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A variety of cytokines mediate the activation of Janus protein tyrosine kinases (Jaks). The Jaks then phosphorylate cellular substrates,including members of the signal transducers and activators of transcription (Stat) family of transcription factors. Among the Stats,the two highly related proteins,Stat5a and Stat5b,are activated by a variety of cytokines. To assess the role of the Stat5 proteins,mutant mice were derived that have the genes deleted individually or together. The phenotypes of the mice demonstrate an essential,and often redundant,role for the two Stat5 proteins in a spectrum of physiological responses associated with growth hormone and prolactin. Conversely,the responses to a variety of cytokines that activate the Stat5 proteins,including erythropoietin,are largely unaffected. View Publication

The novel quinazoline derivative 4-(3'-bromo-4'-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P154) exhibited significant cytotoxicity against U373 and U87 human glioblastoma cell lines,causing apoptotic cell death at micromolar concentrations. The in vitro antiglioblastoma activity of WHI-P154 was amplified textgreater 200-fold and rendered selective by conjugation to recombinant human epidermal growth factor (EGF). The EGF-P154 conjugate was able to bind to and enter target glioblastoma cells within 10-30 min via receptor (R)-mediated endocytosis by inducing internalization of the EGF-R molecules. In vitro treatment with EGF-P154 resulted in killing of glioblastoma cells at nanomolar concentrations with an IC50 of 813 +/- 139 nM,whereas no cytotoxicity against EGF-R-negative leukemia cells was observed,even at concentrations as high as 100 microM. The in vivo administration of EGF-P154 resulted in delayed tumor progression and improved tumor-free survival in a severe combined immunodeficient mouse glioblastoma xenograft model. Whereas none of the control mice remained alive tumor-free beyond 33 days (median tumor-free survival,19 days) and all control mice had tumors that rapidly progressed to reach an average size of textgreater 500 mm3 by 58 days,40% of mice treated for 10 consecutive days with 1 mg/kg/day EGF-P154 remained alive and free of detectable tumors for more than 58 days with a median tumor-free survival of 40 days. The tumors developing in the remaining 60% of the mice never reached a size textgreater 50 mm3. Thus,targeting WHI-P154 to the EGF-R may be useful in the treatment of glioblastoma multiforme. View Publication

BACKGROUND There have been many randomised trials of adjuvant tamoxifen among women with early breast cancer,and an updated overview of their results is presented. METHODS In 1995,information was sought on each woman in any randomised trial that began before 1990 of adjuvant tamoxifen versus no tamoxifen before recurrence. Information was obtained and analysed centrally on each of 37000 women in 55 such trials,comprising about 87% of the worldwide evidence. Compared with the previous such overview,this approximately doubles the amount of evidence from trials of about 5 years of tamoxifen and,taking all trials together,on events occurring more than 5 years after randomisation. FINDINGS Nearly 8000 of the women had a low,or zero,level of the oestrogen-receptor protein (ER) measured in their primary tumour. Among them,the overall effects of tamoxifen appeared to be small,and subsequent analyses of recurrence and total mortality are restricted to the remaining women (18000 with ER-positive tumours,plus nearly 12000 more with untested tumours,of which an estimated 8000 would have been ER-positive). For trials of 1 year,2 years,and about 5 years of adjuvant tamoxifen,the proportional recurrence reductions produced among these 30000 women during about 10 years of follow-up were 21% (SD 3),29% (SD 2),and 47% (SD 3),respectively,with a highly significant trend towards greater effect with longer treatment (chi2(1)=52.0,2ptextless0.00001). The corresponding proportional mortality reductions were 12% (SD 3),17% (SD 3),and 26% (SD 4),respectively,and again the test for trend was significant (chi2(1) = 8.8,2p=0.003). The absolute improvement in recurrence was greater during the first 5 years,whereas the improvement in survival grew steadily larger throughout the first 10 years. The proportional mortality reductions were similar for women with node-positive and node-negative disease,but the absolute mortality reductions were greater in node-positive women. In the trials of about 5 years of adjuvant tamoxifen the absolute improvements in 10-year survival were 10.9% (SD 2.5) for node-positive (61.4% vs 50.5% survival,2ptextless0.00001) and 5.6% (SD 1.3) for node-negative (78.9% vs 73.3% survival,2ptextless0.00001). These benefits appeared to be largely irrespective of age,menopausal status,daily tamoxifen dose (which was generally 20 mg),and of whether chemotherapy had been given to both groups. In terms of other outcomes among all women studied (ie,including those with ER-poor" tumours)� View Publication

