Search PubMed⌕ Search

Biomedical subjects

M R Green

Publications and source records attributed to M R Green.

At least 127 records · Page 7Linked to original sources
PubMed1996

A phase I/II trial of etoposide and cisplatin in extensive small cell lung cancer: a cancer and leukemia group B study.

Patients with untreated extensive small cell lung cancer (SCLC) with CALGB performance scores 0-2 were treated with etoposide 200 mg/m2/day on days 1-3 and cisplatin doses of 20, 30, or 35 mg/m2/day days 1-3 in a Phase I/II format. Of the nine patients treated at the 35 mg/m2/day cisplatin dose in the Phase I portion of the study, Grade 4 leukopenia occurred in five patients and Grade 4 thrombocytopenia in four. There were two deaths due to myelosuppression and sepsis. This dose was thus considered the maximum tolerated dose (MTD), and a Phase II trial was then conducted using this treatment program. In the Phase II trial of 39 patients, the objective response rate was 67% (95% confidence interval, 50-81%) with 21% complete responses (CI 9-36%). Median survival was 10.5 months. Grade 4-5 leukopenia was seen in 57% and Grade 4-5 thrombocytopenia in 56%. The MTD defined by this Phase I trial represents a 67-100% increase in etoposide and a 32-42% increase in cisplatin dosage compared to prior studies. The observed objective response rates with this regimen are comparable to studies using conventional doses, but hematological toxicity was higher.

Adult↗
PubMed1996

A randomized phase II study of ifosfamide/mesna/cisplatin plus G-CSF or etoposide/cisplatin plus G-CSF in advanced non-small cell lung cancer: a Cancer and Leukemia Group B study.

This Phase II study was designed to determine the efficacy of two chemotherapy regimens with G-CSF support for patients with advanced non-small cell lung cancer (NSCLC). One-hundred and one patients with Stage IIIB or IV NSCLC and performance status 0-1 were randomized to receive ifosfamide 2.0 g/m2 days 1-3, mesna 400 mg/m2 at 0, 4, 6 h days 1-3, cisplatin 33 mg/m2 days 1-3 or etoposide 200 mg/m2 days 1-3, cisplatin 35 mg/m2 days 1-3. Both groups received G-CSF 5 micrograms/kg SQ day 4 to the post day 11 absolute neutrophil count > 10 000. For the 47 eligible patients receiving ifosfamide/mesna/cisplatin, the response rate was 26% (95% confidence interval: 14-40%) and the median survival 7.5 months (95% confidence interval: 5.8-11.0 months). Grade 3 or worse toxicities were: neutropenia 75%, thrombocytopenia 70%, infection 21%. There were two treatment-related deaths due to infection. For course 1, the median absolute neutrophil count nadir was 1.3, platelet nadir 96 000 and incidence of febrile neutropenia 16%. For the 48 eligible patients receiving etoposide/cisplatin, the response rate was 21% (95% confidence interval: 11-35%) and median survival 5.8 months (95% confidence interval: 4.5-9.7 months). Grade 3 or worse toxicities were: neutropenia 90%, thrombocytopenia 58%, infection 29%. There were three treatment-related deaths due to infection. For course 1, the median absolute neutrophil count was 0.2, platelet nadir 80 000 and incidence of febrile neutropenia 33%. For both ifosfamide/mesna/cisplatin and etoposide/cisplatin, median duration of Grade IV neutropenia was short (< or = 4 days), time to subsequent courses 21 days and dose delivered > 95% of planned dose. Although G-CSF allowed full doses of drugs to be delivered on schedule, both ifosfamide/mesna/cisplatin and etoposide/cisplatin produced response rates and survival similar to other cisplatin-based regimens. In view of the significant cost of G-CSF and no obvious improvement in response rate, survival or toxicity profile, G-CSF cannot be recommended with these chemotherapy regimens for patients with advanced NSCLC.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

A non-canonical base pair within the human immunodeficiency virus rev-responsive element is involved in both rev and small molecule recognition.

