Ribosome subunit attrition and activation of the p53-MDM4 axis dominate the response of MLL-rearranged cancer cells to WDR5 WIN site inhibition.

The chromatin-associated protein WD Repeat Domain 5 (WDR5) is a promising target for cancer drug discovery, with most efforts blocking an arginine-binding cavity on the protein called the 'WIN' site that tethers WDR5 to chromatin. WIN site inhibitors (WINi) are active against multiple cancer cell types in vitro, the most notable of which are those derived from MLL-rearranged (MLLr) leukemias. Peptidomimetic WINi were originally proposed to inhibit MLLr cells via dysregulation of genes connected to hematopoietic stem cell expansion. Our discovery and interrogation of small-molecule WINi, however, revealed that they act in MLLr cell lines to suppress ribosome protein gene (RPG) transcription, induce nucleolar stress, and activate p53. Because there is no precedent for an anticancer strategy that specifically targets RPG expression, we took an integrated multi-omics approach to further interrogate the mechanism of action of WINi in human MLLr cancer cells. We show that WINi induce depletion of the stock of ribosomes, accompanied by a broad yet modest translational choke and changes in alternative mRNA splicing that inactivate the p53 antagonist MDM4. We also show that WINi are synergistic with agents including venetoclax and BET-bromodomain inhibitors. Together, these studies reinforce the concept that WINi are a novel type of ribosome-directed anticancer therapy and provide a resource to support their clinical implementation in MLLr leukemias and other malignancies.

Family as a Pathway to Suicidal Behaviors Through Depression Symptoms and Internalized Homophobia.

Research consistently highlights how systemic and social factors can adversely impact mental health, and the potential buffering effects of family support, yet raced sexual minorities are vastly underrepresented among these studies. As rates of suicide increase among Black people and remain high among men and those in gender and sexually diverse communities, this study sought to examine to relationships between family dynamics and suicidality among young Black men who have sex with men (MSM) in young adulthood. We used an online survey to conduct a logistic regression to examine family factors (family support, open family communication, other adult support, and other adult value), depression symptoms, and internalized homophobia on suicide attempts. The conceptualization of the study's design and interpretation of the results were informed by minority stress theory and the phenomenological variant of ecological systems theory. The results indicate that higher levels of family support and open family communication were associated with lower levels of suicidality. Implications for future research and applications for healthcare providers and human services professionals who support young Black MSM in emerging adulthood are discussed.

Lactate Utilization Enables Metabolic Escape to Confer Resistance to BET Inhibition in Acute Myeloid Leukemia.

Impairing the BET family coactivator BRD4 with small-molecule inhibitors (BETi) showed encouraging preclinical activity in treating acute myeloid leukemia (AML). However, dose-limiting toxicities and limited clinical activity dampened the enthusiasm for BETi as a single agent. BETi resistance in AML myeloblasts was found to correlate with maintaining mitochondrial respiration, suggesting that identifying the metabolic pathway sustaining mitochondrial integrity could help develop approaches to improve BETi efficacy. Herein, we demonstrated that mitochondria-associated lactate dehydrogenase allows AML myeloblasts to utilize lactate as a metabolic bypass to fuel mitochondrial respiration and maintain cellular viability. Pharmacologically and genetically impairing lactate utilization rendered resistant myeloblasts susceptible to BET inhibition. Low-dose combinations of BETi and oxamate, a lactate dehydrogenase inhibitor, reduced in vivo expansion of BETi-resistant AML in cell line and patient-derived murine models. These results elucidate how AML myeloblasts metabolically adapt to BETi by consuming lactate and demonstrate that combining BETi with inhibitors of lactate utilization may be useful in AML treatment. SIGNIFICANCE: Lactate utilization allows AML myeloblasts to maintain metabolic integrity and circumvent antileukemic therapy, which supports testing of lactate utilization inhibitors in clinical settings to overcome BET inhibitor resistance in AML. See related commentary by Boët and Sarry, p. 950.

Ribosome subunit attrition and activation of the p53-MDM4 axis dominate the response of MLL-rearranged cancer cells to WDR5 WIN site inhibition.

