Description du sujet de thèse

The PhD position is a collaborative project between the laboratories of Christophe Lamaze (Institut Curie, Paris, France) and Robert Nabi (UBC, Vancouver, Canada). It is funded by the CNRS–UBC Joint PhD Program.

INTRODUCTION

Caveolae: Emerging Players in Mechanobiology:
Caveolae are 80-100 nm plasma membrane (PM) invaginations composed of oligomerized caveolin-1 (Cav1) scaffolds, stabilized by cytosolic cavins and anchored at the PM by the ATPase EHD2. Traditionally viewed as endocytic structures, the Lamaze lab has demonstrated that caveolae rapidly flatten and disassemble under mechanical stress, serving as a PM reservoir to prevent rupture. This has been a game-changer in the understanding of caveolae functions. While Cav1 has long been thought to regulate signaling within caveolae, the Nabi lab challenged this dogma by revealing that signaling regulation relies on noncaveolar Cav1 scaffolds and established AI-based software (SuperResNET) to detect scaffolds from dSTORM super-resolution microscopy. Recently, Lamaze and Nabi showed that mechanical disassembly of caveolae releases highly diffusive Cav1 scaffolds across the PM, regulating intracellular signaling through a novel paradigm we term “remote mechanosignaling”.

Tumor Invasion and Cancer-Associated Fibroblasts (CAFs):
Tumor progression depends on the intrinsic properties of tumor cells and is strongly supported by the tumor microenvironment (TME), where cancer-associated fibroblasts (CAF) are key players. Within the TME, both tumor cells and CAFs are continuously exposed to dynamic mechanical forces. Cav1 expression in both tumor cells and CAFs impacts cancer prognosis however implications of its new mechanical role are not clearly understood and remain unexplored.

RATIONALE AND OBJECTIVES

This collaborative project aims to elucidate the role of caveolae mechanics in tumorigenesis, by leveraging the complementary expertise of the Lamaze and Nabi labs. It consists of two integrated research projects: (1) Lamaze will investigate the role of CAF-caveolae mechanosignaling in tumor invasion; and (2) Nabi will study Cav1 mechano-trafficking in tumor cells and CAFs.

LAMAZE PROJECT: Caveolae Mechanics in CAFs and Tumorigenesis

We focus on colorectal cancer (CRC) due to its highly mechanodynamic microenvironment and the abundance of mechano-sensitive caveolae in CRC-associated CAFs (our preliminary data).

AXE 1: Impact of CAF-Caveolae Mechanics on Tumor Invasion.
We will use 3D tumor models that mimic tumor architecture and allow controlled mechanical forces application (stretchable chips). First model: CRC CT26 spheroids will be co-embedded with murine CAFs in a collagen I matrix. Second model: CRC-on-chip with co-cultured murine CRC organoids and CAFs replicating crypt architecture and peristalsis. The invasion index will be quantified via 3D microscopy (biphoton, lightsheet). To dissect the roles of caveolae vs. scaffolds in tumor invasion, CAFs will be depleted for Cav1 (eliminating both) or cavin-1 (preserving scaffolds).

AXE 2: Caveolae Mechanics in CAF Intracellular Signaling.
We will assess the role of Cav1 scaffolds in remote mechanosignaling, focusing on educated guess pathways (IL6/STAT3, YAP/TAZ, PI3K, TGF-β, ERK…), while transcriptomics/kinome analysis will reveal other relevant pathways. Using CAF monoculture (+/- Cav1 or cavin-1) on stretchable collagen I substrates, we will perform functional assays (contractility, matrix topography) and analyze signaling effectors (IF/WB). dSTORM microscopy, combined with Nabi's SuperResNET and SiMiLe-M software (multiple instance learning), will distinguish caveolae from scaffolds in pathway regulation. Additionally, we will investigate Cav1 mechanical endocytosis in these regulations using the biotin sensor from the Nabi lab.

AXE 3: Effects of CAF-Caveolae Mechanics on Tumor Cells.
Using models from Axe 1, we will assess CAF-caveolae mechanics' impact on CAF-dependent tumor cell signaling (Axe 2) and use transcriptomics/kinome analysis to identify additional targets. Tumor cell proliferation (Ki67), survival (TUNEL, caspase-3), and metabolism will also be examined.

Contexte de travail

The PhD student will be supervised by Christophe Lamaze. He will be enrolled in the Life Sciences Doctoral School in University Paris Sciences et Lettres (PSL). In addition to a collaboration with R. Nabi, this project is carried out in collaboration with the teams of D. Vignjevic (tumor microenvironment specialist, Institut Curie, UMR144) and S. Descroix (microfluidics specialist, Institut Curie, UMR168). Student exchanges between the Lamaze and Nabi labs are planned to foster joint work on their respective research projects.

The team is composed of 10 members working on various aspects of caveolae. Several grants have been secured by the PI to ensure funding for the coming years (CNRS, Institut Curie institutional funding, INCa, Fondation de France, Ligue contre le Cancer), and several lab members (postdocs and technicians) are funded to collaborate on this topic as well.

The project will be conducted at Institut Curie, a world-renowned cancer research center with a broad range of expertise in cell biology, soft matter physics, and chemical biology. It is composed of multidisciplinary teams (biologists, chemists, physicists, computer scientists). Institut Curie is equipped with state-of-the-art technologies, including the Nikon Imaging Centre (one of the few in Europe), which provides advanced microscopes and robust image analysis tools. The research center has close interactions with clinicians at Curie Hospital, one of Europe's leading institutions for cancer treatment, and they regularly collaborate with academic teams. All of this provides an ideal environment for the PhD student.

Contraintes et risques

Biological risks (cell culture), chemical risks (CMR)