Clinical characteristics and outcome of patients over 60 years with Hodgkin lymphoma treated in Switzerland

Hodgkin lymphoma (HL) in older patients appears to be a different disease compared with younger patients with historically lower survival rates. This is related to a variety of factors, including increased treatment-related toxicity, the presence of comorbidities, and biologic differences. In order to better assess the clinical characteristics, treatment strategies, and outcome of this particular population, we conducted a population-based, retrospective analysis including 269 patients with HL older than 60 years (median age 71 years, range 60-94), treated between 2000 and 2017 in 15 referral centers across Switzerland. Primary endpoints were overall survival (OS), progression-free survival (PFS), and cause-specific survival (CSS). The vast majority of patients were treated with curative intent, either with a combined modality approach (chemotherapy followed by radiation therapy) or with systemic therapy. At a median follow-up of 6.6 years (95% confidence interval [CI], 6.0-7.6), 5-year PFS was 52.2% (95% CI, 46.0-59.2), 5-year OS was 62.5% (95% CI, 56.4-69.2), and 5-year CSS was 85.1.8% (95% CI, 80.3-90.1) for the entire cohort. A significant difference in terms of CSS was observed for patients older than 71 years in comparison to patients aged 60-70 years (hazard ratio 2.6, 1.3-5.0, p = 0.005). Bleomycin-induced lung toxicity (BLT) was documented in 26 patients (17.7%) out of the 147 patients exposed to this compound and was more frequent in patients older than 71 years (15/60, 25%). Outcome of HL pts older than 71 years appeared to decrease substantially in comparison to the younger counterpart. Treatment-related toxicities appeared to be relevant, in particular, BLT. New, potentially less toxic strategies need to be investigated in prospective clinical trials in this particular frail population.

Nelfinavir and lenalidomide/dexamethasone in patients with lenalidomide-refractory multiple myeloma. A phase I/II Trial (SAKK 39/10)

The antiretroviral agent nelfinavir has antimyeloma activity and can overcome resistance to bortezomib. Our phase I/II trial investigated whether adding nelfinavir to lenalidomide-dexamethasone can overcome lenalidomide resistance in lenalidomide-refractory multiple myeloma (MM). Twenty-nine patients were included (high-risk cytogenetic aberrations 31%; ≥2 prior therapy lines 93%; lenalidomide-bortezomib double-refractory 34%). Twenty-four patients (83%) had prior bortezomib and 10 (34%) were lenalidomide-bortezomib double-refractory. They received four cycles of nelfinavir 2500 mg/day with standard-dose lenalidomide (25 mg days 1-21) and dexamethasone (40/20 mg days 1, 8, 15, 22). Minor response or better was achieved in 16 patients (55%; 95% CI 36-74%), including 40% of those who were lenalidomide-bortezomib double-refractory, and partial response or better in nine patients (31%; 95% CI 15-51%). Median progression-free survival was 3.4 (95% CI 2.0-4.9) months and median overall survival 21.6 (13.0-50.1) months. Lenalidomide-related pneumonitis, pneumonia, and neutropenic fever occurred, but there were no unexpected adverse events. Peripheral blood mononuclear cells showed a 45% (95% CI 40-51%) reduction in total proteasome activity from baseline and significant induction of unfolded protein response and autophagy. Thus, nelfinavir-lenalidomide-dexamethasone is an active oral combination in lenalidomide-refractory MM.

Multiple myeloma-associated amyloidoma of the sacrum: case report and review of the literature

Study Design Case report. Objectives With only two previously reported cases, localized amyloidosis of the sacrum is extremely rare. Here we report a 64-year-old woman with a large osteolytic lesion accompanied by weakness and paresthesia of the right leg and difficulties in bladder control. Methods Fine needle biopsy and standard staging procedures revealed a primary solitary amyloidoma that was treated with intralesional resection, lumbopelvic stabilization, and consolidation radiotherapy. Results Clinical follow-up revealed the diagnosis of multiple myeloma 9 months after initial treatment. At 12 months, no local recurrence has occurred, the neurologic symptoms have resolved, and the systemic disease is in remission. Conclusions Intralesional resection with adjuvant radiotherapy of the amyloidoma achieved good local tumor control with limited morbidity.