The chromatin-associated protein WD Repeat Domain 5 (WDR5) is a promising target for cancer drug discovery, with most efforts blocking an arginine-binding cavity on the protein called the "WIN" site that tethers WDR5 to chromatin. WIN site inhibitors (WINi) are active against multiple cancer cell types in vitro, the most notable of which are those derived from MLL-rearranged (MLLr) leukemias. Peptidomimetic WINi were originally proposed to inhibit MLLr cells via dysregulation of genes connected to hematopoietic stem cell expansion. Our discovery and interrogation of small molecule WIN site inhibitors, however, revealed that they act in MLLr cell lines to suppress ribosome protein gene (RPG) transcription, induce nucleolar stress, and activate p53. Because there is no precedent for an anti-cancer strategy that specifically targets RPG expression, we took an integrated multi-omics approach to further interrogate the mechanism of action of WINi in MLLr cancer cells. We show that WINi induce depletion of the stock of ribosomes, accompanied by a broad yet modest translational choke and changes in alternative mRNA splicing that inactivate the p53 antagonist MDM4. We also show that WINi are synergistic with agents including venetoclax and BET-bromodomain inhibitors. Together, these studies reinforce the concept that WINi are a novel type of ribosome-directed anti-cancer therapy and provide a resource to support their clinical implementation in MLLr leukemias and other malignancies.

TLR3 agonism augments CD47 inhibition in acute myeloid leukemia.

CD47-SIRPa is a myeloid check point pathway that inhibits phagocytosis of cells lacking markers for self-recognition. Tumor cells can overexpress CD47 and bind to SIRPa on macrophages, preventing phagocytosis. CD47 expression is enhanced and correlated with a negative prognosis in Acute Myeloid Leukemia (AML), with its blockade leading to cell clearance. ALX90 is an engineered fusion protein with high-affinity for CD47. Composed of the N-terminal D1 domain of SIRPα genetically linked to an inactive Fc domain from human IgG, ALX90 is designed to avoid potential toxicity of CD47-expressing red blood cells. Venetoclax (VEN) is a specific B-cell lymphoma-2 (BCL-2) inhibitor that can restore apoptosis in malignant cells. In AML VEN is combined with azanucleosides to induce superior remission rates, however treatment for refractory/relapse is an unmet need. We questioned whether the anti-tumor activity of a VEN based regimen can be augmented through CD47 inhibition (CD47i) in AML. Human AML cell lines were sensitive to ALX90 and its addition increased efficacy of a VEN+AZA regimen in vivo. However, CD47i failed to clear bone marrow tumor burden in PDX models. We hypothesized that in cases of high medullary tumor burden, loss of resident macrophages reduced ALX efficiency. Therefore, we attempted to enhance this medullary macrophage population with agonism of TLR3 via Poly(I:C), which led to expansion and activation of medullary macrophages in in vivo AML PDX models and potentiated CD47i. In summary, the addition of Poly(I:C) can enhance medullary macrophage populations to potentiate the phagocytosis merited by therapeutic inhibition of CD47.

Phylogenomic investigation of lampreys (Petromyzontiformes).

The history of lamprey evolution has been contentious due to limited morphological differentiation and limited genetic data. Available data has produced inconsistent results, including in the relationship among northern and southern species and the monophyly of putative clades. Here we use whole genome sequence data sourced from a public database to identify orthologs for 11 lamprey species from across the globe and build phylogenies. The phylogeny showed a clear separation between northern and southern lamprey species, which contrasts with some prior work. We also find that the phylogenetic relationships of our samples of two genera, Lethenteron and Eudontomyzon, deviate from the taxonomic classification of these species, suggesting that they require reclassification.

Asynchronous student-generated flip videos facilitate student learning and assessment in a large-enrollment introductory human physiology course.

Oral demonstration of knowledge is an effective learning and assessment strategy. It has been shown that generating explanations to oneself, or self-explaining, can improve student understanding of information. This can be achieved via student-generated videos. The quantitative effects of student-generated videos on learning and assessment in postsecondary education are unknown. To our knowledge, this is the first study to analyze the effects asynchronous student-generated videos have on student learning and assessment in a large-enrollment (∼400 students), undergraduate physiology course. Students were charged with making self-generated videos discussing major physiological concepts and uploading these videos to Flip for assessment. Flip is an online, social education platform for asynchronous video-based discussion. In the present study, we combined four semesters (n = 1,100 students) of Flip data and analyzed the effects it had on student examination performance. Specifically, we first analyzed how students performed on exam questions corresponding to their Flip prompts in comparison to students not assigned those prompts [25/44 (57%) were statistically significantly different]. Second, we analyzed the association between Flip prompt score and performance on corresponding exam questions [39/44 (89%) were statistically significantly different]. Third, we analyzed the association between cumulative Flip score and performance on all corresponding, and noncorresponding exam questions. Finally, we analyzed the association between cumulative Flip score and averaged exam performance. There was a positive association (r = 0.54). Taken together, our data suggest that asynchronous student-generated Flip videos can facilitate student learning and assessment in a large-enrollment, undergraduate physiology course.NEW & NOTEWORTHY Oral demonstration of knowledge is an effective learning and assessment strategy. Student-generated videos have been shown to improve learning and assessment in secondary education. To our knowledge, this is the first study to analyze the effects asynchronous student-generated Flip videos have on student learning and assessment in postsecondary education. The results of the present study suggest that asynchronous student-generated Flip videos can facilitate student learning and assessment in a large-enrollment (∼400 students), undergraduate physiology course.

