E2F-1 potentiates cell death by blocking antiapoptotic signaling pathways

The E2F family of transcription factors plays an essential role in promoting cell cycle progression, and one member of the family, E2F-1, is also capable of inducing apoptosis. We show here that E2F-1 can induce apoptosis by a death receptor-dependent mechanism, by downregulating TRAF2 protein levels and inhibiting activation of antiapoptotic signals including NF-kappa B. In this way, E2F-1 expression can lead to the sensitization of cells to apoptosis by a number of agents independently of p53. Deregulation of E2F-1 activity occurs in the majority of human tumors, and the ability of E2F-1 to inhibit antiapoptotic signaling may contribute to the enhanced sensitivity of transformed cells to chemotherapeutic agents.

Expression of leading region genes on IncI1 plasmid ColIb-P9: genetic evidence for single-stranded DNA transcription

The leading region of a plasmid is the first sector to enter the recipient cell in bacterial conjugation. This sector of IncI1 plasmid ColIb-P9 includes genes that are transcribed in a transient pulse early in the conjugatively infected cell to promote establishment of the immigrant plasmid. Evidence is presented that the burst of gene expression is regulated by a process which is independent of a repressor but dependent on the orientation of the genes on the unique plasmid strand transferred in conjugation. The nucleotide sequence of 11.7 kb of the leading region was determined and found to contain 10 ORFs; all are orientated such that the template strand for transcription corresponds to the transferred strand. The leading region contains three dispersed repeats of a sequence homologous to a novel promoter in ssDNA described by H. Masai & K. Arai (1997, Cell 89, 897-907). It is proposed that the repeats are promoters that form in the transferring strand of ColIb to support transient transcription of genes transferred early in conjugation.

Recurrent venous thrombosis and heparin therapy: an evaluation of the importance of early activated partial thromboplastin times

BACKGROUND

The presence of an association between early subtherapeutic activated partial thromboplastin times (aPTTs) and recurrent venous thromboembolism (VTE) remains controversial.

OBJECTIVE

To determine the relation between early subtherapeutic aPTTs and recurrent VTE in patients who were treated with intravenous (i.v.) unfractionated heparin (UFH).

PATIENTS AND METHODS

We studied 961 patients with acute VTE who received i.v. UFH in 3 randomized trials that compared the use of i.v. UFH (loading dose: 5000 U i.v.; initial infusion, 1250-1280 U/h) with that of subcutaneous low-molecular-weight heparin. According to aPTT criteria, patients were classified as being in a subtherapeutic or a therapeutic state during the first 24 and 48 hours of treatment. All episodes of possible recurrent VTE were adjudicated by an independent committee that was unaware of the aPTTs.

RESULTS

At 24 hours, in 886 patients who were eligible for the analysis, the rate of recurrent VTE in the subtherapeutic group was 6.7% (11/163) compared with 5.3% (38/723) in the therapeutic group. The odds ratio for recurrence in patients in the subtherapeutic vs the therapeutic group at 24 hours was 1.30 (95% confidence interval: 0.64-2.63; P = .46). At 48 hours, in 917 patients who were eligible for the analysis, the rate of recurrent VTE in the subtherapeutic group was 7.8% (5/64) compared with 5.7% (49/853) in the therapeutic group. The odds ratio for recurrence in patients in the subtherapeutic vs the therapeutic group at 48 hours was 1.32 (95% confidence interval: 0.51-3.44; P = .56).

CONCLUSION

In patients with acute VTE who receive an i.v. bolus of 5000 U, followed by a starting dose of at least 1250 U/h of UFH, a subtherapeutic aPTT response during the first 48 hours of treatment is not associated with a large increase in the risk of recurrent VTE.

Mdm2 binds p73 alpha without targeting degradation

The function of the p53 tumor suppressor protein is regulated by interaction with Mdm2, which targets p53 for ubiquitin dependent degradation. We show here that like p53, p73 alpha forms an interaction with Mdm2, both in vitro and in cells, but this does not result in the degradation of the p73 alpha protein. The human papillomavirus E6 protein also fails to degrade p73 alpha, suggesting that the mechanisms governing p73 alpha stability are distinct from those known to regulate p53 stability. However, the interaction of Mdm2 with 73 alpha is sufficient to impede p73 alpha transcriptional function, despite the lack of degradation.

Reversal of p53-induced cell-cycle arrest

Activation of the tumor suppressor protein p53 can lead to arrest in both G1 and G2 stages of the cell cycle and, in some cells, to apoptotic cell death. In this study, we showed that the p53 response to a chemotherapeutic drug, actinomycin D, was reversible in both normal and tumor cells, even when a substantial proportion of tumor cells were undergoing apoptosis. Despite the clear reversibility of the p53-induced cell-cycle arrest after removal of actinomycin D, a substantial proportion of the cells arrested in G2 failed to resume normal cell-cycle progression and underwent another round of DNA synthesis. This endoreduplication probably reflects a function of the cyclin-dependent kinase inhibitor p21Waf1Cip1, which is expressed in response to p53. Our observation that this abnormal re-replication of DNA occurred in both transformed and untransformed cells after reversal of a p53 response may have implications for the eventual outcome of tumor therapies in which p53 is transiently expressed in a substantial number of normal as well as tumor cells.

Reversal of p53-induced cell-cycle arrest

Activation of the tumor suppressor protein p53 can lead to arrest in both G1 and G2 stages of the cell cycle and, in some cells, to apoptotic cell death. In this study, we showed that the p53 response to a chemotherapeutic drug, actinomycin D, was reversible in both normal and tumor cells, even when a substantial proportion of tumor cells were undergoing apoptosis. Despite the clear reversibility of the p53-induced cell-cycle arrest after removal of actinomycin D, a substantial proportion of the cells arrested in G2 failed to resume normal cell-cycle progression and underwent another round of DNA synthesis. This endoreduplication probably reflects a function of the cyclin-dependent kinase inhibitor p21Waf1Cip1, which is expressed in response to p53. Our observation that this abnormal re-replication of DNA occurred in both transformed and untransformed cells after reversal of a p53 response may have implications for the eventual outcome of tumor therapies in which p53 is transiently expressed in a substantial number of normal as well as tumor cells.