Differential coding potential of ADAM22 mRNAs

ADAM22 is one of three catalytically inactive ADAM family members highly expressed in the brain. Preliminary functional studies suggest possible roles in epilepsy and myelination. We report an additional eight new splice variants of human ADAM22. Analysis of the altered splicing patterns of ADAM22 mRNAs in glioma allows us to suggest alternate splicing patterns in normal brain compared to glioma may represent differential use of exon 32. We also report diversity in the 5' leader sequences of ADAM22 mRNAs as a consequence of alternate transcriptional initiation sites. ADAM22 has an additional transcriptional initiation element producing transcripts lacking the exon 1 sequence including the signal peptide. Variable transcriptional initiation in exon 1 produces a range of ADAM22 5' leader sequence lengths, all of which are significantly longer than those described in NCBI reference sequences. Longer 5' leader sequences contain a second upstream AUG codon which acts to inhibit ADAM22 translation.

Human delta Np73 regulates a dominant negative feedback loop for TAp73 and p53

Inactivation of the tumour suppressor p53 is the most common defect in cancer cells. p53 is a sequence specific transcription factor that is activated in response to various forms of genotoxic stress to induce cell cycle arrest and apoptosis. Induction of p53 is subjected to complex and strict control through several pathways, as it will often determine cellular fate. The p73 protein shares strong structural and functional similarities with p53 such as the potential to activate p53 responsive genes and the ability to induce apoptosis. In addition to alternative splicing at the carboxyl terminus which yields several p73 isoforms, a p73 variant lacking the N-terminal transactivation domain (Delta Np73) was described in mice. In this study, we report the cloning and characterisation of the human Delta Np73 isoforms, their regulation by p53 and their possible role in carcinogenesis. As in mice, human Delta Np73 lacks the transactivation domain and starts with an alternative exon (exon 3'). Its expression is driven by a second promoter located in a genomic region upstream of this exon, supporting the idea of two independently regulated proteins, derived from the same gene. As anticipated, Delta Np73 is capable of regulating TAp73 and p53 function since it is able to block their transactivation activity and their ability to induce apoptosis. Interestingly, expression of the Delta Np73 is strongly up-regulated by the TA isoforms and by p53, thus creating a feedback loop that tightly regulates the function of TAp73 and more importantly of p53. The regulation of Delta Np73 is exerted through a p53 responsive element located on the Delta N promoter. Expression of Delta Np73 not only regulates the function of p53 and TAp73 but also shuts off its own expression, once again finely regulating the whole system. Our data also suggest that increased expression of Delta Np73, functionally inactivating p53, could be involved in tumorogenesis. An extensive analysis of the expression pattern of Delta Np73 in primary tumours would clarify this issue.

Defective gp130-mediated signal transducer and activator of transcription (STAT) signaling results in degenerative joint disease, gastrointestinal ulceration, and failure of uterine implantation

The receptor subunit gp130 transduces multiple cell type-specific activities of the leukemia inhibitory factor (LIF)/interleukin (IL)-6 family of cytokines through the signal transducer and activator of transcription (STAT) and src homology 2 domain-bearing protein tyrosine phosphatase (SHP)-2/ras/Erk pathways. To define STAT-dependent physiological responses, we generated mice with a COOH-terminal gp130(DeltaSTAT) "knock-in" mutation which deleted all STAT-binding sites. gp130(DeltaSTAT) mice phenocopyed mice deficient for IL-6 (impaired humoral and mucosal immune and hepatic acute phase responses) and LIF (failure of blastocyst implantation). However, unlike mice with null mutations in any of the components in the gp130 signaling pathway, gp130(DeltaSTAT) mice also displayed gastrointestinal ulceration and a severe joint disease with features of chronic synovitis, cartilaginous metaplasia, and degradation of the articular cartilage. Mitogenic hyperresponsiveness of synovial cells to the LIF/IL-6 family of cyto-kines was caused by sustained gp130-mediated SHP-2/ras/Erk activation due to impaired STAT-mediated induction of suppressor of cytokine signaling (SOCS) proteins which normally limits gp130 signaling. Therefore, the joint pathology in gp130(DeltaSTAT) mice is likely to arise from the disturbance of the otherwise balanced activation of the SHP-2/ras/Erk and STAT signaling cascades emanating from gp130.

