Biomedical subjects

M R Green

Publications and source records attributed to M R Green.

At least 37 records · Page 2Linked to original sources

PubMed2001

Sequence-specific interaction between HIV-1 matrix protein and viral genomic RNA revealed by in vitro genetic selection.

The human immunodeficiency virus type-1 matrix protein (HIV-1 MA) is a multifunctional structural protein synthesized as part of the Pr55 gag polyprotein. We have used in vitro genetic selection to identify an RNA consensus sequence that specifically interacts with MA (Kd = 5 x 10(-7) M). This 13-nt MA binding consensus sequence bears a high degree of homology (77%) to a region (nt 1433-1446) within the POL open reading frame of the HIV-1 genome (consensus sequence from 38 HIV-1 strains). Chemical interference experiments identified the nucleotides within the MA binding consensus sequence involved in direct contact with MA. We further demonstrate that this RNA-protein interaction is mediated through a stretch of basic amino acids within MA. Mutations that disrupt the interaction between MA and its RNA binding site within the HIV-1 genome resulted in a measurable decrease in viral replication.

Base Sequence↗

PubMed2001

Rapid identification and characterization of hammerhead-ribozyme inhibitors using fluorescence-based technology.

The ability to rapidly identify small molecules that interact with RNA would have significant clinical and research applications. Low-molecular-weight molecules that bind to RNA have the potential to be used as drugs. Therefore, technologies facilitating the rapid and reliable identification of such activities become increasingly important. We have applied a fluorescence-based assay to screen for modulators of hammerhead ribozyme (HHR) catalysis from a small library of antibiotic compounds. Several unknown potent inhibitors of the hammerhead cleavage reaction were identified and further characterized. Tuberactinomycin A, for which positive cooperativity of inhibition in vitro was found, also reduced ribozyme cleavage in vivo. The assay is applicable to the screening of mixtures of compounds, as inhibitory activities were detected within a collection of 2,000 extracts from different actinomycete strains. This approach allows the rapid, reliable, and convenient identification and characterization of ribozyme modulators leading to insights difficult to obtain by classical methodology.

Anti-Bacterial Agents↗

PubMed2001

Beyond pancreatic cancer: irinotecan and gemcitabine in solid tumors and hematologic malignancies.

Non-platinum combinations including gemcitabine and irinotecan (Gemzar; Eli Lilly and Company, Indianapolis, IN) for the management of a variety of malignancies have started to emerge. Gemcitabine and irinotecan are well-tolerated single agents, each with a broad spectrum of antitumor activity. Preclinical data suggests synergy for the two drugs when used in combination. A phase I trial has defined a well-tolerated combination regimen using both drugs on a day-1, -8 schedule every 3 weeks. Phase II data suggest activity for the combination in pancreatic cancer, and a phase III trial of the two-drug combination versus gemcitabine alone is underway in previously untreated pancreatic cancer patients. Other phase II trials evaluating the impact of this combination on a variety of other tumors, such as non-small cell lung, small cell lung, breast, colorectal, and non-Hodgkin's lymphoma, are either forthcoming or in progress. Semin Oncol 28 (suppl 10):34-43.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

Cerebral venous thrombosis as a complication of Crohn disease: a case report.

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Adolescent↗

PubMed2001

Carboplatin/etoposide/paclitaxel in the treatment of patients with extensive small-cell lung cancer.

The purpose of this study was to examine the safety and efficacy of carboplatin/etoposide/paclitaxel in patients with untreated stage IV non-small-cell lung cancer (NSCLC) and extensive small-cell lung cancer (SCLC). Carboplatin was administered intravenously (i.v.) at an area under the curve (AUC) of 6 with etoposide at either 80 or 100 mg/m2 i.v. days 1-3 and paclitaxel at 175 or 200 mg/m2 i.v. over 3 hours along with 5 g/kg of granulocyte colony-stimulating factor subcutaneously on days 4-18, repeated every 3 weeks for 6 courses. Thirty-one patients (five NSCLC and 26 SCLC) entered into this phase I study. The median age was 63 (range, 42 to 74 years), with 24 males and seven females. The recommended dose level for phase II testing was carboplatin AUC = 6, etoposide 80 mg/m2 days 1-3, and paclitaxel 175 mg/m2 over 3 hours. With seven patients at this level, 14% had grade 4 neutropenia, 14% had grade 4 thrombocytopenia, none had grade 2/3 neurotoxicity, and no toxic deaths occurred. One of five (20%) patients with NSCLC responded, and 19 of 22 (86%) evaluable SCLC patients experienced a response to therapy. SCLC patients had a median survival of 10 months. The combination of carboplatin/etoposide/paclitaxel has significant activity with acceptable toxicity in patients with extensive SCLC.

