by various stimuli including TGF-beta, serum withdrawal, loss of cell adhesion (anoikis) and TNF-alpha. Smad7 increased TGF-beta-mediated apoptosis in Mv1Lu cells as well as anoikis and/or serum withdrawal-induced apoptosis in Mv1Lu and MDCK cells. Smad7 markedly decreased the activity of the survival NF-kappaB transcription factor in MDCK cells. Interestingly, the stable expression of oncogenic Ras in MDCK cells which suppressed Smad7 inhibition of NF-kappaB also suppressed Smad7 potentiation of serum withdrawal-induced apoptosis and anoikis. In addition, Smad7 inhibited TNF-alpha stimulation of NF-kappaB and increased TNF-alpha-mediated apoptosis in MDCK cells. Our results provide the first evidence that Smad7 induces sensitization of cells to different forms of cell death. They moreover demonstrate that Smad7 inhibits the survival NF-kappaB factor, providing a potential mechanism whereby Smad7 potentiates cell death.

Involvement of small GTPases in Mycoplasma fermentans membrane lipoproteins-mediated activation of macrophages

Mycoplasma fermentans lipoproteins (LAMPf) are capable of activating macrophages and inducing the secretion of proinflammatory cytokines. We have recently reported that mitogen-activated protein kinase (MAPK) pathways and NF-kappaB and activated protein 1 (AP-1) play a crucial role in the activation induced by this bacterial compound. To further elucidate the mechanisms by which LAMPf mediate the activation of macrophages, we assessed the effects of inhibiting small G proteins Rac, Cdc42, and Rho. The Rho-specific inhibitor C3 enzyme completely abolished the secretion of tumor necrosis factor alpha by macrophages stimulated with LAMPf and also inhibited the activation of extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK), and p38 kinase. In addition, we have shown that LAMPf stimulate Cdc42 and that inhibition of Cdc42 or Rac by dominant negative mutants abrogates LAMPf-mediated activation of JNK and transactivation of NF-kappaB and AP-1 in the murine macrophage cell line RAW 264.7. These results indicate that small G proteins Rho, Cdc42, and Rac are involved in the cascade of events leading to the macrophage activation by mycoplasma lipoproteins.

Signal transduction pathways involved in the activation of NF-kappa B, AP-1, and c-fos by Mycoplasma fermentans membrane lipoproteins in macrophages

Mycoplasma fermentans-derived membrane lipoproteins (LAMPf) have been demonstrated to stimulate monocytic cells and to induce the secretion of proinflammatory cytokines by a mechanism involving the triggering of protein tyrosine kinase and mitogen-activated protein kinase cascades. Herein, we have examined the effects of LAMPf on the activation of a series of transcription factors potentially involved in cytokine gene expression. LAMPf was capable of inducing NF-kappa B, activated protein 1 (AP-1), and c-fos activation in macrophages and of stimulating NF-kappa B and AP-1 transactivation. Furthermore, we have delineated the contribution of each mitogen-activated protein kinase pathway to the LAMPf-mediated activation of AP-1, c-fos, and NF-kappa B. Whereas the selective extracellular signal-regulated kinase pathway inhibitor PD-98059 did not affect the LAMPf-mediated transactivation of AP-1, c-fos, or NF-kappa B, the specific p38 inhibitor SB203580 abrogated this activity. A c-Jun N-terminal kinase-dominant negative was shown to block the activation of AP-1 without altering NF-kappa B or c-fos activation by LAMPf. In addition, D609, a selective inhibitor of phosphatidylcholine-specific phospholipase C, was shown to block both translocation and transactivation of either NF-kappa B or AP-1 in response to LAMPf. Although LAMPf-mediated macrophage activation is CD14 independent, we could not distinguish between the intracellular mechanisms leading to the macrophage activation triggered by either LPS or LAMPf. This suggests that macrophages display a common signaling machinery leading to the secretion of proinflammatory cytokines in response to different bacterial products. The comprehension of these mechanisms may help to better understanding the bacterial pathogenesis and to elucidate general mechanisms of macrophage activation leading to cytokine secretion.