Efflux of rhodamine from CD56+ cells as a surrogate marker for reversal of P-glycoprotein-mediated drug efflux by PSC 833

The expression of high levels of P-glycoprotein (Pgp) in circulating mononuclear cells allowed us to use an ex vivo assay as a surrogate measure of Pgp antagonism. Efflux of rhodamine from CD56(+) cells was measured before the start of PSC 833 and at varying times thereafter. Patients receiving PSC 833 had decreased rhodamine efflux from their circulating CD56(+) cells. Time course studies showed that following a single oral dose of PSC 833, decreased rhodamine efflux was found in some patients within 15 minutes of treatment. Maximal inhibition was observed at times ranging from 45 minutes to 60 minutes. A dose-response relationship was shown between the concentration of PSC 833 in the blood and the inhibition of rhodamine efflux, with an apparent plateau of the inhibition of rhodamine efflux at approximately 1,000 ng/mL. The Ki, defined as the concentration required for half-maximal inhibition of Pgp-mediated rhodamine efflux, was determined to be in the range of 29 to 181 ng/mL; although results in two patients were distinctly different, with Ki values of 914 and 916 ng/mL. MRK-16 staining was similar among all patients. We conclude that measurement of rhodamine efflux from CD56(+) cells provides a surrogate assay with the potential for monitoring Pgp antagonism in clinical trials.

Mechanisms of p53-mediated apoptosis

The loss of p53-mediated apoptosis (programmed cell death) has been implicated as an important event in tumour progression in a number of systems. p53 can induce or potentiate apoptosis through several mechanisms, both by regulating the expression of genes which can participate in the apoptotic response and through transcriptionally independent means. There appears to be cell type variability in both the response to p53 expression and in the requirement for p53 transcriptional transactivation for the induction of apoptosis. It seems clear, however, that the induction of p53 in untransformed cells is more likely to result in cell-cycle arrest, whereas the expression of p53 in their transformed counterparts is more likely to result in the induction of apoptosis, and this may, in part, reflect the deregulated expression of E2F-1 in tumour cells. The synergistic action of p53 and E2F-1 in the induction of apoptosis has raised the possibility that the reactivation of p53 in transformed cells can be an effective tumour therapy.

Regulating plant/insect interactions using CO2 enrichment in model ecosystems

The greenhouse environment is a challenging artificial ecosystem in which it is possible to study selected plant/insect interaction in a controlled environment. Due to a combination of "direct" and "indirect" effects of CO2 enrichment on plant photosynthesis and plant development, canopy productivity is generally increased. In this paper, we discuss the effects of daytime and nighttime CO2 enrichment protocols on gas exchange of pepper plants (Capsicum annuum L, cv Cubico) grown in controlled environments. In addition, we present the effects of thrips, a common Insect pest, on the photosynthetic and respiratory activity of these plant canopies. Carbon dioxide has diverse effects on the physiology and mortality of insects. However, our data indicate that thrips and whiteflies, at least, are not killed "directly" by CO2 levels used to enhance photosynthesis and plant growth. Together the data suggest that the insect population is affected "indirectly" by CO2 and that the primary effect of CO2 is via its effects on plant metabolism.

IncP plasmids are unusually effective in mediating conjugation of Escherichia coli and Saccharomyces cerevisiae: involvement of the tra2 mating system

Mobilizable shuttle plasmids containing the origin-of-transfer (oriT) region of plasmids F (IncFI), ColIb-P9 (IncI1), and RP4/RP1 (IncPalpha) were constructed to test the ability of the cognate conjugation system to mediate gene transfer from Escherichia coli to Saccharomyces cerevisiae. Only the Palpha system caused detectable mobilization to yeast, giving peak values of 5 x 10(-5) transconjugants per recipient cell in 30 min. Transfer of the shuttle plasmid required carriage of oriT in cis and the provision in trans of the Palpha Tra1 core and Tra2 core regions. Genes outside the Tra1 core did not increase the mobilization efficiency. All 10 Tra2 core genes (trbB, -C, -D, -E, -F, -G, -H, -I, -J, and -L) required for plasmid transfer to E. coli K-12 were needed for transfer to yeast. To assess whether the mating-pair formation (Mpf) system or DNA-processing apparatus of the Palpha conjugation system is critical in transkingdom transfer, an assay using an IncQ-based shuttle plasmid specifying its own DNA-processing system was devised. RP1 but not ColIb mobilized the construct to yeast, indicating that the Mpf complex determined by the Tra2 core genes plus traF is primarily responsible for the remarkable fertility of the Palpha system in mediating gene transfer from bacteria to eukaryotes.

Using the national cancer institute anticancer drug screen to assess the effect of MRP expression on drug sensitivity profiles

The MRP gene contributes to one form of multidrug resistance. To identify drugs interacting with MRP, we measured MRP mRNA expression by quantitative PCR in 60 cell lines of the National Cancer Institute Anticancer Drug Screen. Expression was detected in all cell lines (highest in lung carcinomas and central nervous system tumors) with a range of 14-fold. A mean graph of MRP mRNA levels was constructed to determine Pearson correlation coefficients (PCCs) with mean graphs of >40,000 compounds using the COMPARE analysis. Only 20 compounds had PCCs of >/=0.500. The PCCs for VP-16, doxorubicin, and vincristine were 0.008, 0.13, and 0.257, respectively. Initially, 36 compounds with PCCs of >/=0.428 were analyzed using two MRP-overexpressing cell lines; low levels of cross-resistance was demonstrated for 23 compounds (1.3-9.4-fold). Twenty-four compounds also were available for further studies. Using a fluorescence activated cell sorter assay to measure competition of calcein efflux from MRP-overexpressing cells, 10 compounds were found to increase calcein retention by >/=2-fold. Ten compounds also were able to reduce ATP-dependent [3H]LTC4 transport into vesicles from MRP-overexpressing cells. These results contrast with previous studies with MDR-1 in which high correlations were found and confirmed for a large number of compounds. Although other assays may be more revealing, in these unselected cell lines, MRP mRNA expression was a poor predictor of drug sensitivity. This raises the possibility that other factors, including conjugating enzymes, glutathione levels, or other transporters, confound the MRP effect.

