A directed genome evolution method to enhance hydrogen production in Rhodobacter capsulatus.

Nitrogenase-dependent H2 production by photosynthetic bacteria, such as Rhodobacter capsulatus, has been extensively investigated. An important limitation to increase H2 production using genetic manipulation is the scarcity of high-throughput screening methods to detect possible overproducing mutants. Previously, we engineered R. capsulatus strains that emitted fluorescence in response to H2 and used them to identify mutations in the nitrogenase Fe protein leading to H2 overproduction. Here, we used ultraviolet light to induce random mutations in the genome of the engineered H2-sensing strain, and fluorescent-activated cell sorting to detect and isolate the H2-overproducing cells from libraries containing 5 × 105 mutants. Three rounds of mutagenesis and strain selection gradually increased H2 production up to 3-fold. The whole genomes of five H2 overproducing strains were sequenced and compared to that of the parental sensor strain to determine the basis for H2 overproduction. No mutations were present in well-characterized functions related to nitrogen fixation, except for the transcriptional activator nifA2. However, several mutations mapped to energy-generating systems and to carbon metabolism-related functions, which could feed reducing power or ATP to nitrogenase. Time-course experiments of nitrogenase depression in batch cultures exposed mismatches between nitrogenase protein levels and their H2 and ethylene production activities that suggested energy limitation. Consistently, cultivating in a chemostat produced up to 19-fold more H2 than the corresponding batch cultures, revealing the potential of selected H2 overproducing strains.

Genetic and Biochemical Analysis of the Azotobacter vinelandii Molybdenum Storage Protein.

The N2 fixing bacterium Azotobacter vinelandii carries a molybdenum storage protein, referred to as MoSto, able to bind 25-fold more Mo than needed for maximum activity of its Mo nitrogenase. Here we have investigated a plausible role of MoSto as obligate intermediate in the pathway that provides Mo for the biosynthesis of nitrogenase iron-molybdenum cofactor (FeMo-co). The in vitro FeMo-co synthesis and insertion assay demonstrated that purified MoSto functions as Mo donor and that direct interaction with FeMo-co biosynthetic proteins stimulated Mo donation. The phenotype of an A. vinelandii strain lacking the MoSto subunit genes (ΔmosAB) was analyzed. Consistent with its role as storage protein, the ΔmosAB strain showed severe impairment to accumulate intracellular Mo and lower resilience than wild type to Mo starvation as demonstrated by decreased in vivo nitrogenase activity and competitive growth index. In addition, it was more sensitive than the wild type to diazotrophic growth inhibition by W. The ΔmosAB strain was found to readily derepress vnfDGK upon Mo step down, in contrast to the wild type that derepressed Vnf proteins only after prolonged Mo starvation. The ΔmosAB mutation was then introduced in a strain lacking V and Fe-only nitrogenase structural genes (Δvnf Δanf) to investigate possible compensations from these alternative systems. When grown in Mo-depleted medium, the ΔmosAB and mosAB + strains showed low but similar nitrogenase activities regardless of the presence of Vnf proteins. This study highlights the selective advantage that MoSto confers to A. vinelandii in situations of metal limitation as those found in many soil ecosystems. Such a favorable trait should be included in the gene complement of future nitrogen fixing plants.

Expression of a functional oxygen-labile nitrogenase component in the mitochondrial matrix of aerobically grown yeast.

The extreme sensitivity of nitrogenase towards oxygen stands as a major barrier to engineer biological nitrogen fixation into cereal crops by direct nif gene transfer. Here, we use yeast as a model of eukaryotic cell and show that aerobically grown cells express active nitrogenase Fe protein when the NifH polypeptide is targeted to the mitochondrial matrix together with the NifM maturase. Co-expression of NifH and NifM with Nif-specific Fe-S cluster biosynthetic proteins NifU and NifS is not required for Fe protein activity, demonstrating NifH ability to incorporate endogenous mitochondrial Fe-S clusters. In contrast, expression of active Fe protein in the cytosol requires both anoxic growth conditions and co-expression of NifH and NifM with NifU and NifS. Our results show the convenience of using mitochondria to host nitrogenase components, thus providing instrumental technology for the grand challenge of engineering N2-fixing cereals.

Trabectedin in pre-treated patients with advanced or metastatic soft tissue sarcoma: a phase II study evaluating co-treatment with dexamethasone.

