Differential transformation capacity of neuro-glial progenitors during development.

Gliomas represent the most common type of brain tumor, but show considerable variability in histologic appearance and clinical outcome. The phenotypic differences between types and grades of gliomas have not been explained solely on the grounds of differing oncogenic stimuli. Several studies have demonstrated that some phenotypic differences may be attributed to regional differences in the neural stem cells from which tumors arise. We hypothesized that temporal differences may also play a role, with tumor phenotypic variability reflecting intrinsic differences in neural stem cells at distinct developmental stages. To determine how the tumorigenic potential of lineally related stem cells changes over time, we used a conditional transgenic system that integrates Cre-Lox-mediated and Tet-regulated expression to drive K-ras(G12D) expression in neuro-glial progenitor populations at different developmental time points. Using this model, we demonstrate that K-ras(G12D)-induced transformation is dependent on the developmental stage at which it is introduced. Diffuse malignant brain tumors develop during early embryogenesis but not when K-ras(G12D) expression is induced during late embryogenesis or early postnatal life. We show that differential expression of cell-cycle regulators during development may be responsible for this differing susceptibility to malignant transformation and that loss of p53 can overcome the transformation resistance seen at later developmental stages. These results highlight the interplay between genetic alterations and the molecular changes that accompany specific developmental stages; early progenitors may lack the regulatory mechanisms present at later, more lineage-restrictive, developmental time points, making them more susceptible to transformation.

In vitro activity of ceftazidime-avibactam against gram-negative bacteria in patients with bacteremia and skin and soft-tissue infections in Colombia 2019-2021.

OBJECTIVES: Ceftazidime-avibactam (CAZ-AVI) is an option for infections caused by MDR gram-negative bacilli. In this study, we aimed to analyze the in vitro antimicrobial activity of CAZ-AVI and other antimicrobial agents against gram-negative bacilli that were collected in Colombia between 2019 and 2021 from patients with bacteremia and skin and soft-tissue infections (SSTIs). METHODS: A total of 600 Enterobacterales and 259 P. aeruginosa strains were analyzed. The phenotypic resistance of isolates, particularly non-susceptibility to meropenem, multidrug-resistant (MDR) isolates, and difficult-to-treat (DTR) P. aeruginosa, was evaluated according to CLSI breakpoints. RESULTS: Enterobacterales had the most susceptibility to CAZ-AVI (96.5 %) and tigecycline (95 %). Tigecycline and CAZ-AVI were the antimicrobial agents with the most in vitro activity against carbapenem-resistant Enterobacterales (CRE). CAZ-AVI was the antimicrobial treatment with the most activity against P. aeruginosa. CONCLUSIONS: Tigecycline and CAZ-AVI were the antimicrobial agents with the most activity against CRE and MDR Enterobacterales. For P. aeruginosa, CAZ-AVI was the antimicrobial treatment with the most in vitro activity.

Loss of p53 cooperates with K-ras activation to induce glioma formation in a region-independent manner.

Gliomas are recognized as a heterogeneous group of neoplasms differing in their location and morphological features. These differences, between and within varying grades of gliomas, have not been explained solely on the grounds of an oncogenic stimulus. Interactions with the tumor microenvironment as well as inherent characteristics of the cell of origin are likely a source of this heterogeneity. There is an ongoing debate over the cell of origin of gliomas, where some suggest a progenitor, while others argue for a stem cell origin. Thus, it is presumed that neurogenic regions of the brain such as the subventricular zone (SVZ) containing large numbers of neural stem and progenitor populations are more susceptible to transformation. Our studies demonstrate that K-ras(G12D) cooperates with the loss of p53 to induce gliomas from both the SVZ and cortical region, suggesting that cells in the SVZ are not uniquely gliomagenic. Using combinations of doxycycline-inducible K-ras(G12D) and p53 loss, we show that tumors induced by the cooperative actions of these genes remain dependent on active K-ras expression, as deinduction of K-ras(G12D) leads to complete tumor regression despite absence of p53. These results suggest that the interplay between specific combinations of genetic alterations and susceptible cell types, rather than the site of origin, are important determinates of gliomagenesis. Additionally, this model supports the view that, although several genetic events may be necessary to confer traits associated with oncogenic transformation, inactivation of a single oncogenic partner can undermine tumor maintenance, leading to regression and disease remission.

