Age-, experience- and avoidance learning-related synaptic plasticity in leaf-cutting ants

Dissertação de mestrado em Biologia Celular e Molecular apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.A proteína mixed-lineage kinase 3 (MLK3) é uma cinase de serina/treonina vastamente expressa que está envolvida em diferentes funções fisiológicas como proliferação, apoptose, sobrevivência e migração celular. Ao responder a mitogénios e estímulos de stress regula a sinalização das MAPK através da activação das vias da ERK, JNK e p38. O seu domínio cinase é crucial para fosforilar e consequentemente activar moléculas alvo. Contudo, a activação da MLK3 nem sempre é requerida para a modulação de algumas funções por ela induzidas. A MLK3 pode ainda funcionar como proteína scaffold, ligando diferentes vias de sinalização. Mutações na MLK3 foram descritas, pela primeira vez, em 2010 pelo nosso grupo. Nesse mesmo trabalho, foi demonstrado que mutações missense na MLK3 possuíam potencial transformante e tumorigénico. Duas dessas mutações (P252H e R799C) mostraram um comportamento invasivo. Tendo em conta estas informações nós estabelecemos linhas celulares (HEK293) que expressam de uma forma estável estas mutações para assim identificar os efeitos celulares a elas associados e avaliar quais os alvos moleculares dependentes desses dois mutantes da MLK3. Verificámos que a mutação no domínio cinase da MLK3 (P252H) confere propriedades diferentes quando comparada com a mutação localizada no domínio rico em prolina. A mutação P252H parece induzir uma maior migração celular, enquanto a mutação R799C parece interferir com a diferenciação celular. Além disso, nós verificámos que ambas as mutações regulam a via do WNT de maneira distinta, seja através da activação da via canónica ou da não canónica. Em resumo, o trabalho descrito nesta tese mostra que duas das mutações na MLK3, previamente descritas, interferem com vias de sinalização cruciais do desenvolvimento colorectal e neste sentido contribuem para a tumorigénese colorectal.Mixed-lineage kinase 3 (MLK3) is a serine/threonine kinase widely expressed and involved in different physiological functions, such as proliferation, apoptosis, cell survival and cell migration. Responding to mitogens and stress stimuli it regulates MAPK signalling through activation of ERK, JNK, p38 pathways. Its kinase domain is crucial to phosphorylate and thus activate downstream targets. However, MLK3 activation is not always required to MLK3-induced modulation of some cellular functions. MLK3 may indeed function as a scaffold protein, linking different signalling pathways. MLK3 mutations were reported, for the first time, in 2010 by our group. Missense MLK3 mutations were found to be able to harbour transforming and tumourigenic potential. Two of the mutations (P252H and R799C) were found to show an invasive behaviour. Taking this data into account we generated HEK293 stable cell lines harbouring these mutations in order to identify associated cellular effects and evaluate which molecular targets were dependent of these two MLK3 mutants. We found that a mutation in MLK3 kinase domain (P252H) confers different properties when compared to a one localized in the proline-rich domain. P252H mutation seems to induce increased cell migration, while R799C seems to interfere with cell differentiation. Furthermore, we verified that both mutations regulate the WNT pathway in distinct manner, either through the activation of the canonical or non-canonical pathway. In summary, we showed that two of the MLK3 mutations previously described interfere with crucial pathways of colorectal development and in this way contribute to colorectal tumourigenesis

Time to antibiotics is unrelated to outcome in pediatric patients with fever in neutropenia presenting without severe disease during chemotherapy for cancer.

Fever in neutropenia (FN) remains an unavoidable, potentially lethal complication of chemotherapy. Timely administration of empirical broad-spectrum intravenous antibiotics has become standard of care. But the impact of time to antibiotics (TTA), the lag period between recognition of fever or arrival at the hospital to start of antibiotics, remains unclear. Here we aimed to analyze the association between TTA and safety relevant events (SRE) in data from a prospective multicenter study. We analyzed the association between time from recognition of fever to start of antibiotics (TTA) and SRE (death, admission to intensive care unit, severe sepsis and bacteremia) with three-level mixed logistic regression. We adjusted for possible triage bias using a propensity score and stratified the analysis by severity of disease at presentation with FN. We analyzed 266 FN episodes, including 53 (20%) with SRE, reported in 140 of 269 patients recruited from April 2016 to August 2018. TTA (median, 120 min; interquartile range, 49-180 min) was not associated with SRE, with a trend for less SREs in episodes with longer TTA. Analyses applying the propensity score suggested a relevant triage bias. Only in patients with severe disease at presentation there was a trend for an association of longer TTA with more SRE. In conclusion, TTA was unrelated to poor clinical outcome in pediatric patients with FN presenting without severe disease. We saw strong evidence for triage bias which could only be partially adjusted