Hypoglycaemic activity of an HMG-containing flavonoid glucoside, chamaemeloside, from Chamaemelum nobile

The 3-hydroxy-3-methylglutaric acid (HMG) containing flavonoid glucoside chamaemeloside, has been determined to have in vivo hypoglycaemic activity comparable to that of free HMG. An improved isolation scheme for obtaining chamaemeloside from Chamaemelum nobile is presented.

Cell cycle arrest and DNA endoreduplication following p21Waf1/Cip1 expression

p21Waf1/Cip1 is a major transcriptional target of p53 and has been shown to be one of the principal mediators of the p53 induced G1 cell cycle arrest. We show that in addition to the G1 block, p21Waf1/Cip1 can also contribute to a delay in G2 and expression of p21Waf1/Cip1 gives rise to cell cycle profiles essentially indistinguishable from those obtained following p53 expression. Arrest of cells in G2 likely reflects an inability to induce cyclin B1/cdc2 kinase activity in the presence of p21Waf1/Cip1, although the inefficient association of p21Waf1/Cip1 and cyclin B1 suggests that the mechanism of inhibition is indirect. Cells released from an S-phase block were not retarded in their ability to progress through S-phase by the presence of p21Waf1/Cip1, despite efficient inhibition of cyclin E, A and B1 dependent kinase activity, suggesting that p21Waf1/Cip1 is inefficient at inhibiting replicative DNA synthesis in vivo. Interestingly, significant numbers of cells released from the p21Waf1/Cip1 activated G2 block undergo endoreduplication, passing through another S-phase before undergoing mitosis. This supports a function of the mitotic kinases in both entry into mitosis, and also in preventing re-replication of DNA following S-phase and suggests a role for p21Waf1/Cip1 in coupling DNA synthesis and mitosis. Unlike p53, which induces apoptosis in these cells, extended expression of p21Waf1/Cip1 resulted in the expression of a senescent-like phenotype in these p53 null, pRB null tumor cells.

Does short-term antiepileptic drug treatment in children result in cognitive or behavioral changes?

PURPOSE

To determine possible cognitive and behavioral effects of antiepileptic drug (AED) therapy by assessing children with newly diagnosed epilepsy before and after initiation of treatment. A comparison group of children with diabetes mellitus (DM) was included to control for the effects of practice, maturation, and chronic illness.

METHODS

Baseline neuropsychological assessments were completed for children with epilepsy (n = 37) and children with DM (n = 26) recruited through outpatient clinics at a regional children's hospital. Children were reevaluated 6 months from baseline testing. At follow-up, children with epilepsy had therapeutic AED levels and controlled seizures. Statistical analysis included a between-group repeated measures ANCOVA with pretest scores serving as the covariate.

RESULTS

Significant differences between groups were not found for any cognitive or behavioral factors, including attention (p < 0.24), immediate memory (p < 0.24), delayed memory (p < 0.10), complex motor speed (p < 0.19), or behavior problems (p < 0.89).

CONCLUSIONS

Changes in performance on cognitive and behavioral measures were not different for children treated with AEDs and controls. Although adverse effects may be associated with prolonged treatment, results would not suggest adverse effects from AED monotherapy during the first 6 months of therapy.

The alternative product from the human CDKN2A locus, p14(ARF), participates in a regulatory feedback loop with p53 and MDM2

The two distinct proteins encoded by the CDKN2A locus are specified by translating the common second exon in alternative reading frames. The product of the alpha transcript, p16(INK4a), is a recognized tumour suppressor that induces a G1 cell cycle arrest by inhibiting the phosphorylation of the retinoblastoma protein by the cyclin-dependent kinases, CDK4 and CDK6. In contrast, the product of the human CDKN2A beta transcript, p14(ARF), activates a p53 response manifest in elevated levels of MDM2 and p21(CIP1) and cell cycle arrest in both G1 and G2/M. As a consequence, p14(ARF)-induced cell cycle arrest is p53 dependent and can be abrogated by the co-expression of human papilloma virus E6 protein. p14(ARF) acts by binding directly to MDM2, resulting in the stabilization of both p53 and MDM2. Conversely, p53 negatively regulates p14(ARF) expression and there is an inverse correlation between p14(ARF) expression and p53 function in human tumour cell lines. However, p14(ARF) expression is not involved in the response to DNA damage. These results place p14(ARF) in an independent pathway upstream of p53 and imply that CDKN2A encodes two proteins that are involved in tumour suppression.

The transcription-repair coupling factor CSA is required for efficient repair only during the elongation stages of RNA polymerase II transcription

The known nucleotide excision repair (NER) defects of xeroderma pigmentosum (XP) and Cockayne syndrome (CS) cells can be exploited to analyze mechanisms of repair of UV-induced cyclobutane pyrimidine dimers (CPDs) at nucleotide (nt.) resolution. The two gene products of the CS complementation groups (CSA and CSB) have been implicated in the preferential repair of the transcribed strand of human genes. We had previously described very efficient repair of CPDs at sequences near the transcription initiation site of the human JUN gene in normal fibroblasts. Here, we have analyzed repair in a CSA fibroblast strain. CSA cells exhibited rapid repair near the transcription initiation site (positions -45 to +15) but were deficient in repair of sequences on the transcribed strand beginning around nt. +20. There was also no strand-selective repair of sequences further downstream of the start site (+260 to +450). The results suggest that the transcription-repair coupling factor (TRCF) CSA is required for efficient repair only during the elongation stages of RNA polymerase II transcription. We also discuss possible mechanisms of differential repair observed near the transcription initiation site in XP and CS cells and conclude that these in vivo repair data support some recent models obtained from nucleotide excision repair experiments in vitro.