Involvement of mitogen-activated protein kinase pathways in interleukin-8 production by human monocytes and polymorphonuclear cells stimulated with lipopolysaccharide or Mycoplasma fermentans membrane lipoproteins

Interleukin-8 (IL-8) is a chemokine that belongs to the alpha-chemokine or CXC subfamily and is produced by a wide variety of human cells, including monocytes and polymorphonuclear cells (PMN). IL-8 is secreted in response to inflammatory stimuli, notably bacterial products such as lipopolysaccharide (LPS), but little is known about the mechanisms by which these agents mediate IL-8 induction. In this report, we show that Mycoplasma fermentans lipid-associated membrane proteins (LAMPf) induce the production of high levels of IL-8 by THP-1 (human monocyte) cells and PMN at the same extent as LPS. It was previously demonstrated that stimulation of monocytic cells with either LPS or LAMPf led to a series of common downstream signaling events, including the activation of protein tyrosine kinase and of mitogen-activated protein kinase cascades. By using PD-98059 and SB203580, two potent and selective inhibitors of MEK1 (a kinase upstream of ERK1/2) and p38, respectively, we have demonstrated that both ERK1/2 and p38 cascades play a key role in the production of IL-8 by monocytes and PMN stimulated with bacterial fractions.

A Mycoplasma fermentans-derived synthetic lipopeptide induces AP-1 and NF-kappaB activity and cytokine secretion in macrophages via the activation of mitogen-activated protein kinase pathways

Mycoplasma lipoproteins have been demonstrated to stimulate monocytic cells and induce proinflammatory cytokine secretion. In this paper, we show that a synthetic analog of the Mycoplasma fermentans membrane-associated lipopeptide macrophage-activating lipopeptide-2 (MALP-2) induces mRNA synthesis and protein secretion of interleukin-1beta and tumor necrosis factor-alpha in human monocytes/macrophages and the murine macrophage cell line RAW 264.7, whereas the nonlipidated counterpart lacks this effect, underscoring the importance of protein acylation for cell activation. Synthetic MALP-2 (sMALP-2) induced the activation of MAPK family members extracellular signal regulated kinases 1 and 2, c-Jun NH2-terminal kinase, and p38 and induced NF-kappaB and AP-1 transactivation in macrophages. Whereas the specific p38 inhibitor SB203580 abrogated both cytokine synthesis and NF-kappaB and AP-1 transactivation in response to MALP-2, the selective MAPK/extracellular signal-regulated kinase-1 inhibitor PD-98059 decreased interleukin-1beta and tumor necrosis factor-alpha production in response to sMALP-2 without affecting the transactivation of NF-kappaB or AP-1. These results indicate that activation of MAPKs by sMALP-2 is a crucial event leading to the expression of proinflammatory cytokines. Our findings demonstrate that the synthetic analog of MALP-2 reproduces the macrophage stimulation activity found in different fractions of mycoplasmas. Given that MALP-2 has been recently shown to be expressed at the surface of M. fermentans as a molecular entity, sMALP-2 constitutes a valuable surrogate for investigating immunomodulation by these microorganisms and evaluating the role that this activity plays in the development of inflammatory diseases associated with mycoplasma infections.

Identification of the cleavage site involved in production of plasma soluble Fc gamma receptor type III (CD16)

CD16 (FcgammaR type III) is a low-affinity IgG Fc receptor (R) that exists in two isoforms, a transmembrane FcgammaRIIIa expressed by NK cells and monocytes, and a phosphatidylinositol-linked FcgammaRIIIb expressed by neutrophils. A soluble form of CD16 (sCD16) circulates in plasma. The cleavage site and the nature of the enzyme(s) involved in production of sCD16 were investigated. Soluble CD16 was purified to apparent homogeneity from human serum by eight steps, including anion exchange and immunoaffinity chromatography. Serum sCD16 was sequenced at both ends, as well as a recombinant form of sCD16 used as control. N-terminal sequencing demonstrated that serum sCD16 originates from neutrophil FcgammaRIIIb and C-terminal sequencing suggested that the cleavage site is between Val 196 and Ser 197, close to the membrane anchor. Addition of a hydroxamate-based inhibitor of Zn2+ metalloproteinases (RU36156) led to a dramatic decrease of sCD16 production by phorbol 12-myristate 13-acetate-activated neutrophils, whereas inhibitors of serine proteinases had no significant effect, showing the metalloproteinase dependence of this cleavage process.