Time to antibiotics is unrelated to outcome in pediatric patients with fever in neutropenia presenting without severe disease during chemotherapy for cancer

Fever in neutropenia (FN) remains an unavoidable, potentially lethal complication of chemotherapy. Timely administration of empirical broad-spectrum intravenous antibiotics has become standard of care. But the impact of time to antibiotics (TTA), the lag period between recognition of fever or arrival at the hospital to start of antibiotics, remains unclear. Here we aimed to analyze the association between TTA and safety relevant events (SRE) in data from a prospective multicenter study. We analyzed the association between time from recognition of fever to start of antibiotics (TTA) and SRE (death, admission to intensive care unit, severe sepsis and bacteremia) with three-level mixed logistic regression. We adjusted for possible triage bias using a propensity score and stratified the analysis by severity of disease at presentation with FN. We analyzed 266 FN episodes, including 53 (20%) with SRE, reported in 140 of 269 patients recruited from April 2016 to August 2018. TTA (median, 120 min; interquartile range, 49-180 min) was not associated with SRE, with a trend for less SREs in episodes with longer TTA. Analyses applying the propensity score suggested a relevant triage bias. Only in patients with severe disease at presentation there was a trend for an association of longer TTA with more SRE. In conclusion, TTA was unrelated to poor clinical outcome in pediatric patients with FN presenting without severe disease. We saw strong evidence for triage bias which could only be partially adjusted

How the oxygen tolerance of a [NiFe]-hydrogenase depends on quaternary structure

‘Oxygen-tolerant’ [NiFe]-hydrogenases can catalyze H(2) oxidation under aerobic conditions, avoiding oxygenation and destruction of the active site. In one mechanism accounting for this special property, membrane-bound [NiFe]-hydrogenases accommodate a pool of electrons that allows an O(2) molecule attacking the active site to be converted rapidly to harmless water. An important advantage may stem from having a dimeric or higher-order quaternary structure in which the electron-transfer relay chain of one partner is electronically coupled to that in the other. Hydrogenase-1 from E. coli has a dimeric structure in which the distal [4Fe-4S] clusters in each monomer are located approximately 12 Å apart, a distance conducive to fast electron tunneling. Such an arrangement can ensure that electrons from H(2) oxidation released at the active site of one partner are immediately transferred to its counterpart when an O(2) molecule attacks. This paper addresses the role of long-range, inter-domain electron transfer in the mechanism of O(2)-tolerance by comparing the properties of monomeric and dimeric forms of Hydrogenase-1. The results reveal a further interesting advantage that quaternary structure affords to proteins

Efficacy and safety of immune checkpoint inhibitor rechallenge in individuals with hepatocellular carcinoma