BACKGROUND: Human immunodeficiency virus (HIV) replication depends on the interaction of an HIV regulatory protein, Rev, with a viral RNA element (the Rev-responsive element, RRE). The high affinity RRE core region contains a non-canonical base pair (G48:G71) that is important for Rev recognition. Aminoglycoside antibiotics, specifically neomycin B, bind to the RRE and selectively block Rev-RRE interactions in vivo and in vitro. We attempted to generate an in vitro model for the establishment of HIV-1 resistance to neomycin B. RESULTS: We have used in vitro genetic selection to evolve RRE variants that bind to Rev in the presence of neomycin B. Most of the RRE variants selected in the presence of 10 microM neomycin B contain a G48:G71 to A48:A71 substitution. Those selected in 100 microM neomycin B contain either C:A or A:A substitutions at this position. Binding constants for the interaction of neomycin B with the wild-type RRE and a subset of the selected RRE variants were determined using a novel ultrafiltration procedure. CONCLUSIONS: A purine-purine base pair within the bulge region of the RRE core elements is critical for neomycin B binding as well as Rev binding. RRE variants that survive in high concentrations of neomycin do so either by binding Rev better than wild-type (this correlates with the sequence A48:A71) or by binding neomycin poorly (correlating with the sequence C48:A71). Other sequences must also influence both Rev and neomycin B binding.

Base Composition↗
PubMed1996

Localization of HIV-1 RNA in mammalian nuclei.

The Rev protein of human immunodeficiency virus type 1 (HIV-1) facilitates the nuclear export of unspliced and partially spliced viral RNAs. In the absence of Rev, these intron-containing HIV-1 RNAs are retained in the nucleus. The basis for nuclear retention is unclear and is an important aspect of Rev regulation. Here we use in situ hybridization and digital imaging microscopy to examine the intranuclear distributions of intron-containing HIV RNAs and to determine their spatial relationships to intranuclear structures. HeLa cells were transfected with an HIV-1 expression vector, and viral transcripts were localized using oligonucleotide probes specific for the unspliced or spliced forms of a particular viral RNA. In the absence of Rev, the unspliced viral RNAs were predominantly nuclear and had two distinct distributions. First, a population of viral transcripts was distributed as approximately 10-20 intranuclear punctate signals. Actinomycin D chase experiments indicate that these signals represent nascent transcripts. A second, stable population of viral transcripts was dispersed throughout the nucleoplasm excluding nucleoli. Rev promoted the export of this stable population of viral RNAs to the cytoplasm in a time-dependent fashion. Significantly, the distributions of neither the nascent nor the stable populations of viral RNAs coincided with intranuclear speckles in which splicing factors are enriched. Using splice-junction-specific probes, splicing of human beta-globin pre-mRNA occurred cotranscriptionally, whereas splicing of HIV-1 pre-mRNA did not. Taken together, our results indicate that the nucleolus and intranuclear speckles are not involved in Rev regulation, and provide further evidence that efficient splicing signals are critical for cotranscriptional splicing.

Biological Transport↗
PubMed1996

A phase II trial of gemcitabine in patients with 5-FU-refractory pancreas cancer.

PURPOSE: To assess the effect of gemcitabine in patients with metastatic pancreas cancer that had progressed despite prior treatment with 5-FU. PATIENTS AND METHODS: Seventy-four patients were enrolled in this multicenter trial. Alleviation of cancer-related symptoms was the primary endpoint. Sixty-three patients completed a pain stabilization period and were treated with gemcitabine. Clinical Benefit Response was defined as a > or = 50% reduction in pain intensity, > or = 50% reduction in daily analgesic consumption, or > or = 20 point improvement in KPS that was sustained for > or = 4 consecutive weeks. RESULTS: Seventeen of 63 pts (27.0%) attained a Clinical Benefit Response (95% CI: 16.0%-38.0%). The median duration of Clinical Benefit Response was 14 weeks (range: 4-69 weeks). Median survival for patients treated with gemcitabine was 3.85 months (range: 0.3-18.0+ months). Therapy was generally well-tolerated with a low incidence of grade 3 or 4 toxicities. CONCLUSION: Systematic assessment of subjective outcomes can be used to evaluate the clinical impact of new therapies for pancreas cancer, a highly symptomatic disease. Our findings suggest that gemcitabine is a useful palliative agent in patients with 5-FU-refractory pancreas cancer.

Adenocarcinoma↗
PubMed1996

Modeling acne in vitro.

To help elucidate the factors responsible for the infundibular changes seen in acne, the human sebaceous pilosebaceous infundibulum was isolated by microdissection and maintained for 7 d in keratinocyte serum-free medium supplemented with 50 micrograms/ml bovine pituitary extract, 100 units/ml penicillin and streptomycin, 2.5 micrograms/ml amphotericin B and CaCl2(10H2O) to give a final Ca2+ concentration of 2 mM. Infundibular structure was maintained over 7 d in this medium; the pattern of cell division mimicked that in vivo. The rate of cell division was significantly higher than previously described for infundibula maintained in supplemented William's E medium, and moreover did not fall over 7 d. The addition of 1 ng/ml interleukin-1 alpha (IL-1 alpha) caused hypercornification of the infundibulum similar to that seen in comedones; this could be blocked by 1000 ng/ml interleukin-1 receptor antagonist (IL-1ra). In about 20% of subjects there was spontaneous hypercornification of the infundibulum that could be blocked by 1000 ng/ml IL-1ra, suggesting that the infundibulum is capable of synthesising IL-1 alpha. The addition of 5 ng/ml epidermal growth factor or 5 ng/ml transforming growth factor-alpha to the medium caused a disorganisation of the keratinocytes of the infundibulum that resulted in rupturing similar to that seen in the more severe, purulent grades of acne. The addition of 1 microM 13-cis retinoic acid caused a significant reduction in the rate of DNA synthesis and apparent parakeratosis. We are now, therefore, able to model histologically the major infundibular changes in acne.

