Properties of the iron-sulfur cluster electron transfer relay in an [FeFe]-hydrogenase that is tuned for H2 oxidation catalysis.

[FeFe]-hydrogenases catalyze the reversible oxidation of H2 from electrons and protons at an organometallic active site cofactor named the H-cluster. In addition to the H-cluster, most [FeFe]-hydrogenases possess accessory FeS cluster (F-cluster) relays that function in mediating electron transfer with catalysis. There is significant variation in the structural properties of F-cluster relays among the [FeFe]-hydrogenases; however, it is unknown how this variation relates to the electronic and thermodynamic properties, and thus the electron transfer properties, of enzymes. Clostridium pasteurianum [FeFe]-hydrogenase II (CpII) exhibits a large catalytic bias for H2 oxidation (compared to H2 production), making it a notable system for examining if F-cluster properties contribute to the overall function and efficiency of the enzyme. By applying a combination of multifrequency and potentiometric electron paramagnetic resonance, we resolved two electron paramagnetic resonance signals with distinct power- and temperature-dependent properties at g = 2.058 1.931 1.891 (F2.058) and g = 2.061 1.920 1.887 (F2.061), with assigned midpoint potentials of -140 ± 18 mV and -406 ± 12 mV versus normal hydrogen electrode, respectively. Spectral analysis revealed features consistent with spin-spin coupling between the two [4Fe-4S] F-clusters, and possible functional models are discussed that account for the contribution of coupling to the electron transfer landscape. The results signify the interplay of electronic coupling and free energy properties and parameters of the FeS clusters to the electron transfer mechanism through the relay and provide new insight as to how relays functionally complement the catalytic directionality of active sites to achieve highly efficient catalysis.

Crystalline Si Surface Passivation with Nafion for Bulk Defects Detection with Electron Paramagnetic Resonance.

In monocrystalline Si (c-Si) solar cells, identification and mitigation of bulk defects are crucial to achieving a high photoconversion efficiency. To spectroscopically detect defects in the c-Si bulk, it is desirable to passivate the surface defects. Passivation of the c-Si surface with dielectrics such as Al2O3 and SiNx requires deposition at elevated temperatures, which can influence defects in the bulk. Herein, we report on the passivation of different Czochralski (Cz) Si wafer surfaces by an organic copolymer, Nafion. We test the efficacy of the surface passivation at temperatures ranging from 6 to 473 K to detect bulk defects using electron paramagnetic resonance (EPR) spectroscopy. By comparing with state-of-the-art passivation layers, including Al2O3 and liquid HF/HCl, we found that at room temperature, Nafion can provide comparable passivation of n-type Cz Si with an implied open-circuit voltage (iVoc) of 713 mV and a recombination current prefactor J0 of 5 fA/cm2. For p-type Cz Si, we obtained an iVoc of 682 mV with a J0 of 22.4 fA/cm2. Scanning electron microscopy and photoluminescence reveal that Nafion can also be used to passivate the surface of c-Si solar cell fragments scribed from a solar cell module by using a laser. Consistent with previous studies, analysis of the EPR spectroscopy data confirms that the H-terminated surface is necessary, and fixed negative charge in Nafion is responsible for the field-effect passivation. While the surface passivation quality was maintained for almost 24 h, which is sufficient for spectroscopic measurements, the passivation degraded over longer durations, which can be attributed to surface SiOx growth. These results show that Nafion is a promising room-temperature surface passivation technique to study bulk defects in c-Si.

Transitioning to Neoadjuvant Therapy for Resectable Non-Small Cell Lung Cancer: Trends and Surgical Outcomes in a Regionalized Pulmonary Oncology Network.