Journal Article↗

PubMed2001

Docetaxel followed by gemcitabine and irinotecan in solid tumors.

Docetaxel (Taxotere), gemcitabine (Gemzar), and irinotecan (Camptosar, CPT-11) are active single agents in a variety of solid tumors. In combination, synergism may be schedule dependent. Preclinical studies suggested synergistic interactions when docetaxel was administered 24 hours before gemcitabine or irinotecan. The objective of this phase I trial in patients with refractory solid tumors was to determine the maximum tolerated dose of docetaxel followed 24 hours later by gemcitabine and irinotecan. Two different schedules were tested: docetaxel escalated by 5 mg/m2/cohort from an initial dose of 20 mg/m2 on days 1 and 8 (schedule A) or escalated by 15 mg/m2/cohort from 45 mg/m2 on day 8 only (schedule B). In both schedules, docetaxel was given over 1 hour. Gemcitabine and irinotecan were given on days 2 and 9 (arm A) or 1 and 9 (arm B) at fixed doses of 1,000 mg/m2 over 30 minutes and 100 mg/m2 over 90 minutes, respectively. Escalation of docetaxel was planned in groups of three patients, with three additional patients added at the first indication of dose-limiting toxicity. Four dose levels in arm A and one dose level in arm B have been tested. Seventeen patients were evaluable in arm A; one died of an unrelated cause on cycle 1, and another withdrew consent before beginning treatment. Five of six patients were evaluable in arm B; one patient inadvertently received G-CSF on cycle 1. Forty-two cycles have been delivered in arm A (mean; 2.2 cycles/patient), and 25 cycles in arm B (mean, 4.2 cycles/patient); the maximum tolerated dose of docetaxel on arm A was 20 mg/m2. The dose-limiting toxicities were grade 3 diarrhea in one patient, grade 3 infection in two patients, and grade 4 neutropenia for > 4 days in one patient at the 25 mg/m2 level. The dose-limiting toxicities on arm B occurred at the first dose level and included grade 3 diarrhea in one patient, grade 4 diarrhea in one patient, and grade 4 neutropenia for 4 days in another patient. Accrual to schedule B was closed after testing the cohort 1 dose level because testing of a single deescalated docetaxel dose given on day 8 was not considered clinically relevant.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

Irinotecan/gemcitabine combination chemotherapy in pancreatic cancer.

Gemcitabine (Gemzar) and irinotecan (CPT-11, Camptosar) are active cytotoxic drugs against pancreatic cancer. Preclinical data evaluating the combination of gemcitabine and irinotecan suggest dose-dependent synergistic interactions in SCOG small-cell lung cancer and MCF-7 breast cancer cell lines. Two phase I trials of this combination have been reported to date: the day 1 and 8 every-3-week schedule (IrinoGem trial), and the day 1, 8, and 15 every-4-week schedule (MSKCC trial). Both trials aimed to determine the maximum tolerated dose of irinotecan when administered as a 90-minute i.v. infusion either immediately after (IrinoGem) or before or immediately after (MSKCC) gemcitabine at 1,000 mg/m2 by 30-minute i.v. infusion in patients with solid tumors. The achieved maximum tolerated dose of IrinoGem has a higher dose intensity of irinotecan (100 mg/m2 on days 1 and 8, every-3-week cycle) compared with the MSKCC schedule (60 mg/m2 on days 1, 8, and 15, every-4-week trial). In IrinoGem, two of three previously untreated metastatic pancreas cancer patients had durable radiologic partial responses. The third had stable disease with clinical benefit for eight cycles. In addition, a patient with metastatic adenocarcinoma of unknown primary--potentially pancreatic--has had a durable response and is alive more than 30 months after the diagnosis. Preliminary results of a 45-patient multicenter phase II trial with IrinoGem in advanced and metastatic pancreas cancer were recently reported. Toxicity was modest, with no toxic deaths or neutropenic fever. Radiologic response rate was 20% of patients (9 out of 45), and a CA 19-9 decrease of more than 50% from baseline values occurred in 32.5% of patients (13 out of 40). Median survival was 6 months (range: 0.9 to 12.2+ months) and median time to treatment failure was 2.9 months (range: 0.1 to 11.3+ months). A pivotal international multicenter phase III trial comparing IrinoGem to single-agent gemcitabine in advanced and metastatic pancreas cancer is ongoing.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