PURPOSE: This study assesses the efficacy, toxicity and pharmacokinetic profile of trabectedin with or without prophylactic dexamethasone co-treatment in patients with recurrent advanced soft tissue sarcoma (STS). PATIENTS AND METHODS: Patients were randomized to receive trabectedin as a 3-h infusion every 3 weeks with dexamethasone or placebo in the first cycle, with the alternate in the second cycle and with the patient's choice subsequently. Due to toxicity, the randomized design was modified to open-label to make dexamethasone mandatory and the initial dose (1,650 µg/m(2)) was reduced to 1,500 µg/m(2) and then to 1,300 µg/m(2). RESULTS: Forty-one patients were enrolled and 35 were evaluable for efficacy. One partial response and 18 disease stabilizations were found. The median PFS and OS were 2.1 and 10.2 months, respectively, with the 3- and 6-month PFS rates indicating activity in pretreated STS. Twenty-three and 27 patients developed transient asymptomatic grade 3/4 AST and ALT elevation, respectively, and 21 patients had grade 3/4 neutropenia. Dose reduction from 1,650 µg/m(2) to 1,300 µg/m(2) decreased the incidence of grade 3/4 thrombocytopenia (26% vs. 0%), neutropenia (51% vs. 25%) and AST increase (76% vs. 25% of patients). Four patients died due to drug-related toxicities (3 with placebo). The total body clearance of trabectedin was 28% higher and half-life was 21% lower with dexamethasone compared to placebo, with no differences in volume of distribution. CONCLUSIONS: Trabectedin has confirmed activity in patients with pretreated STS. This study shows that co-treatment with dexamethasone improves the safety of trabectedin by reducing drug-induced hepatotoxicity and myelosuppression.

Efficacy of sequential high-dose doxorubicin and ifosfamide compared with standard-dose doxorubicin in patients with advanced soft tissue sarcoma: an open-label randomized phase II study of the Spanish group for research on sarcomas.

PURPOSE: To assess the progression-free survival (PFS) and antitumor response to standard-dose doxorubicin compared with sequential dose-dense doxorubicin and ifosfamide in first-line treatment of advanced soft tissue sarcoma. PATIENTS AND METHODS: Patients with measurable advanced soft tissue sarcoma, Eastern Cooperative Oncology Group (ECOG) performance status (PS) < 2, between the ages 18 and 65 years, and with adequate bone marrow, liver, and renal function were entered in the study. The stratifications were: ECOG PS (0 v 1), location of metastases, and potentially resectable disease. Patients were randomly assigned to either doxorubicin 75 mg/m(2) given as a bolus injection every 3 weeks for 6 cycles (arm A) or doxorubicin at 30 mg/m(2) per day for 3 consecutive days once every 2 weeks for 3 cycles followed by ifosfamide at 12.5 g/m(2) delivered by continuous infusion over 5 days once every 3 weeks for 3 cycles with filgastrim or pegfilgastrim support (arm B). RESULTS: Between December 2003 and September 2007, 132 patients were entered onto the study. Febrile neutropenia, asthenia, and mucositis were more frequent in the arm B. The interim preplanned analysis for futility allowed the premature closure. Objective responses were observed in 23.4% of assessable patients in arm A and 24.1% in arm B. PFS was 26 weeks in the arm A and 24 weeks in arm B (P = .88). Overall survival did not differ between the two therapeutic arms (P = .14). CONCLUSION: Single-agent doxorubicin remains the standard treatment in fit patients with advanced soft tissue sarcoma.

Secreted MMP9 promotes angiogenesis more efficiently than constitutive active MMP9 bound to the tumor cell surface.

Association of matrix metalloprotease 9 (MMP9) to the cell membrane is considered important in tumor growth and angiogenesis. To dissect this regulatory mechanism, we generated raft and non-raft MMP9 chimeras to force membrane expression in the MCF-7 human breast carcinoma cell line. MMP9 targeting to non-raft cell surface domains rendered a constitutive active membrane MMP9 form, suggesting a contribution by the lipid environment in MMP activation. We generated human breast cancer xenograft models using MCF-7 cells overexpressing secreted and membrane-anchored MMP9. The non-raft MMP9 chimera was constitutively active at the cell membrane in xenografts, but this activation did not correlate with an increase in MMP9-induced angiogenesis. Capillary number and vessel perimeter were specifically increased only in tumors overexpressing wild-type MMP9 (the secreted form); this increase was inhibited when tumors were induced in doxycycline-treated mice. Xenografts from tumor cells overexpressing wild-type MMP9 showed increased vascular endothelial growth factor (VEGF)/VEGFR2 receptor association, which was also dependent on MMP9 activity. These observations indicate that membrane location can influence MMP9 activity in vitro and in vivo, and confirm the relevance of stromal-associated, but not tumor-bound MMP9 in mediating tumor-induced angiogenesis.