Three mitogen-activated protein kinase pathways are up-regulated during the activation of T lymphocytes,the extracellular signal-regulated kinase (ERK),Jun NH2-terminal kinase,and p38 mitogen-activated protein kinase pathways. To examine the effects of blocking the ERK pathway on T cell activation,we used the inhibitor U0126,which has been shown to specifically block mitogen-activated protein kinase/ERK kinase (MEK),the kinase upstream of ERK. This compound inhibited T cell proliferation in response to antigenic stimulation or cross-linked anti-CD3 plus anti-CD28 Abs,but had no effect on IL-2-induced proliferation. The block in T cell proliferation was mediated by down-regulating IL-2 mRNA levels. Blocking Ag-induced proliferation by inhibiting MEK did not induce anergy,unlike treatments that block entry into the cell cycle following antigenic stimulation. Surprisingly,induction of anergy in T cells exposed to TCR cross-linking in the absence of costimulation was also not affected by blocking MEK,unlike cyclosporin A treatment that blocks anergy induction. These results suggest that inhibition of MEK prevents T cell proliferation in the short term,but does not cause any long-term effects on either T cell activation or induction of anergy. These findings may help determine the viability of using mitogen-activated protein kinase inhibitors as immune suppressants. View Publication

Recent studies have shown efficient gene transfer to primitive progenitors in human cord blood (CB) when the cells are incubated in retrovirus-containing supernatants on fibronectin-coated dishes. We have now used this approach to achieve efficient gene transfer to human CB cells with the capacity to regenerate lymphoid and myeloid progeny in nonobese diabetic (NOD)/severe combined immunodeficiency (SCID) mice. CD34(+) cell-enriched populations were first cultured for 3 days in serum-free medium containing interleukin-3 (IL-3),IL-6,granulocyte colony-stimulating factor,Flt3-ligand,and Steel factor followed by two 24-hour incubations with a MSCV-NEO virus-containing medium obtained under either serum-free or serum-replete conditions. The presence of serum during the latter 2 days made no consistent difference to the total number of cells,colony-forming cells (CFC),or long-term culture-initiating cells (LTC-IC) recovered at the end of the 5-day culture period,and the cells infected under either condition regenerated similar numbers of human CD34(+) (myeloid) CFC and human CD19(+) (B lymphoid) cells for up to 20 weeks in NOD/SCID recipients. However,the presence of serum increased the viral titer in the producer cell-conditioned medium and this was correlated with a twofold to threefold higher efficiency of gene transfer to all progenitor types. With the higher titer viral supernatant,17% +/- 3% and 17% +/- 8%,G418-resistant in vivo repopulating cells and LTC-IC were obtained. As expected,the proportion of NEO + repopulating cells determined by polymerase chain reaction analysis of in vivo generated CFC was even higher (32% +/- 10%). There was no correlation between the frequency of gene transfer to LTC-IC and colony-forming unit-granulocyte-macrophage (CFU-GM),or to NOD/SCID repopulating cells and CFU-GM (r2 = 0.16 and 0.17,respectively),whereas values for LTC-IC and NOD/SCID repopulating cells were highly and significantly correlated (r2 = 0.85). These findings provide further evidence of a close relationship between human LTC-IC and NOD/SCID repopulating cells (assessed using a textgreater/= 6-week CFC output endpoint) and indicate the predictive value of gene transfer measurements to such LTC-IC for the design of clinical gene therapy protocols. View Publication

The prototype of a new class of antiproliferative phospholipid analogs,hexadecylphosphocholine (HePC),has been shown to inhibit tumor growth and is currently used for the treatment of cutaneous metastases of mammary carcinomas. Although several cellular targets of HePC,e.g. protein kinase C and CTP:phosphocholine cytidylyltransferase,have been proposed,the mechanisms of HePC-induced anticancer activity are still unclear. Considering that the antiproliferative effect of HePC correlates with inhibition of phosphatidylcholine biosynthesis,which is tightly coupled to sphingomyelin biosynthesis,we tested the hypothesis that treatment of cells with the anticancer drug leads to increased cellular ceramide and subsequently to apoptotic cell death. In the present study,we showed that 25 micromol/liter HePC induced apoptosis. In further experiments,we demonstrated that HePC inhibited the incorporation of radiolabeled choline into phosphatidylcholine and at a later time point into sphingomyelin. This was confirmed by metabolic labeling of the lipid backbone using radiolabeled serine,and it was shown that HePC decreased the incorporation of serine into sphingomyelin by 35% and simultaneously increased the incorporation of serine into ceramide by 70%. Determination of the amount of ceramide revealed an increase of 53% in HePC-treated cells compared with controls. In accordance with the hypothesis that elevated ceramide levels may be the missing link between the metabolic effects of HePC and its proapoptotic properties,HePC-induced apoptosis was blocked by fumonisin B1,an inhibitor of ceramide synthesis. Furthermore,we found that membrane-permeable ceramides additively increased the apoptotic effect of HePC. View Publication