Activation of mitogen-activated protein kinase pathways by Mycoplasma fermentans membrane lipoproteins in murine macrophages: involvement in cytokine synthesis

Stimulation of monocytes and resident macrophages by mycoplasmas induces production of numerous cytokines. We have previously reported that membrane lipoproteins derived from Mycoplasma fermentans are responsible for the induction of proinflammatory cytokines by monocytic cells and that triggering protein tyrosine kinase activation is an essential requirement for this biologic effect. In the present study, we have investigated the effect of M. fermentans-derived membrane lipoproteins (LAMPf) on mitogen-activated protein kinase (MAPK) cascades in the murine macrophage cell line RAW 264.7 and have analyzed the contribution of these pathways to the cytokine induction mediated by this agent. Treatment of murine macrophages with LAMPf resulted in significant activation of MAPK family members extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun NH2-terminal kinase (JNK), and p38. Unlike LPS, these effects were demonstrated to be independent of the presence of serum. The activation of MAPKs paralleled the tyrosine kinase activation and peaked at 30 min after stimulation. The specific p38 inhibitor SB203580 abrogated the mycoplasma-induced IL-6, IL-1beta, and TNF-alpha synthesis. The selective MAPK/extracellular signal-regulated kinase 1 (MEK-1) inhibitor PD-98059 blocked both IL-1beta and TNF-alpha but not IL-6 production by RAW 264.7 cells in response to LAMPf. Additionally, transfection of murine macrophages with a JNK dominant negative mutant significantly reduced only IL-6 production. These data underscore the role of MAPKs as signal transduction molecules controlling the expression of cytokines upon mycoplasma stimulation.

Partial purification and characterization of a tumor necrosis factor-alpha converting activity

Tumor necrosis factor (TNF)-alpha is initially synthesized as an extracellular membrane-associated 26-kDa protein that is further cleaved at Ala76-Val77 to yield the soluble 17-kDa form. Recently, peptide-hydroxamate metalloproteinase inhibitors have been reported to block the proteolytic processing of TNF-alpha, thus suggesting that the putative TNF-alpha converting enzyme (TACE) is a zinc-dependent metalloendopeptidase. In this report, we characterize a TNF-alpha converting activity (TACA) that cleaves in vitro the human 26-kDa TNF-alpha at the physiological processing site. The chromatography steps followed for purification and the use of a panel of proteinase inhibitors indicate that the enzyme responsible for TACA is a membrane glycosylated metalloendopeptidase which is most likely different from the matrix-degrading metalloproteinases. The failure of TACA to process a Val77-->Gly77 precursor mutant emphasizes the importance of hydrophobic residue at P1' position. In addition, TACA is not able to cleave the mouse pro-TNF-alpha and does not catalyze in vitro the processing of other transmembrane proteins susceptible to metalloproteinase-mediated shedding, such as interleukin-6 or TNF receptors. These studies suggest the existence of an enzyme specific for TNF-alpha within the metalloproteinases involved in the processing/shedding of a number of cytokines and cytokine receptors.