BACKGROUND: Several regulatory agencies have approved the use of the neoadjuvant chemo-immunotherapy for resectable stage II and III of non-small cell lung cancer (NSCLC) and numerous trials investigating novel agents are underway. However, significant concerns exist around the feasibility and safety of offering curative surgery to patients treated within such pathways. The goal in this study was to evaluate the impact of a transition towards a large-scale neoadjuvant therapy program for NSCLC. METHODS: Medical charts of patients with clinical stage II and III NSCLC who underwent resection from January 2015 to December 2020 were reviewed. The primary outcome was perioperative complication rate between neoadjuvant-treated versus upfront surgery patients. Multivariable logistic regression estimated occurrence of postoperative complications and overall survival was assessed as an exploratory secondary outcome by Kaplan-Meier and Cox-regression analyses. RESULTS: Of the 428 patients included, 106 (24.8%) received neoadjuvant therapy and 322 (75.2%) upfront surgery. Frequency of minor and major postoperative complications was similar between groups (P = .22). Occurrence in postoperative complication was similar in both cohort (aOR = 1.31, 95% CI 0.73-2.34). Neoadjuvant therapy administration increased from 10% to 45% with a rise in targeted and immuno-therapies over time, accompanied by a reduced rate of preoperative radiation therapy use. 1-, 2-, and 5-year overall survival was higher in neoadjuvant therapy compared to upfront surgery patients (Log-Rank P = .017). CONCLUSIONS: No significant differences in perioperative outcomes and survival were observed in resectable NSCLC patients treated by neoadjuvant therapy versus upfront surgery. Transition to neoadjuvant therapy among resectable NSCLC patients is safe and feasible from a surgical perspective.

Structural and biophysical properties of a [4Fe4S] ferredoxin-like protein from Synechocystis sp. PCC 6803 with a unique two domain structure.

Electron carrier proteins (ECPs), binding iron-sulfur clusters, are vital components within the intricate network of metabolic and photosynthetic reactions. They play a crucial role in the distribution of reducing equivalents. In Synechocystis sp. PCC 6803, the ECP network includes at least nine ferredoxins. Previous research, including global expression analyses and protein binding studies, has offered initial insights into the functional roles of individual ferredoxins within this network. This study primarily focuses on Ferredoxin 9 (slr2059). Through sequence analysis and computational modeling, Ferredoxin 9 emerges as a unique ECP with a distinctive two-domain architecture. It consists of a C-terminal iron­sulfur binding domain and an N-terminal domain with homology to Nil-domain proteins, connected by a structurally rigid 4-amino acid linker. Notably, in contrast to canonical [2Fe2S] ferredoxins exemplified by PetF (ssl0020), which feature highly acidic surfaces facilitating electron transfer with photosystem I reaction centers, models of Ferredoxin 9 reveal a more neutral to basic protein surface. Using a combination of electron paramagnetic resonance spectroscopy and square-wave voltammetry on heterologously produced Ferredoxin 9, this study demonstrates that the protein coordinates 2×[4Fe4S]2+/1+ redox-active and magnetically interacting clusters, with measured redox potentials of -420 ± 9 mV and - 516 ± 10 mV vs SHE. A more in-depth analysis of Fdx9's unique structure and protein sequence suggests that this type of Nil-2[4Fe4S] multi-domain ferredoxin is well conserved in cyanobacteria, bearing structural similarities to proteins involved in homocysteine synthesis in methanogens.

Docetaxel-Based Neoadjuvant Chemotherapy Followed by En Bloc Resection for Esophageal Adenocarcinoma: A 15-Year Retrospective Analysis from a Regional Upper Gastrointestinal Cancer Network.

