A mathematical model of the tetrapyrrole biosynthesis pathway

The tetrapyrrole biosynthesis pathway is a key part in chlorophyll production and is essential for plant survival. It involves numerous interacting compounds and, crucially, light. The understanding of the complex regulation processes involved has been the focus of extensive experimental research providing a large source of data. A particular set of data, concerned with the modelling described in this report, involves 24 hour timecourse data from seedlings exposed to constant light, following a three day period of growth from seed in darkness. This data includes the levels of key components such as chlorophyll, ATP, chlorophyllide and proto-chlorophyllide. Amongst the questions posed in the study-group were: i) Can the timecourse data be predicted by a model? ii) Can it predict the dierences in levels of various components in found mutant strains. To address these questions, we present in this report a model consisting of a coupled system of nonlinear ODEs that describes a simplied version of the tetrapyrrole pathway based on mass action laws. Model simulations produced results that agree qualitatively well with most, but not all, of the available timecourse data obtained from wild-type and mutant strains. Nearly all of the model's parameters are not known, so the values used in these simulations are based on estimates of the relative timescales of the reactions. An attempt at improving these estimates using data tting techniques is also discussed

Sustained Progression-Free Survival Benefit of Rituximab Maintenance in Patients With Follicular Lymphoma : Long-Term Results of the PRIMA Study

PURPOSE The PRIMA study (ClinicalTrials.gov identifier: NCT00140582) established that 2 years of rituximab maintenance after first-line immunochemotherapy significantly improved progression-free survival (PFS) in patients with follicular lymphoma compared with observation. Here, we report the final PFS and overall survival (OS) results from the PRIMA study after 9 years of follow-up and provide a final overview of safety. METHODS Patients (> 18 years of age) with previously untreated high-tumor-burden follicular lymphoma were nonrandomly assigned to receive one of three immunochemotherapy induction regimens. Responding patients were randomly assigned (stratified by induction regimen, response to induction treatment, treatment center, and geographic region) 1:1 to receive 2 years of rituximab maintenance (375 mg/m(2), once every 8 weeks), starting 8 weeks after the last induction treatment, or observation (no additional treatment). All patients in the extended follow-up provided their written informed consent (data cutoff: December 31, 2016). RESULTS In total, 1,018 patients completed induction treatment and were randomly assigned to rituximab maintenance (n = 505) or observation (n = 513). Consent for the extended follow-up was provided by 607 patients (59.6%) of 1,018 (rituximab maintenance, n = 309; observation, n = 298). After data cutoff, median PFS was 10.5 years in the rituximab maintenance arm compared with 4.1 years in the observation arm (hazard ratio, 0.61; 95% CI, 0.52 to 0.73; P <.001). No OS difference was seen in patients randomly assigned to rituximab maintenance or observation (hazard ratio, 1.04; 95% CI, 0.77 to 1.40; P = .7948); 10-year OS estimates were approximately 80% in both study arms. No new safety signals were observed. CONCLUSION Rituximab maintenance after induction immunochemotherapy provides a significant long-term PFS, but not OS, benefit over observation.Peer reviewe

Dynamical feedback between circadian clock and sucrose availability explains adaptive response of starch metabolism to various photoperiods

Plants deal with resource management during all their life. During the day they feed on photosynthetic carbon, sucrose, while storing a part into starch for night use. Careful control of carbon partitioning, starch degradation and sucrose export rates is crucial to avoid carbon starvation, insuring optimal growth whatever the photoperiod. Efficient regulation of these key metabolic rates can give an evolutionary advantage to plants. Here we propose a model of adaptive starch metabolism in response to various photoperiods. We assume the three key metabolic rates to be circadian regulated in leaves and that their phases of oscillations are shifted in response to sucrose starvation. We performed gradient descents for various photoperiod conditions to find the corresponding optimal sets of phase shifts that minimize starvation. Results at convergence were all consistent with experimental data: i) diurnal starch profile showed linear increase during the day and linear decrease at night; ii) shorter photoperiod tended to increase starch synthesis speed while decreasing its degradation speed during the longer night; iii) sudden early dusk showed slower starch degradation during the longer night. Profiles that best explained observations corresponded to circadian regulation of all rates. This theoretical study would establish a framework for future research on feedback between starch metabolism and circadian clock as well as plant productivity

Rituximab combined with chemotherapy and interferon in follicular lymphoma patients: results of the GELA-GOELAMS FL2000 study

