Evidence for a role of RUNX1 as recombinase cofactor for TCRβ rearrangements and pathological deletions in ETV6-RUNX1 ALL

T-cell receptor gene beta (TCRβ) gene rearrangement represents a complex, tightly regulated molecular mechanism involving excision, deletion and recombination of DNA during T-cell development. RUNX1, a well-known transcription factor for T-cell differentiation, has recently been described to act in addition as a recombinase cofactor for TCRδ gene rearrangements. In this work we employed a RUNX1 knock-out mouse model and demonstrate by deep TCRβ sequencing, immunostaining and chromatin immunoprecipitation that RUNX1 binds to the initiation site of TCRβ rearrangement and its homozygous inactivation induces severe structural changes of the rearranged TCRβ gene, whereas heterozygous inactivation has almost no impact. To compare the mouse model results to the situation in Acute Lymphoblastic Leukemia (ALL) we analyzed TCRβ gene rearrangements in T-ALL samples harboring heterozygous Runx1 mutations. Comparable to the Runx1+/- mouse model, heterozygous Runx1 mutations in T-ALL patients displayed no detectable impact on TCRβ rearrangements. Furthermore, we reanalyzed published sequence data from recurrent deletion borders of ALL patients carrying an ETV6-RUNX1 translocation. RUNX1 motifs were significantly overrepresented at the deletion ends arguing for a role of RUNX1 in the deletion mechanism. Collectively, our data imply a role of RUNX1 as recombinase cofactor for both physiological and aberrant deletions.

Silencing AML1-ETO gene expression leads to simultaneous activation of both pro-apoptotic and proliferation signaling

The t(8;21)(q22;q22) rearrangement represents the most common chromosomal translocation in acute myeloid leukemia (AML). It results in a transcript encoding for the fusion protein AML1-ETO (AE) with transcription factor activity. AE is considered to be an attractive target for treating t(8;21) leukemia. However, AE expression alone is insufficient to cause transformation, and thus the potential of such therapy remains unclear. Several genes are deregulated in AML cells, including KIT that encodes a tyrosine kinase receptor. Here, we show that AML cells transduced with short hairpin RNA vector targeting AE mRNAs have a dramatic decrease in growth rate that is caused by induction of apoptosis and deregulation of the cell cycle. A reduction in KIT mRNA levels was also observed in AE-silenced cells, but silencing KIT expression reduced cell growth but did not induce apoptosis. Transcription profiling of cells that escape cell death revealed activation of a number of signaling pathways involved in cell survival and proliferation. In particular, we find that the extracellular signal-regulated kinase 2 (ERK2; also known as mitogen-activated protein kinase 1 (MAPK1)) protein could mediate activation of 23 out of 29 (79%) of these upregulated pathways and thus may be regarded as the key player in establishing the t(8;21)-positive leukemic cells resistant to AE suppression.

[Universal modular system for in vitro screening of potential inhibitors of HIV-1 replication]

Here we describe a system based on recombinant lentiviral vectors for the safe screening of potential anti-HIV drugs. The system allows to evaluate the sensitivity of HIVl-1 reverse transcriptase and integrase (wild-type as well as mutant forms of these enzymes detected in drug-resistant virus isolates) towards different drugs and substances, but also to screen inhibitors of other stages of HIV-1 life cycle.

[Expression of FLT3-ITD oncogene confers mice progenitor B-cells BAF3 sensitivity to the ribonuclease binase cytotoxic action]

Acute myeloid leukemia is the most common acute leukemia affecting adults, and its incidence increases with age. Along with chromosomal translocations in leukemic cells mutations in the genes of receptor tyrosine kinases KIT and FLT3 were found with a high frequency. Here we show that transgenic progenitor of B-cells BAF3/FLT3-ITD are much more sensitive to the ribonuclease binase cytotoxic effects than the original BAF3 cells. The principal difference between BAF3/FLT3-ITD and the original BAF3 cells is the expression of FLT3-ITD oncogene, which leads to a change in the normal cell signaling pathways. Earlier, we described a similar effect for the cytotoxic action of binase on Kasumi-1 and FDC-P1-N822K cells, which express the activated KIT-N822K oncogene. Increased binase cytotoxicity toward the cells, expressing FLT3-ITD oncogene, suggests that, as in the case of FDC-P1 cells, transduced by KIT oncogene, the expression of an activated oncogene determines the sensitivity of cells to binase.

[Replication-competent γ-retrovirus Mo-MuLV expressing green fluorescent protein gene as an efficient tool for screening of inhibitors of retroviruses that use heparan sulfate as the primary cell receptor]

The effect of sulfated polysaccharides on the efficiency of infection of mouse embryonic fibroblast cell lines SC-1 and NIH-3T3 by replication-competent recombinant Moloney murine leukemia virus (Mo-MuLV) carrying the eGFP gene was investigated. It was shown that used polysaccharides have no cytostatic and cytotoxic effects on SC-1 and NIH 3T3 cells inthe concentrations from 0.01 to 100 μg/ml and have virucidal activity against Mo-MuLV. Polysaccharides in the indicated concentrations inhibit cell infection by Mo-MuLV, that prevents further expansion of viral infection. It was detected that sulfated polysaccharides are effective inhibitors of other retroviruses, including lentiviruses, that use heparan sulfate as cell receptors for non-specific binding.

[Modulation of activated oncogene c-kit expression with RNA-interference]

Hyperexpression of oncogene c-kit is found in 80% patients with acute myeloid leukemia (AML). The transgenic model cell line expressing the oncogene c-kit was obtained by transduction with recombinant retrovirus. We have designed small interfering RNAs (siRNA) efficiently suppressing the expression of activated oncogene c-kit. Further small hairpin RNAs (shRNA) targeting c-kit mRNA were designed and expressed in lentiviral vectors. We report a stable reduction in c-kit expression following the introduction of shRNAs into model cells as well as Kasumi-1 cells from the patient with AML.