Acne Vulgaris↗
PubMed1996

Bronchioloalveolar carcinoma.

PURPOSE: To review bronchioloalveolar carcinoma (BAC). MATERIALS AND METHODS: English language articles were identified through a Melvyl Medline Search (1966 to 1995) and through the bibliographies of selected articles. RESULTS: An increase in BAC appears to be responsible for the observed rise in the incidence of adenocarcinoma of the lung. Patients with BAC tend to be younger at diagnosis, are more likely to be female, and less likely to be cigarette smokers when compared with other patients with non-small-cell lung cancer (NSCLC). The etiology of this disease is unclear, but multiple environmental insults have been implicated. There are three subtypes of BAC and the symptoms and prognosis of the disease depend on the subtype and extent of disease, but are generally similar to other histologic types of NSCLC. The radiographic differential diagnosis is broad and includes both benign and malignant diseases. The treatment approach to patients with BAC is similar to those with other types of NSCLC. CONCLUSION: BAC appears to be increasing in incidence, especially in young, nonsmoking females. Three subtypes of the disease exist and are responsible for the variable clinical presentations. Further epidemiologic investigation is needed to elucidate the etiology and pathogenesis of this unique disease.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1996

The SR protein family: pleiotropic functions in pre-mRNA splicing.

A family of proteins with arginine-serine-rich domains has recently come into the limelight of studies on the mechanisms of constitutive and regulated pre-mRNA splicing. Implicated in an ever increasing variety of functions, these proteins act as driving forces during spliceosome assembly and also play decisive roles in alternative splice-site selection, suggesting that they are crucial players in the regulation of splicing during cell differentiation and development.

Animals↗
PubMed1996

Gemcitabine safety overview.

The novel nucleoside analog, gemcitabine, appears to be exceptionally well tolerated. To examine gemcitabine's toxicity profile in detail, an analysis of safety data from 18 single-agent gemcitabine studies has been performed. The studies were across a range of tumor types, but all used a dose regimen of 800 to 1,250 mg/ m2 once a week for 3 weeks followed by a week of rest. Seven hundred ninety patients were included in the analysis. Myelosuppression was found to be mild and short-lived: World Health Organization grades 3 and 4, respectively, were recorded in 6.4% and 0.9% of patients for hemoglobin, in 8.1% and 0.5% for leukocytes, in 18.7% and 5.7% for neutrophils, and in 3.7% and 1.0% for platelets. There was little associated infection or hemorrhage. Mild transaminase increases were common but were rarely dose limiting. In general, renal toxicity was mild, but a few cases of renal failure of uncertain etiology were reported. There was little symptomatic toxicity, with low incidences of the gastrointestinal and hair toxicities normally associated with cytotoxic drugs. However, there was a higher incidence than expected of flu-like symptoms and edema, although these were rarely serious. When the safety data from non-small cell lung cancer studies were analyzed separately, the toxicity findings were similar. Therefore, these analyses in large numbers of patients confirm gemcitabine's favorable safety profile.

Antimetabolites, Antineoplastic↗
PubMed1995

Recognition of bZIP proteins by the human T-cell leukaemia virus transactivator Tax.

Human T-cell leukaemia virus type I (HTLV-I) Tax protein increases the DNA binding of many cellular transcription factors that contain a basic region-leucine zipper (bZIP) DNA-binding domain. bZIP domains comprise a leucine-rich dimerization motif and a basic region that mediates DNA contact. How Tax recognizes diverse bZIPs is not understood. Here we show that no specific sequence of the leucine zipper is required for a Tax response. In contrast, the basic region is essential for the Tax-mediated DNA-binding increase, which can be eliminated by single substitutions of several conserved amino acids. Surprisingly, Tax alters the relative affinity of a bZIP for different DNA binding sites. Thus, through recognition of the conserved basic region. Tax increases DNA binding and modifies DNA site selection. Tax provides a model for how a single auxiliary factor can regulate multiple sequence-specific DNA-binding proteins.

