Delloye-Bourgeois, C. | bioRxiv Science

bioRxiv2021

Modeling breast cancer by grafting patient tumor samples in the avian embryo: an in vivo platform for therapy evaluation coupled to large scale molecular analyses

Lack of preclinical patient-derived xenograft (PDX) cancer models in which to conduct large scale molecular studies seriously impairs the development of effective personalized therapies. We report here on an in vivo concept consisting of implanting human tumor cells in targeted tissues of an avian embryo, delivering therapeutics, evaluating their efficacy by measuring tumors using light sheet confocal microscopy, and conducting large scale RNAseq analysis to characterize therapeutic-induced changes in gene expression. The model was established to recapitulate triple negative breast cancer (TNBC) and validated using TNBC standards of care (SOCs) and an investigational therapeutic agent.

cancer biology↗

bioRxiv2020

Iterative inhibition of commissural growth cone exploration, not post-crossing barrier, ensures forward midline navigation through SlitC-PlxnA1 signaling

Sensitization to Slits and Semaphorin (Sema)3B floor plate repellents after midline crossing is thought to be the mechanism expelling commissural axons contralaterally and preventing their back-turning. We studied the role of Slit-C terminal fragment sharing with Sema3B the Plexin (Plxn) A1 receptor, newly implicated in midline guidance. We generated a knock-in mouse strain baring PlxnA1Y1815F mutation altering SlitC but not Sema3B responses and observed recrossing phenotypes. Using fluorescent reporters, we found that Slits and Sema3B form clusters decorating an unexpectedly complex mesh of ramified FP glia basal processes spanning the entire navigation path. Time-lapse analyzes revealed that impaired SlitC sensitivity destabilized axon trajectories by inducing high levels of growth cone exploration from the floor plate entry, increasing risk of aberrant decisions. Thus, FP crossing is unlikely driven by post-crossing sensitization to SlitC. Rather, SlitC limits growth cone plasticity and exploration through reiterated contacts, continuously imposing a straight and forward-directed trajectory.

developmental biology↗