Over the last few decades, nanoparticles have been studied in theranostic field with the objective of exhibiting a long circulation time through the body coupled to major accumulation in tumor tissues, rapid elimination, therapeutic potential and contrast properties. In this context, we developed sub-5 nm gadolinium-based nanoparticles that possess in vitro efficient radiosensitizing effects at moderate concentration when incubated with head and neck squamous cell carcinoma cells (SQ20B). Two main cellular internalization mechanisms were evidenced and quantified: passive diffusion and macropinocytosis. Whereas the amount of particles internalized by passive diffusion is not sufficient to induce in vitro a significant radiosensitizing effect, the cellular uptake by macropinocytosis leads to a successful radiotherapy in a limited range of particles incubation concentration. Macropinocytosis processes in two steps: formation of agglomerates at vicinity of the cell followed by their collect via the lamellipodia (i.e. the "arms") of the cell. The first step is strongly dependent on the physicochemical characteristics of the particles, especially their zeta potential that determines the size of the agglomerates and their distance from the cell. These results should permit to control the quantity of particles internalized in the cell cytoplasm, promising ambitious opportunities towards a particle-assisted radiotherapy using lower radiation doses.

Since radiotherapy is widely used in cancer treatment, it is essential to develop strategies which lower the irradiation burden while increasing efficacy and become efficient even in radio resistant tumors. Our new strategy is relying on the development of solid hybrid nanoparticles based on rare-earth such as gadolinium. In this paper, we then evidenced that gadolinium-based particles can be designed to enter efficiently into the human glioblastoma cell line U87 in quantities that can be tuned by modifying the incubation conditions. These sub-5 nm particles consist in a core of gadolinium oxide, a shell of polysiloxane and are functionalized by diethylenetriaminepentaacetic acid (DTPA). Although photoelectric effect is maximal in the [10-100 keV] range, such particles were found to possess efficient in-vitro radiosensitizing properties at an energy of 660 keV by using the "single-cell gel electrophoresis comet assay," an assay that measures the number of DNA damage that occurs during irradiation. Even more interesting, the particles have been evidenced by MTT assays to be also efficient radiosensitizers at an energy of 6 MeV for doses comprised between 2 and 8 Gy. The properties of the gadolinium-based particles give promising opening to a particle-assisted radio-therapy by using irradiation systems already installed in the majority of hospitals.

Despite the strong rationale for combining cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) in patients with peritoneal carcinomatosis, thermotolerance and chemoresistance might result from heat shock protein overexpression.

The Genes such as carbonic anhydrase IX (CAIX), hypoxia inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) have been suggested as hypoxic biomarkers in cancer. Indeed, these endogenous biomarkers have been shown to have stronger prognostic value response after treatment by irradiation. However, inconsistent results suggest that factors other than oxygen influence their expression. This present study deciphers the level of expression of different radioresistance biomarkers in both normoxia and hypoxia conditions followed by irradiation of human ovarian tumor cell lines (uterine cervix squamous cell carcinoma (HeLa). HeLa cells were submitted to hypoxia (1% O 2 ) conditions in a Thermo Scientific Heracell i CO 2 incubator. The cells were subjected to two doses 4-10 Gy irradiation and re-incubate in their starting conditions for 4 hours, then fixed in 4% paraformaldehyde for 20 min. Protein expressions were assessed by immunocytochemistry staining and fluorescent images were captured by a Axio Imager Z1 fluorescence microscope with oil immersion lens at 63× magnification. In normoxia conditions there was no modification of the level of expression of the CAIX after irradiation. However, an increasing expression level of VEGF was noted. The level of expression of HIF-1 in normoxia was low compared to the other two proteins (CAIX and VEGF). Hypoxia conditions at 2% resulted in a low expression of CAIX and VEGF before and after irradiation at 10 Gy in HeLa cells. HIF-1 had a maximum expression level compared to CAIX and VEGF at 2% oxygen after irradiation in HeLa cells. As tumor hypoxia occurs in a deprived microenvironment, other environmental factors such as irradiation might interact with the effect of low oxygen concentration on gene expression. This study shows that irradiation of HeLa cells has a profound influence on the oxygen dependent induction of certain endogenous hypoxic markers as HIF-1, CAIX, and VEGF.