The current status of docetaxel for advanced non-small cell lung cancer.

Docetaxel is an active single agent in both first- and second-line therapy of patients with advanced non-small cell lung cancer (NSCLC). Randomized trials versus best supportive care have documented an improvement in overall survival for docetaxel therapy in both settings. Docetaxel also produced a significant 1-year survival rate improvement when compared with vinorelbine or ifosfamide as second-line therapy. Docetaxel has been extensively investigated in phase I/II studies in combination with cisplatin, carboplatin, irinotecan and gemcitabine. Substantial activity has been demonstrated. In a randomized phase II trial comparing docetaxel plus cisplatin with docetaxel plus gemcitabine, the efficacy of the two regimens was almost identical (response rates 32 and 34%; 1-year survival rates 42 and 38%). However, the combination of docetaxel with gemcitabine was associated with significantly less grade III/IV neutropenia, diarrhea and nausea/vomiting. Three drug regimens combining docetaxel with, for example, gemcitabine and carboplatin or with ifosfamide and cisplatin, are producing very high response rates in phase II trials. Whether three-drug combinations including docetaxel will result in an improved outcome for patients with advanced NSCLC remains to be determined.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Redundant roles for the TFIID and SAGA complexes in global transcription.

The transcription factors TFIID and SAGA are multi-subunit complexes involved in transcription by RNA polymerase II. TFIID and SAGA contain common TATA-binding protein (TBP)-associated factor (TAF(II)) subunits and each complex contains a subunit with histone acetyltransferase activity. These observations have raised questions about whether the functions of the two complexes in vivo are unique or overlapping. Here we use genome-wide expression analysis to investigate how expression of the yeast genome depends on both shared and unique subunits of these two complexes. We find that expression of most genes requires one or more of the common TAF(II) subunits, indicating that the functions of TFIID and SAGA are widely required for gene expression. Among the subunits shared by TFIID and SAGA are three histone-like TAF(II)s, which have been proposed to form a sub-complex and mediate a common function in global transcription. Unexpectedly, we find that the histone-like TAF(II)s have distinct roles in expression of the yeast genome. Most importantly, we show that the histone acetylase components of TFIID and SAGA (TAF(II)145 and Gcn5) are functionally redundant, indicating that expression of a large fraction of yeast genes can be regulated through the action of either complex.

Acetyltransferases↗

PubMed2000

Distinct classes of yeast promoters revealed by differential TAF recruitment.

The transcription factor TFIID contains the TATA box binding protein (TBP) and multiple TBP-associated factors (TAFs). Here, the association of TFIID components with promoters that either are dependent on multiple TAFs (TAFdep) or have no apparent TAF requirement (TAFind) is analyzed in yeast. At TAFdep promoters, TAFs are present at levels comparable to that of TBP, whereas at TAFind promoters, TAFs are present at levels that approximate background. After inactivation of several general transcription factors, including TBP, TAFs are still recruited by activators to TAFdep promoters. The results reveal two classes of promoters: at TAFind promoters, TBP is recruited in the apparent absence of TAFs, whereas at TAFdep promoters, TAFs are co-recruited with TBP in a manner consistent with direct activator-TAF interactions.