Screening of Potential HIV-1 Inhibitors/Replication Blockers Using Secure Lentiviral in Vitro System

The development and usage of safe cell systems for testing agents which possess anti-HIV activity is a very important factor in the design of new drugs. We have described in detail a system we designed that is based on lentiviral vectors (Prokofjeva et. al.,Antiviral Therapy,in print) for swift and completely safe screening of potential HIV-1 replication inhibitors. The system enables one to test the efficiency of the inhibitory activity of compounds whose action is directed towards either wild-type HIV-1 reverse transcriptase or integrase, or mutant enzymes corresponding to the drug-resistant virus form. Testing results of a number of already known drugs, which correlate well with published data as well as data on newly synthesized compounds, were obtained. Application of this system substantially broadens the possibilities of preclinical anti-HIV drugs testing.

[Downregulation of activated leukemic oncogenes AML1-ETO and RUNX1(K83N) expression with RNA-interference]

In the present study we have applied the siRNA approach for substantial reduction of AML1-ETO and RUNX1 (K83N) expression, which are frequently found in the leukemic cells. We have designed small hairpin RNAs (shRNA) for targeting AML1-ETO oncogene and a region close to the 5'-untranslated region of mRNA for the mutant RUNX1 (K83N) oncogene and expressed the shRNAs in lentiviral vectors. We report a stable reduction in expression of the oncogenes following the introduction of shRNAs into cells.

Murine endogenous retroviruses

Up to 10% of the mouse genome is comprised of endogenous retrovirus (ERV) sequences, and most represent the remains of ancient germ line infections. Our knowledge of the three distinct classes of ERVs is inversely correlated with their copy number, and their characterization has benefited from the availability of divergent wild mouse species and subspecies, and from ongoing analysis of the Mus genome sequence. In contrast to human ERVs, which are nearly all extinct, active mouse ERVs can still be found in all three ERV classes. The distribution and diversity of ERVs has been shaped by host-virus interactions over the course of evolution, but ERVs have also been pivotal in shaping the mouse genome by altering host genes through insertional mutagenesis, by adding novel regulatory and coding sequences, and by their co-option by host cells as retroviral resistance genes. We review mechanisms by which an adaptive coexistence has evolved. (Part of a multi-author review).

Gadd45 beta is a pro-survival factor associated with stress-resistant tumors

Tumors that acquire resistance against death stimuli constitute a severe problem in the context of cancer therapy. To determine genetic alterations that favor the development of stress-resistant tumors in vivo, we took advantage of polyclonal tumors generated after retroviral infection of newborn Elambda-MYC mice, in which the retroviral integration acts as a mutagen to enhance tumor progression. Tumor cells were cultivated ex vivo and exposed to gamma-irradiation prior to their transplantation into syngenic recipients, thereby providing a strong selective pressure for pro-survival mutations. Secondary tumors developing from stress-resistant tumor stem cells were analysed for retroviral integration sites to reveal candidate genes whose dysregulation confer survival. In addition to the gene encoding the antiapoptotic Bcl-x(L) protein, we identified the gadd45b locus to be a novel common integration site in these tumors, leading to enhanced expression. In accord with a thus far undocumented role of Gadd45beta in tumorigenesis, we showed that NIH3T3 cells overexpressing Gadd45beta form tumors in NOD/SCID mice. Interestingly and differently to other known 'classical' antiapoptotic factors, high Gadd45beta levels did not protect against MYC-, UV- or gamma-irradiation-induced apoptosis, but conferred a strong and specific survival advantage to serum withdrawal.

Gene transfer of SHIP-1 inhibits proliferation of juvenile myelomonocytic leukemia cells carrying KRAS2 or PTPN11 mutations

Juvenile myelomonocytic leukemia (JMML) is a malignant disease of early childhood characterized by a hypersensitivity to granulocyte/macrophage colony-stimulating factor (GM-CSF). Mutations in RAS or PTPN11 are frequently detected in JMML patients. The SH2-containing inositol 5-phosphatase 1 (SHIP-1) is a negative regulator of GM-CSF signaling, and inactivation of SHIP-1 in mice results in a myeloproliferative disease. Here, we report the effects of SHIP-1 expression on GM-CSF-dependent proliferation and colony formation of human hematopoietic cells. After retroviral-mediated transduction of SHIP-1 into CD34+ cells from cord blood of healthy newborns or peripheral blood of JMML patients carrying mutations in KRAS2 or PTPN11, we observed a reduction in GM-CSF-dependent proliferation and colony formation. An enzymatically inactive form of SHIP-1 (D672A) had no effect. These data indicate that SHIP-1 can effectively block GM-CSF hypersensitivity in JMML progenitor cells with mutations in KRAS2 or PTPN11 and may be a useful approach for the treatment of JMML patients.

Ethical issues identified by rehabilitation clinicians

OBJECTIVES

To quantify systematically and to characterize the range of ethics issues affecting rehabilitation professionals' day-to-day clinical practice, and to assess the preferences of rehabilitation clinicians for ethics education.

DESIGN

Survey of clinicians and admitting office personnel in an acute rehabilitation hospital with open-ended questions about the ethical issues they found most troubling in daily practice.

SETTING

A 175-bed free-standing, urban rehabilitation hospital.

PARTICIPANTS

A total of 411 clinicians and admitting office personnel, of whom 217 responded (53%) and generated a total of 547 ethics issues.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Ethical issues were coded by 2 independent raters into 24 different categories and a reconciliation session was used to resolve discrepancies.

RESULTS

The largest response (24%) was categorized as pressures resulting from health care reimbursement changes. The second most common problem (17%) involved conflicts among patients, physicians, team members, or families around goal setting. Difficulty assessing decision-making capacity was third (7%). The respondents favored discussion groups or interdisciplinary in-services and lectures over self-instructional materials as formats for ethics education.

CONCLUSIONS

Ethical issues in the rehabilitation setting are common, and reflect both the dynamic nature of the health care environment and the team model of care. Ongoing, interactive educational interventions are warranted to address these issues.