A bad time to die? Exploring bereaved families/wha-nau experiences of end-of-life care under COVID-19 restrictions: a qualitative interview study.

Background: There have been international concerns raised that, during the COVID-19 pandemic, there was an absence of good palliative care resulting in poor end-of-life care experiences. To date, there have been few studies considering the pandemic's impact on people dying from non-COVID-19 causes and their families and friends. In particular, there has been very less empirical research in relation to end-of-life care for Indigenous, migrant and minoritised ethnic communities. Objectives: To explore bereaved next-of-kin's views and experiences of end-of-life care under COVID-19 pandemic regulations. Design: This qualitative study involved in-depth one-off interviews with 30 ethnically diverse next-of-kin who had a family member die in the first year of the pandemic in Aotearoa, New Zealand. Methods: Interviews were conducted by ethnically matched interviewers/interviewees. A reflexive thematic analysis was used to explore and conceptualise their accounts. Results: A key finding was that dying alone and contracting COVID-19 were seen as equally significant risks by bereaved families. Through this analysis, we identified five key themes: (1) compromised connection; (2) uncertain communication; (3) cultural safety; (4) supported grieving and (5) silver linings. Conclusion: This article emphasises the importance of enabling safe and supported access for family/whanau to be with their family/wha-nau member at end-of-life. We identify a need for wider provision of bereavement support. We recommend that policy makers increase resourcing of palliative care services to ensure that patients and their families receive high-quality end-of-life care, both during and post this pandemic. Policy makers could also promote a culturally-diverse end-of-life care work force and the embedding of culturally-safety practices across a range of institutions where people die.

Ethnoracial differences in workplace drug testing and policies on positive drug tests in the United States.

BACKGROUND: Drug testing is widely implemented as a work-based prevention strategy for employee substance use. However, it has raised concerns about its potential use as a punitive measure in the workplace where racialized/ethnic workers are over-represented. This study examines the rates of exposure to workplace drug testing among ethnoracial workers in the United States and the potential differences in the employers' responses to positive test results. METHODS: A nationally-representative sample of 121,988 employed adults was examined using the 2015-2019 National Survey on Drug Use and Health data. The rates of exposure to workplace drug testing were estimated separately for ethnoracial workers. Then we used multinomial logistic regression to test differences in employers' responses to the first positive drug test results across ethnoracial subgroups. RESULTS: Since 2002, Black workers reported 15-20% points higher rates of having a workplace drug testing policy than Hispanic or White workers. When tested positive for drug use, Black and Hispanic workers were more likely to be fired than White workers. When tested positive, Black workers were more likely to be referred to treatment/counseling services while Hispanic workers were less likely to be referred compared to White workers. CONCLUSION: Black workers' disproportionate exposure to drug testing and punitive responses in the workplace may potentially place individuals with substance use problems out of the workforce, limiting their access to treatment/other resources available via their workplaces. Also, Hispanic workers' limited accessibility to treatment and counseling services when tested positive for drug use requires attention to address unmet needs.

COVID-19 risk perception and vaccine acceptance in individuals with self-reported chronic respiratory or autoimmune conditions.