Overexpression of the p73 gene is a novel finding in high-risk B-cell chronic lymphocytic leukemia

The p73 protein shares structural and functional similarities with the tumour-suppressor p53, but its role in neoplastic transformation is unknown. Alternative splicing leads to the expression of at least nine p73 C-terminal mRNA splice variants (alpha, beta, gamma, delta, epsilon, zeta, eta, eta1, theta). In this survey, we analyse the expression of p73 by real-time quantitative RT-PCR, its known C-terminal variants with an RT-PCR-Southern technique and by Western blot in samples of 51 patients with B-CLL, normal B lymphocytes from eight individuals, and five haematopoetic cell lines. p73alpha protein expression positively correlated with higher risk B-CLL stages (P = 0.046). Total p73 mRNA expression was higher (P = 0.01) and p73alpha protein more frequently detected (P = 0.008) in B-CLL compared with normal CD19+-B-lymphocytes. p73 C-terminal mRNA variants were expressed both in B-CLL and in normal B-lymphocytes, but their expression was biased since the gamma (P = 0.041), the theta (P < 0.001), and the eta variant (P = 0.033) prevailed in normal B-lymphocytes. In summary, we conclude that the accumulation of p73, the expression pattern of particular p73 variants and its link to progression may play a distinct role in the molecular pathology B-CLL.

Type I interferons mediate the lipopolysaccharide induction of macrophage cyclin D2

Lipopolysaccharide (LPS) is a powerful macrophage-activating agent and antimitogen. We recently showed that LPS unexpectedly induces cyclin D2 in macrophages. Since LPS stimulates macrophages to produce autocrine-acting cytokines, we examined whether LPS induction of cyclin D2 was mediated by one such type of cytokine, type I interferons (IFN). We report that bone marrow-derived macrophages (BMM) lacking a component of the type I interferon receptor (IFNAR-1) do not express cyclin D2 mRNA or protein in response to LPS stimulation (0.01-1 microg/ml for 7-30 h). Consistent with this result, addition of anti-IFN-alpha/beta neutralizing antibodies reduced levels of LPS-stimulated cyclin D2 in normal BMM. Furthermore, IFN-alpha alone induced cyclin D2 mRNA and protein in normal BMM. Thus, we have identified a new role for type I IFN in macrophages, namely, as essential mediators of LPS-stimulated cyclin D2 expression.

Induction of CD44 expression in stab wounds of the brain: long term persistence of CD44 expression

We studied the expression of the hyaluronan receptor protein CD44 in the mouse brain in response to stab injuries. CD44 expression was strongly activated in the area surrounding the injury within 2 days and then persisted for over 2 months. The expression extended in a direct line the depth of the actual wound inflicted. It appears that CD44 may be involved in the wound healing processes following injury to the brain.

Hyaluronidase-2 overexpression accelerates intracerebral but not subcutaneous tumor formation of murine astrocytoma cells

Gliomas are highly invasive, invariably fatal intracerebral tumors. It seems that receptors for hyaluronan are required for the invasive process. Hyaluronan is a major component of the extracellular matrix in the brain, and all of the gliomas express CD44, the principal receptor for hyaluronan. To investigate the role of lysosomal hyaluronidases on tumor invasion we overexpressed hyaluronidase-2 (HYAL2) in murine astrocytoma cells. We found that high expression of HYAL2 accelerated intracerebral tumor growth dramatically, whereas the same cells formed s.c. tumors within the same time as the parental cells. The brain tumors were highly vascularized and more invasive than the control tumors. It seems that the interactions of the HYAL2-expressing tumor cells with the hyaluronan-containing extracellular matrix in the brain mediate these effects, whereas the same cells in a s.c. environment, which lacks the high hyaluronan level, behave like the parental cells.