A metalloproteinase inhibitor blocks the shedding of soluble cytokine receptors and processing of transmembrane cytokine precursors in human monocytic cells

A number of membrane-anchored cytokines and cytokine receptors are susceptible to yield soluble counterparts. Recently, peptide-hydroxamate metalloproteinase inhibitors have been reported to block the proteolytic processing of tumour necrosis factor (TNF)-alpha 55- and 75-kDa TNF receptors (TNF-R55 and TNF-R75), and interleukin (IL)-6R. In this report the authors studied the effect of an hydroxamate metalloproteinase inhibitor on the secretion of cytokines and the generation of cytokine soluble receptors by human myelomonoycytic cell lines and purified monocytes. Whereas secretion of cytokines lacking a transmembrane domain precursor (IL-1 alpha, IL-1 beta, IL-6 or IL-10) is either unaffected or augmented, shedding/secretion of transmembrane domain-containing cytokines and cytokine receptors [TNF-alpha, macrophage colony-stimulating factor (M-CSF), transforming growth factor (TGF)-alpha, stem cell factor (SCF), TNF-R55, TNF-R75, and IL-6R] was dramatically decreased in the presence of the metalloproteinase inhibitor. The diversity of sequences in the cleavage site of these proteins and differences found in the inhibitory concentration values suggest the existence of a metalloproteinase family displaying different substrate specificity. These results emphasize the important role of metalloproteinases as regulators of membrane expression and secretion of cytokines and cytokine receptors.

Mycoplasma membrane lipoproteins induced proinflammatory cytokines by a mechanism distinct from that of lipopolysaccharide

To gain a clear understanding of the mechanisms by which mycoplasmas induced the expression of proinflammatory cytokines in monocytic cells, we have studied the induction of interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha, and IL-6 by mycoplasmas in three distinct human myelomonocytic cell lines in comparison with induction by lipopolysaccharide (LPS). HL-60 cell line did not release cytokines when induced with either LPS or mycoplasmas. In contrast to LPS, mycoplasmas failed to increase the weak levels of tumor necrosis factor alpha secreted by phorbol myristate acetate-differentiated U937 cells. In addition, Northern (RNA) blot analysis of cytokine expression in these cells showed that the induction of IL-1 beta by mycoplasmas involves, unlike that by LPS, posttranscriptional events. Interestingly, in THP-1 cells, cytokine induction pathways triggered by mycoplasmas remained operational under conditions where LPS pathways were abolished, suggesting functional independence. The study of cytokine-inducing activity displayed by distinct fractions derived from a series of different mycoplasma species demonstrated that lipid membrane constituents were largely responsible for these effects. Finally, we have demonstrated that tyrosine phosphorylation is a crucial event in the mycoplasma-mediated induction of proinflammatory cytokines in either THP-1 cells or human monocytes.

Effects of Mycoplasma fermentans on the myelomonocytic lineage. Different molecular entities with cytokine-inducing and cytocidal potential

Mycoplasma fermentans is a mycoplasma species that has been accused of serving as a cofactor of AIDS development. Here, we show that M. fermentans affects the function of human monocytes and myelomonocytic cell lines on at least two different levels. Heat-inactivated mycoplasma particles induce inflammatory cytokines such as IL-1, IL-6, and TNF in monocytes, as well as in THP-1 cells. Moreover, M. fermentans induces IL-10 (but not IL-12) in freshly isolated human monocytes. The cytokine-inducing effect is mediated by lipid-associated molecules. In addition, we have detected a novel biologic activity that resides in the nonlipid-associated protein fraction of M. fermentans (approximate molecular mass: 15 to 30 kDa) and that has a cytocidal effect on nondifferentiated myelomonocytic cell lines (U937 cells, HL-60 cells), as well as on actinomycin-D-sensitized monocytes. Death is accompanied by oligonucleosomal DNA fragmentation and loss of chromosomal DNA. U937 and HL-60 cells fail to produce cytokines and rather undergo cell death in response to heat-inactivated M. fermentans, provided that they are kept in a relatively undifferentiated stage. Whereas the cytokine-inducing activity is a general feature of many mycoplasma species, it appears that only a restricted panel of mycoplasma species exert a cell death-inducing activity. In addition to M. fermentans strains, Mycoplasma penetrans, another hypothetical cofactor of AIDS, possess a cytocidal activity. This does not apply to other mycoplasma species, including pathogenic ones such as Mycoplasma pneumoniae and Ureaplasma urealyticum. The cell death-inducing effect of M. fermentans is not mediated by cytokines and obeys different principles than TNF-alpha-mediated apoptosis. Thus, in contrast to TNF-alpha-induced death, it is not accompanied by a decrease in the mitochondrial transmembrane potential and is not inhibited by preincubation with the antioxidant drug N-acetylcysteine. In synthesis, it appears that certain AIDS-associated mycoplasma species perturb the function and/or generation of cells from the myelomonocytic lineage via several distinct pathways.