The Mus cervicolor MuLV isolate M813 is highly fusogenic and induces a T-cell lymphoma associated with large multinucleated cells

M813 is a type-C murine leukemia virus (MuLV) isolated from the Asian rodent Mus cervicolor. We have recently demonstrated that M813 defines a distinct MuLV receptor interference group. Here we show that M813 rapidly induces fusion of MuLV-expressing fibroblasts from "without," with syncytia being observed within 1 h after exposure to virus. Infection of fibroblasts with MuLV from all tested receptor-interference groups imparts susceptibility to M813-induced fusion, provided the cells also express the M813 receptor. Syncytium induction is also observed in vivo; mice infected with M813 develop a peripheral T-cell lymphoma, which is associated with large multinucleated cells of macrophage origin. A recombinant Moloney MuLV/M813 chimeric virus demonstrated that syncytium induction is a function of the Env SU protein. We postulate that the highly fusogenic property of M813 is attributable to either its unique receptor usage or sequences in the proline-rich domain of the Env protein.

Not ready for hospice: characteristics of patients in a pre-hospice program

CONTEXT

There are many patients with terminal illness for whom hospice care would be appropriate, but they either never enroll or enroll very late. In a pre-hospice program designed to help patients make the transition into hospice, we observed that many patients did not make the transition.

OBJECTIVES

To understand more about the transition to hospice and the functions of a pre-hospice program, this paper compares patients who enrolled in hospice with those who died in the pre-hospice program.

DESIGN, SETTING, AND PATIENTS

Data were collected from a retrospective review of the charts of 123 consecutive patients who enrolled in a prehospice program between January 1, 1995, and December 31, 1996.

MAIN OUTCOME MEASURES

The patient's decision to transfer to home hospice or (perhaps, by not making a decision) to remain enrolled in the pre-hospice program until death.

RESULTS

At the end of the research period, 38 patients had transferred to hospice and 36 had died without transfer. The remaining 49 patients had uncertain outcomes at the end of the research period. Patients who transferred to hospice were older (P = .02) and more likely to have secondary insurance (P = .05). In addition, those who enrolled in hospice were more likely to live alone (P = .03) and have psychosocial concerns noted by staff on admission (P = .05).

CONCLUSIONS

Many patients died in this program that was designed only for transition to hospice. We found statistically significant differences characterizing the groups associated with transferring to hospice. Further studies to find out why these differences exist will be important in order to provide excellent end-of-life care for more people.

Functional identification of secondary mutations inducing autonomous growth in synergy with a truncated interleukin-3 receptor Implications for multi-step oncogenesis

OBJECTIVE

A truncated common beta chain (Deltabeta(C)) of the interleukin-3 (IL-3) receptor complex was previously identified as a key factor in inducing autonomous growth of IL-3-independent mutants. Expression of Deltabeta(C) in IL-3-dependent hematopoietic cells does not result in immediate factor-independent growth, but increases the frequency of obtaining autonomous mutants by three to four orders of magnitude. This study was designed to delineate the mechanisms by which Deltabeta(C) increases the frequency to autonomous growth.

DESIGN AND METHODS

Retroviral vectors were used to express Deltabeta(C) into IL-3-dependent myeloid cells, which were then tested for factor-independent growth. To determine if secondary genetic events were required for conversion to autonomous growth, elements of the Cre-loxP recombinant system were used to excise Deltabeta(C) in factor-independent clones.

RESULTS

Excision of Deltabeta(C) in factor-independent clones revealed two types of phenotypes: reversion to factor-dependent growth (1/8) or continued IL-3-dependent growth (7/8). Analysis of cells that remained factor independent revealed constitutive activation of STAT5, not observed in factor-dependent revertants. Analysis of revertant cells demonstrated the presence of interacting secondary mutations that synergize with Deltabeta(C)-induced proliferation. A cysteine residue within the truncated extracellular domain of Deltabeta(C) was also found to be required for its oncogenic potential, supporting a model of dimerization for receptor activation.

CONCLUSIONS

The high incidence of obtaining factor-independent mutants from cells expressing Deltabeta(C) results from the selection of mutations that either complement Deltabeta(C) expression to promote proliferation or that singly or in synergy with other secondary mutations negate the requirement of Deltabeta(C) expression for proliferation.

Mus cervicolor murine leukemia virus isolate M813 belongs to a unique receptor interference group

Murine leukemia virus (MuLV) M813 was originally isolated from the Southeast Asian rodent Mus cervicolor. As with the ecotropic MuLVs derived from Mus musculus, its host range is limited to rodent cells. Earlier studies have mapped its receptor to chromosome 2, but it has not been established whether M813 shares a common receptor with any other MuLVs. In this study, we have performed interference assays with M813 and viruses from four interference groups of MuLV. The infection efficiency of M813 was not compromised in cells expressing any one of the other MuLVs, demonstrating that M813 must use a distinct receptor for cell entry. The entire M813 env coding region was molecularly cloned. Sequence analysis revealed high similarity with other MuLVs but with a unique receptor-binding domain. Substitution of M813 env sequences in Moloney MuLV resulted in a replication-competent virus with a host range and interference profile similar to those of the biological clone M813. M813 thus defines a novel receptor interference group of type C MuLVs.

Insertional mutagenesis of preneoplastic astrocytes by Moloney murine leukemia virus

Retroviral infection can induce transcriptional activation of genes flanking the sites of proviral integration in target cells. Because integration is essentially random, this phenomenon can be exploited for random mutagenesis of the genome, and analysis of integration sites in tumors may identify potential oncogenes. Here we have investigated this strategy in the context of astrocytoma progression. Neuroectodermal explants from astrocytoma-prone GFAP-v-src transgenic mice were infected with the ecotropic Moloney murine leukemia virus (Mo-MuLV). In situ hybridization and FACS analysis indicated that astrocytes from E12.5-13.5 embryos were highly susceptible to retroviral infection and expressed viral RNA and proteins both in vitro and in vivo. In average 80% of neuroectodermal cells were infected in vitro with 9-14 proviral integrations per cell. Virus mobility assays confirmed that Mo-MuLV remained transcriptionally active and replicating in neuroectodermal primary cultures even after 45 days of cultivation. Proviral insertion sites were investigated by inverse long-range PCR. Analysis of a limited number of provirus flanking sequences in clones originated from in vitro infected GFAP-v-src neuroectodermal cells identified loci of possible relevance to tumorigenesis. Therefore, the approach described here might be suitable for acceleration of tumorigenesis in preneoplastic astrocytes. We expect this method to be useful for identifying genes involved in astrocytoma development/progression in animal models.