The efficacy of local anaesthesia for percutaneous epididymal sperm aspiration and testicular sperm aspiration

A total of 37 percutaneous epididymal sperm aspiration (PESA) and/or testicular sperm aspiration (TESA) procedures were performed under local anaesthesia (LA) on 34 men between June and November 1996. Local anaesthesia was achieved by injecting 10 ml of 1% lignocaine solution along the sides of the vas deferens near the external inguinal ring (spermatic cord block). Sperm retrieval was successful in 92% of the procedures. Of the 37 procedures, in 29 the patients felt either no pain or mild discomfort while in six they experienced moderate but tolerable pain. Analgesia was incomplete in two procedures and was supplemented with i.v. sedation. Vasovagal reflex in two procedures was reversed by i.v. atropine. In 24 procedures patients felt relaxed, whilst in 13 they felt anxious. In 32 procedures the patients expressed overall satisfaction. If the procedure was to be repeated, after 29 procedures the patients requested LA again, while after four procedures they preferred i.v. sedation and after four were undecided. LA is adequate for PESA and TESA in a large proportion of patients. Prior discussion of LA technique with the patient is necessary. Back-up facilities for i.v. sedation and atropine should be available.

Risk of fatal pulmonary embolism in patients with treated venous thromboembolism

CONTEXT

The most serious complication of deep vein thrombosis (DVT) or nonfatal pulmonary embolism (PE) is fatal PE. However, reliable estimates as to the risk of fatal PE in patients with treated DVT or PE are lacking.

OBJECTIVE

To provide reliable estimates of the risk of fatal PE and the case-fatality rate of recurrent DVT or PE among patients presenting with symptomatic DVT or PE, during and following 3 months of anticoagulant therapy.

DATA SOURCES

A MEDLINE literature search was performed to identify prospective studies in which patients with symptomatic DVT or PE were treated with 5 to 10 days of heparin and 3 months of oral anticoagulants. We searched the years 1966 to September 1997 using the search terms thrombophlebitis, diagnosis, drug therapy, and prognosis. Current Contents and bibliographies were also scanned.

DATA EXTRACTION

Of 137 retrieved studies, 25 studies satisfied predetermined methodologic criteria and were included in the analysis.

DATA SYNTHESIS

Among patients presenting with DVT, the rate of fatal PE during anticoagulant therapy was 0.4% (95% confidence interval [CI], 0.2%-0.6%); following anticoagulant therapy it was 0.3 per 100 patient-years (95% CI, 0.1-0.8). The case-fatality rate of recurrent DVT or PE during anticoagulant therapy was 8.8% (95% CI, 5.0%-14.1%); following anticoagulant therapy it was 5.1% (95% CI, 1.4%-12.5%). Among patients presenting with PE, the rate of fatal PE during anticoagulant therapy was 1.5% (95% CI, 0.9%-2.2%); following anticoagulant therapy it was 0 per 265 patient-years (95% CI, 0-3.6). The case-fatality rate of recurrent DVT or PE among patients presenting with PE was 26.4% (95% CI, 16.7%-38.1%).

CONCLUSION

Among patients with symptomatic PE or DVT who are treated with anticoagulants for 3 months, fatal PE is rare during and following anticoagulant therapy. Patients presenting with PE are more likely to die of recurrent PE or DVT than are patients presenting with DVT.

Effects of PALA on the pharmacokinetics of 5-fluorouracil

N-(phosphonacetyl)-L-aspartate (PALA) modulates the activity of 5-fluorouracil (5-FU) by inhibiting pyrimidine biosynthesis. A cross-over study was conducted to determine whether PALA affects the pharmacokinetic parameters of 5-FU in patients given 5-FU/folinic acid (FA). Six patients (3 males, 3 females) aged 63 4.3 (mean SD) years (body surface area of 1.84 18 m2) with metastatic colorectal carcinoma were given two courses of treatment. The treatment consisted of 250 mg/m2 of PALA on day 1 followed by 20 mg/m2 FA and 400 mg/m2 5-FU (5 min i.v. bolus injection) on days 2-5 in one cycle of treatment (PALA+). In another treatment cycle, these doses of 5-FU and FA were given for all 5 days without PALA (PALA-). The two courses were given four weeks apart. It was determined by random selection whether the course with PALA was given before or after the course without PALA. Blood samples were collected over a period of three hours, starting from the beginning of 5-FU infusion on days 2 and 5 of both courses. Plasma concentrations of 5-FU were determined by an HPLC technique. Pharmacokinetic parameters were calculated using a non-compartmental model. While there were no significant differences between pharmacokinetic parameters in the PALA+ vs PALA- courses, there was a trend towards a decreasing area under the curve (AUC) and increasing clearance (Cl) in PALA+ courses of treatment.

Morphology of acute promyelocytic leukemia with cytogenetic or molecular evidence for the diagnosis: characterization of additional microgranular variants

Early diagnosis of t(15;17) acute promyelocytic leukemia (APL) is essential because of the associated disseminated intravascular coagulation and the unique response of the disease to all-trans retinoic acid (ATRA) therapy. Early diagnosis depends primarily on morphological recognition. The French-American-British (FAB) classification, however, does not describe all morphological variations that occur in APL. In 25 cases with evidence of APL confirmed by cytogenetic and/or molecular analysis, we found a heterogeneous morphological group. The most common form of APL was heterogeneous and consisted of various combinations of cells in which hypergranular cells and some cells with multiple Auer rods were obvious. In some cases, one cell predominated. This led to the description of five subcategories. These included the classical FAB M3 with hypergranular cells and multiple Auer rods; the FAB variant with hypogranular bilobed cells; the basophilic cell type of McKenna et al. [Br. J. Haematol 50:201, 1982]; and two additional subtypes, one consisting of differentiated promyelocytes and a few blast cells (M2-like), and the other consisting largely of blast cells and a few early promyelocytes (M1-like). Immunophenotyping revealed a pattern of CD33 and/or CD13 positivity, and CD14 and HLA-DR negativity in 96% of cases. CD2 was positive in the FAB variant and in the subtype with basophilic cells, but negative with other subtypes. Three out of five cases with basophilic cell predominance [McKenna et al.: Br J Haematol 50:201, 1982], and one out of two M2-like cases, responded to ATRA therapy. Awareness of the heterogeneity and the atypical morphologic subtypes found in t(15;17) APL will contribute to improved recognition and early institution of ATRA therapy.