BACKROUND: Real-world, long-term survival outcomes of neoadjuvant, docetaxel-based therapy for esophageal and junctional adenocarcinoma are lacking. This study describes the long-term survival outcomes of patients with esophageal and junctional adenocarcinoma treated with neoadjuvant docetaxel-based chemotherapy and en bloc transthoracic esophagectomy. METHODS: A retrospective cohort analysis of a prospectively maintained database from a regional upper gastrointestinal cancer network in Quebec, Canada, was performed. From January 2007 to December 2021, all patients with locally advanced (cT3 and/or N1) esophageal/Siewert I/II adenocarcinoma treated with neoadjuvant DCFx3 (Docetaxel/Cisplatin/5FU) or FLOTx4 (5FU/Leucovorin/Oxaliplatin/Docetaxel) and transthoracic en bloc esophagectomy were identified. Postoperative, pathological, and survival outcomes were compared. RESULTS: Overall, 236 of 420 patients met the inclusion criteria. Tumor location was esophageal/Siewert I/Siewert II (118/33/85), most were cT3-4 (93.6%) and cN+ (61.0%). DCF and FLOT were used in 127 of 236 (53.8%) and 109 of 236 (46.2%). All neoadjuvant cycles were completed in 87.3% with no difference between the regimens. Operative procedures included Ivor Lewis (81.8%), left thoraco-abdominal esophagectomy (10.6%) and McKeown (7.6%) with an R0 resection in 95.3% and pathological complete response in 9.7% (DCF 12.6%/FLOT 6.4%, p = 0.111). The median lymph node yield was 32 (range 4-79), and 60.6% were ypN+. Median follow-up was longer for the DCF group (74.8 months 95% confidence interval [CI] 4-173 vs. 37.8 months 95% CI 2-119, p <0.001. Overall survival was similar between the groups (FLOT 97.3 months, 78.6-115.8 vs. DCF 92.9, 9.2-106.5, p = 0.420). CONCLUSIONS: Neoadjuvant DCF and FLOT followed by transthoracic en bloc resection are both highly effective regimens for locally advanced esophageal adenocarcinoma with equivalent survival outcomes despite high disease load.

Low-temperature trapping of N2 reduction reaction intermediates in nitrogenase MoFe protein-CdS quantum dot complexes.

The biological reduction of N2 to ammonia requires the ATP-dependent, sequential delivery of electrons from the Fe protein to the MoFe protein of nitrogenase. It has been demonstrated that CdS nanocrystals can replace the Fe protein to deliver photoexcited electrons to the MoFe protein. Herein, light-activated electron delivery within the CdS:MoFe protein complex was achieved in the frozen state, revealing that all the electron paramagnetic resonance (EPR) active E-state intermediates in the catalytic cycle can be trapped and characterized by EPR spectroscopy. Prior to illumination, the CdS:MoFe protein complex EPR spectrum was composed of a S = 3/2 rhombic signal (g = 4.33, 3.63, and 2.01) consistent with the FeMo-cofactor in the resting state, E0. Illumination for sequential 1-h periods at 233 K under 1 atm of N2 led to a cumulative attenuation of E0 by 75%. This coincided with the appearance of S = 3/2 and S = 1/2 signals assigned to two-electron (E2) and four-electron (E4) reduced states of the FeMo-cofactor, together with additional S = 1/2 signals consistent with the formation of E6 and E8 states. Simulations of EPR spectra allowed quantification of the different E-state populations, along with mapping of these populations onto the Lowe-Thorneley kinetic scheme. The outcome of this work demonstrates that the photochemical delivery of electrons to the MoFe protein can be used to populate all of the EPR active E-state intermediates of the nitrogenase MoFe protein cycle.

High Affinity Electrostatic Interactions Support the Formation of CdS Quantum Dot:Nitrogenase MoFe Protein Complexes.

Nitrogenase MoFe protein can be coupled with CdS nanocrystals (NCs) to enable photocatalytic N2 reduction. The nature of interactions that support complex formation is of paramount importance in intermolecular electron transfer that supports catalysis. In this work we have employed microscale thermophoresis to examine binding interactions between 3-mercaptopropionate capped CdS quantum dots (QDs) and MoFe protein over a range of QD diameters (3.4-4.3 nm). The results indicate that the interactions are largely electrostatic, with the strength of interactions similar to that observed for the physiological electron donor. In addition, the strength of interactions is sensitive to the QD diameter, and the binding interactions are significantly stronger for QDs with smaller diameters. The ability to quantitatively assess NC protein interactions in biohybrid systems supports strategies for understanding properties and reaction parameters that are important for obtaining optimal rates of catalysis in biohybrid systems.

Cryo-annealing of Photoreduced CdS Quantum Dot-Nitrogenase MoFe Protein Complexes Reveals the Kinetic Stability of the E4(2N2H) Intermediate.