The inositol 5-phosphatase SHIP is expressed as 145 and 135 kDa proteins in blood and bone marrow cells in vivo, whereas carboxyl-truncated forms of SHIP are generated by proteolytic cleavage in vitro

The inositol polyphosphate 5-phosphatase SHIP plays an important role in negative signalling in B cells and mast cells and in the down-regulation of cytokine receptor-mediated signals in myeloid cells. SHIP is expressed as a 145 kDa full-length protein and an isoform of 135 kDa due to alternative splicing. Additional smaller forms of SHIP which are truncated at the carboxy terminus have been described in bone marrow and peripheral blood mononuclear cells (PBMC). Our data demonstrate that human bone marrow cells and PBMC from healthy donors and patients with acute myeloid leukemia express the 145 kDa form of SHIP and low amounts of a 135 kDa form of SHIP in vivo whereas C-terminal-truncated SHIP proteins are generated by a PMSF-sensitive protease during the preparation of cell lysates in vitro. We have further characterized this protease and identified a proteolytic cleavage site in the human SHIP protein C-terminal to tryptophan residue 941. These data support a physiological role for the 145 and 135 kDa forms of SHIP in bone marrow and peripheral blood cells from normal donors and patients with acute myeloid leukemia.

Lack of functional Pit-1 and Pit-2 expression on hematopoietic stem cell lines

Hematopoietic stem cells (HSC) are an important target for retroviral gene transfer. However, transduction efficiency in these HSC is extremely low compared to fibroblasts or more mature hematopoietic cells. This infection block was analyzed in the HSC line FDC-Pmix. The infection frequency with the amphotropic murine leukemia virus (MLV-A) is more than 100-fold lower in FDC-Pmix cells as compared to fibroblasts. Pseudotyping with the env of the 10A1 strain (MLV-10A1), which uses both the amphotropic receptor (Pit-2) and the receptor for gibbon ape leukemia virus (Pit-1), did not improve the infection efficiency. Vectors pseudotyped with VSV G protein were found to overcome the infection block in FDC-Pmix, confirming that the block is at the level of virus binding and possibly penetration. Accordingly, we could not detect virus binding of MLV-A or MLV-10A1 to FDC-Pmix cell lines. Northern blot analysis was performed to detect whether the defect is at the level of transcription. Surprisingly, similar levels of Pit-2 receptor transcripts were detected in all cell types. The overexpression of rat Pit-2 DNA in CHO but not in FDC-Pmix cells improved amphotropic infection frequency after introducing rat Pit-2 DNA into the cells. Taken together these results show that the inefficient infection of FDC-Pmix is due to a lack of functional receptors. Either the receptor protein is incorrectly processed in these cells or a cofactor is missing in FDC-Pmix cells that is necessary for efficient binding and/or penetration.

Transcriptional activation of the granulocyte-macrophage colony-stimulating factor receptor gene in cell mutants

Retroviral insertional mutagenesis has proven to be a powerful in vivo approach for identifying genetic mutations involved in tumorigenesis or developmental abnormalities. Applying this approach to an in vitro system, where experimental design can be readily manipulated, would greatly increase its efficacy. In this study, we sought to determine whether retroviral insertional mutagenesis could be used to isolate cell mutants, in which the transcriptional activation of a receptor gene has occurred. Cells of the myeloid progenitor cell line FDC-P1(M), which do not express the alpha receptor subunit (GMRalpha) for granulocyte-macrophage colony-stimulating factor (GM-CSF), were infected and selected for growth in GM-CSF. Over 100 mutants were isolated at a frequency up to ninefold higher than that of uninfected controls. Expression of GMRalpha in these mutants was confirmed by blocking proliferation with GM-CSF antibodies, detection of high-affinity receptors, and Northern blot analysis. Significantly, in 7/18 mutants analyzed, gross DNA rearrangements had occurred in the GMRalpha locus. These rearrangements were demonstrated to be due to intergenic rearrangements, juxtaposing an active enhancer/promoter upstream of the GMRalpha gene. In one mutant it could be demonstrated that the wild-type allele was also expressed, providing evidence that secondary mutations had occurred. The implications of these results for retroviral insertional mutagenesis are discussed.

Effect of estradiol on insulin secreting INS-1 cells overexpressing estrogen receptors

BACKGROUND

Estrogen has been shown to have profound effects on insulin and glucose metabolism in vivo. Indeed, estrogens were recently shown to modulate ion channel and secretory activities in endocrine cells.

DESIGN AND METHODS

To investigate whether estrogenic influences are caused by direct effects on pancreatic beta-cells, we equipped INS-1 insulinoma cells with estrogen receptors and monitored insulin content and Ca(2+) fluxes as well as basal and stimulated insulin secretion upon different stimuli including glucose, the Ca(2+) ionophore ionomycin, the Ca(2+) channel agonist BayK8644, the protein kinase C activator TPA, and the adenylate cyclase activator forskolin.

RESULTS AND CONCLUSION

Our data reveal that estradiol has no significant direct effect on proliferation rate, insulin content, basal and stimulated insulin output as well as Ca(2+) fluxes of insulin secreting cells in vitro, indicating that in vivo responses to estrogen on insulin and glucose metabolism result from indirect betacytotropic effects.

Patients' priorities among treatment effects in head and neck cancer: evaluation of a new assessment tool

BACKGROUND

Patients with head and neck cancer may face decisions between surgery or radiation (with or without chemotherapy) which involve significant trade-offs in functional outcomes. This preliminary investigation is designed to examine patients' priorities among the effects of treatments for head and neck cancer.

METHODS

A new instrument designed to allow patients to rank personal priorities among 12 treatment effects was developed and tested. A cross section of patients (19) from pretreatment and posttreatment time periods and 23 controls participated.

