Periodic Reporting for period 1 - QuiescStemGBM (Studying the role of Quiescent Cancer Stem Cells in GBM development using a novel in vivo cell cycle-based approach)
Reporting period: 2020-04-01 to 2022-03-31
The project focused on characterising the cell cycle state (proliferating and quiescent) cancer stem cells (CSCs) are present in glioblastoma multiforme (GBM) and their different contribution to tumor formation, progression, and relapse after therapy. Indeed, the main problem of incurability of GBM is due to the recurrence within 6-9 months after first treatment. Furthermore, the invasive feature makes GBM to be completely removed by surgery. In the past, several studies have attempted to demonstrate what is the role of quiescent cancer cells in the progression and relapse of the disease after therapy but their role in cancer invasion remain unclear. Even if believed such cells are indeed responsible for the incurability of GBM, the clear scientific confirmation needed a new method or tool specifically designed to do so. The project aimed to address such biological questions using an innovative method developed ad hoc for studying CSCs from a cell cycle point-of-view. Indeed, in the previous studies, the lack of proper tools to specifically trace or ablate or in general to focus the investigation on quiescent cells might have contributed to the poor knowledge on their contribution in GBM pathogenesis. The knowledge obtained from this project is important for society because, due to the lack of an efficient therapy, it will be used to identify new therapeutical target to fight aggressive brain cancers. The main results showed the presence of quiescent cells where the cancer cells invade brain, and their functional characterization highlighted their importance for the invasion and spreading of cancer. In addition, we developed a new model of brain cancer using cerebral organoids. This will allow scientific community to use also artificial mini brain cancer to investigate several biological questions reducing the need of animals.
The work performed in the project was focused on using newly developed method and tool to study the presence and biological role of different population of cancer cells in-vivo during formation, progression and relapse of Glioblastoma (GBM). I genetically induced tumors over-expressing specific combination oncogene and mutated oncosuppressor in the mouse brain. The co-expression of a quiescent sensor only in specific cancer stem cell population allowed to directly visualise only quiescent cells in the tumor. Quiescent cells were located all over the different tumor areas but their tracing over time after chemotherapy showed no contribution in tumor relapse while their ablation showed to be involved in cancer invasion. Finally, using in vitro models based GBM cell lines and a newly developed organoid-based model of brain cancer, it was possible to test the effective pharmacological targetability of quiescent cells that impacted n cancer invasion. The described results can be exploited in several ways: firstly, the newly conceived tool designed to specifically trace and ablate cells based on their cell cycle state can be used to study other cellular subpopulation and better understating their differential contribution to cancer formation, progression, invasion, and relapse. Secondly, quiescent cells showed to be also pharmacologically targetable impacting on cancer invasion and spread. This last aspect represents a step forward in conceiving new therapeutical agents against invading cancer cells. To disseminate the results of this work I prepared a scientific publication that is currently under revision in a peer reviewed scientific journal. This publication describes the identification of a population of quiescent cancer cells involved in the invasion of cancer within the brain and includes references to the EU funding. Furthermore, the knowledge gained in in vivo and organoid models of GBM, gave me the possibility to prepare a review manuscript entitled “Modeling Brain Tumors: A Perspective Overview of in vivo and Organoid Models” that has been accepted for publication in the journal Frontiers in Molecular Neuroscience which includes references to the EU funding.
The work performed led to great progress beyond the state of art in fact it led to the discovery of a crucial role of quiescent stem cells in the invasion of high-grade glioma/GBM. Indeed, despite several studies have proposed quiescent stem cells as the origin of relapse, their involvement in the invasion of cancer in the brain remains unclear. The results of this project showed the functionality of newly developed tool to specifically trace and ablate cells based on their cell cycle state. This was the key to demonstrate the existence of population of quiescent cells involved in the cancer invasion. Furthermore, this was demonstrated using in vivo as well as newly created in vitro human organoid-based model system of brain cancer. The discovery of a cancer population involved in the invasion together with the creation of new tools and model system to study such process open a new avenue in the study of a strategy to block cancer invasion. Since a diagnosis of GBM is considered a sentence to death, the development of new therapeutical strategies will have a positive impact of patient outcome and survival. Therefore, these results represent an important contribution to the state of the art, and it can be of interest of pharmaceutical companies for the research and development of new therapies for blocking cancer progression. Finally, the system developed to specifically study the lineage of interest based on its cell cycle state can be used for example to study the role of quiescent cells in other type of cancers (i.e. leukaemia) or even normal tissues (i.e. muscle).