Sequence-specific and domain-specific DNA repair in xeroderma pigmentosum and Cockayne syndrome cells

Xeroderma pigmentosum (XP) and Cockayne syndrome (CS) cells have specific DNA repair defects. We had previously analyzed repair rates of cyclobutane pyrimidine dimers at nucleotide resolution along the human JUN gene in normal fibroblasts and found very efficient repair of sequences near the transcription initiation site but slow repair along the promoter. To investigate sequence-specific repair rate patterns in XP and CS cells, we conducted a similar analysis in XPA, XPB, XPC, XPD, and CSB fibroblasts. XPA cells were almost completely repair-deficient at all sequences analyzed. XPC cells repaired only the transcribed DNA strand beginning at position -20 relative to the transcription start site. Both XBP and XPD cells were deficient in repair of nontranscribed DNA and also very inefficiently repaired the transcribed strand including sequences near the transcription start site. CSB cells exhibited rapid repair near the transcription initiation site but were deficient in repair of sequences encountered by RNA polymerase during elongation (beginning at position +20). Since transcription of the JUN gene was UV-induced in all fibroblast strains, including CSB, the defective repair of the transcribed strand in CSB cannot be explained by a lack of transcription; rather, it appears to be a true DNA repair defect.

Accumulation of p16INK4a in mouse fibroblasts as a function of replicative senescence and not of retinoblastoma gene status

Viral transformation of mouse and human fibroblasts has very different effects on the composition of cyclin-dependent kinase (Cdk) complexes. In human cells transformed by the large T-antigen of simian virus 40 (SV40 T-Ag) and human tumour cell lines that lack a functional retinoblastoma gene product (pRb) no cyclin D1-Cdk4 complexes can be detected because all the available Cdk4 is associated with the Cdk-inhibitor p16INK4a. In contrast, SV40-transformed mouse cells and fibroblasts from Rh1-nullizygous mouse embryos contain normal levels of cyclin D1-Cdk4 complexes. To investigate this species difference, we have compared the biochemical properties and expression of mouse p16INK4a with that of its human counterpart. There is a marked increase in p16 RNA and protein levels as primary embryo fibroblasts approach their finite lifespan in culture, but mouse p16 expression does not appear to be influenced by the status of pRb. Transformed or spontaneously immortalized mouse cells therefore do not achieve the very high levels of p16 characteristic of pRb-negative human cell lines. We suggest that these differences may be related to the different frequencies with which mouse and human cells can be immortalized in culture.

Induction of DNA synthesis and apoptosis are separable functions of E2F-1

The family of E2F transcription factors have an essential role in mediating cell cycle progression, and recently, one of the E2F protein family, E2F-1, has been shown to participate in the induction of apoptosis. Cooperation between E2F and the p53 tumor suppressor protein in this apoptotic response had led to the suggestion that cell cycle progression induced by E2F-1 expression provides an apoptotic signal when placed in conflict with an arrest to cell cycle progression, such as provided by p53. We show here that although apoptosis is clearly enhanced by p53, E2F-1 can induce significant apoptosis in the absence of p53. Furthermore, this apoptotic function of E2F-1 is separable from the ability to accelerate entry into DNA synthesis. Analysis of E2F-1 mutants indicates that although DNA-binding is required, transcriptional transactivation is not necessary for the induction of apoptosis by E2F-1, suggesting that it may be mediated through alleviation of E2F-dependent transcriptional repression. These results indicate that E2F-1 can show independent cell cycle progression and apoptotic functions, consistent with its putative role as a tumor suppressor.

Perturbation of the p53 response by human papillomavirus type 16 E7

The p53 tumor suppressor protein can induce both cell cycle arrest and apoptosis in DNA-damaged cells. In human carcinoma cell lines expressing wild-type p53, expression of E7 allowed the continuation of full cell cycle progression following DNA damage, indicating that E7 can overcome both G1 and G2 blocks imposed by p53. E7 does not interfere with the initial steps of the p53 response, however, and E7 expressing cells showed enhanced expression of p21(waf1/cip1) and reductions in cyclin E- and A-associated kinase activities following DNA damage. One function of cyclin-dependent kinases is to phosphorylate pRB and activate E2F, thus allowing entry into DNA synthesis. Although E7 may substitute for this activity during cell division by directly targeting pRB, continued cell cycle progression in E7-expressing cells was associated with phosphorylation of pRB, suggesting that E7 permits the retention of some cyclin-dependent kinase activity. One source of this activity may be the E7-associated kinase, which was not inhibited following DNA damage. Despite allowing cell cycle progression, E7 was unable to protect cells from p53-induced apoptosis, and the elevated apoptotic response seen in these cells correlated with the reduction of cyclin A-associated kinase activity. It is possible that inefficient cyclin A-dependent inactivation of E2F at the end of DNA synthesis contributes to the enhanced apoptosis displayed by E7-expressing cells.

Regulation and function of the cyclin-dependent kinase inhibitor p16CDKN2

Many human tumours show perturbations of a pathway that includes the D-cyclins, their associated cyclin-dependent kinases, and specific kinase inhibitors. The focal point of this pathway is the product of the retinoblastoma tumour suppressor gene, pRb, which imposes a block on G1 phase progression. Thus, the major role of the cyclin D-dependent kinases is to overcome this block by initiating the phosphorylation of pRb. Excessive activity of this pathway is likely to lead to excessive cell proliferation. Conversely, accumulation of the inhibitors is associated with the cessation of cell division.

Hypercoagulability in patients with primary biliary cirrhosis and primary sclerosing cholangitis evaluated by thrombelastography

BACKGROUND/AIMS

Patients with primary biliary cirrhosis and primary sclerosing cholangitis survive variceal bleeding better than patients with alcoholic cirrhosis and have less bleeding at liver transplantation. Recently, patients with primary biliary cirrhosis have been found to have a higher incidence of thrombosis in the portal venous tree. We hypothesized that primary biliary cirrhosis and primary sclerosing cholangitis patients may be hypercoagulable.