BACKGROUND: COVID-19 disproportionately affects those with preexisting conditions, but little research has determined whether those with chronic diseases view the pandemic itself differently - and whether there are differences between chronic diseases. We theorized that while individuals with respiratory disease or autoimmune disorders would perceive greater threat from COVID-19 and be more supportive of non-pharmaceutical interventions (NPIs), those with autoimmune disorders would be less likely to support vaccination-based interventions. METHODS: We conducted a two-wave online survey conducted in February and November 2021 asking respondents their beliefs about COVID-19 risk perception, adoption and support of interventions, willingness to be vaccinated against COVID-19, and reasons for vaccination. Regression analysis was conducted to assess the relationship of respondents reporting a chronic disease and COVID-19 behaviors and attitudes, compared to healthy respondents adjusting for demographic and political factors. RESULTS: In the initial survey, individuals reporting a chronic disease had both stronger feelings of risk from COVID-19 as well as preferences for NPIs than healthy controls. The only NPI that was still practiced significantly more compared to healthy controls in the resample was limiting trips outside of the home. Support for community-level NPIs was higher among individuals reporting a chronic disease than healthy controls and remained high among those with respiratory diseases in sample 2. Vaccine acceptance produced more divergent results: those reporting chronic respiratory diseases were 6% more willing to be vaccinated than healthy controls, while we found no significant difference between individuals with autoimmune diseases and healthy controls. Respondents with chronic respiratory disease and those with autoimmune diseases were more likely to want to be vaccinated to protect themselves from COVID-19, and those with an autoimmune disease were more likely to report fear of a bad vaccine reaction as the reason for vaccine hesitancy. In the resample, neither those with respiratory diseases nor autoimmune diseases reported being more willing to receive a booster vaccine than healthy controls. CONCLUSIONS: It is not enough to recognize the importance of health in determining attitudes: nuanced differences between conditions must also be recognized.

Selective inhibition of MCL1 overcomes venetoclax resistance in a murine model of myelodysplastic syndromes.

Treatment for myelodysplastic syndromes (MDS) remains insufficient due to clonal heterogeneity and lack of effective clinical therapies. Dysregulation of apoptosis is observed across MDS subtypes regardless of mutations and represents an attractive therapeutic opportunity. Venetoclax (VEN), a selective inhibitor of anti-apoptotic protein B-cell lymphoma- 2 (BCL2), has yielded impressive responses in older patients with acute myeloid leukemia (AML) and high risk MDS. BCL2 family anti-apoptotic proteins BCL-XL and induced myeloid cell leukemia 1 (MCL1) are implicated in leukemia survival, and upregulation of MCL1 is seen in VEN-resistant AML and MDS. We determined in vitro sensitivity of MDS patient samples to selective inhibitors of BCL2, BCL-XL and MCL1. While VEN response positively correlated with MDS with excess blasts, all MDS subtypes responded to MCL1 inhibition. Treatment with combined VEN + MCL1 inhibtion was synergistic in all MDS subtypes without significant injury to normal hematopoiesis and reduced MDS engraftment in MISTRG6 mice, supporting the pursuit of clinical trials with combined BCL2 + MCL1 inhibition in MDS.

Management of Severe Hypomagnesemia as the Primary Electrolyte Abnormality with a Delayed Onset of Clinical Signs as a Result of Refeeding Syndrome in a Cat.

This case report describes severe hypomagnesemia in a cat attributed to refeeding syndrome with an onset of clinical signs from the magnesium deficiency apparent on the twelfth day following initiation of feeding. The patient initially presented in a state of cachexia from apparent malnutrition after missing from the owners care for five months. The patient was initially discharged five days after the initiation of feeding with only a mild hypokalemia apparent and requiring supplementation and returned for outpatient management. The patient presented through the emergency department on the twelfth day following the onset of feeding with the clinical signs of acute lethargy, vomiting, generalized tremors and a seizure episode and had a severe total hypomagnesemia on diagnostic bloodwork. The patient's clinical signs resolved following emergency treatment with parenteral magnesium sulfate as a continuous rate infusion and was later managed with oral magnesium hydroxide for a prolonged period of time. Electrolyte abnormalities and associated clinical signs typically occur between two and five days after initiation of feeding and up to ten days after starting food intake in humans with anorexia nervosa. This case report highlights that hypomagnesemia, while not the most common electrolyte disturbance to occur with refeeding syndrome, can occur without other significant electrolyte changes and can cause clinical signs greater than ten days following refeeding to a starving patient. This magnesium deficiency required prolonged treatment, but the patient made a complete recovery.

COVID-19 risk perception and vaccine acceptance in individuals with chronic disease.