The FL2000 study was undertaken to evaluate the combination of the anti-CD20 monoclonal antibody rituximab with chemotherapy plus interferon in the first-line treatment of follicular lymphoma patients with a high tumor burden. Patients were randomly assigned to receive either 12 courses of the chemotherapy regimen CHVP (cyclophosphamide, adriamycin, etoposide, and prednisolone) plus interferon-alpha 2a (CHVP+I arm) over 18 months or 6 courses of the same chemotherapy regimen combined with 6 infusions of 375 mg/m(2) rituximab and interferon for the same time period (R-CHVP+I arm). After a median follow-up of 5 years, event-free survival estimates were, respectively, 37% (95% confidence interval [CI], 29%-44%) and 53% (95% CI, 45%-60%) in the CHVP+I and R-CHVP+I arm (P = .001). Five-year overall survival estimates were not statistically different in the CHVP+I (79%; 95% CI, 72%-84%) and R-CHVP+I (84%; 95% CI, 78%-84%) arms. In a multivariate regression analysis, event-free survival was significantly influenced by both the Follicular Lymphoma International Prognostic Index score (hazard ratio = 2.08; 95% CI, 1.6%-2.8%) and the treatment arm (hazard ratio = 0.59; 95% CI, 0.44%-0.78%). With a 5-year follow-up, the combination of rituximab with CHVP+I provides superior disease control in follicular lymphoma patients despite a shorter duration of chemotherapy. This study's clinical trial was registered at the National Institutes of Health website as no. NCT00136552. (Blood. 2008;112:4824-4831

FDG-PET driven consolidation strategy in diffuse large B-cell lymphoma: Final results of a randomized phase II study.

Dose-dense induction and upfront consolidation with autologous stem cell transplantation (ASCT) remain controversial issues when treating high-risk diffuse large B cell lymphoma patients. GELA designed a randomized phase II trial evaluating the efficacy of either R-ACVBP or R-CHOP14 induction and a PET-driven ASCT or standard immunochemotherapy (SIC) consolidation in aaIPI2-3 patients. PET was done at baseline, after 2 (PET2) and 4 induction cycles (PET4) and centrally assessed using international harmonization project (IHP) criteria. PET2-/PET4- patients were assigned SIC, PET2+/PET4- ASCT and PET4+ patients treated with investigator' choice. The primary end-point was the 2007 international working group CR rate after induction. ΔSUVmax PET assessment was explored. 211 patients were randomized to R-ACVBP (n=109) or R-CHOP14 (n=102). PET4-/CR rates were 53/47% with R-ACVBP and 41/39% with R-CHOP14 (CR 95%CI: 38%-67% v 28%-54%; p=0.076). Consolidation in the R-ACVBP and R-CHOP14 arms was SIC in 26% and 23% of patients and ASCT in 28% and 18%, respectively. PET4 positivity was higher with R-CHOP14 (54% v 41%; p=0.08) leading to more salvage therapy (37% v 26%; p=0.07) and lower EFS (4y-EFS= 31% v 43%; p70% was associated with better outcome (4y-PFS: 84% v 35%; 4y-OS: 91% v 57%, p<0.0001) whatever the consolidation. Superiority of R-ACVBP over R-CHOP14 was not established as IHP criteria did not properly reflect disease control. ΔSUVmax may help better select patients needing alternative to SIC, including ASCT

Oxaliplatin before autologous transplantation in combination with high-dose cytarabine and rituximab provides longer disease control than cisplatin or carboplatin in patients with mantle-cell lymphoma: results from the LyMA prospective trial

National audienceLyMA trial has demonstrated the benefit of rituximab maintenance after autologous stem cell transplantation (ASCT) in previously untreated mantle-cell lymphoma patients (MCL). Induction consisted of four courses of R-DHAP (rituximab, dexamethasone, high-dose cytarabine, and platinum derivative). The platinum derivative (PD) choice was free: R-DHA-cisplatin, R-DHA-carboplatin, or R-DHA-oxaliplatin. We investigated the prognostic impact of each PD. PFS and OS calculated from inclusion and investigated in an intention-to-treat (ITT) (= 298) and per-protocol analyses (PP) (n = 227). R-DHACis, R-DHACa, or R-DHAOx were used at first cycle in 184, 76, and 38 patients, respectively. Overall, 71 patients (59 in the R-DHACis) required a change in PD, mainly because of PD toxicity. In ITT-analysis, PFS in the R-DHACis and R-DHACa groups were similar (4-year PFS of 65%), while R-DHAOx had a better PFS (4-year PFS of 65% versus 86.5%, respectively, HR = 0.44, p = 0.02). The 4-year OS was 92% for R-DHAOx versus 75.9% for R-DHACis/DHACa (HR = 0.37, p = 0.03). Similar results were yielded in the PP analysis. Low MIPI and R-DHAOx were independent favorable prognostic markers for both PFS (HR = 0.44, p = 0.035) and OS (HR = 0.36, p = 0.045). In vitro and in silico analyses confirmed that oxaliplatin has an anti-MCL cytotoxic effect that differs from that of other PD. R-DHAOx before ASCT provides better outcome in transplantation eligible young MCL patients