Direct effects of leptin on size and extracellular matrix components of human pediatric ventricular myocytes.

OBJECTIVE: There is a well-documented association between obesity and heart failure although the mechanistic basis for this correlation is unclear. Both extracellular matrix remodeling and left ventricular hypertrophy are well-defined components of remodeling in heart failure, and here we further investigate the role of leptin, the obese gene product, on these parameters. METHODS: We used primary human pediatric ventricular cardiomyocytes combined with gelatin zymography, quantitative PCR analysis, proline and leucine incorporation assays, and investigation of kinase activation by Western blotting. RESULTS: We show using gelatin zymography that leptin dose-dependently (0-60 nM) increased proteolytic activity at approximately 72 kDa. Accordingly, upon quantitative PCR analysis we found that leptin increased expression of matrix metalloproteinase-2 (MMP-2). Leptin also caused an increase in collagen type III and IV mRNA expression and a decrease in collagen type I mRNA expression. This was reflected in no significant change in total collagen synthesis, measured by [3H]proline incorporation, in response to leptin. A statistically significant increase in cell size, [3H]leucine incorporation, and expression of well-characterized markers of cardiac hypertrophy, namely cardiac alpha-actin and myosin light chain, were observed in response to leptin. We demonstrate activation of Janus-activated kinase and mitogen-activated protein kinase pathways by leptin, and using pharmacological inhibitors we show that these signaling pathways play a role in mediating the effects of leptin. CONCLUSIONS: Our findings show that leptin regulates cell size, stimulates MMP-2 expression, and alters the profile, but not the total content, of collagen in human cardiomyocytes. This indicates the potential for altered leptin sensitivity to directly regulate cardiac remodeling in obesity.

In situ analysis of mutant EGFRs prevalent in glioblastoma multiforme reveals aberrant dimerization, activation, and differential response to anti-EGFR targeted therapy.

Aberrations in epidermal growth factor receptor (EGFR/ErbB1) are the most common oncogenic alterations in glioblastoma multiforme (GBM), the most common primary brain tumor. Interactions between wild-type (wt) and mutant EGFRs and their subsequent activation are of biologic and potential therapeutic importance in GBMs. We recently showed that in situ proximity ligation assay (PLA) allows for quantitative evaluation of EGFR dimerization and activation in intact cells. Using this in situ platform, we show the aberrant homo-/heterodimeric properties of EGFRvIII and EGFRc958 mutants, the two most common EGFR mutants in GBMs. In addition, dimer phosphoactivation status could be detected by PLA with superior signal-noise ratio (>17-fold) and sensitivity (>16-fold) than immunofluorescence-based phospho-EGFR measurements. Dimer activation analysis indicated quantitative activation differences of mutant dimers. These aberrant features were not overexpression dependent but appeared independent of cellular expression levels, suggesting inherent properties of the mutant receptors. Moreover, we observed in situ detection of EGFRwt-EGFRvIII heterodimerization in GBM specimens, supporting our cell line observations. Notably, currently used anti-EGFR therapeutics, such as cetuximab, matuzumab, and panitumumab, could effectively block EGFRwt dimerization and activation but did not equally impair EGFRvIII homodimers, EGFRwt-EGFRvIII, or EGFRvIII-EGFRc958 heterodimers. EGFRvIII appears to have intrinsic phosphoactivation independent of dimerization as matuzumab blockade of homodimerization had no effect on receptor phosphorylation levels. These data suggest differences in the dimerization-blocking efficacy of EGFR monoclonal antibodies as mutant EGFR dimer configurations prevalent in GBMs can evade blockade by anti-EGFR treatments. Further studies are warranted to evaluate whether this evasion contributes to poor therapeutic response or resistance.

Mouse models to interrogate the implications of the differentiation status in the ontogeny of gliomas.

