Sigaud, R. | bioRxiv Science

bioRxiv2026

Standard treatment against paediatric BRAF-V600E glioma promotes senescence and sensitizes tumours to BCL-xL inhibition

BackgroundChemo-, radio-, and targeted therapies can induce senescence in tumour cells, a process called therapy-induced senescence (TIS), which can be exploited therapeutically using compounds that kill senescent cells (senolytics). Children with BRAF-V600E activated brain tumours are commonly treated with Dabrafenib, Trametinib or Vinblastine (alone or in combination) with good responses. However, a subset of patients experiences tumour regrowth upon treatment withdrawal. Here, we explore the role of TIS and senolytic therapies in preclinical models of paediatric BRAF-V600E driven brain tumours. MethodsHuman BT-40 tumour cells derived from pleomorphic xanthoastrocytoma are used in vitro or in vivo orthotopically transplanted into mice and treated with either Dabrafenib, Trametinib or Vinblastine. Senescence is assessed by immunostaining and RNA sequencing. Sensitivity to senolytics is determined in vitro in dose response assays and in vivo. ResultsTrametinib treatment induces a senescent phenotype in BT-40 cells in vivo with activation of a senescence-associated secretory phenotype (SASP) and expansion of IBA-1 microglia. Senescence is induced in BT-40 cells in vitro when treated not only with Trametinib, but also with Dabrafenib and Vinblastine. In vitro testing identifies Navitoclax as a potent senolytic against BT-40 senescent cells, mostly through inhibition of the anti-apoptotic protein BCL-xL. In BT-40 tumour bearing mice, combination of Trametinib and Navitoclax causes the ablation of senescent BT-40 cells with significant reduction in tumour regrowth after treatment withdrawal and increased mouse survival. ConclusionsThis study shows that Navitoclax enhances the anti-tumour efficacy of Trametinib and limits tumour regrowth following treatment withdrawal. Key PointsO_LITrametinib, Dabrafenib and Vinblastine induce senescence in BT-40 cells in vitro C_LIO_LISenescent BT-40 cells are sensitive to BCL-xL inhibition C_LIO_LICombination of Trametinib and Navitoclax reduces rebound tumour growth in vivo C_LI Importance of the StudyChildren with BRAF-V600E activated glioma are frequently treated with Dabrafenib, Trametinib or Vinblastine with good responses. However, a subset of patients shows tumour regrowth when the treatment is stopped. To prevent this rebound growth, patients must continue treatment with potential aggravation in quality of life and risk of malignant progression. Our research demonstrates that these therapies induce BT-40 tumour cells to enter a non-proliferative state that shows features of cellular senescence. We identify that senescent tumour cells can be killed using Navitoclax, and potent inhibitor of the anti-apoptotic protein BCL-xL and a well-studied senolytic. We demonstrate that the combination of Trametinib and Navitoclax reduces tumour regrowth after treatment withdrawal. Our research provides a strong rationale supporting the combined use of senolytics with current conventional and targeted therapies against BRAF-V600E mutated brain tumours.

cancer biology↗

bioRxiv2018

Elucidating the roles of Alzheimer disease-associated proteases and the signal-peptide peptidase-like 3 (SPPL3) in the shedding of glycosyltransferases

The Golgi resident glycosyltransferases (GTs) are membrane-bound glycoproteins but are frequently found as soluble proteins in biological fluids where their function remains largely unknown. Previous studies have established that the release of these proteins involved Alzheimer disease-associated proteases such as {beta}-secretases (BACE1 and BACE2) and the intramembrane-cleaving aspartyl proteases Presenilins 1 and 2. Recent studies have involved another intramembrane-cleaving enzyme, the signal peptide peptidese-like-3 (SPPL3). Except for the latter, the two former studies mostly addressed particular cases of GTs, namely ST6Gal-I (BACEs) or GnT-V (Presenilins). Therefore the question still remains as which of these secretases is truly responsible for the cleavage and secretion of GTs. We herein combined the 3 proteases in a single study with respect to their abilities to release 3 families of GTs encompassing three N-acetylglucosaminyltransferases, two fucosyltransferases and two sialyltransferases. Green fluorescent protein (gfp)-fused versions of these GTs were virally transduced in mouse embryonic fibroblasts devoid of BACEs, Presenilins or SPPL3. We found that neither BACE nor Presenilins are involved in the shedding of these glycosyltransferases, while SPPL3 was involved in the cleavage and release of some but not all GTs. Notably, the {gamma}- secretase inhibitor DFK-167 was the only molecule capable of significantly decreasing glycosyltransferase secretion, suggesting the involvement of {gamma}-secretase(s), yet different from Presenilins but comprising SPPL3 among other proteases still to be identified. Using confocal microscopy, we show that SPPL3 selectivity towards GTs relays not only on sequence specificity but also depends on how GTs distribute in the cell with respect SPPL3 during their cycling within and outside the Golgi.

biochemistry↗