Cys mutants as tools to study the oligomerization of the pore-forming toxin sticholysin I.

Sticholysin I (StI) is a water-soluble protein with the ability to bind membranes where it oligomerizes and forms pores leading to cell death. Understanding the assembly property of this protein may be valuable for designing potential biotechnological tools, such as stable or structurally defined nanopores. In order to get insights into the stabilization of StI oligomers by disulfide bonds, we designed and characterized single and double cysteine mutants at the oligomerization interface. The oligomer formation was induced in the presence of lipid membranes and visualized by SDS-PAGE. The contribution of the oligomeric structures to the membrane binding and pore-forming capacities of StI was assessed. Single and double cysteine introduction at the protein-protein oligomerization interface does not considerably affect the conformation and function of the monomeric protein. In the presence of membranes, a cysteine double mutation at positions 15 and 59 favored formation of different size oligomers stabilized by disulfide bonds. The results of this work highlight the relevance of these positions (15 and 59) to be considered for developing biosensors based on nanopores from StI.

Acceptance of SARS-CoV-2 vaccination among cancer patients in Portugal: attitudes and associated factors.

OBJECTIVE: COVID-19 vaccines have shown efficacy and safety in healthy people. However, cancer patients under active immunosuppressive treatment were not included in the clinical trials conducted to test vaccines' efficacy and safety. This study aimed to evaluate the COVID-19 vaccine acceptance in cancer patients undergoing immunosuppressive therapy. METHODS: A total of 200 adult cancer patients received a questionnaire between March 8 and April 2, 2021, before the beginning of cancer patients' vaccination in Portugal. The questionnaire adapted from previously conducted studies included 11 close-ended items, evaluating variables such as patient sociodemographic and clinical characteristics, and the acceptance and underlying reasons to be or not to be vaccinated. The primary outcome was the intended acceptance of the COVID-19 vaccine in cancer patients. Multiple logistic regression was performed to identify factors associated with intended acceptance. RESULTS: Among the 200 delivered questionnaires, only 169 were included in this study. From those, 142 (84%) patients intended to be vaccinated against COVID-19. Only 27 participants (16%) had not yet decided or were reluctant to COVID-19 vaccination. High school degree (odds ratio (OR) 0.133, 95% confidence interval (C.I.) 0.031-0.579, p = 0.007], rural residence (OR 0.282, 95% C.I. 0.081-0.984, p = 0.047), and reluctance in believing in the vaccine efficacy (OR 0.058, 95% C.I. 0.016-0.204, p < 0.001] were identified predictors factor for COVID-19 vaccine hesitancy. CONCLUSION: Most patients intended to be vaccinated against COVID-19, and specific factors such as education level, rural residence and the belief in vaccine efficacy were related to vaccine acceptance.

Epithelioid Trophoblastic Tumour Presenting with Scalp Lesions.

Epithelioid trophoblastic tumour (ETT) is a very rare variant of gestational trophoblastic disease, which arises in reproductive-age women with a prior gestational history. Because of its rarity, its biological behaviour, imaging characteristics and therapeutic schedule have not yet been fully established. Here we describe a rare case of metastatic ETT in a premenopausal woman. A 40-year-old, gravida 3, para 2, Portuguese woman was referred to the dermatology department for multiple skin nodules on the scalp measuring between 1 and 6 cm. A skin biopsy was suggestive of metastatic lesions of low differentiated carcinoma in favour of squamous cell carcinoma. Staging cervical-thoracic-abdominal and pelvic CT showed multiple lesions compatible with metastasis (ganglia, lung and kidneys). Since a CT scan was unable to identify the primary tumour, it was decided to perform a PET-CT scan and to take a biopsy of a vulvar nodule which had been clinically identified as ETT. The patient began the EMA-CO protocol and completed two cycles but with clinical worsening and radiological progression. Although several different chemotherapy regimens are used to treat gestational trophoblastic disease, the optimal treatment is not known given the rarity of this disease and the lack of controlled trials. LEARNING POINTS: Trophoblastic disease is a rare entity with several presentations at diagnosis.Presentation with dermatological changes may need differential diagnosis to distinguish it from other types of dermatological disease.Quick diagnosis and referral to an appropriate centre are needed.