Phase I/II study of gemcitabine and vinorelbine plus cisplatin in non-small cell lung cancer.

PURPOSE: We determine the maximum tolerated dose (MTD) and efficacy of gemcitabine plus vinorelbine combined with cisplatin in patients with non-small cell lung cancer (NSCLC). PATIENTS AND METHODS: Chemo naive patients with stage IIIA to IV non-small cell lung cancer received outpatient administration of gemcitabine 1,000 mg/m2 and vinorelbine 25 mg/m2 intravenously on days 1 and 8 every 21 days. Doses of gemcitabine and vinorelbine were escalated by 250 mg/m2 and 5 mg/m2, respectively, at each dose level. Cisplatin was administered at a fixed dose of 50 mg/m2 on days 2 and 9. After the MTD was reached, the study was continued as a phase II trial. RESULTS: From January 1998 to March 1999, sixty-five patients were enrolled. The first 38 patients participated in the phase I evaluation. After 130 cycles, the dose-limiting toxicities were neutropenia, stomatitis, asthenia, and hepatotoxicity occurring at the third and fourth dose levels (doses of gemcitabine/vinorelbine of 1,500/25 and 1,000/30 mg/m2). For the subsequent phase II evaluation, 27 additional patients, out of a total of 53, receiving the MTD of gemcitabine and vinorelbine (1000-1250/25 mg/m2) followed (24 hours later) by cisplatin 50 mg/m2. Thirty one (58%) of 53 assessable patients responded. Objective response for patients with stages III and IV disease, respectively, were 65% and 47%. The median time to progression and the overall survival time were 9 months (95% CI: 5-12) and 11 months (95% CI: 9-13), respectively. World Health Organization toxicity > or = grade 3 neutropenia was registered in 28 (54%) of 52 assessable patients (2% with febrile neutropenia), and > or = grade 3 thrombocytopenia in 15 (29%) patients (4% with bleeding). Nausea/vomiting (> or = grade 2) and asthenia (moderate to severe) occurred in 24 (46%) and 14 (27%) patients, respectively. CONCLUSION: Gemcitabine 1,000-1,250 mg/m2 plus vinorelbine 25 mg/m2 on days 1 and 8, followed by cisplatin 50 mg/m2 24 hours later, is safe for outpatient administration and active in patients with NSCLC.

Phase I/II study of gemcitabine plus vinorelbine in non-small cell lung cancer.

BACKGROUND: Because gemcitabine and vinorelbine have demonstrated single-agent activity in non-small cell lung cancer (NSCLC), we conducted this phase I/II study to determine the maximum tolerated dose (MTD) and activity of these drugs combined. PATIENTS AND METHODS: Patients with inoperable or advanced NSCLC and no prior chemotherapy were treated with gemcitabine plus vinorelbine on days 1 and 8 every 21 days. The initial doses of gemcitabine 1,000 mg/m2 and vinorelbine 25 mg/m2 were escalated by 250 mg/m2 and 5 mg/m2, respectively, in separate patient cohorts until the MTD was established. RESULTS: In phase I, 32 patients received a total of 115 cycles. Dose-limiting toxicities were neutropenia and hepatotoxicity, occurring at the dose level of 1,500 mg/m2 and 30 mg/m2. Thus, the MTD used for phase II was 1,250 mg/m2 and 30 mg/m2. Of 41 patients in phase II, 16 (39%) achieved objective responses (95% confidence interval [CI] 24% to 54%), with a median time to progression of 4.2 months. Overall survival was 9 months (95% CI 5.7 to 12.7 months) and the 1-year survival rate was 31%. World Health Organization (WHO) > or = grade 3 neutropenia and reversible thrombocytosis occurred in 15% and 65% of patients, respectively. Non-hematologic toxicity was mild at all dose levels. Grades 3 and 4 hepatotoxicity were reported in one patient each. CONCLUSION: The combination of 1,250 mg/m2 gemcitabine and 30 mg/m2 vinorelbine on days 1 and 8 every 21 days is well tolerated and active in patients with NSCLC. These results should be confirmed in comparative studies.