Effects of Mycoplasma fermentans on the myelomonocytic lineage. Different molecular entities with cytokine-inducing and cytocidal potential

Mycoplasma fermentans is a mycoplasma species that has been accused of serving as a cofactor of AIDS development. Here, we show that M. fermentans affects the function of human monocytes and myelomonocytic cell lines on at least two different levels. Heat-inactivated mycoplasma particles induce inflammatory cytokines such as IL-1, IL-6, and TNF in monocytes, as well as in THP-1 cells. Moreover, M. fermentans induces IL-10 (but not IL-12) in freshly isolated human monocytes. The cytokine-inducing effect is mediated by lipid-associated molecules. In addition, we have detected a novel biologic activity that resides in the nonlipid-associated protein fraction of M. fermentans (approximate molecular mass: 15 to 30 kDa) and that has a cytocidal effect on nondifferentiated myelomonocytic cell lines (U937 cells, HL-60 cells), as well as on actinomycin-D-sensitized monocytes. Death is accompanied by oligonucleosomal DNA fragmentation and loss of chromosomal DNA. U937 and HL-60 cells fail to produce cytokines and rather undergo cell death in response to heat-inactivated M. fermentans, provided that they are kept in a relatively undifferentiated stage. Whereas the cytokine-inducing activity is a general feature of many mycoplasma species, it appears that only a restricted panel of mycoplasma species exert a cell death-inducing activity. In addition to M. fermentans strains, Mycoplasma penetrans, another hypothetical cofactor of AIDS, possess a cytocidal activity. This does not apply to other mycoplasma species, including pathogenic ones such as Mycoplasma pneumoniae and Ureaplasma urealyticum. The cell death-inducing effect of M. fermentans is not mediated by cytokines and obeys different principles than TNF-alpha-mediated apoptosis. Thus, in contrast to TNF-alpha-induced death, it is not accompanied by a decrease in the mitochondrial transmembrane potential and is not inhibited by preincubation with the antioxidant drug N-acetylcysteine. In synthesis, it appears that certain AIDS-associated mycoplasma species perturb the function and/or generation of cells from the myelomonocytic lineage via several distinct pathways.

In vitro processing of human tumor necrosis factor-alpha

Tumor necrosis factor (TNF)-alpha is initially synthesized as a membrane-bound, cell-associated 26-kDa protein that is further cleaved to yield the soluble 17-kDa form. By using a radiolabeled in vitro translated TNF-alpha precursor we detected a serine proteinase processing activity present in crude membrane preparations of monocytic cells able to generate a 17-kDa active protein. A similar processing pattern was obtained using purified neutral serine proteinase proteinase-3 (PR-3). Moreover, while a secretory leukocyte proteinase inhibitor (a natural serine anti-proteinase) did not affect the in vitro TNF-alpha processing, IgG preparations containing high titers of anti-PR-3 autoantibodies completely blocked this activity. The NH2-terminal sequencing of the reaction products obtained with either membrane preparations or PR-3 showed that cleavage occurs in both cases between Val77 and Arg78. These results together with cellular expression and localization of PR-3 suggest a potential role for this enzyme as an accessory TNF-alpha processing enzyme.

