👤 Pauline Deshors

Glioblastomas (GBM) are aggressive tumors, which systematically relapse despite standard treatment associating surgery, chemotherapy and radiation therapy. More recently, GBM therapy now includes another therapeutic modality option, Tumor Treating Fields (TTFields) given in combination with Temozolomide (TMZ) following standard treatment. However even with the adjunction of TTFields, GBM remains a lethal disease due to treatment resistance. One of the causes of resistance is the presence of cancer stem cells (GSC) known to be chemo and radioresistant and responsible for tumor regrowth. Studying mechanisms of resistance of GSC to TTFields is thus a major issue to address. Fibroblast Growth Factor Receptors (FGFR) play a major role in numerous processes essential for cancer development, and dysregulation of FGFR signaling has been observed in many cancer types, including GBM. We have previously shown that tyrosine kinase receptor Fibroblast Growth Factor Receptor 1 (FGFR1) controls GBM aggressiveness and GSC radioresistance and that its inhibition leads to radiosensitization through increasing mitotic cell death and microenvironment modulation. Because one of the main mechanisms of action of TTFields is mitotic disturbance and because TTFields act synergistically in vitro with irradiation (IR), we hypothesize that targeting FGFR could sensitize GSC to TTFields. Here we show that, like IR, TTFields significantly decrease GSC growth. Treatment of GSC with pemigatinib (Pem), a FGFR1-3 inhibitor, alters FGFR signalling pathway. We demonstrate that Pem, sensitizes GSC to TTFields by synergistically decreasing their survival and clonogenic ability. Finally, the adjunction of Pem to treatment combining IR and TTFields could sensitize GSC by inducing, in some GSC, a further decrease in the repair of IR-induced DNA damages. Altogether, these results highlight the potential benefits of inhibiting FGFR with the concomitant application of TTFields in the first-line standard GBM treatment to improve patient prognosis. Show less

Glioblastoma (GBM) is a highly lethal type of cancer. GBM recurrence following chemoradiation is typically attributed to the regrowth of invasive and resistant cells. Therefore, there is a pressing need to gain a deeper understanding of the mechanisms underlying GBM resistance to chemoradiation and its ability to infiltrate. Using a combination of transcriptomic, proteomic, and phosphoproteomic analyses, longitudinal imaging, organotypic cultures, functional assays, animal studies, and clinical data analyses, we demonstrate that chemoradiation and brain vasculature induce cell transition to a functional state named VC-Resist (vessel co-opting and resistant cell state). This cell state is midway along the transcriptomic axis between proneural and mesenchymal GBM cells and is closer to the AC/MES1-like state. VC-Resist GBM cells are highly vessel co-opting, allowing significant infiltration into the surrounding brain tissue and homing to the perivascular niche, which in turn induces even more VC-Resist transition. The molecular and functional characteristics of this FGFR1-YAP1-dependent GBM cell state, including resistance to DNA damage, enrichment in the G2M phase, and induction of senescence/stemness pathways, contribute to its enhanced resistance to chemoradiation. These findings demonstrate how vessel co-option, perivascular niche, and GBM cell plasticity jointly drive resistance to therapy during GBM recurrence. Show less