RESULTS

Preliminary findings indicate high individual variability, with some differences between groups according to treatment time. Differences between patients and controls are evident. We report test-retest reliability and the limitations of this new tool.

CONCLUSIONS

The data suggest that measures of health state values should be conducted with patients rather than healthy volunteers. Patients' priorities may be influenced by treatment and some values may be more susceptible to change with experience of treatment effects. This new tool may provide insight into how patients' prioritize the anticipated and experienced effects of treatment for head and neck cancers.

Murine leukemia virus recombinants that use phosphate transporters for cell entry induce similar spongiform encephalomyelopathies in newborn mice

Amphotropic Moloney-murine leukemia virus recombinants (Mo-AmphoV) induce a severe spongiform encephalomyelopathy in newborn mice. We show here that a coisogenic recombinant with a 10A1-MuLV host range (Mo-10A1V) also induces a neurodegenerative disease, clinically characterized by mild tremor and ataxia. Spongiform lesions are most severe in the metencephalon and mesencephalon but extend into the prosencephalon and spinal cord. Significantly, the quality of histopathology was indistinguishable between Mo-AmphoV and Mo-10A1V, probably reflecting a final common pathogenic pathway. Common receptor use thus may be an important determinant in the pathogenicity of these viruses. These results have implications for the clinical use of retroviral pseudotypes that use phosphate transporters for cell entry.

Carboxyl-truncated STAT5beta is generated by a nucleus-associated serine protease in early hematopoietic progenitors

Hematopoiesis is tightly controlled by a family of cytokines that signal through a related set of receptors. The pleiotropic and overlapping response of a cell to different cytokines is reflected in the number and complex pattern of activated signal transducers. Of special interest is STAT5, which is stimulated by a large and diverse set of cytokines. In addition to the two highly homologous proteins, STAT5A and STAT5B, encoded by duplicated genes, expression and activation of a dominant-negative, carboxyl-truncated form has also been described in early hematopoietic progenitors. We show here that a protease expressed in early hematopoietic cells cleaves the alpha forms of STAT5A/5B (p96/p94) to generate carboxyl-truncated beta forms (p80/p77). Inhibition studies assigned this protease to the serine class of endopeptidases. Cell fractionation experiments showed that the protease is associated with the nucleus in a constitutively activated form and does not require an activated STAT5 substrate. The ability of a protease to modulate the specificity of an activated transcription factor is unprecedented and underlines the importance of proteases in regulation of cell functions.

Entry of amphotropic and 10A1 pseudotyped murine retroviruses is restricted in hematopoietic stem cell lines

Although transduction with amphotropic murine leukemia virus (MLV) vectors has been optimized successfully for hematopoietic differentiated progenitors, gene transfer to early hematopoietic cells (stem cells) is still highly restricted. A similar restriction to gene transfer was observed in the mouse stem cell line FDC-Pmix compared with transfer in the more mature myeloid precursor cell line FDC-P1 and the human erythroleukemia cell line K562. Gene transfer was not improved when the vector was pseudotyped with gp70SU of the 10A1 strain of MLV, which uses the receptor of the gibbon ape leukemia virus (Pit1), in addition to the amphotropic receptor (Pit2). Although 10A1 and amphotropic gp70SU bound to FDC-P1, K562, and fibroblasts, no binding to FDC-Pmix cells was detected. This indicates that FDC-Pmix cells lack functional Pit2 and Pit1 receptors. Pseudotyping with the vesicular stomatitis virus G protein improved transduction efficiency in FDC-Pmix stem cells by 2 orders of magnitude, to fibroblast levels, confirming a block to retroviral infection at the receptor level.

Host cis-mediated extinction of a retrovirus permissive for expression in embryonal stem cells during differentiation

The use of retroviral vectors for gene transfer into animals has been severely hampered by the lack of provirus transcription in the early embryo and embryonic stem (ES) cells. This primary block in provirus expression is maintained in differentiated cells by a cis-acting mechanism that is not well characterized. Retroviral vectors based on the murine embryonal stem cell virus (MESV), which overcome the transcriptional block in ES cells, were constructed to investigate this secondary mechanism. These vectors transferred G418 resistance to ES cells with the same efficiency as to fibroblasts, but overall transcript levels were greatly reduced. A mosaic but stable expression pattern was observed when single cells from G418-resistant clones were replated in G418 or assayed for expression of LacZ or interleukin-3. The expression levels in independent clones were variable and correlated inversely with methylation. However, a second, more pronounced, block to transcription was found upon differentiation induction. Differentiation of the infected ES cells to cells permissive for retroviral expression resulted in repression and complete extinction of provirus expression. Extinction was not accompanied by increased levels of methylation. Provirus expression is thus regulated by two independent cis-acting mechanisms: (i) partial repression in the undifferentiated state, accompanied by increased methylation but compatible with long-term, low expression of retroviral genes, and (ii) total repression and extinction during early stages of differentiation, apparently independent of changes in methylation. These results indicate a time window early during the transition from an undifferentiated to a differentiated stage in which provirus expression is silenced. The mechanisms are presently unknown, but elucidation of these events will have an important impact on vector development for targeting stem cells and for gene therapy.

Gene transfer into haemopoietic cells

The therapeutic potential achievable by efficient transfer and expression of genes into haemopoietic stem cells (HSC) is enormous. In addition to inherited disorders such as haemoglobinopathies and lysosomal storage disorders, this technology can be applied to acquired disorders such as myelosuppression induced by anticancer chemotherapy or infection with human immunodeficiency virus (HIV). To date retroviral vectors are the most attractive modality for gene transfer into HSC. Unfortunately, the expectations of gene therapy are more advanced than the methodology needed to fulfil the goals. In this chapter, the current concepts and limitations in the genetic manipulation of haemopoietic cells are presented. Overcoming these limitations requires not only improvement in isolation and expansion of HSC that contribute to long-term repopulation, but also development of better retroviral transfer systems. Current restrictions occur at various levels in the viral transfer process, including efficient cell entry, regulated expression levels, and sustained expression. The analysis of retroviral mutants has proven to be a successful approach to developing effective retroviral vectors for HSC gene therapy.