Expression of a Y559F mutant CSF-1 receptor in M1 myeloid cells: a role for Src kinases in CSF-1 receptor-mediated differentiation

We have established two M1 myeloid cell lines, M1/WT cells overexpressing the wild-type CSF-1 receptor and M1/Y559F cells expressing a specific tyrosine mutant. M1/WT cells differentiated in response to CSF-1, with a reduction in their proliferative capacity. CSF-1-mediated differentiation was partially abrogated in the M1/Y559F cells, with a less marked reduction in proliferative capacity. The Src tyrosine kinases c-Src, c-Yes, c-Fyn, and c-Hck were tyrosine phosphorylated in the M1/WT cells in response to CSF-1 and bound to the WT CSF-1R through their SH2 domains. Binding of the Src kinases to the CSF-1 receptor was greatly reduced in the M1/Y559F cells. CSF-1-mediated activation of STAT3 was also abrogated in the M1/Y559F cell line. Treatment of M1/WT cells with the Src family inhibitor PP2 resulted in an inhibition of CSF-1-mediated differentiation, equivalent to that observed in the M1/Y559F cells. These data suggest that the reduced Src binding observed in the M1/Y559F cells may contribute to their reduced ability to differentiate.

The carboxyl-terminal domains of gp130-related cytokine receptors are necessary for suppressing embryonic stem cell differentiation. Involvement of STAT3

Cell type-specific responses to the leukemia inhibitory factor (LIF)/interleukin 6 cytokine family are mediated by dimerization of the LIF receptor alpha-chain (LIFRalpha) with the signal transducer gp130 or of two gp130 molecules followed by activation of the JAK/STAT and Ras/mitogen-activated protein kinase cascades. In order to dissect the contribution of gp130 and LIFRalpha individually, chimeric molecules consisting of the extracellular domain of the granulocyte colony stimulating factor receptor (GCSF-R) and various mutant forms of the cytoplasmic domains of gp130 or LIFRalpha were expressed in embryonic stem (ES) cells to test for suppression of differentiation, or in a factor-dependent plasma cytoma cell line to assess for induction of proliferation. Carboxyl-terminal domains downstream of the phosphatase (SHP2)-binding sites were dispensable for mitogen-activated protein kinase activation and the transduction of proliferative signals. Moreover, carboxyl-terminal truncation mutants which lacked intact Box 3 homology domains showed decreased STAT3 activation, failed to induce Hck kinase activity and suppress ES cell differentiation. Moreover, STAT3 antisense oligonucleotides impaired LIF-dependent inhibition of differentiation. Substitution of the tyrosine residue within the Box 3 region of the GSCF-R abolished receptor-mediated suppression of differentiation without affecting the transduction of proliferative signals. Thus, distinct cytoplasmic domains within the LIFRalpha, gp130, and GCSF-R transduce proliferative and differentiation suppressing signals.

Differential ability of SOCS proteins to regulate IL-6 and CSF-1 induced macrophage differentiation

M1/WT4 cells, derived from the murine myeloid leukemic M1 cells by over-expression of the receptor for CSF-1, were transfected with expression vectors encoding SOCS-1, SOCS-2, SOCS-3 or Cis-1. The differentiation response to CSF-1 and IL-6 was analyzed in the resulting cell lines. Myeloid differentiation in response to CSF-1 was not affected by any of the SOCS proteins, whereas the IL-6-mediated differentiation was inhibited by SOCS-1 and SOCS-3 and slightly delayed by SOCS-2 expression. In M1/WT4 cells IL-6 causes strong tyrosine phosphorylation of STAT3, whereas the response to CSF-1 is weaker. The expression of the SOCS proteins had no effect on CSF-1 mediated STAT3 tyrosine phosphorylation; however, SOCS-1 and SOCS-3 reduced the tyrosine phosphorylation of STAT3 in response to IL-6 but did not abolish it. It appears, therefore, that SOCS-1, -2 and -3 and Cis-1 do not inhibit tyrosine kinase activity involved in CSF-1 mediated cell differentiation, whereas SOCS-1 and -3 are inhibiting kinase activity required for IL-6-mediated differentiation.

Proliferation-independent induction of macrophage cyclin D2, and repression of cyclin D1, by lipopolysaccharide