METHODS

We used thrombelastography, which is a simple technique for evaluating whole blood clotting and fibrinolysis, to establish if hypercoagulability was present, defined by thrombelastography values greater than 2SD over controls: r<19 mm (this reflects plasma clotting factors), maximum amplitude (ma) >60 mm, and alpha angle >43 degrees (these reflect platelets and fibrinogen levels). We evaluated 47 primary biliary cirrhosis and 21 primary sclerosing cholangitis patients, 40 with non-cholestatic cirrhosis and 40 healthy subjects as control groups with thrombelastography, full blood count, prothrombin time, partial thromboplastin time and, fibrinogen concentrations. In those with hypercoagulability we evaluated protein S, C, anti-thrombin III levels and activated protein C phenotype.

RESULTS

All three thrombelastography abnormalities present together defined hypercoagulability: these were found in 13 of 47 (28%) primary biliary cirrhosis and in nine of 21 (43%) primary sclerosing cholangitis patients independent of cirrhosis, and bilirubin concentration, but in only 2 of 40 (5%) patients with noncholestatic cirrhosis and in none of the healthy controls (p<0.03 and p<0.0002, respectively). There was no correlation between the fibrinogen concentration (which was normal in all patients) or platelet count and the thrombelastography parameters. Only six of the 22 hypercoagulable patients had lower than normal values of protein S, C or antithrombin III. Activated protein C phenotype was normal in all.

CONCLUSIONS

This diffference between biliary and parenchymal liver disease may have clinical implications, which need to be defined.

Initial pharmacokinetics and bioavailability of PSC 833, a P-glycoprotein antagonist

Resistant cancer cells have been shown to overexpress a 170-kd membrane glycoprotein called P-glycoprotein. P-glycoprotein, a product of the multidrug resistance 1 gene, functions as an energy-dependent efflux pump that decreases intracellular drug concentrations. A variety of nonchemotherapeutic agents have been shown to inhibit P-glycoprotein-dependent drug efflux including cyclosporin. PSC 833 is a nonimmunosuppressive derivative of cyclosporin D with the ability to reverse multidrug resistance because of P-glycoprotein overexpression in vitro. As part of early clinical development of PSC 833, the authors investigated the bioavailability of an oral formulation of PSC 833. PSC 833 (3 mg/kg) was administered as a 2-hour intravenous infusion on day 1 of the treatment cycle. Serial blood samples for the determination of PSC 833 whole blood concentrations were obtained after both the intravenous and oral doses. On day 5 of the study, patients received a single oral dose (9 mg/kg) of PSC 833. A total of 14 patients were treated. The intravenous data were best described by a two-compartment open model. The oral data also were described using a two-compartment model, with oral absorption incorporating a lag time to account for possible delays in absorption. There was large intra- and interpatient variability in the pharmacokinetics of PSC 833 in these patients. The absolute bioavailability of PSC 833 was 34% but ranged from 3% to 58% of the administered dose. The clearance (CI) of PSC 833, in general, was consistent between the two dose forms administered. The pharmacokinetic behavior of PSC 833 appears to be similar to that of cyclosporine.

Resistance to paclitaxel mediated by P-glycoprotein can be modulated by changes in the schedule of administration

PURPOSE

Increasing use of paclitaxel in clinical oncology has stimulated interest in its mechanisms of resistance and ways to overcome these. Studies were performed with paclitaxel to determine the role of P-glycoprotein in drug sensitivity, and the effect of schedule on relative resistance. We have previously reported that prolonged exposure to P-glycoprotein substrates decreases relative resistance in multidrug resistant cells.

METHODS

Using both unselected and drug-selected cell lines, cross-resistance and cytotoxicity reversal studies using cyclosporin A were performed. In multidrug-resistant cells, cross-resistance was evaluated after 3-, 24-, and 96-h exposures to paclitaxel.

RESULTS

Cross-resistance to paclitaxel in P-glycoprotein-expressing sublines was shown to be comparable to that of other drugs transported by P-glycoprotein. Sensitivity to paclitaxel could be modulated by cyclosporin A in unselected cell lines expressing P-glycoprotein and not in P-glycoprotein-negative cell lines. Resistance to paclitaxel was reduced tenfold by increasing the duration of exposure in P-glycoprotein-expressing cells. This effect was not observed in a paclitaxel-resistant cell line which does not express P-glycoprotein.

CONCLUSIONS

These studies extend observations on the schedule dependence of paclitaxel cytotoxicity and the role of P-glycoprotein in mediating paclitaxel sensitivity. The schedule dependence of relative resistance suggests that infusional paclitaxel may help in overcoming P-glycoprotein-mediated resistance.

A high-resolution analysis of chromatin structure along p53 sequences

A detailed investigation of how nucleosomes are formed and arranged on the DNA sequence is a prerequisite to understanding the molecular mechanisms of DNA-dependent processes such as transcription, replication, DNA repair, and mutagenesis. In this report we analyzed the chromatin structure of exons 5-8 of the p53 gene in human fibroblasts. We mapped at the nucleotide level the positions of DNase I and micrococcal nuclease cleavage sites in permeabilized cells. Areas of clear DNase I protection, which would be indicative of the binding of sequence-specific proteins, were not detected. Instead, the micrococcal nuclease and DNase digestion patterns suggested that this region was covered by nucleosomes and that two areas spanning exons 5 and 6 are occupied preferentially. These nucleosomes could influence DNA damage distribution, repair of certain lesions, and other aspects of the mutagenesis process in p53 sequences.

Characterisation of human cyclin G1 and G2: DNA damage inducible genes

Several genes have been identified as targets for transcriptional activation by the p53 tumour suppressor protein. Rodent cyclin G was previously identified as a p53 responsive gene and in order to assess the role played by cyclin G as a mediator of p53 function in humans cells we have isolated full length human cyclin G1 and identified a related gene designated cyclin G2. Both human G-cyclins are induced by the DNA damaging agent actinomycin-D and although the induction of cyclin G1 is clearly p53 dependent, activation of cyclin G2 expression was observed in the absence of p53. Based on sequence similarity, the G-cyclins and the recently identified cyclin I form a distinct sub-group within the larger cyclin family, possibly reflecting some degree of functional similarity.