Amphotropic murine leukemia viruses induce spongiform encephalomyelopathy

Recombinants of amphotropic murine leukemia virus (A-MuLV) have found widespread use in retroviral vector systems due to their ability to efficiently and stably infect cells of several different species, including human. Previous work has shown that replication-competent recombinants containing the amphotropic env gene, encoding the major SU envelope glycoprotein that determines host tropism, induce lymphomas in vivo. We show here that these viruses also induce a spongiform encephalomyelopathy in mice inoculated perinatally. This fatal central nervous system disease is characterized by noninflammatory spongiform lesions of nerve and glial cells and their processes, and is associated with moderate astro- and microgliosis. The first clinical symptoms are ataxia, tremor, and spasticity, progressing to complete tetraparesis and incontinence, and finally death of the animal. Sequences within the amphotropic env gene are necessary for disease induction. Coinfection of A-MuLV recombinants with nonneuropathogenic ecotropic or polytropic MuLV drastically increases the incidence, degree, and distribution of the neurodegenerative disorder. The consequence of these results in view of the use of A-MuLV recombinants in the clinic is discussed.

An alternative strategy for studying adverse events in medical care

BACKGROUND

Data about the frequency of adverse events related to inappropriate care in hospitals come from studies of medical records as if they represented a true record of adverse events. In a prospective, observational design we analysed discussion of adverse events during the care of all patients admitted to three units of a large, urban teaching hospital affiliated to a university medical school. Discussion took place during routine clinical meetings. We undertook the study to enhance understanding of the incidence and scope of adverse events as a basis for preventing them.

METHODS

Ethnographers trained in qualitative observational research attended day-shift, weekday, regularly scheduled attending rounds, residents' work rounds, nursing shift changes, case conferences, and other scheduled meetings in three study units as well as various departmental and section meetings. They recorded all adverse events during patient care discussed at these meetings and developed a classification scheme to code the data. Data were collected about health-care providers' own assessments about the appropriateness of the care that patients received to assess the nature and impact of adverse events and how health-care providers and patients responded to the adverse events.

FINDINGS

Of the 1047 patients in the study, 185 (17.7%) were said to have had at least one serious adverse event; having an initial event was linked to the seriousness of the patient's underlying illness. Patients with long stays in hospital had more adverse events than those with short stays. The likelihood of experiencing an adverse event increased about 6% for each day of hospital stay, 37.8% of adverse events were caused by an individual, 15.6% had interactive causes, and 9.8% were due to administrative decisions. Although 17.7% of patients experienced serious events that led to longer hospital stays and increased costs to the patients, only 1.2% (13) of the 1047 patients made claims for compensation.

INTERPRETATION

This study shows that there is a wide range of potential causes of adverse events that should be considered, and that careful attention must be paid to errors with interactive or administrative causes. Healthcare providers' own discussions of adverse events can be a good source of data for proactive error prevention.

[Will transfer of cytostatic drug resistance genes increase hematopoiesis resistance in the treatment of malignant tumors?]

The aim of aggressive antitumor chemotherapy is to kill the tumor with the largest possible dose of a cytotoxic drug. The maximum dose tolerated by the patient is limited by the toxicity to normal tissue, hematopoiesis being frequently the most sensitive system. Transfer of drug resistance genes to hematopoietic cells could protect them against chemotherapy-related toxicity and thus could be a way of gene therapy in cancer. Methylating and chloroethylating derivatives of nitrosourea are effective anticancer drugs, however, acute hematopoietic toxicity and late risk of leukemia are serious side effects. The major lesion responsible for toxic and mutagenic effects of alkylnitrosoureas is O6-alkylation of guanine in DNA. This lesion is specifically repaired by O6-alkylguanine-DNA-alkyltransferase and hematopoietic cells can be protected against toxic and mutagenic effect of nitrosoureas by alkyltransferase gene transfer. Endogenous alkyltransferase in tumor tissue could be inactivated by administration of O6-benzylguanine, while hematopoietic cells could still be chemoprotected by inhibitor-resistant alkyltransferase gene transfer. This approach could increase the therapeutic efficacy of nitrosoureas in gene therapy augmented cancer treatment.

Effects of organizational change in the medical intensive care unit of a teaching hospital: a comparison of 'open' and 'closed' formats

OBJECTIVE

To compare the effects of change from an open to a closed intensive care unit (ICU) format on clinical outcomes, resource utilization, teaching, and perceptions regarding quality of care.

DESIGN

Prospective cohort study; prospective economic evaluation.

SETTING

Medical ICU at a university-based tertiary care center. For the open ICU, primary admitting physicians direct care of patients with input from critical care specialists via consultation. For the closed ICU, critical care specialists direct patient care.

PATIENTS

Consecutive samples of 124 patients admitted under an open ICU format and 121 patients admitted after changing to a closed ICU format. Readmissions were excluded.

MAIN OUTCOME MEASURES

Comparison of hospital mortality with mortality predicted by the Acute Physiology and Chronic Health Evaluation II (APACHE II) system; duration of mechanical ventilation; length of stay; patient charges for radiology, laboratory, and pharmacy departments; vascular catheter use; number of interruptions of formal teaching rounds; and perceptions of patients, families, physicians, and nurses regarding quality of care and ICU function.

RESULTS

Mean +/- SD APACHE II scores were 15.4 +/- 8.3 in the open ICU and 20.6 +/- 8.6 in the closed ICU (P=.001). In the closed ICU, the ratio of actual mortality (31.4 percent) to predicted mortality (40.1 percent) was 0.78. In the open ICU, the ratio of actual mortality (22.6 percent) to predicted mortality (25.2 percent) was 0.90. Mean length of stay for survivors in the open ICU was 3.9 days, and mean length of stay for survivors in the closed ICU was 3.7 days (P=.79). There were no significant differences between periods in patient charges for radiology, laboratory, or pharmacy resources. Nurses were more likely to say that they were very confident in the clinical judgment of the physician primarily responsible for patient care in the closed ICU compared with the open ICU (41 percent vs 7 percent; P<.Ol), and nurses were the group most supportive of changing to a closed ICU format before and after the study.

