Biology subjects

Armand, F.

Publications and source records attributed to Armand, F..

3 recordsLinked to original sources

bioRxiv2022

Resistance mechanism to Notch inhibition and combination therapy in human T cell acute lymphoblastic leukemia

Gain-of-function mutations in NOTCH1 are among the most frequent genetic alterations in T cell acute lymphoblastic leukemia (T-ALL), making the Notch signaling pathway a promising therapeutic target for personalized medicine. Yet, a major limitation for long-term success of targeted therapy is relapse due to tumor heterogeneity or acquired resistance. Thus, we performed a genome-wide CRISPR-Cas9 screen to identify prospective resistance mechanisms to pharmacological NOTCH inhibitors and novel targeted combination therapies to efficiently combat T-ALL. Mutational loss of Phosphoinositide-3-Kinase regulatory subunit 1 (PIK3R1) causes resistance to Notch inhibition. PIK3R1 deficiency leads to increased PIK3/Akt signaling which regulates the cell cycle and spliceosome machinery, both at the transcriptional and post-translational level. Moreover, several therapeutic combinations have been identified, where simultaneous targeting of the cyclin-dependent kinases 4 and 6 (CDK4/6) and NOTCH proved to be the most efficacious in T-ALL xenotransplantation models. Key pointsO_LIMutational loss of PIK3R1 induces resistance to NOTCH1 inhibition in T-ALL C_LIO_LIPharmacological Notch inhibition synergizes with CDK4/6 inhibitors in T-ALL C_LI

cancer biology↗

bioRxiv2021

Regulation of Src tumor activity by its N-terminal intrinsically disordered region

The membrane anchored Src tyrosine kinase is involved in numerous pathways and its deregulation is involved in human cancer. Our knowledge on Src regulation relies on crystallography, which revealed intramolecular interactions to control active Src conformations. However, Src contains a N-terminal intrinsically disordered unique domain (UD) whose function remains unclear. Using NMR, we reported that UD forms an intramolecular fuzzy complex involving a conserved region with lipid-binding capacity named Unique Lipid Binding Region (ULBR), which could modulate Src membrane anchoring. Here we show that the ULBR is essential for Srcs oncogenic capacity. ULBR inactive mutations inhibited Src transforming activity in NIH3T3 cells and in human colon cancer cells. It also reduced Src-induced tumor development in nude mice. An intact ULBR was required for MAPK signaling without affecting Src kinase activity nor sub-cellular localization. Phospho-proteomic analyses revealed that, while not impacting on the global tyrosine phospho-proteome in colon cancer cells, this region modulates phosphorylation of specific membrane-localized tyrosine kinases needed for Src oncogenic signaling, including EPHA2 and Fyn. Collectively, this study reveals an important role of this intrinsically disordered region in malignant cell transformation and suggests a novel layer of Src regulation by this unique region via membrane substrate phosphorylation.

cancer biology↗

bioRxiv2021

Small Intestinal Resident Eosinophils Maintain Gut Homeostasis Following Microbial Colonisation

Intestinal homeostasis following postnatal microbial colonization requires the coordination of multiple processes including the activation of immune cells, cell-cell communication, the controlled deposition of extracellular matrix, and epithelial cell turnover and differentiation. The intestine harbors the largest frequency of resident eosinophils of all homeostatic organs, yet the functional significance of eosinophil recruitment to this organ has long remained enigmatic. Eosinophils are equipped to both respond to, and modify, their local tissue environment and thus are able to regulate the adaption of tissues to environmental changes. We report a critical role for eosinophils in regulating villous structure, barrier integrity and motility in the small intestine. Notably, the microbiota was identified as a key driver of small intestinal eosinophil activation and function. Collectively our findings demonstrate a critical role for eosinophils in facilitating mutualistic interactions between host and microbiota and provide a rationale for the functional significance of their early life recruitment in the small intestine. HIGHLIGHTSO_LIThe microbiota is a critical regulator of eosinophil activation and turnover C_LIO_LIEosinophils uphold intestinal barrier integrity following microbial colonization C_LIO_LILoss of eosinophils at steady-state results in increased villous blunting and altered intestinal motility C_LI

immunology↗