Amino Acid Sequence↗
PubMed1995

A human nucleoporin-like protein that specifically interacts with HIV Rev.

The Rev protein of human immunodeficiency virus type 1 (HIV-1) facilitates the nuclear export of unspliced and partly spliced viral RNAs. Rev contains an RNA binding domain, required for interaction with HIV-1 RNA, and an effector domain, required for RNA-bound Rev to function. The Rev effector domain is believed to interact with a cellular cofactor required for the Rev response and thus HIV-1 replication. Here we report the use of a yeast two-hybrid screen to clone human Rev interacting protein (hRIP), which specifically interacts with the Rev effector domain. This hRIP protein has homology with nucleoporins, a class of proteins that mediate nucleocytoplasmic transport. These and other properties of hRIP are those expected of a Rev cellular cofactor.

Amino Acid Sequence↗
PubMed1995

Distinct binding specificities and functions of higher eukaryotic polypyrimidine tract-binding proteins.

In higher eukaryotes, the polypyrimidine-tract (Py-tract) adjacent to the 3' splice site is recognized by several proteins, including the essential splicing factor U2AF65, the splicing regulator Sex-lethal (Sxl), and polypyrimidine tract-binding protein (PTB), whose function is unknown. Iterative in vitro genetic selection was used to show that these proteins have distinct sequence preferences. The uridine-rich degenerate sequences selected by U2AF65 are similar to those present in the diverse array of natural metazoan Py-tracts. In contrast, the Sxl-consensus is a highly specific sequence, which can help explain the ability of Sxl to regulate splicing of transformer pre-mRNA and autoregulate splicing of its own pre-mRNA. The PTB-consensus is not a typical Py-tract; it can be found in certain alternatively spliced pre-mRNAs that undergo negative regulation. Here it is shown that PTB can regulate alternative splicing by selectively repressing 3' splice sites that contain a PTB-binding site.

Animals↗
PubMed1995

A role for activator-mediated TFIIB recruitment in diverse aspects of transcriptional regulation.

BACKGROUND: Transcription by RNA polymerase II in eukaryotic cells requires the ordered assembly of general transcription factors on the promoter to form a preinitiation complex. Transcriptional activator proteins (activators) stimulate transcription by increasing the rate and/or extent of preinitiation complex assembly. We have shown previously that acidic activators increase the stable association of TFIIB on the promoter, a process we refer to as 'recruitment'. In this study, we provide evidence that diverse activators facilitate TFIIB assembly by a related mechanism. We then investigate the activator-mediated assembly of TFIIB with regard to two aspects of transcription: the distance-dependence of activator function, and reinitiation. RESULTS: We have previously described amino-acid-substitution mutants of TFIIB that are able to support an activator-independent basal level of transcription but do not respond to acidic activators. We now show that these mutants also do not respond to other classes of activators. We demonstrate that this defect is due to a failure of the activators to recruit the mutant TFIIB to the promoter. Activators often lose activity as their distance from the initiation site is increased. We show that this impaired transcriptional activity correlates with a decrease in TFIIB recruitment. Finally, we find that following the initiation of transcription, TFIIB dissociates from the promoter, requiring the activator-mediated reassembly of TFIIB in the preinitiation complex for each new round of transcription. CONCLUSION: We have provided evidence that diverse activators recruit TFIIB to the promoter by a related mechanism. This central step in transcriptional activation is sensitive to promoter architecture, and is required for each new round of transcription.

Gene Expression Regulation↗
PubMed1995

Enhanced E-cadherin expression in epidermal growth factor receptor expressing cells.

Expression of the epidermal growth factor receptor (EGFr) and the cell-cell adhesion molecule E-cadherin have individually been implicated in the biological activity of the most common human malignancies. There is also evidence for colocalization and for a correlation in the expression of these two proteins in human cells. To better define the relationship between these two gene products, we used immunohistochemistry and Western blot analysis to compare E-cadherin expression in various well characterized cell lines lacking expression of EGFr or expressing wild type, functional mutant or non functioning mutant EGFr. Parental NR6 cells, which lack endogenous EGFr, and a derivitive cell line NR6M721, which expresses EGFr lacking tyrosine kinase activity, showed low levels of E-cadherin expression with or without stimulation with EGF. In contrast, the derivative NR6c'973 cell line, which expresses an active EGFr defective in EGF induced internalization and down-regulation and NR6 cells expressing wild type EGFr showed strong E-cadherin expression. These results suggest that EGFr activation may regulate or enhance E-cadherin expression.

3T3 Cells↗