A critical step in the mechanism of N2 reduction to 2NH3 catalyzed by the enzyme nitrogenase is the reaction of the four-electron/four-proton reduced intermediate state of the active-site FeMo-cofactor (E4(4H)). This state is a junction in the catalytic mechanism, either relaxing by the reaction of a metal bound Fe-hydride with a proton forming H2 or going forward with N2 binding coupled to the reductive elimination (re) of two Fe-hydrides as H2 to form the E4(2N2H) state. E4(2N2H) can relax to E4(4H) by the oxidative addition (oa) of H2 and release of N2 or can be further reduced in a series of catalytic steps to release 2NH3. If the H2 re/oa mechanism is correct, it requires that oa of H2 be associative with E4(2N2H). In this report, we have taken advantage of CdS quantum dots in complex with MoFe protein to achieve photodriven electron delivery in the frozen state, with cryo-annealing in the dark, to reveal details of the E-state species and to test the stability of E4(2N2H). Illumination of frozen CdS:MoFe protein complexes led to formation of a population of reduced intermediates. Electron paramagnetic resonance spectroscopy identified E-state signals including E2 and E4(2N2H), as well as signals suggesting the formation of E6 or E8. It is shown that in the frozen state when pN2 is much greater than pH2, the E4(2N2H) state is kinetically stable, with very limited forward or reverse reaction rates. These results establish that the oa of H2 to the E4(2N2H) state follows an associative reaction mechanism.

Transcriptional immunogenomic analysis reveals distinct immunological clusters in paediatric nervous system tumours.

BACKGROUND: Cancer immunotherapies including immune checkpoint inhibitors and Chimeric Antigen Receptor (CAR) T-cell therapy have shown variable response rates in paediatric patients highlighting the need to establish robust biomarkers for patient selection. While the tumour microenvironment in adults has been widely studied to delineate determinants of immune response, the immune composition of paediatric solid tumours remains relatively uncharacterized calling for investigations to identify potential immune biomarkers. METHODS: To inform immunotherapy approaches in paediatric cancers with embryonal origin, we performed an immunogenomic analysis of RNA-seq data from 925 treatment-naïve paediatric nervous system tumours (pedNST) spanning 12 cancer types from three publicly available data sets. RESULTS: Within pedNST, we uncovered four broad immune clusters: Paediatric Inflamed (10%), Myeloid Predominant (30%), Immune Neutral (43%) and Immune Desert (17%). We validated these clusters using immunohistochemistry, methylation immune inference and segmentation analysis of tissue images. We report shared biology of these immune clusters within and across cancer types, and characterization of specific immune cell frequencies as well as T- and B-cell repertoires. We found no associations between immune infiltration levels and tumour mutational burden, although molecular cancer entities were enriched within specific immune clusters. CONCLUSIONS: Given the heterogeneity of immune infiltration within pedNST, our findings suggest personalized immunogenomic profiling is needed to guide selection of immunotherapeutic strategies.

Postoperative Outcomes and Quality of Life After Left Thoracoabdominal Esophagogastrectomy: Contrasting Esophagogastrostomy with Esophagojejunostomy.

BACKGROUND: Following left thoracoabdominal (LTA) esophagogastrectomy, gastrointestinal continuity can be re-established via esophagogastrostomy or esophagojejunostomy. We explored how the method of reconstruction impacted postoperative outcomes and quality of life (QoL). METHODS: From January 2007 to January 2022, patients undergoing LTA were identified from a single center's prospectively maintained database. Following esophagogastrectomy or extended total gastrectomy, an esophagogastrostomy (GAS) or Roux-en-Y esophagojejunostomy (R-Y) was fashioned. Postoperative outcomes were compared according to the method of reconstruction. The Functional Assessment of Cancer Therapy-Esophagus (FACT-E) questionnaire compared QoL. RESULTS: Of the 147 LTA patients identified, 135 (92%) were included-97 GAS (72%) and 38 R-Y patients (28%). R-Y patients had more ypT3/4 lesions (97% vs. 61%, p ≤ 0.001) and a similar incidence of ypN+/M+ disease. Anastomotic leaks were more common among GAS patients (17% vs. 3%, p = 0.023), however grade 3/4 complications (26.6% vs. 19.4%, p = 0.498), reoperation, intensive care admission, hospital representation and readmission were similar. FACT-E data were available for 68/97 (70%) GAS patients and 22/38 (58%) R-Y patients, with scores for 80/21/24/18/23/24 patients at baseline/preoperatively/1 month/3-6 months/1-3 years/3+ years postoperatively, respectively. Comparing between the groups, the scores were similar at each timepoint. FACT-E improved between baseline and preoperatively (79, 34-124 vs. 102, 81-123, p = 0.027). Only at 3+ years were postoperative scores equivalent to preoperative values. GAS patients had more reflux and esophagitis >6 months postoperatively (54% vs. 13%, p = 0.048; 62% vs. 0%, p ≤ 0.001). CONCLUSION: While the type of reconstruction did not affect QoL, it did affect the postoperative course.