Cross-Linking Reagents↗

PubMed2000

Paclitaxel/ifosfamide or navelbine/ifosfamide chemotherapy for advanced non-small cell lung cancer: CALGB 9532.

In order to explore non-cisplatin containing regimens for advanced non-small cell lung cancer, Cancer and Leukemia Group B conducted a randomized Phase-II study of two novel combinations, paclitaxel/ifosfamide and vinorelbine/ifosfamide. Both regimens were active with a 38% response rate (95% CI: 24%, 53%) and 31% (95% CI: 18%, 47%), respectively. Median survivals were 8.5 and 7.4 months. Toxicity, mostly neutropenia, was acceptable. These two combinations establish a 'proof of principle' that non-cisplatin containing regimens also have activity in this setting.

Adult↗

PubMed2000

TBP-associated factors (TAFIIs): multiple, selective transcriptional mediators in common complexes.

Transcription of eukaryotic structural genes requires the assembly of RNA polymerase II and the general transcription factors (GTFs) on the promoter to form a pre-initiation complex (PIC). Among these, TFIID is the major sequence-specific DNA-binding component; the other GTFs enter the PIC primarily through protein-protein interactions. TFIID is composed of the TATA-box-binding protein (TBP) and multiple TBP-associated factors (TAFIIs). Unexpectedly, TAFIIs have also been found in other multi-subunit complexes involved in transcription. Whereas TBP is a general transcription factor, a variety of in vivo studies have demonstrated that TAFIIs are highly promoter selective. Here I review studies on the role of TAFIIs in genome-wide transcription and their mechanism of action.

Animals↗

PubMed2000

Differential recognition of the polypyrimidine-tract by the general splicing factor U2AF65 and the splicing repressor sex-lethal.

The polypyrimidine-tract (Py-tract) adjacent to 3' splice sites is an essential splicing signal and is recognized by several proteins, including the general splicing factor U2AF65 and the highly specific splicing repressor Sex-lethal (SXL). They both contain ribonucleoprotein-consensus RNA-binding motifs. However, U2AF65 recognizes a wide variety of Py-tracts, whereas SXL recognizes specific Py-tracts such as the nonsex-specific Py-tract of the transformer pre-mRNA. It is not understood how these seemingly similar proteins differentially recognize the Py-tract. To define these interactions, we used chemical interference and protection assays, saturation mutagenesis, and RNAs containing modified nucleotides. We find that these proteins recognize distinct features of the RNA. First, although uracils within the Py-tract are protected from chemical modification by both of these proteins, modification of any one of seven uracils by hydrazine, or any of eight phosphates by ethylnitrosourea strongly interfered with the binding of SXL only. Second, the 2' hydroxyl groups or backbone conformation appeared important for the binding of SXL, but not U2AF65. Third, although any of the bases (cytosine >> adenine > guanine) could substitute for uracils for U2AF65 binding, only guanine partially substituted for certain uracils for SXL binding. The different dependence on individual contacts and nucleotide preference may provide a basis for the different RNA-binding specificities and thus functions of U2AF65 and SXL in 3' splice site choice.

Amino Acid Motifs↗

PubMed2000

Atmospheric oxygen accelerates the induction of a post-mitotic phenotype in human dermal fibroblasts: the key protective role of glutathione.

It has been proposed that ageing of human dermal fibroblasts occurs as a multi-stage process during which cells progress from a mitotic to a post-mitotic state. We describe the development of a simple and novel cell-cloning model for identifying and quantifying the different fibroblast morphotypes associated with the induction of post mitotic behaviour. We have found that under atmospheric (20%) oxygen tension a significant proportion of human dermal fibroblasts are rapidly induced to switch from a mitotic to a post-mitotic phenotype. In contrast, under more physiological (4%) oxygen conditions, the induction of a post-mitotic phenotype is largely prevented. Increasing oxidative stress by addition of hydrogen peroxide or depletion of glutathione also induced a switch from a mitotic to a post-mitotic phenotype in these cells, whereas addition of the anti-oxidant N-acetylcysteine under atmospheric (20%) oxygen tension potently inhibited this process. In addition, a statistically significant correlation was observed between the magnitude of intracellular glutathione depletion and the reduction in the population of mitotic cells in this model. We propose that the switch from a mitotic to a post-mitotic phenotype represents a process of cellular ageing and that standard atmospheric oxygen tension imposes a substantial oxidative stress on dermal fibroblasts which accelerates this process in culture. The data also suggest that intracellular glutathione levels strongly influence the induction of a post-mitotic phenotype and that, by implication, depletion of glutathione may play a significant role in the progression of cellular ageing in human skin.