Background: COVID-19 disproportionately affects those with preexisting conditions, but little research has determined whether those with chronic diseases view the pandemic itself differently - and whether there are differences between chronic diseases. We theorized that while individuals with respiratory disease or autoimmune disorders would perceive greater threat from COVID-19 and be more supportive of nonpharmaceutical interventions (NPIs), those with autoimmune disorders would be less likely to support vaccination-based interventions. Methods: We conducted a two-wave online survey conducted in February and November 2021 asking respondents their beliefs about COVID-19 risk perception, adoption and support of interventions, willingness to be vaccinated against COVID-19, and reasons for vaccination. Regression analysis was conducted to assess the relationship of respondents reporting a chronic disease and COVID-19 behaviors and attitudes, compared to healthy respondents adjusting for demographic and political factors. Results: In the initial survey, individuals reporting a chronic disease had stronger both stronger feelings of risk from COVID-19 as well as preferences for NPIs than healthy controls. The only NPI that was still practiced significantly more compared to healthy controls in the resample was limiting trips outside of the home. Support for community-level NPIs was higher among individuals reporting a chronic disease than healthy controls and remained high among those with respiratory diseases in sample 2. Vaccine acceptance produced more divergent results: those reporting chronic respiratory diseases were 6% more willing to be vaccinated than healthy controls, while we found no significant difference between individuals with autoimmune diseases and healthy controls. Respondents with chronic respiratory disease and those with autoimmune diseases were more likely to want to be vaccinated to protect themselves from COVID-19, and those with an autoimmune disease were more likely to report fear of a bad vaccine reaction as the reason for vaccine hesitancy. In the resample, neither those with respiratory diseases nor autoimmune diseases reported being more willing to receive a booster vaccine than healthy controls. Conclusions: It is not enough to recognize the importance of health in determining attitudes: nuanced differences between conditions must also be recognized.

Pevonedistat and azacitidine upregulate NOXA (PMAIP1) to increase sensitivity to venetoclax in preclinical models of acute myeloid leukemia.

Dysregulation of apoptotic machinery is one mechanism by which acute myeloid leukemia (AML) acquires a clonal survival advantage. B-cell lymphoma protein-2 (BCL2) overexpression is a common feature in hematologic malignancies. The selective BCL2 inhibitor, venetoclax (VEN) is used in combination with azacitidine (AZA), a DNAmethyltransferase inhibitor (DNMTi), to treat patients with AML. Despite promising response rates to VEN/AZA, resistance to the agent is common. One identified mechanism of resistance is the upregulation of myeloid cell leukemia-1 protein (MCL1). Pevonedistat (PEV), a novel agent that inhibits NEDD8-activating enzyme, and AZA both upregulate NOXA (PMAIP1), a BCL2 family protein that competes with effector molecules at the BH3 binding site of MCL1. We demonstrate that PEV/AZA combination induces NOXA to a greater degree than either PEV or AZA alone, which enhances VEN-mediated apoptosis. Herein, using AML cell lines and primary AML patient samples ex vivo, including in cells with genetic alterations linked to treatment resistance, we demonstrate robust activity of the PEV/VEN/AZA triplet. These findings were corroborated in preclinical systemic engrafted models of AML. Collectively, these results provide rational for combining PEV/VEN/AZA as a novel therapeutic approach in overcoming AML resistance in current therapies.

Second Report of PDE10A-BRAF Fusion in Pediatric Spindle Cell Sarcoma With Infantile Fibrosarcoma-Like Morphology Suggesting PDE10A-BRAF Fusion Is a Recurrent Event.

Infantile/congenital fibrosarcoma (IFS) is the most common soft tissue tumor in children less than one year of age. The most common anatomic site of IFS is in the extremities or trunk, and rarely in the abdomen or retroperitoneum. Approximately 70-90% of cases are characterized by a distinct t(12;15)(p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion. As such, TRK inhibitors are considered frontline therapy in TRK-fusion positive IFS. The ETV6-NTRK3 fusion is also detected in congenital mesoblastic nephroma (CMN) and less frequently in myeloid leukemias, secretory breast carcinoma, and mammary-type secretory carcinoma of the skin and salivary glands. Infrequently, cases of tumors with IFS-like morphology without the characteristic ETV6-NTRK3 gene fusion have been identified. Herein, an ETV6-NTRK3 fusion negative spindle cell sarcoma with IFS-like morphology subjected to genomic profiling revealed a PDE10A-BRAF fusion, a fusion event that has been detected previously in an isolated case of undifferentiated infantile sarcoma.

The delta isoform of phosphatidylinositol-3-kinase predominates in chronic myelomonocytic leukemia and can be targeted effectively with umbralisib and ruxolitinib.

