Therapeutic strategies using drugs which cause Lysosomal Cell Death have been proposed for eradication of resistant cancer cells. In this context, nanotherapy based on Magnetic Intra-Lysosomal Hyperthermia (MILH) generated by magnetic nanoparticles (MNPs) that are grafted with ligands of receptors overexpressed in tumors appears to be a very promising therapeutic option. However, mechanisms whereby MILH induces cell death are still elusive. Herein, using Gastrin-grafted MNPs specifically delivered to lysosomes of tumor cells from different cancers, we provide evidences that MILH causes cell death through a non-apoptotic signaling pathway. The mechanism of cell death involves a local temperature elevation at the nanoparticle periphery which enhances the production of reactive oxygen species through the lysosomal Fenton reaction. Subsequently, MILH induces lipid peroxidation, lysosomal membrane permeabilization and leakage of lysosomal enzymes into the cytosol, including Cathepsin-B which activates Caspase-1 but not apoptotic Caspase-3. These data highlight the clear potential of MILH for the eradication of tumors overexpressing receptors.

This work presents an integrated technology for assessing in vivo anti-cancer treatments in mice, based on various heating conditions. Bioluminescence imaging (BLI) was used to assess the physiological response of tumor and tumor microenvironment (TME) to heat treatment induced by magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU). Transgenic tumor cells and mouse models with either constitutive or thermoinduced luciferase expressions were combined to monitor cell viability and heat-induced processes in the tumor and TME. BLI performed after MRgHIFU heating shows that a moderate increase in temperature (45°C) over 5 min can be exploited to promote heat-activable treatments in the tumor and its TME, without inducing direct cell death. A higher temperature rise over a shorter exposure time can induce cell death in the tumor, as revealed by a reduction in the BLI signal after treatment. Under these conditions, BLI also revealed that the TME can be stimulated by heat without inducing necrosis. These integrated technologies and models are useful to assess, in vivo in mice, the efficacy of various anticancer strategies exploiting local heat deposition by noninvasive MRgHIFU, including those combining tumor ablation with local drug administration using thermosensitive nanovehicles.