Any epithelial portion of a normal mouse mammary gland can reproduce an entire functional gland when transplanted into an epithelium-free mammary fat pad. Mouse mammary hyperplasias and tumors are clonal dominant populations and probably represent the progeny of a single transformed cell. Our study provides evidence that single multipotent stem cells positioned throughout the mature fully developed mammary gland have the capacity to produce sufficient differentiated progeny to recapitulate an entire functional gland. Our evidence also demonstrates that these stem cells are self-renewing and are found with undiminished capacities in the newly regenerated gland. We have taken advantage of an experimental model where mouse mammary tumor virus infects mammary epithelial cells and inserts a deoxyribonucleic acid copy(ies) of its genome during replication. The insertions occur randomly within the somatic genome. CzechII mice have no endogenous nucleic acid sequence homology with mouse mammary tumor virus; therefore all viral insertions may be detected by Southern analysis provided a sufficient number of cells contain a specific insertional event. Transplantation of random fragments of infected CzechII mammary gland produced clonal-dominant epithelial populations in epithelium-free mammary fat pads. Serial transplantation of pieces of the clonally derived outgrowths produced second generation glands possessing the same viral insertion sites providing evidence for self-renewal of the original stem cell. Limiting dilution studies with cell cultures derived from third generation clonal outgrowths demonstrated that three multipotent but distinct mammary epithelial progenitors were present in clonally derived mammary epithelial populations. Estimation of the potential number of multipotent epithelial cells that may be evolved from an individual mammary-specific stem cell by self-renewal is in the order of 10(12)-10(13). Therefore,one stem cell might easily account for the renewal of mammary epithelium over several transplant generations. View Publication

Elucidation of mechanisms that regulate hematopoietic stem cell self-renewal and differentiation would be facilitated by the identification of defined culture conditions that allow these cells to be amplified. We now demonstrate a significant net increase (3-fold,P textless 0.001) in vitro of cells that are individually able to permanently and competitively reconstitute the lymphoid and myeloid systems of syngeneic recipient mice when Sca-1(+)lin- adult marrow cells are incubated for 10 days in serum-free medium with interleukin 11,flt3-ligand,and Steel factor. Moreover,the culture-derived repopulating cells continued to expand their numbers in the primary hosts at the same rate seen in recipients of noncultured stem cells. In the expansion cultures,long-term culture-initiating cells increased 7- +/- 2-fold,myeloid colony-forming cells increased 140- +/- 36-fold,and total nucleated cells increased 230- +/- 62-fold. Twenty-seven of 100 cultures initiated with 15 Sca-1(+)lin- marrow cells were found to contain transplantable stem cells 10 days later. This frequency of positive cultures is the same as the frequency of transplantable stem cells in the original input suspension,suggesting that most had undergone at least one self-renewal division in vitro. No expansion of stem cells was seen when Sca-1+TER119- CD34+ day 14.5 fetal liver cells were cultured under the same conditions. These findings set the stage for further investigations of the mechanisms by which cytokine stimulation may elicit different outcomes in mitotically activated hematopoietic stem cells during ontogeny and in the adult. View Publication

CGP 57148 is a compound of the 2-phenylaminopyrimidine class that selectively inhibits the tyrosine kinase activity of the ABL and the platelet-derived growth factor receptor (PDGFR) protein tyrosine kinases. We previously showed that CGP 57148 selectively kills p210BCR-ABL-expressing cells. To extend these observations,we evaluated the ability of CGP 57148 to inhibit other activated ABL tyrosine kinases,including p185BCR-ABL and TEL-ABL. In cell-based assays of ABL tyrosine phosphorylation,inhibition of ABL kinase activity was observed at concentrations similar to that reported for p210BCR-ABL. Consistent with the in vitro profile of this compound,the growth of cells expressing activated ABL protein tyrosine kinases was inhibited in the absence of exogenous growth factor. Growth inhibition was also observed with a p185BCR-ABL-positive acute lymphocytic leukemia (ALL) cell line generated from a Philadelphia chromosome-positive ALL patient. As CGP 57148 inhibits the PDGFR kinase,we also showed that cells expressing an activated PDGFR tyrosine kinase,TEL-PDGFR,are sensitive to this compound. Thus,this compound may be useful for the treatment of a variety of BCR-ABL-positive leukemias and for treatment of the subset of chronic myelomonocytic leukemia patients with a TEL-PDGFR fusion protein. View Publication