Acetylcysteine↗

PubMed2000

Radiation and chemotherapy for patients with stage III non-small cell lung cancer.

Nearly 50,000 people in the United States will be diagnosed with stage III non-small cell lung cancer during the year 2000. Over the past 10 years, combined modality therapy has become the standard of care for primary treatment of most of these patients. Numerous studies and meta-analyses document an improvement in survival for patients with stage III disease treated with sequential chemotherapy followed by chest radiation, compared with radiation alone. Some more recent studies have shown a further improvement in survival when the chemotherapy and full-dose radiation are given concurrently. Acute toxicity is increased compared with sequential chemotherapy followed by radiation, but late toxicities seem similar. A current question under study is whether the use of initial chemotherapy followed by concurrent chemoradiotherapy will further improve median and overall survival compared with immediate concurrent therapy alone.

Carcinoma, Non-Small-Cell Lung↗

PubMed2000

Inflammatory mediators in normal, sensitive and diseased skin types.

The role of inflammatory mediators in the pathogenesis and pathophysiology of skin diseases is now widely accepted. We analysed the profiles of inflammatory mediators in normal, sensitive (past history of eczema, but currently patch test negative) and diseased (psoriasis and eczema) skin types to identify the patterns associated with various degrees of inflammatory dermatoses. Compared with normal skin, prostaglandin E2 was increased approximately 3.8-fold (p<0.0002) and 4.7-fold (p<0.0001) in suction blister fluids from sensitive and diseased skin types, respectively. Leukotriene B4 and interleukin-1alpha showed no differences between normal and sensitive skin types. However, in lesional skin from psoriasis and eczema patients, leukotriene B4 was increased approximately 6.6-fold (p<0.0001), whereas interleukin-1alpha was decreased approximately 3.1-fold (p<0.001). Interleukin 6 and tumour necrosis factor-alpha could not discriminate between skin types. We conclude that only prostaglandin E2 showed a significant stepwise increase on progression from normal through sensitive and inflammatory skin diseases. Levels of leukotriene B4 and interleukin-1alpha were also indicative of disease state and may be important in the pathophysiology of these conditions.

Adult↗

PubMed2000

Advances in treatment of inoperable NSCLC: gemcitabine doublets--a promising alternative.

Gemcitabine (Gemzar) was originally approved for use in combination with cisplatin (Platinol) for the treatment of advanced non-small-cell lung cancer (NSCLC). Research began to focus on combining gemcitabine with newer drugs, such as carboplatin (Paraplatin), vinorelbine (Navelbine), the taxanes, and the camptothecins, when it became clear that these agents had potentially increased efficacy and fewer side effects than the standard treatment. This article will briefly review the original experience with the gemcitabine/cisplatin doublet and then examine the experience to date with non-cisplatin-based gemcitabine doublet combinations in the treatment of advanced NSCLC.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2000

Irinotecan in the management of patients with pancreatic cancer.

Synergy with no overlapping toxicities has been demonstrated for the combination of irinotecan (Camptosar, CPT-11) and gemcitabine (Gemzar) in vitro. Results of a single-institution phase I study in which patients with previously untreated pancreatic cancer were given irinotecan and gemcitabine were promising, with two of three patients achieving a partial response. Because of the favorable outcome of the phase I study, a multicenter phase II trial was undertaken in previously untreated patients with pancreatic carcinoma. Data from other sites entering patients in this phase II study have been analyzed, and a multicenter phase III trial of single-agent gemcitabine vs the irinotecan combination in first-line treatment of patients with locally advanced or metastatic pancreatic cancer is underway.

Antineoplastic Agents, Phytogenic↗