Constança Coelho

The role of low-molecular-weight protein tyrosine phosphatase (LMW-PTP ACP1) in oncogenesis

Protein tyrosine phosphorylation is a crucial cellular event that is involved in the most important processes of cellular metabolism. Low-molecular-weight protein tyrosine phosphatase (LMW-PTP) is a tyrosine phosphatase that presents two active distinct isoforms and is regulated through cysteine oxidation and tyrosine phosphorylation. This enzyme has been linked to tumorigenesis, but its role is considered controversial: it may be considered oncogenic or anti-oncogenic depending on its interaction with different substrates. Furthermore, recent studies have demonstrated that LMW-PTP is involved in epithelial cell migration, a characteristic of tumor cells. This fact strengthens the importance of this enzyme in the oncogenic process and opens new avenues for future research. The study of LMW-PTP and its pathways may enhance therapeutic strategies that target tyrosine phosphorylation and its substrates. In this review, we try to clarify the importance of this protein in carcinogenesis through the analysis of LMW-PTP interaction with different substrates.

Low molecular weight protein tyrosine phosphatase isoforms regulate breast cancer cells migration through a RhoA dependent mechanism.

Low molecular weight protein tyrosine phosphatase (LMW-PTP) has been associated with cell proliferation control through dephosphorylation and inactivation of growth factor receptors such as PDGF-R and EphA2, and with cellular adhesion and migration through p190RhoGap and RhoA. We aim to clarify the role of two main LMW-PTP isoforms in breast cancer tumorigenesis. We used a siRNA-mediated loss-of-function in MDA-MB-435 breast cancer cell line to study the role of the two main LMW-PTP isoforms, fast and slow, in breast cancer tumorigenesis and migration. Our results show that the siRNAs directed against total LMW-PTP and LMW-PTP slow isoform enhanced cell motility in an invasive breast cancer cell line, MDA-MB-435, with no changes in the proliferation and invasive potential of cells. The total LMW-PTP knockdown caused a more pronounced increase of cell migration. Suppression of total LMW-PTP decreased RhoA activation and suppression of the LMW-PTP slow isoform caused a small but significant increase in RhoA activation. We propose that the increase or decrease in RhoA activation induces changes in stress fibers formation and consequently alter the adhesive and migratory potential of cells. These findings suggest that the two main isoforms of LMW-PTP may act differentially, with the fast isoform having a more prominent role in tumor cell migration. In addition, our results highlight functional specificity among LMW-PTP isoforms, suggesting hitherto unknown roles for these proteins in breast cancer biology. Novel therapeutic approaches targeting LMW-PTP, considering the expression of these two isoforms and not LMW-PTP as a whole, should be investigated.

Polymorphism C242T of the gene of the p22phox subunit for nicotinamide adenine dinucleotide phosphate oxidase, and erythrocytic antioxidant enzymes, in patients with tetralogy of Fallot.

BACKGROUND Nicotinamide adenine dinucleotide phosphate oxidase of the vascular cell membrane is an important source of reactive oxygen species. The aim of our study was to evaluate the possible influence of the p22phox C242T gene polymorphism on blood pressure and some markers of oxidative stress in children with tetralogy of Fallot. METHODS After surgical repair in early life, we recruited 38 children, aged 11.7 plus or minus 3.2 years, including 185 healthy individuals as controls for the purposes of establishing frequencies of alleles and genotypes. From this latter group, we matched a sub-sample of 53 healthy caucasian children, aged 11.0 plus or minus 1.0 years, in order to compare enzymic activities. RESULTS The children with tetralogy of Fallot showed significantly lower values of low-molecular-weight protein tyrosine phosphatase, particularly in carriers of CC genotype for the p22phox gene, with values of 145.2 plus or minus 77.4 micromol/g Hb/h, compared to controls, at 344.4 plus or minus 100.4 micromol/g Hb/h (p less than 0.001). Methemoglobin reductase activity in the patients with tetralogy was also lower in those with the CC genotype, at 9.8 plus or minus 3.2 micromol/g Hb-1 min(-1) compared to 24.2 plus or minus 11.8 micromol/g Hb(-1) min(-1) as measured in the controls (p less than 0.01). Lower systolic (p less than 0.05) and diastolic (p less than 0.01) blood pressures were also observed in the patients with tetralogy of Fallot. CONCLUSIONS Patients with tetralogy of Fallot having the CC genotype may be at a higher state of oxidative stress than T allele carriers, a finding which could have prognostic implications. Long term follow-up of these patients, however, may be necessary in order to draw definite conclusions.

