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Digital archive of theses discussed at the University of Pisa


Thesis etd-12202016-085728

Thesis type
Tesi di dottorato di ricerca
Thesis title
Studying stem cells in cancer and in regenerative processes
Academic discipline
Course of study
tutor Prof. Martini, Claudia
relatore Dott.ssa Giacomelli, Chiara
  • Adenosine receptors
  • Cancer stem cell
  • Carnosol
  • Epithelial Mesenchymal Transition
  • Glioblastoma Multiforme
  • Mesenchymal stem cell
  • Stem cell
  • uPAR
Graduation session start date
In my PhD course of studies, I have focused my attention on different aspects of stem cell life/death and differentiation. The stem cells are a particular kind of cell able to proliferate nearly indefinitely and to differentiate giving rise to specialized cells.
The main part of my studies has been oriented towards the investigation of Cancer Stem Cells (CSCs) that are a minor population of cancer cells with stem-like properties and with a high rate of tumourogenity.
Among all cancers, Glioblastoma Multiforme (GBM) aggressiveness and recurrence has been related to the presence of the CSCs in the tumour bulk that confer a high grade of proliferation, chemo- and radio- resistance. For this reason, I have studied CSCs more thoroughly by investigating the mechanism at the basis of their aggressiveness as well as the therapeutic perspective, in order to elucidate new targets and to discover new strategies able to overcome the resistance of those cells.
Firstly, I have investigated uPAR (Urokinase-type Plasminogen Activator Receptor) as a potential target of GBM CSCs. This receptor is often overexpress in GBM and it is already known to have pivotal role in the maintenance of glioma cell viability. Herein the preservation of stem-like features of CSCs and the control of their development has been linked to the expression of uPAR, suggesting that this receptor could protect them from apoptosis. Therefore, uPAR could be definitely taken into consideration as a valuable target to contrast GBM and glioma CSCs.
Considering the key role of Adenosine in the insurgence of different cancers, a further focus of my investigation was the evaluation of Adenosine receptors role in CSCs using their specific ligands. The selective modulation of A1 and A2B adenosine receptor subtypes was demonstrated to promote CSCs differentiation or apoptosis, respectively.
The induction of differentiation approach together with the conventional one used in glioma, such as the administration of alkylating agent Temozolomide (TMZ), has been recently emerged in literature as an innovative strategy to overcome the CSC-mediated resistance. Interestingly, the A1 and A2B activation significantly increases the effects of conventional therapy (TMZ).
Finally, I shift my attention on the discovery of potential new agents to contrast GBM malignancy studying the effects of the natural compound Carnosol, which is the major component of the rosemary extract. The GBM aggressiveness has been also associated to the occurrence of the epithelial-mesenchymal transition (EMT). The effects of the diterpene on the EMT process and on CSCs formation and viability was specifically evaluated. Carnosol exerted an anti-proliferative effect on GBM CSCs interfering with the expression of stemness genes related to the maintenance of CSCs and the induction of an aggressive mesenchymal phenotype. Therefore, diterpene could represent a valuable starting point for the development of effective drug able to prevent and reduce a poor GBM clinical outcome. Moreover, the diterpene could be used to improve the effect of the conventional anti-cancer therapy as a future therapeutic perspective.
In the last part of my studies, I have evaluated the positive aspect of the stem cell coin, focusing on the Bone-Marrow Mesenchymal Stem Cells (BM-MSC). Such pluripotent stem cells have a multi-lineage differentiation potential giving rise to adipocytes, chondrocyte and osteoblasts; furthermore, those cells have been widely used in regenerative medicine.
Bone diseases, fragility and fractures are unfortunately becoming increasingly frequent pathologies in the elderly population. Thus, the discovery of the mechanism that trigger or promote the BM-MSC differentiation could give new insight to develop strategy in favour of bone remodelling.
The effect of the inflammatory environment on the A2B-mediated BM-MSC differentiation in osteoblasts was evaluated. Low dose of inflammatory cytokine was demonstrate to induce the impairment of A2B desensitization process through the degradation of the G-protein coupled receptor kinase 2 (GRK2), thus leading to an increase of bone formation. These results highlight the importance role of cytokine release in the first phase of bone repair. Furthermore, a more thorough understanding of the molecular activation of A2BAR receptor in the presence of inflammatory conditions could help in the development of new therapeutic agents and strategies.
A deeper analysis of the multiple aspects of stem cells, which occur in such widespread diseases, has led to understand both their inherent complexity and huge potentiality.
The stem cells can be considered the tipping point of two opposite events as the cancer onset and the regenerative processes, so better investigate their molecular mechanism may give hope of more long-term survival to many people, in present and future research.