BACKGROUND & AIMS: We investigated the efficacy and safety of immune checkpoint inhibitor (ICI) rechallenge in patients with hepatocellular carcinoma (HCC) who received ICI-based therapies in a previous systemic line. METHODS: In this international, retrospective multicenter study, patients with HCC who received at least two lines of ICI-based therapies (ICI-1, ICI-2) at 14 institutions were eligible. The main outcomes included best overall response and treatment-related adverse events. RESULTS: Of 994 ICI-treated patients screened, a total of 58 patients (male, n = 41; 71%) with a mean age of 65.0±9.0 years were included. Median systemic treatment lines of ICI-1 and ICI-2 were 1 (range, 1-4) and 3 (range, 2-9), respectively. ICI-based therapies used at ICI-1 and ICI-2 included ICI alone (ICI-1, n = 26, 45%; ICI-2, n = 4, 7%), dual ICI regimens (n = 1, 2%; n = 12, 21%), or ICI combined with targeted therapies/anti-VEGF (n = 31, 53%; n = 42, 72%). Most patients discontinued ICI-1 due to progression (n = 52, 90%). Objective response rate was 22% at ICI-1 and 26% at ICI-2. Responses at ICI-2 were also seen in patients who had progressive disease as best overall response at ICI-1 (n = 11/21; 52%). Median time-to-progression at ICI-1 and ICI-2 was 5.4 (95% CI 3.0-7.7) months and 5.2 (95% CI 3.3-7.0) months, respectively. Treatment-related adverse events of grade 3-4 at ICI-1 and ICI-2 were observed in 9 (16%) and 10 (17%) patients, respectively. CONCLUSIONS: ICI rechallenge was safe and resulted in a treatment benefit in a meaningful proportion of patients with HCC. These data provide a rationale for investigating ICI-based regimens in patients who progressed on first-line immunotherapy in prospective trials. IMPACT AND IMPLICATIONS: Therapeutic sequencing after first-line immune checkpoint inhibitor (ICI)-based therapy for advanced hepatocellular carcinoma (HCC) remains a challenge as no available second-line treatment options have been studied in immunotherapy-pretreated patients. Particularly, the role of ICI rechallenge in patients with HCC is unclear, as data from prospective trials are lacking. We investigated the efficacy and safety of ICI-based regimens in patients with HCC pretreated with immunotherapy in a retrospective, international, multicenter study. Our data provide the rationale for prospective trials investigating the role of ICI-based regimens in patients who have progressed on first-line immunotherapy

Selective Sirt2 inhibition by ligand-induced rearrangement of the active site

Sirtuins are a highly conserved class of NAD+-dependent lysine deacylases. The human isotype Sirt2 has been implicated in the pathogenesis of cancer, inflammation and neurodegeneration, which makes the modulation of Sirt2 activity a promising strategy for pharmaceutical intervention. A rational basis for the development of optimized Sirt2 inhibitors is lacking so far. Here we present high-resolution structures of human Sirt2 in complex with highly selective drug-like inhibitors that show a unique inhibitory mechanism. Potency and the unprecedented Sirt2 selectivity are based on a ligand-induced structural rearrangement of the active site unveiling a yet-unexploited binding pocket. Application of the most potent Sirtuin-rearranging ligand, termed SirReal2, leads to tubulin hyperacetylation in HeLa cells and induces destabilization of the checkpoint protein BubR1, consistent with Sirt2 inhibition in vivo. Our structural insights into this unique mechanism of selective sirtuin inhibition provide the basis for further inhibitor development and selective tools for sirtuin biology

Molecular characterization of hepatocellular carcinoma in patients with nonalcoholic steatohepatitis

Background and aims: Non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma (HCC) is increasing globally, but its molecular features are not well defined. We aimed to identify unique molecular traits characterising NASH-HCC compared to other HCC aetiologies. Methods: We collected 80 NASH-HCC and 125 NASH samples from 5 institutions. Expression array (n = 53 NASH-HCC; n = 74 NASH) and whole exome sequencing (n = 52 NASH-HCC) data were compared to HCCs of other aetiologies (n = 184). Three NASH-HCC mouse models were analysed by RNA-seq/expression-array (n = 20). Activin A receptor type 2A (ACVR2A) was silenced in HCC cells and proliferation assessed by colorimetric and colony formation assays. Results: Mutational profiling of NASH-HCC tumours revealed TERT promoter (56%), CTNNB1 (28%), TP53 (18%) and ACVR2A (10%) as the most frequently mutated genes. ACVR2A mutation rates were higher in NASH-HCC than in other HCC aetiologies (10% vs. 3%, p <0.05). In vitro, ACVR2A silencing prompted a significant increase in cell proliferation in HCC cells. We identified a novel mutational signature (MutSig-NASH-HCC) significantly associated with NASH-HCC (16% vs. 2% in viral/alcohol-HCC, p = 0.03). Tumour mutational burden was higher in non-cirrhotic than in cirrhotic NASH-HCCs (1.45 vs. 0.94 mutations/megabase; p <0.0017). Compared to other aetiologies of HCC, NASH-HCCs were enriched in bile and fatty acid signalling, oxidative stress and inflammation, and presented a higher fraction of Wnt/TGF-β proliferation subclass tumours (42% vs. 26%, p = 0.01) and a lower prevalence of the CTNNB1 subclass. Compared to other aetiologies, NASH-HCC showed a significantly higher prevalence of an immunosuppressive cancer field. In 3 murine models of NASH-HCC, key features of human NASH-HCC were preserved. Conclusions: NASH-HCCs display unique molecular features including higher rates of ACVR2A mutations and the presence of a newly identified mutational signature. Lay summary: The prevalence of hepatocellular carcinoma (HCC) associated with non-alcoholic steatohepatitis (NASH) is increasing globally, but its molecular traits are not well characterised. In this study, we uncovered higher rates of ACVR2A mutations (10%) - a potential tumour suppressor - and the presence of a novel mutational signature that characterises NASH-related HCC