In-situ preferential usage of V alpha 8 T-cell receptor gene segments in a patient with bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering skin disease associated with the occurrence of autoantibodies directed to a limited series of antigens located at the basement membrane zone of the dermo-epidermal junction. Previous studies have demonstrated the presence of activated T cells in BP lesions although their actual contribution to the pathogenesis of the disease has remained unclear. One approach to better understanding the significance of these T-cell infiltrates is to study the diversity of the recognition receptors (TCRs) expressed at the lesion sites. We report here an extensive analysis, performed in one patient with typical BP, where 187 TCR in frame transcripts from a lesional area, from clinically normal skin or from peripheral blood lymphocytes have been sequenced and compared. The data show preferential usage of the V alpha 8 subfamily gene segments in the lesion. It is therefore suggested that T-cell infiltration in BP may not simply reflect a non-specific inflammatory process but include antigen-specific responses.

Limited T-cell receptor diversity in liver-infiltrating lymphocytes from patients with primary biliary cirrhosis

Primary biliary cirrhosis is associated with the presence of high-titer anti-mitochondrial autoantibodies as well as T-cell infiltration of the liver, suggesting the involvement of autoimmune mechanisms. We have studied here the sequences of T-cell receptor alpha and beta chains expressed by T-cell clones derived from liver-infiltrating lymphocytes of two patients with primary biliary cirrhosis. Among the eight clones studied from the first patient, four expressed the same member of the V beta 6 subfamily, associated with either V alpha 4 (three clones) or V alpha 21 (one clone) gene segment. Two other clones expressed an identical V beta 12 transcript, and two in-frame alpha chain transcripts, involving V alpha 2 and V alpha 7 gene segments. From the second patient, eight out of the nine clones were found to rearrange V beta 17-J beta 2.1 and V alpha 3 gene segments. The remaining clone expressed distinct T-cell receptor chains, involving V beta 9 and V alpha 11 gene segments. As deduced from the analysis of their junctional regions, the eight T-cell clones expressing V beta 17/V alpha 3 gene segments derived from only three different T cells. Furthermore, conserved amino acid motifs were found to be encoded in both the alpha and the beta-chain junctional regions. Together, these data show a local amplification of unique T lymphocytes in both patients. The use of identical V beta J beta and V alpha gene segments with similar junctional sequences by three different cells, evidenced in one of the two cases, strengthens the view that liver-infiltrating T lymphocytes are selected locally by autoantigens in PBC.

The use of anchored polymerase chain reaction for the study of large numbers of human T-cell receptor transcripts

Anchored-PCR (A-PCR) is an approach designed to amplify and clone sequences with unknown 5' or 3' extremities. A-PCR is therefore appropriate for studying variable region of T-cell receptors (TCRs) expressed in polyclonal T-cell populations since it does not prejudge which variable gene segments are actually being used. We report here some critical modifications in the initial procedure to make it easy to clone and sequence large series of TCR transcripts. They have been introduced to improve both the yield and specificity of TCR amplified products and include re-amplification, size selections of the material combined with the successive use of nested TCR constant region specific primers. This procedure has been successfully applied to the study of the repertoire of both TCR alpha/beta+ and gamma/delta+ human T-cells. The efficiency of the present A-PCR protocol will help to precisely analyze TCR usage in normal and pathological situations.

Alternatively spliced T cell receptor transcripts expressed in human T lymphocytes

We used the anchored-polymerase chain reaction (A-PCR) procedure to study human TCR transcripts derived from a variety of polyclonal T cell populations. In this series of experiments, 31 'unusual' cDNAs, which do not include exclusively V-J-C, J-C or 5'C genomic sequences, were identified. Ten of these were found to represent distinct types of alternatively spliced TCR alpha transcripts whose structure is derived from unusual splicing of one, two or even three intervening intronic sequences. The splicing events led to either conservation of a novel exon in the mRNA structure (designated aE1 alpha-aE5 alpha) between the V-J and C segments or to deletion of the 3' V region-J segment. In three cases, the alternatively spliced exons (aE1 alpha-aE3 alpha) interrupt the open translational reading frame of the corresponding V-J alpha segment. Nineteen and two cDNA represent sterile C beta or C delta transcripts, respectively. Their structures are derived from the conservation of a non-translatable exon, aE1 beta or aE1 delta, which is precisely spliced at the 5' end of the corresponding C exon sequences. Interestingly, the 3' region of the aE1 beta sequence is homologous to the murine C beta 0 exon. Together, these results led to the characterization of nine novel exons in the TCR alpha, beta and delta loci.