The 8th Edition TNM Stage Reclassification of T4 Non-Small Cell Lung Cancer: A Granular Examination of Short and Long-Term Outcomes.

INTRODUCTION: Whilst the American Joint Committee on Cancer 7th edition (AJCC7) classified pT4 non-small-cell lung cancers (NSCLC) as those with extra-pulmonary invasion, the revised 8th edition (AJCC8) included tumors > 7cm regardless of extra-pleural spread. We examined perioperative and long-term outcomes of classical T4 definitions with patients whose tumors were greater than 7cm without extra-pulmonary invasion. MATERIALS AND METHODS: A retrospective single center cohort study was performed. All consecutive patients with pT4 lesions between 2011 and 2018 were identified based on either the AJCC7 or AJCC8 classification. Clinicopathological variables were extracted and compared in a univariate manner. A multivariate Cox regression analysis was performed to assess factors associated with overall survival. RESULTS: Forty patients were allocated to AJCC7 and 118 to AJCC8. Patients in the former were more likely to have positive lymph nodes, synchronous metastasis, multifocal disease and lymphovascular invasion. AJCC7 patients were more likely to undergo pneumonectomy despite significantly more being treated with neoadjuvant therapy. Ninety-day mortality was higher in the AJCC7 group. There was no difference in long-term overall survival. On multivariate analysis male gender, squamous cell histology and increasing tumor size were associated with an increased risk of death. CONCLUSION: Although long-term outcomes were similar, the heterogenicity within the AJCC8 classification emphasizes the need to contextualize the perioperative outcomes for patients with pT4 NSCLC. These data are important for future iterations of the TNM classification in view of emerging neoadjuvant options for patients with cT4 operable NSCLC.

Myeloma immunoglobulin rearrangement and translocation detection through targeted capture sequencing.

Multiple myeloma is a plasma cell neoplasm characterized by clonal immunoglobulin V(D)J signatures and oncogenic immunoglobulin gene translocations. Additional subclonal genomic changes are acquired with myeloma progression and therapeutic selection. PCR-based methods to detect V(D)J rearrangements can have biases introduced by highly multiplexed reactions and primers undermined by somatic hypermutation, and are not readily extended to include mutation detection. Here, we report a hybrid-capture approach (CapIG-seq) targeting the 3' and 5' ends of the V and J segments of all immunoglobulin loci that enable the efficient detection of V(D)J rearrangements. We also included baits for oncogenic translocations and mutation detection. We demonstrate complete concordance with matched whole-genome sequencing and/or PCR clonotyping of 24 cell lines and report the clonal sequences for 41 uncharacterized cell lines. We also demonstrate the application to patient specimens, including 29 bone marrow and 39 cell-free DNA samples. CapIG-seq shows concordance between bone marrow and cfDNA blood samples (both contemporaneous and follow-up) with regard to the somatic variant, V(D)J, and translocation detection. CapIG-seq is a novel, efficient approach to examining genomic alterations in myeloma.

The Contribution of Proton-Donor pKa on Reactivity Profiles of [FeFe]-hydrogenases.