D-type cyclins are induced in response to mitogens and are essential and rate-limiting for G1 phase progression in normal mammalian cells. Macrophages proliferating in response to colony-stimulating factor-1 (CSF-1) express cyclin D1 and to a lesser extent cyclin D2 but not cyclin D3. Previously we showed that the macrophage-activating agent lipopolysaccharide (LPS) blocks CSF-1-induced proliferation and cyclin D1 expression in macrophages. Here we report upon the effect of LPS on expression of cyclin D2 in normal mouse bone marrow-derived macrophages (BMM). Unexpectedly we found that this anti-mitogen raised levels of CSF-1-stimulated cyclin D2 mRNA and protein. Furthermore, LPS alone induced cyclin D2 but not cyclin D1. Inhibition of the MEK/ERK (MAPK/ERK kinase/extracellular signal-regulated kinase) mitogen-activated protein kinase pathway repressed LPS-induced cyclin D2 mRNA, whereas inhibition of the p38 mitogen-activated protein kinase enhanced expression. However, in contrast to cyclin D1, cyclin D2 in bone marrow-derived macrophages did not appear to be regulated by protein kinase A pathways. The present data (a) show elevation of a D-type cyclin in the absence of proliferation, (b) demonstrate inverse regulation of two distinct D-type cyclins under identical conditions, and (c) suggest that cyclin D2 plays a role in macrophage activation by LPS.

STAT3 forms stable homodimers in the presence of divalent cations prior to activation

We present evidence that the transcription factor STAT3, derived from uninduced cells, can form stable homodimers, which are independent of the tyrosine phosphorylation status of the protein. The strong interaction, which is resistant to many denaturing agents, is dependent on the presence of divalent cations. The presence of the homodimer was initially observed in immunoprecipitates of STAT3 and was detected upon fractionation of cell lysates. These dimers are different in structure from dimers observed after cytokine stimulation of cells, which results in tyrosine phosphorylation of STAT3 and dimerization involving the SH2 domain of STAT3.

CSF-1 and interferon-gamma act synergistically to promote differentiation of FDC-P1 cells into macrophages

FDC-P1 cells expressing the wildtype CSF-1 receptor, FDwtfms, differentiate into macrophages during incubation with CSF-1. This response is amplified in the presence of interferon-gamma. Cells expressing the 807F mutant receptor, 807F cells, proliferate in response to CSF-1 and do not differentiate. However, in response to CSF-1 and interferon-gamma they differentiate as well. CSF-1 causes the activation of STAT proteins in FDwtfms cells, but not in 807F cells. Cellular differentiation correlates with a sustained activation of STAT1 and STAT3 in response to interferon-gamma over at least 40 hours. However, interferon-gamma alone did not cause differentiation of cells expressing either receptor. Other defects in response to CSF-1 of the 807F cells, such as lack of PLC gamma 2 activation, were not complemented by co-incubation of the cells with CSF-1 and interferon-gamma. It appears that a combination of signaling pathways are activated by CSF-1 and interferon-gamma which caused the shift of response from proliferation to differentiation in the 807F cells and an enhanced differentiation in the FDwtfms cells.

Distinct roles for leukemia inhibitory factor receptor alpha-chain and gp130 in cell type-specific signal transduction

Leukemia inhibitory factor (LIF) induces a variety of disparate biological responses in different cell types. These responses are thought to be mediated through the functional LIF receptor (LIFR), consisting of a heterodimeric complex of LIFR alpha-chain (LIFRalpha) and gp130. The present study investigated the relative capacity of the cytoplasmic domains of each receptor subunit to signal particular responses in several cell types. To monitor the signaling potential of LIFRalpha and gp130 individually, we constructed chimeric receptors by linking the extracellular domain of granulocyte colony-stimulating factor receptor (GCSFR) to the transmembrane and cytoplasmic regions of either LIFRalpha or gp130. Both chimeric receptors and the full-length GCSFR in expressed in M1 myeloid leukemic cells to measure differentiation induction, in embryonic stem cells to measure differentiation inhibition, and in Ba/F3 cells to measure cell proliferation. Our results demonstrated that whereas GCSFR-gp130 receptor homodimer mediated a GCSF-induced signal in all three cell types, the GCSFR-LIFRalpha receptor homodimer was only functional in embryonic stem cells. These findings suggest that the signaling potential of gp130 and LIFRalpha cytoplasmic domains may differ depending upon the tissue and cellular response initiated.