Analysis of T-cell receptor alpha/beta variability in lymphocytes infiltrating a melanoma metastasis

Multiple experimental and clinical studies have suggested that the immune system may, to some extent, control the development of melanomas. The presence of tumor-infiltrating lymphocytes could reflect an in situ immune reaction directed to the malignant cells. The characterization of T-cell receptor (TCR) expressed by tumor-infiltrating lymphocytes is one way to precisely analyze these local T-cell responses. In this study, we have assessed the TCR alpha/beta variability in tumor-infiltrating lymphocytes from a subcutaneous metastasis of a melanoma patient. Using the anchored-polymerase chain reaction 268 TCR alpha and 266 TCR beta chain transcripts have been cloned and sequenced. Their analysis shows that the T-cell infiltrate is extremely diverse, with no preferential TCR gene segment usage.

An experimentally validated panel of subfamily-specific oligonucleotide primers (V alpha 1-w29/V beta 1-w24) for the study of human T cell receptor variable V gene segment usage by polymerase chain reaction

We report here the characterization of a series of T cell receptor (TcR) V alpha or V beta subfamily-specific oligonucleotide primers. Criteria that have guided the design of each oligonucleotide include appropriate thermodynamic parameters as well as differential base-pairing scores with related and unrelated target sequences. The specificity of the oligonucleotides for each V alpha or V beta subfamily was tested by polymerase chain reaction (PCR) on both a series of TcR encoding plasmid DNA and clonal T cell populations. Unexpected cross-reactivities were observed with plasmid cDNA sequences corresponding to unrelated subfamily gene segments. This led to the synthesis of additional series of oligonucleotides to obtain a relevant panel. A series of V alpha 1-w29/V beta 1-w24 TcR subfamily-specific oligonucleotides was eventually selected which generates little, if any, cross-reactivity. The use of C alpha or C beta primers for the amplification of internal positive control templates (i.e. C beta for the V alpha series and C alpha for the V beta series) has been tested in PCR performed with cDNA derived from peripheral blood lymphocytes; it was shown not to alter the amplification of the V subfamily-specific DNA fragments. This panel of oligonucleotides will be helpful in the study of TcRV gene segment usage and, thus, may lead to a better characterization of T cell responses in physiological and pathological situations.

Studies on the human T cell receptor alpha/beta variable region genes. I. Identification of 7 additional V alpha subfamilies and 14 J alpha gene segments

The anchored-polymerase chain reaction has been used to study further the diversity of the human T cell receptor alpha chain. The analysis of 308 cDNA transcripts from human peripheral lymphocytes hybridizing with a C alpha probe led to the identification of a series of additional V alpha and J alpha gene segments. The sequences of seven V alpha gene segments which individually define a novel V alpha subfamily (termed V alpha w23 to V alpha w29) are reported. The sequences of some previously described V alpha 1, V alpha 2, V alpha 5, V alpha 7 and V alpha 22 gene segments are also extended. In addition, we report 14 novel J alpha gene segment sequences. Taken together, these data indicate that the contribution of the alpha chain combinatorial diversity to the human T cell receptor alpha/beta variability has not yet been fully appreciated.

Molecular characterization of human T cell receptor alpha chains including a V delta 1-encoded variable segment