The [FeFe]-hydrogenases are enzymes that catalyze the reversible activation of H2 coupled to the reduction-oxidation of electron carriers. Members of the different taxonomic groups of [FeFe]-hydrogenases display a wide range of preference, or bias, for H2 oxidation or H2 production reactions, despite sharing a common catalytic cofactor, or H-cluster. Identifying the properties that control reactivity remains an active area of investigation, and models have emerged that include diversity in the catalytic site coordination environments and compositions of electron transfer chains. The kinetics of proton-coupled electron transfer at the H-cluster might be expected to be a point of control of reactivity. To test this hypothesis, systematic changes were made to the conserved cysteine residue that functions in proton exchange with the H-cluster in the three model enzymes: CaI, CpII, and CrHydA1. CaI and CpII both employ electron transfer accessory clusters but differ in bias, whereas CrHydA1 lacks accessory clusters having only the H-cluster. Changing from cysteine to either serine (more basic) or aspartate (more acidic) modifies the sidechain pKa and thus the barrier for the proton exchange step. The reaction rates for H2 oxidation or H2 evolution were surveyed and measured for model [FeFe]-hydrogenases, and the results show that the initial proton-transfer step in [FeFe]-hydrogenase is tightly coupled to the control of reactivity; a change from cysteine to more basic serine favored H2 oxidation in all enzymes, whereas a change to more acidic aspartate caused a shift in preference toward H2 evolution. Overall, the changes in reactivity profiles were profound, spanning 105 in ratio of the H2 oxidation-to-H2 evolution rates. The fact that the change in reactivity follows a common trend implies that the effect of changing the proton-transfer residue pKa may also be framed as an effect on the scaling relationship between the H-cluster di(thiolmethyl)amine (DTMA) ligand pKa and E m values of the H-cluster. Experimental observations that support this relationship, and how it relates to catalytic function in [FeFe]-hydrogenases, are discussed.

A site-differentiated [4Fe-4S] cluster controls electron transfer reactivity of Clostridium acetobutylicum [FeFe]-hydrogenase I.

One of the many functions of reduction-oxidation (redox) cofactors is to mediate electron transfer in biological enzymes catalyzing redox-based chemical transformation reactions. There are numerous examples of enzymes that utilize redox cofactors to form electron transfer relays to connect catalytic sites to external electron donors and acceptors. The compositions of relays are diverse and tune transfer thermodynamics and kinetics towards the chemical reactivity of the enzyme. Diversity in relay design is exemplified among different members of hydrogenases, enzymes which catalyze reversible H2 activation, which also couple to diverse types of donor and acceptor molecules. The [FeFe]-hydrogenase I from Clostridium acetobutylicum (CaI) is a member of a large family of structurally related enzymes where interfacial electron transfer is mediated by a terminal, non-canonical, His-coordinated, [4Fe-4S] cluster. The function of His coordination was examined by comparing the biophysical properties and reactivity to a Cys substituted variant of CaI. This demonstrated that His coordination strongly affected the distal [4Fe-4S] cluster spin state, spin pairing, and spatial orientations of molecular orbitals, with a minor effect on reduction potential. The deviations in these properties by substituting His for Cys in CaI, correlated with pronounced changes in electron transfer and reactivity with the native electron donor-acceptor ferredoxin. The results demonstrate that differential coordination of the surface localized [4Fe-4S]His cluster in CaI is utilized to control intermolecular and intramolecular electron transfer where His coordination creates a physical and electronic environment that enables facile electron exchange between electron carrier molecules and the iron-sulfur cluster relay for coupling to reversible H2 activation at the catalytic site.

Neoadjuvant Prehabilitation Therapy for Locally Advanced Non-Small-Cell Lung Cancer: Optimizing Outcomes Throughout the Trajectory of Care.