Mitomycin C,an important antitumor drug and antibiotic,has an extraordinary ability to crosslink DNA with high efficiency and absolute specificity for the sequence CpG. Recent results have shown how mitomycin C crosslinks DNA,and why the sequence specificity is so complete. This new understanding may allow the design of agents that mimic mitomycin C's economy of structure and can crosslink other sequences. View Publication

Peripheral blood progenitor cells (PBPCs) are increasingly used instead of bone marrow for autologous or allogeneic transplantation. In this study PBPCs mobilized in cancer patients by chemotherapy and granulocyte-colony stimulating factor were collected by apheresis and first enriched by immunoaffinity removal of lineage positive cells. When these cells were exposed to both cyclophosphamide and taxol or cultured for 7 days in the presence of 5-fluorouracil,stem cell factor,and interleukin-3,88% to 93% of the enriched PBPCs were killed and short-term clonogenic capacity in methylcellulose assays was lost,but week-5 cobblestone area-forming cell (CAFC) enrichment was higher than 10-fold in comparison to enriched PBPCs and higher than 700-fold in comparison to unmanipulated apheresis cells. After drug exposure,most of the progenitors displayed a CD34+,CD38-,multidrug-resistance (MDR+),Rhodamine 123 low,Hoechst 33342 low phenotype,and as few as 180 of these drug-resistant cells were able to generate a stable multilineage human hematopoiesis in sublethally irradiated immunodeficient mice. In these animals,the level of human hematopoietic engraftment was significantly increased by cotransplantation of irradiated cells from the human L87/4 stromal cell line. These observations are consistent with the functional isolation of a population of very early hematopoietic progenitors and might help to design new protocols for the removal of neoplastic cells from autografts. View Publication

We compared glucocorticoid receptor binding characteristics and glucocorticoid responsiveness of human mononuclear leukocytes (HML) from hypertensive patients and matched normotensive volunteers. We also considered associations of these variables with plasma renin activity,aldosterone,cortisol,corticotropin,and electrolyte concentrations. We calculated binding affinity (Kd; nmol/L) and capacity (Bmax; sites/cell) for dexamethasone and cortisol from homologous and heterologous competition curves for specific [3H]dexamethasone binding sites on HML isolated from the blood of normotensive volunteers and subjects with essential hypertension. Glucocorticoid responsiveness of HML was evaluated as IC50 values (nmol/L) for dexamethasone and cortisol for the inhibition of lysozyme release. We measured plasma hormones by radioimmunoassay. Kd values (mean+/-SE) for cortisol in HML of hypertensive patients were higher than in control subjects (24.6+/-2.4 versus 17.5+/-1.7 nmol/L,Ptextless.04). Binding capacity (4978+/-391 versus 4131+/-321 sites/cell),Kd values for dexamethasone (6.7+/-0.5 versus 5.7+/-0.3 nmol/L),and IC50 values for dexamethasone (3.4+/-0.3 versus 3.1+/-0.2 nmol/L) and cortisol (12.2+/-1.6 versus 9.5+/-0.3 nmol/L) were not significantly different. Patients with renin values less than 0.13 ng angiotensin I/L per second were markedly less sensitive to cortisol than those with higher values. Both Kd (30.3+/-2.5 versus 19.2+/-2.4 nmol/L) and IC50 values (15.5+/-1.8 versus 8.9+/-1.2 nmol/L) for cortisol were significantly higher in patients with lower renin values (Ptextless.03). Other variables,including plasma hormone and electrolyte values and binding characteristics for dexamethasone,were not different. These data suggest that cortisol binding to glucocorticoid receptor is slightly impaired in patients with essential hypertension. In vivo,this could lead to inappropriate binding of cortisol to mineralocorticoid receptors. Hence,decreased sensitivity to cortisol is associated with renin suppression. This hypothesis is supported by evidence of hypertension and low renin activity,which others have described in patients with primary glucocorticoid resistance due to mutations of the glucocorticoid receptor. View Publication