Bladder cancer is among the top ten most common cancer types in the world. Around 25% of all cases are muscle-invasive bladder cancer, for which the gold standard treatment in the absence of metastasis is the cystectomy. In recent years, trimodality treatment associating maximal transurethral resection and radiotherapy combined with concurrent chemotherapy is increasingly used as an organ-preserving alternative. However, the use of this treatment is still limited by the lack of biomarkers predicting tumour response and by a lack of targeted radiosensitising drugs that can improve the therapeutic index, especially by limiting side effects such as bladder fibrosis. In order to improve the bladder-preserving treatment, experimental studies addressing these main issues ought to be considered (both in vitro and in vivo studies). Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews, we conducted a literature search in PubMed on experimental studies investigating how to improve bladder cancer radiotherapy with different radiosensitising agents using a comprehensive search string. We made comments on experimental model selection, experimental design and results, formulating the gaps of knowledge still existing: such as the lack of reliable predictive biomarkers of tumour response to chemoradiation according to the molecular tumour subtype and lack of efficient radiosensitising agents specifically targeting bladder tumour cells. We provided guidance to improve forthcoming studies, such as taking into account molecular characteristics of the preclinical models and highlighted the value of using patient-derived xenografts as well as syngeneic models. Finally, this review could be a useful tool to set up new radiation-based combined treatments with an improved therapeutic index that is needed for bladder preservation.

Side effects of proton therapy are poorly studied. Moreover, the differences in the method of dose delivery on normal tissues are not taken into account when proton beams are scanned instead of being scattered. We proposed here to study the effects of both modalities of proton beam delivery on blood; skin; lung and heart in a murine model. In that purpose; C57BL/6 mice were total body irradiated by 190.6 MeV proton beams either by Double Scattering (DS) or by Pencil Beam Scanning (PBS) in the plateau phase before the Bragg Peak. Mouse survival was evaluated. Blood and organs were removed three months after irradiation. Biomarkers of genotoxicity; oxidative stress and inflammation were measured. Proton irradiation was shown to increase lymphocyte micronucleus frequency; lung superoxide dismutase activity; erythrocyte and skin glutathione peroxidase activity; erythrocyte catalase activity; lung; heart and skin oxidized glutathione level; erythrocyte and lung lipid peroxidation and erythrocyte protein carbonylation even 3 months post-irradiation. When comparing both methods of proton beam delivery; mouse survival was not different. However, PBS significantly increased lymphocyte micronucleus frequency; erythrocyte glutathione peroxidase activity and heart oxidized glutathione level compared to DS. These results point out the necessity to take into account the way of delivering dose in PT as it could influence late side effects.

Bladder cancer is a common cancer; it is the tenth most common cancer in the world. Around one fourth of all diagnosed patients have muscle-invasive bladder cancer (MIBC), characterized by advanced tumors and which remains a lethal disease. The standard treatment for MIBC is the bladder removal by surgery. However, bladder-preserving alternatives are emerging by combining chemotherapy, radiotherapy and minimal surgery, aiming to increase the patient’s quality of life. The aim of the study was to improve these treatments by investigating a novel approach where in addition to radiotherapy, a receptor, TYRO3, a member of TAM receptor tyrosine kinase family known to be highly expressed on the bladder cancer cells and involved in the control of cell survival is targeted. For this, we evaluated the influence of TYRO3 expression levels on a colony or cell survival assays, DNA damage, γH2AX foci formation, gene expression profiling and cell cycle regulation, after radiation on different bladder cell models. We found that TYRO3 expression impacts the radiation response via the cell cycle dysregulation with noeffets on the DNA repair. Therefore, targeting TYRO3 is a promising sensitization marker that could be clinically employed in future treatments.

Proton therapy (PT), first delivered passively using the Double Scattering (DS) technique, has shifted to active delivery through the Pencil Beam technique

Olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor with established radiosensitizing properties, is a candidate for combination with radiotherapy, yet its multi-organ oxidative toxicity when combined with photon versus proton irradiation has not been characterized. In the ToxIP3 project, C57BL/6 male mice were allocated to six groups (n = 10 per group) receiving whole-body irradiation at 7.5 Gy by photons (TrueBeam™) or protons (190.6 MeV, Institut Curie, Orsay), with or without concurrent oral olaparib (50 mg/kg/day). Seventy-four biomarkers spanning protein carbonylation, lipid peroxidation, antioxidant enzyme activities, glutathione redox status, PARP activity, total protein, TGF-β1, and 13 plasma cytokines were quantified across nine compartments. The principal comparison (protons + olaparib vs. photons + olaparib) used two-sided Wilcoxon–Mann–Whitney tests with Benjamini–Hochberg false discovery rate (FDR) correction; time-shifted comparisons used rank-based ANCOVA adjusted for the day of sacrifice. Combination arms showed markedly increased lethality (median survival 9 days for photons + olaparib and 8 days for protons + olaparib in all 60 randomized animals); 54 mice were available for biomarker analysis. Of 74 biomarkers, 18 differed between combination arms after FDR correction; seven hepatic protein-normalized measurements were considered non-interpretable, leaving 11. Protons + olaparib was associated with higher intestinal GPx and GSH/GSSG, higher erythrocyte GSH, GSSG and SOD, higher cerebral SOD (+75.1%, q = 0.010), and a higher hepatic GSH/GSSG ratio (+108.2%, q < 0.001), whereas skin showed a lower GSH/GSSG ratio (−77.6%) and higher protein carbonylation (+142.9%). These exploratory findings, obtained in a near-lethal whole-body irradiation model, show modality-associated differences in redox biomarkers but do not establish differences in normal-tissue toxicity.