BACKGROUND: Prehabilitation is well established for improving outcomes in cancer surgery. Combining prehabilitation with neoadjuvant treatments may provide an opportunity to rapidly initiate cancer-directed therapy while improving functional status in preparation for local consolidation. In this proof-of-concept study, we analyzed non-small-cell lung cancer patients who underwent simultaneous prehabilitation and neoadjuvant therapy. PATIENTS AND METHODS: We retrospectively analyzed all patients who underwent neoadjuvant treatment for non-small-cell lung cancer followed by curative intent surgery between 2015 and 2021. Patients who were screened for the prehabilitation program were identified. The screening included assessment of physical performance, nutritional status, and signs of anxiety and depression. RESULTS: We identified a total of 141 patients who underwent neoadjuvant therapy. Twenty patients were screened to undergo a prehabilitation program. Four patients did not complete the exercise program (1 surgical intervention too soon, 1 drop-out after the first session, and 2 patients were deemed fit without intervention). The postoperative median length of stay was 2 days (range 1-18). Patients improved their 6-minute-walk test despite undergoing neoadjuvant treatment by a mean of 33 meters (± 50, P = .1). Self-reported functional status (DASI) showed significant improvement by a mean of 10 points (± 11, P = .03), and HADS-anxiety-score was significantly reduced after the prehabilitation program by a mean of 1.5 points (± 1, P = .005). CONCLUSION: Neoadjuvant prehabilitation therapy is feasible and associated with encouraging results. The performance of all measures remains a logistic challenge. With multimodal strategies for lung cancer treatment becoming key to optimal outcomes, neoadjuvant prehabilitation therapy is a concept worthy of prospective multi-center evaluation.

The influence of electron utilization pathways on photosystem I photochemistry in Synechocystis sp. PCC 6803.

The capacity of cyanobacteria to adapt to highly dynamic photon flux and nutrient availability conditions results from controlled management and use of reducing power, and is a major contributing factor to the efficiency of photosynthesis in aquatic environments. The response to changing conditions includes modulating gene expression and protein-protein interactions that serve to adjust the use of electron flux and mechanisms that control photosynthetic electron transport (PET). In this regard, the photochemical activity of photosystem I (PSI) reaction centers can support balancing of cyclic (CEF) and linear electron flow (LEF), and the coupling of redox carriers for use by electron utilization pathways. Therefore, changes in the utilization of reducing power might be expected to result in compensating changes at PSI as a means to support balance of electron flux. To understand this functional relationship, we investigated the properties of PSI and its photochemical activity in cells that lack flavodiiron 1 catalyzed oxygen reduction activity (ORR1). In the absence of ORR1, the oxygen evolution and consumption rates declined together with a shift in the oligomeric form of PSI towards monomers. The effect of these changes on PSI energy and electron transfer properties was examined in isolated trimer and monomer fractions of PSI reaction centers. Collectively, the results demonstrate that PSI photochemistry is modulated through coordination with the depletion of electron demand in the absence of ORR1.

The Clinically Actionable Molecular Profile of Early versus Late-Stage Non-Small Cell Lung Cancer, an Individual Age and Sex Propensity-Matched Pair Analysis.

Background: Despite meticulous surgery for non-small cell lung cancer (NSCLC), relapse is as high as 70% at 5 years. Many institutions do not conduct reflexive molecular testing on early stage specimens, although targeted gene therapy may extend life by years in the event of recurrence. This ultimately delays definitive treatment with additional biopsy risking suboptimal tissue acquisition and quality for molecular testing. Objective: To compare molecular profiles of genetic alterations in early and late NSCLC to provide evidence that reflexive molecular testing provides clinically valuable information. Methods: A single-center propensity matched retrospective analysis was conducted using prospectively collected data. Adults with early and late-stage NSCLC had tissue subject to targeted panel-based NGS. Frequencies of putative drivers were compared, with 1:3 matching on the propensity score; p < 0.05 deemed statistically significant. Results: In total, 635 NSCLC patients underwent NGS (59 early, 576 late); 276 (43.5%) females; age 70.9 (±10.2) years; never smokers 140 (22.0%); 527 (83.0%) adenocarcinomas. Unadjusted frequencies of EGFR mutations were higher in the early cohort (30% vs. 18%). Following adjustment for sex and smoking status, similar frequencies for both early and late NSCLC were observed for variants in EGFR, KRAS, ALK, MET, and ROS1. Conclusion: The frequency of clinically actionable variants in early and late-stage NSCLC was found to be similar, providing evidence that molecular profiling should be performed on surgical specimens. This pre-determined profile is essential to avoid treatment delay for patients who will derive clinical benefit from targeted systemic therapy, in the high likelihood of subsequent relapse.