Differential activation of target cellular promoters by p53 mutants with impaired apoptotic function

The p53 tumor suppressor protein is a sequence-specific transcriptional activator, a function which contributes to cell cycle arrest and apoptosis induced by p53 in appropriate cell types. Analysis of a series of p53 point mutants has revealed the potential for selective loss of the ability to transactivate some, but not all, cellular p53-responsive promoters. p53 175P and p53 181L are tumor-derived p53 point mutants which were previously characterized as transcriptionally active. Both mutants retained the ability to activate expression of the cyclin-dependent kinase inhibitor p2lcip1/waf1, and this activity correlated with the ability to induce a G1 cell cycle arrest. However, an extension of this survey to include other p53 targets showed that p53 175P was defective in the activation of p53-responsive sequences derived from the bax promoter and the insulin-like growth factor-binding protein 3 gene (IGF-BP3) promoter, while p53 181L showed loss of the ability to activate a promoter containing IGF-BP3 box B sequences. Failure to activate transcription was also reflected in the reduced ability of the mutants to bind the p53-responsive DNA sequences present in these promoters. These specific defects in transcriptional activation correlated with the impaired apoptotic function displayed by these mutants, and the results suggest that activation of cell cycle arrest genes by p53 can be separated from activation of genes with a role in mediating the p53 apoptotic response. The cellular response to p53 activation may therefore depend, at least in part, on which group of p53-responsive genes become transcriptionally activated.

Behavioral descriptors that differentiate between seizure and nonseizure events in a pediatric population

The diagnosis and treatment of epilepsy relies heavily on descriptions of behavioral changes noted during seizure episodes. A pilot study was completed to determine the frequency of occurrence of behaviors commonly associated with seizures in a pediatric population (n = 153). Caretakers of the children (ages = 4 months to 19 years) were asked to respond to a checklist containing 40 behavioral descriptors. Thirteen descriptors were found to differentiate between seizure and nonseizure events. Twelve of these behaviors were endorsed significantly more frequently by caretakers of children with seizures including the following: does not remember what happened, moves mouth funny, drools, jerking/twitching, becomes stiff, changes in breathing, stares off, bites or chews tongue, eyes look glassy, will not respond, mumbles or slurs words, and eyes or head turn to one side. One behavior, fidgets in seat, was significantly more associated with nonseizure episodes. The behavioral descriptors may be presented in a checklist format or incorporated within a clinical interview in primary care settings for initial screening of children with possible seizure disorders.

Specific loss of apoptotic but not cell-cycle arrest function in a human tumor derived p53 mutant

The p53 tumor-suppressor gene product is frequently inactivated in malignancies by point mutation. Although most tumor-derived p53 mutants show loss of sequence specific transcriptional activation, some mutants have been identified which retain this activity. One such mutant, p53175P, is defective for the suppression of transformation in rodent cells, despite retaining the ability to suppress the growth of p53-null human cells. We now demonstrate that p53175P can induce a cell-cycle arrest in appropriate cell types but shows loss of apoptotic function. Our results therefore support a direct role of p53 transcriptional activation in mediating a cell-cycle arrest and demonstrate that such activity is not sufficient for the full apoptotic response. These data suggest that either p53 can induce apoptosis through a transcriptionally independent mechanism, a function lost by p53175P, or that this mutant has specifically lost the ability to activate genes which contribute to cell death, despite activation of genes responsible for the G1 arrest. This dissociation of the cell-cycle arrest and apoptotic activities of p53 indicates that inactivation of p53 apoptotic function without concomitant loss of growth inhibition can suffice to relieve p53-dependent tumor-suppression in vivo and thereby contribute to tumor development.

p53 in signaling checkpoint arrest or apoptosis

The cell cycle arrest and apoptotic functions of p53 both contribute to the role of this tumour suppressor protein in preventing replication of cells suffering DNA damage. Although the ability of p53 to function as a sequence-specific transcription factor appears to be directly and causally linked to the implementation of an arrest at the G1 stage of the cell cycle, the contribution of transcriptional activation to the apoptotic response is less clear. It seems likely that several p53 activities, both transcriptionally dependent and transcriptionally independent, can play a role in mediating cell death. The requirement for each of these functions appears to depend on the cell type, the cell environment and other genetic alterations already sustained by the cell in which p53 function is activated.

Evidence for different modes of action of cyclin-dependent kinase inhibitors: p15 and p16 bind to kinases, p21 and p27 bind to cyclins

A number of low molecular weight proteins have recently been identified that specifically inhibit the function of cyclin-dependent protein kinases in mammalian cells. These fall into two distinct families based on primary sequence comparisons and probable modes of action. Using a simple in vitro binding assay, we show that p21CDKN1 and the related p27KIP1 can efficiently interact with cyclins D1, D2, D3, E and A, and to a lesser extent with cyclin B. By generating a deleted form of cyclin D1 that binds to p21 and p27 but not to Cdks, we confirm that these interaction do not depend on stoichiometric amounts of the relevant kinase subunit. Moreover, p21 and p27 do not detectably associated with kinase subunits unless a cyclin is present. This is in sharp contrast to the properties of p16CDKN2 and p15MTS2/INK4b which bind to Cdk4 and Cdk6 in the absence of any cyclin. These data suggest that p21 and p27 act as broad spectrum regulators of cyclin dependent kinase function by participating in ternary complexes whereas the p16 family specifically interfere with the formation of cyclin D-dependent kinase complexes.

Artifacts in functional magnetic resonance imaging from gaseous oxygen

Unexpectedly large fluctuations in signal intensity were identified in the functional MRI (FMRI) of normal subjects breathing pure oxygen intermittently. To test the hypothesis that the signal changes were due to fluctuating concentrations of gaseous (paramagnetic) oxygen in the magnetic field, echo planar gradient echo images were acquired of a phantom contiguous to an oxygen mask through which pure oxygen was administered intermittently via plastic tubing. As a control, room air was administered intermittently or oxygen continuously in the same experimental protocol. Signal intensity changes of up to 60% temporally correlated with the administration of oxygen were produced in the phantom. In functional images prepared from the echo planar images, the signal intensity changes resulted in artifacts especially at interfaces in the phantom. The intermittent administration of pure oxygen during acquisition of data for FMRI may produce signal intensity changes that stimulate or obscure function.