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome/myeloproliferative neoplasm overlap syndrome characterized by monocytic proliferation in the presence of dysplastic bone marrow changes, inflammatory symptoms, and propensity for transformation to acute myeloid leukemia (AML), with a poor prognosis and limited treatment options. Unlike the α and ß isoforms, the phosphatidylinositol-3-kinase (PI3K)-δ signaling protein is predominantly expressed by hematopoietic cells and therefore has garnered interest as a potential target for the treatment of lymphomas and leukemias. We revealed a pattern of increased PIK3CD:PIK3CA ratio in monocytic M5 AML patients and cell lines, and this ratio correlated with responsiveness to pharmacological PI3K-δ inhibition in vitro. Because CMML is a disease defined by monocytic clonal proliferation, we tested the PI3K-δ inhibitor umbralisib as a single agent and in combination with the JAK1/2 inhibitor ruxolitinib, in CMML. Our ex vivo experiments with primary CMML patient samples revealed synergistic inhibition of viability and clonogenicity with this combination. Phospho-specific flow cytometry revealed that dual inhibition had the unique ability to decrease STAT5, ERK, AKT, and S6 phosphorylation simultaneously, which offers a mechanistic hypothesis for the enhanced efficacy of the combination treatment. These preclinical data indicate promising activity by co-inhibition of PI3K-δ and JAK1/2 and support the use of ruxolitinib + umbralisib combination therapy in CMML under active clinical investigation.

Author Correction: Enhancement of trans-cleavage activity of Cas12a with engineered crRNA enables amplified nucleic acid detection.

A Correction to this paper has been published: https://doi.org/10.1038/s41467-020-20117-z.

Enhancement of trans-cleavage activity of Cas12a with engineered crRNA enables amplified nucleic acid detection.

The CRISPR-Cas12a RNA-guided complexes have tremendous potential for nucleic acid detection but are limited to the picomolar detection limit without an amplification step. Here, we develop a platform with engineered crRNAs and optimized conditions that enabled us to detect various clinically relevant nucleic acid targets with higher sensitivity, achieving a limit of detection in the femtomolar range without any target pre-amplification step. By extending the 3'- or 5'-ends of the crRNA with different lengths of ssDNA, ssRNA, and phosphorothioate ssDNA, we discover a self-catalytic behavior and an augmented rate of LbCas12a-mediated collateral cleavage activity as high as 3.5-fold compared to the wild-type crRNA and with significant improvement in specificity for target recognition. Particularly, the 7-mer DNA extension to crRNA is determined to be universal and spacer-independent for enhancing the sensitivity and specificity of LbCas12a-mediated nucleic acid detection. We perform a detailed characterization of our engineered ENHANCE system with various crRNA modifications, target types, reporters, and divalent cations. With isothermal amplification of SARS-CoV-2 RNA using RT-LAMP, the modified crRNAs are incorporated in a paper-based lateral flow assay that can detect the target with up to 23-fold higher sensitivity within 40-60 min.

O2 No Longer the Go2: A Systematic Review and Meta-Analysis Comparing the Effects of Giving Perioperative Oxygen Therapy of 30% FiO2 to 80% FiO2 on Surgical Site Infection and Mortality.

OBJECTIVE: To determine the effects of perioperative high (80%) versus low (30%) fraction of inspired oxygen (FiO2) on surgical site infection (SSI) and mortality in adult surgical patients. BACKGROUND: The routine use of high fraction perioperative oxygen in patients is "standard of care" and recommended by the World Health Organisation; however, whether there is truly any benefit to this therapy has been challenged by some authors. Questions have also been raised about the possibility of harm from oxygen therapy. METHOD: Randomised control trials comparing high-to-low FiO2 were located by searching MEDLINE, Embase, CENTRAL and Web of Science. The primary outcomes were SSI up to 15 days and up to any time point postoperatively and mortality up to 30 days. The data were analysed using random effects meta-analysis. RESULTS: Twelve studies involving 10,212 participants were included. At 15 days postoperatively, and at the longest point of post-operative follow-up, there was no statistically significant reduction in the risk of SSI when comparing patients who received a perioperative FiO2 of 30% to those with an FiO2 of 80% (RR 1.41, 95% CI 1.00-2.01, p 0.05 and RR 1.23, 95% CI 1.00-1.51, p 0.05). There was no statistically significant difference in mortality between the 30% FiO2 and the 80% FiO2 groups (RR 1.12, 95% CI 0.56-2.22, p 0.76). CONCLUSION: This meta-analysis showed no statistically significant difference in post-operative SSI or mortality when comparing patients receiving an FiO2 of 80% to those receiving an FiO2 of 30%.