CONCLUSIONS

Based on comparison of actual to predicted mortality, changing from an open to a closed ICU format improved clinical outcome. Although patients in the closed ICU had greater severity of illness, resource utilization did not increase.

Physicians' attitudes about the care of patients in the persistent vegetative state: a national survey

OBJECTIVE

To study the attitudes and beliefs of physicians who have experience caring for patients in the persistent vegetative state (PVS).

DESIGN

Mailed questionnaire survey.

PARTICIPANTS

500 physicians, 250 from the American Academy of Neurology and 250 from the American Medical Directors Association.

MEASUREMENTS

Physicians' beliefs about diagnosis of the PVS, patient awareness and suffering, treatment withdrawal, appropriate use of health maintenance and life-prolonging therapies, organ donation, lethal injection, and the treatment they would want if they were in the PVS.

RESULTS

68% of surveyed neurologists and 60% of medical directors responded. Thirteen percent of responders believe that patients in the PVS have awareness and experience hunger and thirst; 30% believe they experience pain. Fewer than 9% believe that respiratory failure, cardiogenic shock, acute renal failure, or cancer should be aggressively treated. Eighty-nine percent believe that it is ethical to withdraw artificial hydration and nutrition. Almost two thirds of responders believe that it would be ethical to use the vital organs of patients in the PVS for transplantation, and 20% believe that it would be ethical to hasten the patient's death by lethal injection.

CONCLUSIONS

When evaluating the appropriateness of treatments for patients in the PVS, neurologists and medical directors largely concur. Most physicians in both groups believe that patients in the PVS would be better off dead; that it is not necessary to provide aggressive therapeutic interventions; and that all therapeutic interventions, including artificial nutrition and hydration, can be withheld in certain circumstances. The areas of consensus are remarkable and suggest that an ethical standard that physicians believe should be followed when caring for these patients may be emerging.

Long-term protection of hematopoiesis against the cytotoxic effects of multiple doses of nitrosourea by retrovirus-mediated expression of human O6-alkylguanine-DNA-alkyltransferase

A human O6-alkylguanine-DNA-alkyltransferase (ATase) cDNA-containing retrovirus was used to infect murine long-term primary bone marrow cultures. High levels of ATase expression were obtained, and colony-forming cells of the granulocyte-macrophage lineage from the cultures transduced with the human ATase retrovirus were three times more resistant to the alkylating agent, N-methyl-N-nitrosourea (MNU), than control cultures. Furthermore, expression of the human ATase protected long-term hematopoiesis, measured as the output of progenitor cells to the nonadherent fraction of the culture, against the cytotoxic effects of repeated exposures to MNU. These results clearly show that a human ATase cDNA-containing retrovirus can be used to infect long-term primary bone marrow cultures and that this attenuates their sensitivity to nitrosoureas.

Activity of Friend mink cell focus-forming retrovirus during myelo-erythroid hematopoiesis

Friend mink cell focus-forming (FMCF) viruses are recombinants between the Friend murine leukemia virus (F-MuLV) and endogenous polytropic retroviruses involved in a number of retrovirus-induced malignancies of the myelo-erythroid compartment. To analyze the contribution of the viral cis regulatory elements to the host range determinants within the hematopoietic system, we performed a series of marker gene experiments using both transient transfection and retroviral-mediated stable transduction of indicator cell lines representing distinct developmental stages. According to our data, the U3 region in the long terminal repeat (LTR) of FMCF viruses possesses an enhancer assembly that allows efficient transcription in both early and late myelo-erythroid stem and progenitor cells. Retroviral gene expression, however, is subjected to stage-dependent transcriptional controls during blood cell maturation. We obtained evidence that a repressor element overlapping with the primer binding site in the viral leader region compromises U3-mediated gene expression in a stage-dependent manner, with the strongest restriction observed in the most primitive cells analyzed, FDCP-mix. In addition, our data indicate a second hurdle for retroviral gene expression in early hematopoietic cells that is independent of the primer binding site and most likely related to inefficient utilization of U3-located enhancers. These data shed light on the mechanisms of host range restriction within the hematopoietic system and define a basis for the design of retroviral vectors aimed to overcome transcriptional inefficiency in early hematopoietic cells. Thus, we developed novel retroviral vectors combining FMCF-type U3 regions with a permissive leader from the murine embryonic stem cell virus. These vectors are highly efficient for gene transfer and expression in both early and late myelo-erythroid cells, indicating that they will be of great use for a variety of experimental and therapeutic applications.

The application of health care surrogate laws to older populations: how good a match?

OBJECTIVE

The Health Care Surrogate Act (HCSA) in Illinois has been proposed as a model for state laws naming surrogate medical decision-makers for those without advance directives (ADs). Our objective was to determine if the HCSA identifies the same surrogate as older persons would choose for themselves. If not, is the discrepancy between legally identified surrogate and preferred surrogate troublesome to respondents? Because it is documented that black Americans have a variety of family structures, some of which may not be reflected in the HCSA list, we also wished to determine if discrepancies between surrogates named by the law and those desired by patients are associated with black or white race.

DESIGN, SETTING AND PARTICIPANTS

A convenience sample of 144 patients aged 65 and older, without cognitive impairment, was interviewed at the geriatrics clinic of an academic medical center.

MAIN OUTCOME MEASURES

Respondents without ADs who had a different stated choice for surrogate medical decision-maker than the surrogate defined by the Illinois HCSA, based on their existing family.

RESULTS

Twenty-six percent of respondents without ADs chose a surrogate that differed from the surrogate defined by the HCSA. However, 67% of those with a different choice for surrogate than defined by law were not troubled by the discrepancy. The proportion of black subjects (25%) and white subjects (31%) who had surrogate discrepancies was not significantly different (P = .6).

CONCLUSION

Because the Illinois HCSA named surrogates who would be agreeable to the majority of our respondents, it appears that it may be a useful model for state surrogacy laws.