Previously we have shown that a small fraction of human peripheral T cells expresses a surface receptor recognized both by the BMA031 mAb, specific for a TcR alpha/beta framework epitope, and by the A13 mAb, putatively specific for an epitope encoded by the V delta 1 gene segment. An interleukin 2-dependent polyclonal cell line (termed T2) was derived from such A13+BMA031+ circulating lymphocytes. The molecular characterization of the TcR chains expressed by T2 cells demonstrated indeed that the V delta 1 gene (one of the two major V delta genes) was transcribed with the C alpha gene segment. In the T2 polyclonal cell line, distinct V delta 1/C alpha transcripts were all found to include the same J alpha segment suggesting the existence of "hybrid" TcR alpha/delta chains encoded by unique V delta 1/J alpha rearrangements. The present study was designed to characterize further the V delta 1/J alpha rearranged genes expressed in A13+BMA031+ cells. Three additional cell lines were generated from peripheral blood of distinct adult healthy donors. Using the anchored polymerase chain reaction, it was found that 17 different J alpha segments were used in the 20 V delta 1J alpha C alpha transcripts which have been studied. Together, these data indicate that V delta 1 is a "mixed" (i.e. alpha/delta) TcR V segment which can join with most (if not all) J segments in the alpha/delta locus. In addition, it can be definitely concluded that the A13 mAb recognizes a V delta 1-encoded antigenic determinant and not a V delta 1J epitope (i.e. it can be defined and used as an anti-V delta 1 mAb, as opposed to reagents such as for example delta-TCS-1).

Studies on the human T cell receptor alpha/beta variable region genes. II. Identification of four additional V beta subfamilies

The human T cell receptor (TcR) beta chain gene segment diversity has been studied using the anchored-polymerase chain reaction. Three hundred and fifty C beta-specific transcripts derived from peripheral lymphocytes were analyzed. Transcripts including V-D beta 1-J beta 2-C2 sequences were found with a high frequency (greater than 10%), suggesting that "illegitimate" joinings may constitute a cis-complementing rearrangement mechanism capable of substantially increasing the TcR beta chain combinatorial diversity. Twelve previously undescribed V beta gene segments have been identified. Five of them delineate four novel V beta subfamilies (V beta w21: two members, V beta w22, 23, 24: one member) which all have a murine homologue. The additional seven gene segments belong to the V beta 5, V beta 6, V beta 12 and V beta 13 subfamilies. In addition, the sequences of two known V beta 7 and V beta 9 gene segments have been extended. Together, the present data support the view that the contribution of the beta chain combinatorial diversity to the TcR alpha/beta variability has not yet been fully appreciated.

Cloning and expression of a lymphocyte activation gene (LAG-1)

Using subtractive hybridization of a cDNA library we have identified a human gene, termed LAG-1 (for "Lymphocyte Activation Gene-1"). This cDNA codes for a 69 amino-acid polypeptide which belongs to a new class of recently described proteins secreted by activated lymphocytes and/or monocytes. The LAG-1 gene was cloned, sequenced and its chromosomal location assigned to chromosome 17 (q21 band). The promoter region of the LAG-1 gene was shown to include a GM-CSF-like decanucleotide sequence. Using a baculovirus vector expression system, we found that a 10 kDa recombinant LAG-1 protein is secreted by AcNPV infected SF9 cells, as determined in Western blot experiments by the reactivity of specific anti-peptidic heteroantibodies. Finally the natural LAG-1 protein was precipitated from the supernatant of internally labeled activated Nk cells and shown to migrate as a single entity of 14 kDa in SDS-PAGE analysis.

LAG-3, a novel lymphocyte activation gene closely related to CD4

We have identified a novel human gene of the Ig superfamily, designated LAG-3. Expression of this gene is undetectable in resting PBL, while it is found (a 2-kb message) in activated T and NK cells. The LAG-3 gene includes eight exons; the corresponding cDNA encodes a 498-amino acid membrane protein with four extracellular IgSF domains. The first one belongs to the V-SET; it is particular since it includes an extra loop in the middle of the domain and an unusual intrachain disulphide bridge. The three other domains belong to the C2-SET. Strong internal homologies are found in the LAG-3 molecule between domains 1 and 3, as well as between domains 2 and 4. It is therefore likely that LAG-3 has evolved by duplication of a pre-existing gene encoding a two IgSF-domain structure. The compared analysis of LAG-3 and CD4, with respect to both their peptidic sequence as well as their exon/intron organization, indicated that the two molecules are closely related. This point is strengthened by the finding that both genes are located on the distal part of the short arm of chromosome 12.