Tumor microenvironment is a rich ecosystem that goes beyond immune cells also involving its vasculature and extracellular matrix (ECM). Excessive accumulation and aberrant architecture of ECM is a hallmark of cancer progression. A rigid stroma is correlated with an adverse prognosis in several human carcinomas. Increasing evidences also suggest a tight relationship between ECM remodelling and stiffening, cellular mechanosignaling, tissue inflammation and tumor aggression. The tumor microenvironment also mediates the response of solid tumors to chemo- and nanoparticle- therapy. Aberrantly abundant and dense ECM, high interstitial pressure, chaotic vessel organisation, enhanced solid stress are physical features that dramatically restrict the transport of cytotoxic therapeutic agents. Such physical barriers directly contribute to decreased therapeutic efficacy and the emergence of drug resistance by creating drug-free sanctuaries.
Our hypothesis is that physical strategies using nanoparticles that can be activated on demand at a distance through external electromagnetic fields offer attractive solution to modulate the tumor microenvironment, and eventually more localised control of heating in tumor environment. Among photoactivable nanostructures, both plasmonic metallic nanoantennae (mostly gold particles) and carbon-based adsorbing nanomaterials (e.g. carbon nanotubes (CNTs) or graphene oxide) have shown great promises for tumor treatment via localised heating when exposed to near-infrared light (NIR). However, the multifaceted effects of nanoparticle-mediated local hyperthermia on the tumor microenvironment remains elusive. Recent studies have mainly focused on the vascular barrier showing that local heating by nanoparticles could be exploited to increase the vascular permeability and enhance the accumulation of molecular and nano-sized (10-200 nm) agents into the tumor parenchyma. Shifting the focus to the interstitial barriers, the team of Florence Gazeau (primary PhD supervisor) recently demonstrated that mild hyperthermia generated by magnetic nanocubes under an alternating magnetic field had a local effect on the organisation of collagen fibres that improved nanoparticle penetration in the tumor after repeated treatment and potentiate the delivery and efficacy of doxorubicin. Gold nanorods or carbon nanotubes heated to ablative temperature (>50°C) also induced significant collagen remodelling29. Preliminary results also evidence that photo-thermal therapy mediated by carbon nanotubes induces a macroscopic normalisation of the ECM stiffness while inducing spatially and temporally controlled damages to ECM collagen fibres30. Hence the ECM could be an important target of nanohyperthermia with still-underestimated effects on drug transport, normalisation of tumor stiffness and improvement of immune reaction. Insight into how nanomaterial-mediated heating induces remodelling of ECM and further influences anti-tumor immune response would guide the development of novel oncologic approaches that use thermal energy generated at the nanoscale as adjuvant treatment.
Extracellular vesicles (EVs) have been identified as new actors in the tumor-microenvironment interplay modulating immune cells, altering the vasculature and remodeling the ECM. The present project proposes to take advantage of EV-mediated crosstalk between tumor and stroma to deliver an immunostimulating signaling combined to a physical approach to normalize tumor mechanics. The idea is to merge the intrinsic immunomodulatory properties of EVs derived from dendritic cells with extrinsic theranostic features in order to trigger T cell-induced tumor regression. To this end, EVs will be loaded with nanoparticles displaying heating/imaging properties to alter the dense ECM network of growing tumors. In some conditions, the EV membrane will be also engineered to display immune checkpoint inhibitors (anti-PD-1), the overall goal of this protocol being to simultaneously enhance T cell infiltration and activation into tumors promoting the destruction of cancer cells. A combination of methods including real-time imaging on fresh tumor fragments as well as cellular and murine tumor models will be used to get insight into important issues conditioning therapeutic efficiency. Particularly, we will assess the immunomodulatory properties of EVs by quantifying the distribution, the migratory behaviour and the activation status of T lymphocytes in the tumor environment. We will correlate the tumor distribution of heating EVs, the thermally-induced structural damages of ECM at a microscopic level and the modulation of mechanical properties and microvasculature at the tissue level. Finally, we will investigate T cell infiltration after thermal damages and correlate migratory pathway of T-cells with local modification of ECM architecture. This interdisciplinary project is expected to provide new insight into the mechanical cues affecting T cell surveillance in tumors and propose a novel strategy to normalise ECM and promote immune response by means of engineered EVs.