Deciphering Differentiation Trajectories in Neuroblastoma and Glioblastoma: Insights from Single-Cell and Spatial Transcriptomics

This thesis explores two highly aggressive tumors: neuroblastoma and glioblastoma. The first project focuses on neuroblastoma, a common extracranial pediatric tumor that typically arises in the adrenal gland during the development of the peripheral sympathetic nervous system. Through a meta-analysis that integrates different single-cell RNA sequencing datasets, I compared tumor cells with normal adrenal medulla cells to identify the differentiation stage that promotes the tumorigenic process. I found that neuroblastoma cells tend to recapitulate the regular differentiation program of the adrenal medulla and most of them exhibit features that resemble the characteristics of sympathoblasts and cycling sympathoblasts, but they do not complete their differentiation in sympathetic neurons. I then investigated which genes, chromosomal aberrations, and pathways block this terminal differentiation. In the second project, I focused on glioblastoma, a highly aggressive primary brain tumor that affects adults. Through spatial transcriptomics, I analysed 12 tumor samples taken from three patients, each from four distinct areas, to verify if glioblastoma shows different characteristics depending on the sampling region. I observed that, unlike other regions, the outermost margin of the tumor has tumor cells resembling the OPC-like subtype. In contrast, the more aggressive MES-like and AC-like phenotypes are mostly represented in the central area and inner margins of the tumor. A more in-depth analysis of the interaction between tumor cells and tumor microenvironment cells has revealed that OPC-like tumor cells release immunosuppressive molecules, promoting growth and immune evasion. These results highlight the spatial complexity of glioblastoma and suggest possible therapeutic targets for this heterogeneous disease.