Glioblastoma multiforme (GBM) is the most common and lethal of human primary central nervous system (CNS) tumors, with a median survival of 14-16 months despite optimal surgery, radiation and chemotherapy. A reason for this dismal prognosis is insufficient understanding of the ontogeny of GBMs, which are highly heterogeneous at a pathological level. This pathological diversity, between and within GBMs as well as varying grades of gliomas, has not been fully explained solely on the grounds of oncogenic stimulus. Interaction with the tumor microenvironment is likely a source of this pathological heterogeneity, as well as the inherent characteristics of the tumor cell of origin. Currently, controversy exists on whether the initial transformed cell is a differentiated astrocyte, progenitor or neural stem cell. Putative cancer stem cells (CSCs), which have features of normal stem cell plus the ability to recapitulate the tumor phenotype in vivo in small numbers, have been identified from a variety of solid human cancers, including GBMs. Evidence suggesting that regions harboring normal stem cells in the adult CNS, such as the subventricular zone and the dentate gyrus, are more prone to viral and chemical oncogenesis, is supportive of the hypothesis that brain tumors arise from stem cells. However, it is still to be determined whether the appearance of brain tumor stem cells (BTSC) is the cause or consequence of tumor initiation and progression. This review discusses emerging evidence highlighting the relevance of the state of differentiation and regional heterogeneity in the ontogeny of GBM. This is an area of high interest in cancer in general, with potential significant therapeutic and prognostic implications.

¿Intervenimos adecuadamente las hernias inguinales? / Do we adequately intervene inguinal hernias?

Introducción. La herniorrafia inguinal es la intervención quirúrgica más frecuente en el ámbito de la cirugía general. El uso de técnicas quirúrgicas con malla ha traído numerosos beneficios, entre los que se pueden mencionar la disminución de la tasa de recidiva y de las complicaciones posoperatorias, y la reducción del tiempo de convalecencia y de reintegración a las actividades cotidianas. Materiales y métodos. Se llevó a cabo un estudio de tipo observacional retrospectivo desde noviembre de 2010 hasta septiembre de 2012 de pacientes diagnosticados con hernia inguinal, que fueron intervenidos quirúrgicamente en una institución de tercer nivel de atención en salud. La recolección de la información se hizo mediante un formato estructurado y la revisión de las historias clínicas. Resultados. De 102 pacientes intervenidos en este lapso de tiempo, 86,3 % eran hombres y 13,7 % mujeres, entre los 14 y 88 años. El 57 % tenía una hernia indirecta unilateral y 28 % presentó una directa unilateral. En 68 % de los pacientes se usó malla y, de estos, a todos se les practicó fijación de la misma. El tipo de malla usada fue mayormente de polipropileno (88 %). El 18,6 % de los pacientes presentó complicaciones posoperatorias. Discusión. La institución estudiada presentó una tasa de utilización de la técnica de Lichtenstein menor a la esperada con relación a otros estudios. La tasa de morbilidad general fue menor, pero el hematoma se presentó el doble de veces que en la mayoría de los reportes de la literatura científica.

Background. Inguinal herniorraphy is the most common surgical procedure performed in general surgery. Using mesh surgical techniques has greatly reduced the relapse rate after the procedure, postoperative complications, recovery time and reintegration to daily activities. Methods. A retrospective observational study of patients diagnosed and surgically treated of inguinal hernia from November 2010 to September 2012 in a third level of care general hospital was performed. The data collection was done through a structured format and review of medical records. Results. In a total of 102 patients, 86.3% were male and 13.7% female, with ages ranging from14 to 88 years old. Most of them had a unilateral indirect hernia (57%) and 28% had a unilateral direct hernia 68 % of the patients were intervened with a mesh technique and all patients received mesh fixation. Most of mesh's type used in the procedures was polypropylene (88%); 18.6 % of patients presented posoperative complications (POP). Discussion. The studied institution showed a lower utilization rate of the Lichtenstein technique than expected according to current literature. The general morbidity rate was lower, but hematoma occurred twice as often than in most literature reports.