VIROLLE – iBV

Glioblastomas (GBM) are the most common form of primary brain tumors in adult. These tumors remain incurable and lead to a fatal outcome in less than 18 months. Tumor development is a complex process mixing normal cells and heterogeneous cancer cell populations. A sublevel of complexity in intra-tumor heterogeneity resides in the co-existence of functionally divergent heterogeneous populations of cells. GBM exemplifies this situation by harboring tumor territories functionally divergent while sharing similar genomic abnormalities. These territories are enriched in mitotic tumor cells, positive for markers of GBM stem cell (GSC), or enriched in non-mitotic, differentiated cells, frequently associated to pathological vessels and large necrotic areas. Such heterogeneity constitutes a major obstacle for conventional therapies, mostly due to the selection and expansion of resistant GSC. Thus targeting GSC properties and mitotic territories will be valuable for therapeutic strategies.

The research developed by our group focuses on the study of the regulation of GSC plasticity in the context of the genesis of tumor micro-territories. Through a better understanding of tumor homeostasis, our goal is to identify key molecular factors of interest for therapeutic purposes. The group is composed of researchers and clinicians, an essential association to link fundamental research with clinical applications. Because GBM are heterogeneous tumors, we have built a platform dedicated to establish and characterize a collection of GSC primary cultures (from different patients) as well as GBM samples representative of mitotic and non-mitotic tumor territories. This collection, crucial for our research, allowed us to identify key molecular factors involved in the control of GSC properties and tumorigenicity.

The objective of our research development is to model the molecular basis involved in the biogenesis and homeostasis of both mitotic and non-mitotic tumor territories, affecting tumor progression and aggressiveness. Our aim is to identify innovative therapeutic targets capable to efficiently repress GSC properties.

We have identified a tumor suppressor miRNA signature (among them the miR-302-367 cluster), constituting a feature and a gatekeeper of non-mitotic territories, while one of its common targets, a splice factor, is restricted to stem-like/progenitor cells in mitotic territories and contributes to the maintenance of stemness and selfrenewal.

We will characterize the regulation of this splice factor and its mode of action in self-renewing GSC by identifying its most functionally prominent targets (deep RNAseq, exome analysis and CLIP-seq). Our recent results indicate the strong contribution of this factor in the regulation of H3K9 and H3K27 methylation, influencing thus the chromatin structure. Using bioinformatic and mathematical modeling, we will determine hubs of regulatory targets involved in GSC maintenance and aggressiveness.

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