Programming of Essential Hypertension: What Pediatric Cardiologists Need to Know

Hypertension is recognized as one of the major contributing factors to cardiovascular disease, but its etiology remains incompletely understood. Known genetic and environmental influences can only explain a small part of the variability in cardiovascular disease risk. The missing heritability is currently one of the most important challenges in blood pressure and hypertension genetics. Recently, some promising approaches have emerged that move beyond the DNA sequence and focus on identification of blood pressure genes regulated by epigenetic mechanisms such as DNA methylation, histone modification and microRNAs. This review summarizes information on gene–environmental interactions that lead toward the developmental programming of hypertension with specific reference to epigenetics and provides pediatricians and pediatric cardiologists with a more complete understanding of its pathogenesis.

Ranibizumab for the Treatment of Diabetic Macular Oedema in the Real-World Clinical Setting in Portugal: A Multicentre Study

Purpose: The purpose of this study was to evaluate the 2-year outcome of ranibizumab for diabetic macular oedema (DME) in the real-life clinical practice of five ophthalmology departments of the National Health Service (NHS) in Portugal. Methods: This is a retrospective multicentre study. The clinical records on consecutive patients with DME from clinical practice treated with 0.5 mg intravitreal ranibizumab and followed up for 24 months were reviewed. Efficacy outcomes comprised the change in best corrected visual acuity (BCVA) and central macular thickness (CMT) evaluated by SD-OCT. Multivariate regression analysis was performed to explore predictors of BCVA. Results: A total of 122 eyes of 93 patients were included. The median BCVA change by 24 months was +5.0 letters (IQR 12.0) (p < 0.001) and the CMT change was –89.0 µm (IQR 165.0) (p < 0.001). By 24 months, 21.4% of the eyes had gained ≥15 letters and 8.6% had lost ≥15 letters. The median number of injections given during follow-up was 5.0 (IQR 4.0). A greater baseline CMT and a more disrupted status of the external limiting membrane were predictive of worse BCVA at 24 months (p ≤ 0.015). Conclusion: DME treatment with ranibizumab in the Portuguese NHS is associated with anatomic and functional improvement by 2 years; however, our results are below those reported in major clinical trials, and undertreatment is probably the cause.

Prediction of severe exacerbations and mortality in COPD: the role of exacerbation history and inspiratory capacity/total lung capacity ratio

Background Severe exacerbations and mortality are major outcomes in COPD, and risk factors for these events are actively searched for. Several predictors of mortality have been identified in COPD. The inspiratory capacity/total lung capacity (IC/TLC) ratio has been shown to be a strong predictor of all cause and respiratory mortality in patients with COPD. The major objectives of this study were to analyze which clinical parameters, including lung volumes, were the best predictors of the 5-year cumulative risk of hospital admissions or death and the 5-year risk of exacerbations, in stable COPD patients. Methods This study retrospectively reviewed data from 98 stable COPD patients, consecutively recruited in 2012. Forced expiratory volume in 1 s (FEV1), modified Medical Research Council dyspnea scale, exacerbation history (ExH), Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2011 groups, and lung volumes were reviewed. Five years later, this population was evaluated for cumulative exacerbations, hospital admissions, and mortality. All the population, and GOLD group D separately, were analyzed. Results The cumulative 5-year combined risk of hospital admission or death was significantly predicted by the ExH and the IC/TLC ratio. Analyzing separately group D, FEV1 was the only predictor of this outcome. The frequency of exacerbations in the previous year was the best predictor of future cumulative 5-year risk of subsequent exacerbations, both for the total population and the GOLD D group. Conclusion ExH and IC/TLC ratio were the best predictors of the most severe outcomes in COPD (admissions or mortality), independently of COPD severity. FEV1 was the only predictor of the cumulative 5-year combined risk of hospital admission or death in the GOLD D group. ExH was the best predictor of 5-year cumulative future risk of exacerbations. Besides FEV1 and ExH, the IC/TLC ratio can be a useful predictor of severe outcomes in COPD.