Prognostic factors for early relapse in non-metastatic triple negative breast cancer - real world data.

BACKGROUND: Triple negative breast cancer (TNBC) has the worst prognosis amongst all subtypes. Studies have shown that the achievement of pathologic complete response in the breast and axilla correlates with improved survival. The aim of this study was to identify clinical or pathological features of real-life TNBC patients with a higher risk of early relapse. MATERIALS AND METHODS: Single-centre retrospective analysis of 127 women with TNBC, stage II-III, submitted to neoadjuvant treatment and surgery between January 2016 and 2020. Multivariate Cox regression analysis for disease free survival (DFS) at 2 years was performed and statistically significant variables were computed into a prognostic model for early relapse. RESULTS: After 29 months of median follow-up, 105 patients (82.7%) were alive and, in total, 38 patients (29.9%) experienced recurrence. The 2-year DFS was 73% (95% CI: 21.3-22.7). In multivariate analysis, being submitted to neoadjuvant radiotherapy [HR 2.8 (95% CI: 1.2-6.4), p = 0.017] and not achieving pathologic complete response [HR 0.3 (95% CI: 0.1-1.7), p = 0.011] were associated with higher risk of recurrence. In our prognostic model, the presence of at least one of these variables defined a subgroup of patients with a worse 2-year DFS than those without these features (59% vs. 90%, p < 0.001, respectively). CONCLUSIONS: In this real-life non-metastatic TNBC cohort, neoadjuvant radiotherapy (performed due to insufficient clinical response to neoadjuvant chemotherapy or significant toxicity) impacted as an independent prognostic factor for relapse along with the absence of pathologic complete response identifying a subgroup of higher risk patients for early relapse that might merit a closer follow-up.

Acute toxicity and tolerability of anthracycline-based chemotherapy regimens in older versus younger patients with breast cancer: real-world data.

OBJECTIVES: To compare the non-cardiac acute toxicity and tolerability profile of anthracycline-based regimens between older versus younger women diagnosed with breast cancer in a real-world setting. METHODS: Retrospective cohort of female patients diagnosed with breast cancer and treated with neoadjuvant or adjuvant anthracycline-based regimens between 2017 and 2019. Patients were grouped in young versus older, using an age of 65 as cut-off. Differences in non-cardiac acute toxicity and change in treatment plan were examined. RESULTS: Among the 559 patients, 19.5% were aged ≥ 65 years. Regimens used were fluorouracil, epirubicin, and cyclophosphamide in 56.2% of patients, doxorubicin and cyclophosphamide in 33.3%, and epirubicin and cyclophosphamide in 10.5%; there were no differences in incidence of grade 3 or 4 toxicities between regimens (p = 0.184). Acute grade 3 or 4 toxicities occurred more frequently in the older group (33.9% versus 10.7%, p < 0.0001, OR 4.304, 95%-CI [2.619-7.073]). Delay of at least one chemotherapy cycle due to toxicity occurred more frequently in the older group (24.8% versus 9.3%, p < 0.0001, OR 3.199, 95%-CI [1.867-5.481]). Early termination of treatment also occurred more frequently in the older group (11.9% versus 1.6%, p < 0.0001, OR 8.571, 95%-CI [3.331-22.048]). CONCLUSION: Although acute grade 3 or 4 toxicities were more frequent in older patients, which resulted in increased cycle delay and/or premature termination of treatment, overall treatment was still reasonably well-tolerated, with 88.1% of older patients completing the planed anthracycline regimen.

Architecture of the pore forming toxin sticholysin I in membranes.