Efficacy and safety of immune checkpoint inhibitor rechallenge in individuals with hepatocellular carcinoma

BACKGROUND & AIMS: We investigated the efficacy and safety of immune checkpoint inhibitor (ICI) rechallenge in patients with hepatocellular carcinoma (HCC) who received ICI-based therapies in a previous systemic line. METHODS: In this international, retrospective multicenter study, patients with HCC who received at least two lines of ICI-based therapies (ICI-1, ICI-2) at 14 institutions were eligible. The main outcomes included best overall response and treatment-related adverse events. RESULTS: Of 994 ICI-treated patients screened, a total of 58 patients (male, n = 41; 71%) with a mean age of 65.0±9.0 years were included. Median systemic treatment lines of ICI-1 and ICI-2 were 1 (range, 1-4) and 3 (range, 2-9), respectively. ICI-based therapies used at ICI-1 and ICI-2 included ICI alone (ICI-1, n = 26, 45%; ICI-2, n = 4, 7%), dual ICI regimens (n = 1, 2%; n = 12, 21%), or ICI combined with targeted therapies/anti-VEGF (n = 31, 53%; n = 42, 72%). Most patients discontinued ICI-1 due to progression (n = 52, 90%). Objective response rate was 22% at ICI-1 and 26% at ICI-2. Responses at ICI-2 were also seen in patients who had progressive disease as best overall response at ICI-1 (n = 11/21; 52%). Median time-to-progression at ICI-1 and ICI-2 was 5.4 (95% CI 3.0-7.7) months and 5.2 (95% CI 3.3-7.0) months, respectively. Treatment-related adverse events of grade 3-4 at ICI-1 and ICI-2 were observed in 9 (16%) and 10 (17%) patients, respectively. CONCLUSIONS: ICI rechallenge was safe and resulted in a treatment benefit in a meaningful proportion of patients with HCC. These data provide a rationale for investigating ICI-based regimens in patients who progressed on first-line immunotherapy in prospective trials. IMPACT AND IMPLICATIONS: Therapeutic sequencing after first-line immune checkpoint inhibitor (ICI)-based therapy for advanced hepatocellular carcinoma (HCC) remains a challenge as no available second-line treatment options have been studied in immunotherapy-pretreated patients. Particularly, the role of ICI rechallenge in patients with HCC is unclear, as data from prospective trials are lacking. We investigated the efficacy and safety of ICI-based regimens in patients with HCC pretreated with immunotherapy in a retrospective, international, multicenter study. Our data provide the rationale for prospective trials investigating the role of ICI-based regimens in patients who have progressed on first-line immunotherapy

Transcriptom and miRNA data of PUFA-enriched stimulated murine macrophage and human endothelial cell lines

Abstract Inflammation is associated with the adaptation of macrophages and endothelial cells, and the dysregulation of these differentiation processes has been directly linked to both acute and chronic disease states. As cells in constant contact with blood, macrophages and endothelial cells are also under the direct influence of immunomodulatory dietary components such as polyunsaturated fatty acids (PUFA). RNA sequencing analyses allow us to understand the global changes in gene expression occurring during cell differentiation, including both transcriptional (transcriptome) and post-transcriptional (miRNAs) levels. We generated a comprehensive RNA sequencing dataset of parallel transcriptome and miRNA profiles of PUFA-enriched and pro-inflammatory stimulated macrophages and endothelial cells aiming to uncover the underlying molecular mechanisms. PUFA concentrations and duration of supplementation were based on dietary ranges, allowing for metabolism and plasma membrane uptake of fatty acids. The dataset may serve as a resource to study transcriptional and post-transcriptional changes associated with macrophage polarisation and endothelial dysfunction in inflammatory settings and their modulation by omega-3 and omega-6 fatty acids