Requirement for Y706 of the murine (or Y708 of the human) CSF-1 receptor for STAT1 activation in response to CSF-1

Using FDC-P1 derived cell lines which ectopically express either the wild type or mutant forms of the murine CSF-1 receptor in which individual tyrosine residues have been replaced with phenylalanine, we analysed the requirement for tyrosine residues of the receptor for the activation of STAT proteins in response to CSF-1. We found Y706 to be required for efficient activation of STAT1. The activation of STAT3 was not affected by the mutation of Y706 to phenylalanine. The addition of phosphopeptides spanning Y708 of the human CSF-1 receptor (identical with the sequence surrounding Y706 of the murine receptor) to electrophoretic mobility shift assays led to competition of the formation of STAT1 containing complexes, SIF-B and SIF-C with the DNA probe. These phosphopeptides did, however, not affect the formation of the STAT3 containing complex, SIF-A, with the probe. Replacement of Y807 with phenylalanine led to a complete block of activation of all STAT proteins in response to CSF-1, however, this phosphotyrosine does not appear to represent a STAT binding site of the receptor as a phosphopeptide spanning Y809 of the human CSF-1 receptor could not compete any STAT/DNA complex formation in electrophoretic mobility shift assays.

Tyrosine-599 of the c-Mpl receptor is required for Shc phosphorylation and the induction of cellular differentiation

Interaction of thrombopoietin (TPO) with its receptor, c-Mpl, triggers cell growth and differentiation responses controlling primitive haemopoietic cell production and megakaryocytopoiesis. To examine the important receptor domains and signal transduction pathways involved in these cellular responses, c-Mpl cytoplasmic domain truncation and tyrosine substitution mutants were generated. In the myelomonocytic leukaemia cell lines WEHI3B-D+ and M1, ectopic expression of the wild-type c-Mpl receptor induced TPO-dependent cellular differentiation characterized by increased cell migration through agar and acquisition of the morphology and molecular markers of macrophages. Consistent with the concept that proliferative and differentiation signals emanate from distinct receptor domains, the C-terminal 33 amino acids of c-Mpl were dispensable for a proliferative response in Ba/F3 cells but proved critical for WEHI3B-D+ and M1 differentiation. Finer mapping revealed that substitution of Tyr599 by phenylalanine within this c-Mpl domain was sufficient to abolish the normal differentiation response. Moreover, in contrast to the normal c-Mpl receptor, this same mplY599F mutant was also incapable of stimulating TPO-dependent Shc phosphorylation, the association of Shc with Grb2 or c-Mpl and of inducing c-fos expression. Thus activation of components of the Ras signalling cascade, initiated by interaction of Shc with c-Mpl Tyr599, may play a decisive role in specific differentiation signals emanating from the c-Mpl receptor.

Tyrosine residues in the granulocyte colony-stimulating factor (G-CSF) receptor mediate G-CSF-induced differentiation of murine myeloid leukemic (M1) cells

The cytoplasmic tyrosine residues of many growth factor receptors have been shown to be important for receptor signal transduction via the recruitment of proteins containing phosphotyrosine-binding domains. This study demonstrates the importance of specific tyrosine residues in the granulocyte colony-stimulating factor (G-CSF) receptor cytoplasmic domain in G-CSF-induced macrophage cell differentiation. Site-directed mutagenesis was used to generate a series of G-CSF receptor (G-CSF-R) mutants in which the tyrosine residues were replaced with phenylalanine either singly or in combination. The mouse myeloid leukemic cell line (M1) transfected with G-CSF-R cDNA can be induced to differentiate into macrophages in response to G-CSF. The effect of the tyrosine mutations on this differentiation response was assessed by examining cell morphology and differentiation in soft agar colony assays. Although three of the four cytoplasmic tyrosine residues appeared to contribute to the differentiation response, mutation of a single residue (Tyr744) significantly reduced the ability of the M1 cells to differentiate. The STAT family of signaling molecules (Stat1, Stat3, and Stat5) were activated by G-CSF in M1 cells expressing those G-CSF-R tyrosine mutants unable to mediate G-CSF-induced differentiation. Furthermore, activation of STAT proteins was shown to occur in the absence of all four cytoplasmic tyrosine residues, suggesting an alternative mechanism for STAT activation other than direct interaction with receptor phosphotyrosines.