Sticholysin I (StI) is a toxin produced by the sea anemone Stichodactyla helianthus and belonging to the actinoporins family. Upon binding to sphingomyelin-containing membranes StI forms oligomeric pores, thereby leading to cell death. According to recent controversial experimental evidences, the pore architecture of actinoporins is a debated topic. Here, we investigated the StI topology in membranes by site-directed spin labeling and electron paramagnetic resonance spectroscopy. The results reveal that StI in membrane exhibits an oligomeric architecture with heterogeneous stoichiometry of predominantly eight or nine protomers, according to the available structural models. The StI topology resembles the conic pore structure reported for the actinoporin fragaceatoxin C. Our data show that StI coexists in two membrane-associated conformations, with the N-terminal segment either attached to the protein core or inserted in the membrane forming the pore. This finding suggests a 'pre-pore' to 'pore' transition determined by a conformational change that detaches the N-terminal segment.

Self-homodimerization of an actinoporin by disulfide bridging reveals implications for their structure and pore formation.

The Trp111 to Cys mutant of sticholysin I, an actinoporin from Stichodactyla helianthus sea anemone, forms a homodimer via a disulfide bridge. The purified dimer is 193 times less hemolytic than the monomer. Ultracentrifugation, dynamic light scattering and size-exclusion chromatography demonstrate that monomers and dimers are the only independent oligomeric states encountered. Indeed, circular dichroism and fluorescence spectroscopies showed that Trp/Tyr residues participate in homodimerization and that the dimer is less thermostable than the monomer. A homodimer three-dimensional model was constructed and indicates that Trp147/Tyr137 are at the homodimer interface. Spectroscopy results validated the 3D-model and assigned 85° to the disulfide bridge dihedral angle responsible for dimerization. The homodimer model suggests that alterations in the membrane/carbohydrate-binding sites in one of the monomers, as result of dimerization, could explain the decrease in the homodimer ability to form pores.

Binding of sea anemone pore-forming toxins sticholysins I and II to interfaces--modulation of conformation and activity, and lipid-protein interaction.

Sticholysins I and II (St I and St II) are water-soluble toxins produced by the sea anemone Stichodactyla helianthus. St I and St II bind to biological and model membranes containing sphingomyelin (SM), forming oligomeric pores that lead to leakage of internal contents. Here we describe functional and structural studies of the toxins aiming at the understanding at a molecular level of their mechanism of binding, as well as their effects on membrane permeabilization. St I and St II caused potassium leakage from red blood cells and temperature-dependent hemolysis, the activation energy of the process being lower for the latter toxin. Protein intrinsic fluorescence measurements provided evidence for toxin binding to model membranes composed of 1:1 (mol:mol) egg phosphatidyl choline (ePC):SM. The fluorescence intensity increased and the maximum emission wavelength decreased as a result of binding. The changes were quantitatively different for both toxins. Circular dichroism spectra showed that both St I and St II exhibit a high content of beta-sheet structure and that binding to model membranes did not alter the toxin's conformation to a large extent. Changing the lipid composition by adding 5 mol% of negatively charged phosphatidic acid (PA) or phosphatidyl glycerol (PG) had small, but detectable, effects on protein conformation. The influence of lipid composition on toxin-induced membrane permeabilization was assessed by means of fluorescence measurements of calcein leakage. The effect was larger for ePC:SM bilayers containing 5 mol% of negative curvature-inducing lipids. Electron paramagnetic resonance (EPR) spectra of intercalated fatty acid spin probes carrying the nitroxide moiety at different carbons (5, 7, 12, and 16) evidenced the occurrence of lipid-protein interaction. Upon addition of the toxins, two-component spectra were observed for the probe labeled at C-12. The broader component, corresponding to a population of strongly immobilized spin probes, was ascribed to boundary lipid. The contribution of this component to the total spectrum was larger for St II than for St I. Moreover, it was clearly detectable for the C-12-labeled probe, but it was absent when the label was at C-16, indicating a lack of lipid-protein interaction close to the lipid terminal methyl group. This effect could be either due to the fact that the toxins do not span the whole bilayer thickness or to the formation of a toroidal pore leading to the preferential interaction with acyl chain carbons closer to the phospholipids head groups.