Factors predicting recurrence in thymic epithelial neoplasms.

OBJECTIVES: Thymic epithelial neoplasms (TENs) represent a heterogeneous group of rare thoracic malignancies. We analysed the clinicopathological features, survival outcomes, risk factors, and patterns of recurrence in patients undergoing resection. METHODS: Records were reviewed for adult patients with TEN who underwent resection from 2006 to 2019. Survival rates were assessed using the Kaplan-Meier method. Univariable and multivariable analyses were performed using the log-rank test and Cox proportional hazards model. RESULTS: A total of 100 patients were analysed (51 females, median age 58 years). Thymoma was the most common histology (n = 92), followed by thymic carcinoma (n = 5) and thymic neuroendocrine tumour (n = 3). Stage II (Masaoka) tumours were most common (n = 51), followed by stage I (n = 27). World Health Organization B2/B3 was the most prominent histological subtype (n = 34). Complete resection (R0) was achieved in 91 patients: 86/92 thymoma, 4/5 thymic carcinoma and 1/3 neuroendocrine tumour. The most common treatment modality was surgery alone in 72 patients, followed by surgery and radiation therapy in 24, and adjuvant chemoradiotherapy in 3 patients. Only one patient with thymic carcinoma received neoadjuvant chemotherapy. The 10-year overall and disease-free survival rates were 86.6% and 83.9%, respectively. Recurrence was most common in neuroendocrine tumours (3/3). Risk factors for recurrence identified on multivariable analyses were: R1/2 resection (hazard ratio 9.30; 95% confidence interval 1.82-36.1), TEN subtype (hazard ratio 8.08; 95% confidence interval 1.24-34.6), and presence of lymphovascular invasion (hazard ratio 9.56; 95% confidence interval 2.56-25.8). CONCLUSIONS: Complete resection remains critical in patients with TEN. Incomplete resection, high-risk histology, and lymphovascular invasion highlight the need for effective adjuvant modalities. Given the rarity of these diseases, emphasis must be placed on collaborative research conducted on TEN.

Changes in Perioperative Platelet Lymphocyte Ratio Predict Survival in Oesophago-Gastric Adenocarcinoma.

BACKGROUND: Platelet to lymphocyte ratio (PLR) is associated with survival in oesophageal cancer. We explored whether PLR changes during different stages of treatment correlate with survival outcomes. METHODS: A retrospective single-centre study was performed. Consecutive patients who received neoadjuvant chemotherapy followed by surgery for oesophageal adenocarcinoma were identified. Changes in PLR were calculated during two time periods: the first spanning the neoadjuvant period (T1); the second the perioperative period (T2). Differences in PLR were calculated for clinicopathological variables during both T1 and T2 and for variables with regards to their association with median overall survival (OS). Variables found to be significant on univariate analysis were included in a multivariate Cox regression model. Using ROC analysis, optimal cut-offs for PLR changes were identified and plotted on a Kaplan-Meir curve. RESULTS: Of the 370 patients identified, 110 (29.7%) were included in the analysis. During T1 a positive correlation was noted between higher positive lymph node ratio and PLR change. During T2, PLR change was positively higher in patients who suffered major postoperative complications. Median survival for the cohort as a whole was 42.3 months and 5-year OS was 57.3%. Survival at 5 years was associated with lower PLR changes during T2. On univaraite analysis, median OS was significantly less for patients with a tumour size > 3 cm, poor differentiation and change in PLR ≥ 43.4 during T2. The latter two variables remained significant on multivariate analysis. Using the same PLR threshold, the survival curve comparing changes in PLR during T2 remained statistically significant. CONCLUSION: Perioperative PLR changes are highly prognostic of survival outcomes in patients treated for oesophageal adenocarcinoma.