Formation of STAT5-containing DNA binding complexes in response to colony-stimulating factor-1 and platelet-derived growth factor

Colony-stimulating factor (CSF-1) activates several members belonging to the STAT (signal transducers and activators of transcription) family of transcription factors. We investigated the DNA binding complexes activated by CSF-1 in several cell lines and compared them with complexes activated by platelet-derived growth factor and interleukin 3. Our results indicate that the SIF-A complex activated by CSF-1 and platelet-derived growth factor may contain STAT3/STAT5 heterodimers binding to the high affinity SIF binding site, m67. In addition, both growth factors activate one or several STAT5-containing protein complexes binding to the prolactin-inducible element, PIE. The formation of these complexes was cell type and growth factor specific. Interleukin 3 activated only PIE binding complexes containing STAT5A and STAT5B and did not activate m67 binding complexes. It appears, therefore, that STAT5 cannot bind to m67 as a homodimer, but it can bind if it is dimerized with STAT3, whereas it can bind to the PIE element without being either complexed with STAT3 or any other known STAT protein, possibly as a homodimer or as STAT5A/STAT5B heterodimer. However, in addition, STAT5 may heterodimerize with other proteins and form novel PIE binding complexes.

Differential regulation of cell cycle machinery by various antiproliferative agents is linked to macrophage arrest at distinct G1 checkpoints

There is currently much interest in the mechanisms of action of antiproliferative agents and their effects on cell cycle machinery. In the present study we examined the mechanisms of action of four unrelated agents known to inhibit proliferation of CSF-1-stimulated bone marrow-derived macrophages (BMM). We report that 8-bromo-cAMP (8Br-cAMP) and lipopolysaccharide (LPS) potently reduced CSF-1-stimulated cyclin D1 protein, and cyclin-dependent kinase (cdk) 4 mRNA and protein levels, while the inhibitory effects of the Na+/ H+ antiport inhibitor 5-(N',N'-dimethyl) amiloride (DMA) and interferon gamma (IFN gamma ) were only weak. All agents repressed CSF-1-stimulated retinoblastoma protein phosphorylation. Furthermore, 8Br-cAMP and to a lesser extent IFN gamma, also reduced CSF-1-stimulated levels of E2F DNA binding activity in a macrophage cell line, BAC1.2F5. An explanation for the different effects of the agents is that 8Br-cAMP and LPS were found to arrest BMM in early/mid-G1, while IFN gamma and DMA arrested cells in late G1 or early S phase. These data indicate that (1) different antiproliferative agents can arrest the same cell type at distinct checkpoints in G1 and (2) effects of antiproliferative agents on cell cycle machinery is linked to the position at which they arrest cells in G1.

Aberrant activation of JAK/STAT pathway components in response to G-CSF, interferon-alpha/beta and interferon-gamma in NFS-60 cells

There is evidence that the cellular responses to cytokines, such as granulocyte colony stimulating factor (G-CSF) and interferons, depend on prior activation of components of the JAK/STAT signalling pathway. We report here that the myeloid cell line NFS-60 shows aberrant JAK/STAT signalling yet elicits expected biological responses to G-CSF and interferons-alpha/beta and gamma. Instead of increased phosphorylation of JAK1 and JAK2 in response to G-CSF and interferon-gamma, and JAK1 and Tyk2 in response to interferon-alpha/beta, we observed only an increase of phosphorylation of Tyk2 in response to all of these cytokines in NFS-60 cells. The subset of STAT proteins being activated in response to these cytokines was unusual as well. G-CSF activated STAT3 and STAT5A, whereas interferons activated, in addition to STAT1 and STAT5 other, as yet unidentified, DNA binding proteins. However, NFS-60 cells show normal biological responses to these cytokines, such as proliferation in response to G-CSF, and reduction of proliferation, induction of an anti-viral response and induction of specific genes in response to interferons.

Distinct regions of the granulocyte colony-stimulating factor receptor are required for tyrosine phosphorylation of the signaling molecules JAK2, Stat3, and p42, p44MAPK

The protein tyrosine kinases JAK1 and JAK2 are phosphorylated tyrosine after the interaction of granulocyte colony-stimulating factor (G-CSF) with its transmembrane receptor. So too is Stat3, a member of the STAT family of transcriptional activators thought to be activated by the JAK kinases. Truncated G-CSF receptor (G-CSF-R) mutants were used to determine the different regions of the cytoplasmic domain necessary for tyrosine phosphorylation of the signaling molecules JAK2, Stat3, and p42, p44MAPK. We have shown that G-CSF-induced tyrosine phosphorylation and kinase activation of JAK2 requires the membrane proximal 57 amino acids of the cytoplasmic domain. In contrast, maximal Stat3 tyrosine phosphorylation required amino acids 96 to 183 of the G-CSF-R cytoplasmic domain, Stat3 DNA binding could occur with a receptor truncated 96 amino acids from the transmembrane domain and containing a single tyrosine residue, but was reduced in comparison with the full-length receptor. Together with the tyrosine phosphorylation of Stat3, this finding suggests that additional Stat3 does not appear to be required for proliferation. MAP kinase tyrosine phosphorylation correlated with both the proliferative response and JAK2 activation.

