Characterization of colon cancer stem cells and their response to treatment with extracts of medical plants

Il cancro del colon-retto è una delle neoplasie più frequenti, ad alto tasso di mortalità, causato dall’interazione di fattori genetici e ambientali. Parallelamente al modello stocastico, secondo il quale tutte le cellule tumorali (CT) hanno una stessa probabilità di rigenerare un tumore, sta prendendo piede il modello che vede solamente in un piccolissimo sottogruppo di cellule staminali tumorali (CST) la capacità di dar luogo e sostenere la crescita tumorale. Dalla letteratura si evince come le CST mostrino deregolazioni a carico di geni implicati in: chemio-resistenza, transizione epitelio-mesenchimale (EMT), auto-rinnovamento incontrollato, processi peculiari delle CST, che favoriscono l’insorgenza di un fenotipo tumorale. Lo scopo del progetto di Dottorato è stato quello di isolare e caratterizzare le CST sia da linee cellulari tumorali che da biopsie di tumore al colon-retto, per identificare marcatori tumorali utili a delineare le fasi di progressione del tumore e di individuare potenziali bersagli terapeutici. Inoltre, ho sottoposto le CT e le CST di una linea di adenocarcinoma del colon-retto (HCA7), a trattamento con l’estratto naturale di T. cordifolia, pianta utilizzata della medicina Ayurvedica, ed uno dei suoi principi attivi, la berberina, allo scopo di verificarne l'efficacia antitumorale. Ho osservato importanti deregolazioni nelle popolazioni cellulari trattate, a carico di diversi geni coinvolti principalmente nella EMT, nella regolazione del ciclo cellulare e della apoptosi e nel favorire un fenotipo chemio-resistente. I livelli di espressione di questi geni sono risultati essere significativamente sotto-espressi, sia nelle CT trattate che nelle CST trattate. I risultati che ho ottenuto depongono a favore di un potenziale ruolo attivo della sostanza naturale sottoposta ad indagine, nel contrastare molti di quei processi fondamentali per lo sviluppo di un fenotipo tumorale. Inoltre, i miei dati avvallano anche l’ipotesi che vede le CST come potenziali bersagli terapeutici, per ottenere un effetto mirato su questa popolazione cellulare tumorale.Colorectal cancer is one of the most frequent cancer, with a high mortality rate, caused by the interaction of genetic and environmental factors. Parallel to the stochastic model, according to which all tumor cells (CT) have the same probability of regenerating a tumor, there is a new model that look in a very small subset of cancer stem cells (CST) the responsible of tumor growth. In the literature, CSTs shows important deregulations on genes implicated in: chemo-resistance, epithelial-mesenchymal transition (EMT), uncontrolled self-renewal, peculiar processes of this small subpopulation, which favor the onset of a tumor phenotype . The aim of my PhD project was to isolate and characterize CSTs both from tumor cell lines and from colorectal cancer biopsies, in order to identify tumor markers useful for delineating the phases of tumor progression and identifying potential therapeutic targets. In addition, I treated the CT and CST of a line of colorectal adenocarcinoma (HCA7) with the natural extract of T. cordifolia, a plant used in Ayurvedic medicine, and one of its active ingredients, berberine, in order to verify its antitumor efficacy. I observed important deregulations in treated cell populations, dependent on several genes involved mainly in EMT, in cell cycle regulation and apoptosis, but also in promoting a chemo-resistant phenotype. The expression levels of these genes were found to be significantly under-expressed, both in the treated CTs and in the treated CSTs. The results I have obtained are in favor of a potential active role of the investigated natural substance, in countering many of those fundamental processes for the development of a tumor phenotype. Furthermore, my data also support the hypothesis that CSTs are potential therapeutic targets for the purpose of achieving a targeted effect on this cell tumor population

Influence of adaptive mesh refinement and the hydro solver on shear-induced mass stripping in a minor-merger scenario

We compare two different codes for simulations of cosmological structure formation to investigate the sensitivity of hydrodynamical instabilities to numerics, in particular, the hydro solver and the application of adaptive mesh refinement (AMR). As a simple test problem, we consider an initially spherical gas cloud in a wind, which is an idealized model for the merger of a subcluster or galaxy with a big cluster. Based on an entropy criterion, we calculate the mass stripping from the subcluster as a function of time. Moreover, the turbulent velocity field is analyzed with a multi-scale filtering technique. We find remarkable differences between the commonly used PPM solver with directional splitting in the Enzo code and an unsplit variant of PPM in the Nyx code, which demonstrates that different codes can converge to systematically different solutions even when using uniform grids. For the test case of an unbound cloud, AMR simulations reproduce uniform-grid results for the mass stripping quite well, although the flow realizations can differ substantially. If the cloud is bound by a static gravitational potential, however, we find strong sensitivity to spurious fluctuations which are induced at the cutoff radius of the potential and amplified by the bow shock. This gives rise to substantial deviations between uniform-grid and AMR runs performed with Enzo, while the mass stripping in Nyx simulations of the subcluster is nearly independent of numerical resolution and AMR. Although many factors related to numerics are involved, our study indicates that unsplit solvers with advanced flux limiters help to reduce grid effects and to keep numerical noise under control, which is important for hydrodynamical instabilities and turbulent flows.Comment: 23 pages, 18 figures, accepted for publication by Astronomy and Computin