Novel retroviral vectors for efficient expression of the multidrug resistance (mdr-1) gene in early hematopoietic cells

We present data that retroviral gene expression in early hematopoietic cells is subjected to transcriptional controls similar to those previously described for embryonic stem cells. Transient transfection experiments revealed that both the viral enhancer region in the U3 region of the long terminal repeat as well as a repressor element coincident with the primer binding site of Moloney leukemia viruses are limiting for expression in hematopoietic cells in a differentiation-dependent manner. Within the group of Moloney leukemia virus-related viruses, only the myeloproliferative sarcoma virus showed high enhancer activity in myeloid (including erythroid) cells. In contrast, enhancer regions related to the Friend mink cell focus-forming viruses mediate much higher gene expression levels in both multipotent and lineage-committed myeloid cells. In addition, transcriptional repression related to sequences in the primer binding site of Moloney leukemia virus-derived vectors is also found in early hematopoietic cells and can be overcome by using the corresponding sequences of the murine embryonic stem cell virus. On the basis of these results, two types of novel retroviral hybrid vectors were developed; they combine the U3 regions of either the Friend mink cell focus-forming virus family or the myeloproliferative sarcoma virus with the primer binding site of the murine embryonic stem cell virus. When used to express the human multiple drug resistance gene, these vectors substantially improve protection to cytostatic drugs in transduced hematopoietic cell lines FDC-Pmix, TF-1, and K-562 in comparison with Moloney leukemia virus-derived vectors presently used for the stem cell protection approach in somatic gene therapy.

Perceptions of cancer patients and their physicians involved in phase I trials

PURPOSE

In an attempt to understand some of the complex issues related to the participation of cancer patients in phase I trials, and the perceptions of patients toward these trials, we conducted a pilot survey study of 30 cancer patients who had given informed consent to participate in a phase I trial at our institution. Concurrently, the oncologists identified by the surveyed patients as responsible for their care were surveyed as well.

PATIENTS AND METHODS

Twenty-seven of 30 consecutive patients agreed to and completed the survey. Patients were surveyed before they received any investigational agents. Eighteen oncologists participated in this survey study.

RESULTS

Eighty-five percent of patients decided to participate in a phase I trial for reasons of possible therapeutic benefit, 11% because of advice/trust of physicians, and 4% because of family pressures. Ninety-three percent said that they understood all (33%) or most (60%) of the information provided about the trials in which they had decided to participate. Only 33% were able to state the purpose of the trial in which they were participating, with patients able to state the purpose of phase I trials being more educated (P = .01). Surveyed oncologists had wide-ranging beliefs regarding expectations of possible benefits and toxicities for their patients participating in phase I trials.

CONCLUSION

Cancer patients who participate in phase I trials are strongly motivated by the hope of therapeutic benefit. Altruistic feelings appear to have a limited and inconsequential role in motivating patients to participate in these trials. Cancer patients who participate in phase I trials appear to have an adequate self-perceived knowledge of the risks of investigational agents. However, only a minority of patients appear to have an adequate understanding of the purpose of phase I trials as dose-escalation/dose-determination studies.

Sequential mutations in the interleukin-3 (IL3)/granulocyte-macrophage colony-stimulating factor/IL5 receptor beta-subunit genes are necessary for the complete conversion to growth autonomy mediated by a truncated beta C subunit

An amino-terminally truncated beta C receptor (beta C-R) subunit of the interleukin-3 (IL3)/granulocyte-macrophage colony-stimulating factor/IL5 receptor complex mediates factor-independent and tumorigenic growth in two spontaneous mutants of a promyelocytic cell line. The constitutive activation of the JAK2 protein kinase in these mutants confirms that signaling occurs through the truncated receptor protein. Noteworthily, in addition to a 10-kb deletion in the beta C-R subunit gene encoding the truncated receptor, several secondary and independent mutations that result in the deletion or functional inactivation of the allelic beta C-R subunit and the closely related beta IL3-R subunit genes were observed in both mutants, suggesting that such mutations are necessary for the full oncogenic penetrance of the truncated beta C-R subunit. Reversion of these mutations by the expression of the wild-type beta C-R in the two mutants resulted in a fivefold decrease in cloning efficiency of the mutants in the absence of IL3, confirming a functional interaction between the wild-type and truncated proteins. Furthermore, expression of the truncated beta C-R subunit in factor-dependent myeloid cells did not immediately render the cells autonomous but increased the spontaneous frequency to factor-independent growth by 4 orders of magnitude. Implications for both leukemogenic progression and receptor-subunit interaction and signaling are discussed.

The novel activation of ABL by fusion to an ets-related gene, TEL

In human leukemia, activation of the ABL proto-oncogene locus on chromosome 9 most commonly occurs as a result of its fusion to the BCR locus on chromosome 22. The resulting chimeric protein displays an elevated tyrosine kinase activity. We have identified a novel activation of ABL which involves a gene located on chromosome 12, designated TEL. Like BCR, TEL is fused in-frame with ABL and produces a fusion protein with an elevated tyrosine kinase activity when assayed in an immune complex. The amino-terminal sequences of TEL encode a helix-loop-helix motif which may mediate dimerization.

Mutants of a multipotent hematopoietic cell line blocked in GM-CSF-induced differentiation are leukemogenic in vivo

FDCP-Mix cells infected with a retroviral vector expressing the GM-CSF gene (GMV-FDCP-Mix) self-renew in the presence of interleukin-3 (IL-3), are multipotent, and undergo differentiation into granulocytes and macrophages coupled with clonal extinction after removal of IL-3. Mutants of GMV-FDCP-Mix were isolated that escape clonal extinction after differentiation induction by the autocrine secreted GM-CSF. Some of these mutant clones have a blast cell morphology and are blocked in differentiation, whereas others exhibit all stages of granulocyte and macrophage differentiation without clonal extinction. In contrast to the parental GMV-FDCP-Mix cells, all the mutants tested were leukemogenic when injected into syngeneic mice. Depending on the in vitro differentiation capacity of the transplanted mutant cell lines, the animals developed undifferentiated blast cell leukemias or CML-like syndromes. Thus, these mutant cell lines can be used to define the cooperating steps in autocrine myeloid leukemia.