Generation of a drug resistance profile by quantitation of mdr-1/P-glycoprotein in the cell lines of the National Cancer Institute Anticancer Drug Screen

Identifying new chemotherapeutic agents and characterizing mechanisms of resistance may improve cancer treatment. The Anticancer Drug Screen of the National Cancer Institute uses 60 cell lines to identify new agents. Expression of mdr-1/P-glycoprotein was measured by quantitative PCR. Expression was detected in 39 cell lines; the highest levels were in renal and colon carcinomas. Expression was also detected in all melanomas and central nervous system tumors, but in only one ovarian carcinoma and one leukemia cell line. Using a modified version of the COMPARE program, a high correlation was found between expression of mdr-1 and cellular resistance to a large number of compounds. Evidence that these compounds are P-glycoprotein substrates includes: (a) enhancement of cytotoxicity by verapamil; (b) demonstration of cross-resistance in a multidrug-resistant cell line, (c) ability to antagonize P-glycoprotein, increasing vinblastine accumulation by decreasing efflux; and (d) inhibition of photoaffinity labeling by azidopine. Identification of many heretofore unrecognized compounds as substrates indicates that P-glycoprotein has a broader substrate specificity than previously recognized. This study confirms the validity of this novel approach and provides the basis for similar studies examining a diverse group of gene products, including other resistance mechanisms, putative drug targets, and genes involved in the cell cycle and apoptosis.

Cyclin D1 as a cellular proto-oncogene

Deregulated expression of cyclin D1 occurs in several types of human cancer. Since it often results from a specific chromosomal abnormality, this over-expression is likely to be significant in the development of the disease. Cyclin D1 is also implicated in virally induced tumors in mice and transgenic models based on ectopic expression if cyclin D1 recapitulate features of the naturally occurring tumors. By these criteria, as well as its effects in transfected rodent cells, cyclin D1 has the hallmarks of a cellular proto-oncogene. Although the normal role of cyclin D1 is not well understood, its oncogenic properties appear to involve functional interactions with cyclin-dependent kinases, the retinoblastoma gene product and the MTS1/p16 tumor suppressor gene.

Lack of cyclin D-Cdk complexes in Rb-negative cells correlates with high levels of p16INK4/MTS1 tumour suppressor gene product

D-type cyclins, in association with the cyclin-dependent kinases Cdk4 or Cdk6, regulate events in the G1 phase of the cell cycle and may contribute to the phosphorylation of the retinoblastoma gene product (Rb). However, in cells in which the function of Rb has been compromised, either by naturally arising mutations or through binding to proteins encoded by DNA tumour viruses, Cdk4 and Cdk6 are not associated with D cyclins. Instead, both kinases form binary complexes with a stable 16 kDa protein (p16) encoded by the putative tumour suppressor gene INK4/MTS1 on human chromosome 9p21. Here we show an inverse correlation between Rb status and the expression of p16. Since Rb-negative cells express high levels of p16, we suggest that in these cells p16 competes with D cyclins for binding to Cdk4 and Cdk6 and prevents formation of active complexes. In line with these predictions, DNA tumour virus oncoproteins do not disrupt cyclin D1-Cdk4 complexes in cells lacking p16.

Phase II study of paclitaxel in relapsed non-Hodgkin's lymphomas

PURPOSE

To assess the efficacy and toxicity of paclitaxel administered as a 96-hour infusion to patients with relapsed non-Hodgkin's lymphomas (NHLs).

PATIENTS AND METHODS

Eligible patients had relapsed NHL and measurable disease and were considered incurable. Paclitaxel was infused at a dose of 140 mg/m2 every 3 weeks. Premedications to prevent paclitaxel hypersensitivity reactions were not administered and no patients received corticosteroids. Expression of the multidrug resistance (mdr-1) gene was determined in tumor from 17 patients by mRNA quantitative polymerase chain reaction (PCR).

RESULTS

Thirty-one patients received a total of 99 cycles of paclitaxel. Two patients were not assessable for response. The median age was 50 years, 71% had stage IV disease, and intermediate/high-grade histology was present in 65% of patients. Patients had received a median of three prior chemotherapy regimens, and 68% of patients had responded to the previous chemotherapy (chemotherapy-sensitive). Of 29 assessable patients, five (17%) achieved a partial response (PR). With a median potential follow-up time of 17 months, the median event-free and overall survival durations were 1.6 and 7.5 months, respectively. No correlation was found between response to paclitaxel and extent of prior treatment or response. The mdr-1 gene was easily detectable in 14 of 17 tumor biopsies, but was low in all but one sample. The most serious toxicity was grade 4 neutropenia, which occurred during 14% of cycles.

CONCLUSION

Paclitaxel was well tolerated, but had a low response rate in patients with relapsed NHLs. There was no clear association between response to paclitaxel and extent of our response to prior treatment. Most patients had chemotherapy-sensitive disease, which suggests that the low response rate to paclitaxel was probably not due to general chemotherapy resistance. Paclitaxel provided good palliation in a minority of patients and is a reasonable agent to consider for use in patients who have failed to respond to standard chemotherapy.

Socialization to the culture of a rehabilitation hospital: an ethnographic study

OBJECTIVES

Most previous research on rehabilitation of patients after spinal cord injuries has dealt with the attainment of outcomes valued by staff members or with the prediction of successful outcomes based on sociodemographic characteristics of patients. This study examined the rehabilitation process from the insider's perspective of an individual patient to determine his view of important adaptive problems and to examine how these problems were addressed.

METHODS

Ethnographic methods were used for fine-grained documentation of the experiences of one 30-year-old man with spinal cord injury. Daily interview were conducted with this patient during his 116 days of inpatient rehabilitation. An interdisciplinary research team analyzed the data with the constant comparative method to identify a number of recurring themes.

RESULTS

Findings indicate that in addition to learning how to function in the local world of the rehabilitation hospital, the patient also learned a new identify as a person with a long-term disability.

DISCUSSION

A central theme was the patient's ongoing attempt to figure out how his future was related to his life before the injury and how he could use previous competencies in adapting to disability. Staff members seemed so intent on teaching the patient new skills that they often discounted the significance of his past experience and failed to engage in helping the patient connect his future life story to his past.