Colony-stimulating factor 1-induced STAT1 and STAT3 activation is accompanied by phosphorylation of Tyk2 in macrophages and Tyk2 and JAK1 in fibroblasts

Colony-stimulating factor 1 (CSF-1) causes the activation of STAT1 and STAT3 transcription factors in bone marrow macrophages (BMM), in the macrophage cell line BAC1.2F5, and in fibroblasts that express the wild-type receptor for CSF-1. Fibroblasts expressing a mutant receptor in which the tyrosine 809 is replaced with phenylalanine do not activate STAT proteins in response to CSF-1. The activation of the STAT proteins in BMM is accompanied by tyrosine phosphorylation of Tyk2. In fibroblasts, the activation of the STAT proteins is accompanied by tyrosine phosphorylation of Tyk2 and JAK1. We propose that these JAK kinases are subjected to very rapid phosphorylation in response to CSF-1, followed by rapid dephosphorylation. Furthermore, we propose that kinases other than JAK kinase may be involved in the phosphorylation of the STAT proteins in response to CSF-1.

Regulation of the urokinase gene by the retinoblastoma protein

The promoter of the human urokinase plasminogen activator (uPA) gene contains a sequence identical with the retinoblastoma control element (RCE) of the murine c-fos gene, as well as several Sp1 binding sites. In a number of cell lines, the uPA promoter is activated during enforced expression of the retinoblastoma protein, pRB. Electrophoretic mobility-shift assays revealed that the RCE sequence of the uPA gene forms only one specific DNA-protein complex that does not contain pRB. The formation of the RCE-protein complex can be inhibited by 20 molar excess of the unlabeled RCE sequences and by 5 molar excess of the unlabeled E2F binding site. The RCE of the human uPA gene interacts specifically with a protein, which appears to be distinct from members of the E2F family of proteins, Sp1, ATF2, and Elf-1, which are all transcription factors shown to be regulated by pRB.

Cytokine modulation of plasminogen activator inhibitor-1 (PAI-1) production by human articular cartilage and chondrocytes. Down-regulation by tumor necrosis factor alpha and up-regulation by transforming growth factor-B basic fibroblast growth factor

Recombinant human cytokines were examined for their effects on plasminogen activator inhibitor-1 (PAI-1) production by human articular cartilage and chondrocyte monolayer cultures. Cartilage and chondrocytes were cultured with and without added cytokines and the conditioned media assayed for PAI-1 by a specific enzyme-linked immunosorbent assay, and mRNA levels determined by Northern blot analysis. Tumor necrosis factor alpha (TNF alpha) reduced, and transforming growth factor-beta (TGF-beta) and basic fibroblast growth factor (bFGF) increased, the levels of PAI-1 antigen and mRNA in the culture fluids and cell extracts, respectively. The effects of TNF alpha and TGF-beta on PAI-1 antigen levels were both time- and concentration-dependent; optimum doses being 10-100 pM TNF alpha and 0.4-0.8 nM TGF-beta, with each cytokine exerting its effect on PAI-1 antigen levels within 8 h of addition to culture. TNF alpha (and interleukin-1 alpha) also countered the effects of TGF-beta and bFGF. The anti-inflammatory drugs, indomethacin and dexamethasone, did not appear to modulate PAI-1 levels in cultures of cartilage tissue. The inhibition of PAI-1 levels by cytokines and reagents which stimulate cartilage resorption (i.e., TNF alpha, interleukin-1 alpha, retinoic acid) and enhancement by cytokines which counter it (i.e., TGF-beta, bFGF) further implicate plasminogen activator in the mechanism(s) of cartilage degradation in diseases such as arthritis.